METHODS FOR CONTROLLED PROLIFERATION OF STEM CELLS / GENERATING INNER EAR HAIR CELLS USING GSK-3- ALPHA INHIBITORS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Application No. 62/302,803, filed March 2, 2016; and U.S. Application No. 62/303,099, filed March 3, 2016, each of which is incorporated by reference in its entirety.

BACKGROUND

Technical Field

[0002] The present disclosure relates to compositions and methods for inducing the self- renewal of stem/progenitor supporting cells, including inducing the stem/progenitor cells to proliferate while maintaining in the daughter cells the capacity to differentiate into tissue cells.

Description of the Related Art

[0003] Stem cells exhibit an extraordinary ability to generate multiple cell types in the body. Besides embryonic stem cells, tissue specific stem cells serve a critical role during development as well as in homeostasis and injury repair in the adult. Stem cells renew themselves through proliferation as well as generate tissue specific cell types through differentiation. The characteristics of different stem cells varies from tissue to tissue, and are determined by their intrinsic genetic and epigenetic status. However, the balance between self-renewal and differentiation of different stem cells are all stringently controlled.

Uncontrolled self-renewal may lead to overgrowth of stem cells and possibly tumor formation, while uncontrolled differentiation may exhaust the stem cell pool, leading to an impaired ability to sustain tissue homeostasis. Thus, stem cells continuously sense their environment and appropriately respond with proliferation, differentiation or apoptosis. It would be desirable to drive regeneration by controlling the timing and extent of stem cell proliferation and differentiation. Controlling the proliferation with small molecules that are cleared over time would allow for control of the timing and extent of stem cell proliferation and differentiation. Remarkably, tissue stem cells from different tissues share a limited number of signaling pathways for the regulation of their self-renewal and differentiation, albeit in a very context dependent manner. Some of these pathways are the Wnt and GSK3- beta pathways. [0004] Lgr5 is expressed across a diverse range of tissues and has been identified as a biomarker of adult stem cells in a variety of tissues such as the gut epithelia (Barker et al. 2007), kidney, hair follicle, and stomach (Barker et al, 2010; Haegebarth & Clevers, 2009). For example, it was first published in 2011, that mammalian inner ear hair cells are derived from LGR5 ⁺ cells (Chai et al, 2011, Shi et al. 2012). Lgr5 is a known component of the Wnt/beta-catenin pathway, which has been shown to play major roles in differentiation, proliferation, and inducing stem cell characteristics (Barker et al. 2007).

[0005] Permanent damage to the hair cells of the inner ear results in sensorineural hearing loss, leading to communication difficulties in a large percentage of the population. Hair cells are the receptor cells that transduce the acoustic stimulus. Regeneration of damaged hair cells would provide an avenue for the treatment of a condition that currently has no therapies other than prosthetic devices. Although hair cells do not regenerate in the mammalian cochlea, new hair cells in lower vertebrates are generated from epithelial cells, called supporting cells, which surround hair cells.

[0006] Prior work has focused on transdifferentiation of supporting cells into hair cells through activation or forced expression of genes that lead to hair cell formation, with a particular focus on mechanisms to enhance expression of Atohl (Bermingham et al, 1999; Zheng and Gao, 2000; Izumikawa et al, 2005; Mizutari et al, 2013). Interestingly, cells transduced with Atohl vectors have been shown to acquire vestibular phenotypes (Kawamoto et al, 2003; Huang et al, 2009; Yang et al, 2012, 2013), and lack complete development. As mentioned, upregulating Atohl via gene insertion has been shown to create non-cochlear cell types that behave in a manner that is not found within the native cochlea. In addition, these methods increase hair cell numbers but decrease supporting cell numbers. Since supporting cells are known to have specialized roles (Ramirez-Camancho 2006, Dale and Jagger 2010), loss of these cells could create problems in proper cochlear function.

[0007] Thus, there remains a long felt need to protect auditory cells before injury, preserve/promote the function of existing cells after injury, regenerate structure including neurons and hair cells after injury, and regenerate cochlear supporting cells or hair cells after injury. As disclosed below, in certain embodiments, the present disclosure provides methods for preventing and treating auditory dysfunctions.

BRIEF DESCRIPTION OF THE DRAWINGS [0008] Figures 1A-1B show expansion of Lgr5-GFP inner ear supporting cells in multiple conditions. Figure 1A shows Brightfield and GFP fluorescence images of Lgr5-GFP inner ear progenitor cells cultured for 10 days in media containing Growth Factor (GF) = [EGF, bFGF, IGF-1], VPA (V), combined with either CHIR99021 (C), a molecule that preferentially inhibits GSK3 , or AZD1080, a molecule that preferentially inhibits GSK3a. Figure IB shows quantification of Lgr5-GFP inner ear progenitor cells cultured for 10 days in media containing GF=[EGF, bFGF, IGF-1], VPA (V), combined with either CHIR99021 (C), a molecule that preferentially inhibits GSK3 , or AZD1080, a molecule that preferentially inhibits GSK3a.

[0009] Figures 2A-2B show Expansion of Lgr5-GFP inner ear supporting cells in multiple conditions. Figure 2B shows brightfield and GFP fluorescence images of Lgr5-GFP inner ear progenitor cells cultured for 10 days in media containing GF=[EGF, bFGF, IGF-1], VPA (V), combined with either CHIR99021 (C), a molecule that preferentially inhibits GSK3 , or GSK3 inhibitor XXII, a molecule that equally inhibits GSK3a and GSK3 . Figure 2B shows quantification of Lgr5-GFP inner ear progenitor cells cultured for 10 days in media containing GF = [EGF, bFGF, IGF-1], VPA (V), combined with either CHIR99021 (C), a molecule that preferentially inhibits GSK3 , or GSK3 inhibitor XXII, which has a higher GSK3a-inhibition preference than CHIR99021.

[0010] Figure 3 shows increased number of hair cells in organ of Corti treated ex vivo. Organ of Corti treated with GSK3 -inhibitor XXII showed increased Lgr5-GFP expression, 2 rows of inner hair cells, and 6 rows of outer hair cells. This is an increase over the normal 1 row of inner hair cells and 3 rows of outer hair cells normally seen in the cochlea.

[0011] Figure 4 shows hearing recovery in noise damaged CBA/CaJ mice. Animals treated with Valproic Acid and CHIR99021 (CV), where CHIR99021 preferentially inhibits GSK3 compared to GSKa, showed significant recovery across all tested frequencies (n=32).

Animals treated with VPA (V) and GSK3-inhibitor XXII (a molecule that has a higher GSK3a-inhibition preference than CHIR99021 (n=6)).

BRIEF SUMMARY

[0012] In one aspect the present disclosure provides a method for proliferation of stem cells comprising contacting a cell population with an effective amount of a GSK3-alpha inhibitor, or a pharmaceutically-acceptable salt thereof. In some embodiments, the method further comprises contacting the cell population with a differentiation inhibitor, e.g., an HDAC inhibitor or a Notch agonist. In certain embodiments, the differentiation inhibitor is valproic acid.

[0013] Among the various aspects of the present disclosure, therefore, may be noted a method for activating the Wnt pathway in a cell population to increase the capacity of the population for self-renewal, i.e., the capacity for repeated generation of daughter cells with equivalent proliferation and 'cell fate specification' potential, and differentiation, i.e. , the capacity for generation of daughter cells specified for differentiation. In one embodiment, the cell population is a cochlear supporting cell population. Preferably, the Wnt pathway is activated upstream of the c-myc gene in members of the population and without any genetic modification of the population. Instead, the Wnt pathway is preferably activated by small molecules that transiently induce such activity. Additionally, the supporting cell population preferably includes supporting cells that are LGR5 ⁺ and endogenous to the Organ of Corti.

[0014] A further aspect of the present disclosure is a method for inducing the self-renewal of stem/progenitor supporting cells comprised by a cochlear cell population. That is, the stem/progenitor supporting cells are induced to proliferate {i.e., divide and form daughter cells) while maintaining, in the daughter cells, the capacity to differentiate into hair cells. In contrast, if the stem/progenitor supporting cells were merely induced to proliferate (without maintaining multi-potency), the daughter cells would lack the capacity to divide into hair cells. Further, merely enforcing differentiation of a pre-existing stem/progenitor cell population has the potential to exhaust the stem cell pool.

[0015] Proliferation is preferably activated by small molecules that transiently induce such activity. Additionally, in certain embodiments the supporting cell population preferably includes supporting cells that are LGR5 ⁺ and endogenous to the Organ of Corti.

[0016] In various embodiments, the Wnt pathway is activated with a GSK3-alpha inhibitor. In some embodiments, the Wnt pathway is activated with a plurality of GSK3-alpha inhibitors. In some embodiments, the GSK3-alpha inhibitor used according to the methods herein includes one or more of the GSK3 -alpha inhibitors disclosed herein. In one embodiment, the one or more GSK3-alpha inhibitor is one or more of the GSK3-alpha inhibitors in Table 1.

[0017] In certain embodiments, therefore, the present disclosure provides methods to induce self-renewal of a population of supporting cells by activating pathways and mechanisms (e.g., the Wnt pathway) that are involved in inducing stem cell properties to create "induced pluripotent stem cells", e.g., via contacting the cells with a GSK3-alpha inhibitor. Preferably, the pathways are activated with small molecules (e.g., any one or more of the GSK3-alpha inhibitors in Table 1). For example, a composition when applied in vitro to a supporting cell population induces the population to proliferate to a high degree and in high purity in a Stem Cell Proliferation Assay, and also allows the population to differentiate into a high purity population of a tissue cell in a Stem Cell Differentiation Assay. In one such embodiment, the composition induces and maintains stem cell properties by proliferating to produce stem cells that can divide for many generations and maintain the ability to have a high proportion of the resulting cells differentiate into tissue cells. Further, the proliferating stem cells express stem cell markers which may include one or more of Lgr5, Sox2, Opeml, Phex, lin28, Lgr6, cyclin Dl, Msxl, Myb, Kit, Gdnf3, Zic3, Dppa3, Dppa4, Dppa5, Nanog, Esrrb, Rexl, Dnmt3a, Dnmt3b, Dnmt31, Utfl, Tell, Oct4, Klf4, Pax6, Six2, Zicl, Zic2, Otx2, Bmil, CDX2, STAT3, Smadl, Smad2, smad2/3, smad4, smad5, and smad7.

[0018] In certain embodiments, the disclosure provides a method for expanding a population of cochlear cells in a cochlear tissue comprising a parent population of cells, the method comprising contacting the cochlear tissue with a stem cell proliferator to form an expanded population of cells in the cochlear tissue, wherein

the stem cell proliferator is capable of (i) forming a proliferation assay final cell population from a proliferation assay initial cell population over a proliferation assay time period in a stem cell proliferation assay and (ii) forming a differentiation assay final cell population from a differentiation assay initial cell population over a differentiation assay time period in a stem cell differentiation assay wherein:

(a) the proliferation assay initial cell population has (i) a proliferation assay initial number of total cells, (ii) a proliferation assay initial number of Lgr5 ⁺ cells, (iii) a proliferation assay initial number of hair cells, (iv) a proliferation assay initial Lgr5 ⁺ cell fraction that equals the ratio of the proliferation assay initial number of Lgr5 ⁺ cells to the proliferation assay initial number of total cells, and (v) a proliferation assay initial hair cell fraction that equals the ratio of the proliferation assay initial number of hair cells to the proliferation assay initial number of total cells;

(b) the proliferation assay final cell population has (i) a proliferation assay final number of total cells, (ii) a proliferation assay final number of Lgr5 ⁺ cells, (iii) a proliferation assay final number of hair cells, (iv) a proliferation assay final Lgr5 ⁺ cell fraction that equals the ratio of the proliferation assay final number of Lgr5 ⁺ cells to the proliferation assay final number of total cells and (v) a proliferation assay final hair cell fraction that equals the ratio of the proliferation assay final number of hair cells to the proliferation assay final number of total cells;

(c) the differentiation assay initial cell population has (i) a differentiation assay initial number of total cells, (ii) a differentiation assay initial number of Lgr5 ⁺ cells, (iii) a differentiation assay initial number of hair cells, (iv) a differentiation assay initial Lgr5 ⁺ cell fraction that equals the ratio of the differentiation assay initial number of Lgr5 ⁺ cells to the differentiation assay initial number of total cells, and (v) a differentiation assay initial hair cell fraction that equals the ratio of the differentiation assay initial number of hair cells to the differentiation assay initial number of total cells;

(d) the differentiation assay final cell population has (i) a differentiation assay final number of total cells, (ii) a differentiation assay final number of Lgr5 ⁺ cells, (iii) a differentiation assay final number of hair cells, (iv) a differentiation assay final Lgr5 ⁺ cell fraction that equals the ratio of the differentiation assay final number of Lgr5 ⁺ cells to the differentiation assay final number of total cells, and (v) a differentiation assay final hair cell fraction that equals the ratio of the differentiation assay final number of hair cells to the differentiation assay final number of total cells;

(e) the proliferation assay final number of Lgr5 ⁺ cells exceeds the proliferation assay initial number of Lgr5 ⁺ cells by a factor of at least 10; and

(f) the differentiation assay final number of hair cells is a non-zero number.

In certain such embodiments, the stem cell proliferator comprises Sternness Driver (e.g., a GSK3-alpha inhibitor). In certain embodiments, the stem cell proliferator comprises a Differentiation Inhibitor. In certain embodiments, the stem cell proliferator comprises a Sternness Driver and a Differentiation Inhibitor. In certain embodiments, the stem cell proliferator is a GSK3 -alpha inhibitor (e.g., a GSK3 -alpha inhibitor shown in Table 1) and the method further comprises contacting cochlear cells in the cochlear tissue with a differentiation inhibitor. In some embodiments, the differentiation inhibitor is an HDAC inhibitor or a Notch agonist. In some embodiments, the differentiation inhibitor is valproic acid. [0019] In certain embodiments, the disclosure provides a method for increasing the cell density of supporting cells in a population of cochlear cells, the method comprising activating pathways and mechanisms that induce stem cell properties in the supporting cells, proliferating the activated supporting cells (while maintaining the multi-potent character of the supporting cells in the newly formed daughter cells) and thereafter allowing (or even inducing) the expanded population to differentiate into hair cells to form an expanded cochlear cell population wherein the cell density of hair cells in the expanded cochlear cell population exceeds the cell density of hair cells in the original (non-expanded) cochlear cell population. In some embodiments, the supporting cell population is an in vitro supporting cell population. In some embodiments, the supporting cell population is an in vivo supporting cell population. Additionally, the proliferation stage is preferably controlled to substantially maintain the native organization of the cochlear structure. In such embodiments, the proliferating is induced by one or more GSK3-alpha inhibitors (e.g., one or more of the GSK- alpha inhibitors shown in Table 1) that transiently induce such activity, rather than by induction of c-myc and without any genetic modification of the population. In some embodiments, such methods further comprise contacting the cells with a differentiation inhibitor. In some embodiments, the differentiation inhibitor is an HDAC inhibitor or a Notch agonist. In some embodiments, the differentiation inhibitor is valproic acid.

Additionally, in certain embodiments the supporting cell population preferably includes supporting cells that are LGR5 ⁺ and endogenous to the Organ of Corti.

[0020] In certain embodiments, the disclosure provides a method for increasing the cell density of Lgr5 ⁺ supporting cells in a population of cochlear cells, the method comprising activating pathways and mechanisms that induce or maintain stem cell properties in the Lgr5 ⁺ supporting cells, proliferating the activated Lgr5 ⁺ supporting cells (while maintaining such stem cell properties) and thereafter allowing (or even inducing) the expanded population to differentiate into hair cells to form an expanded cochlear cell population wherein the cell density of hair cells in the expanded cochlear cell population exceeds the cell density of hair cells in the original (non-expanded) cochlear cell population. In some embodiments, the Lgr5 ⁺ supporting cell population is an in vitro Lgr5 ⁺ stem cell population. In some embodiments, the Lgr5 ⁺ supporting cell population is an in vivo supporting cell population. Additionally, in certain embodiments the proliferation stage is preferably controlled to substantially maintain the native organization of the cochlear structure. In such

embodiments, the proliferating is induced by one or more GSK3-alpha inhibitors (e.g., one or more of the GSK-alpha inhibitors shown in Table 1). In some embodiments, the GSK3-alpha inhibitors transiently induce such activity, rather than by induction of c-myc and without any genetic modification of the population. In some embodiments, such methods further comprise contacting the cells with a differentiation inhibitor. In some embodiments the differentiation inhibitor is an HDAC inhibitor or a Notch agonist. In some embodiments, the differentiation inhibitor is valproic acid.

[0029] In certain embodiments, a composition containing a Sternness Driver (e.g., a GSK- alpha inhibitor) and a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor such as valproic acid) is administered to a cochlear cell population to induce proliferation of stem cells and to inhibit differentiation of the stem cells until the desired expansion of the stem cell population is achieved. Thereafter, the expanded population is permitted (or optionally even induced) to differentiate into hair cells. Additionally, the proliferation stage is preferably controlled to substantially maintain the native organization of the cochlear structure. In some embodiments, the Sternness Driver and Differentiation inhibitor are small molecules. In some embodiments, the stem cell population is an in vivo stem cell population. In some embodiments, the stem cell population is an in vitro stem cell population. In some embodiments, the stem cell population is an in vivo Lgr5 ⁺ stem cell population. In some embodiments, the stem cell population is an in vitro Lgr5 ⁺ stem cell population. In some embodiments, the Sternness Driver is a GSK-alpha inhibitor. In some embodiments, the differentiation inhibitor is an HDAC inhibitor or a Notch agonist. In some embodiments, the differentiation inhibitor is valproic acid.

[0030] In certain embodiments, the disclosure provides a method for increasing the cell density of hair cells in an initial population of cochlear cells, the initial population (which may be an in vivo or an in vitro population) comprises hair cells, Lgr ^" supporting cells, and Lgr5 ⁺ supporting cells. The method comprises administering to the initial population a Sternness Driver and Differentiation inhibitor. In some embodiments, the Sternness Driver is a GSK-alpha inhibitor. In some embodiments, the differentiation inhibitor is an HDAC inhibitor or a Notch agonist. In some embodiments, the differentiation inhibitor is valproic acid.

[0021] In certain embodiments, the method produces stem cells in a Stem Cell Proliferation Assay that express stem cells markers Lgr5 ⁺ . In certain embodiments, if a mixed population of Lgr5 ⁺ and non-Lgr5 ⁺ stems are placed in a Stem Cell Proliferation Assay, the method increases the fraction of cells in the population that are Lgr5 ⁺ . [0031] Expanding supporting cell populations to a degree that destroys the native

organization of the cochlear structure could inhibit cochlear function. Driving proliferation of existing supporting cells with a small molecule signal may allow for a more controlled regeneration of hair cells than using gene delivery, which is incapable of targeting a specific cell type and permanently alters a cell's genetic information. An approximately normal cochlear structure is desired with rows of hair cells that have supporting cells between them, and hair cells do not contact other hair cells. Further, it would be desirable to avoid using genetic modification to drive proliferation to create large cell aggregations in the cochlea that disrupt the organ's anatomy.

[0022] In certain embodiments, the disclosure provides a composition comprising a Sternness Driver that may be used to drive the selective expansion of cochlea supporting cells. In some cases, a Sternness Driver may also induce differentiation of the supporting cells to hair cells if a Differentiation Inhibitor is not present at an Effective Differentiation Inhibition

Concentration. Examples of Sternness Drivers that may drive both proliferation and differentiation include GSK3-alpha inhibitors. In certain of these embodiments, the composition comprises a Sternness Driver and a Differentiation Inhibitor, where in the Sternness Driver and the Differentiation Inhibitor are different agents. In one such embodiment, the Sternness Driver is a GSK3-alpha inhibitor (e.g., one of the GSK3-alpha inhibitors disclosed herein) and the Differentiation Inhibitor is valproic acid.

[0023] In certain embodiments, the disclosure provides a method for increasing the cell density of hair cells in an initial population of cochlear cells comprising hair cells and supporting cells. The method comprises selectively expanding the number of supporting cells in the initial population to form an intermediate cochlear cell population wherein the ratio of the number of supporting cells to hair cells in the intermediate cochlear cell population exceeds the ratio of the number of supporting cells to hair cells in the initial cochlear cell population. The method further comprises generating hair cells in the intermediate cochlear cell population to form an expanded cochlear cell population wherein the ratio of the number of hair cells to supporting cells in the expanded cochlear cell population exceeds the ratio of the number of hair cells to supporting cells in the intermediate cochlear cell population.

[0024] In certain embodiments, the disclosure provides a method for increasing the number of Lgr5 ⁺ supporting cells or increasing the Lgr5 ⁺ activity in an initial population of cochlear cells, wherein the initial population comprises supporting cells and hair cells. For example, in one such method an intermediate population is formed in which the number of Lgr5 ⁺ supporting cells is expanded relative to the initial population. Alternatively, in one such method an intermediate population is formed in which the Lgr5 ⁺ activity of the supporting cells relative to the initial population is increased. Alternatively, a method where the number of Lgr5 ⁺ cells is increased relative to the initial cell population by activating Lgr5 ⁺ expression in cell types that normally lack or have very low levels of Lgr5 ⁺ . By way of further example, an intermediate population is formed in which the number of Lgr5 ⁺ supporting cells is expanded and the Lgr5 activity is increased relative to the initial cochlear cell population. Thereafter, hair cells in the intermediate cochlear cell population may be generated to form an expanded cochlear cell population wherein the ratio of hair cells to supporting cells in the expanded cochlear cell population exceeds the ratio of the number of hair cells to supporting cells in the intermediate cochlear cell population.

[0025] In some embodiments, the methods of the present disclosure comprise a first

Proliferation Period with an Effective Sternness Driver Concentration and an Effective Differentiation Inhibition Concentration of a Differentiation Inhibitor, followed by a

Differentiation Period with an Effective Sternness Driver Concentration and without an Effective Differentiation Inhibition Concentration of a Differentiation Inhibitor. In some such embodiments, the Sternness Driver and Differentiation Inhibitor are provided to the cochlear cells in a formulation that releases the Sternness Driver and Differentiation inhibitor at different rates. In some such embodiments, the Sternness Driver is a GSK3-alpha inhibitor (e.g., one or more of the GSK3-alpha inhibitors disclosed in Table 1). In some such embodiments, the Sternness Driver is a GSK3-alpha inhibitor (e.g., one or more of the GSK3- alpha inhibitors disclosed in Table 1) and the Differentiation Inhibitor is an HDAC inhibitor or a Notch agonist. In some such embodiments, the Sternness Driver is a GSK3-alpha inhibitor (e.g., one or more of the GSK3-alpha inhibitors disclosed in Table 1) and the Differentiation Inhibitor is valproic acid.

[0032] In certain embodiments, the disclosure provides a method of and compositions for generating hair cells, the method comprising: administering or causing to be administered to a stem cell population (e.g., of an in vitro, ex vivo, or in vivo sample/subject) a composition comprising both of (i) and (ii): (i) a GSK3-alpha inhibitor (or a derivative or

pharmaceutically-acceptable salt thereof) and (ii) valproic acid (or a derivative or analog or pharmaceutically-acceptable salt thereof), thereby proliferating stem cells in the stem cell population and resulting in an expanded population of stem cells; and exposing the expanded population of stem cells to a GSK3-alpha inhibitor (or a derivative or pharmaceutically- acceptable salt thereof) and, optionally a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor, e.g., valproic acid), thereby facilitating generation of inner ear hair cells from the expanded population of stem cells.

[0026] In certain embodiments, the disclosure provides methods for preventing and treating auditory dysfunction. For example, in certain embodiments, the disclosure provides methods for preventing or treating auditory impairments in a subject comprising administering to said subject an effective amount of a GSK3-alpha inhibitor (e.g., any one or more of the GSK3- alpha inhibitors disclosed in Table 1)

[0027] In certain embodiments, the present disclosure also relates to ex-vivo uses of cells described herein. For example, approaches described herein can be used for hi and for discovery purposes. For example, certain embodiments of the present disclosure are useful for identifying agents that proliferate hair cell progenitors and/or increase numbers of hair cells, and also agents that protect supporting cells and/or hair cells (e.g. to support their survival), and also for identifying agents that are toxic or not toxic to supporting cells or differentiated progeny including hair cells.

[0028] In certain embodiments, the disclosure provides for methods for inhibiting the loss or death of the cells of the auditory system in a subject comprising administering to said subject an effective amount of a composition described herein (e.g., comprising a GSK3-alpha inhibitor and optionally a differentiation inhibitor (e.g., a Notch agonist or an HDAC inhibitor, e.g., valproic acid) or derivative thereof or pharmaceutically-acceptable salt thereof and an acceptable carrier or excipient, thereby inhibiting loss or death of the cells of the auditory system in the subject or regenerating structure including hair cells and/or neurons.

[0029] In certain embodiments, the disclosure provides methods for maintaining or promoting the growth of cells of the auditory system in a subject comprising administering to said subject a composition comprising as an agent described herein (comprising a GSK3- alpha inhibitor and optionally a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor, e.g., valproic acid) or derivative thereof or pharmaceutically-acceptable salt thereof in an effective amount so as to augment or initiate endogenous repair, thereby maintaining or promoting the growth of cells of the auditory system in the subject.

[0033] Also described herein is a method for expanding a population of cochlear cells in a cochlear tissue comprising a parent population of cells, the parent population including supporting cells and a number of Lgr5 ⁺ cells, the method comprising contacting the cochlear tissue with a stem cell proliferator to form an expanded population of cells in the cochlear tissue, wherein the stem cell proliferator is capable (i) in a stem cell proliferation assay of increasing the number of Lgr5 ⁺ cells in a stem cell proliferation assay cell population by a factor of at least 10 and (ii) in a stem cell differentiation assay of forming hair cells from a cell population comprising Lgr5 ⁺ cells.

[0034] Also described herein is a method for expanding a population of cochlear cells in a cochlear tissue comprising a parent population of cells, the parent population including supporting cells, the method comprising contacting the cochlear tissue with a stem cell proliferator to form an expanded population of cells in the cochlear tissue. The stem cell proliferator can be capable of (i) forming a proliferation assay final cell population from a proliferation assay initial cell population over a proliferation assay time period in a stem cell proliferation assay and (ii) forming a differentiation assay final cell population from a differentiation assay initial cell population over a differentiation assay time period in a stem cell differentiation assay wherein: (a) the proliferation assay initial cell population has (i) a proliferation assay initial number of total cells, (ii) a proliferation assay initial number of Lgr5 ⁺ cells, (iii) a proliferation assay initial number of hair cells, (iv) a proliferation assay initial Lgr5 ⁺ cell fraction that equals the ratio of the proliferation assay initial number of Lgr5 ⁺ cells to the proliferation assay initial number of total cells, and (v) a proliferation assay initial hair cell fraction that equals the ratio of the proliferation assay initial number of hair cells to the proliferation assay initial number of total cells; (b) the proliferation assay final cell population has (i) a proliferation assay final number of total cells, (ii) a proliferation assay final number of Lgr5 ⁺ cells, (iii) a proliferation assay final number of hair cells, (iv) a proliferation assay final Lgr5 ⁺ cell fraction that equals the ratio of the proliferation assay final number of Lgr5 ⁺ cells to the proliferation assay final number of total cells and (v) a proliferation assay final hair cell fraction that equals the ratio of the proliferation assay final number of hair cells to the proliferation assay final number of total cells; (c) the

differentiation assay initial cell population has (i) a differentiation assay initial number of total cells, (ii) a differentiation assay initial number of Lgr5 ⁺ cells, (iii) a differentiation assay initial number of hair cells, (iv) a differentiation assay initial Lgr5 ⁺ cell fraction that equals the ratio of the differentiation assay initial number of Lgr5 ⁺ cells to the differentiation assay initial number of total cells, and (v) a differentiation assay initial hair cell fraction that equals the ratio of the differentiation assay initial number of hair cells to the differentiation assay initial number of total cells; (d) the differentiation assay final cell population has (i) a differentiation assay final number of total cells, (ii) a differentiation assay final number of Lgr5 ⁺ cells, (iii) a differentiation assay final number of hair cells, (iv) a differentiation assay final Lgr5 ⁺ cell fraction that equals the ratio of the differentiation assay final number of Lgr5 ⁺ cells to the differentiation assay final number of total cells, and (v) a differentiation assay final hair cell fraction that equals the ratio of the differentiation assay final number of hair cells to the differentiation assay final number of total cells; (e) the proliferation assay final number of Lgr5 ⁺ cells exceeds the proliferation assay initial number of Lgr5 ⁺ cells by a factor of at least 10; and (f) the differentiation assay final number of hair cells is a non-zero number.

[0035] The proliferation assay final number of Lgr5 ⁺ cells can be greater than the proliferation assay initial number of Lgr5 ⁺ cells by a factor of at least 50, or by a factor of at least 100. The expanded population of cells in the cochlear tissue can include a greater number of hair cells than does the parent population. The proliferation assay final Lgr5 ⁺ cell fraction can be greater than the differentiation assay initial Lgr5 ⁺ cell fraction by at least a factor of 2. The differentiation assay final hair cell fraction can be greater than the proliferation assay initial hair cell fraction by at least a factor of 2. The proliferation assay final hair cell fraction can be at least 25% less than the proliferation assay initial hair cell fraction. The proliferation assay final Lgr5 ⁺ cell fraction can be at least 10% greater than proliferation assay initial Lgr5 ⁺ cell fraction. One of more morphological characteristics of the cochlear tissue can be maintained. Native morphology can be maintained. The stem cell proliferator can be dispersed in a biocompatible matrix, which can be a biocompatible gel or foam. The cochlear tissue can be an in vivo cochlear tissue or an ex vivo cochlear tissue. The method can produce a population of Lgr5 ⁺ cells that are in s-phase. The at least one stem cell proliferator can include both a sternness driver and a differentiation inhibitor. For example, in some embodiments, the stem cell proliferator includes a sternness driver that is a GSK3-alpha inhibitor and a differentiation inhibitor. In some embodiments, the stem cell proliferator includes a sternness driver that is a GSK3-alpha inhibitor and a differentiation inhibitor that is an HDAC inhibitor or a Notch agonist. In some embodiments, the stem cell proliferator includes a sternness driver that is a GSK3-alpha inhibitor and a differentiation inhibitor that is valproic acid. Contacting can provide to the cochlear tissue: in an initial phase, at least an effective proliferation concentration of the sternness driver and at least an effective differentiation inhibition concentration of the differentiation inhibitor; and in a subsequent phase, at least an effective proliferation concentration of the sternness driver and less than an effective differentiation inhibition concentration of the differentiation inhibitor. The cochlear tissue can be in a subject, and contacting the cochlear tissue with the composition can be achieved by administering the composition transtympanically to the subject. Contacting the cochlear tissue with the composition can result in improved auditory functioning of the subject.

[0036] Also described herein is a method of treating a subject who has, or is at risk of developing, hearing loss. The method can include transtympanically administering to a cochlear tissue of the subject a GSK3-alpha inhibitor. In some such embodiments, the method further comprises administering a differentiation inhibitor to the tissue. In one such embodiment, the differentiation inhibitor is an HDAC inhibitor or a Notch agonist. In one such embodiment, the differentiation inhibitor is valproic acid.

[0037] Certain embodiments relate to pharmaceutical compositions, comprising a pharmaceutically-acceptable carrier and a stem cell proliferator that is a GSK3-alpha inhibitor, or a pharmaceutically-acceptable salt thereof. In some embodiments, the composition is adapted for administration to the inner ear and/or middle ear. In some instances, the composition is adapted for local administration to the round window membrane. In some embodiments, the composition is adapted for intratympanic or transtympanic administration, for example, to cochlear tissue.

[0038] In some embodiments, the GSK3-alpha inhibitor is dispersed in a biocompatible matrix. In certain embodiments, the biocompatible matrix is a biocompatible gel or foam.

[0039] Some compositions further comprise a differentiation inhibitor. In particular embodiments, the differentiation inhibitor is selected from an HDAC inhibitor and a Notch agonist, or a pharmaceutically-acceptable salt thereof. In some embodiments, the HDAC inhibitor is valproic acid, or a derivative or analog or pharmaceutically-acceptable salt thereof.

[0040] In some embodiments, the GSK3-alpha inhibitor has a GSK3-alpha/GSK3-beta selectivity ratio that is at least about 0.5x, or 0.6x, 0.7x, 0.8x, 0.9x, l .Ox, l . lx, 1.2x, or 1.3x, 1.4x, 1.5x, 2x, 3x, 4x, 5x, 6x, 7x, 8x, 9x, lOx, 15x, 20x, 25x, 30x, 40x, 50x, 60x, 70x, 80x, 90x, or lOOx. In some embodiments, the GSK3-alpha inhibitor has potency against both GSK3-alpha and GSK3-beta, wherein the potency is less than about 100 nM for inhibiting both GSK3-alpha and GSK3-beta, or less than about 50 nM, 20 nM, 10 nM, 5 nM, 2 nM, or less than about 1 nM for inhibiting both GSK3-alpha and GSK3-beta. In some embodiments, the GSK3-alpha inhibitor has a GSK3-alpha/CDK selectivity ratio that is at least about lOx or 15x, 20x, 25x, 30x, 35x, 40x, 45x, 50x, 60x, 60x, 80x, 90x, or at least about lOOx. In some embodiments, the GSK3-alpha inhibitor has a GSK3-alpha/MAPK selectivity ratio that is at least about lOx or 15x, 20x, 25x, 30x, 35x, 40x, 45x, 50x, 60x, 60x, 80x, 90x, or at least about lOOx. In some embodiments, the GSK3-alpha inhibitor has a GSK3-alpha/ERK selectivity ratio that is at least about l Ox or 15x, 20x, 25x, 30x, 35x, 40x, 45x, 50x, 60x, 60x, 80x, 90x, or at least about l OOx. In some embodiments, the GSK3-alpha inhibitor has a GSK3-alpha/MEK selectivity ratio that is at least about l Ox or 15x, 20x, 25x, 30x, 35x, 40x, 45x, 50x, 60x, 60x, 80x, 90x, or at least about l OOx. In some embodiments, the GSK3-alpha inhibitor comprises potency for GSK3-alpha that ranges from about InM to about ΙΟΟΟηΜ; from about 100 nM to about 1000 nM; from about 10 nM to about ΙΟΟηΜ; of from about InM to about 10 nM.

[0041] In some embodiments, the pharmaceutical composition comprises a poloxamer. In particular embodiments, the poloxamer comprises at least one of Poloxamer 188 and

Poloxamer 407 or mixtures thereof. In some embodiments, the poloxamer is in a

concentration between about 5 wt% and about 25 wt% relative to the composition. In particular embodiments, the poloxamer is in a concentration between about 10 wt% and about 23 wt% relative to the composition. In some embodiments, the poloxamer is in a

concentration between about 15 wt% and about 20 wt% relative to the composition. In specific embodiments, the poloxamer is in a concentration is approximately 17 wt% relative to the composition.

[0042] In some compositions, the GSK3-alpha inhibitor is at a concentration of about 0.01 uM to 1000 mM, about 0.1 uM to 1000 mM, about 1 uM to 100 mM, about 10 uM to 10 mM, about 1 uM to 10 uM, about 10 uM to 100 uM, about 100 uM to 1000 uM, about 1 mM to 10 mM, or about 10 mM to 100 mM; or at a concentration ratio of about 0.01 to 1 ,000,000 fold relative to its effective activity in an in vitro activity assay, or about 0.1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 5000 fold relative to its effective activity in an in vitro activity assay, or about 50 to 2000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay, or at about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 0.01 nM to 1000 uM, about 0.1 nM to 1000 uM, about 1 nM to 100 uM, about 10 nM to 10 uM, about 1 nM to 10 nM, about 10 nM to 100 nM, about 100 nM to 1000 nM, about 1 uM to 10 uM, or about 10 uM to 100 uM.

[0043] In some embodiments, the GSK3-alpha inhibitor is GSK3 inhibitor XXII, which is at a concentration of about 0.1 uM to 1000 mM, about 1 uM to 100 mM, 10 uM to 10 mM, about 100 uM to 10 mM, or 100 uM to 1 mM, or about 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10 mM; or at a concentration ratio of about 0.1 to 1 ,000,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 10 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay, or about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 0.1 nM to 1000 uM, about 1 nM to 100 uM, about 10 nM to 10 uM, about 100 nM to 1 uM, or about 0.5 uM.

[0044] In certain embodiments, the GSK3-alpha inhibitor is AZD1080, which is at a concentration of about 0.1 uM to 1000 mM, about 1 uM to 1000 mM, about 10 uM to 100 mM, about 100 uM to 10 mM, about 1 mM to 10 mM, or about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mM; or at a concentration ratio of about 0.1 to 1,000,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 10 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay, or about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 1 nM to 1000 uM, about 10 nM to 1000 uM, about 100 nM to 100 uM, about 1 uM to 10 uM, or about 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10 uM.

[0045] In some embodiments, the HDAC inhibitor is at a concentration of about 0.01 uM to 100,000 mM, about 1 uM to 10,000 mM, about 10 uM to 10,000 mM, about 100 uM to 1000 mM, about 1 uM to 10 uM, about 10 uM to 100 uM, about 100 uM to 1000 uM, about 1000 uM to 10 mM, about 10 mM to 100 mM, about 100 mM to 1000 mM, or about 1000 mM to 10,000 mM; or at a concentration ratio of about 0.1 to 1,000,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 10 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay; or about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 0.01 nM to 100,000 uM, about 1 nM to 10,000 uM, about 10 nM to 10,000 uM, about 100 nM to 1000 uM, about 1 nM to 10 nM, about 10 nM to 100 nM, about 100 nM to 1000 nM, about 1 uM to 10 uM, about 10 uM to 100 uM, about 100 uM to 1000 uM, or about 1000 uM to 10,000 uM.

[0046] In certain embodiments, the HDAC inhibitor is valproic acid, which is at a concentration of about 10 uM to 100,000 mM, about 1 mM to 10,000 mM, about 10 mM to 10,000 mM, about 100 mM to 10,000 mM, about 200 mM to 2000 mM, about 1000 mM, or about 600 mM; or at a concentration ratio of about 0.1 to 1,000,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 10 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay, or about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 10 nM to 100,000 uM, 1 uM to 10,000 uM, about 10 uM to 10,000 uM, about 100 uM to 10,000 uM, about 200 uM to 2000 uM, or about 1000 uM.

[0047] In certain embodiments, the effective activity is measured in an Lgr5 proliferation assay, as described herein.

[0048] In certain compositions, the GSK3-alpha inhibitor is capable in a stem cell proliferation assay of increasing the number of Lgr5 ⁺ cells in a stem cell proliferation assay cell population by a factor of at least about 1.25, 1.5, 1.75, 2, 3, 5, 10, or 20, and is optionally selected from Table 1. In some compositions, the a GSK3-alpha inhibitor is capable in a stem cell differentiation assay of forming hair cells from a cell population comprising Lgr5 ⁺ cells

[0049] The pharmaceutical compositions can be used in any one or more of the methods described herein, including the use of the compositions for expanding a population of cochlear cells in a cochlear tissue. The pharmaceutical compositions can also be used for treating a subject who has, or is at risk of developing, hearing loss.

[0050] Also included are methods of generating Myo7a+ cochlear cells. The methods can include contacting Lgr5+ cochlear cells with a GSK3 -alpha inhibitor, thereby generating an expanded population of Lgr5+ cells;, thereby generating Myo7a+ cochlear cells.

[0051] Other objects and features will be in part apparent and in part pointed out hereinafter.

DETAILED DESCRIPTION

Definitions [0052] In this application, the use of "or" includes "and/or" unless stated otherwise. As used in this application, the term "comprise" and variations of the term, such as "comprising" and "comprises," are not intended to exclude other additives, components, integers or steps. By "consisting of is meant including, and limited to, whatever follows the phrase "consisting of." Thus, the phrase "consisting of indicates that the listed elements are required or mandatory, and that no other elements may be present. By "consisting essentially of is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase "consisting essentially of indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present depending upon whether or not they materially affect the activity or action of the listed elements.

[0053] As used in this application, the terms "about" and "approximately" are used as equivalents. Any numerals used in this application with or without about/approximately are meant to cover any normal fluctuations appreciated by one of ordinary skill in the relevant art. In certain embodiments, the term "approximately" or "about" refers to a range of values that fall within 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater than or less than) of the stated reference value unless otherwise stated or otherwise evident from the context (except where such number would exceed 100% of a possible value).

[0054] "Administration" refers to introducing a substance into a subject. In some embodiments, administration is auricular, intraauricular, intracochlear, intravestibular, or transtympanically, e.g. , by injection. In some embodiments, administration is directly to the inner ear, e.g. injection through the round window, otic capsule, or vestibular canals. In some embodiments, administration is directly into the inner ear via a cochlear implant delivery system. In some embodiments, the substance is injected transtympanically to the middle ear. In certain embodiments "causing to be administered" refers to administration of a second component after a first component has already been administered (e.g., at a different time and/or by a different actor).

[0055] An "antibody" refers to an immunoglobulin polypeptide, or fragment thereof, having immunogen binding ability. [0056] As used herein, an "agonist" is an agent that causes an increase in the expression or activity of a target gene, protein, or a pathway, respectively. Therefore, an agonist can bind to and activate its cognate receptor in some fashion, which directly or indirectly brings about this physiological effect on the target gene or protein. An agonist can also increase the activity of a pathway through modulating the activity of pathway components, for example, through inhibiting the activity of negative regulators of a pathway. Therefore, a "Wnt agonist" can be defined as an agent that increases the activity of Wnt pathway, which can be measured by increased TCF/LEF-mediated transcription in a cell. Therefore, a "Wnt agonist" can be a true Wnt agonist that bind and activate a Frizzled receptor family member, including any and all of the Wnt family proteins, an inhibitor of intracellular beta-catenin degradation, and activators of TCF/LEF.

[0057] An "antagonist" refers to an agent that binds to a receptor, and which in turn decreases or eliminates binding by other molecules.

[0058] "Antisense" refers to a nucleic acid sequence, regardless of length, that is complementary to the coding strand or mRNA of a nucleic acid sequence. Antisense RNA can be introduced to an individual cell, tissue or organoid. An anti-sense nucleic acid can contain a modified backbone, for example, phosphorothioate, phosphorodithioate, or other modified backbones known in the art, or may contain non-natural internucleoside linkages.

[0059] As referred to herein, a "complementary nucleic acid sequence" is a nucleic acid sequence capable of hybridizing with another nucleic acid sequence comprised of complementary nucleotide base pairs. By "hybridize" is meant pair to form a double- stranded molecule between complementary nucleotide bases (e.g., adenine (A) forms a base pair with thymine (T), as does guanine (G) with cytosine (C) in DNA) under suitable conditions of stringency. (See, e.g., Wahl, G. M. and S. L. Berger (1987) Methods Enzymol. 152:399; Kimmel, A. R. (1987) Methods Enzymol. 152:507).

[0060] "Auricular administration" refers to a method of using a catheter or wick device to administer a composition across the tympanic membrane to the inner ear of the subject. To facilitate insertion of the wick or catheter, the tympanic membrane may be pierced using a suitably sized syringe or pipette. The devices could also be inserted using any other methods known to those of skill in the art, e.g., surgical implantation of the device. In particular embodiments, the wick or catheter device may be a stand-alone device, meaning that it is inserted into the ear of the subject and then the composition is controllably released to the inner ear. In other particular embodiments, the wick or catheter device may be attached or coupled to a pump or other device that allows for the administration of additional compositions. The pump may be automatically programmed to deliver dosage units or may be controlled by the subject or medical professional.

[0061] "Cell Aggregate" as used herein shall mean a body cells in the Organ of Corti that have proliferated to form a cluster of a given cell type that is greater than 40 microns in diameter and/or produced a morphology in which greater than 3 cell layers reside perpendicular to the basilar membrane. A "Cell Aggregate" can also refer a process in which cell division creates a body of cells that cause one or more cell types to breach the reticular lamina, or the boundary between endolymph and perilymph

[0062] "Cell Density" as used herein in connection with a specific cell type is the mean number of that cell type per area in a Representative Microscopy Sample. The cell types may include but are not limited to Lgr5 ⁺ cells, hair cells, or supporting cells. The Cell Density may be assessed with a given cell type in a given organ or tissue, including but not limited to the cochlea or Organ of Corti. For instance, the Lgr5 ⁺ Cell Density in the Organ of Corti is the Cell Density of Lgr5 ⁺ cells as measured across the Organ of Corti. Typically, supporting cells and Lgr5 ⁺ cells will be enumerated by taking cross sections of the Organ of Corti.

Typically, hair cells will be enumerated by looking down at the surface of the Organ of Corti, though cross sections may be used in some instances, as described in a Representative Microscopy Sample. Typically, Cell Density of Lgr5 ⁺ cells will be measured by analyzing whole mount preparations of the Organ of Corti and counting the number of Lgr5 cells across a given distance along the surface of the epithelia, as described in a Representative

Microscopy Sample. Hair cells may be identified by their morphological features such as bundles or hair cell specific stains (e.g., Myosin Vila, Prestin, vGlut3, Pou4f3, Espin, conjugated-Phalloidin, PMCA2, Ribeye, Atohl, etc.). Lgr5 ⁺ cells may be identified by specific stains or antibodies (e.g., Lgr5-GFP transgenic reporter, anti-Lgr5 antibody, etc.)

[0063] "Cochlear Concentration" as used herein will be the concentration of a given agent as measured through sampling cochlear fluid. Unless otherwise noted, the sample should contain a substantial enough portion of the cochlear fluid so that it is approximately representative of the average concentration of the agent in the cochlea. For example, samples may be drawn from a vestibular canal, and a series of fluid samples drawn in series such that individual samples are comprised of cochlear fluid in specified portions of the cochlea [0064] "Complementary nucleic acid sequence" refers to a nucleic acid sequence capable of hybridizing with another nucleic acid sequence comprised of complementary nucleotide base pairs.

[0065] "Cross-Sectional Cell Density" as used herein in connection with a specific cell type is the mean number of that cell type per area of cross section through a tissue in a

Representative Microscopy Sample. Cross sections of the Organ of Corti can also be used to determine the number of cells in a given plane. Typically, hair cells Cross-sectional Cell Density will be measured by analyzing whole mount preparations of the Organ of Corti and counting the number of hair cells across a given distance in cross sections taken along a portion of the epithelia, as described in a Representative Microscopy Sample. Typically, Cross-sectional Cell Density of Lgr5 ⁺ cells will be measured by analyzing whole mount preparations of the Organ of Corti and counting the number of Lgr5 ⁺ cells across a given distance in cross sections taken along a portion of the epithelia, as described in a

Representative Microscopy Sample. Hair cells may be identified by their morphological features such as bundles or hair cell specific stains (suitable stains include e.g. , Myosin Vila, Prestin, vGlut3, Pou4f3, conjugated-Phalloidin, PMCA2, Atohl, etc.). Lgr5 ⁺ cells may be identified by specific stains or antibodies (suitable stains and antibodies include fluorescence in situ hybridization of Lgr5 mRNA, Lgr5-GFP transgenic reporter system, anti-Lgr5 antibodies, etc.).

[0066] "Decreasing" refers to decreasing by at least 5%, for example, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99 or 100%, for example, as compared to the level of reference.

[0067] "Decreases" also means decreases by at least 1-fold, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 500, 1000-fold or more, for example, as compared to the level of a reference.

[0068] "Differentiation Inhibitor" as used herein is an agent which may inhibit differentiation of an inner ear stem cell into an inner ear hair cell. Some differentiation inhibitors maintain expression of post-natal Stem Cell Markers. Some Differentiation Inhibitors include, without limitation, Notch agonists and HDAC inhibitors.

[0069] "Differentiation Period" as used herein is the duration of time in which there is an Effective Sternness Driver Concentration without an Effective Differentiation Inhibition Concentration. [0070] "Effective Concentration" may be the Effective Sternness Driver Concentration for a Sternness Driver or the Effective Differentiation Inhibition Concentration for a

Differentiation Inhibitor.

[0071] "Effective Differentiation Inhibition Concentration" is the minimum concentration of a Differentiation Inhibitor that does not allow more than a 50% increase in the fraction of the total population of cells that are hair cells at the end of the Stem Cell Proliferation Assay compared to the start of the Stem Cell Proliferation Assay In measuring the Effective Differentiation Inhibition Concentration, a Hair Cell stain for cells may be used with flow cytometry to quantify hair cells for a mouse strain that is not an Atohl-GFP mouse.

Alternatively, and Atohl-GFP mouse strain may be used.

[0072] "Effective Release Rate" (mass/time) as used herein is the Effective Concentration (mass/volume) * 30 uL / 1 hour.

[0073] "Effective Sternness Driver Concentration" is the minimum concentration of a Sternness Driver that induces at least 1.5-fold increase in number of LGR5+ cells in a Stem Cell Proliferation Assay compared to the number of Lgr5+ cells in a Stem Cell Proliferation Assay performed without the Sternness Driver and with all other components present at the same concentrations.

[0074] "Eliminate" means to decrease to a level that is undetectable.

[0075] "Engraft" or "engraftment" refers to the process of stem or progenitor cell incorporation into a tissue of interest in vivo through contact with existing cells of the tissue. "Epithelial progenitor cell" refers to a multipotent cell which has the potential to become restricted to cell lineages resulting in epithelial cells.

[0076] "Epithelial stem cell" refers to a multipotent cell which has the potential to become committed to multiple cell lineages, including cell lineages resulting in epithelial cells.

[0077] "Fragment" refers to a portion of a polypeptide or nucleic acid molecule. This portion contains, preferably, at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the entire length of the reference nucleic acid molecule or polypeptide. A fragment may contain 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 nucleotides or amino acids.

[0078] "GSK3-alpha," "GSK3a," and "GSK3A" as used interchangeably herein are acronyms for glycogen synthase kinase 3 alpha. [0079] "GSK3 -alpha inhibitor" is a compound or composition that inhibits the activity of GSK3-alpha (e.g., any one of the GSK3-alpha inhibitors disclosed herein, e.g., in Table 1).

[0080] "GSK3-beta," "GSK-3 ," and "GSK-3B" as used interchangeably herein are acronyms for glycogen synthase kinase 3 beta.

[0081] "GSK3-beta inhibitor" is a compound or composition that inhibits the activity of GSK3beta.

[0082] "GSK3-alpha potency" refers to the ICso value of a GSK3-alpha inhibitor. The IC50 values can be measured using any suitable method known in the art. In one embodiment, activity assays include approximately 0.2 uM enzyme (e.g., GSK3-alpha) alone or with 10 μΜ known peptide substrates. Peptides are subjected to a kinase reaction (10 mM HEPES [pH 7.0], 10 mM MgC12, 200 μΜ EDTA, 100 μΜ cold ATP, 1 μθί [γ- 32P] ATP) to determine time-dependent phosphate incorporations into the peptides.

[0083] "GSK3-beta potency" refers to the ICso value of a GSK3-beta inhibitor.

[0084] "GSK3-alpha selective" refers to a GSK3-alpha inhibitor that has a higher potency against GSK3-alpha, than it does against another target, e.g., GSK3-beta, a CDK, MAPK, ERK, or MEK.

[0085] The "GSK3-alpha/CDK selectivity ratio" for a given compound (e.g., a GSK3-alpha inhibitor) is the ratio of the compound's ICso for a CDK divided by its ICso for GSK3-alpha.

[0086] The "GSK3-alpha/GSK3-beta selectivity ratio" for a given compound (e.g., a GSK3- alpha inhibitor) is the ratio of the compound's IC50 for GSK3-beta divided by its IC50 for GSK3-alpha.

[0087] The "GSK3-alpha/ERK selectivity ratio" for a given compound (e.g., a GSK3-alpha inhibitor) is the ratio of the compound's IC50 for ERK divided by its IC50 for GSK3 -alpha.

[0088] The "GSK3-alpha/MAPK selectivity ratio" for a given compound (e.g., a GSK3- alpha inhibitor) is the ratio of the compound's IC50 for MAPK divided by its IC50 for GSK3- alpha.

[0089] The "GSK3-alpha/MEK selectivity ratio" for a given compound (e.g., a GSK3 -alpha inhibitor) is the ratio of the compound's IC50 for MEC divided by its IC50 for GSK3-alpha.

[0090] "Hybridize" refers to pairing to form a double-stranded molecule between complementary nucleotide bases (e.g., adenine (A) forms a base pair with thymine (T), as does guanine (G) with cytosine (C) in DNA) under suitable conditions of stringency. (See, e.g., Wahl, G. M. and S. L. Berger (1987) Methods Enzymol. 152:399; Kimmel, A. R. (1987) Methods Enzymol. 152:507).

[0091] An "inhibitor" refers to an agent that causes a decrease in the expression or activity of a target gene or protein, respectively. An "antagonist" can be an inhibitor, but is more specifically an agent that binds to a receptor, and which in turn decreases or eliminates binding by other molecules.

[0092] As used herein, an "inhibitory nucleic acid" is a double-stranded RNA, RNA interference, miRNA, siRNA, shRNA, or antisense RNA, or a portion thereof, or a mimetic thereof, that when administered to a mammalian cell results in a decrease in the expression of a target gene. Typically, a nucleic acid inhibitor comprises at least a portion of a target nucleic acid molecule, or an ortholog thereof, or comprises at least a portion of the complementary strand of a target nucleic acid molecule. Typically, expression of a target gene is reduced by 10%, 25%, 50%, 75%, or even 90-100%.

[0093] "In Vitro Lgr5 activity" refers to the level of expression or activity of Lgr5 in an in vitro population of cells. It may be measured, for example, in cells derived from a Lgr5-GFP expressing mouse such as a B6.129P2-Lgr5tml(cre/ERT2)Cle/J mouse (also known as Lgr5- EGFP-IRES-creERT2 or Lgr5-GFP mouse, Jackson Lab Stock No: 008875) by dissociating cells to single cells, staining with propidium iodide (PI), and analyzing the cells using a flow cytometer for Lgr5-GFP expression. Inner ear epithelial cells from wild-type (non-Lgr5- GFP) mice that passing the same culturing and analyzing procedures can be used as a negative control. Typically, two population of cells are shown in the bivariate plot with GFP/FITC as one variable, which include both GFP positive and GFP negative populations. Lgr5 -positive cells are identified by gating GFP positive cell population. The percentage of Lgr5 -positive cells are measured by gating GFP positive cell population against both GFP negative population and the negative control. The number of Lgr5 -positive cells is calculated by multiplying the total number of cells by the percentage of Lgr5-positive cells. For cells derived from non-Lgr5-GFP mice, Lgr5 activity can be measured using an anti-Lgr5 antibody or quantitative-PCR on the Lgr5 gene.

[0094] "In Vivo Lgr5 activity" as used herein is the level of expression or activity of Lgr5 in a subject. It may be measured, for example, by removing an animal's inner ear and measuring Lgr5 protein or Lgr5 mRNA. Lgr5 protein production can be measured using an anti-Lgr5 antibody to measure fluorescence intensity as determined by imaging cochlear samples, where fluorescence intensity is used as a measure of Lgr5 presence. Western blots can be used with an anti-Lgr5 antibody, where cells can be harvested from the treated organ to determine increases in Lgr5 protein. Quantitative-PCR or RNA in situ hybridization can be used to measure relative changes in Lgr5 mRNA production, where cells can be harvested from the inner ear to determine changes in Lgr5 mRNA. Alternatively, Lgr5 expression can be measured using an Lgr5 promoter driven GFP reporter transgenic system, where the presence or intensity GFP fluoresce can be directly detected using flow cytometry, imaging, or indirectly using an anti-GFP antibody.

[0095] "Increases" also means increases by at least 1-fold, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 500, 1000-fold or more, for example, as compared to the level of a as compared to the level of a reference standard.

[0096] "Increasing" refers to increasing by at least 5%, for example, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, 100% or more, for example, as compared to the level of a reference.

[0097] "Intraauricular administration" refers to administration of a composition to the middle or inner ear of a subject by directly injecting the composition.

[0098] "Intracochlear" administration refers to direct injection of a composition across the tympanic membrane and across the round window membrane into the cochlea.

[0099] "Intravestibular" administration refers to direct injection of a composition across the tympanic membrane and across the round window membrane into the vestibular organs.

[00100] "Isolated" refers to a material that is free to varying degrees from components which normally accompany it as found in its native state. "Isolate" denotes a degree of separation from original source or surroundings.

[00101] "Lgr5" is an acronym for the Leucine-rich repeat-containing G-protein coupled receptor 5, also known as G-protein coupled receptor 49 (GPR49) or G-protein coupled receptor 67 (GPR67). It is a protein that in humans is encoded by the Lgr5 gene.

[00102] "Lgr5 activity" is defined as the level of activity of Lgr5 in a population of cells. In an in vitro cell population, Lgr5 activity may be measured in an in vitro Lgr5 Activity assay. In an in vivo cell population, Lgr5 activity may be measured in an in vivo Lgr5 Activity assay. [00103] "Lgr5 ⁺ cell" or "Lgr5-positive cell" as used herein is a cell that expresses Lgr5. "Lgr5 ^" cell" as used herein is a cell that is not Lgr5 ⁺ .

[00104] "Lineage Tracing" as used herein is using a mouse line that enables fate tracing of any cell that expresses a target gene at the time of reporter induction. This can include hair cell or supporting cells genes (Sox2, Lgr5, MyosinVIIa, Pou4f3, etc). For example, lineage tracing may use an Lgr5-EGFP-IRES-creERT2 mouse crossed with a reporter mouse, which upon induction, allows one to trace the fate of cells that expressed Lgr5 at the time of induction. By further example, Lgr5 cells can be isolated into single cells and cultured in a Stem Cell Proliferation Assay to generate colonies, then subsequently differentiated in a Differentiation Assay and analyzed for cell fate by staining for hair cell and/or supporting cell proteins and determinning the reporter colocalization with either hair cell or supporting cell staining to determine the Lgr5 cells' fate. In addition, lineage tracing can be performed in cochlear explants to track supporting cell or hair cell fate within the intact organ after treatment. For example, Lgr5 cell fate can be determined by isolating the cochlea from a Lgr5-EGFP-IRES-creERT2 mouse crossed with a reporter mouse, and inducing the reporter in Lgr5 cells before or during treatment. The organ can then be analyzed for cell fate by staining for hair cell and/or supporting cell proteins and determinning the reporter colocalization with either hair cell or supporting cell staining to determine the Lgr5 cells' fate. In addtion, lineage tracing can be performed in vivo track supporting cell or hair cell fate within the intact organ after treatment. For example, Lgr5 cell fate can be determined inducing a reporter in an Lgr5-EGFP-IRES-creERT2 mouse crossed with a reporter mouse, treating the animal, then isolating the cochlea. The organ can then be analyzed for cell fate by staining for hair cell and/or supporting cell proteins and determinning the reporter colocalization with either hair cell or supporting cell staining to determine the Lgr5 cells' fate. Lineage tracing may be performed using alternative reporters of interest as is standard in the art.

[00105] "Mammal" refers to any mammal including but not limited to human, mouse, rat, sheep, monkey, goat, rabbit, hamster, horse, cow or pig.

[00106] "Mean Release Time" as used herein is the time in which one-half of an agent is released into phosphate buffered saline from a carrier in a Release Assay.

[00107] "Native Morphology" as used herein is means that tissue organization largely reflects the organization in a healthy tissue. [00108] "Non-human mammal", as used herein, refers to any mammal that is not a human.

[00109] As used in relevant context herein, the term "number" of cells can be 0, 1, or more cells.

[00110] "Organ of Corti" as used herein refers to the sensory cells (inner and outer hair cells) of the hearing organ located in the cochlea.

[00111] "Organoid" or "epithelial organoid" refers to a cell cluster or aggregate that resembles an organ, or part of an organ, and possesses cell types relevant to that particular organ.

[00112] "Population" of cells refers to any number of cells greater than 1, but is preferably at least 1X10 ³ cells, at least 1X10 ⁴ cells, at least at least 1X10 ⁵ cells, at least 1X10 ⁶ cells, at least 1X10 ⁷ cells, at least 1X10 ⁸ cells, at least 1X10 ⁹ cells, or at least 1X10 ¹⁰ cells.

[00113] "Progenitor cell" as used herein refers to a cell that, like a stem cell, has the tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its "target" cell.

[00114] "Proliferation Period" as used herein is the duration of time in which there is an Effective Sternness Driver Concentration and a Differentiation Inhibition Concentration of a Differentiation Inhibitor.

[00115] In certain embodiments, the "purity" of any given compound in a composition may be specifically defined. For instance, certain compositions may comprise a compound that is at least 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% pure, including all decimals in between, as measured, for example and by no means limiting, by high performance liquid chromatography (HPLC), a well-known form of column chromatography used frequently in biochemistry and analytical chemistry to separate, identify, and quantify compounds.

[00116] "Reference" means a standard or control condition (e.g., untreated with a test agent or combination of test agents).

[00117] "Release Assay" as used herein is a test in which the rate of release of an agent from a Biocompatible Matrix through dialysis membrane to a saline environment. An exemplary Release Assay may be performed by placing 30 microliters of a composition in 1 ml Phosphate Buffered Saline inside saline dialysis bag with a suitable cutoff, and placing the dialysis bag within 10 mL of Phosphate Buffered Saline at 37 °C. The dialysis membrane size may be chosen based on agent size in order to allow the agent being assessed to exit the membrane. For small molecule release, a 3.5-5 kDa cutoff may be used. The agent may be a Sternness Driver, Differentiation Inhibitor, or other agent. The Release Rate for a composition may change over time and may be measured in 1 hour increments.

[00118] "Representative Microscopy Sample" as used herein describes a sufficient number of fields of view within a cell culture system, a portion of extracted tissue, or an entire extracted organ that the average feature size or number being measured can reasonably be said to represent the average feature size or number if all relevant fields were measured. For example, in order to assess the hair cell counts at a frequency range on the Organ of Corti, ImageJ software (NIH) can used to measure the total length of cochlear whole mounts and the length of individual counted segments. The total number of inner hair cells, outer hair cells, and supporting cells can be counted in the entire or fraction of any of the four cochlear segments of 1200-1400 μιτι (apical, mid-apical, mid-basal, and basal) at least 3 fields of view at Ι ΟΟμιτι field size would be reasonably considered a Representative Microscopy Sample. A Representative Microscopy sample can include measurements within a field of view, which can be measured as cells per a given distance. A Representative Microscopy sample can be used to assess morphology, such as cell-cell contacts, cochlear architecture, and cellular components (e.g. , bundles, synapses).

[00119] "Rosette Patterning" is a characteristic cell arrangement in the cochlea in which <5% hair cells are adjacent to other hair cells.

[00120] The term "sample" refers to a volume or mass obtained, provided, and/or subjected to analysis. In some embodiments, a sample is or comprises a tissue sample, cell sample, a fluid sample, and the like. In some embodiments, a sample is taken from (or is) a subject (e.g., a human or animal subject). In some embodiments, a tissue sample is or comprises brain, hair (including roots), buccal swabs, blood, saliva, semen, muscle, or from any internal organs, or cancer, precancerous, or tumor cells associated with any one of these. A fluid may be, but is not limited to, urine, blood, ascites, pleural fluid, spinal fluid, and the like. A body tissue can include, but is not limited to, brain, skin, muscle, endometrial, uterine, and cervical tissue or cancer, precancerous, or tumor cells associated with any one of these. In an embodiment, a body tissue is brain tissue or a brain tumor or cancer. Those of ordinary skill in the art will appreciate that, in some embodiments, a "sample" is a "primary sample" in that it is obtained from a source (e.g., a subject); in some embodiments, a "sample" is the result of processing of a primary sample, for example to remove certain potentially contaminating components and/or to isolate or purify certain components of interest. [00121] "A selectivity ratio" for a given compound is the ratio of the compound's potency against a control enzyme as compared to its potency against a test enzyme. For example, the "GSK3-alpha/GSK3-beta selectivity ratio" for a given inhibitor is the ratio of the compound's IC50 for GSK3-beta divided by its IC50 for GSK3-alpha. Similarly, the GSK3-alpha/MEK selectivity ratio for a given inhibitor is the ratio of the compound's IC50 for MEK divided by its IC50 for GSK3-alpha.

[00122] "Self-renewal" refers to the process by which a stem cell divides to generate one (asymmetric division) or two (symmetric division) daughter cells with development potentials that are indistinguishable from those of the mother cell. Self-renewal involves both proliferation and the maintenance of an undifferentiated state.

[00123] "siRNA" refers to a double stranded RNA. Optimally, an siRNA is 18, 19, 20, 21, 22, 23 or 24 nucleotides in length and has a 2 base overhang at its 3' end. These dsRNAs can be introduced to an individual cell or culture system. Such siRNAs are used to downregulate mRNA levels or promoter activity.

[00124] "Stem cell" refers to a multipotent cell having the capacity to self-renew and to differentiate into multiple cell lineages.

[00125] "Stem Cell Differentiation Assay" as used herein is an assay to determine the differentiation capacity of stem cells. In an exemplary Stem Cell Differentiation Assay, the number of cells for an initial cell population is harvested from a Atohl-GFP mouse between the age of 3 to 7 days, by isolating the Organ of Corti sensory epithelium, dissociating the epithelium into single cells, and passing the cells through a 40um cell strainer.

Approximately 5000 cells are entrapped in 40 μΐ of culture substrate (for example: Matrigel (Corning, Growth Factor Reduced)) and placed at the center of wells in a 24-well plate with 500 μΐ of an appropriate culture media, growth factors and agent being tested. Appropriate culture media and growth factors include Advanced DMEM/F12 with media Supplements (IX N2, IX B27, 2 mM Glutamax, 10 mM HEPES, 1 mM N-acetylcysteine, and 100 U/ml Penicillin/100 μg/ml Streptomycin) and growth factors (50 ng/ml EGF, 50 ng/ml bFGF, and 50 ng/ml IGF-1) as well as the agent(s) being assessed are added into each well. Cells are cultured for 10 days in a standard cell culture incubator at 37 ^° C and 5% CO2, with media change every 2 days. These cells are then cultured by removing the Stem Cell Proliferation Assay agents and replacing with Basal culture media and molecules to drive differentiation. An appropriate Basal culture media is Advanced DMEM/F12 supplemented with IX N2, IX B27, 2 mM Glutamax, 10 mM HEPES, 1 mM N-acetylcysteine, and 100 U/ml Penicillin/100 μg/ml Streptomycin and appropriate molecules to drive differentiation are 3 μΜ CHIR99021 and 5 μΜ DAPT for 10 days, with media change every 2 days. The number of hair cells in a population may be measured by using flow cytometry for GFP. Hair cell differentiation level can further be assessed using qPCR to measure hair cell marker (e.g., Myo7a) expression level normalized using suitable and unregulated references or housekeeping genes (e.g. , Hprt). Hair cell differentiation level can also be assessed by immunostaining for hair cell markers (e.g. Myosin7a, vGlut3, Espin, PMCAs, Ribeye, conjugated-phalloidin, Atohl, Pou4f3, etc.). Hair cell differentiation level can also be assessed by Western Blot for Myosin7a, vGlut3, Espin, PMCAs, Prestin, Ribeye, Atohl, Pou4f3.

[00126] "Stem Cell Assay" as used herein is an assay in which a cell or a cell population are tested for a series of criteria to determine whether the cell or cell population are stem cells or enriched in stem cells or stem cell markers. In a stem cell assay, the cell/cell population are tested for stem cell characteristics such as expression of Stem Cell Markers, and further optionally are tested for stem cell function, including the capacity of self-renewal and differentiation.

[00127] "Stem Cell Proliferator" as used herein is a compound (or composition, if so indicated) that induces an increase in a population of cells which have the capacity for self- renewal and differentiation.

[00128] "Stem Cell Proliferation Assay" as used herein is an assay to determine the capacity for agent(s) to induce the creation of stem cells from a starting cell population. In an exemplary Stem Cell Proliferation Assay, the number of cells for an initial cell population is harvested from a Lgr5-GFP mouse such as a B6.129P2-Lgr5tml(cre/ERT2)Cle/J mouse (also known as Lgr5-EGFP-IRES-creERT2 or Lgr5-GFP mouse, Jackson Lab Stock No: 008875) between the age of 3 to 7 days, by isolating the Organ of Corti sensory epithelium and dissociating the epithelium into single cells. Approximately 5000 cells are entrapped in 40 μΐ of culture substrate (for example: Matrigel (Coming, Growth Factor Reduced)) and placed at the center of wells in a 24-well plate with 500 μΐ of an appropriate culture media, growth factors and agent being tested. Appropriate culture media and growth factors include Advanced DMEM/F12 with media Supplements (IX N2, IX B27, 2 mM Glutamax, 10 mM HEPES, 1 mM N-acetylcysteine, and 100 U/ml Penicillin/100 μg/ml Streptomycin) and growth factors (50 ng/ml EGF, 50 ng/ml bFGF, and 50 ng/ml IGF-1) as well as the agent(s) being assessed are added into each well. Cells are cultured for 10 days in a standard cell culture incubator at 37 ^° C and 5% CC , with media change every 2 days. The number of Lgr5 ⁺ cells is quantified by counting the number of cells identified as Lgr5+ in an In

Vitro Lgr5 activity assay. The fraction of cells that are Lgr5 ⁺ is quantified by dividing the number of cells identified as Lgr5 ⁺ in a cell population by the total number of cells present in the cell population. The average Lgr5 ⁺ activity of a population is quantified by measuring the average mRNA expression level of Lgr5 of the population normalized using suitable and unregulated references or housekeeping genes (e.g. , Hprt). The number of hair cells in a population may be measured by staining with hair cell marker (e.g., MyosinVIIa), or using an endogenous reporter of hair cell genes (e.g., Pou4f3-GFP, Atohl-nGFP) and analyzing using flow cytometry. The fraction of cells that are hair cells is quantified by dividing the number of cells identified as hair cells in a cell population by the total number of cells present in the cell population. Lgr5 activity can be measured by qPCR.

[00129] "Stem Cell Markers" as used herein can be defined as gene products (e.g. protein, RNA, etc.) that specifically expressed in stem cells. One type of stem cell marker is gene products that are directly and specifically support the maintenance of stem cell identity. Examples include Lgr5 and Sox2. Additional stem cell markers can be identified using assays that were described in the literatures. To determine whether a gene is required for maintenance of stem cell identity, gain-of-function and loss-of-function studies can be used. In gain-of-function studies, over expression of specific gene product (the stem cell marker) would help maintain the stem cell identity. While in loss-of-function studies, removal of the stem cell marker would cause loss of the stem cell identity or induced the differentiation of stem cells. Another type of stem cell marker is gene that only expressed in stem cells but does not necessary to have specific function to maintain the identity of stem cells. This type of markers can be identified by comparing the gene expression signature of sorted stem cells and non-stem cells by assays such as micro-array and qPCR. This type of stem cell marker can be found in the literature, (e.g. Liu Q. et al, Int J Biochem Cell Biol. 2015 Mar;60:99- 111. http://www.ncbi.nlm.nih.gov/pubmed/25582750). Potential stem cell markers include Ccdcl21, GdflO, Opcml, Phex, etc. The expression of stem cell markers such as Lgr5 or Sox2 in a given cell or cell population can be measure using assays such as qPCR, immunohistochemistry, western blot, and RNA hybridization. The expression of stem cell markers can also be measured using transgenic cells express reporters which can indicate the expression of the given stem cell markers, e.g. Lgr5-GFP or Sox2-GFP. Flow cytometry analysis can then be used to measure the activity of reporter expression. Fluorescence microscopy can also be used to directly visualize the expression of reporters. The expression of stem cell markers may further be determined using microarray analysis for global gene expression profile analysis. The gene expression profile of a given cell population or purified cell population can be compared with the gene expression profile of the stem cell to determine similarity between the 2 cell populations. Stem cell function can be measured by colony forming assay or sphere forming assay, self-renewal assay and differentiation assay. In colony (or sphere) forming assay, when cultured in appropriate culture media, the stem cell should be able to form colonies, on cell culture surface (e.g. cell culture dish) or embedded in cell culture substrate (e.g. Matrigel) or be able to form spheres when cultured in suspension. In colony/sphere forming assay, single stem cells are seeded at low cell density in appropriate culture media and allowed to proliferate for a given period of time (7-10 days). Colony formed are then counted and scored for stem cell marker expression as an indicator of sternness of the original cell. Optionally, the colonies that formed are then picked and passaged to test its self-renewal and differentiation potential. In self-renewal assay, when cultured in appropriate culture media, the cells should maintain stem cell marker (e.g. Lgr5) expression over at least one (e.g., 1, 2, 3, 4, 5, 10, 20, etc.) cell divisions. In a Stem Cell Differentiation Assay, when cultured in appropriate differentiation media, the cells should be able to generate hair cell which can be identified by hair cell marker expression measured by qPCR, immunostaining, western blot, RNA hybridization or flow cytometry.

[00130] "Sternness Driver" as used herein is a composition that induces proliferation of LGR5 ⁺ cells, upregulates Lgr5 in cells, or maintains Lgr5 expression in cells, while maintaining the potential for self-renewal and the potential to differentiate into hair cells. Generally, sternness drivers upregulate at least one biomarker of post-natal stem cells.

Sternness Drivers include but are not limited to Wnt agonists and GSK3Beta inhibitors.

[00131] "Subject" includes humans and mammals (e.g. , mice, rats, pigs, cats, dogs, and horses). In some embodiments, subjects are be mammals, particularly primates, especially humans. In some embodiments, subjects are livestock such as cattle, sheep, goats, cows, swine, and the like; poultry such as chickens, ducks, geese, turkeys, and the like; and domesticated animals particularly pets such as dogs and cats. In some embodiments (e.g., particularly in research contexts) subject mammals will be, for example, rodents (e.g., mice, rats, hamsters), rabbits, primates, or swine such as inbred pigs and the like.

[00132] "Supporting Cell" as used herein in connection with a cochlear epithelium comprises epithelial cells within the organ of Corti that are not hair cells. This includes inner pillar cells, outer pillar cells, inner phalangeal cells, Deiter cells, Hensen cells, Boettcher cells, and/or Claudius cells.

[00133] By "statistically significant", it is meant that the result was unlikely to have occurred by chance. Statistical significance can be determined by any method known in the art.

Commonly used measures of significance include the p-value, which is the frequency or probability with which the observed event would occur, if the null hypothesis were true. If the obtained p-value is smaller than the significance level, then the null hypothesis is rejected. In simple cases, the significance level is defined at a p-value of 0.05 or less.

[00134] "Substantially" or "essentially" means nearly totally or completely, for instance, 95% or greater of some given quantity.

[00135] "Synergy" or "synergistic effect" is an effect which is greater than the sum of each of the effects taken separately; a greater than additive effect.

[00136] "TGF-beta inhibitor" as used herein is a composition that reduces activity of TGF- beta.

[00137] "Tissue" is an ensemble of similar cells from the same origin that together carry out a specific function including, for example, tissue of cochlear, such as the Organ of Corti.

[00138] "Transtympanic" administration refers to direct injection of a composition across the tympanic membrane into the middle ear.

[00139] "Treating" as used herein in connection with a cell population means delivering a substance to the population to effect an outcome. In the case of in vitro populations, the substance may be directly (or even indirectly) delivered to the population. In the case of in vivo populations, the substance may be delivered by administration to the host subject.

[00140] "Valproic acid" (VP A) has chemical formula CsHieC and the following alternate name: 2-propylpentanoic acid. Its chemical structure is as follows:

[00141] In some embodiments, reference herein to "valproic acid" or "VP A" means "valproic acid, or a pharmaceutically-acceptable salt thereof."

[00142] "Wnt activation" as used herein is an activation of the Wnt signaling pathway. [00143] "Pharmaceutically-acceptable salt" includes both acid and base addition salts.

[00144] "Pharmaceutically-acceptable acid addition salt" refers to those salts which retain the biological effectiveness and properties of the free bases, which are not biologically or otherwise undesirable, and which are formed with inorganic acids such as, but are not limited to, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as, but not limited to, acetic acid, 2,2-dichloroacetic acid, adipic acid, alginic acid, ascorbic acid, aspartic acid, benzenesulfonic acid, benzoic acid, 4- acetamidobenzoic acid, camphoric acid, camphor- 10-sulfonic acid, capric acid, caproic acid, caprylic acid, carbonic acid, cinnamic acid, citric acid, cyclamic acid, dodecylsulfuric acid, ethane- 1 ,2-disulfonic acid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, formic acid, fumaric acid, galactaric acid, gentisic acid, glucoheptonic acid, gluconic acid, glucuronic acid, glutamic acid, glutaric acid, 2-oxo-glutaric acid, glycerophosphoric acid, gly colic acid, hippuric acid, isobutyric acid, lactic acid, lactobionic acid, lauric acid, maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonic acid, mucic acid, naphthalene-1,5- disulfonic acid, naphthalene-2-sulfonic acid, l-hydroxy-2-naphthoic acid, nicotinic acid, oleic acid, orotic acid, oxalic acid, palmitic acid, pamoic acid, propionic acid, pyroglutamic acid, pyruvic acid, salicylic acid, 4-aminosalicylic acid, sebacic acid, stearic acid, succinic acid, tartaric acid, thiocyanic acid, / toluenesulfonic acid, trifluoroacetic acid, undecylenic acid, and the like.

[00145] "Pharmaceutically-acceptable base addition salt" refers to those salts which retain the biological effectiveness and properties of the free acids, which are not biologically or otherwise undesirable. These salts are prepared from addition of an inorganic base or an organic base to the free acid. Salts derived from inorganic bases include, but are not limited to, the sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. For example, inorganic salts include, but are not limited to, ammonium, sodium, potassium, calcium, and magnesium salts. Salts derived from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as ammonia, isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, diethanolamine, ethanolamine, deanol, 2- dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, benethamine, benzathine, ethylenediamine, glucosamine, methylglucamine, theobromine, triethanolamine, tromethamine, purines, piperazine, piperidine, N-ethylpiperidine, polyamine resins and the like. Example organic bases used in certain embodiments include isopropylamine, diethylamine, ethanolamine, trimethylamine, dicyclohexylamine, choline and caffeine.

[00146] A description of exemplary embodiments of the disclosure follows.

[00147] The present disclosure relates to methods and compositions for activating the Wnt pathway and/or inhibiting GSK3 -alpha activity.

[00148] In some aspects the present disclosure provides a method for controlled proliferation of stem cells comprising an initial phase of inducing sternness while inhibiting differentiation and a subsequent phase of differentiation of the stem cells into tissue cells comprising administering to a cell population an effective amount of a GSK3 -alpha inhibitor or a pharmaceutically-acceptable salt thereof, optionally in combination with a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor, e.g., valproic acid). In some embodiments, the Differentiation Inhibitor is an HDAC inhibitor or a Notch agonist. In some embodiments, the Differentiation Inhibitor is valproic acid, or a pharmaceutically-acceptable salt thereof.

[00149] In certain aspects the present disclosure relates to methods to prevent, reduce or treat the incidence and/or severity of disorders or diseases associated with absence or lack of certain tissue cells. In one aspect the present disclosure relates to methods to prevent, reduce or treat the incidence and/or severity of inner ear disorders and hearing impairments involving inner ear tissue, particularly inner ear hair cells, their progenitors, and optionally, the stria vascularis, and associated auditory nerves. Of particular interest are those conditions that lead to permanent hearing loss where reduced number of hair cells may be responsible and/or decreased hair cell function. Also of interest are those arising as an unwanted side- effect of ototoxic therapeutic drugs including cisplatin and its analogs, aminoglycoside antibiotics, salicylate and its analogs, or loop diuretics. In certain embodiments, the present disclosure relates to inducing, promoting, or enhancing the growth, proliferation or regeneration of inner ear tissue, particularly inner ear supporting cells and hair cells.

[00150] Among other things, the methods presented here are useful for the preparation of pharmaceutical formulations for the prophylaxis and/or treatment of acute and chronic ear disease and hearing loss, dizziness and balance problems especially of sudden hearing loss, acoustic trauma, hearing loss due to chronic noise exposure, presbycusis, trauma during implantation of the inner ear prosthesis (insertion trauma), dizziness due to diseases of the inner ear area, dizziness related and/or as a symptom of Meniere's disease, vertigo related and/or as a symptom of Meniere's disease, tinnitus, and hearing loss due to antibiotics and cytostatics and other drugs.

[00151] When cochlea supporting cell populations are treated with the compound, whether the population is in vivo or in vitro, the treated supporting cells exhibit stem-like behavior in that the treated supporting cells have the capacity to proliferate and differentiate and, more specifically, differentiate into cochlear hair cells. Preferably, the composition induces and maintains the supporting cells to produce daughter stem cells that can divide for many generations and maintain the ability to have a high proportion of the resulting cells differentiate into hair cells. In certain embodiments, the proliferating stem cells express stem cell markers which may include Lgr5, Sox2, Opeml, Phex, lin28, Lgr6, cyclin Dl, Msxl, Myb, Kit, Gdnf3, Zic3, Dppa3, Dppa4, Dppa5, Nanog, Esrrb, Rexl, Dnmt3a, Dnmt3b, Dnmt31, Utfl, Tell, Oct4, Klf4, Pax6, Six2, Zicl, Zic2, Otx2, Bmil, CDX2, STAT3, Smadl, Smad2, smad2/3, smad4, smad5, and/or smad7.

[00152] In some embodiments, the method of the present disclosure may be used to maintain, or even transiently increase sternness (i.e., self-renewal) of a pre-existing supporting cell population prior to significant hair cell formation. In some embodiments, the pre-existing supporting cell population comprises inner pillar cells, outer pillar cells, inner phalangeal cells, Deiter cells, Hensen cells, Boettcher cells, and/or Claudius cells. Morphological analyses with immunostaining (including cell counts) and lineage tracing across a

Representative Microscopy Samples may be used to confirm expansion of one or more of these cell-types. In some embodiments, the pre-existing supporting cells comprise Lgr5 ⁺ cells. Morphological analyses with immunostaining (including cell counts) and qPCR and RNA hybridization may be used to confirm Lgr5 upregulation amongst the cell population.

[00153] Advantageously, the methods of the present disclosure achieve these goals without the use of genetic manipulation. Germ-line manipulation used in many academic studies is not a therapeutically desirable approach to treating hearing loss. In general, the therapy preferably involves the administration of a small molecule, peptide, antibody, or other non- nucleic acid molecule or nucleic acid delivery vector unaccompanied by gene therapy. In certain embodiments, the therapy involves the administration of a small organic molecule. Preferably, hearing protection or restoration is achieved through the use of a (non-genetic) therapeutic that is injected in the middle ear and diffuses into the cochlea. [00154] The cochlea relies heavily on all present cell types, and the organization of these cells is important to their function. As supporting cells play an important role in

neurotransmitter cycling and cochlear mechanics. Thus, maintaining a rosette patterning within the organ of Corti may be important for function. Cochlear mechanics of the basilar membrane activate hair cell transduction. Due to the high sensitivity of cochlear mechanics, it is also desirable to avoid masses of cells. In all, maintaining proper distribution and relation of hair cells and supporting cells along the basilar membrane, even after proliferation, is likely a desired feature for hearing as supporting cell function and proper mechanics is necessary for normal hearing.

[00155] In one embodiment of the present disclosure, the cell density of hair cells in a cochlear cell population is expanded in a manner that maintains, or even establishes, the rosette pattern characteristic of cochlear epithelia.

[00156] In accordance with one aspect of the present disclosure, the cell density of hair cells may be increased in a population of cochlear cells comprising both hair cells and supporting cells. The cochlear cell population may be an in vivo population (i.e., comprised by the cochlear epithelium of a subject) or the cochlear cell population may be an in vitro {ex vivo) population. If the population is an in vitro population, the increase in cell density may be determined by reference to a Representative Microscopy Sample of the population taken prior and subsequent to any treatment. If the population is an in vivo population, the increase in cell density may be determined indirectly by determining an effect upon the hearing of the subject with an increase in hair cell density correlating to an improvement in hearing.

[00157] In one embodiment, supporting cells placed in a Stem Cell Proliferation Assay in the absence of neuronal cells form ribbon synapses.

[00158] In a native cochlea, patterning of hair cells and supporting cells occurs in a manner parallel to the basilar membrane. In one embodiment of the present disclosure, the proliferation of supporting cells in a cochlear cell population is expanded in a manner that the basilar membrane characteristic of cochlear epithelia.

[00159] In one embodiment, the number of supporting cells in an initial cochlear cell population is selectively expanded by treating the initial cochlear cell population with a composition of the present disclosure (e.g. , a composition containing an Effective

Concentration of a Sternness Driver such as, e.g., a GSK3-alpha inhibitor and an Effective Concentration of a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor such as valproic acid) to form an intermediate cochlear cell population and wherein the ratio of supporting cells to hair cells in the intermediate cochlear cell population exceeds the ratio of supporting cells to hair cells in the initial cochlear cell population. The expanded cochlear cell population may be, for example, an in vivo population, an in vitro population or even an in vitro explant. In one such embodiment, the ratio of supporting cells to hair cells in the intermediate cochlear cell population exceeds the ratio of supporting cells to hair cells in the initial cochlear cell population. For example, in one such embodiment the ratio of supporting cells to hair cells in the intermediate cochlear cell population exceeds the ratio of supporting cells to hair cells in the initial cochlear cell population by a factor of 1.1. By way of further example, in one such embodiment the ratio of supporting cells to hair cells in the intermediate cochlear cell population exceeds the ratio of supporting cells to hair cells in the initial cochlear cell population by a factor of 1.5. By way of further example, in one such embodiment the ratio of supporting cells to hair cells in the intermediate cochlear cell population exceeds the ratio of supporting cells to hair cells in the initial cochlear cell population by a factor of 2. By way of further example, in one such embodiment the ratio of supporting cells to hair cells in the intermediate cochlear cell population exceeds the ratio of supporting cells to hair cells in the initial cochlear cell population by a factor of 3. In each of the foregoing embodiments, the capacity of a composition of the present disclosure to expand a cochlear cell population as described in this paragraph may be determined by means of a Stem Cell Proliferation Assay.

[00160] In one embodiment, the number of stem cells in a cochlear cell population is expanded to form an intermediate cochlear cell population by treating a cochlear cell population with a composition of the present disclosure (e.g. , a composition containing an Effective Concentration of a Sternness Driver such as, e.g., a GSK3-alpha inhibitor and an Effective Concentration of a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor such as valproic acid) wherein the cell density of stem cells in the intermediate cochlear cell population exceeds the cell density of stem cells in the initial cochlear cell population. The treated cochlear cell population may be, for example, an in vivo population, an in vitro population or even an in vitro explant. In one such embodiment, the cell density of stem cells in the treated cochlear cell population exceeds the cell density of stem cells in the initial cochlear cell population by a factor of at least 1.1. For example, in one such embodiment the cell density of stem cells in the treated cochlear cell population exceeds the cell density of stem cells in the initial cochlear cell population by a factor of at least 1.25. For example, in one such embodiment the cell density of stem cells in the treated cochlear cell population exceeds the cell density of stem cells in the initial cochlear cell population by a factor of at least 1.5. By way of further example, in one such embodiment the cell density of stem cells in the treated cochlear cell population exceeds the cell density of stem cells in the initial cochlear cell population by a factor of at least 2. By way of further example, in one such embodiment the cell density of stem cells in the treated cochlear cell population exceeds the cell density of stem cells in the initial cochlear cell population by a factor of at least 3. In vitro cochlear cell populations may expand significantly more than in vivo populations; for example, in certain embodiments the cell density of stem cells in an expanded in vitro population of stem cells may be at least 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000 or even 3000 times greater than the cell density of the stem cells in the initial cochlear cell population. In each of the foregoing embodiments, the capacity of a composition of the present disclosure to expand a cochlear cell population as described in this paragraph may be determined by means of a Stem Cell Proliferation Assay.

[00161] In accordance with one aspect of the present disclosure, a cochlea supporting cell population is treated with a composition of the present disclosure (e.g. , a composition containing an Effective Concentration of a Sternness Driver such as, e.g., a GSK3-alpha inhibitor and an Effective Concentration of a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor, e.g., valproic acid) to increase the Lgr5 activity of the population. For example, in one embodiment a GSK3 -alpha inhibitor has the capacity to increase and maintain the Lgr5 activity of an in vitro population of cochlea supporting cells by factor of at least 1.2. By way of further example, in one such embodiment the GSK3-alpha inhibitor has the capacity to increase the Lgr5 activity of an in vitro population of cochlea supporting cells by factor of 1.5. By way of further example, in one such embodiment the GSK3-alpha inhibitor has the capacity to increase the Lgr5 activity of an in vitro population of cochlea supporting cells by factor of 2, 3, 5 10, 100, 500, 1000, 2000 or even 3000. Increases in Lgr5 activity may also be observed for in vivo populations but the observed increase may be somewhat more modest. For example, in one embodiment the GSK3-alpha inhibitor has the capacity to increase the Lgr5 activity of an in vivo population of cochlea supporting cells by at least 5%. By way of further example, in one such embodiment the GSK3-alpha inhibitor has the capacity to increase the Lgr5 activity of an in vivo population of cochlea supporting cells by at least 10%. By way of further example, in one such embodiment the GSK3-alpha inhibitor has the capacity to increase the Lgr5 activity of an in vivo population of cochlea supporting cells by at least 20%. By way of further example, in one such embodiment the GSK3-alpha inhibitor has the capacity to increase the Lgr5 activity of an in vivo population of cochlea supporting cells by at least 30%. In each of the foregoing embodiments, the capacity of the GSK3-alpha inhibitor for such an increase in Lgr5 activity may be demonstrated, for example, in an In Vitro Lgr5 ⁺ Activity Assay and in an in vivo population may be demonstrated, for example, in an In Vivo Lgr5 ⁺ Activity Assay, as measured by isolating the organ and performing morphological analyses using immunostaining, endogenous fluorescent protein expression of Lgr5 (e.g., Lgr5, Sox2), and qPCR for Lgr5.

[00162] In addition to increasing the Lgr5 activity of the population, the number of Lgr5 ⁺ supporting cells in a cochlea cell population may be increased by treating a cochlea cell population containing Lgr5 ⁺ supporting cells (whether in vivo or in vitro) with a composition of the present disclosure (e.g., a composition containing an Effective Concentration of a Sternness Driver such as, e.g., a GSK3-alpha inhibitor and an Effective Concentration of a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor such as valproic acid). In general, the cell density of the stem/progenitor supporting cells may expand relative to the initial cell population via one or more of several mechanisms. For example, in one such embodiment, newly generated Lgr5 ⁺ supporting cells may be generated that have increased stem cell propensity (i.e., greater capacity to differentiate into hair cell). By way of further example, in one such embodiment no daughter Lgr5 ⁺ cells are generated by cell division, but pre-existing Lgr5 ⁺ supporting cells are induced to differentiate into hair cells. By way of further example, in one such embodiment no daughter cells are generated by cell division, but Lgr5 ^" supporting cells are activated to a greater level of Lgr5 activity and the activated supporting cells are then able to differentiate into hair cells. Regardless of the mechanism, in one embodiment a composition (e.g., a composition comprising a GSK3 -alpha inhibitor) of the present disclosure has the capacity to increase the cell density of Lgr5 ⁺ supporting cells in an in vitro isolated cell population of cochlea supporting cells by factor of at least 5. By way of further example, in one such embodiment the composition (e.g., a composition comprising a GSK3-alpha inhibitor) has the capacity to increase the cell density of Lgr5 ⁺ supporting cells in an in vitro population of cochlea supporting cells by factor of at least 10. By way of further example, in one such embodiment the composition (e.g., a composition comprising a GSK3-alpha inhibitor) has the capacity to increase the cell density of Lgr5 ⁺ supporting cells in an in vitro population of cochlea supporting cells by factor of at least 100, at least 500, at least 1000 or even at least 2000. Increases in the cell density of Lgr5 ⁺ supporting cells may also be observed for in vivo populations but the observed increase may be somewhat more modest. For example, in one embodiment the composition (e.g., a composition comprising a GSK3-alpha inhibitor) has the capacity to increase the cell density of Lgr5 ⁺ supporting cells in an in vivo population of cochlea supporting cells by at least 5%. By way of further example, in one such embodiment the composition (e.g., a composition comprising a GSK3- alpha inhibitor) has the capacity to increase the cell density of Lgr5 ⁺ supporting cells in an in vivo population of cochlea supporting cells by at least 10%. By way of further example, in one such embodiment the composition (e.g., a composition comprising a GSK3-alpha inhibitor) has the capacity to increase the cell density of Lgr5 ⁺ supporting cells in an in vivo population of cochlea supporting cells by at least 20%. By way of further example, in one such embodiment the composition (e.g., a composition comprising a GSK3-alpha inhibitor) has the capacity to increase the cell density of Lgr5 ⁺ supporting cells in an in vivo population of cochlea supporting cells by at least 30%. The capacity of the composition (e.g., a composition comprising a GSK3-alpha inhibitor) for such an increase in Lgr5 ⁺ supporting cells in an in vitro population may be demonstrated, for example, in a Stem Cell Proliferation Assay or in an appropriate in vivo assay. In one embodiment, a composition (e.g., a composition comprising a GSK3-alpha inhibitor) of the present disclosure has the capacity to increase the number of Lgr5 ⁺ cells in the cochlea by inducing expression of Lgr5 in cells with absent or low detection levels of the protein, while maintaining Native Morphology. In one embodiment, a composition (e.g., a composition comprising a GSK3-alpha inhibitor) of the present disclosure has the capacity to increase the number of Lgr5 ⁺ cells in the cochlea by inducing expression of Lgr5 in cells with absent or low detection levels of the protein, while maintaining Native Morphology and without producing Cell Aggregates.

[00163] In addition to increasing the cell density of Lgr5 ⁺ supporting cells, in one embodiment the method of the present disclosure has the capacity to increase the ratio of Lgr5 ⁺ cells to hair cells in a cochlear cell population. In one embodiment, the number of Lgr5 ⁺ supporting cells in an initial cochlear cell population is selectively expanded by treating the initial cochlear cell population with a composition of the present disclosure (e.g., a composition containing an Effective Concentration of a Sternness Driver such as, e.g., a GSK3-alpha inhibitor and an Effective Concentration of a Differentiation Inhibitor (e.g., a Notch agonist or an HDAC inhibitor such as valproic acid) to form an expanded cell population and wherein the number of Lgr5 ⁺ supporting cells in the expanded cochlear cell population at least equals the number of hair cells. The expanded cochlear cell population may be, for example, an in vivo population, an in vitro population or even an in vitro explant. In one such embodiment, the ratio of Lgr5 ⁺ supporting cells to hair cells in the expanded cochlear cell population is at least 1 : 1. For example, in one such embodiment the ratio of Lgr5 ⁺ supporting cells to hair cells in the expanded cochlear cell population is at least 1.5: 1. By way of further example, in one such embodiment the ratio of Lgr5 ⁺ supporting cells to hair cells in the expanded cochlear cell population is at least 2: 1. By way of further example, in one such embodiment the ratio of Lgr5 ⁺ supporting cells to hair cells in the expanded cochlear cell population is at least 3: 1. By way of further example, in one such embodiment the ratio of Lgr5 ⁺ supporting cells to hair cells in the expanded cochlear cell population is at least 4: 1. By way of further example, in one such embodiment the ratio of Lgr5 ⁺ supporting cells to hair cells in the expanded cochlear cell population is at least 5: 1. In each of the foregoing embodiments, the capacity of the composition (e.g., the composition comprising a GSK3-alpha inhibitor) of the present disclosure to expand a cochlear cell population as described in this paragraph may be determined by means of a Stem Cell Proliferation Assay.

[00164] In certain embodiments, the method increases the fraction of the Lgr5 ⁺ cells to total cells on the sensory epithelium by at least 10%, 20%, 50%, 100%, 250% 500%, 1000% or 5000%.

[00165] In certain embodiments, the method increases the Lgr5 ⁺ cells until they become at least 10, 20, 30, 50, 70, or 85 % of the cells on the sensory epithelium, e.g. the Organ of Corti.

[00166] In general, excessive proliferation of supporting cells in the cochlea is preferably avoided. In one embodiment, the method of the present disclosure has the capacity to expand a cochlear cell population without creating a protrusion of new cells beyond the native surface of the cochlea, e.g. a Cell Aggregate. In some embodiments, 30 days after placing a composition (e.g., a composition comprising a GSK3 -alpha inhibitor) on the round window membrane, the cochlear tissue has Native Morphology. In some embodiments, 30 days after placing the composition (e.g., the composition comprising a GSK3-alpha inhibitor) on the round window membrane, the cochlear tissue has Native Morphology and lacks Cell Aggregates. In some embodiments, 30 days after placing the composition (e.g., the composition comprising a GSK3-alpha inhibitor) on the round window membrane, the cochlear tissue has Native Morphology and at least 10, 20, 30, 50, 75, 90, 95, 98, or even at least 99% of the Lgr5 ⁺ cells in the Organ of Corti are not part of Cell Aggregates. [00167] In addition to expanding supporting cell populations, generally, and Lgr5 ⁺ supporting cells, specifically, as described above, the method of the present disclosure has the capacity to maintain, in the daughter cells, the capacity to differentiate into hair cells. In in vivo populations, the maintenance of this capacity may be indirectly observed by an improvement in a subject's hearing. In in vitro populations, the maintenance of this capacity may be directly observed by an increase in the number of hair cells relative to a starting population or indirectly by measuring LGR5 activity, SOX2 activity or one or more of the other stem cell markers identified elsewhere herein.

[00168] In one embodiment, the capacity of the method to increase the sternness of a population of cochlear supporting cells, in general, or a population of Lgr5 ⁺ supporting cells, in particular, may be correlated with an increase of Lgr5 activity of an in vitro population of isolated Lgr5 ⁺ cells as determined by an Lgr5 Activity Assay. As previously noted, in one such embodiment, the composition (e.g., the composition comprising a GSK3-alpha inhibitor) has the capacity to increase the Lgr5 activity of stem cells in the intermediate cell population by a factor of 5 on average relative to the Lgr5 activity of the cells in the initial cell population. By way of further example, in one such embodiment the method has the capacity to increase the Lgr5 activity of the stem cells genes in the intermediate cell population by a factor of 10 relative to the Lgr5 activity of the cells in the initial cell population. By way of further example, in one such embodiment the method has the capacity to increase the Lgr5 activity of the stem cells in the intermediate cell population by a factor of 100 relative to the Lgr5 activity of the cells in the initial cell population. By way of further example, in one such embodiment the method has the capacity to increase the Lgr5 activity of the stem cells in the intermediate cell population by a factor of 1000 relative to the Lgr5 activity of the cells in the initial cell population. In each of the foregoing embodiments, the increase in the activity of stem cells in the cell population may be determined in vitro by immunostaining or endogenous fluorescent protein expression for target genes and analysis of their relative intensities via imaging analysis or flow cytometry, or using qPCR for target stem cell genes. The identity of the resulting stem cell population may optionally be further determined by stem cell assays including stem cell marker expression assay, colony forming assay, self-renewal assay and differentiation assay as defined in Stem cell assay.

[00169] In some embodiments, the method applied to an adult mammal produces a population of adult mammalian Lgr5 ⁺ cells that are in S-phase. [00170] In one embodiment, after applying a GSK3-alpha inhibitor to the round window of a mouse, the in vivo Lgr5 ⁺ Activity of a cell population in the Organ of Corti increases 1.3x, 1.5x, up to 20x over baseline for a population that has not been exposed to the composition (e.g., the composition comprising a GSK3-alpha inhibitor). In some embodiments, applying the composition (e.g., the composition comprising a GSK3-alpha inhibitor) to the round window of a mouse increases the average In vivo Lgr5 ⁺ Activity for cells in the Organ of Corti is increased 1.3x, 1.5x, up to 20x over baseline for a population that has not been exposed to the composition (e.g., the composition comprising a GSK3-alpha inhibitor).

[00171] In certain embodiments, the method increases the Lgr5 ⁺ cells until they become at least 10%, 7.5%, 10%, up to 100% of the supporting cell population by number.

[00172] In some cases, a Sternness Driver may also induce differentiation of the supporting cells to hair cells if a Differentiation Inhibitor is not present at an Effective Differentiation Inhibition Concentration. Examples of Sternness Drivers that may drive both proliferation and differentiation include GSK3-alpha inhibitors such as, e.g., those disclosed in Table 1.

[00173] In some embodiments, a Sternness Driver may be used to drive the proliferation of Lgr5 ⁺ stem cells. In some cases, a Sternness Driver may also induce differentiation of Lgr5 ⁺ cells to hair cells if a Differentiation Inhibitor is not present at an Effective Differentiation Inhibition Concentration. Examples of Sternness Drivers that may drive both proliferation and differentiation include GSK3-alpha inhibitors such as, e.g., those disclosed in Table 1. In some embodiments, the Differentiation inhibitor is also a Sternness Driver. In some embodiments, the Differentiation inhibitor is Valproic Acid, which may be a Sternness Driver. In some embodiments, if a Differentiation Inhibitor is also a Sternness Driver, the concentration of the Differentiation Inhibitor is below the Effective Differentiation Inhibition Concentration during the Differentiation Period.

[00174] In certain embodiments, the composition (e.g., the composition comprising a GSK3- alpha inhibitor) has the capacity to increase the percentage of Lgr5 ⁺ cell in a cochlea by 5%, 10%, 25%, 50%, or 80%. In certain embodiments, the present disclosure provides a composition comprising a combination of (i) a GSK3-alpha inhibitor and (ii) valproic acid. In some embodiments, use of such a combination composition comprising (i) and (ii) above has the capacity to increase the percentage of Lgr5 ⁺ cell in a cochlea by 5%, 10%, 25%, 50%, or 80%. Sternness Drivers

[00175] Exemplary GSK3-alpha inhibitors within the present disclosure appear in Table 1. Pyrazolo- Compound 16 1597440-17-9 8 26 3.2 tetrahydroquinolinone

Pyrazolo- BRD1652 1597438-93-1 0.4 4 10 tetrahydroquinolinone

Urea AR-A014418 487021-52-3 28 116 4.1

CREB knockdown

ACS Chem. Biol. 2016, 11, 1952-1963

PLoS One (2016), 11(4), e0153075

[00176] In some embodiments, the GSK3-alpha inhibitor of the present disclosure comprises potency for GSK3-alpha that is less than InM. In some embodiments, the GSK3-alpha inhibitor of the present disclosure comprises potency for GSK3-alpha that is 1-10 nM. In some embodiments, the GSK3-alpha inhibitor of the present disclosure comprises potency for GSK3-alpha that is between 10 nM and 100 nM. In some embodiments, the GSK3-alpha inhibitor of the present disclosure comprises potency for GSK3 -alpha that is between 100 nM and 1000 nM.

[00177] In some embodiments the GSK3-alpha inhibitor is a pyrazolopyridine compound disclosed in Witherington, J. et.al., Bioorganic & Medicinal Chemistry Letters (2003), 13(18), 3055-3057; Witherington, J. et.al, Bioorganic & Medicinal Chemistry Letters (2003), 13(18), 3059-3062; or Witherington, J. et.al, Bioorganic & Medicinal Chemistry Letters (2003), 13(9), 1577-1580, each of which is incorporated herein by reference in its entirety.

[00178] In some embodiments the GSK3-alpha inhibitor is a pyrazolopyridazine compound disclosed in Witherington, J. et.al., Bioorganic & Medicinal Chemistry Letters (2003), 13(9), 1581-1584, incorporated herein by reference in its entirety.

[00179] Potency vs GSK3-alpha and GSK3-beta can be determined as described in the experimental procedures in the following references: Unoa, Y. et.al, Brain Research (2009), 1296, 148; Neumann, T. et.al, B. Journal of Medicinal Chemistry (2015), 58(22), 8907-8919, each of which is incorporated herein by reference in its entirety.

[00180] In some embodiments, compounds with a structure similar to potent GSK3-alpha inhibitors will show potent GSK-3-alpha inhibition as well. Accordingly, in some embodiments, the GSK3-alpha inhibitor is a pyrazoles that form a binding motif similar to GSK-3 beta XXII inhibitor CAS 1195901-31-5:

[00181] In some embodiments, the GSK3-alpha inhibitor comprises a structure:

[00182] In some embodiments, the GSK3-alpha inhibitor is a compound disclosed in Unoa, Y., Iwashitaa et.al., Brain Research (2009) 1296, 148; or Tsukamoto, T.; WO 2006085685

[00183] In some embodiments, the GSK3-alpha inhibitor is a compound disclosed in Wyatt, P.G. et.al., J. Med. Chem. 2008, 51, 4986-4999; WO2005002552A2, WO2005012256A1, WO2007129062A1, WO2007129066A1, WO2008001101A2, WO2008001115A2;

US20110002879 Al ; WO 2005002576 A2; WO 2006070192; WO2006077414 Al ;

WO2006077416; WO2006077419 WO2006077424; WO 2006077425 Al; WO 2006070198 Al WO 2006070195; WO 2006077426 A2; WO 2006003440 Al; WO 2007129062;

WO2006077428; WO 2006070202; WO 2008007113 A2; WO 2008007122 A2;

WO2008007123 A2; or WO 2008009954, each of which is incorporated herein by reference in its entirety.

[00184] In some embodiments, the GSK3-alpha inhibitor is a compound disclosed in Urich, R. et.al, Journal of Medicinal Chemistry (2014), 57(18), 7536-7549, incorporated herein by reference in its entirety.

[00185] In some embodiments, the GSK3-alpha inhibitor is a compound disclosed in CN102060772 or Lu, Y. et.al, Chemical Pharmaceutical Bulletin (2014), 62(3), 238-246, each of which is incorporated herein by reference in its entirety

[00186] In some embodiments, the GSK3-alpha inhibitor of the present disclosure inhibits both GSK3-alpha and GSK3-beta. In some embodiments, the GSK3-alpha inhibitor has potency against GSK3-alpha and GSK3-beta, wherein the potency is less than about 100 nM for inhibiting both GSK3 -alpha and GSK3-beta, or less than about 50 nM, 20 nM, 10 nM, 5 nM, 2 nM, or less than 1 nM for inhibiting both GSK3-alpha and GSK3-beta. [00187] In some embodiments, the GSK3-alpha inhibitor is selective for GSK3-alpha over GSK3-beta. In some embodiments, the GSK3-alpha inhibitor comprises a GSK3- alpha/GSK3-beta selectivity ratio that is at least about 0.5x, or at least about 0.6x, 0.7x, 0.8x, 0.9x, l .Ox, l . lx,1.2x, or 1.3x, 1.4x, 1.5x, 2x, 3x, 4x, 5x, 6x, 7x, 8x, 9x, lOx, 15x, 20x, 25x, 30x, 40x, 50x, 60x, 70x, 80x, 90x, or lOOx, including all integers (e.g., 61x, 62x, 63x) and ranges (e.g., from about lx to about lOOx; from about 20x to about 90x; from about 40x to about 60x) between of GSK3-alpha/GSK3-beta selectivity ratios.

[00188] In some embodiments, the GSK3-alpha inhibitor of the present disclosure comprises potency against GSK3-alpha and GSK3-beta, wherein the potencies against GSK3-alpha and GSK3-beta differ by about 100% or by about 50 %; about 25%; about 20%; or about 5%. In some embodiments, the GSK3-alpha inhibitor of the present disclosure comprises potency against GSK3-alpha and GSK3-beta, wherein the potencies against GSK3-alpha and GSK3- beta are not detectably different.

[00189] In some embodiments, the GSK3-alpha inhibitor is a compound with GSK3-alpha selectivity over GSK3-beta selected from (i) the oxadiazole compounds disclosed in Lo Monte, F. et.al, Journal of Medicinal Chemistry (2012), 55(9), 4407-4424; Neumann, T. et.al, Journal of Medicinal Chemistry (2015), 58(22), 8907-8919; (ii) the indole compounds disclosed in Georgievska, B. et.al, Journal of neurochemistry (2013), 125(3), 446-56; (iii) the isonicotinamide compounds disclosed in Luo, G. et.al, Journal of Medicinal Chemistry (2016), 59(3), 1041-1051 ; (iv) the maleimides compounds disclosed in Remsing Rix, L.L. et.al, ACS Chemical Biology (2014), 9(2), 353-358 or Bertrand, J. A. et.al., Journal of Molecular Biology (2003), 333(2), 393-407; (v) the diaminopyrimidine and azapurine compounds disclosed in Lum, C. et.al, Bioorganic & Medicinal Chemistry Letters (2008), 18(12), 3578-358; and (vi) the metal Complexes disclosed in Kramer, T.; Schmidt, B.; Lo Monte, F. International Journal of Alzheimer's Disease (2012), 381029, 32; Feng, L. et.al, Journal of the American Chemical Society (2011), 133(15), 5976-5986; Bregman, H. et.al, Journal of the American Chemical Society (2004), 126(42), 13594-13595; Atilla-Gokcumen, G. E.; Di Costanzo, L.; Meggers, E. JBIC, Journal of Biological Inorganic Chemistry (2011), 16(1), 45-50, each of which is incorporated herein by reference in its entirety.

[00190] In some embodiments, the GSK3-alpha inhibitor of the present disclosure does not comprise any detectable potency for inhibiting a cyclin-dependent kinase (CDK)(e.g., in vitro against a panel of CDKs such as CDKl, CDK2, CDK3, CDK4, CDK5, CDK6, CDK7, CDK9 using a standard radiometric in vitro kinase assay in which the ability of the CDKs to incorporate radioactive ATP into a known peptide substrate is tested in the presence of the inhibitor. In some embodiments, the GSK3 -alpha inhibitor of the present disclosure is selective for GSK3-alpha over CDK. In some embodiments, the GSK3-alpha inhibitor comprises a GSK3-alpha/CDK selectivity ratio that is at least about lOx, at least about 15x, at least about 20x, at least about 25x, at least about 30x, at least about 35x, at least about 40x, at least about 45x, at least about 50x, at least about 60x, at least about 60x, at least about 80x, at least about 90x, at least about lOOx, at least about 200x, at least about 500x, at least about lOOOx, or at least about 15,000x, including all integers (e.g., 81x, 82x, 83x) and ranges (e.g., from about lOx to about lOOOx; from about 200x to about 900x; from about 400x to about 600x) between of GSK3-alpha/CDK selectivity ratios.

[00191] In some embodiments, the GSK3-alpha inhibitor of the present disclosure does not comprise any detectable potency for inhibiting a Mitogen-activated protein kinase (MAPK) in vitro using a standard radiometric in vitro kinase assay in which the ability of the MAPK to incorporate radioactive ATP into a known peptide substrate is tested in the presence of the inhibitor. In some embodiments, the GSK3 -alpha inhibitor of the present disclosure is selective for GSK-alpha over MAPK. In some embodiments, the GSK3-alpha inhibitor comprises a GSK3-alpha/MAPK selectivity ratio that is at least about lOx, at least about 15x, at least about 20x, at least about 25x, at least about 30x, at least about 35x, at least about 40x, at least about 45x, at least about 50x, at least about 60x, at least about 60x, at least about 80x, at least about 90x, at least about lOOx, at least about 200x, at least about 500x, at least about lOOOx, or at least about 15,000x, including all integers (e.g., 81x, 82x, 83x) and ranges (e.g., from about lOx to about lOOOx; from about 200x to about 900x; from about 400x to about 600x) between of GSK3-alpha/MAPK selectivity ratios.

[00192] In some embodiments, the GSK3-alpha inhibitor of the present disclosure does not comprise any detectable potency for inhibiting a extracellular-signal -regulated kinases (ERK) in vitro using a standard radiometric in vitro kinase assay in which the ability of the ERK to incorporate radioactive ATP into a known peptide substrate is tested in the presence of the inhibitor. In some embodiments, the GSK3 -alpha inhibitor of the present disclosure is selective for GSK-alpha over ERK. In some embodiments, the GSK3 -alpha inhibitor comprises a GSK3-alpha/ERK selectivity ratio that is at least about lOx, at least about 15x, at least about 20x, at least about 25x, at least about 30x, at least about 35x, at least about 40x, at least about 45x, at least about 50x, at least about 60x, at least about 60x, at least about 80x, at least about 90x, at least about lOOx, at least about 200x, at least about 500x, at least about ΙΟΟΟχ, or at least about 15,000x, including all integers (e.g., 81x, 82x, 83x) and ranges (e.g., from about lOx to about lOOOx; from about 200x to about 900x; from about 400x to about 600x) between of GSK3-alpha/ERK selectivity ratios.

[00193] In some embodiments, the GSK3-alpha inhibitor of the present disclosure does not comprise any detectable potency for inhibiting a Mitogen-activated protein kinase kinase (MEK) in vitro using a standard radiometric in vitro kinase assay in which the ability of the MEK to incorporate radioactive ATP into a known peptide substrate is tested in the presence of the inhibitor. In some embodiments, the GSK3-alpha inhibitor of the present disclosure is selective for GSK-alpha over MEK. In some embodiments, the GSK3-alpha inhibitor comprises a GSK3-alpha/MEK selectivity ratio that is at least about lOx, at least about 15x, at least about 20x, at least about 25x, at least about 30x, at least about 35x, at least about 40x, at least about 45x, at least about 50x, at least about 60x, at least about 60x, at least about 80x, at least about 90x, at least about lOOx, at least about 200x, at least about 500x, at least about lOOOx, or at least about 15,000x, including all integers (e.g., 81x, 82x, 83x) and ranges (e.g., from about lOx to about lOOOx; from about 200x to about 900x; from about 400x to about 600x) between of GSK3-alpha/MEK selectivity ratios.

[00194] Classes of GSK3-alpha inhibitors for use in various embodiments of the

compositions and methods disclosed herein include but are not limited to those listed in Column A of Table 1. Specific GSK3-alpha inhibitors for use in various embodiments of the compositions and methods disclosed herein include but are not limited to those listed in Column B of Table 1.

Combinations of Agents

[00195] In certain embodiments, the composition comprises an agent within the classes of Table 1, Column A (or a derivative or pharmaceutically-acceptable salt thereof) and a Differentiation Inhibitor. In certain embodiments, the composition comprises an agent within the classes of Table 1, Column A (or a derivative or pharmaceutically-acceptable salt thereof) and an HDAC inhibitor (or a derivative or pharmaceutically-acceptable salt thereof) or a Notch agonist (or a derivative or pharmaceutically-acceptable salt thereof). In certain embodiments, the composition comprises an agent within the classes of Table 1, Column A (or a derivative or pharmaceutically-acceptable salt thereof) and valproic acid (or a derivative or analog or pharmaceutically-acceptable salt thereof). Delivery Profile of Combined Agents. [00196] Exemplary HDAC Inhibitors within the present disclosure appear in Table 4.

Table 4 - HDAC Inhibitors

Column A Column B CAS Number

Class Agent

Cyclic peptide Dihydrochlamydocin 52574-64-8

Epoxide (-)-Depudecin 139508-73-9

Epoxide Parthenolide 20554-84-1

Hydro xamate Trichostatin A (TSA)

Hydro xamate Trichostatin A (TSA) 58880-19-6

Hydro xamate SAHA (Zolinza, vonnostat) 149647-78-9

Hydro xamate 4-iodo-SAHA 1219807-87-0

Hydro xamate SBHA 38937-66-5

Hydro xamate CBHA 174664-65-4

Hydro xamate LAQ-824 591207-53-3

Hydro xamate PDX-101 (belinostat) 866323-14-0

Hydro xamate LBH-589 (panobinostat) 404950-80-7

Hydro xamate ITF2357 (Givinostat) 497833-27-9

Hydro xamate PCI-34051 950762-95-5

Hydro xamate PCI-24781 (Abexinostat) 783355-60-2

Hydro xamate Tubastatin A 1252003-15-8

Hydro xamate CUDC-101 1012054-59-9

Hydro xamate Oxamflatin 151720-43-3

Hydro xamate ITF2357 497833-27-9

Hydro xamate Bufexamac 2438-72-4

Hydro xamate APHA Compound 8 676599-90-9

Hydro xamate HDAC Inhibitor XXIV 854779-95-6

Hydro xamate Tubacin 537049-40-4

Hydro xamate Butyrylhydroxamic acid 4312-91-8

Hydro xamate MC 1568 852475-26-4

Hydro xamate SB 939 (Pracinostat) 929016-96-6

Hydro xamate 4SC-201 (Resminostat) 864814-88-0

Hydro xamate Tefinostat (CHR-2845) 914382-60-8

Hydro xamate CHR-3996 1256448-47-1

Hydro xamate NSC 57457 6953-61-3

Hydro xamate CG200745 936221-33-9

Hydro xamate ACY1215 1316214-52-4

Hydro xamate Nexturastat A 1403783-31-2

Hydro xamate Droxinostat 99873-43-5

Hydro xamate Scriptaid 287383-59-9

Hydro xamate BRD9757 1423058-85-8

Hydro xamate HPOB 1429651-50-2

Hydro xamate CAY10603 1045792-66-2

Hydro xamate HDAC6 Inhibitor III 1450618-49-1

Hydro xamate M 344 251456-60-7

Hydro xamate 4-(dimethylamino)-N-[6- 193551-00-7 Table 4 - HDAC Inhibitors

Column A Column B CAS Number

Class Agent

(hydroxy amino)-6-oxohexyl] - benzamide

Hydro xamate (S)-HDAC-42 935881-37-1

Hydro xamate HNHA 926908-04-5

Hydro xamate Pyroxamide 382180-17-8

Hydro xamate HDAC Inhibitor VI 926908-04-5

Hydro xamate HDAC Inhibitor II 174664-65-4

Hydro xamate LMK235 1418033-25-6

Hydro xamate HDAC-IN-1 1239610-44-6

Hydro xamate VAHA 106132-78-9

Ketone - CF3 Compound 6e 946500-31-8

Ketone - CF3 Compound 6H 946500-39-6

Ketone - CF3 Compound 27 946499-86-1

Ketone Compound 43 891259-76-0

Ketone - a-ketoamides 436150-82-2 436150-82-2

Polyketide Ratjadone A 163564-92-9

Silylalcohol 1587636-32-5 1587636-32-5

Sulphonyl Urea 960130-17-0 960130-17-0

Sulphonamide 1587636-33-6 1587636-33-6

Sulphonamide 329967-25-1 329967-25-1

Thiol 1428536-05-3 1428536-05-3

Thiol 908860-21-9 908860-21-9

Thiol 828920-13-4 828920-13-4

Thiol 1368806-68-1 1368806-68-1

Thiol 827036-76-0 827036-76-0

Thioester TCS HDAC6 20b 956154-63-5

Thioester PTACH 848354-66-5

Thioester KD 5170 940943-37-3

Thioester HDAC Inhibitor XXII 848354-66-5

Thioketone SIRT1/2 Inhibitor VII 143034-06-4

Tropones 46189-88-2 46189-88-2

Tropones 1411673-95-4 1411673-95-4

Non classical TMP269 1314890-29-3

Non classical Tasquinimod 254964-60-8

[00197] Exemplary Notch agonists within the present disclosure appear in Table 3.

Table 3 - Notch Agonists

Column A Column B CAS Number

Natural receptor Ligands Jagged 1 Protein Jagged 2 Protein

Delta-like 1 Protein

Delta-like 2 Protein

Delta-like 3 Protein

Delta-like 4 Protein

DSL peptide Protein

Delta 1 Protein

Delta D Protein

Receptor antibodies Notch 1 antibody Protein

Inhibition of Suppressor of

Deltex-mediated receptor

ubiquitination degradation

Downregulation of negative Notchless Protein

modulators of Notch activity

Numb Protein

Portion of Jag-1 residue 188-204 CDDYYYGFGCNKFCRPR Peptide

[00198] In some embodiments, a Sternness Driver may be used to drive the proliferation of Lgr5 ⁺ stem cells. In some cases, a Sternness Driver may also induce differentiation of LGR5+ cells to hair cells if a Differentiation Inhibitor is not present at an Effective

Differentiation Inhibition Concentration. One example of Sternness Drivers that may drive both proliferation and differentiation includes GSK3-alpha inhibitors. In some embodiments, the Differentiation Inhibitor may be an HDAC inhibitor (or a derivative or pharmaceutically - acceptable salt thereof) or a Notch agonist (or a derivative or pharmaceutically-acceptable salt thereof). In some embodiments, the Differentiation Inhibitor is valproic acid (or a derivative or pharmaceutically-acceptable salt thereof). In certain embodiments, the stem cell population is of an in vivo subject, and the method is a treatment for hearing loss and/or vestibular dysfunction (e.g., wherein the generation of inner ear hair cells from the expanded population of stem cells results in partial or full recovery of hearing loss and/or improved vestibular function). In certain embodiments, the stem cell population is of an in vivo subject, and the method further comprises delivering a drug to the subject (e.g., for treatment of a disease and/or disorder unrelated to hearing loss and/or vestibular dysfunction) at a higher concentration than a known safe maximum dosage of the drug for the subject (e.g. , the known safe maximum dosage if delivered in the absence of the generation of inner ear hair cells resulting from the method) (e.g., due to a reduction or elimination of a dose-limiting ototoxicity of the drug). [00199] In certain embodiments, the method further comprises performing high throughput screening using the generated inner ear hair cells. In certain embodiments, the method comprises using the generated inner ear hair cells to screen molecules for toxicity against inner ear hair cells. In certain embodiments, the method comprises using the generated inner ear hair cells to screen molecules for ability to improve survival of inner ear hair cells (e.g., inner ear hair cells exposed to said molecules).

[00200] In some aspects, the disclosure is directed to a method of producing an expanded population of stem cells, the method comprising: administering or causing to be administered to a stem cell population (e.g., of an in vitro, ex vivo, or in vivo sample/subject) a GSK3-alpha inhibitor (e.g., a GSK3-alpha inhibitor disclosed in Table 1), optionally in combination with a Differentiation Inhibitor. In some embodiments, the Differentiation Inhibitor is an HDAC inhibitor or a Notch agonist. In some embodiments, the Differentiation Inhibitor is valproic acid.

[00201] In certain embodiments, the administering step is carried out by performing one or more injections into the ear (e.g., transtympanically into the middle ear and/or inner ear).

[00202] In certain embodiments, the administering step comprises administering the GSK3- alpha inhibitor in a sustained manner. In some embodiments, the administering step further comprises administering a Differentiation Inhibitor in combination with the GSK3-alpha inhibitor. In some embodiments, the GSK3 -alpha inhibitor and the Differentiation Inhibitor are administered as a single combination composition. In some embodiments the GSK3- alpha inhibitor and the Differentiation Inhibitor are administered sequentially, as separate compositions.

[00203] In certain embodiments, the administering step comprises administering the GSK3- alpha inhibitor in a sustained manner, wherein the administering step further comprises administering an HDAC inhibitor or a Notch agonist in combination with the GSK3-alpha inhibitor. In some embodiments, the GSK3 -alpha inhibitor and the HDAC inhibitor or Notch agonist are administered as a single combination composition. In some embodiments the GSK3-alpha inhibitor and the HDAC inhibitor or Notch agonist are administered

sequentially, as separate compositions.

[00204] In certain embodiments, the administering step comprises administering the GSK3- alpha inhibitor in a sustained manner, wherein the administering step further comprises administering valproic acid in combination with the GSK3-alpha inhibitor. In some embodiments, the GSK3-alpha inhibitor and the valproic acid are administered as a single combination composition. In some embodiments the GSK3 -alpha inhibitor and the valproic acid are administered sequentially, as separate compositions.

[00205] In certain embodiments, the stem cells are inner ear stem cells and/or supporting cells.

[00206] In certain embodiments, the method further comprises performing high throughput screening using the generated expanded population of stem cells. In certain embodiments, the method further comprises using the generated stem cells to screen molecules for toxicity against stem cells and/or their progeny. In certain embodiments, the method comprises using the generated stem cells to screen molecules for ability to improve survival of stem cells and/or their progeny.

[00207] In some aspects, the disclosure is directed to a method of treating a subject who has, or is at risk of developing, hearing loss and/or vestibular dysfunction, the method comprising: identifying a subject who has experienced, or is at risk for developing, hearing loss and/or vestibular dysfunction, administering or causing to be administered a GSK3-alpha inhibitor and optionally a Differentiation Inhibitor. In some embodiments, the Differentiation

Inhibitor is an HDAC inhibitor or a Notch agonist. In some embodiments, the Differentiation inhibitor is valproic acid.

[00208] In certain embodiments, the stem cell population comprises Lgr5 ⁺ cells. In certain embodiments, the stem cell population comprises post-natal cells. In certain embodiments, the stem cell population comprises epithelial stem cells. In certain embodiments, stem cells include progenitor cells.

[00209] In certain embodiments, the administering step comprises administering or causing to be administered to the subject VPA (e.g., in a pharmaceutically-acceptable form (e.g., salt)). In certain embodiments, the step of administering is carried out by performing one or more injections into the ear (e.g., transtympanically into the middle ear and/or inner ear).

[00210] In some aspects, the disclosure is directed to a method of generating inner ear hair cells, the method comprising: proliferating stem cells in an initial stem cell population (e.g., of an in vitro, ex vivo, or in vivo sample/subject), resulting in an expanded population of stem cells (e.g., such that the expanded population is a factor of at least 1.25, 1.5, 1.75, 2, 3, 5, 10, or 20 greater than the initial stem cell population); and facilitating generation of inner ear hair cells from the expanded population of stem cells. [00211] In some aspects, the disclosure is directed to a method of generating inner ear hair cells, the method comprising administering a GSK3-alpha inhibitor (e.g., in a

pharmaceutically-acceptable form (e.g., salt)) to a cell population in an inner ear of a subject, thereby facilitating generation of inner ear hair cells.

[00212] In some aspects, the disclosure is directed to a method of generating inner ear hair cells, the method comprising: proliferating post-natal LGR5+ cells in an initial population (e.g., of an in vitro, ex vivo, or in vivo sample/subject), resulting in an expanded population of LGR5+ cells (e.g., such that the expanded population is a factor of at least 1.25, 1.5, 1.75, 2, 3, 5, 10, or 20 greater than the initial stem cell population), said expanded population of LGR5+ cells resulting in generation of inner ear hair cells. In certain embodiments, stem cells include progenitor cells.

[00213] In some aspects, the disclosure is directed to a method of treating a disease or disorder, the method comprising: proliferating post-natal Lgr5 ⁺ epithelial cells in an initial population of a subject (in vivo), resulting in an expanded population of Lgr5+ epithelial cells (e.g., such that the expanded population is a factor of at least 1.25, 1.5, 1.75, 2, 3, 5, 10, or 20 greater than the initial post-natal Lgr5 ⁺ epithelial cell population).

[00214] In some embodiments, Lgr5 ⁺ cells are differentiated into hair cells.

Compositions and Administration

[00215] Certain embodiments relate to pharmaceutical, prophylactic, or therapeutic compositions, comprising a pharmaceutically-acceptable carrier and a stem cell proliferator that is a GSK3-alpha inhibitor, or a pharmaceutically-acceptable salt thereof. In some embodiments, as noted above, a composition is adapted for administration to the inner ear and/or middle ear, for example, local administration to the round window membrane or intratympanic or transtympanic administration, for example, to cochlear tissue.

[00216] The phrase "pharmaceutically-acceptable" is employed herein to refer to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio.

[00217] As used herein "pharmaceutically-acceptable carrier, diluent or excipient" includes without limitation any adjuvant, carrier, excipient, glidant, sweetening agent, diluent, preservative, dye/colorant, flavor enhancer, surfactant, wetting agent, dispersing agent, suspending agent, stabilizer, isotonic agent, solvent, surfactant, or emulsifier which has been approved by the United States Food and Drug Administration as being acceptable for use in humans or domestic animals. Exemplary pharmaceutically-acceptable carriers include, but are not limited to, to sugars, such as lactose, glucose and sucrose; starches, such as corn starch and potato starch; cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; tragacanth; malt; gelatin; talc; cocoa butter, waxes, animal and vegetable fats, paraffins, silicones, bentonites, silicic acid, zinc oxide; oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; glycols, such as propylene glycol; polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; esters, such as ethyl oleate and ethyl laurate; agar; buffering agents, such as magnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen- free water; isotonic saline; Ringer's solution; ethyl alcohol; phosphate buffer solutions; and any other compatible substances employed in pharmaceutical formulations.

[00218] Certain compositions comprise at least one biocompatible matrix. The term

"biocompatible matrix" as used herein is a polymeric carrier that is acceptable for administration to humans for the release of therapeutic agents. In some instances, a biocompatible matrix may be a biocompatible gel or foam.

[00219] Certain compositions comprise at least on poloxamer. Poloxamers are triblock copolymers formed of (i.e., hydrophilic poly (oxy ethylene) blocks and hydrophobic poly(oxypropylene) blocks) configured as a triblock of poly(oxyethylene)- poly(oxypropylene)-poly(oxy ethylene). Poloxamers are one class of block copolymer surfactants having a propylene oxide block hydrophobe and an ethylene oxide hydrophile. Poloxamers are commercially available (e.g., Pluronic® polyols are available from BASF Corporation). Alternatively, poloxamers can be synthesized by known techniques.

[00220] Exemplary poloxamers include Poloxamer 124, Poloxamer 188, Poloxamer 237, Poloxamer 338, and Poloxamer 407. In some embodiments, the poloxamer comprises mixtures of two or more of Poloxamer 124, Poloxamer 188, Poloxamer 237, Poloxamer 338 or Poloxamer 407. In some embodiments, the mixture of two or more poloxamers comprise Poloxamer 407 and Poloxamer 124. In certain embodiments the poloxamer comprises at least one of Poloxamer 188 and Poloxamer 407 or mixtures thereof. In some embodiments, the poloxamer is Poloxamer 407. [00221] In some embodiments, the poloxamer is in a concentration between about 5 wt% and about 25 wt% relative to the composition, or about 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 1 1 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, or 25 wt% relative to the composition. In certain embodiments, the poloxamer is in a concentration between about 10 wt% and about 23 wt% relative to the composition. In some embodiments the poloxamer is in a concentration between about 15 wt% and about 20 wt% relative to the composition. In particular embodiments, the poloxamer is in a concentration is approximately 17 wt% relative to the composition.

[00222] In some embodiments, wetting agents, emulsifiers and lubricants, such as sodium lauryl sulfate and magnesium stearate, as well as coloring agents, release agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the compositions.

[00223] Certain compositions comprise at least one antioxidant. Examples of

pharmaceutically-acceptable antioxidants include: (1) water soluble antioxidants, such as ascorbic acid, cysteine hydrochloride, sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2) oil-soluble antioxidants, such as ascorbyl palmitate, butylated

hydroxyanisole (BHA), butylated hydroxy toluene (BHT), lecithin, propyl gallate, alpha- tocopherol, and the like; and (3) metal chelating agents, such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol, tartaric acid, phosphoric acid, and the like.

[00224] In specific embodiments, the viscosity of the composition at about body temperature is substantially different (e.g., lesser, greater) than the viscosity of the composition at room temperature.

[00225] In some embodiments, the composition comprises a buffer. For example, in certain instances, the buffer is physiological saline or phosphate-buffered saline (PBS).

[00226] In some embodiments, the composition is at or near physiological pH. For instance, in some embodiments, the composition has a pH of between about 6 and about 8, including all integers, decimals, and ranges in between, for example, about 6 to about 6.5 to about 7 to about 7.5 to about 8. In specific embodiments, the composition has a pH of about 7.4 (±0.2).

[00227] In certain embodiments, the GSK3 -alpha inhibitor is present in a pharmaceutical composition at an effective or otherwise defined concentration or concentration range. For example, in certain embodiments, the GSK3-alpha inhibitor is present in a composition at a concentration of about 0.01 uM to 1000 mM, about 0.1 uM to 1000 mM, about 1 uM to 100 mM, about 10 uM to 10 mM, about 1 uM to 10 uM, about 10 uM to 100 uM, about 100 uM to 1000 uM, about 1 mM to 10 mM, or about 10 mM to 100 mM; or at a concentration ratio of about 0.01 to 1,000,000 fold relative to its effective activity in an in vitro activity assay, or about 0.1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 5000 fold relative to its effective activity in an in vitro activity assay, or about 50 to 2000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay, or at about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 0.01 nM to 1000 uM, about 0.1 nM to 1000 uM, about 1 nM to 100 uM, about 10 nM to 10 uM, about 1 nM to 10 nM, about 10 nM to 100 nM, about 100 nM to 1000 nM, about 1 uM to 10 uM, or about 10 uM to 100 uM, including all integers and ranges in between. In some embodiments, the effective activity is measured in an Lgr5 proliferation assay, as described herein.

[00228] In some embodiments, the GSK3-alpha inhibitor is GSK3 inhibitor XXII, which is in a composition at a concentration of about 0.1 uM to 1000 mM, about 1 uM to 100 mM, 10 uM to 10 mM, about 100 uM to 10 mM, or 100 uM to 1 mM, or about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mM; or at a concentration ratio of about 0.1 to 1,000,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 10 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay, or about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 0.1 nM to 1000 uM, about 1 nM to 100 uM, about 10 nM to 10 uM, about 100 nM to 1 uM, or about 0.5 uM, including all integers and ranges in between. In some embodiments, the effective activity is measured in an Lgr5 proliferation assay, as described herein.

[00229] In particular embodiments, the GSK3-alpha inhibitor is AZD1080, which is at a concentration of about 0.1 uM to 1000 mM, about 1 uM to 1000 mM, about 10 uM to 100 mM, about 100 uM to 10 mM, about 1 mM to 10 mM, or about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mM; or at a concentration ratio of about 0.1 to 1,000,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or aboutlO to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay, or about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 1 nM to 1000 uM, about 10 nM to 1000 uM, about 100 nM to 100 uM, about 1 uM to 10 uM, or about 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10 uM, including all integers and ranges in between. In some embodiments, the effective activity is measured in an Lgr5 proliferation assay, as described herein.

[00230] In certain embodiments, the HDAC inhibitor is present in a pharmaceutical composition at an effective or otherwise defined concentration or concentration range. For example, in certain embodiments, the HDAC inhibitor is present in a composition at a concentration of about 0.01 uM to 100,000 mM, about 1 uM to 10,000 mM, about 10 uM to 10,000 mM, about 100 uM to 1000 mM, about 1 uM to 10 uM, about 10 uM to 100 uM, about 100 uM to 1000 uM, about 1000 uM to 10 mM, about 10 mM to 100 mM, about 100 mM to 1000 mM, or about 1000 mM to 10,000 mM; or at a concentration ratio of about 0.1 to 1,000,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 10 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay; or about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 0.01 nM to 100,000 uM, about 1 nM to 10,000 uM, about 10 nM to 10,000 uM, about 100 nM to 1000 uM, about 1 nM to 10 nM, about 10 nM to 100 nM, about 100 nM to 1000 nM, about 1 uM to 10 uM, about 10 uM to 100 uM, about 100 uM to 1000 uM, or about 1000 uM to 10,000 uM, including all integers and ranges in between. In some embodiments, the effective activity is measured in an Lgr5 proliferation assay, as described herein.

[00231] In some embodiments, the HDAC inhibitor is valproic acid, which is at a

concentration of about 10 uM to 100,000 mM, about 1 mM to 10,000 mM, about 10 mM to 10,000 mM, about 100 mM to 10,000 mM, about 200 mM to 2000 mM, about 1000 mM, or about 600 mM; or at a concentration ratio of about 0.1 to 1 ,000,000 fold relative to its effective activity in an in vitro activity assay, or about 1 to 100,000 fold relative to its effective activity in an in vitro activity assay, or about 10 to 10,000 fold relative to its effective activity in an in vitro activity assay, or about 100 to 1000 fold relative to its effective activity in an in vitro activity assay, or about 1000 fold relative to its effective activity in an in vitro activity assay; or at a concentration of about 10 nM to 100,000 uM, 1 uM to 10,000 uM, about 10 uM to 10,000 uM, about 100 uM to 10,000 uM, about 200 uM to 2000 uM, or about 1000 uM, including all integers and ranges in between. In some embodiments, the effective activity is measured in an Lgr5 proliferation assay, as described herein..

[00232] Compounds or compositions described herein can be formulated in any manner suitable for a desired delivery route, e.g., transtympanic injection, transtympanic wicks and catheters, cochlear implants, and injectable depots. In some instances, compositions or formulations include one or more physiologically-acceptable components, including derivatives or prodrugs, solvates, stereoisomers, racemates, or tautomers thereof with any physiologically acceptable carriers, diluents, and/or excipients.

[00233] As noted above, certain compositions are adapted for, and certain methods employ, administration to the middle ear or inner ear, for example, by local administration to the round window membrane. The membrane of the round window is the biological barrier to the inner ear space and represents the major obstacle for the local treatment of hearing impairment. The administered drug must overcome this membrane to reach the inner ear space. The drug can operatively (e.g., injection through the tympanic membrane) be placed locally to the round window membrane and can then penetrate through the round window membrane. Substances that penetrate the round window typically distribute in the perilymph and thus reach the hair cells and supporting cells.

[00234] The pharmaceutical compositions or formulations may also contain a membrane penetration enhancer, which supports the passage of the agents mentioned herein through the round window membrane. Accordingly, liquid, gel or foam formulations may be used. It is also possible to apply the active ingredient orally or to employ a combination of delivery approaches.

[00235] Certain compositions are adapted for, and certain methods employ, administration to the middle ear or inner ear, for example, by intratympanic or transtympanic administration. Intratympanic (IT) delivery of drugs to the ear is increasingly used for both clinical and research purposes. Some groups have applied drugs in a sustained manner using

microcatheters and micro wicks, while the majority have applied them as single or as repeated IT injections (up to 8 injections over periods of up to 2 weeks).

[00236] Intratympanically applied drugs are thought to enter the fluids of the inner ear primarily by crossing the round window (RW) membrane. Calculations show that a major factor controlling both the amount of drug entering the ear and the distribution of drug along the length of the ear is the duration the drug remains in the middle ear space. Single, One- shot' applications or applications of aqueous solutions for few hours' duration result in steep drug gradients for the applied substance along the length of the cochlea and rapidly declining concentration in the basal turn of the cochlea as the drug subsequently becomes distributed throughout the ear.

[00237] Other injection approaches include by osmotic pump, or, by combination with implanted biomaterial, and more preferably, by injection or infusion. Biomaterials that can aid in controlling release kinetics and distribution of drug include hydrogel materials, degradable materials. One class of materials that is most preferably used includes in situ gelling materials. All potential materials and methodologies mentioned in references (Almeida H, Amaral MH, Lobao P, Lobo JM, Drug Discov Today 2014;19:400-12; Wise AK, Gillespie LN, J Neural Eng 2012;9:065002; Surovtseva EV, Johnston AH, Zhang W, et al, Int J Pharmaceut 2012; 424: 121-7; Roy S, Glueckert R, Johnston AH, et al,

Nanomedicine 2012; 7:55-63; Rivera T, Sanz L, Camarero G, Varela-Nieto I,. Curr Drug Deliv 2012;9:231-42; Pararas EE, Borkholder DA, Borenstein JT, Adv Drug Deliv Rev 2012; 64: 1650-60; Li ML, Lee LC, Cheng YR, et al, IEEE TBio-MedEng 2013; 60:2450-60; Lajud SA, Han Z, Chi FL, et al, J Control Release 2013;166:268-76; Kim DK, Park SN, Park KH, et al., Drug Deliv 2014; Engleder E, Honeder C, Klobasa J, Wirth M, Amoldner C, Gabor F, Int J Pharmaceut 2014;471 :297-302; Bohl A, Rohm HW, Ceschi P, et al, J Mater Sci Mater Med 2012;23:2151-62; Hoskison E, Daniel M, Al-Zahid S, Shakesheff KM, Bayston R, Birchall JP, Ther Deliv 2013;4: 115-24; Staecker H, Rodgers B, Expert Opin Drug Deliv 2013;10:639-50; Pritz CO, Dudas J, Rask-Andersen H, Schrott-Fischer A, Glueckert R, Nanomedicine 2013;8: 1155-72), which are included herein by reference in their entirety. Other materials include collagen or other natural materials including fibrin, gelatin, and decelluarized tissues. Gelfoam may also be suitable.

[00238] Delivery may also be enhanced via alternate means including but not limited to agents added to the delivered composition such as penetration enhancers, or could be through devices via ultrasound, electroporation, or high speed jet.

[00239] Methods described herein can also be used for inner ear cell types that may be produced using a variety of methods know to those skilled in the art including those cell types described in PCT Application No. WO2012103012 Al.

[00240] With regard to human and veterinary treatment, the amount of a particular agent(s) that is administered may be dependent on a variety of factors, including the disorder being treated and the severity of the disorder; activity of the specific agent(s) employed; the age, body weight, general health, sex and diet of the patient; the time of administration, route of administration, and rate of excretion of the specific agent(s) employed; the duration of the treatment; drugs used in combination or coincidental with the specific agent(s) employed; the judgment of the prescribing physician or veterinarian; and like factors known in the medical and veterinary arts.

[00241] The agents described herein may be administered in a therapeutically effective amount to a subject in need of treatment. Administration of compositions (e.g., compositions comprising one or more GSK3-alpha inhibitor and optionally a Differentiation Inhibitor (e.g., (e.g., a Notch agonist or an HDAC inhibitor, e.g., valproic acid) described herein can be via any of suitable route of administration, for example, by intratympanic administration. Other routes include ingestion, or alternatively parenterally, for example intravenously, intra- arterially, intraperitoneally, intrathecally, intraventricularly, intraurethrally, intrasternally, intracranially, intramuscularly, intranasally, subcutaneously, sublingually, transdermally, or by inhalation or insufflations, or topical by ear instillation for absorption through the skin of the ear canal and membranes of the eardrum. Such administration may be as a single or multiple oral dose, defined number of ear drops, or a bolus injection, multiple injections, or as a short- or long-duration infusion. Implantable devices (e.g., implantable infusion pumps) may also be employed for the periodic parenteral delivery over time of equivalent or varying dosages of the particular formulation. For such parenteral administration, the compounds are preferably formulated as a sterile solution in water or another suitable solvent or mixture of solvents. The solution may contain other substances such as salts, sugars (particularly glucose or mannitol), to make the solution isotonic with blood, buffering agents such as acetic, citric, and/or phosphoric acids and their sodium salts, and preservatives.

[00242] Compositions described herein can be administered by a number of methods sufficient to deliver the composition to the inner ear. Delivering a composition to the inner ear includes administering the composition to the middle ear, such that the composition may diffuse across the round window to the inner ear. It also includes administering a composition to the inner ear by direct injection through the round window membrane. Such methods include, but are not limited to auricular administration, by transtympanic wicks or catheters, or parenteral administration, for example, by intraauricular, transtympanic, or intracochlear injection. [00243] In particular embodiments, the compounds, compositions and formulations of the disclosure are locally administered, meaning that they are not administered systemically.

[00244] In one embodiment, a syringe and needle apparatus is used to administer compounds or compositions to a subj ect using auricular administration. A suitably sized needle is used to pierce the tympanic membrane and a wick or catheter comprising the composition is inserted through the pierced tympanic membrane and into the middle ear of the subject. The device may be inserted such that it is in contact with the round window or immediately adjacent to the round window. Exemplary devices used for auricular administration include, but are not limited to, transtympanic wicks, transtympanic catheters, round window microcatheters (small catheters that deliver medicine to the round window), and Silverstein Microwicks™ (small tube with a "wick" through the tube to the round window, allowing regulation by subject or medical professional).

[00245] In some embodiments, a syringe and needle apparatus is used to administer compounds or compositions to a subj ect using transtympanic injection, injection behind the tympanic membrane into the middle and/or inner ear. The formulation may be administered directly onto the round window membrane via transtympanic injection or may be administered directly to the cochlea via intracochlear injection or directly to the vestibular organs via intravestibular injection.

[00246] In some embodiments, the delivery device is an apparatus designed for

administration of compounds or compositions to the middle and/or inner ear. By way of example only: GYRUS Medical GmbH offers micro-otoscopes for visualization of and drug delivery to the round window niche; Arenberg has described a medical treatment device to deliver fluids to inner ear structures in U. S. Pat. Nos. 5,421,818; 5,474,529; and 5,476,446, each of which is incorporated by reference herein for such disclosure. U. S. patent application Ser. No. 08/874,208, which is incorporated herein by reference for such disclosure, describes a surgical method for implanting a fluid transfer conduit to deliver compositions to the inner ear. U. S. Patent Application Publication 2007/0167918, which is incorporated herein by reference for such disclosure, further describes a combined otic aspirator and medication dispenser for transtympanic fluid sampling and medicament application.

[00247] In some embodiments, a compound or composition disclosed herein is administered to a subject in need thereof once. In some embodiments, a compound or composition disclosed herein is administered to a subject in need thereof more than once. In some embodiments, a first administration of a compound or composition disclosed herein is followed by a second, third, fourth, or fifth administration of a compound or composition disclosed herein.

[00248] The number of times a compound or composition is administered to an subject in need thereof depends on the discretion of a medical professional, the disorder, the severity of the disorder, and the subject's response to the formulation. In some embodiments, the compound or composition disclosed herein is administered once to a subject in need thereof with a mild acute condition. In some embodiments, a compound or composition disclosed herein is administered more than once to a subject in need thereof with a moderate or severe acute condition. In the case wherein the subject's condition does not improve, upon the doctor's discretion the compound or composition may be administered chronically, that is, for an extended period of time, including throughout the duration of the subject's life in order to ameliorate or otherwise control or limit the symptoms of the subject's disease or condition.

[00249] In the case wherein the subject's status does improve, upon the doctor's discretion the compound or composition may administered continuously; alternatively, the dose of drug being administered may be temporarily reduced or temporarily suspended for a certain length of time (i.e., a "drug holiday"). The length of the drug holiday varies between 2 days and 1 year, including by way of example only, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 10 days, 12 days, 15 days, 20 days, 28 days, 35 days, 50 days, 70 days, 100 days, 120 days, 150 days, 180 days, 200 days, 250 days, 280 days, 300 days, 320 days, 350 days, and 365 days. The dose reduction during a drug holiday may be from 10%- 100%, including by way of example only 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%.

[00250] Once the subject's hearing and/or balance has improved, a maintenance dose can be administered, if necessary. Subsequently, the dosage or the frequency of administration, or both, is optionally reduced, as a function of the symptoms, to a level at which the improved disease, disorder or condition is retained. In certain embodiments, subjects require intermittent treatment on a long-term basis upon any recurrence of symptoms.

EXAMPLES

Assay: Mouse Strains

[00251] Lgr5-EGFP-IRES-Cre-ER mice (Barker et al, 2007)

(http://jaxmice.jax.org/strain/008875.html) were used to analyze the effects of small molecules on cochlear stem cell expansion. Atohl-nGFP mice (Lumpkin et al, 2003) (provided by Dr. Jane Johnson) were used to identify differentiated hair cells.

[00252] Isolation of stem cells from the inner ear: All animal studies were conducted under an approved institutional protocol according to National Institutes of Health guidelines. For experiments with neonatal mice (postnatal days 1-3), the cochleae were dissected in HBSS and the organ of Corti was separated from the stria vascularis and the modiolus. The organs of Corti were then treated with Cell Recovery Solution (Corning) for 1 h to separate cochlear epithelium from the underlying mesenchyme. Epithelia were then collected and treated with TrypLE (Life Technologies) for 15-20 minutes at 37 ^° C. Single cells obtained by mechanical trituration were filtered (40 μιτι) and suspended in Matrigel (Corning) for 3D culture.

Expansion of Lgr5-Positive Cells

[00253] Cells were cultured in a 1 : 1 mixture of DMEM and F12, supplemented with Glutamax (GIBCO), N2, B27 (Invitrogen), EGF (50 ng/mL; Chemicon), bFGF (50 ng/mL; Chemicon), IGF1 (50 ng/mL; Chemicon) and a GSK3-alpha inhibitor. Media were changed every other day.

[00254] Differentiation of Lgr5 -Positive Progenitor Cells Stem cell colonies were differentiated in a 1 : 1 mixture of DMEM and F12, supplemented with Glutamax (GIBCO), N2, B27 (Invitrogen), with the addition of molecules that drive differentiation, or after removal of growth factors without the addition of molecules that drive differentiation. Small molecules were added to the culture to test their effect on differentiation. The optimal differentiation conditions were achieved with 3 μΜ of a GSK3-alpha inhibitor.

Analysis

[00255] Lgr5-positive cells were quantified after 10 days (D10) in culture in multiple conditions. Cell colonies were dissociated into single cells using TrypLE (Gibco). The cells were then stained with propidium iodide (PI) and analyzed using a flow cytometer for Lgr5- GFP expression. The number of GFP-positive cells and the percentage of GFP-positive cells were quantified.

[00256] Atohl-nGFP-positive cells were quantified at day 0 (DO) and day 10 (D 10) of differentiation treatment to determine the number of hair cells that had differentiated. Cell colonies were incubated in Cell Recovery Solution to release the colonies from Matrigel and dissociated into single cells using TrypLE. The total number and percentage of GFP-positive cells were quantified using a flow cytometer for multiple culture conditions. ANOVA was used to compare means across conditions, and the two-tailed Student's T-test was used to compare each condition to the treatment with the highest yield.

Example 1

[00257] Cell culture: Heterozygous Lgr5-EGFP-IRES-CreERT2 (Lgr5-GFP) mice were obtained from Jackson Labs, and neonatal P2-P5 mice were used for cell isolation. Organ of Corti were isolated from Lgr5-GFP mice and further dissociated into single cells using Tryple (Life Technologies). Cells were then cultured as previously described (Yin et al, 2014). Briefly, cells were entrapped in Matrigel and plated at the center of wells in a 24-well plate. Following polymerization of Matrigel, 500 μΐ of culture media (Advanced DMEM/F12 with N2 and B27) was added, containing growth factors including EGF (50 ng/ml) (epidermal growth factor), bFGF (50 ng/ml) (fibroblast growth factor), and IGFl (50 ng/ml) (insulin-like growth factor 1), Valproic acid sodium salt (lmM), and the small molecules including CHIR99021 (3 μΜ), or AZD1080 (varying concentrations), or GSK3 inhibitor XXII (varying concentrations).

[00258] For single cell isolation, the cochleae were isolated from the otic capsule and the modiolar tissue (auditory nerve) and stria vascularis (ion transport epithelia) were removed. The organ of Corti was then placed in Tryple (Life Technologies) for 15-20 minutes at 37 ^° C. Single cells obtained by mechanical trituration were filtered by cell strainer (40 μιτι). Single cells were then mixed in Matrigel and cultured in a 3D culture system. In each well containing Lgr5 cells in 3D culture, either CHIR99021, AZD1080, or GSK inhibitor XXII were added as described above, in the presence of background growth factors and VP A.

[00259] Lgr5 cell quantification: Cell culture media was removed and Tryple was added. After incubation at 37 °C for 15-20 min, colonies were dissociated into single cells using mechanical trituration. Live Lgr5-GFP cell number was counted using PI staining and the Lgr5-GFP.

[00260] For cochlear explant studies, organ of Corti isolated from Lgr5-GFP mice were treated with either CHIR99021+VPA or GSK3 -inhibitor XXII+VPA for 3 days. Organ of Corti were plated on a cover slip and bathed in media containing the drugs. Growth factors were not present. CHIR99021 (3uM), GSK3 -inhibitor XXII (.3uM), VPA (lmM).

[00261] For the mouse studies, a 17-19% (w/w) stock solution of poloxamer 407 gel (Sigma- Aldrich) was prepared by slowly adding it to cold lx phosphate-buffered saline at pH 7.4. This solution is liquid when refrigerated or at room temperature but solidifies at body temperature. The gel was tinted blue with Evans blue dye (50 ppm) for visualization during administration.

[00262] A formulation was then prepared with 87.6mg/ml VPA and 55.6mg/ml CHIR99021 or 87.6mg/ml VPA and 50mg/ml GSK3 inhibitor XXII in 17-19% Poloxamer 407 with 5% DMSO.

[00263] CBA/CaJ mice were deafened in a noise chamber by exposure to an 8-16 kHz octave band noise band for 2 hours at 120 dB SPL. 24 hours after noise exposure, their hearing was assessed by measuring auditory brainstem responses (ABRs). The minimum sound pressure level (SPL) required for visual detection of ABR Wave I was determined at 5, 10, 20, 28.3, and 40 kHz. Following ABR measurements, a trans-tympanic injection of a Poloxamer gel drug mixture was delivered to fill the middle ear cavity. After 30 days, ABR was assessed and the improvement in hearing threshold from 24hrs to 30 days after noise exposure was determined. The results are shown in Figure 4.

Results

[00264] Lgr5 cells are present within a subset of supporting cells within the cochlear epithelium. Using an Lgr5-GFP mouse line, we tested the activation or inhibition of multiple GSK3 alpha and beta-inhibitors to expand single Lgr5 ⁺ supporting cells isolated from the cochlea in a Matrigel based 3D culture system. Inner ear epithelial cells have been shown to be able to be cultured as neuro-spheres in the presence of growth factors including epidermal growth factor (EGF or E), basic fibroblast growth factor (bFGF or F), and insulin like growth factor 1 (IGF-1 or I) (Li et al, 2003). However, in this condition, no Lgr5-GFP cell growth is observed. Inhibiting the glycogen synthase kinase 3β (GSK3 ) inhibitor with CHIR99021 (CHIR or C) in combination with the histone deacetylase (HDAC) inhibitor, valproic acid (VPA or V), along with EGF, bFGF, and IGF-1 addition has been shown to enhance Lgr5 cell proliferation in cochlear Lgr5 cells (McLean et al). Here, as shown in the Figures, it was found that molecules with stronger GSKa-inhibition preference than CHIR99021 promoted the expansion of Lgr5-GFP cells, and large colonies of Lgr5-GFP+ cells were observed in the culture of the AZD1080 and GSK inhibitor XXII in a background of EGF, bFGF, IGF-1, and VPA (FIG. 1 A and 2A). Flow cytometry analysis also revealed that a combination of CHIR and VPA increased Lgr5-GFP cell number similar to AZD108 and VPA or GSK inhibitor XXII and VPA in background growth factors (Fig IB and 2B). [00265] Organ of Corti treated ex vivo with a molecule (GSK3 inhibitor XXII) that has a higher preference for GSK3a-inhibition compared to CHIR99021, in combination with VP A (V), showed evidence with showed increase in hair cell number.

[00266] When administered to the noise-damaged inner ear, a molecule (GSK3 inhibitor XXII) with a higher preference for GSK3a-inhibition compared to CHIR99021,in combination with VPA (V), showed evidence of hearing recovery.

[00267] As shown in Figure 1 and Figure 2, a cocktail containing growth factors (GF), VPA (V), and GSK3 -inhibitors promoted the proliferation and GFP expression of Lgr5+ inner ear progenitor cells in vitro, and permitted the expansion of these cells.

[00268] The results of Figure 3 show increased number of hair cells in organ of Corti treated ex vivo a molecule (GSK3 inhibitor XXII) that has a higher preference for GSK3a-inhibition than CHIR99021, in combination with VPA (V).

[00269] The results of Figure 4 show hearing recovery in noise-damaged CBA/CaJ mice. Specifically, treatment with GSK3 XXII + VPA, a molecule with a higher preference for GSK3a inhibition, lead to greater hearing recovery than CHIR99021 + VPA (CV). A 10 dB improvement in threshold creates a doubling in loudness for a given sound and is considered to be clinically meaningful. The CV formulation achieved a 10 dB recovery while the VPA/GSK3 inhibitor XXII formulation achieved even greater recoveries.

[00270] From the foregoing description, it will be apparent that variations and modifications may be made to the invention described herein to adopt it to various usages and conditions. Methods and materials are described herein for use in the present invention; other, suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. Such embodiments are also within the scope of the following claims. The recitation of a listing of elements in any definition of a variable herein includes definitions of that variable as any single element or combination (or subcombination) of listed elements. The recitation of an embodiment herein includes that embodiment as any single embodiment or in combination with any other embodiments or portions thereof. The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety. While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.