COMPOSITIONS AND METHODS FOR EMBRYONIC STEM CELL EXPANSION

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63/063,942, filed August 10, 2020, which is incorporated herein by reference in its entirety and for all purposes.

BACKGROUND

[0002] Human embryonic stem cells (hESC) have a basic property of self-renewal, which makes them an unlimited cell source and enables industrial-scale cell therapy initiatives. Their pluripotent developmental potential positioned them as a cell source for most cell therapy products.

[0003] A critical requirement for hESC clinical applications is the supply of a large quantity of hESC-derived therapeutic cells. Production of these therapeutic cells starts from thawing cells of qualified cell banks, such as the master cell bank (MCB) or the working cell bank (WCB), under current good manufacturing practices (cGMP). The quality of the cell bank plays an important role in hESC bioprocessing as it impacts post-thaw hESC expansion, the efficiency of the subsequent lineage-specific differentiation, and process reproducibility.

[0004] Manufacturing such a cell bank is labor intensive, usually requires manual cell manipulations, and there is lot-to-lot variability due to several critical raw materials such as the use of feeder cells, non-recomb inant matrix, serum and other materials which are not fully defined.

BRIEF SUMMARY

[0005] To make such cell therapy initiatives a reality, provided herein are methods for the production of GMP grade hESCs or human-induced pluripotent stem cells (hiPSCs) banks.

[0006] In one aspect, the present disclosure provides a method for expanding and maintaining human embryonic stem cells (hESCs) in an undifferentiated, pluripotent state, the method comprising the steps of (a) simultaneously combining human embryonic stem cells, an extracellular matrix component (ECM), and a microcarrier in growth media to form a suspendable expansion complex, and (b) culturing the suspendable expansion complex for a period of time.

[0007] In some embodiments, the microcarriers comprise one or more of polystyrene, crosslinked dextran, magnetic particles, microchips, cellulose, hydroxylated methacrylate, collagen, gelatin, polystyrene, plastic, glass, ceramic, silicone, or a combination thereof.

[0008] In some embodiments, the microcarriers are spherical, smooth, macroporous, rodshaped, or a combination thereof.

[0009] In some embodiments, the ECM comprises matrigel, laminin, vitronectin, collagen, their derivatives, or a combination thereof. In specific embodiments, the ECM is human laminin. In specific embodiments, the human laminin is human laminin 511 E8 fragment.

[0010] In specific embodiments, the microcarriers are not coated.

[0011] In some embodiments, the microcarriers are coupled with protamine or polylysine.

[0012] In some embodiments, the microcarriers are neutral or negatively charged. In specific embodiments, the microcarriers are neutral. In specific embodiments, the microcarriers are negatively charged. In specific embodiments, the microcarriers are hydrophilic.

[0013] In some embodiments, the suspendable expansion complex is cultured for at least about one day. In some embodiments, the suspendable expansion complex is cultured from about one day to about fourteen days.

[0014] In some embodiments, the cultured cells of the suspendable expansion complex are harvested and expanded further by repeating steps (a) and (b).

[0015] In some embodiments, the cultured cells of the suspendable expansion complex are harvested and further differentiated. In some embodiments, the cultured cells of the suspendable expansion complex are further differentiated by changing the growth medium.

[0016] In some embodiments, the cultured cells of the suspendable expansion complex remain undifferentiated and pluripotent. In some embodiments, the undifferentiated cells express at least about 80% of each of S SEA-5 and TRA-1-60. In some embodiments, the undifferentiated cells express at least about 70% of each of Oct-4 and Nanog. In some embodiments, the undifferentiated cells express at least about 80% of SSEA-5, at least about 80% of TRA-1-60, at least about 70% of Oct-4, and at least about 70% of Nanog.

[0017] In another aspect, the present disclosure provides a suspendable expansion complex composition comprising human embryonic stem cells, an extracellular matrix component (ECM), and a microcarrier.

[0018] In some embodiments, the composition further comprises a growth medium.

[0019] In some embodiments, the microcarriers comprise one or more of polystyrene, crosslinked dextran, magnetic particles, microchips, cellulose, hydroxylated methacrylate, collagen, gelatin, polystyrene, plastic, glass, ceramic, silicone. In some embodiments, the microcarriers are spherical, smooth, macroporous, rod-shaped, or a combination thereof.

[0020] In some embodiments, the microcarriers are coated with matrigel, laminin, vitronectin, collagen, their derivatives, or a combination thereof. In some embodiments, the laminin is human laminin. In specific embodiments, the human laminin is human laminin 511 E8 fragment.

[0021] In some embodiments, the microcarriers are not coated.

[0022] In some embodiments, the microcarriers are coupled with protamine or polylysine.

[0023] In some embodiments, the microcarriers are neutral or negatively charged. In some embodiments, the microcarriers are neutral. In some embodiments, the microcarriers are negatively charged. In some embodiments, the microcarriers are hydrophilic.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 shows morphology assessment along passage. Pl on MC Group A- Synthemax® II MC, Group B- Enhanced Attachment MC. Cells grown on MC were harvested and seeded for P2 on TC treated T25 flasks.

[0025] FIG. 2 shows morphology of harvested cells from the hESC scale-up system during DC differentiation.

[0026] FIG. 3 shows the hESC expansion scale-up system process. [0027] FIG. 4 shows the morphology of cells in the hESC scale-up system.

[0028] FIG. 5 shows the morphology of harvested cells from the hESCs scale-up system after re-seeding as hESCs 2D culture.

[0029] FIG. 6 shows the morphology of the hESC scale-up system under the tested conditions.

[0030] FIG. 7 shows the morphology of the hESC scale-up system in different platforms.

[0031] FIG. 8 shows the morphology of the hESC scale-up system with different iMatrix- 511 E8 concentrations.

[0032] FIG. 9 shows the morphology of the hESC scale-up system in different passage durations.

[0033] FIG. 10 shows the morphology of cells cultured in the hESC scale-up system before cryopreservation and after thawing as 2D culture.

[0034] FIG. 11 shows culturing parameters and pluripotency marker expression of cells cultured in the hESCs scale-up system and passaged as 2D culture.

DETAILED DESCRIPTION

[0035] Embodiments herein generally relate to methods, compositions of matter, and devices for expanding embryonic stem cells.

[0036] After reading this description it will become apparent to one skilled in the art how to implement the present disclosure in various alternative embodiments and alternative applications. However, all the various embodiments of the present invention will not be described herein. It will be understood that the embodiments presented here are presented by way of an example only, and not limitation. As such, this detailed description of various alternative embodiments should not be construed to limit the scope or breadth of the present disclosure as set forth herein.

[0037] Before the present technology is disclosed and described, it is to be understood that the aspects described below are not limited to specific compositions, methods of preparing such compositions, or uses thereof as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0038] The detailed description divided into various sections only for the reader’s convenience and disclosure found in any section may be combined with that in another section. Titles or subtitles may be used in the specification for the convenience of a reader, which are not intended to influence the scope of the present disclosure.

DEFINITIONS

[0039] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0040] “Optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0041] The term “about” when used before a numerical designation, e.g., temperature, time, amount, concentration, and such other, including a range, indicates approximations which may vary by ( + ) or ( - ) 10%, 5%, 1%, or any subrange or subvalue there between. Preferably, the term “about” when used with regard to an amount means that the amount may vary by +/- 10%.

[0042] “Comprising” or “comprises” is intended to mean that the compositions and methods include the recited elements, but not excluding others. “Consisting essentially of’ when used to define compositions and methods, shall mean excluding other elements of any essential significance to the combination for the stated purpose. Thus, a composition consisting essentially of the elements as defined herein would not exclude other materials or steps that do not materially affect the basic and novel characteristic(s) of the claimed invention. “Consisting of’ shall mean excluding more than trace elements of other ingredients and substantial method steps. Embodiments defined by each of these transition terms are within the scope of this disclosure.

[0043] An “effective amount” is an amount sufficient for a composition to accomplish a stated purpose relative to the absence of the composition (e.g. achieve the effect for which it is administered, treat a disease, reduce enzyme activity, increase enzyme activity, reduce a signaling pathway, or reduce one or more symptoms of a disease or condition). An example of an “effective amount” is an amount sufficient to contribute to the treatment, prevention, or reduction of a symptom or symptoms of a disease, which could also be referred to as a “therapeutically effective amount.” A “reduction” of a symptom or symptoms (and grammatical equivalents of this phrase) means decreasing of the severity or frequency of the symptom(s), or elimination of the symptom(s). A “prophylactically effective amount” of a drug (e.g., the cells described herein) is an amount of the drug that, when administered to a subject, will have the intended prophylactic effect, e.g., preventing or delaying the onset (or reoccurrence) of an injury, disease, pathology or condition, or reducing the likelihood of the onset (or reoccurrence) of an injury, disease, pathology, or condition, or their symptoms. The full prophylactic effect does not necessarily occur by administration of one dose, and may occur only after administration of a series of doses. Thus, a prophylactically effective amount may be administered in one or more administrations. An “activity decreasing amount,” as used herein, refers to an amount of antagonist required to decrease the activity of an enzyme relative to the absence of the antagonist. A “function disrupting amount,” as used herein, refers to the amount of antagonist required to disrupt the function of an enzyme or protein relative to the absence of the antagonist. The exact amounts will depend on the purpose of the treatment, and will be ascertainable by one skilled in the art using known techniques (see, e.g., Lieberman, Pharmaceutical Dosage Forms (vols. 1-3, 1992); Lloyd, The Art, Science and Technology of Pharmaceutical Compounding (1999); Pickar, Dosage Calculations (1999); and Remington: The Science and Practice of Pharmacy, 20th Edition, 2003, Gennaro, Ed., Lippincott, Williams & Wilkins).

[0044] For any composition described herein, the therapeutically effective amount can be initially determined from cell culture assays. Target concentrations will be those concentrations of active composition(s) (e.g., cell concentration or number) that are capable of achieving the methods described herein, as measured using the methods described herein or known in the art.

[0045] “Control” or “control experiment” is used in accordance with its plain ordinary meaning and refers to an experiment in which the subjects or reagents of the experiment are treated as in a parallel experiment except for omission of a procedure, reagent, or variable of the experiment. In some instances, the control is used as a standard of comparison in evaluating experimental effects. In some embodiments, a control is the measurement of the activity of a protein in the absence of a composition as described herein (including embodiments and examples). [0046] “Pharmaceutically acceptable excipient” and “pharmaceutically acceptable carrier” refer to a substance that aids the administration of an active agent to and absorption by a subject and can be included in the compositions of the present disclosure without causing a significant adverse toxicological effect on the patient. Non-limiting examples of pharmaceutically acceptable excipients include water, NaCl, normal saline solutions, lactated Ringer’s, normal sucrose, normal glucose, binders, fillers, disintegrants, lubricants, coatings, sweeteners, flavors, salt solutions (such as Ringer's solution), alcohols, oils, gelatins, carbohydrates such as lactose, amylose or starch, fatty acid esters, hydroxymethycellulose, polyvinyl pyrrolidine, and colors, and the like. Such preparations can be sterilized and, if desired, mixed with auxiliary agents such as lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salts for influencing osmotic pressure, buffers, coloring, and/or aromatic substances and the like that do not deleteriously react with the compositions of the disclosure. One of skill in the art will recognize that other pharmaceutical excipients are useful in the present disclosure.

[0047] A “cell” as used herein, refers to a cell carrying out metabolic or other function sufficient to preserve or replicate its genomic DNA. A cell can be identified by well-known methods in the art including, for example, presence of an intact membrane, staining by a particular dye, ability to produce progeny or, in the case of a gamete, ability to combine with a second gamete to produce a viable offspring. Cells may include prokaryotic and eukaryotic cells. Prokaryotic cells include but are not limited to bacteria. Eukaryotic cells include but are not limited to yeast cells and cells derived from plants and animals, for example mammalian, insect (e.g., spodoptera) and human cells. Cells may be useful when they are naturally nonadherent or have been treated not to adhere to surfaces, for example by trypsinization.

[0048] As used herein, the "stem cells" refers to cells which are capable of remaining in an undifferentiated state (e.g., pluripotent or multipotent stem cells) for extended periods of time in culture until induced to differentiate into other cell types having a particular, specialized function (e.g., fully differentiated cells). In embodiments, "stem cells" include embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), adult stem cells, mesenchymal stem cells and hematopoietic stem cells.

[0049] As used herein, “induced pluripotent stem cells” or “iPSCs” are cells that can be generated from somatic cells by genetic manipulation of somatic cells, e.g., by retroviral transduction of somatic cells such as fibroblasts, hepatocytes, gastric epithelial cells with transcription factors such as Oct-3/4, Sox2, c-Myc, and KLF4 [Yamanaka S, Cell Stem Cell. 2007, 1 ( 1 ):39-49; Aoi T, et al., Generation of Pluripotent Stem Cells from Adult Mouse Liver and Stomach Cells. Science. 2008 Feb 14. (Epub ahead of print); IH Park, Zhao R, West JA, et al. Reprogramming of human somatic cells to pluripotency with defined factors. Nature 2008;451:141-146; K Takahashi, Tanabe K, Ohnuki M, et al. Induction of pluripotent stem cells from adult human fibroblasts by defined factors. Cell 2007;131:861-872], Other embryonic-like stem cells can be generated by nuclear transfer to oocytes, fusion with embryonic stem cells or nuclear transfer into zygotes if the recipient cells are arrested in mitosis. In addition, iPSCs may be generated using non-integrating methods e.g., by using small molecules or RNA.

[0050] The term "embryonic stem cells" refers to embryonic cells that are capable of differentiating into cells of all three embryonic germ layers (i.e., endoderm, ectoderm and mesoderm), or remaining in an undifferentiated state. The phrase "embryonic stem cells" comprise cells which are obtained from the embryonic tissue formed after gestation (e.g., blastocyst) before implantation of the embryo (i.e., a pre-implantation blastocyst), extended blastocyst cells (EBCs) which are obtained from a post-implantation/pre-gastrulation stage blastocyst (see WO 2006/040763) and embryonic germ (EG) cells which are obtained from the genital tissue of a fetus any time during gestation, preferably before 10 weeks of gestation. In embodiments, embryonic stem cells are obtained using well-known cell-culture methods. For example, human embryonic stem cells can be isolated from human blastocysts.

[0051] It is appreciated that commercially available stem cells can also be used in aspects and embodiments of the present disclosure. Human ES cells may be purchased from the NIH human embryonic stem cells registry, www.grants.nih.govstem_cells/ or from other hESC registries. Non-limiting examples of commercially available embryonic stem cell lines are HAD-C 102, ESI, BGO 1, BG02, BG03, BG04, CY12, CY30, CY92, CY1O, TE03, TE32, CHB-4, CHB-5, CHB-6, CHB-8, CHB-9, CHB-10, CHB-11, CHB-12, HUES 1, HUES 2, HUES 3, HUES 4, HUES 5, HUES 6, HUES 7, HUES 8, HUES 9, HUES 10, HUES 11, HUES 12, HUES 13, HUES 14, HUES 15, HUES 16, HUES 17, HUES 18, HUES 19, HUES 20, HUES 21, HUES 22, HUES 23, HUES 24, HUES 25, HUES 26, HUES 27, HUES 28, CyT49, RUES3, WAO 1, UCSF4, NYUES 1, NYUES2, NYUES3, NYUES4, NYUESS, NYUES6, NYUES7, UCLA 1, UCLA 2, UCLA 3, WA077 (H7), WA09 (H9), WA 13 (Hl 3), WA14 (H14), HUES 62, HUES 63, HUES 64, CT I, CT2, CT3, CT4, MA135, Eneavour-2, WIBR 1, WIBR2, WIBR3, WIBR4, WIBRS, WIBR6, HUES 45, Shef 3, Shef 6, BINheml9, BJNhem20, SAGO 1, SAOO1.

[0052] As used herein, the term “microcarrier” or “MC” refers to a suspendible support matrix that allows adherent cells to grow in dynamic or static cell culture, and can stay in suspension with gentle mixing. Microcarriers can be composed of including, but not limited to, polystyrene, surface-modified polystyrene, chemically modified polystyrene, cross-linked dextran, cellulose, acrylamide, collagen, alginate, gelatin, glass, DEAE-dextran, or a combination thereof. Microcarriers can be coated with a biological support matrix, including, but not limited to, laminin, Matrigel, collagen, poly-lysine, poly-L-lysine, poly-D-lysine, vitronectin, fibronectin, tenascin, dextran, a peptide, or a combination thereof. Many different types of microcarriers are commercially available, including, but not limited to, HyQSphere (HyClone), Hillex (SoloHill Engineering), and Low Concentration Synthemax® II (Coming) brands. Microcarriers can be made from cross-linked dextran such as the Cytodex brand (GE Healthcare). Microcarriers can be spherical and smooth, can have microporous surfaces, such as CYTOPORE brand (GE Healthcare), and/or can be rod-shaped carriers such as DE-53 (Whatman). Microcarriers can be impregnated with magnetic particles that may help in cell separation from beads (e.g., GEM particles from Global Cell Solutions). Chip-based microcarriers such as the μHex product (Nunc) provide a flat surface for cell growth while maintaining the high surface to volume ratio of traditional microcarriers. The properties of microcarriers may significantly affect expansion rates and cell multi- or pluripotency.

METHODS

[0053] In an aspect, provided herein are methods for expanding and maintaining human embryonic stem cells (hESCs) in an undifferentiated, pluripotent state, the method comprising the steps of (a) simultaneously combining human embryonic stem cells, an extracellular matrix component (ECM), and a microcarrier in growth media to form a suspendable expansion complex, and (b) culturing the suspendable expansion complex for a period of time.

[0054] In some embodiments, the cultured cells of the suspendable expansion complex are harvested and expanded further by repeating steps (a) and (b).

[0055] In some embodiments, the cultured cells of the suspendable expansion complex are harvested and further differentiated. [0056] Human embryonic stem cells can be isolated from human blastocysts. Human blastocysts are typically obtained from human in vivo preimplantation embryos or from in vitro fertilized (IVF) embryos. Alternatively, a single cell human embryo can be expanded to the blastocyst stage. For the isolation of human ES cells the zona pellucida is removed from the blastocyst and the inner cell mass (ICM) is isolated by a procedure in which the trophectoderm cells are lysed and removed from the intact ICM by gentle pipetting. The ICM is then plated in a tissue culture flask containing the appropriate medium which enables its outgrowth. Following 9 to 15 days, the ICM derived outgrowth is dissociated into clumps either by a mechanical dissociation or by an enzymatic degradation and the cells are then re-plated on a fresh tissue culture medium. Colonies demonstrating undifferentiated morphology are individually selected by micropipette, mechanically dissociated into clumps, and re-plated. Resulting ES cells are then routinely split every 4-7 days. For further details on methods of preparation human ES cells, see Reubinoff et al. Nat Biotechnol 2000, May: 18(5): 559; Thomson et al., [U.S. Patent No. 5,843,780; Science 282: 1145, 1998; Curr. Top. Dev. Biol. 38: 133, 1998; Proc. Natl. Acad. Sci. USA 92: 7844, 1995]; Bongso et al., [Hum Reprod 4: 706, 1989]; and Gardner et al., [Fertil. Steril. 69: 84, 1998].

[0057] In addition, ES cells can be obtained from other species, including mouse (Mills and Bradley, 2001), golden hamster [Doetschman et al., 1988, Dev Biol. 127: 224-7], rat [lannaccone et al., 1994, Dev Biol. 163: 288-92], rabbit [Giles et al. 1993, Mol Reprod Dev. 36: 130-8; Graves & Moreadith, 1993, Mol Reprod Dev. 1993, 30 36: 424-33], several domestic animal species [Notarianni et al., 1991, J Reprod Fertil Suppl. 43: 255-60; Wheeler 1994, Reprod Fertil Dev. 6: 563-8; Mitalipova et al., 2001, Cloning. 3: 59-67] and non-human primate species (Rhesus monkey and marmoset) [Thomson et al., 1995, Proc Natl Acad Sci U S A. 92: 7844-8; Thomson et al., 1996, Biol Reprod. 55: 254-9].

[0058] Extended blastocyst cells (EBCs) can be obtained from a blastocyst of at least nine days post fertilization at a stage prior to gastrulation. Prior to culturing the blastocyst, the zona pellucida is digested [for example by Tyrode’s acidic solution (Sigma Aldrich, St Louis, MO, USA)] so as to expose the inner cell mass. The blastocysts are then cultured as whole embryos for at least nine and no more than fourteen days post fertilization (i.e., prior to the gastrulation event) in vitro using standard embryonic stem cell culturing methods.

[0059] Another method for preparing ES cells is described in Chung et al., Cell Stem Cell, Volume 2, Issue 2, 113-117, 7 February 2008. This method comprises removing a single cell from an embryo during an in vitro fertilization process. The embryo is not destroyed in this process.

[0060] EG (embryonic germ) cells are prepared from the primordial germ cells obtained from fetuses of about 8-11 weeks of gestation (in the case of a human fetus) using laboratory techniques known to anyone skilled in the arts. The genital ridges are dissociated and cut into small portions which are thereafter disaggregated into cells by mechanical dissociation. The EG cells are then grown in tissue culture flasks with the appropriate medium. The cells are cultured with daily replacement of medium until a cell morphology consistent with EG cells is observed, typically after 7-30 days or 1-4 passages. For additional details on methods of preparation human EG cells see Shamblott et al., [Proc. Natl. Acad. Sci. USA 95: 13726, 1998] and U.S. Patent No. 6,090,622.

[0061] Yet another method for preparing ES cells is by parthenogenesis. The embryo is also not destroyed in the process.

[0062] The cells may be expanded in suspension, with or without a microcarrier, or in a monolayer. The expansion of the mixed population of cells in monolayer cultures or in suspension culture may be modified to large scale expansion in bioreactors or multi/hyper stacks by methods well known to those versed in the art.

[0063] According to some embodiments, the expansion phase is effected for at least one to 20 weeks, for example at least one week, at least 2 weeks, at least 3 weeks, at least 4 weeks, at least 5 weeks, at least 6 weeks, at least 7 weeks, at least 8 weeks, at least 9 weeks or even 10 weeks. In embodiments, the expansion phase is effected for 1 week to 10 weeks, such 2 weeks to 10 weeks, 3 weeks to 10 weeks, 4 weeks to 10 weeks, or 4 weeks to 8 weeks. The time period may be any value or subrange within the recited ranges, including endpoints.

[0064] According to still other embodiments, the mixed population of cells are passaged at least one time during the expansion phase, at least twice during the expansion phase, at least three times during the expansion phase, at least four times during the expansion phase, at least five times during the expansion phase, at least six times during the expansion phase, or at least seven times during the expansion phase.

[0065] When cells are collected enzymatically, it is possible to continue the expansion for more than 8 passages, more than 9 passages and even more than 10 passages (e.g. 11-15 passages). The number of total cell doublings can be increased to greater than 30, e.g. 31, 32, 33, 34 or more. (See international patent application publication number WO 2017/021973, incorporated herein by reference in its entirety).

[0066] An extracellular matrix (ECM) is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and biochemical support to surrounding cells. Because multicellularity evolved independently in different multicellular lineages, the composition of ECM varies between multicellular structures; however, cell adhesion, cell-to-cell communication and differentiation are common functions of the ECM.

[0067] The animal extracellular matrix includes the interstitial matrix and the basement membrane. Interstitial matrix is present between various animal cells (i.e., in the intercellular spaces). Gels of polysaccharides and fibrous proteins fill the interstitial space and act as a compression buffer against the stress placed on the ECM. Basement membranes are sheet-like depositions of ECM on which various epithelial cells rest. Each type of connective tissue in animals has a type of ECM: collagen fibers and bone mineral comprise the ECM of bone tissue; reticular fibers and ground substance comprise the ECM of loose connective tissue; and blood plasma is the ECM of blood.

[0068] Suitable extracellular matrix components for use within the scope of the present disclosure may include, but are not necessarily limited to, matrigel, vitronectin, gelatin, collagen I, collagen IV, laminin (e.g. laminin 521), fibronectin poly-D-lysine, their derivatives, or a combination thereof. In specific embodiments, the human laminin is human laminin 511 E8 fragment.

[0069] In some embodiments, the microcarriers may comprise one or more of polystyrene, cross-linked dextran, magnetic particles, microchips, cellulose, hydroxylated methacrylate, collagen, gelatin, polystyrene, plastic, glass, ceramic, or silicone. In some embodiments, the microcarriers are composed of polystyrene, surface-modified polystyrene, chemically modified polystyrene, cross-linked dextran, cellulose, acrylamide, collagen, alginate, gelatin, glass, DEAE-dextran, or a combination thereof. In some embodiments, the microcarrier is composed of polystyrene. In some embodiments, the microcarrier is composed of surface-modified polystyrene. In some embodiments, the microcarrier is composed of chemically modified polystyrene. In some embodiments, the microcarrier is composed of cross-linked dextran. In some embodiments, the microcarrier is composed of cellulose. In some embodiments, the microcarrier is composed of acrylamide. In some embodiments, the microcarrier is composed of collagen. In some embodiments, the microcarrier is composed of alginate. In some embodiments, the microcarrier is composed of gelatin. In some embodiments, the microcarrier is composed of glass. In some embodiments, the microcarrier is composed of DEAE-dextran. In some embodiments, the microcarriers are not coated.

[0070] In some embodiments, the microcarriers are coated. In embodiments, the microcarriers may be coated with matrigel, laminin, vitronectin, collagen, their derivatives, or a combination thereof. In embodiments, the microcarriers may be coated by poly-lysine, poly- L-lysine, poly-D-lysine, fibronectin, tenascin, dextran, a peptide, or a combination thereof. In some embodiments, the microcarrier is coated with laminin. In some embodiments, the microcarrier is coated with Matrigel. In some embodiments, the microcarrier is coated with collagen. In some embodiments, the s microcarrier is coated with poly-lysine. In some embodiments, the microcarrier is coated with poly-L-lysine. In some embodiments, the microcarrier is coated with poly-D-lysine. In some embodiments, the microcarrier is coated with vitronectin. In some embodiments, the microcarrier is coated with fibronectin. In some embodiments, the microcarrier is coated with tenascin. In some embodiments, the microcarrier is coated with dextran. In some embodiments, the microcarrier is coated with a peptide.

[0071] In some embodiments, the microcarriers may be spherical, smooth, macroporous, rod-shaped, or a combination thereof. In some embodiments, the microcarriers maybe coupled with protamine or polylysine. In some embodiments, the microcarrier is spherical. In some embodiments, the s microcarrier is ellipsoidal. In some embodiments, the microcarrier is rodshaped. In some embodiments, the microcarrier is disc-shaped. In some embodiments, the microcarrier is porous. In some embodiments, the microcarrier is non-porous. In some embodiments, the microcarrier is smooth. In some embodiments, the microcarrier is flat.

[0072] In some embodiments, the microcarriers are neutral. In some embodiments, the microcarriers are negatively charged. In some embodiments, the microcarriers are hydrophilic.

[0073] In some embodiments, the microcarriers may have a surface area of 25 cm ² , 50 cm ² , 75 cm ² , 100 cm ² , 125 cm ² , 150 cm ² , 175 cm ² , 200 cm ² , 225 cm ² , 250 cm ² , 500 cm ² , 625 cm ² , 750 cm ² , 1,000 cm ² , 1,250 cm ² , 5,000 cm ² , or 7,500 cm ² . The surface area may be any value or subrange within the recited ranges, including endpoints. [0074] In specific embodiments, the microcarriers are surface treated to enhance cell attachment, maximizing cell yield and viability. The microcarriers may be comprised of USP Class VI polystyrene material, which provides a consistent platform. In some embodiments, the microcarriers create a synthetic surface on the microcarriers for stem cell expansion. An enhanced attachment surface treatment infuses the surface of the microcarriers with oxygen to improve cell attachment. In some embodiments, the microcarriers are nonpyrogenic. In some embodiments, the microcarriers are optimized for mesenchymal stem cell applications. In specific embodiments, the beads may vary in size from 125-212 pm. In specific embodiments, the density of the microcarriers may be 1.026 ± 0.004. In specific embodiments, the microcarriers may be 360 cm ² /gram.

[0075] In some embodiments, the method comprises combining the hESCs with laminin or a derivative thereof to improve the cell attachment to the carrier surface. In specific embodiments, the laminin is human laminin 511. As alternative embodiments, several other extracellular matrices may be used for cell attachment, such as including, but not necessarily limited to, vitronectin, fibronectin, collagen, matrigel, or derivatives thereof.

[0076] In some embodiments, the cells may be cultured for one day, two days, three days, four days, five days, six days, seven days, eight days, nine days, ten days, eleven days, twelve days, thirteen days, or fourteen days.

[0077] In some embodiments, the cells may be cultured in a working volume of between 10 mL and 3,000 mL, for example about 10 mL, 20 mL, 30 mL, 40 mL, 50 mL, 100 mL, 250 mL, 500 mL, 750 mL, 1,000 mL, or 3,000 mL. The volume may be any value or subrange within the recited ranges, including endpoints.

[0078] In some embodiments, the cultured cells may be expanded further.

[0079] In some embodiments, the cultured cells may remain undifferentiated. Undifferentiated cells may be identified by expression of various markers, such as including, but not necessarily limited to, SSEA-5, TRA-1-60, Oct-4, and Nanog. In some embodiments, undifferentiated cells express SSEA-5. In some embodiments, undifferentiated cells express TRA-1-60. In some embodiments, undifferentiated cells express Oct-4. In some embodiments, undifferentiated cells express Nanog. In some embodiments, undifferentiated cells express both SSEA-5 and TRA-1-60. In some embodiments, undifferentiated cells express both Oct-4 and Nanog. In some embodiments, undifferentiated cells express SSEA-5, TRA-1-60, Oct-4, and Nanog.

[0080] In some embodiments, the cells maybe cultured in a feeder cell-conditioned medium. ES culturing methods may include the use of feeder cell layers which secrete factors needed for stem cell proliferation, while at the same time, inhibiting their differentiation. The culturing is typically effected on a solid surface, for example a surface coated with gelatin or vimentin. Exemplary feeder layers include human embryonic fibroblasts, adult fallopian epithelial cells, primary mouse embryonic fibroblasts (PMEF), mouse embryonic fibroblasts (MEF), murine fetal fibroblasts (MFF), human embryonic fibroblast (HEF), human fibroblasts obtained from the differentiation of human embryonic stem cells, human fetal muscle cells (HFM), human fetal skin cells (HFS), human adult skin cells, human foreskin fibroblasts (HFF), human umbilical cord fibroblasts, human cells obtained from the umbilical cord or placenta, and human marrow stromal cells (hMSCs). Growth factors may be added to the medium to maintain the ESCs in an undifferentiated state. Such growth factors include bFGF and/or TGF. In another embodiment, agents may be added to the medium to maintain the hESCs in a naive undifferentiated state - see for example Kalkan et al., 2014, Phil. Trans. R. Soc. B, 369: 20130540.

[0081] hESCs are typically plated on top of the feeder cells 1-4 days later in a supportive medium (e.g. NUTRISTEM® or NUT(+) with human serum albumin,). Additional factors may be added to the medium to prevent differentiation of the ESCs such as bFGF and TGFI3. Once a sufficient amount of hESCs is obtained, the cells may be mechanically disrupted (e.g. by using a sterile tip or a disposable sterile stem cell tool; 14602 Swemed). Alternatively, the cells may be removed by enzymatic treatment (e.g. collagenase A, or TrypLE Select). This process may be repeated several times to reach the necessary amount of hESC. According to some embodiments, following the first round of expansion, the hESCs are removed using TrypLE Select and following the second round of expansion, the hESCs are removed using collagenase A.

[0082] Feeder cell free systems have also been used in ES cell culturing, such systems utilize matrices supplemented with serum replacement, cytokines and growth factors (including IL6 and soluble IL6 receptor chimera) as a replacement for the feeder cell layer. Stem cells can be grown on a solid surface such as an extracellular matrix (e.g., MATRIGELR™, laminin or vitronectin) in the presence of a culture medium - for example the Lonza L7 system, mTeSR, StemPro, XFKSR, E8, NUTRISTEM®). Unlike feeder-based cultures which require the simultaneous growth of feeder cells and stem cells and which may result in mixed cell populations, stem cells grown on feeder-free systems are easily separated from the surface. The culture medium used for growing the stem cells contains factors that effectively inhibit differentiation and promote their growth such as MEF-conditioned medium and bFGF.

[0083] Also within the scope of the present disclosure are methods for expanding and maintaining human embryonic stem cells (hESCs) in an undifferentiated state, comprising culturing human pluripotent stem cells on a non-adherent surface to obtain a population of undifferentiated hESCs, combining said population of undifferentiated hESCs with microcarriers in growth media, and expanding said population of cells.

[0084] Examples of non-adherent cell culture plates include those manufactured by Nunc (e.g. Hydrocell Cat No. 174912), etc. In other embodiments, non-adherent suspension culture dishes may be used (e.g., Coming).

[0085] According to some embodiments, when the cells are cultured on the non-adherent substrate, e.g. cell culture plates, the atmospheric oxygen conditions are 20%. However, manipulation of the atmospheric oxygen conditions is also contemplated such that the atmospheric oxygen percent is less than about 20%, 15%, 10%, 9%, 8%, 7%, 6% or even less than about 5% (e.g. between 1% - 20%, 1 %-l 0% or 0-5 %). According to other embodiments, the cells are cultured on the non-adherent substrate initially under normal atmospheric oxygen conditions and then lowered to less than normal atmospheric oxygen conditions.

[0086] In some embodiments, the method may further comprise freezing (e.g., cryopreserving) the expanded population of cells. Examples of media suitable for cryopreservation include but are not limited to 90% Human Serum/10% DMSO, Media 3 10% (CS10), Media 2 5% (CS5) and Media 1 2% (CS2), Stem Cell Banker, PRIME XV° FREEZIS, HYPOTHERMASOL®, Trehalose, etc.

[0087] In further embodiments, the cryopreservation medium includes: a purine nucleoside (e.g., adenosine), a branched glucan (e.g., dextran 40), a zwitterionic organic chemical buffering agent (e.g., HEPES (N-(2-Hydroxyethyl) piperazine EN’-(2E ethanesulfonic acid))), and a cell tolerable polar aprotic solvent (e.g., dimethyl sulfoxide (DMSO). In still further embodiments, one or more of the purine nucleoside, branched glucan, buffering agent, and the polar aprotic solvent are generally recognized as safe by the US FDA.

[0088] In some embodiments, the cryopreservation media further includes one or more of: a sugar acid (e.g., lactobionic acid), one or more of a base (e.g., sodium hydroxide, potassium hydroxide), an antioxidant (e.g., L-glutathione), one or more halide salt (e.g., potassium chloride, sodium chloride, magnesium chloride), a basic salt (e.g., potassium bicarbonate), phosphate salt (e.g., potassium phosphate, sodium phosphate, potassium phosphate), one or more sugars (e.g., dextrose, sucrose), sugar alcohol, (e.g., mannitol), and water.

[0089] In other embodiments, one or more of the sugar acid, base, halide salt, basic salt, antioxidant, phosphate salt, sugars, sugar alcohols are generally recognized as safe by the US FDA.

[0090] DMSO can be used as a cryoprotective agent to prevent the formation of ice crystals, which can kill cells during the cryopreservation process. In some embodiments, the cryopreservable medium comprises between about 0.1% and about 2% DMSO (v/v). In some embodiments, the cryopreservable medium comprises between about 1% and about 20% DMSO. In some embodiments, the cryopreservable medium comprises about 2% DMSO. In some embodiments, the cryopreservable medium comprises about 5% DMSO.

[0091] In some embodiments, the method may further comprise culturing the expanded population of cells on an adherent surface in a medium comprising a differentiating agent to obtain differentiating cells. Examples of adherent substrates or a mixture of substances could include but are not limited to fibronectin, laminin, polyD-lysine, collagen and gelatin. In one embodiment, the differentiating is effected in the presence of nicotinamide (e.g. between 0.01- 100 mM, 0.1-100 mM, 0.1-50 mM, 5-50 mM, 5-20 mM, e.g. 10 mM), and in the absence of activin A. The concentration may be any value or subrange within the recited ranges, including endpoints.

[0092] According to some embodiments, the cells are cultured on the adherent substrate initially under normal atmospheric oxygen conditions and subsequently the oxygen is lowered to less than normal atmospheric oxygen conditions.

[0093] According to some embodiments, when the cells are cultured on the adherent substrate e.g. laminin, the atmospheric oxygen conditions are 20%. They may be manipulated such that the atmospheric oxygen percentage is less than about 20%, 15%, 10%, more preferably less than about 9%, less than about 8%, less than about 7%, less than about 6% and more preferably about 5% (e.g. between 1% - 20%, 1% -10% or 0-5%). The amount may be any value or subrange within the recited ranges, including endpoints.

[0094] In some embodiments, the cells are cultured in a feeder cell-conditioned medium, as described in detail above.

[0095] In some embodiments, the cells are cultured in the absence of feeder cells.

[0096] In some embodiments, after initial expansion, the cells may be further expanded.

[0097] In some embodiments, the cells may be cultured for one day, two days, three days, four days, five days, six days, or seven days.

[0098] In some embodiments, the cultured cells may be expanded further.

[0099] In some embodiments, the cultured cells of the suspendable expansion complex are harvested and further differentiated. In some embodiments, the cultured cells of the suspendable expansion complex are further differentiated by changing the growth medium. In some embodiments, the cultured cells of the suspendable expansion complex remain undifferentiated and pluripotent.

Additional Embodiments

[0100] The present disclosure provides the following illustrative embodiments.

Embodiment 1 - A method for expanding and maintaining human embryonic stem cells (hESCs) in an undifferentiated, pluripotent state, the method comprising the steps of (a) simultaneously combining human embryonic stem cells, an extracellular matrix component (ECM), and a microcarrier in growth media to form a suspendable expansion complex, and (b) culturing the suspendable expansion complex for a period of time.

Embodiment 2 -The method of embodiment 1 , wherein the microcarriers comprise one or more of polystyrene, cross-linked dextran, magnetic particles, microchips, cellulose, hydroxylated methacrylate, collagen, gelatin, polystyrene, plastic, glass, ceramic, silicone, or a combination thereof. Embodiment 3 - The method of embodiment 1 or 2, wherein the microcarriers are spherical, smooth, macroporous, rod-shaped, or a combination thereof.

Embodiment 4 - The method of any of embodiments 1 to 3, wherein the ECM comprises matrigel, laminin, vitronectin, collagen, their derivatives, or a combination thereof.

Embodiment 5 - The method of embodiment 1 , wherein the ECM is human laminin.

Embodiment 6 - The method of embodiment 5 wherein the human laminin is human laminin 511 E8 fragment.

Embodiment 7 - The method of any of embodiments 1 to 3, wherein the microcarriers are not coated.

Embodiment 8 - The method of any of embodiments 1 to 7, wherein the microcarriers are coupled with protamine or polylysine.

Embodiment 9 - The method of any of embodiments 1 to 7, wherein the microcarriers are neutral or negatively charged.

Embodiment 10 - The method of embodiment 9, wherein the microcarriers are neutral.

Embodiment 11 - The method of embodiment 9, wherein the microcarriers are negatively charged.

Embodiment 12 - The method of any of embodiments 1 to 11, wherein the microcarriers are hydrophilic.

Embodiment 13 - The method of any of embodiments 1 to 12, wherein the suspendable expansion complex is cultured for at least about one day.

Embodiment 14 - The method of embodiment 13, wherein the suspendable expansion complex is cultured from about one day to about fourteen days.

Embodiment 15 - The method of embodiment 1, wherein the cultured cells of the suspendable expansion complex are harvested and expanded further by repeating steps (a) and (b). Embodiment 16 - The method of embodiment 1 wherein the cultured cells of the suspendable expansion complex are harvested and further differentiated.

Embodiment 17 - The method of embodiment 16 wherein the cultured cells of the suspendable expansion complex are further differentiated by changing the growth medium.

Embodiment 18 - The method of embodiment 1 , wherein the cultured cells of the suspendable expansion complex remain undifferentiated and pluripotent.

Embodiment 19 - The method of embodiment 16, wherein the undifferentiated cells express at least about 80% of each of SSEA-5 and TRA-1-60.

Embodiment 20 - The method of embodiment 16, wherein the undifferentiated cells express at least about 70% of each of Oct-4 and Nanog.

Embodiment 21 - The method of embodiment 16, wherein the undifferentiated cells express at least about 80% of SSEA-5, at least about 80% of TRA-1-60, at least about 70% of Oct-4, and at least about 70% of Nanog.

COMPOSITIONS

[0101] In another aspect, provided herein are suspendable expansion complex compositions comprising human embryonic stem cells, an extracellular matrix component (ECM), and a microcarrier.

[0102] Human embryonic stem cells, extracellular matrices, and microcarriers are described in detail elsewhere herein.

[0103] Expansion complex ranges may vary. In the following tables, the range of the complex components are detailed in different units for the ECM component.

Table 1. [0104] The ECM component can be presented by mol/cm ² by using the laminin 511 E8 fragment’s molecular weight (150 KDa).

Table 2.

[0105] The ECM component can also be presented by the number of molecules/cm ² by using molecular weight (150 KDa) multiplied by Avogadro’s number (6.022xl0 ²³ ).

Table 3.

[0106] In some embodiments, the following specification parameters may be expanded:

# Of hESCs (cells) - 4,000 - 600,000 cells per cm ² of microcarriers

Laminin 511 E8 fragment (pg per cm ² of microcarriers) - 0.125 pg per cm ² or higher.

[0107] In some embodiments, the composition may further comprise a growth medium. Nonlimiting examples of commercially available basic media that may be utilized in accordance with this disclosure comprise NUTRISTEM® (without bFGF and TGF for ESC differentiation, with bFGF and TGF for ESC expansion), NEUROBASAL™, KO-DMEM, DMEM, DMEM/F12, CELLGRO™ Stem Cell Growth Medium, or X-VIVO™. The basic medium may be supplemented with a variety of agents as known in the art dealing with cell cultures. The following is a non-limiting reference to various supplements that may be included in the culture to be used in accordance with the present disclosure: serum or with a serum replacement containing medium, such as, without being limited thereto, knock out serum replacement (KOSR), NUTRIDOMA-CS, TCH™, N2, N2 derivative, or B27 or a combination; an extracellular matrix (ECM) component, such as, without being limited thereto, fibronectin, laminin, collagen and gelatin. The ECM may then be used to carry the one or more members of the TGFI3 superfamily of growth factors; an antibacterial agent, such as, without being limited thereto, penicillin and streptomycin; and non-essential amino acids (NEAA), neurotrophins which are known to play a role in promoting the survival of SCs in culture, such as, without being limited thereto, BDNF, NT3, NT4.

[0108] As described above, the microcarriers may comprise one or more of polystyrene, cross-linked dextran, magnetic particles, microchips, cellulose, hydroxylated methacrylate, collagen, gelatin, polystyrene, plastic, glass, ceramic, silicone. In some embodiments, the microcarrier is composed of polystyrene. In some embodiments, the microcarrier is composed of surface-modified polystyrene. In some embodiments, the microcarrier is composed of chemically modified polystyrene. In some embodiments, the microcarrier is composed of cross-linked dextran. In some embodiments, the microcarrier is composed of cellulose. In some embodiments, the microcarrier is composed of acrylamide. In some embodiments, the microcarrier is composed of collagen. In some embodiments, the microcarrier is composed of alginate. In some embodiments, the microcarrier is composed of gelatin. In some embodiments, the microcarrier is composed of glass. In some embodiments, the microcarrier is composed of DEAE-dextran.

[0109] As described above, the microcarriers may be spherical, smooth, macroporous, rodshaped, or a combination thereof.

[0110] In some embodiments, the microcarriers may be coated with matrigel, laminin, vitronectin, collagen, their derivatives, or a combination thereof. In some embodiments, the laminin is human laminin 511.

[0111] In some embodiments, the microcarriers are not coated.

[0112] In some embodiments, the microcarriers have a surface area of 25 cm ² to 7,500 cm ² , e.g., about 25 cm ² , 50 cm ² , 75 cm ² , 100 cm ² , 125 cm ² , 150 cm ² , 175 cm ² , 200 cm ² , 225 cm ² , 250 cm ² , 500 cm ² , 625 cm ² , 750 cm ² , 1,000 cm ² , 1,250 cm ² , 5,000 cm ² , or 7,500 cm ² . The surface area may be any value or subrange within the recited ranges, including endpoints. [0113] In some embodiments, the microcarriers are coupled with protamine or polylysine. In some embodiments, the microcarriers are neutral. In some embodiments, the microcarriers are negatively charged. In some embodiments, the microcarriers are hydrophilic.

[0114] It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.

Additional Embodiments

[0115] The present disclosure provides the following illustrative embodiments.

Embodiment 22 - A suspendable expansion complex composition comprising human embryonic stem cells, an extracellular matrix component (ECM), and a microcarrier.

Embodiment 23 - The composition of embodiment 22, further comprising a growth medium.

Embodiment 24 - The composition of embodiment 22 or 23, wherein the microcarriers comprise one or more of polystyrene, cross-linked dextran, magnetic particles, microchips, cellulose, hydroxylated methacrylate, collagen, gelatin, polystyrene, plastic, glass, ceramic, silicone.

Embodiment 25 - The composition of any of embodiments 22 to 24, wherein the microcarriers are spherical, smooth, macroporous, rod-shaped, or a combination thereof.

Embodiment 26 - The composition of any of embodiments 22 to 25, wherein the microcarriers are coated with matrigel, laminin, vitronectin, collagen, their derivatives, or a combination thereof.

Embodiment 27 - The composition of embodiment 26 wherein the laminin is human laminin.

Embodiment 28 - The composition of embodiment 27, wherein the human laminin is human laminin 511 E8 fragment.

Embodiment 29 - The composition of any of embodiments 22 to 28, wherein the microcarriers are not coated. Embodiment 30 - The composition of any of embodiments 22 to 29, wherein the microcarriers are coupled with protamine or polylysine.

Embodiment 31 - The composition of any of embodiments 22 to 30, wherein the microcarriers are neutral or negatively charged.

Embodiment 32 - The composition of embodiment 31, wherein the microcarriers are neutral.

Embodiment 33 - The composition of embodiment 31 , wherein the microcarriers are negatively charged.

Embodiment 34 - The composition of any of embodiments 22 to 29, wherein the microcarriers are hydrophilic.

EXAMPLES

EXAMPLE 1: METHODS FOR hESC EXPANSION

[0116] Scale-up of hESC production is done on many growth platforms. From growing hESC cell suspension, or attached to 2D flasks such as roller bottles, cell factories or 3D hollowfibers and macro-carriers such as BioNocII, and Fibra Cell discs.

[0117] Fully controlled and closed systems were used for simple mammalian cell growth for many years. Those systems allowed for the manufacturing of large industrial lots of antibodies and proteins. Most of these systems require cells that are inherently grown or were adapted to grow in suspension as single cells. Early attempts to expand hESCs in suspension were not successful as they formed aggregates that tended to lose their pluripotency and spontaneously differentiate. Adaptation to hESC grown as a single cell suspension most of the time compromised genetic stability and caused karyotype abnormalities. Recently such methodology was greatly improved (AMIT Michal, Itzkvitz Eldor Joseph Patent # EP2059586B1, US9040297B2), their innovation is to grow hESCs without adherence to any kind of substrate or coating in serum-free, serum replacement-free, xeno-free, feeder-free and protein carrier-free. That was enabled in part by the addition of a soluble interleukin-6 receptor (sIL6R, >10ng/ml), soluble interleukin-6 (IL6), leukemia inhibitor factor (LIF, 1000- 3000u/ml) as well as bFGF, TGFbl and TGFb3. [0118] Several studies have used microcarriers to grow hESCs cultures. Their properties of being suspended in solution, while providing them with surface for adherent cells to grow on, made them ideal for growing adherent cell culture in a closed and controlled environment. A potential benefit of using microcarriers for large-scale production is that the surface-area-to- volume ratio is greatly increased over traditional static culture processes, so cell density may be increased, and the required footprint reduced.

[0119] Many different types of microcarriers (MCs) are commercially available. MCs can be made from polystyrene such as HyQSphere (HyClone) and Hillex (SoloHill Engineering) brands or made from cross-linked dextran such as the Cytodex brand (GE Healthcare). Although most microcarriers are spherical and smooth, others have macroporous surfaces such as Cytopore brand (GE) and alternatives such as rod-shaped carriers such as DE-53 (Whatman). Additional technological advances include infusion of magnetic particles into the MC that may help in cell separation from beads (GEM particles from Global Cell Solutions) and chip-based microcarriers such as the pH ex product (Nunc) that provide a traditional flat surface for cell growth while maintaining the high surface to volume ratio of traditional microcarriers. Selecting a microcarrier for cell expansion is not a trivial task. Different properties of microcarriers may significantly affect expansion rates, cell pluripotency, ability to perform (in the case of hESCs its ability to differentiate into different lineages), genetic stability, etc. Some surface chemistry modifications can improve cell adhesion. Such methods include applying positive or negative charges and optional coating with extracellular matrix proteins (Lam 2015 BioResearch Open Access Volume 4.1,Cherian 2020 Frontiers in Pharmacology Volume 11 Article 654) .

[0120] First attempts to grow embryonic stem cells (ESC) on microcarriers in stirred suspension were published in 2005-2007 (Fok et al Stem Cells 2005; 23:1333-1342, Abranches et al Biotechnol. Bioeng. 96 (2007), pp. 1211-1221, and Stefanie Terstegge & Oliver Brustle US20070264713A1). Expansion and passaging of hESC onto MC was demonstrated in 2009 using Cytodex 1, 3 and Solohil Plastic, Plastic plus and Hillex II (Nelson, Janssen Biotech Inc, US20180265842A1, US9969972B2) including their differentiation to definitive endoderm and pancreatic cells on MCs, or cardiomyocytes (Oh et al. EP2479260B1). Most of the developed processes included the coating of MCs with Matrigel, in some cases Laminin, or Vitronectin was used as coating of MC precoated with collagen. One study performed the hESC expansion in a controlled environment using the Synthemax® II coated MC (Corning, Silva 2015). The main conditions and results of these studies are summarized in Table 4. Those studies did not yet advance to large vessels, but in general they established comparable results to standard practice in static flasks. But the next step toward large scale production in controlled environment is yet to be made prior to the present disclosure.

Table 4. Known hESC and iPSC scale up studies using microcarriers.

[0121] GMP grade feeder free and serum free hESCs banks were previously generated from clinically approved hESCs lines (HADC102, Hl). Here, hESCs were propagated for several passages on uncoated flasks by adding the iMatrix-511 -E8 (No.2009-234583/PCTJP2010- 067618/W02011-043405, Miyazaki et al. 2012 Nat Commun. 2012 Dec 4; 3: 1236) synthetic fragment to the seeding solution. This methodology was used for a scale-up of hESC culturing on MCs for development of a scale up process. In a proof of concept study, hESCs (Hl) were cultured on non-adherent T25 flasks in mTeSR plus media supplemented with iMatrix-511-E8 - 0.125p.gr/cm ² using Synthemax® II or Enhanced Attachment (Coming) MC.

[0122] The combination of human laminin 511 as a coating, specifically iMatrix-511-E8 (synthetic fraction of laminin 511), with those specific two MCs (others were tested in the POC study and failed) in suspension, to allow for expansion of hESCs in a culturing system, allows for scale up. Human laminin 511, specifically iMatrix E8, was used here for the first time for coating MCs in a scaled up system. Former publications teach about culturing hESCs on laminin coated tissue culture, or about hESC culturing on different MCs with a variety of substrates covering in general all protein matrices (Matrigel, collagen, gelatin, vitronectin, laminin, or their derivatives or combinations).

[0123] This combination, as detailed above, makes the transfer to large scale much easier and linear when intending to use single-use bioreactors for hESC expansion.

[0124] As an additional point, the coating procedure was done using the high specificity of iMatrix 511 E8 to hESCs, it was used not as an agent for pre-coating the substrate before cell seeding, rather, by simplifying the process and adding this agent directly to the cell suspension before contact with the MCs. Thus, when cells are seeded, the MCs are not pre-coated, but having the iMatrix 511 E8 in the seeding solution enhances their specific attachment to those specific MCs.

[0125] Under current standard practices, microcarriers are coated before cell inoculation. The duration of the pre-coating step is highly variable, from 4 hrs at 37°C to one month at 4°C, and it is difficult to control the coating procedure to be even upon all the surfaces, as MCs get compact in long static incubation and some of the surface is less accessible to coating as it is in contact with neighboring beads. A complete removal of the coating solution is needed before the equilibration step to the MCs in the growth media before MC equilibration and cell inoculation. The coating removal step is risky due to the sensitivity of the laminin coating to low humidity. If the laminin gets dry, it changes its adhesive properties. In a scaled-up system, with large volumes, this step is critical as it may not only affect the number of seeded cells; it can change the cell properties.

The innovation of the present disclosure over hESC expansion systems and techniques heretofore described is the combination or inoculation of ingredients in a single step which allows for a convenient inoculation of the hESC scaled-up system. In particular, the systems and methods described herein include the single step seeding step as described above, namely, (a) simultaneously combining human embryonic stem cells, an extracellular matrix component (ECM), and a microcarrier in growth media to form a suspendable expansion complex, and (b) culturing the suspendable expansion complex for a period of time. For example, by mixing all relevant materials together for inoculating the scaled-up system (the specific MC type, iMatrix511 E8 with cells), with no need to do pre-coating and then another step of seeding. That also includes the expansion of hESCs in a closed and controlled environment under GMP conditions. The specific combination of those materials for the scaled-up system, allows for easy and safe GMP translation.

Results

[0126] Seeding was done for 2 hrs. at 20,000 cells/cm ² on Synthemax® II or Enhanced Attachment (Coming) MC in a non-treated T25 (Coming). At the end of the seeding step, 8 ml of mTeSR plus was added. 80% of the media was replaced every 24 hours and lactate levels and cell morphology (Figure 1 and Table 6) were monitored. Harvesting was done on the 4 ^th day after seeding using TrypLE Select. Cells were filtered through a 70 pm strainer to remove the MCs. Cells were cryopreserved in CS10. Pluripotency of thawed cells was assessed (Table 5, SSEA- 5/TRA-1-60, Oct4/Nanog) after follow-up passage (P2) on TC treated flasks.

[0127] The results of the study as summarized in Table 6 indicate that efficient hESC expansion on MCs was achieved without reducing cell pluripotency (SSEA-5/TRA-1-60 >98%, % Oct- 4/Nanog >84%) and self-renewal (population doublings (PDL) in P 1 ~4, P2 ~3) for both MC types. Table 5. Pluripotency of hESCs grown for 1 passage on MC.

Table 6. Summary of passaging data for the experiments described herein.

EXAMPLE 2: MANUFACTURING CAPABILITY AND SCALE-UP PLAN

[0128] A fully integrated team would include PD, QC, QA, and manufacturing. World experts in PSC technology guided the differentiation of cells to specific functional lineages. There would be an experienced team for process development, formulation and large-scale production in bioreactors using microcarriers. In-house specialized cGMP production capabilities include 1) two independent clean rooms; 2) bioreactor cell production (currently 5 billion cells per batch); and 3) fill/finish capabilities.

EXAMPLE 3: SYSTEM FOR SCALING UP hESC EXPANSION

[0129] As described above, the combination of ingredients in a single step allows for the convenient inoculation of the hESC scaled-up system in accordance with the teachings of the present disclosure. Under the current standard practice, microcarriers are coated before cell inoculation. The duration of the pre-coating step is highly variable, from 4 hrs at 37°C to a month at 4°C, and it is difficult to control the coating procedure to be even upon all the surfaces, as MCs get compact in long static incubation and some of the surface is less accessible to coating as it is in contact with neighboring beads. A complete removal of the coating solution is needed before the equilibration step to the MC in the growth media before MC equilibration and cell inoculation. The coating removal step is risky due to the sensitivity of the laminin coating to low humidity. If the laminin gets dry it changes its adhesive properties. In a scale- up system, with large volumes, this step is critical as it may not only affect the number of seeded cells, but it can also change the cells’ properties.

[0130] The innovation of the present disclosure includes the seeding step as mentioned above, mixing all relevant materials together for inoculating the scaled-up system (the specific MC type, iMatrix-511 E8 with cells), with no need for pre-coating and an additional step of seeding. That also includes the expansion of hESCs in a closed and controlled environment under GMP conditions. The specific combination of these materials for the scale-up system, enables easy and safe GMP translation.

[0131] The process presented here (Figure 3), involves thawing and expansion of hESCs as a traditional feeder-free 2D culture. Then hESCs are harvested and seeded directly in the hESCs expansion scaled-up system on MCs with iMatrix-511 E8 supplemented to the medium. At the end of hESCs expansion in the scaled-up system, the harvested cells can be cryopreserved as a hESC pluripotent bank for further expansion and/or continue directly to initiate differentiation. [0132] For evaluation of cell growth, several parameters can be evaluated -

1) Lactate measurements - increase in lactate concentration in media along culturing is linear to # of live cells during hESC culturing.

2) Morphological assessment - Clumps of beads observed during hESC expansion in the scale-up system reflect cell growth in culture.

3) Passaging parameters - harvesting density (live cells/cm ² ) of cells in addition to yield parameters.

[0133] Other hESC characterization methods were used to evaluate the harvested cells from the hESC expansion scale-up system -

1) Pluripotency markers expression - cryopreserved harvested cells from the hESCs expansion scale-up system culturing were stained for four well-known pluripotency markers (SSEA-5/TRA-1-60, Oct-4/Nanog) and analyzed by flow cytometry. High expression of these markers affirmed the identity and pluripotency state of the harvested cells from the hESC scale-up culturing system.

2) Karyotype analysis - during development runs, cells were cultured after harvesting from the hESCs scale-up culturing system and fixed. The cell karyotype was tested by the Giemsa banding method to ensure genetic stability.

Culturing of hESCs on several types of MCs

[0134] hESCs were harvested from T-flasks and seeded in one inoculation step on several types of MCs with iMatrix-511 E8 supplemented to seeding medium. Cells were cultured for 4 days passage in the hESCs scale-up system. The MC types evaluated in the hESC expansion scale-up system are detailed in the Table 7. In addition, culturing hESCs on other types of micro and macro carriers (Pall Solohill Star-Plus, Pall Solohill HillexOII, Pall Solohill Plastic, Pall Solohill Plastic Plus, ESCO BioNOC II, CelliGen Fibracell Disks, Advanced Biometrix SphereColOType I Collagen Coated Beads, Cytodex® 3) was tested (data not shown). These micro and macro carriers were not continued after a first screening of MCs.

Table 7. MCs tested in the hESCs expansion scale-up system.

[0135] Morphology assessment of the hESC expansion scale-up system from both groups presented in Table 7 is presented in Figure 4.

[0136] Lactate elevation in culture media between days 2 to 4 in addition to harvesting density, yield and expression of pluripotency markers in cells one passage post culturing in the hESC expansion scale-up system are presented in Table 8.

Table 8. Culturing parameters and pluripotency marker expression of cells cultured in the hESC scale-up system.

[0137] Morphology assessment of harvested cells seeded for further culturing is presented in Figure 5. Cells are showing typical hESC morphology - organized as colonies of compact cells with a high ratio of nucleus to cytoplasm.

[0138] Cells were successfully cultured on Coming Synthemax® II and on Corning Enhanced Attachment MCs under hESC expansion scale-up system conditions and produced pluripotent hESCs.

Harvesting method prior to inoculation of hESC expansion scale-up system

[0139] The full process, as presented in Figure 3, involves culturing of hESCs as a 2D culture before inoculation to the hESC expansion scale-up system. Two harvesting methods from a traditional feeder-free 2D culture (non-enzymatic - results in small clumps of cells, and enzymatic - results in single cells) were used, before hESC expansion scale-up system inoculation. Both harvesting methods were tested on both types of MCs mentioned above. Groups are presented in Table 9.

Table 9. Tested conditions (combination of MCs type and harvesting reagent prior to inoculation) in the hESC scale-up system.

[0140] Morphology assessment of the hESC expansion scale-up system culturing Table 9 is presented in Figure 6. In addition, culturing parameters and pluripotency marker expression of cells from all groups are presented in Table 10.

Table 10. Culturing parameters and pluripotency marker expression of cells cultured in the hESC scale-up system.

[0141] Expression of pluripotency markers (>86% positive for all tested markers), lactate concentration elevation during culturing, added to harvesting density and yield showed that harvesting cells before inoculation in the hESC expansion scale-up system was accomplished with ReLeSR as well as with TrypLE Select. Both methods are suitable for hESC harvesting prior to inoculation in the hESC expansion scale-up system.

[0142] Both MCs (Corning Synthemax® II and Corning Enhanced attachment) and both harvesting methods (ReLeSR and TrypLE Select) are suitable for the hESC expansion scale- up system. Moreover, based on the data shown above, it is rational to assume that culturing hESCs harvested with TrypLE Select from MCs and seeded for additional passage in the hESC expansion scale-up system is feasible.

Culturing platforms for the hESC expansion scale-up system

[0143] Expansion of hESCs in the hESC expansion scale-up system was tested in different culturing platforms and in different working volumes and MC surface areas. Examples for several culturing platforms are presented in Table 11. Table 11. Platforms for culturing in the hESC scale-up system.

[0144] Morphology assessment of the hESC expansion scale-up system from the platforms in Table 11 is presented in Figure 7.

[0145] Culture growth was assessed by measuring lactate concentration along culturing. In addition, harvesting density and yield were calculated. The identity and pluripotency of hESCs was evaluated at the end of culturing by flow cytometry analysis of pluripotency marker expression. In addition, during development, the karyotype of the harvested cells from the hESC expansion scale-up system was tested. Results are summarized in Table 12. Table 12. Culturing parameters and pluripotency marker expression of cells cultured in the hESC scale-up system.

[0146] Growth of hESCs in the hESC expansion scale-up system was accomplished in several culturing vessels (non-treated T25, 0.1L PBS wheel, 0.5L PBS wheel, 3L PBS-MAG) in different MCs surface areas (25 cm ² , 125 cm ² , 250 cm ² , 625 cm ² , 1,250 cm ² and 7,500 cm ² ) and working volumes (10 mL, 50 mL, 100 mL, 250 mL, 500mL, 3,000 mL). Culturing in the hESC expansion scale-up system led to maintenance of very high expression of pluripotency markers even after changing the culturing vessels and conditions. iMatrix-511 E8 concentration for efficient inoculation

[0147] The hESC expansion scale-up system inoculation was performed with two iMatrix- 511 E8 concentrations. The conditions tested and cell growth (assessed by increase in lactate concentration between days 2 and 4 of 4 days passage, and by cells-MCs clumps formation) are summarized in Table 13 and in Figure 8.

Table 13. iMatrix-511 E8 concentration during inoculation in the hESC scale-up system.

[0148] Expansion of hESCs in the hESC expansion scale-up system was accomplished when using 0.125 and 0.250 ug/cm ² of iMatrix-511 E8 during inoculation. Moreover, based on the data shown above, it can be projected that iMatrix-511 E8 concentration of 0.125-0.250 ug/cm ² will result in efficient growth of hESCs in the hESC expansion scale-up system.

Passage duration of hESCs on MCs in the hESC expansion scale-up system

[0149] To allow flexibility for hESC culturing in the hESC expansion scale-up system, 4- and 5-day passages were evaluated. Adjustment of hESC seeding density for different passage durations was performed. Comparison of harvesting density, lactate at harvesting, morphology and pluripotency marker expression of hESCs harvested post 4-day passage (group 5.1) and 5- day passage (group 5.2) is presented in Table 14 and in Figure 9. Morphology assessment and lactate at harvesting showed similarity between 4- and 5-day passage culturing. In addition, pluripotency marker expression was high in both groups (>89% for all markers).

Table 14. Culturing parameters and pluripotency markers expression of cells cultured in hESCs scale-up system. [0150] For both the 4- and 5-day passage duration, hESC culturing in the hESC expansion scale-up system was accomplished. By adjusting the seeding density according to passage duration, hESC cultures reached similar lactate concentration and harvesting density. Moreover, by adjusting the seeding density, culturing hESCs on MCs in the hESC expansion scale-up system can be accomplished for 3-7 day passages.

Cryopreservation of the hESC bank from cells cultured in the hESC expansion scale-up system

[0151] Harvested cells from the hESC expansion scale-up system were cryopreserved. Then, thawed cells were tested for pluripotency marker expression and seeded for further culturing as a 2D traditional feeder-free culturing. The thawed cells showed high pluripotency marker expression (Table 15) in addition to maintaining hESC morphology post culturing in the hESC expansion scale-up system. Culturing parameters in the hESC expansion scale-up system and pluripotency marker expression are presented in Table 15. Morphology of cells during culturing on MCs in the hESC expansion culturing system in addition to 2- and 5-day post thawing and seeding on 2D feeder-free traditional flasks for follow-up are presented in Figure 10.

Table 15. Culturing parameters and pluripotency marker expression of cells cultured in the hESC scale-up system.

[0152] Cryopreservation of the hESC bank from the hESC expansion scale-up system cells was accomplished. Cells showed high expression of pluripotency markers (>95% positive for all tested markers) in addition to maintaining hESC typical morphology as a 2D culture after re-seeding of the thawed cells.

Further culturing of harvested cells from the hESC expansion scale-up system as 2D hESC culture

[0153] Harvested cells from the hESC expansion scale-up system can be further expanded as a hESC 2D culture. In the following example, cells harvested from the hESC expansion scale-up system were further cultured as a 2D feeder-free traditional culturing. Culturing parameters (lactate at harvesting) in addition to morphology of cells cultured in the hESC expansion scale-up system and as 2D culture for 2 consecutive passages are presented in Table 16 and in Figure 11.

Table 16. Culturing parameters and pluripotency marker expression of cells cultured in the hESC scale-up system and further passaged as 2D culture.

[0154] Harvested cells from the hESC expansion scale-up system showed high pluripotency marker expression (>94% for all tested markers). In addition, typical morphology of hESCs was observed in culture in both 2D further passages. Further culturing of harvested cells from the hESC expansion scale-up system on iMatrix-511 E8 direct coated flasks was accomplished. Differentiation of harvested cells from the hESC expansion scale-up

[0155] The main characteristic of pluripotent stem cells is the potential to differentiate into all three germ layers. Harvested cells from the hESC expansion scale-up system were seeded and differentiated into dendritic cells according to established protocol. Dendritic cell marker expression at the end of differentiation is presented in Table 17.

Table 17. DC marker expression of cells derived from harvested cells from the hESC scale-up system.

[0156] Morphology assessment of cells along dendritic cells differentiation process is presented in Figure 2.

[0157] Differentiation of cells harvested from the hESC expansion scale-up system into dendritic cells was accomplished efficiently. Differentiation of harvested cells from the hESC expansion scale-up system into any lineage and cell type can be assumed to be enabled from the hESC expansion scale up system cells with or without harvesting.