WO2012103098A2 - Compositions and methods for treating hematological cytopenias - Google Patents

Abstract

The present disclosure provides for ESC-derived compositions and methods of using same in the treatment of hematological cytopenias. An ESC population is selected that is a deliberate immunological mismatch to the intended recipient. Culture conditions promote further antigenicity. When transplanted, the ESC- derived cells restore the patient's blood cell populations on a temporary basis until they reach the end of their lifespan or are cleared by the patient's recovering adaptive immune system.

Description

COMPOSITIONS AND METHODS FOR TREATING HEMATOLOGICAL CYTOPENIAS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 61/435,522, filed January 24, 201 1, and of U.S. Provisional Patent Application No. 61/435,525, filed January 24, 201 1, the contents of both of which are hereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

[0002] The present disclosure relates to the field of oncology. Specifically, the disclosure provides for compositions and methods that treat cytopenia incident to chemotherapy and radiation exposure.

BACKGROUND

[0003] Systemic chemotherapy given for various solid and hematological cancers targets non-specifically all rapidly dividing cells. As a result, destruction of the rapidly dividing compartment of blood cell progenitors is one of the most serious side-effects of chemotherapy. This renders the patient anemic, thrombocytopenic, and most importantly neutropenic (due to the short life span of the neutrophils).

[0004] Neutropenia can be treated with partial success with drugs based on the hormone granulocyte-colony stimulating factor (GCSF). These drugs act on hematopoietic stem and progenitor cells, instructing them to recover and differentiate faster. However, because most of these cells are destroyed by myelotoxic insults, GCSF can at best achieve a modest acceleration of recovery of myelopoiesis. There is no complete expert consensus on whether GCSF extends survival under all circumstances. Accordingly, there remains a need in the art for improved treatment methods, which restore cell count and immune system competency.

SUMMARY

[0005] In one aspect, the invention features a method of producing a substantially purified population of CFCs comprising: obtaining a substantially purified population of hESCs; culturing the population of hESCs under conditions that promote hematopoietic differentiation of the hESCs; and isolating from the culture a substantially pure population of CFCs, wherein the CFCs are clonally identical.

[0006] In some embodiments, the hESCs are cultured on mouse fibroblasts. In other embodiments, the hESCs are cultured on human fibroblasts.

[0007] In some embodiments, the population of hESCs are cultured in a knockout- DMEM culture medium. In other embodiments, the population of hESCs are cultured in a hESCgro medium. In yet other embodiments, the population of hESCs are cultured in an mTESRl or equivalent feeder-free culture medium.

[0008] In other embodiments, the population of hESCs are cultured in a culture vessel coated with Matrigel or an equivalent pluripotency-supporting substrate.

[0009] In certain embodiments, hematopoietic differentiation is determined by the presence of embryoid body formation.

[0010] In some embodiments, differentiation involves exposing the embryoid bodies to one or more mesoderm-inducing cytokines. In some embodiments, the cytokine is presented to the embryoid bodies over a period of about 3, about 4, about

5, about 6, about 7, about 8, about 9, about 10, about 1 1, about 12, about 13, about

14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, or about 30 days. In particular embodiments, the cytokine is BMP-4, VEGF, bFGF, Activin A, IL-3, or a combination thereof.

[0011] In other embodiments, differentiation involves exposing the embryoid bodies to one or more hematopoietic cytokines. In some embodiments, the cytokine is presented to the embryoid bodies over a period of about 3, about 4, about 5, about

6, about 7, about 8, about 9, about 10, about 1 1, about 12, about 13, about 14, about

15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, or about 30 days. In particular embodiments, the cytokine is SCF, FLT3L, TPO, GCSF, IL-3, IL-6, or a combination thereof.

[0012] In yet other embodiments, differentiation is effectuated by coculturing the population of hESCs with a stromal cell line. In some embodiments, the method further comprises selecting the stromal cell line from a pool of potential stromal cell lines by determining which line instructs the highest numbers of CFC or CD34+ cells.

[0013] In some embodiments, the stromal cell line is a human stromal cell line. In particular embodiments, the stromal cell line is HS5.

[0014] In other embodiments, the stromal cell line is OP9.

[0015] In some embodiments, the hESCs are from an embryonic stem cell line. In other embodiments, the hESCs are from an induced pluripotent stem cell line.

[0016] In certain embodiments, the hESCs are induced to form a CD34+ cell. In other embodiments, the hESCs are induced to form a granulocyte population.

[0017] In yet other embodiments, the isolating step comprises magnetic cell separation. In other embodiments, the isolating step comprises sterile flow cytometry sorting. In yet other embodiments, the isolating step comprises density gradient centrifugation.

[0018] In certain embodiments, the isolating step comprises using CD34 antigen for purification. In other embodiments, the isolating step comprises using CD38 antigen for purification. In yet other embodiments, the isolating step comprises using CD41 antigen for purification.

[0019] In another aspect, the invention features a method of treating a cytopenia comprising: identifying a subject having a cytopenia; obtaining a population of hESCs; culturing the population of hESCs to obtain a substantially pure population of CFCs; and transplanting the population of CFCs to the subject thereby treating the cytopenia.

[0020] In some embodiments, the subject has a cytopenia due to chemotherapy. In other embodiments, the subject has a cytopenia due to radiation exposure. In certain embodiments, the subject has a cytopenia due to chemical weapons exposure. In other embodiments, the subject has a cytopenia due to accidental chemical exposure. In yet other embodiments, the subject has a congenital cytopenia, for example a neutropenia.

[0021] In certain embodiments, prior to transplanting the population of CFCs, the subject's immune system is attenuated by about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90%, relative to a normal subject's immune system. In particular embodiments, prior to transplanting the population of CFCs and after chemotherapy, radiation exposure, chemical weapons exposure, or accidental chemical exposure, the subject's immune system is attenuated by about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90%, relative to the subject's immune system level prior to chemotherapy, radiation exposure, chemical weapons exposure, or accidental chemical exposure.

[0022] In some embodiments, the subject's immune system is not attenuated prior to transplanting the population of CFCs. In other embodiments, the subject's immune system is attenuated by about 100% prior to transplanting the population of CFCs.

[0023] In some embodiments, transplanting the population of CFCs restores the subject's neutrophil counts to substantially normal ranges. In other embodiments, transplanting the population of CFCs restores the subject's number of transient amplifying cells to substantially normal ranges.

[0024] In certain embodiments, transplanting the population of CFCs provides prophylaxis for infection. In other embodiments, transplanting the population of CFCs treats an existing infection.

[0025] In some embodiments, the method further comprises screening the hESCs for an intrinsic bias to differentiate into mature blood cell types.

[0026] In some embodiments, the CFCs persist within the subject for less than about 6 months, less than about 5 months, less than about 4 months, less than about 3 months, less than about 2 months, less than about 1 month, less than about 3 weeks, less than about 2 weeks, or less.

[0027] In another aspect, the invention features a method of treating a cytopenia comprising: identifying a subject having a cytopenia; obtaining a population of hESCs that are allogeneic to the subject; culturing the population of hESCs to obtain a substantially pure population of CFCs; and transplanting the population of CFCs to the subject thereby treating the cytopenia.

[0028] In some embodiments, the hESCs are immunologically incompatible with the subject. In certain embodiments, the immunological incompatibility comprises one or more human leukocyte antigen mismatches. [0029] In some embodiments, the immunological incompatibility with the subject is enhanced. In particular embodiments, the method further includes culturing the hESCs on non-human embryonic fibroblasts, such that non-human peptides or glycans become incorporated in the hESCs or their derivatives. In certain other embodiments, the method further includes differentiating the hESCs into colony forming cells. In particular embodiments, the differentiating step includes coculturing the hESCs with a non-human marrow stromal cell line. In certain embodiments, the coculturing step incorporates non-human peptides or glycans into the human colony forming cells.

[0030] In certain embodiments, prior to transplanting the population of CFCs, the subject's immune system is reduced by about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90%, relative to a normal subject's immune system. In particular embodiments, prior to transplanting the population of CFCs and after chemotherapy, radiation exposure, chemical weapons exposure, or accidental chemical exposure, the subject's immune system is reduced by about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90%, relative to the subject's immune system level prior to chemotherapy, radiation exposure, chemical weapons exposure, or accidental chemical exposure.

[0031] In some embodiments, the subject's immune system is not attenuated prior to transplanting the population of CFCs. In other embodiments, the subject's immune system is attenuated by about 100% prior to transplanting the population of CFCs.

[0032] In another aspect, the invention features a population of CFCs produced using any method described herein.

[0033] In another aspect, the invention features a cellular transplant comprising a population of CFCs produced using any method described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present teachings described herein will be more fully understood from the following description of various illustrative embodiments, when read together with the accompanying drawings. It should be understood that the drawings described below are for illustration purposes only and are not intended to limit the scope of the present teachings in any way.

[0035] FIGS. 1A, IB, and 1C are graphical representations of the administration of therapeutic hESCs and a patient's immune system over time.

DETAILED DESCRIPTION

[0036] All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

[0037] The disclosure includes ESC-derived compositions and methods of using same in the treatment of cytopenias. An ESC population can be selected that is a deliberate immunological mismatch to the intended recipient. Culture conditions can be selected to promote further antigenicity. When transplanted into a subject, the ESC-derived cells can restore the subject's blood cell populations on a temporary basis until they reach the end of their lifespan or are cleared by the patient's recovering adaptive immune system.

Definitions

[0038] The articles "a" and "an" are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0039] As used herein, "purified" (or "isolated") refers to a cell, e.g., a CFC, that is removed or separated from other components present in its natural environment. For example, an isolated cell is one that is separated from other components of a population of cells, e.g., cell culture. An isolated cell can be at least 60% free, or at least 75% free, or at least 90% free, or at least 95% free from other components present in the natural environment or cell culture of the indicated cell. [0040] In accordance with the present disclosure, there may be employed conventional molecular biology, microbiology, and recombinant DNA techniques within the skill of the art. Such techniques are described in the literature (see, e.g., Sambrook, Fritsch & Maniatis (ibid.); DNA Cloning: A Practical Approach, Volumes I and II (D. N. Glover ed. 1985); Oligonucleotide Synthesis (M. J. Gait ed. 1984); Nucleic Acid Hybridization (B. D. Hames & S. J. Higgins eds. (1985)); Transcription And Translation (B. D. Hames & S. J. Higgins, eds. (1984)); Animal Cell Culture (R. I. Freshney, ed. (1986)); Immobilized Cells and Enzymes (IRL Press, (1986)); B. Perbal, A Practical Guide To Molecular Cloning (1984); F. M. Ausubel et al. (eds.), Current Protocols in Molecular Biology. John Wiley & Sons, Inc. (1994).

Hematopoietic Differentiation

[0041] Blood cell formation, also known as hematopoiesis, is a hierarchical process by which the hematopoietic stem cells (HSCs) give rise to committed hematopoietic progenitor cells (HPCs) that are capable of generating the entire repertoire of mature blood cells over the lifetime of an organism. HSCs are functionally defined by their capacity for self-renewal, to maintain or expand the stem cell pool; multi-lineage differentiation, to generate and/or regenerate the mature lympho-hematopoietic system; and ultimately to home to the appropriate microenvironment in vivo where, through self-renewal and multi-lineage differentiation, they can restore normal hematopoiesis in a myeloablated host. As HSC differentiate they give rise to committed hematopoietic progenitor cells with limited self-renewal capacity and an increasingly restricted lineage potential. The earliest HSC cell-fate decision involves differentiation into either the lymphoid or myeloid lineage, establishing the major divisions of lympho-hematopoietic system. This differentiation step involves loss of self-renewal, a stem cell characteristic. The lineage-committed cells are referred to as progenitors, and are bound to become mature blood cells after a limited number of cell divisions. Due to their ability to form colonies made up of mature blood cells in methyl cellulose based media, these cells are also called colony-forming cells (CFC), or colony-forming units (CFU). They can be classified according to the types of mature cells that show up in the methyl cellulose assay, for example as CFC Granulocyte, Erythrocyte, Macrophage, Megakaryocyte (CFC-GEMM), CFC Granulocyte Macrophage (CFC-GM) or CFC Granulocyte (CFC-G). For example, the progenitors are plated in methyl cellulose, in the presence of hematopoietic cytokines, such as Stem Cell Factor, FLt3-ligand, Interleukin-3, Interleukin-6, GCSF, Thrombopoietin and Erythropoietin. Under the influence of the cytokines, the progenitors can expand to form visible colonies of blood cells, such as red blood cells, granulocytes and macrophages.

[0042] The colony-forming cells can be almost entirely contained in the cell population positive for the hematopoietic progenitor marker CD34. These cells can be obtained, e.g., from adult bone-marrow or umbilical cord blood. However, due to the limited potential and pre-existing commitment of the progenitor cells, these cells may not result in a significant expansion of the total hematopoietic potential.

Rather, CD34 cells obtained from adult bone marrow or umbilical cord blood appear to progress down their natural development path, forming increasing numbers of increasingly specialized colonies. The use of embryonic stem cell-derived CFCs according to the methods described herein addresses the limited proliferation potential of such CFCs.

Embryonic Stem Cells

[0043] The methods and compositions described herein utilize embryonic stem cells, e.g., human embryonic stem cells (hESCs). 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. In certain methods for the isolation of human ES cells, the zona pellucida can be removed from the blastocyst and the inner cell mass (ICM) can be isolated by immunosurgery, 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 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 1-2 weeks. Further methods are described in, e.g., Thomson et al, Curr. Top. Dev. Biol. 38: 133 (1998);

Thomson et al, Science 282: 1 145 (1998); Bongso et al, Hum. Reprod. 4:706 (1989); and U.S. Pat. No. 5,843,780.

[0044] Embryonic stem cells can also be obtained commercially, e.g., from the NIH human embryonic stem cells registry (NIH, Bethesda, Maryland). Non-limiting examples of commercially available embryonic stem cell lines are BG01, BG02, BG03, BG04, CY12, CY30, CY92, CY10, TE03, TE32, and WA09 (H9). The selection of useful hESCs is within the level of one of ordinary skill in the art and is not limiting to the present disclosure.

Cell Culture Methods

[0045] Several methods for instructing hematopoietic CFC fate in embryonic stem cells are known in the art (see, e.g., Orlovskaya et al, Methods 45(2): 159-67 (2008)). Two nonlimiting methods for doing so include embryoid body formation and stromal cell coculture. For embryoid body formation, hESCs are allowed, or forced, to aggregate in 3 -dimensional suspension culture. Then, their differentiation can be influenced using, e.g., cytokine cocktails.

[0046] For stromal cell coculture, hESCs can be grown on a layer of cells ("feeder cells") to support the growth of ESCs. Feeder cells can be normal cells that have been inactivated by gamma-irradiation. In culture, the feeder layer serves as a basal layer and supplies cellular factors without further growth or division of their own (Lim et al, Proteomics2(9): 1 187-1203 (2002)). Nonlimiting examples of feeder layer cells include human diploid lung cells, mouse embryonic fibroblasts and Swiss mouse embryonic fibroblasts, but can be any post-mitotic cell that is capable of supplying cellular components and factors that are advantageous in allowing optimal growth, viability and expansion of stem cells. For example, cells can be cultured from known hematopoietic sites (aorta-gonad-mesonephros, yolk sac, fetal liver and bone-marrow stromal), in 2 -dimensional, attached culture. This method can exploit the natural ability of the stromal cells to instruct hematopoietic cell fate. The stromal cells can produce hematopoietic cytokines and/or direct cell-cell contacts that promote hESC hematopoietic differentiation. Specific, exemplary stromal lines used for this purpose include murine OP9 and S17 lines (bone marrow) (Collins et al, J. Immunol. 138: 1082-1087 (1987)), C166 (murine yolk sac) (Wang et al., In Vitro Cell. Dev. Biol. Anim., published in 1996, vol. 32, p 292-299), and HS5 (human bone-marrow).

[0047] In general, the cells described herein can be maintained and expanded in culture medium that is available to and well-known in the art. Such media include, but are not limited to, Dulbecco's Modified Eagle's Medium® (DMEM), DMEM F12 Medium®, Eagle's Minimum Essential Medium®, F-12K Medium®, Iscove's Modified Dulbecco's Medium®, RPMI-1640 Medium®, and serum- free medium for culture and expansion of hematopoietic cells SFEM®. Many media are also available as low-glucose formulations, with or without sodium pyruvate.

[0048] In certain embodiments, culture media can be supplemented with sera, such as mammalian sera. Sera often contain cellular factors and components for viability and expansion. Nonlimiting examples of sera include fetal bovine serum (FBS), bovine serum (BS), calf serum (CS), fetal calf serum (FCS), newborn calf serum (NCS), goat serum (GS), horse serum (HS), human serum, chicken serum, porcine serum, sheep serum, rabbit serum, serum replacements and bovine embryonic fluid. It is understood that sera can be heat-inactivated at 55-65 °C if deemed necessary to inactivate components of the complement cascade.

[0049] Additional supplements also can be used to supply the cells with trace elements for optimal growth and expansion. Such supplements include, without limitation, insulin, transferrin, sodium selenium and combinations thereof. These components can be included in a salt solution such as, but not limited to, Hanks' Balanced Salt Solution® (HBSS), Earle's Salt Solution®, antioxidant supplements, MCDB-201® supplements, phosphate buffered saline (PBS), ascorbic acid and ascorbic acid-2-phosphate, as well as additional amino acids. Many cell culture media already contain amino acids, however, some require supplementation prior to culturing cells. Such amino acids include, but are not limited to, L-alanine, L- arginine, L-aspartic acid, L-asparagine, L-cysteine, L-cystine, L-glutamic acid, L- glutamine, L-glycine, L-histidine, L-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine, and L- valine. It is well within the skill of one in the art to determine the proper concentrations of these supplements.

[0050] Hormones also can be included in the cell cultures described herein and include, but are not limited to, D-aldosterone, diethylstilbestrol (DES),

dexamethasone, beta-estradiol, hydrocortisone, insulin, prolactin, progesterone, somatostatin/human growth hormone (HGH), thyrotropin, thyroxine and L- thyronine.

[0051] In certain instances, lipids and lipid carriers can be used to supplement cell culture media, depending on the type of cell and the fate of the differentiated cell. Such lipids and carriers can include, but are not limited to, cyclodextrin (alpha, beta, gamma), cholesterol, linoleic acid conjugated to albumin, linoleic acid and oleic acid conjugated to albumin, unconjugated linoleic acid, linoleic-oleic-arachidonic acid conjugated to albumin and oleic acid unconjugated and conjugated to albumin, among others.

[0052] In certain instances, the cells described herein can be cultured in low-serum or serum-free culture medium. Serum-free medium used to culture cells is described in, for example, U.S. Pat. No. 7,015,037. One exemplary medium is KnockOut™ Serum Replacement (KOSR) (Invitrogen, Grand Island, NY). Such medium can be supplemented with one or more growth factors. Commonly used growth factors include, but are not limited to, bone morphogenic protein, basis fibroblast growth factor, platelet-derived growth factor and epidermal growth factor, Stem cell factor, thrombopoietine, Flt3Ligand and 1 1-3. See, for example, U.S. Pat. Nos. 7,169,610; 7, 109,032; 7,037,721 ; 6,617, 161 ; 6,617, 159; 6,372,210; 6,224,860; 6,037, 174; 5,908,782; 5,766,951; 5,397,706; and 4,657,866.

[0053] Cells in culture can be maintained either in suspension or attached to a solid support, such as extracellular matrix components. Stem cells can require additional factors that encourage their attachment to a solid support, such as type I and type II collagen, chondroitin sulfate, fibronectin, "superfibronectin" and fibronectin-like polymers, gelatin, poly-D and poly-L-lysine, thrombospondin and vitronectin. Hematopoietic stem cells can also be cultured in low attachment flasks.

[0054] To induce hematopoietic fate, growth factors or cytokines known to promote mesodermal and hematopoietic differentiation can be included in the culture media. These cytokines include, e.g., BMP4, VEGF, FGF-1, PDGF, EGF, SCF, FLT-3 ligand (FLT-3L), thrombopoietin (TPO), G-CSF, GM-CSF, CSF-1, interleukins 1-26 (IL-1 to IL-26), erythropoietin, and C-kit ligand. The amount of growth factor or cytokine used in vitro to stimulate stem cell growth and

differentiation varies according to the type of cell population and within the skill of those in the art (see, e.g., Rameshwar et al, Blood 81(2):391-398 (1993); Rich et al, Toxicol. Sci. 87(2):427-441 (2005); U.S. Pat. Nos. 7,354,729, 7,354,730 and 7,666,615.

[0055] Methods of identifying and subsequently separating differentiated cells from their undifferentiated counterparts can be carried out by methods well known in the art, such as based on a specific phenotype, morphological change, cell size, and the complexity of intracellular organelle distribution. In addition, differentiated cells can be identified by their expression of specific cell-surface markers such as cellular receptors and transmembrane proteins. Monoclonal antibodies against these cell-surface markers can be used to identify differentiated cells. Detection of these cells can be achieved through fluorescence activated cell sorting (FACS) and enzyme-linked immunosorbent assay (ELISA). In addition, reverse-transcription polymerase chain reaction, or RT-PCR, also can be used to monitor changes in gene expression in response to differentiation. Whole genome analysis using microarray technology also can be used to identify differentiated cells.

[0056] Stem cell populations can be identified by cell markers using any means known to those of skill in the art, including but not limited to, for example, fluorescently-labeled antibodies directed to the specific cluster of differentiation (CD) antigen. Fluorescence techniques known in the art can be used with the methods described herein. See, for example, Kusser et al, J. Histochem. Cytochem. 51 :5-14 (2003). Other methods of detecting stem cell differentiation can be used with the methods described herein, including for example, the use of a reporter gene (Eiges et al, Curr. Biol. 11 :514-518 (2001)).

[0057] In some instances, the cell marker can be, but is not limited to, fetal liver kinase- 1 (Flkl), smooth muscle cell-specific myosin heavy chain, vascular endothelial cell cadherin, bone-specific alkaline phosphatase (BAP), hydroxyapatite, osteocalcin (OC), bone morphogenetic protein receptor (BMPR), CD4, CD9, CD 14, CD15, CD29, CD41, CD41A, CD59, CD73, CD90, CD105, CD8, CD34, CD34+ Scol+ Lin- profile, CD38, CD44, CD61, CD123 lo, c-Kit, Colony-forming unit (CFU), fibroblast colony- forming unit (CFU-F), Hoechst dye, leukocyte common antigen (CD45), lineage surface antigen (Lin), Mac-1, glycophorin-A (CD235a), 7- aminoactinomycin D (7-AAD), CD38, CD117, CD3, CD19, CD56, Muc-18 (CD 146), stem cell antigen (Sca-1), Stro-1 antigen, Thy-1, collagen types II and IV, keratin, sulfated proteoglycan, adipocyte lipid-binding protein (ALBP), fatty acid transporter (FAT), adipocyte lipid-binding protein (ALBP), Y chromosome, karyotype, albumin, B-l integrin, CD 133, glial fibrillary acidic protein (GFAP), microtubule-associated protein- 1 (MAP-2), myelin basic protein (MPB), nestin, neural tubulin, neurofilament (NF), neurosphere, noggin, 04, 01, synaptophysin, tau, cytokeratin 19 (CK19), glucagon, insulin, insulin-promoting factor- 1 (PDX-1), pancreatic polypeptide, somatostatin, alkaline phosphatase, alpha-fetoprotein (AFP), bone morphogenetic protein-4, brachyury, cluster designation 30 (CD30), crypto (TDGF-1), GATA-4 gene, GCTM-1, genesis, germ cell nuclear factor, hepatocyte nuclear factor-5 (FTNF-4), neuronal cell-adhesion molecule (N-CAM), polysialic acid-neural cell adhesion molecule (PSA-NCAM), Oct-4, Pax6, stage-specific embryonic antigen-3 (SSEA-3), stage-specific embryonic antigen-4 (SSEA-4), stem cell factor (SCF or c-kit ligand), telomerase, TRA-1-60, TRA-1-81, vimentin, MyoD, Pax&, Myogenin, MR4, myosin heavy chain, myosin light chain, CD 150, CD48, ATP-binding cassette superfamily G member 2 (ABCG2), p75 Neurotrophin R (NTR), Musashi homolog 1 (MSI1), SRY (sex determining region Y)-box (SOX) family of transcription factors, Sox2, nanog, CUB domain containing protein 1 (CDCP1), pul transcription factor, twist 1 transcription factor, POU domain class 5 transcription factor 1 (POU5F1), REXl transcription factor, podocalyxin, or telomerase reverse transcriptase (TERT), Otx2, Myo7a or combinations thereof.

[0058] Once differentiated cells are identified, they can be separated from their undifferentiated counterparts using, e.g., FACS, preferential cell culture methods, ELISA, magnetic beads and combinations thereof. For example, FACS can be used to identify and separate cells based on expression of one or more cell-surface antigens described herein. [0059] Once established in culture, cells can be used fresh or frozen and stored as frozen stocks, using, for example, DMEM with 40% FCS and 10% DMSO. Other methods for preparing frozen stocks for cultured cells also are available to those skilled in the art.

Treatment Methods

[0060] The cells described herein, e.g., hESC-derived CFCs, can be used to treat hematological cytopenias (such as accelerate the recovery of neutrophils and transient amplifying cells in the setting of clinical neutropenia) and to prevent infection. One exemplary cytopenia that can be treated is neutropenia.

[0061] By employing hESC-derived CFCs as a cellular transplant, sufficient cell numbers can be achieved to effect short-term myelopoetic reconstitution. Since these cells are differentiated, there is limited proliferative potential of the transplanted cells with limited time persistence of the transplanted cells and their progeny. Advantageously, the transplant is clonally identical, and the design of purposeful immunological incompatibility between the hESC line used and the recipient of the differentiated CFC provides further control over the persistence of the transplant, minimizing the risk of teratoma formation.

[0062] Causes of hematological cytopenias include chemotherapy treatment for cancer, radiation exposure, chemical weapons exposure and congenital defects.

[0063] Myelotoxic insults, such as chemotherapy or radiation exposure, can destroy mixed progenitors and committed progenitors of other blood cell lineages, such as platelets and erythrocytes. Thus, subjects experiencing myelotoxic insults can be in a condition of pancytopenia. These other blood cell progenitors can be characterized by their ability to give rise to colonies of the respective mature blood cell type in vitro, i.e., CFU-Erythrocyte (CFU-E), Blast-forming unit-Erythrocyte (BFU-E) and CFU-Megakaryocyte (CFU-Meg). In one instance, an hESC-derived graft can contain granulocyte progenitors, and also platelet and red cell progenitors in sufficient numbers to ameliorate pancytopenia. Platelet and red-cell CFC can arise as a side-effect of differentiating hESC into neutrophil progenitors, and would naturally be present in a hESC-derived CD34+, CD38+ or CD45+ population, when prepared as described herein. [0064] When using an hESC-derived product for therapeutic purposes, two risks include rejection risk and teratoma risk. Differentiated hESC-derived cells express human leukocyte antigens (HLA). Thus, if HLA mismatched hESC derived cells are given to a subject, an immune response of the recipient against the transplant population can occur. This can typically be prevented by putting the subject on immunosuppression therapy for as long as the therapeutic benefit of the transplant cells is needed. However, this has serious side effects, such as opportunistic infections, and is not desirable for long-term use. An alternative way of preventing rejection includes matching the HLA type of the graft to that of the patient, using techniques such as stem cell line banking, or reprogramming techniques, such as somatic cell nuclear transfer and induced pluripotency. Either of these methods may be preferred to immune suppression therapy, according to circumstances. However, such approaches are complex and costly, and do not ameliorate teratoma risk.

[0065] Attenuating a subject's immune response against a transplanted hESC can increase the risk of teratoma formation. Teratoma are benign cancers containing cells of all three germ-layers. Teratoma can derive from hESC, as well as from their differentiated progeny.

[0066] The methods described herein include the use of HLA-mismatched hESC- derived CFCs as a transient treatment for neutropenia (e.g., resulting from a myelosuppressive insult). Initially, a subject is immunocompromised (e.g., due to the cytotoxic effects of chemotherapy or radiation) and the adaptive immune response is attenuated. Without wishing to be bound by theory, it is believed than an ESC-derived CFC transplant described herein locates to the subject's bone marrow and provides a temporary supply of hematopoietic cells (e.g., neutrophils), e.g., to treat anemia, a clotting disorder, or to fight off infection, during the period when the subject's own immune system is down. Therefore, as long as the subject's adaptive immune response is attenuated (i.e., while the patient requires neutrophil supplementation), there will be no or a relatively low immune response against the ESC-derived graft.

[0067] However, in the course of the ensuing weeks, the subject's adaptive immune system can recover, and it will begin to regain its ability to recognize the transplanted cells as foreign, and reject them. Thus, using the methods described herein, teratoma, which take months to grow, will not have enough time to develop as the transplant cells will be cleared. Any microscopic pre-teratoma lesions or cysts can be rejected by the subject's recovering immune system before they have a chance to grow or cause complications. This will also cause rejection of the graft, which is no longer needed when the subject's own immune system recovers to the point where it can function on its own. Concurrently, the hematopoietic progenitor cells in the graft exhaust their limited hematopoietic potential and come to the end of their life cycle, providing extra assurance that the transplant will disappear before it has a chance to cause problematic teratoma.

[0068] These concepts are further explained and visualized in Figure 1. Figure 1 shows the presence of the cell therapy and a patient's immune function over time. It also explains how tumor formation is reduced or eliminated in the setting of allogeneic therapy in temporarily immunosuppressed patients, such as neutropenic chemotherapy patients.

[0069] In some instances, enhancing immunological rejection of an ESC transplant can provide a means to control transplant cells having longer life cycles, and can serve to increase the safety margin on ESC derived transplants having shorter lifespans. Enhancing immunological rejection of ESCs can be accomplished in a number of ways, which can be employed individually or in combination to achieve the desired degree of immune system provocation.

[0070] First, the probability of immunological rejection of an ESC transplant by the transplant recipient can increase in proportion to the degree of mismatch between the HLA profiles of the ESC and the intended recipient. ESC preparations intended for therapy can be selected such that the ESCs express HLA and other surface antigens that are purposefully mismatched with the recipient subject, for example xenograft ESCs or ESCs of a different ethnicity to the subject.

Mismatching the therapeutic cells with the subject on an HLA basis can be accomplished and also tuned via controlling the number of loci the HLAs are mismatched. Also, as known to medical practitioners, some HLA loci are more or less immunogenic to some individuals than other equally mismatched loci. One nonlimiting example involves using the human embryonic stem cell line HI, which has an HLA code of A2.1, A3.1, B8, B35, Cw4, Cw7, DR1, DR3, DQB2, DQB1. Transplants of this cell line can be given to a subject with, e.g., an HLA code of A2.5, A3.1, B7.2, B 18, Cw7, Cwl2, DR1, DR7, DQB3, DQB1 ; which differs on several loci from the HLA profile of the HI cell line. Without immunosuppressive therapy, the HI derived transplant would be rejected by the recipient after an adaptive immune response was developed.

[0071] Second, an ESC transplant can be prepared by co-culturing, for example, human ESCs with biological materials derived from another species, such as bovine serum or murine cells. Human cells cultured in close association with animal cells or serum can acquire some of the proteins and glycans that are native to the animal cells and not at found on normal human cells. By allowing non-human proteins, peptides and glycans to become incorporated into the human ESCs, the

immunogenicity of the transplant can be increased. For example, human embryonic stem cells can be cultured on mouse embryonic fibroblasts. The hESCs can incorporate N-glycolylneuraminic acid, a glycan found on mouse cells. These hESCs with N-glycoylneuraminic acid can be immunoreactive due to the presence of preexisting antibodies found in human serum. Furthermore, the dose of xeno- derived glycans incorporated into the hESC can be controlled by adjusting relative cell ratios and coculture times. This allows one to fine-tune the degree of immunogenicity of the transplanted cells, from very low to very high. Thus, the degree of immunogenicity of the transplanted cells can be adjusted depending on the length of time the graft is needed for, and the anticipated risk of unwanted transformation.

[0072] Third, the ESCs can be engineered to express immunogenic determinants or immune stimulatory proteins, for example, but not limited to, B-7, LFA-3, MHC Class I or Class II structures. ESCs can be transfected with one or more exogenous genes encoding immunogenic determinants. The transfected ESCs expressing the transgene can then selected, and culture expanded. As a further precaution, a transplant recipient can be vaccinated prior to the transplant, against a HSC specific antigen (exogenous or endogenous), thereby increasing the immune response against the transplant by the recipient. Methods of Administration

[0073] The hESC-derived CFCs described herein can be formulated as

pharmaceutical compositions. Suitable pharmaceutical compositions are known in the art. In particular, methods generally used for the administration of bone-marrow, mobilized peripheral blood, or umbilical cord blood can be used. Generally, a pharmaceutical composition includes a pharmaceutically acceptable carrier, additive, or excipient and is formulated for an intended mode of delivery, e.g., intraperiteneal, intravenous, or intramuscular administration, or any other route of administration described herein. For example, a pharmaceutical composition for intravenous administration can include a physiological solution, such as physiological saline and water, Ringers Lactate, dextrose in water, Hanks Balanced Salt Solution (HBSS), Isolyte S, phosphate buffered saline (PBS), or serum free cell media (e.g., RPMI). The compositions can also include, e.g., antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. The pH of a composition can be adjusted with acids or bases, such as hydrochloric acid or sodium hydroxide.

[0074] Pharmaceutical compositions should be stable under the conditions of processing and storage and must be preserved against potential contamination by microorganisms such as bacteria and fungi. Prevention of contamination by microorganisms can be achieved by various antibacterial and antifungal agents, e.g., antibiotics such as aminoglycosides (e.g., kanamycin, neomycin, streptomycin, and gentamicin), ansaycins, and quinalones.

[0075] The pharmaceutical composition can be formulated to include one or more additional therapeutic agents. For example, a composition can be formulated to include one or more growth factors or cytokines described herein and/or one or more anti-inflammatory agents.

[0076] In some embodiments, any of the pharmaceutical compositions described herein can be included in a container (e.g., a blood storage bag), pack, or dispenser (e.g., a syringe) together with instructions for delivery. [0077] Compositions described herein can be administered in dosages and by techniques well known to those skilled in the medical and veterinary arts taking into consideration such factors as the age, sex, weight, and condition of the particular subject, and the formulation that will be administered (e.g., solid vs. liquid). Doses for humans or other mammals can be determined without undue experimentation by the skilled artisan, from this disclosure, the documents cited herein, and the knowledge in the art.

[0078] The dose of cells to be used in accordance with the methods described herein will depend on numerous factors and may vary for different circumstances. The parameters that will determine optimal doses to be administered for primary and adjunctive therapy generally will include some or all of the following: the disease being treated and its stage; the species of the subject, their health, gender, age, weight, and metabolic rate; the subject's immunocompetence; other therapies being administered; and expected potential complications from the subject's history or genotype. The parameters may also include: whether the cells are syngeneic, autologous, allogeneic, or xenogeneic; their potency (specific activity); the site and/or distribution that must be targeted for the cells/medium to be effective; and such characteristics of the site such as accessibility to cells/medium and/or engraftment of cells. Additional parameters include co-administration with other factors (such as growth factors and cytokines). The optimal dose in a given situation can also take into consideration the way in which the cells are formulated, the way they are administered, and the degree to which the cells/medium will be localized at the target sites following administration. Finally, the determination of optimal dosing necessarily will provide an effective dose that is neither below the threshold of maximal beneficial effect nor above the threshold where the deleterious effects associated with the dose outweighs the advantages of the increased dose.

[0079] The optimal dose of cells for some embodiments can be in the range of doses used for autologous, mononuclear bone marrow transplantation. For fairly pure preparations of cells, optimal doses in various embodiments will range from about 10⁴ to about 10⁸ CFCs per administration. In some embodiments the optimal dose per administration will be between about 10⁵ to about 10⁷ CFCs. The number of cells can be determined using any method known in the art, such as by FACS, a hemocytometer, or other known means.

[0080] A single dose may be delivered all at once, fractionally, or continuously over a period of time. The entire dose also may be delivered to a single location or spread fractionally over several locations. The cells can be administered in an initial dose, and thereafter maintained by further administration. Suitable regimens for initial administration and further doses or for sequential administrations may all be the same or may be variable. Appropriate regimens can be ascertained by the skilled artisan, from this disclosure, the documents cited herein, and the knowledge in the art.

[0081] The disclosure is further illustrated by the following examples. The examples are provided for illustrative purposes only. They are not to be construed as limiting the scope or content of the disclosure in any way.

EXAMPLES

Example 1

[0082] Immortalized human foreskin fibroblasts (hTERT-BJ) were cultured in T- 75 tissue culture flasks under Dulbecco's Modified Eagle's Medium (DMEM) containing 15% Knockout Serum Replacement (KOSR). The medium was changed every three days. When the cells reached confluency, they were washed once with Hank's Balanced Salt Solution without divalent cations (HBSS). Then, the cells were exposed to 0.05% trypsin, 0.5 mM EDTA for 20 minutes, or until the cells begin to detach. Trypsin was removed and the cells were fully detached by repeatedly squirting DMEM at them. The DMEM-containing cell suspension was distributed to an appropriate number (1-8) of new T-75 flasks containing DMEM / KOSR.

[0083] For propagation, the fibroblasts were treated with 10 mg/ml mitomycin C (MITC) in DMEM. The original DMEM solution was removed by aspiration, and 10 ml of MITC-containing DMEM solution was added per T-75 flask. The cells were left in the incubator for 3.5 hours. Then, the cells were washed twice with HBSS, and trypsinized as above. 60,000 MITC-treated hTERT-BJ / cm² were distributed to culture flasks, allowed to attach, and kept in DMEM / 15% KOSR. The next day, the medium was replaced with Knockout-DMEM containing 15% KOSR, lx non-essential amino acids, 0.01% beta-mercaptoethanol and 4 ng/ml basic fibroblast growth factor (bFGF). After one more day in the incubator, the cells were ready for hESC culture.

[0084] Colonies of human embryonic stem cells HI already being cultured with hTERT-BJ were checked for signs of differentiation with a phase contrast microscope. Differentiating colonies were removed manually. Undifferentiated colonies were cut using a stem cell knife (e.g. Invitrogen's EZPassage).

Dissociation of the colony pieces into single cells was avoided as much as possible. The colony pieces were transferred to the new layer of MITC-inactivated hTERT- BJ. They were cultured for 7 days, or until colonies of the original size (1-2 mm) formed again. They were given fresh medium daily.

[0085] Human marrow stromal cell line HS5 was maintained in DMEM containing 20% KOSR. The medium was replaced every three days. Tissue culture dishes were coated with 0.1% gelatin for 1 h at room temperature. When ready for passage, HS5 cells were treated with 0.05% trypsin, 0.5 mM EDTA for 30 minutes or until the cells begin to detach. Trypsin was removed, and the cells were fully detached by repeatedly squirting alpha-MEM at them. Gelatin was removed from the destination T-75 flasks, and the HS5 / DMEM suspension was transferred into the new, gelatin-coated flasks immediately.

[0086] When HS5 was confluent and HI colonies were ready for passage, the medium was changed to DMEM containing 15% KOSR and 0.01% beta- mercaptoethanol (HS5 differentiation medium). HI were passaged as above, and transferred to the HS5 layer as clumps. Half the supernatant was changed to fresh HS5 differentiation medium every other day, or as needed. Phenol-red can be added to the medium to gauge when the medium needs to be replenished. After 9 days, flow cytometry and CFC assays were used to determine the number of CD34+ CFC in the culture. There were approximately 5% CD34+ cells, and 0.5% CFC. The cells were detached from the flasks using Accutase for 5 minutes. Cell clumps were dissociated by tituration to form a single cell suspension. [0087] Then, CD34+ cells were purified by high speed flow cytometry sorting on a BD Influx high speed cell sorter. The single cell suspension was incubated in the dark at 0° C for 20 minutes with 20 uL purified human Fc receptor binding inhibitor (eBioscience Cat # 14-9161-71) per 100 uL of suspension mixture. 5 uL of anti- human CD34 antibody conjugated with fluorescein (eBioscience Cat # 11-0349) was then diluted separately in 45 uL eFluor NC Flow Cytometry Staining Buffer (eBioscience Cat # 00-3222) for each 100 uL of suspension mixture and then combined with the cell suspension in the dark at 0° C for 30 minutes. The sample was purified on the BD Influx according to the manufacturer's instructions. User defined gating specifications qualify target cells and are based on the resolution of fluorescein conjugated mouse-anti-human CD34 antibody fluorescence over mouse IgGl K fluorescein conjugated isotype control (eBioscience Cat # 1 1-4714-41).

[0088] 100,000 CD34+ cells were transferred per well to ultra-low attachment 6- well plates (Corning) in Stemline II medium (Sigma), containing 100 ng/ml SCF, 100 ng/ml FLT3L and 100 ng/ml GCSF. The cells were expanded for 14 days, with a medium change every other day. This results in a shift from early CFCs

(hematopoietic stem cells, hemangioblasts and CFU-GEMM) to late myeloid CFCs (CFU-GM and CFU-G). The CFU composition was monitored by methylcellulose assays in enriched medium (RnD Systems). When maximal expansion of CFU-GM and CFU-G is reached after 14 days, the graft is sorted once again on the Influx for desired markers, such as CD34 (hematopoietic progenitors), CD38 (hematopoietic progenitors enriched for late CFC), CD41 (hematopoietic progenitors enriched for late CFC) or CD45 (late CFC, myelocytes and mature blood cell types).

Alternatively, the graft is used as-is, if a broader distribution of cell types is desired.

[0089] Approximately 100 million CD34+ cells containing 10 million CFC were prepared using this process.

Example 2

[0090] The human embryonic stem cell line HUES-2 (known to have

hematopoietic differentiation bias) was maintained on Matrigel-coated plates in mTESRl . To prepare the Matrigel plates, 1 ml of Matrigel was pipette into 50 ml of HBSS on ice and mixed. 5 ml of the diluted Matrigel solution was spread to cover the entire bottom of a 9 cm Petri dish. The dish was placed in the incubator at 37 °C for 1 hour, and then equilibrated at room temperature for 1 hour. The Matrigel was removed and 15 ml of mTESRl was added.

[0091] HUES-2 colonies in a 9 cm dish (with feeders or an existing mTESRl culture) were treated with Accutase for 3 minutes. The Accutase was removed by careful washing with HBSS. The colonies were detached and broken into pieces using a cell scraper, suspended in a small volume of mTESRl, and transferred to the mTESRl dishes as small clumps. The cells were allowed to attach to the new dishes overnight. mTESRl was replaced daily, until the colonies approach confluence, and which point the cells were passaged again.

[0092] To induce differentiation, cells were passaged as above, and suspended in 20 ml of Knockout-DMEM/F12 (Invitrogen) containing mesodermal cytokines 50 ng/ml BMP-4, 25 ng/ml VEGF(165) and 25 ng/ml IL-3 ("predifferentiation medium"). The predifferentiation medium was replaced after 2 days. After 4 days, the cells were transferred to Stemline II medium (Sigma-Aldrich Corporation) containing hematopoietic cytokines 300 ng/ml SCF, 300 ng/ml FLT3L, 100 ng/ml TPO, 100 ng/ml GCSF, 50 ng/ml IL-3 and 10 ng/ml IL-6 ("differentiation medium"). The differentiation medium was replaced every other day, for a total of 24 days. The culture may be monitored with regular CFC assays, and used when the number of the desired late stage CFC (CFC-G and CFC-GM) peaks. Embryoid bodies were dissociated to form a single cell suspension using Accutase.

[0093] CFC were purified from the resultant suspension using magnetic cell separation. Stem Cell Technologies (Vancouver, BC) EasySep CD34 positive selection kit (Catalog # 18167) was used. 10⁸ cells were suspended in 1 ml of sterile phosphate buffered saline (PBS) containing 2% FBS and 1 mM ethylene diamine tetraacetic acid (EDTA). 100 ul of CD34 Positive Selection Cocktail tetrameric antibodies was added and mixed with the cells by pipetting. The cells were allowed to bind to the antibodies for 15 minutes. Then, 50 ul of dextran-coated magnetic nanoparticles was added, mixed, and allowed to bind to the antibody-decorated cells for 10 minutes. The volume was brought to 2.5 ml with PBS-FBS-EDTA, and the mixture was placed in the EasySep magnet, allowing CD34 positive cells to be retained, while other cells stay in suspension. The supernatant containing unwanted cells was removed, and the cells were washed two times in a similar manner.

Finally, the cells were suspended in sterile PBS.

Example 3

[0094] In the absence of an adaptive immune response (for example in an autologous setting, or in permanently immunodeficient Nude and severe-combined immunodeficiency (SCID) mice), undifferentiated embryonic stem cells are known to form tumors. In addition, healthy mice are also known to mount an adaptive immune response against allogeneic pluripotent stem cells that is sufficient to reject all the transplanted cells quickly, completely eliminating any such tumors. In this Example, whether allogeneic pluripotent stem cells formed tumors in a mouse whose adaptive immune system was temporarily immunosuppressed by

chemotherapy, but whose adaptive immune system recovered after that temporary period, was investigated.

[0095] H9 Human embryonic stem cells were cultured as in Example 2. Mouse embryonic stem cells (C3H strain) were cultured as in Example 1, except the fibroblasts were mouse embryonic fibroblasts and the medium contained 8 ng/ml leukemia inhibitory factor (LIF) in the place of bFGF. Embryonic stem cells were harvested using Accutase as in Example 2 and counted by complete dissociation into single cells, following flow cytometric analysis on a Miltenyi MACSquant. Human embryonic stem cells were mixed into 50% Matrigel as clumps, and mouse embryonic stem cells as single cell suspension. The cell-matrigel paste was loaded into syringes for injection.

[0096] Permanently immunodeficient Nude or SCID mice were not pre-treated. Control C57-BL/6 mice were not pre-treated. Experimental BL/6 mice were pre- treated with 150 mg/ml of 5-fluorouracil (5FU) intraperitoneally (IP), which causes profound, but temporary, depletion of innate and adaptive immune cells, on the day before stem cell injection. This last group is a model for human chemotherapy patients in a myelosuppressive setting. [0097] As expected, within four months (often as early as 3 weeks), the

permanently immunodeficient mice developed tumors due to the injection of

undifferentiated pluripotent stem cells (Table 1A), even at doses down to only

hundreds of pluripotent stem cells. Also as expected, in the allogeneic / healthy

recipient setting, no tumors developed at all, even at much higher doses of

pluripotent stem cells (1,000,000 hESC, Table IB and 500,000 mESC, Table 1C,

"healthy" rows). Surprisingly, in temporarily immunosuppressed (5FU treated)

mice, no tumors formed either, even at these very high doses of highly tumorigenic

pluripotent stem cells. The window of immunosuppression in these mice is not long enough to permit tumors to take hold such that tumors get rejected before any

growth is visible. This finding suggests that human chemotherapy patients can be

treated with allogeneic pluripotent stem cell-derived products without the risk of

tumor formation.

Table 1 :

A

mESC injected j 57,471 [ 11,891 2,460 ! 509 j 105 !

Tu mor formed 1 Yes Yes Yes Yes Yes Yes ! Yes Yes Ϊ - !

c

Example 4

[0098] hESCs were cultured with mouse embryonic fibroblasts (MEFs), which

aids in maintaining the pluripotency of hESCs. First, the MEFs were prepared by

culturing in T-75 tissue culture flasks under Dulbecco's Modified Eagle's Medium

(DMEM) containing 15% Knockout Serum Replacement (KOSR). The medium was changed every three days. When the MEF cells reached confluency, they were washed once with Hank's Balanced Salt Solution without divalent cations (HBSS). Then, the cells were exposed to 0.05% trypsin, 0.5 mM EDTA for 20 minutes, until the cells begin to detach. Trypsin was removed and the cells were fully detached by repeatedly squirting DMEM at them. The DMEM-containing cell suspension was distributed to new T-75 flasks containing DMEM / KOSR.

[0099] Next, for inhibiting propagation, the MEFs were treated with 10 mg/ml mitomycin C (MITC) in DMEM. The original DMEM solution was removed by aspiration, and 10 ml of MITC-containing DMEM solution was added per T-75 flask. The MEF cells were left in the incubator for 3.5 hours. Then, the MEF cells were washed twice with HBSS, and trypsinized as above. 20,000 MITC-treated MEFs / cm2 were distributed to culture flasks, allowed to attach, and kept in DMEM / 15% KOSR. The next day, the medium was replaced with Knockout-DMEM containing 15% KOSR, lx non-essential amino acids, 0.01% beta-mercaptoethanol and 4 ng/ml basic fibroblast growth factor (bFGF). After one more day in the incubator, the MEF cells were ready for hESC culture.

[0100] Colonies of the human embryonic stem cell line HI in culture were checked for signs of differentiation using phase contrast microscopy. Differentiating colonies were removed manually. Undifferentiated colonies were cut using an EZPassage® stem cell knife (Invitrogen). Dissociation of the ESC colony pieces into single cells was avoided as much as possible. The ESC colony pieces were transferred to the MITC-inactivated MEFs prepared as described above. These were co-cultured for 7 days, or until colonies of ESC of approximately the original size (1-2 mm) formed again. These co-cultures were given fresh medium daily.

[0101] This process allowed glycans from the MEFs to transfer into the hESC, which, upon differentiation will display enhanced immunogenicity.

Example 5 - Co-Culture of ESCs with Mouse Stromal Cells to Simultaneously

Promote Immunogenicity and Direct Differentiation

[0102] Co-culture of ESCs with mouse cells provides a means of differentiation of the ESC populations. The mouse marrow stromal cell line OP9 was maintained in alpha-MEM containing 20% Fetal Bovine Serum (FBS). The medium was replaced every three days. Tissue culture dishes were coated with 0.1% gelatin for 1 hour at room temperature. When ready for passage, OP9 cells were treated with 0.05% trypsin, 0.5 mM EDTA for 30 minutes or until the cells began to detach. Trypsin was removed, and the cells were fully detached by repeatedly squirting alpha-MEM at them. Gelatin was removed from the destination T-75 flasks, and the OP9 / alpha- MEM suspension was transferred into the new, gelatin-coated flasks immediately.

[0103] When the OP9 cells reached confluency the medium was changed to alpha- MEM containing 10%> FBS and 0.01%> beta-mercaptoethanol (OP9 differentiation medium). HI cells were passaged as described above, and transferred to the OP9 layer as colonies. Half the supernatant was changed to fresh OP9 differentiation medium every other day, or as needed. Phenol-red can be added to the medium to gauge when the medium needs to be replenished. After 10-20 days, flow cytometry and colony-forming cell (CFC) assays were used to determine the number of CD34+ CFC in the culture. Using the above method one typically obtains approximately 10% CD34+ cells, and 1% CFC. The cells were detached from the flasks using Accutase for 5 minutes. Cell clumps were dissociated by tituration to form a single cell suspension. Then, CD34+ cells were purified by high speed flow cytometry sorting on a BD FACSAria III instrument. Approximately 100 million CD34+ cells, containing about 10 million CFC were purified using this process.

[0104] This process allowed glycans, such as N-glycolyneuraminic acid to transfer from the OP9 cells to the hESC, providing enhanced immunogenicity of the CD34+ cells upon transplantation.

Example 6 - Incubation with Purified Glycans

[0105] The human embryonic stem cell line HUES-2 (known to have a hematopoietic differentiation bias) was maintained on Matrigel-coated plates in mTESRl . To prepare the Matrigel plates, 1 ml of Matrigel was pipetted into 50 ml of HBSS on ice and mixed. 5 ml of the diluted Matrigel solution was spread to cover the entire bottom of a 9 cm Petri dish. The dish was placed in the incubator at 37C for 1 hour, and then equilibrated at room temperature for 1 hour. The Matrigel was removed and 15 ml of mTESRl was added.

[0106] HUES-2 colonies in a 9 cm dish (with feeders or an existing mTESRl culture) were treated with Accutase for 3 minutes. The Accutase was removed by careful washing with HBSS. The colonies were detached and broken into pieces using a cell scraper, suspended in a small volume of mTESRl, and transferred to the mTESRl dishes as small clumps. The cells were allowed to attach to the new dishes overnight. mTESRl was replaced daily, until the colonies approached confluence, and which point the cells were passaged again.

[0107] To induce differentiation, cells were passaged as above, and suspended in 20 ml of Knockout-DMEM/F12 (Invitrogen) containing mesodermal cytokines 50 ng/ml BMP-4, 25 ng/ml VEGF(165) and 25 ng/ml IL-3 ("predifferentiation medium"). The predifferentiation medium was replaced after 2 days. After 4 days, the cells were transferred to Stemline II medium (Sigma-Aldrich Corporation) containing hematopoietic cytokines 300 ng/ml SCF, 300 ng/ml FLT3L, 100 ng/ml TPO, 100 ng/ml GCSF, 50 ng/ml IL-3 and 10 ng/ml IL-6 ("differentiation medium"). To this differentiation medium 1 mM of N-glycolyneuraminic acid (Neu5Gc) an animal derivative of sialic acid was added. This concentration of Neu5Gc can be altered greatly in either direction in order to fine tune the intended level of immunogenicity in the particular patient or clinical application. The differentiation medium was replaced every other day, for a total of 24 days.

Embryoid bodies were dissociated using Accutase. CD34+ cells were purified from the resultant suspension as above.

References

Each reference indicated is hereby incorporated herein by reference in its entirety.

U.S. Patents 6,465,247; 6,761,883; 7,300,760; 7,618,654

Clamp AR, Ryder WD, Bhattacharya S, Pettengell R, Radford JA. Patterns of mortality after prolonged follow-up of a randomized controlled trial using granulocyte colony-stimulating factor to maintain chemotherapy dose intensity in non-Hodgkin's lymphoma. Br J Cancer. 2008 Jul 22;99(2):253-8

Siminovitch L, McCulloch Ea, Till JE. The distribution of colony-forming cells among spleen colonies. J Cell Physiol. 1963 Dec;62:327-36

McNiece I, Jones R, Cagnoni P, Bearman S, Nieto Y, Shpall EJ. Ex-vivo expansion of hematopoietic progenitor cells: preliminary results in breast cancer. Hematol Cell Ther. 1999 Apr;41(2):82-6

Manz MG, Miyamoto T, Akashi K, Weissman IL. Prospective isolation of human clonogenic common myeloid progenitors. Proc Natl Acad Sci U S A. 2002 Sep 3;99(18): 1 1872-7

Taylor CJ, Bolton EM, Pocock S, Sharpies LD, Pedersen RA, Bradley JA. Banking on human embryonic stem cells: estimating the number of donor cell lines needed for HLA matching. Lancet. 2005 Dec 10;366(9502):2019-25.

Hentze H, Soong PL, Wang ST, Phillips BW, Putti TC, Dunn NR. Teratoma formation by human embryonic stem cells: Evaluation of essential parameters for future safety studies. Stem Cell Res. 2009 May;2(3): 198-210. Epub 2009 Feb 12.

Blum B, Benvenisty N. The tumorigenicity of human embryonic stem cells. Adv Cancer Res. 2008; 100: 133-58

Fong CY, Gauthaman K, Bongso A. Teratomas from pluripotent stem cells: A clinical hurdle. J Cell Biochem. 2010 Nov 1; 1 11(4):769-81

Knoepfler PS. Deconstructing stem cell tumorigenicity: a roadmap to safe regenerative medicine. Stem Cells. 2009 May;27(5): 1050-6. Pal R, Totey S, Mamidi MK, Bhat VS, Totey S. Propensity of human embryonic stem cell lines during early stage of lineage specification controls their terminal differentiation into mature cell types. Exp Biol Med (Maywood). 2009

Oct;234(10): 1230-43.

Martin MJ, Muotri A, Gage F, Varki A., Human embryonic stem cells express an immunogenic nonhuman sialic acid, Nat Med. 2005 Feb; l l(2):228-32. Epub 2005 Jan 30.

Ebert J, Human stem cells trigger immune attack, 24 January 2005, | Nature doi: 10.1038/news050124-l

Fong CY, Gauthaman K, Bongso A. , Teratomas from pluripotent stem cells: A clinical hurdle, J Cell Biochem. 2010 Nov 1; 1 11(4):769-81

Pal R, Totey S, Mamidi MK, Bhat VS, Totey S. Propensity of human embryonic stem cell lines during early stage of lineage specification controls their terminal differentiation into mature cell types. Exp Biol Med (Maywood). 2009 Oct;

234(10): 1230-43

EQUIVALENTS

[0108] It is to be understood that while the disclosure has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims. For example, the selection of useful human ESCs is believed to be routine to one of ordinary skill in the art in view of the teachings herein.

Claims

1. A method of producing a substantially purified population of CFCs comprising: obtaining a substantially purified population of hESCs; culturing the population of hESCs under conditions that promote hematopoietic differentiation of the hESCs; and isolating from the culture a substantially pure population of CFCs, wherein the CFCs are clonally identical.

2. The method of claim I, wherein the hESCs are cultured on mouse fibroblasts.

3. The method of claim 1 , wherein the hESCs are cultured on human fibroblasts.

4. The method of claim 3, wherein the population of hESCs are cultured in a knockout-DMEM culture medium.

5. The method of claim 3, wherein the population of hESCs are cultured in a hESCgro medium.

6. The method of claim I, wherein the population of hESCs are cultured in a culture vessel coated with Matrigel or an equivalent pluripotency-supporting substrate.

7. The method of claim 1, wherein the population of hESCs are cultured in a mTESRl or equivalent feeder- free culture medium.

8. The method of claim 1, wherein hematopoietic differentiation is determined by embryoid body formation.

9. The method of claim 8, wherein differentiation involves exposing the embryoid bodies to a mesoderm-inducing cytokine over a period of about 3 to about 30 days.

10. The method of claim 9 wherein the cytokine is BMP-4, VEGF, bFGF, Activin A, IL-3, or a combination thereof.

1 1. The method of claim 8, wherein differentiation involves exposing the embryoid bodies to a hematopoietic cytokine over a period of 3 to 30 days.

12. The method of claim 11 wherein the cytokine is SCF, FLT3L, TPO, GCSF, IL-3, IL-6, or a combination thereof.

13. The method of claim 1, wherein differentiation is effectuated by coculturing the population of hESCs with a stromal cell line.

14. The method of claim 13, wherein the stromal cell line is a human stromal cell line.

15. The method of claim 14, further comprising selecting the stromal cell line from a pool of potential stromal cell lines by determining which line instructs the highest numbers of CFC or CD34+ cells.

16. The method of claim 14, wherein the stromal cell line is HS5.

17. The method of claim 13, wherein the stromal cell line is OP9.

18. The method of claim 1, wherein the hESC are from an embryonic stem cell line.

19. The method of claim 1, wherein the hESCs are from an induced pluripotent stem cell line.

20. The method of claim 19, wherein the hESCs are induced to form a CD34+ cell.

21. The method of claim 19, wherein the hESCs are induced to form a granulocyte population.

22. The method of claim 1, wherein the isolating step comprises magnetic cell separation.

23. The method of claim 1, wherein the isolating step comprises sterile flow cytometry sorting.

24. The method of claim 22 or 23, wherein the isolating step comprises using CD34 antigen for purification.

25. The method of claim 22 or 23, wherein the isolating step comprises using CD38 antigen for purification.

26. The method of claim 22 or 23, wherein the isolating step comprises using CD41 antigen for purification.

27. The method of claim 1, wherein the isolating step comprises density gradient centrifugation.

28. A method of treating a cytopenia comprising: identifying a subject having a cytopenia; obtaining a population of hESCs; culturing the population of hESCs to obtain a substantially pure population of CFCs; and transplanting the population of CFCs to the subject thereby treating the cytopenia.

29. The method of claim 28, wherein the subject has a cytopenia due to chemotherapy.

30. The method of claim 28, wherein the subject has a cytopenia due to radiation exposure.

31. The method of claim 28, wherein the subject has a cytopenia due to chemical weapons exposure.

32. The method of claim 28, wherein the subject has a cytopenia due to accidental chemical exposure.

33. The method of claim 28, wherein the subject has a congenital neutropenia.

34. The method of claim 28, wherein the method restores the subject's neutrophil counts to substantially normal ranges.

35. The method of claim 28, wherein the method restores the subject's number of transient amplifying cells to substantially normal ranges.

36. The method of claim 28, wherein the method provides prophylaxis for infection.

37. The method of claim 28, wherein the method treats an existing infection.

38. A method of treating a cytopenia comprising: identifying a subject having a cytopenia; obtaining a population of hESCs that are allogeneic to the subject; culturing the population of hESCs to obtain a substantially pure population of CFCs; and transplanting the population of CFCs to the subject thereby treating the cytopenia.

39. The method of claim 38, wherein the hESCs are immunologically incompatible to the subject.

40. The method of claim 39, wherein the immunological incompatibility comprises one or more human leukocyte antigen mismatches.

41. The method of claim 39, wherein the immunological incompatibility is enhanced by culturing the hESCs on non-human embryonic fibroblasts, such that non-human peptides or glycans become incorporated in the hESCs or their derivatives.

42. The method of claim 39, wherein the immunological incompatibility is induced by differentiating the hESCs into colony forming cells by coculture with a non-human marrow stromal cell line, such that non-human peptides or glycans become incorporated into the human colony forming cells

43. The method of claim 28, wherein the hESC line is screened for an intrinsic bias to differentiate into mature blood cell types.

44. The method of claim 28, wherein the CFCs persist in the subject's body for less than six months.