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Advances in Embryonic Stem Cell Research

The studies cited below are a sampling of the published and peer-reviewed material available on the subject. The list will be updated on a regular basis.

Production of pancreatic hormone-expressing endocrine cells from human embryonic stem cells.

D'Amour KA, Bang AG, Eliazer S, Kelly OG, Agulnick AD, Smart NG, Moorman MA, Kroon E, Carpenter MK, Baetge EE.
Novocell Inc., 3550 General Atomics Ct., San Diego, California 92121, USA., Nat Biotechnol. 2006 Nov;24(11):1392-401. Epub 2006 Oct 19.

Abstract: Of paramount importance for the development of cell therapies to treat diabetes is the production of sufficient numbers of pancreatic endocrine cells that function similarly to primary islets. We have developed a differentiation process that converts human embryonic stem (hES) cells to endocrine cells capable of synthesizing the pancreatic hormones insulin, glucagon, somatostatin, pancreatic polypeptide and ghrelin. This process mimics in vivo pancreatic organogenesis by directing cells through stages resembling definitive endoderm, gut-tube endoderm, pancreatic endoderm and endocrine precursor--en route to cells that express endocrine hormones. The hES cell-derived insulin-expressing cells have an insulin content approaching that of adult islets. Similar to fetal beta-cells, they release C-peptide in response to multiple secretory stimuli, but only minimally to glucose. Production of these hES cell-derived endocrine cells may represent a critical step in the development of a renewable source of cells for diabetes cell therapy.

Distinct differentiation characteristics of individual human embryonic stem cell lines.

Mikkola M, Olsson C, Palgi J, Ustinov J, Palomaki T, Horelli-Kuitunen N, Knuutila S, Lundin K, Otonkoski T, Tuuri T. , Program of Developmental and Reproductive Biology, Biomedicum Helsinki, PO Box 63, 00014 University of Helsinki, Helsinki, Finland. milla.mikkola@helsinki.fi, BMC Dev Biol. 2006 Aug 8;6:40

ABSTRACT: Individual differences between human embryonic stem cell (hESC) lines are poorly understood. Here, we describe the derivation of five hESC lines (called FES 21, 22, 29, 30 and 61) from frozen-thawed human embryos and compare their individual differentiation characteristic. RESULTS: The cell lines were cultured either on human or mouse feeder cells. The cells grew significantly faster and could be passaged enzymatically only on mouse feeders. However, this was found to lead to chromosomal instability after prolonged culture. All hESC lines expressed the established markers of pluripotent cells as well as several primordial germ cell (PGC) marker genes in a uniform manner. However, the cell lines showed distinct features in their spontaneous differentiation patterns. The embryoid body (EB) formation frequency of FES 30 cell line was significantly lower than that of other lines and cells within the EBs differentiated less readily. Likewise, teratomas derived from FES 30 cells were constantly cystic and showed only minor solid tissue formation with a monotonous differentiation pattern as compared with the other lines. CONCLUSION: hESC lines may differ substantially in their differentiation properties although they appear similar in the undifferentiated state.

Functional engraftment of human ES cell-derived dopaminergic neurons enriched by coculture with telomerase-immortalized midbrain astrocytes.

Roy NS, et al., Nat Med. 2006 Nov;12(11):1259-68. Epub 2006 Oct 22

Abstract: To direct human embryonic stem (HES) cells to a dopaminergic neuronal fate, we cocultured HES cells that were exposed to both sonic hedgehog and fibroblast growth factor 8 with telomerase-immortalized human fetal midbrain astrocytes. These astrocytes substantially potentiated dopaminergic neurogenesis by both WA09 and WA01 HES cells, biasing them to the A9 nigrostriatal phenotype. When transplanted into the neostriata of 6-hydroxydopamine-lesioned parkinsonian rats, the dopaminergic implants yielded a significant, substantial and long-lasting restitution of motor function. However, although rich in donor-derived tyrosine hydroxylase-expressing neurons, the grafts exhibited expanding cores of undifferentiated mitotic neuroepithelial cells, which can be tumorigenic. These results show the utility of recreating the cellular environment of the developing human midbrain while driving dopaminergic neurogenesis from HES cells, and they demonstrate the potential of the resultant cells to mediate substantial functional recovery in a model of Parkinson disease. Yet these data also mandate caution in the clinical application of HES cell-derived grafts, given their potential for phenotypic instability and undifferentiated expansion.

Recovery from paralysis in adult rats using embryonic stem cells.

Deshpande DM, et al., Ann Neurol. 2006 Jul;60(1):32-44.

OBJECTIVE: We explored the potential of embryonic stem cell-derived motor neurons to functionally replace those cells destroyed in paralyzed adult rats. METHODS: We administered a phosphodiesterase type 4 inhibitor and dibutyryl cyclic adenosine monophosphate to overcome myelin-mediated repulsion and provided glial cell-derived neurotrophic factor within the sciatic nerve to attract transplanted embryonic stem cell-derived axons toward skeletal muscle targets. RESULTS: We found that these strategies significantly increased the success of transplanted axons extending out of the spinal cord into ventral roots. Furthermore, transplant-derived axons reached muscle, formed neuromuscular junctions, were physiologically active, and mediated partial recovery from paralysis. INTERPRETATION: We conclude that restoration of functional motor units by embryonic stem cells is possible and represents a potential therapeutic strategy for patients with paralysis. To our knowledge, this is the first report of the anatomical and functional replacement of a motor neuron circuit within the adult mammalian host.

Transplantation of human embryonic stem cell-derived cells to a rat model of Parkinson's disease: effect of in vitro differentiation on graft survival and teratoma formation.

Brederlau A, et al., Stem Cells. 2006 Jun;24(6):1433-40. Epub 2006 Mar 23.

Abstract: Human embryonic stem cells (hESCs) have been proposed as a source of dopamine (DA) neurons for transplantation in Parkinson's disease (PD). We have investigated the effect of in vitro predifferentiation on in vivo survival and differentiation of hESCs implanted into the 6-OHDA (6-hydroxydopamine)-lesion rat model of PD. The hESCs were cocultured with PA6 cells for 16, 20, or 23 days, leading to the in vitro differentiation into DA neurons. Grafted hESC-derived cells survived well and expressed neuronal markers. However, very few exhibited a DA neuron phenotype. Reversal of lesion-induced motor deficits was not observed. Rats grafted with hESCs predifferentiated in vitro for 16 days developed severe teratomas, whereas most rats grafted with hESCs predifferentiated for 20 and 23 days remained healthy until the end of the experiment. This indicates that prolonged in vitro differentiation of hESCs is essential for preventing formation of teratomas.

Dopaminergic neurons generated from monkey embryonic stem cells function in a Parkinson primate model.

Takagi Y, et al., J Clin Invest. 2005 Jan;115(1):102-9.

Abstract: Parkinson disease (PD) is a neurodegenerative disorder characterized by loss of midbrain dopaminergic (DA) neurons. ES cells are currently the most promising donor cell source for cell-replacement therapy in PD. We previously described a strong neuralizing activity present on the surface of stromal cells, named stromal cell-derived inducing activity (SDIA). In this study, we generated neurospheres composed of neural progenitors from monkey ES cells, which are capable of producing large numbers of DA neurons. We demonstrated that FGF20, preferentially expressed in the substantia nigra, acts synergistically with FGF2 to increase the number of DA neurons in ES cell-derived neurospheres. We also analyzed the effect of transplantation of DA neurons generated from monkey ES cells into 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated (MPTP-treated) monkeys, a primate model for PD. Behavioral studies and functional imaging revealed that the transplanted cells functioned as DA neurons and attenuated MPTP-induced neurological symptoms.

Human embryonic stem cell-derived oligodendrocyte progenitor cell transplants remyelinate and restore locomotion after spinal cord injury.

Keirstead HS, et al, J Neurosci. 2005 May 11;25(19):4694-705.

Abstract: Demyelination contributes to loss of function after spinal cord injury, and thus a potential therapeutic strategy involves replacing myelin-forming cells. Here, we show that transplantation of human embryonic stem cell (hESC)-derived oligodendrocyte progenitor cells (OPCs) into adult rat spinal cord injuries enhances remyelination and promotes improvement of motor function. OPCs were injected 7 d or 10 months after injury. In both cases, transplanted cells survived, redistributed over short distances, and differentiated into oligodendrocytes. Animals that received OPCs 7 d after injury exhibited enhanced remyelination and substantially improved locomotor ability. In contrast, when OPCs were transplanted 10 months after injury, there was no enhanced remyelination or locomotor recovery. These studies document the feasibility of predifferentiating hESCs into functional OPCs and demonstrate their therapeutic potential at early time points after spinal cord injury.

Transplantation of apoptosis-resistant embryonic stem cells into the injured rat spinal cord.

Howard MJ, et al., Somatosens Mot Res. 2005 Mar-Jun;22(1-2):37-44.

Abstract: Murine embryonic stem cells were induced to differentiate into neural lineage cells by exposure to retinoic acid. Approximately one million cells were transplanted into the lesion site in the spinal cords of adult rats which had received moderate contusion injuries 9 days previously. One group received transplants of cells genetically modified to over-express bcl-2, which codes for an anti-apoptotic protein. A second group received transplants of the wild-type ES cells from which the bcl-2 line was developed. In the untransplanted control group, only medium was injected. Locomotor abilities were assessed using the Basso, Beattie and Bresnahan (BBB) rating scale for 6 weeks. There was no incremental locomotor improvement in either transplant group when compared to control over the survival period. Morbidity and mortality were significantly more prevalent in the transplant groups than in controls. At the conclusion of the 6-week survival period, the spinal cords were examined. Two of six cords from the bcl-2 group and one of 12 cords from the wild-type group showed gross evidence of abnormal growths at the site of transplantation. No similar growth was seen in the control. Pathological examination of the abnormal cords showed very large numbers of undifferentiated cells proliferating at the injection site and extending up to 1.5 cm rostrally and caudally. These results suggest that transplanting KD3 ES cells, or apoptosis-resistant cells derived from the KD3 line, into the injured spinal cord does not improve locomotor recovery and can lead to tumor-like growth of cells, accompanied by increased debilitation, morbidity and mortality.

Human embryonic stem cells differentiate into oligodendrocytes in high purity and myelinate after spinal cord transplantation.

Nistor GI, et al., Glia. 2005 Feb;49(3):385-96.

Abstract: Human embryonic stem cells (hESCs) demonstrate remarkable proliferative and developmental capacity. Clinical interest arises from their ability to provide an apparently unlimited cell supply for transplantation, and from the hope that they can be directed to desirable phenotypes in high purity. Here we present for the first time a method for obtaining oligodendrocytes and their progenitors in high yield from hESCs. We expanded hESCs, promoted their differentiation into oligodendroglial progenitors, amplified those progenitors, and then promoted oligodendroglial differentiation using positive selection and mechanical enrichment. Transplantation into the shiverer model of dysmyelination resulted in integration, differentiation into oligodendrocytes, and compact myelin formation, demonstrating that these cells display a functional phenotype. This differentiation protocol provides a means of generating human oligodendroglial lineage cells in high purity, for use in studies of lineage development, screening assays of oligodendroglial-specific compounds, and treating neurodegenerative diseases and traumatic injuries to the adult CNS. Copyright 2004 Wiley-Liss, Inc.

Origin of insulin secreted from islet-like cell clusters derived from murine embryonic stem cells.

Paek HJ, et al., Cloning Stem Cells. 2005;7(4):226-31.

Abstract: Islet-like cell clusters (ILCCs) were derived from murine embryonic stem cells using a slightly modified version of the protocol originally described by Lumelsky et al. in 2001. Analysis with enzyme-linked immunosorbent assays (ELISAs) that distinguish human from murine insulin demonstrated that insulin released from these ILCCs, upon initial in vitro glucose challenge, was of non-murine origin and in fact corresponded to the species of insulin, human or bovine, that had been added to the culture media used to derive ILCCs. This finding convincingly supports the hypothesis that ILCCs are not synthesizing insulin de novo, but rather simply regurgitating insulin taken up during tissue culture. In further experiments, ILCCs were derived in media in which insulin had been replaced by IGF-I with which it shares a common signaling pathway. These ILCCs failed to release any detectable insulin. In contrast, ILCCs produced by various protocols stained positive (dithizone and immunoselective antibodies) for intracellular insulin and, in some cases, C-peptide. Despite the presence of at least some level of de novo, synthesized insulin in ILCCs, the majority of insulin released by ILCCs was sequestered from the exogenous medium.

Teratoma formation leads to failure of treatment for type I diabetes using embryonic stem cell-derived insulin-producing cells.

Fujikawa T, et al., Am J Pathol. 2005 Jun;166(6):1781-91.

Abstract: Embryonic stem (ES) cells have been proposed to be a powerful tool in the study of pancreatic disease, as well as a potential source for cell replacement therapy in the treatment of diabetes. However, data demonstrating the feasibility of using pancreatic islet-like cells differentiated from ES cells remain controversial. In this study we characterized ES cell-derived insulin-expressing cells and assessed their suitability for the treatment of type I diabetes. ES cell-derived insulin-stained cell clusters expressed insulin mRNA and transcription factors associated with pancreatic development. The majority of insulin-positive cells in the clusters also showed immunoreactivity for C-peptide. Insulin was stored in the cytoplasm and released into the culture medium in a glucose-dependent manner. When the cultured cells were transplanted into diabetic mice, they reversed the hyperglycemic state for approximately 3 weeks, but the rescue failed due to immature teratoma formation. Our studies demonstrate that reversal of hyperglycemia by transplantation of ES cell-derived insulin-producing cells is possible. However, the risk of teratoma formation would need to be eliminated before ES cell-based therapies for the treatment of diabetes are considered.

Artifactual insulin release from differentiated embryonic stem cells.

Hansson M, et al., Diabetes. 2004 Oct;53(10):2603-9.

Abstract: Several recent reports claim the generation of insulin-producing cells from embryonic stem cells via the differentiation of progenitors that express nestin. Here, we investigate further the properties of these insulin-containing cells. We find that although differentiated cells contain immunoreactive insulin, they do not contain proinsulin-derived C-peptide. Furthermore, we find variable insulin release from these cells upon glucose addition, but C-peptide release is never detected. In addition, many of the insulin-immunoreactive cells are undergoing apoptosis or necrosis. We further show that cells cultured in the presence of a phosphoinositide 3-kinase inhibitor, which previously was reported to facilitate the differentiation of insulin(+) cells, are not C-peptide immunoreactive but take up fluorescein isothiocyanate-labeled insulin from the culture medium. Together, these data suggest that nestin(+) progenitor cells give rise to a population of cells that contain insulin, not as a result of biosynthesis but from the uptake of exogenous insulin. We conclude that C-peptide biosynthesis and secretion should be demonstrated to claim insulin production from embryonic stem cell progeny.

Transplantation of embryonic stem cells into the infarcted mouse heart: formation of multiple cell types.

Singla DK, et al., J Mol Cell Cardiol. 2006 Jan;40(1):195-200. Epub 2005 Nov 8.

Abstract: Initial studies have suggested that transplantation of embryonic stem (ES) cells following myocardial infarction (MI) in animal models is beneficial; however, the mechanism of benefit is largely unknown. The present study investigated the fate of mouse ES cells transplanted post-MI to determine if the ES cells give rise to the range of major cell types present in the native myocardium. MI was produced by coronary artery ligation in C57BL/6 mice. Two different mouse ES cell lines, expressing eGFP and beta-galactosidase, respectively, were tested. Post-MI intramyocardial injection of 3 x 10(4) ES cells was compared to injection of media alone. Histochemistry and immunofluorescence were used to track the transplanted ES cells and identify the resulting cell types. Echocardiography assessed the cardiac size and function in a blinded fashion. Two weeks post-MI, engraftment of the transplanted ES cells was demonstrated by eGFP or beta-galactosidase-positive cells in the infarct region without evidence for tumor formation. Co-immunolabeling demonstrated that the transplanted ES cells had become cardiomyocytes, vascular smooth muscle, and endothelial cells. Echocardiographic analysis showed that ES cell transplantation resulted in reduced post-MI remodeling of the heart and improved cardiac function. In conclusion, transplanted mouse ES cells can regenerate infarcted myocardium in part by becoming cardiomyocytes, vascular smooth muscle, and endothelial cells that result in an improvement in cardiac structure and function. Therefore, ES cells hold promise for myocardial cellular therapy.

They are not stealthy in the heart: embryonic stem cells trigger cell infiltration, humoral and T-lymphocyte-based host immune response.

Kofidis T, et al., Eur J Cardiothorac Surg. 2005 Sep;28(3):461-6.

OBJECTIVE: The in vivo immunogenicity of Embryonic Stem Cells is controversial. At present, there is only in vitro evidence of MHC I expression by this cell population but vivid speculation about their immune-privileged state. The immunology aspect of ESC transplantation deserves thorough investigation. METHODS: We injected mouse ESC (expressing Green Fluorescent Protein, GFP) into injured myocardium of syngeneic, allogeneic and SCID recipients. Furthermore, we monitored host response for up to 4 weeks post cell transfer. We determined local response (CD 3, CD 11c expression by host cells), MHC I expression by donor cells, MHC-II expression within and around the graft, humoral response of allogeneic hosts using Flow Cytometry and evaluated the hosts' cytokine response using stimulated spleenocytes by means of ELISPOT. Cell survival was estimated by morphometry, by calculating the area of the GFP+ graft over the area of infarction at multiple sections of the harvested heart. RESULTS: There was significant cellular infiltration into and around the graft consisting of T-lymphocytes (CD3+) and dendritic cells (CD 11c). Infiltration was detectable at 1 week and progressed through 4 weeks following cell transplantation. The humoral Ab response was moderate at 2 weeks but frank at 4 weeks. ELISPOT demonstrated a Th1 pathway of donor specific T-lymphocyte response with strong IFN-gamma and Il-2 production (figure A). MHC I expression was significant within the graft and maximal in the allogeneic groups. CONCLUSIONS: An immune response against transplanted ESC was demonstrated and the future use of ESC will likely require the use of systemic immunosuppression.

Stable benefit of embryonic stem cell therapy in myocardial infarction.

Hodgson DM, et al., Am J Physiol Heart Circ Physiol. 2004 Aug;287(2):H471-9.

Abstract: Conventional therapies for myocardial infarction attenuate disease progression without contributing significantly to repair. Because of the capacity for de novo cardiogenesis, embryonic stem cells are considered a potential source for myocardial regeneration, yet limited information is available on their ultimate therapeutic value. We treated infarcted rat hearts with CGR8 embryonic stem cells preexamined for cardiogenicity, serially probed left ventricular function, and determined final pathological outcome. Stem cell delivery generated new cardiomyocytes of embryonic stem cell origin that integrated with host myocardium within infarct regions. This resulted in a functional benefit within 3 wk that remained sustained over 12 wk of continuous follow-up and included a vigorous inotropic response to beta-adrenergic challenge. Integration of stem cell-derived cardiomyocytes was associated with normalized ventricular architecture, little scar, and a decrease in signs of myocardial necrosis. In contrast, sham-treated infarcted hearts exhibited ventricular cavity dilation and aneurysm formation, poor ventricular function, and a lack of response to beta-adrenergic stimulation. No evidence of graft rejection, ectopy, sudden cardiac death, or tumor formation was observed after therapy. These findings indicate that embryonic stem cells, through differentiation within the host myocardium, can contribute to a stable beneficial outcome on contractile function and ventricular remodeling in the infarcted heart.

The proteasome restricts permissive transcription at tissue-specific gene Loci in embryonic stem cells.

Szutorisz H, et al, Cell. 2006 Dec 29;127(7):1375-88.

Abstract: The ability of stem cells to activate different gene expression programs requires the choreographed assembly of trans-acting factors at enhancers and promoters during cell differentiation. In this study, we show that the proteasome acts on specific regulatory regions in embryonic stem (ES) cells to prevent incorrect transcriptional initiation. Chemical or siRNA-mediated inhibition of proteasome activity results in increased transcription factor and RNA polymerase II binding and leads to activation of cryptic promoters. Analysis of the binding profiles of different proteasome subunits in normal ES cells and following RNAi knockdown of individual subunits provides evidence for a targeted assembly of the 26S proteasome at specific regulatory elements. Our results suggest that the proteasome promotes a dynamic turnover of transcription factor and Pol II binding at tissue-specific gene domains in ES cells, thereby restricting permissive transcriptional activity and keeping the genes in a potentiated state, ready for activation at later stages.

F0 generation mice fully derived from gene-targeted embryonic stem cells allowing immediate phenotypic analyses.

Poueymirou WT, et al, Nat Biotechnol. 2006 Dec 24; [Epub ahead of print]

Abstract: A useful approach for exploring gene function involves generating mutant mice from genetically modified embryonic stem (ES) cells. Recent advances in genetic engineering of ES cells have shifted the bottleneck in this process to the generation of mice. Conventional injections of ES cells into blastocyst hosts produce F0 generation chimeras that are only partially derived from ES cells, requiring additional breeding to obtain mutant mice that can be phenotyped. The tetraploid complementation approach directly yields mice that are almost entirely derived from ES cells, but it is inefficient, works only with certain hybrid ES cell lines and suffers from nonspecific lethality and abnormalities, complicating phenotypic analyses. Here we show that laser-assisted injection of either inbred or hybrid ES cells into eight cell-stage embryos efficiently yields F0 generation mice that are fully ES cell-derived and healthy, exhibit 100% germline transmission and allow immediate phenotypic analysis, greatly accelerating gene function assignment.

Persistent dopamine functions of neurons derived from embryonic stem cells in a rodent model of Parkinson's disease.

Rodriguez-Gomez JA, et al., Stem Cells. 2006 Dec 14; [Epub ahead of print]

Abstract: The derivation of dopamine neurons is one of the best examples of the clinical potential of embryonic stem (ES) cells but the long-term function of the grafted neurons has not been established. Here we show that after transplantation into an animal model, neurons derived from mouse ES cells survived for over 32 weeks, maintained midbrain markers and had sustained behavioral effects. Microdialysis in grafted animals showed DA release was induced by depolarization and pharmacological stimulants. Positron emission tomography (PET) measured the expression of pre-synaptic dopamine transporters (DAT) in the graft and also showed that the number of postsynaptic DA D2 receptors was normalized in the host striatum. These data suggest that ES-cell derived neurons show DA release, reuptake and stimulate appropriate post-synaptic responses for long periods after implantation. This work supports continued interest in ES cells as a source of functional DA neurons.

Derivation of human embryonic stem cells in defined conditions.

Ludwig TE, et al., Nat Biotechnol. 2006 Feb;24(2):185-7. Epub 2006 Jan 1.

Abstract: We have previously reported that high concentrations of basic fibroblast growth factor (bFGF) support feeder-independent growth of human embryonic stem (ES) cells, but those conditions included poorly defined serum and matrix components. Here we report feeder-independent human ES cell culture that includes protein components solely derived from recombinant sources or purified from human material. We describe the derivation of two new human ES cell lines in these defined culture conditions.

Gut-like structures from mouse embryonic stem cells as an in vitro model for gut organogenesis preserving developmental potential after transplantation.

Torihashi S, et al., Stem Cells. 2006 Dec;24(12):2618-26. Epub 2006 Aug 3.

Abstract: Recently, we reported the formation of gut-like structures from mouse ESCs in vitro. To determine whether ESCs provide an in vitro model of gastrointestinal (GI) tracts and their organogenesis, we investigated the morphological features, formation process, cellular development, and regional location within the GI tract by immunohistochemistry, electron microscopy, and reverse transcription-polymerase chain reaction. We also examined the developmental potential by transplantation into kidney capsules. The results demonstrated that Id2-expressing epithelium developed first, alpha-smooth muscle actin appeared around the periphery, and finally, the gut-like structures were formed into a three-layer organ with well-differentiated epithelium. A connective tissue layer and musculature with interstitial cells of Cajal developed, similar to organogenesis of the embryonic gut. Enteric neurons appeared underdeveloped, and blood vessels were absent. Many structures expressed intestinal markers Cdx2 and 5-hydroxytryptamine but not the stomach marker H(+)/K(+) ATPase. Transplants obtained blood vessels and extrinsic nerve growth from the host to prolong life, and even grafts of premature structures did not form teratoma. In conclusion, gut-like structures were provided with prototypical tissue components of the GI tract and are inherent in the intestine rather than the stomach. The formation process was basically same as in gut organogenesis. They maintain their developmental potential after transplantation. Therefore, gut-like structures provide a unique and useful in vitro system for development and stem cell studies of the GI tract, including transplantation experiments.

BMP-4 is required for hepatic specification of mouse embryonic stem cell-derived definitive endoderm.

Gouon-Evans V, et al., Nat Biotechnol. 2006 Nov;24(11):1402-11. Epub 2006 Nov 5.

Abstract: When differentiated in the presence of activin A in serum-free conditions, mouse embryonic stem cells efficiently generate an endoderm progenitor population defined by the coexpression of either Brachyury, Foxa2 and c-Kit, or c-Kit and Cxcr4. Specification of these progenitors with bone morphogenetic protein-4 in combination with basic fibroblast growth factor and activin A results in the development of hepatic populations highly enriched (45-70%) for cells that express the alpha-fetoprotein and albumin proteins. These cells also express transcripts of Afp, Alb1, Tat, Cps1, Cyp7a1 and Cyp3a11; they secrete albumin, store glycogen, show ultrastructural characteristics of mature hepatocytes, and are able to integrate into and proliferate in injured livers in vivo and mature into hepatocytes expressing dipeptidyl peptidase IV or fumarylacetoacetate hydrolase. Together, these findings establish a developmental pathway in embryonic stem cell differentiation cultures that leads to efficient generation of cells with an immature hepatocytic phenotype.

Reversal of mouse hepatic failure using an implanted liver-assist device containing ES cell-derived hepatocytes.

Soto-Gutierrez A, et al., Nat Biotechnol. 2006 Nov;24(11):1412-9. Epub 2006 Nov 5.

Abstract: Severe acute liver failure, even when transient, must be treated by transplantation and lifelong immune suppression. Treatment could be improved by bioartificial liver (BAL) support, but this approach is hindered by a shortage of human hepatocytes. To generate an alternative source of cells for BAL support, we differentiated mouse embryonic stem (ES) cells into hepatocytes by coculture with a combination of human liver nonparenchymal cell lines and fibroblast growth factor-2, human activin-A and hepatocyte growth factor. Functional hepatocytes were isolated using albumin promoter-based cell sorting. ES cell-derived hepatocytes expressed liver-specific genes, secreted albumin and metabolized ammonia, lidocaine and diazepam. Treatment of 90% hepatectomized mice with a subcutaneously implanted BAL seeded with ES cell-derived hepatocytes or primary hepatocytes improved liver function and prolonged survival, whereas treatment with a BAL seeded with control cells did not. After functioning in the BAL, ES cell-derived hepatocytes developed characteristics nearly identical to those of primary hepatocytes.

Differentiation of human embryonic stem cells to hepatocytes using deleted variant of HGF and poly-amino-urethane-coated nonwoven polytetrafluoroethylene fabric.

Soto-Gutierrez A, et al., Cell Transplant. 2006;15(4):335-41.

Abstract: Human embryonic stem (hES) cells have recently been studied as an attractive source for the development of a bioartificial liver (BAL). Here we evaluate the differentiation capacity of hES cells into hepatocytes. hES cells were subjected to suspension culture for 5 days, and then cultured onto poly-amino-urethane (PAU)-coated, nonwoven polytetrafluoroethylene (PTFE) fabric in the presence of fibroblast growth factor-2 (bFGF) (100 ng/ml) for 3 days, then with deleted variant of hepatocyte growth factor (dHGF) (100 ng/ml) and 1% dimethyl sulfoxide (DMSO) for 8 days, and finally with dexamethasone (10(-7) M) for 3 days. The hES cells showed gene expression of albumin in a time-dependent manner of the hepatic differentiation process. The resultant hES-derived hepatocytes metabolized the loaded ammonia and lidocaine at 7.8% and 23.6%, respectively. A million of such hepatocytes produced albumin and urea at 351.2 ng and urea at 7.0 microg. Scanning electron microscopy showed good attachment of the cells on the surface of the PTFE fabric and well-developed glycogen rosettes and Gap junction. In the present work we have demonstrated the efficient differentiation of hES cells to functional hepatocytes. The findings are useful to develop a BAL.

Human embryonic stem cells are immunogenic in allogeneic and xenogeneic settings.

Grinnemo KH, et al., Reprod Biomed Online. 2006 Nov;13(5):712-24.

Abstract: Recent studies have suggested that human embryonic stem cells (HESC) are immune-privileged and may thereby circumvent rejection. The expression of immunologically active molecules was studied by DNA microarray analysis and by flow cytometry. HESC were transplanted into immunologically competent mice and traced by fluorescence in-situ hybridization (FISH) and immunohistochemistry. The ability of HESC to directly and indirectly induce immune responses in CD4+ T-cells from naive and transplanted mice was studied. Their ability to induce immune responses of human CD4+ T-cells, when cultured in the presence of dendritic cells (DC) syngeneic to responder T-cells, was also analysed. HESC demonstrated expression of HLA class I and HLA class II genes, but the cell surface expression of HLA class II molecules was low even after incubation with IFNgamma. In wild-type mice, HESC could be demonstrated by FISH until 3 days after transplantation and were surrounded by heavy infiltrates of T-cells and macrophages. HESC induced a similar immune response as human fibroblast cells (HFib) on naive and immunized T-cells, both directly and in the presence of syngeneic DC. A similar response was observed in the allogeneic setting. It is concluded that HESC are immunologically inert and do not inhibit immune responses during direct or indirect antigen presentation, and they were acutely rejected in a xenogeneic setting.

Human embryonic stem cell-derived cells rescue visual function in dystrophic RCS rats.

Lund RD, et al., Cloning Stem Cells. 2006 Fall;8(3):189-99.

Abstract: Embryonic stem cells promise to provide a well-characterized and reproducible source of replacement tissue for human clinical studies. An early potential application of this technology is the use of retinal pigment epithelium (RPE) for the treatment of retinal degenerative diseases such as macular degeneration. Here we show the reproducible generation of RPE (67 passageable cultures established from 18 different hES cell lines); batches of RPE derived from NIH-approved hES cells (H9) were tested and shown capable of extensive photoreceptor rescue in an animal model of retinal disease, the Royal College of Surgeons (RCS) rat, in which photoreceptor loss is caused by a defect in the adjacent retinal pigment epithelium. Improvement in visual performance was 100% over untreated controls (spatial acuity was approximately 70% that of normal nondystrophic rats) without evidence of untoward pathology. The use of somatic cell nuclear transfer (SCNT) and/or the creation of banks of reduced complexity human leucocyte antigen (HLA) hES-RPE lines could minimize or eliminate the need for immunosuppressive drugs and/or immunomodulatory protocols.

 

 

 


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