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Human embryonic stem cells (hESCs) have enormous potential as a source of cells for cell replacement therapies and as a model for early human development. In this study we examined the differentiating potential of hESCs into hepatocytes in two-and three-dimensional (2D and 3D) culture systems. Embryoid bodies (EBs) were inserted into a collagen scaffold 3D culture system or cultured on collagen-coated dishes and stimulated with exogenous growth factors to induce hepatic histogenesis. Immunofluorescence analysis revealed the expression of albumin (ALB) and cytokeratin-18 (CK-18). The differentiated cells in 2D and 3D culture system displayed several characteristics of hepatocytes, including expression of transthyretin, α-1-antitrypsin, cytokeratin 8, 18, 19, tryptophan-2,3-dioxygenase, tyrosine aminotransferase, glucose-6-phosphatase (G6P), cytochrome P450 subunits 7a1 and secretion of alpha-fetoprotein (AFP) and ALB and production of urea. In 3D culture, ALB and G6P were detected earlier and higher levels of urea and AFP were produced, when compared with 2D culture. Electron microscopy of differentiated hESCs showed hepatocyte-like ultrastructure, including glycogon granules, welldeveloped Golgi apparatuses, rough and smooth endoplasmic reticuli and intercellular canaliculi. The differentiation of hESCs into hepatocyte-like cells within 3D collagen scaffolds containing exogenous growth factors, gives rise to cells displaying morphological features, gene expression patterns and metabolic activities characteristic of hepatocytes and may provide a source of differentiated cells for treatment of liver diseases.

Human pluripotent embryonic stem cells (hESC) have great promise for research into human developmental biology and the development of cell therapies for the treatment of diseases. To meet the increased demand for characterized hESC lines, we present the derivation and characterization of five hESC lines on mouse embryonic fibroblast cells. Our stem cell lines are characterized by morphology, long-term expansion, and expression profiles of a number of specific markers, including TRA-1-60, TRA-1-81, alkaline phosphatase, connexin 43, OCT-4, NANOG, CXCR4, NODAL, LEFTY2, THY-1, TDGF1, PAX6, FOXD3, SOX2, EPHA2, FGF4, TAL1, AC133 and REX-1. The pluripotency of the cell line was confirmed by spontaneous differentiation under in vitro conditions. Whereas all of the cell lines expressed all the characteristics of undifferentiated pluripotent hESC, two of the cell lines carried a triploid karyotype.

Embryonic stem (ES) cells are considered to exist in a ground state if shielded from differentiation triggers. Here we show that FGF4 and TGFβ signaling pathway inhibitors, designated R2i, not only provide the ground state pluripotency in production and maintenance of naïve ES cells from blastocysts of different mouse strains, but also maintain ES cells with higher genomic integrity following long-term cultivation compared with the chemical inhibition of the FGF4 and GSK3 pathways, known as 2i. Global transcriptome analysis of the ES cells highlights augmented BMP4 signaling pathway. The crucial role of the BMP4 pathway in maintaining the R2i ground state pluripotency is demonstrated by BMP4 receptor suppression, resulting in differentiation and cell death. In conclusion, by inhibiting TGFβ and FGF signaling pathways, we introduce a novel defined approach to efficiently establish the ground state pluripotency.

Although human induced pluripotent stem cells (hiPSCs) hold great promise as a source of differentiated cells for vast therapeutic implications, many obstacles still need to be surmounted before this can become a reality. One obstacle, a robust feeder-and serum-free system to generate and expand hiPSCs in culture is still unavailable. Here, for the first time, we describe a novel establishment and maintenance culture technique that uses human dermal fibroblasts to generate hiPSCs by introducing four factors, Klf4, Oct4, Sox2, and c-Myc under serum-and feeder-independent conditions. We have used a serum replacement product, conditioned medium (CM), or feeder-free medium (FFM) supplemented with high elevated basicfibroblast growth factor in the absence or presence of Matrigel. Our FFM system in the presence of Matrigel enhanced the efficiency of alkaline phosphatase-positive colonies at a frequency at least 10-fold greater than the conventional method on feeder cells. The established hiPSCs are similar to human embryonic stem cells in many aspects including morphology, passaging, surface and pluripotency markers, normal karyotype, gene expression, ultrastructure, and in vitro differentiation. Such hiPSCs could be useful particularly in the context of in vitro disease modeling, pharmaceutical screening and in cellular replacement therapies once the safety issues have been overcome.

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Despite the enormous progress in studying definitive endoderm (DE) differentiation from human embryonic stem cells (hESCs), none of the reported protocols have produced a universal, cost-effective, and competent DE with the capability to further differentiate into endodermal derivatives. In this study, by using a 2-step differentiation strategy, we have treated hESCs for 1 day with "priming" small molecules (SM), [stauprimide, NSC-308848, rapamycin (Rapa), and/or CHIR] and for the next 3 days with "inducing" SM (LY294002, cymarin, IDE1, and/or IDE2) in conjunction with activin A. In the positive control group, we treated hESCs with Wnt3a (25 ng/mL) for 1 day and activin A (100 ng/mL; W/A100-A100) for the next 3 days. Gene expression analysis showed that treatment of hESCs with 100 nM Rapa and 50 ng/mL activin A (Rapa-A50) out of 25 combinations of factors gave rise to higher expressions of 2 DE-specific genes, SOX17 and FOXA2. Similar results were obtained after treating 2 other hESC lines with this regimen. To investigate the competency of Rapa-A50-induced DE for further differentiation into endodermal derivatives, these cells and W/A100-A100-induced DE cells (positive control) were further differentiated into pancreatic progenitors (PP), then into pancreatic endocrine (PE) cells using 5 previously described differentiation protocols. Gene analysis of differentiated cells showed that the established protocols were insufficient to enable universal differentiation into PE, whereas Rapa-A50-induced DE cells were more competent for PP differentiation in a protocol-dependent manner. Additionally, Rapa-A50-induced DE had the capability to differentiate into hepatocyte-like cells (HLCs) as efficiently as W/A100-A100-induced DE. These data have indicated that hESCs primed with Rapa, and induced by a lower concentration of activin A, could lead to DE that had the capability to further differentiate into HLCs and PP cells, but not PE cells. Thus, current protocols for the differentiation of DE into PE still need additional study.