Survival of primary human hepatocytes and death of induced pluripotent stem cells in media lacking glucose and arginine

Metabolically purified human stem cell-derived hepatocytes reveal distinct effects of Ebola and Lassa viruses

Ebola and Lassa viruses require biosafety-level-4 (BSL4) containment, infect the liver, and cause deadly hemorrhagic fevers. The cellular effects of these viruses, and whether different families of hemorrhagic-fever viruses elicit similar effects, remain fundamental questions in BSL4 virology. Here, we introduce a new metabolic selection approach to create nearly-pure hepatocytes from human pluripotent stem cells, killing non-liver cells by withholding essential nutrients. Unexpectedly, Ebola and Lassa exerted starkly different effects on human hepatocytes. Ebola infection activated the integrated stress response (ISR) and WNT pathways in hepatocytes in vitro and killed them, whereas Lassa did not. Within non-human primates, Ebola likewise infected hepatocytes and activated ISR signaling in vivo . In summary, we present a single-cell transcriptional and chromatin accessibility roadmap of human hepatocyte differentiation, purification, and viral infection.

Lactate promotes survival and hepatocyte differentiation of human induced pluripotent stem cells in a medium without glucose and supplemented with galactose

Human induced pluripotent stem (iPS) cells initiate hepatocyte differentiation in a medium without glucose and supplemented with galactose, oncostatin M and small molecules [hepatocyte differentiation inducer (HDI)]. To clarify the metabolic differences between iPS cells in HDI and ReproFF (undifferentiated state), a metabolome analysis was performed. iPS cells were cultured in a medium without glucose and supplemented with galactose, as well as 1 mM of calcium lactate, sodium lactate or lactic acid. After 7 days of culture, the cells were subjected to reverse transcription-quantitative PCR analysis. The galactose-1-phosphate concentration was significantly higher in cells cultured in HDI than in those cultured with ReproFF. The lactate concentration in the HDI group was significantly lower than that in the ReproFF group. The expression levels of α-feto protein and albumin were significantly higher in the groups cultured with calcium lactate, sodium lactate and lactic acid as compared with ReproFF. It was suggested that lactate promoted the survival of iPS cells cultured in a medium without glucose and supplemented with galactose. Under these conditions, iPS cells begin to differentiate into a hepatocyte lineage. Lactate may be applied to produce hepatocytes from iPS cells more efficiently.

Metabolism-based cardiomyocytes production for regenerative therapy

Human pluripotent stem cells (hPSCs) are currently used in clinical applications such as cardiac regenerative therapy, studying disease models, and drug screening for heart failure. Transplantation of hPSC-derived cardiomyocytes (hPSC-CMs) can be used as an alternative therapy for heart transplantation. In contrast to differentiated somatic cells, hPSCs possess unique metabolic programs to maintain pluripotency, and understanding their metabolic features can contribute to the development of technologies that can be useful for their clinical applications. The production of hPSC-CMs requires stepwise specification during embryonic development and metabolic regulation is crucial for proper embryonic development. These metabolic features have been applied to hPSC-CM production methods, such as mesoderm induction, specifications for cardiac progenitors, and their maturation. This review describes the metabolic programs in hPSCs and the metabolic regulation in hPSC-CM production for cardiac regenerative therapy.

Multi-platform NMR Study of Pluripotent Stem Cells Unveils Complementary Metabolic Signatures towards Differentiation

Stem cells, poised to revolutionize current medicine, stand as major workhorses for monitoring changes in cell fate. Characterizing metabolic phenotypes is key to monitor in differentiating cells transcriptional and epigenetic shifts at a functional level and provides a non-genetic means to control cell specification. Expanding the arsenal of analytical tools for metabolic profiling of cell differentiation is therefore of importance. Here, we describe the metabolome of whole pluripotent stem cells (PSCs) using high‐resolution magic angle spinning (HR-MAS), a non-destructive approach for Nuclear Magnetic Resonance (NMR) analysis. The integrated ¹H NMR analysis results in detection of metabolites of various groups, including energy metabolites, amino acids, choline derivatives and short chain fatty acids. It unveils new metabolites that discriminate PSCs from differentiated counterparts and directly measures substrates and co-factors of histone modifying enzymes, suggesting that NMR stands as a strategic technique for deciphering metabolic regulations of histone post-translational modifications. HR-MAS NMR analysis of whole PSCs complements the much used solution NMR of cell extracts. Altogether, our multi-platform NMR investigation provides a consolidated picture of PSC metabolic signatures and of metabolic pathways involved in differentiation.

Innovation for hepatotoxicity in vitro research models: A review

Many categories of drugs can induce hepatotoxicity, so improving the prediction of toxic drugs is important. In vitro models using human hepatocytes are more accurate than in vivo animal models. Good in vitro models require an abundance of metabolic enzyme activities and normal cellular polarity. However, none of the in vitro models can completely simulate hepatocytes in the human body. There are two ways to overcome this limitation: enhancing the metabolic function of hepatocytes and changing the cultural environment. In this review, we summarize the current state of research, including the main characteristics of in vitro models and their limitations, as well as improved technology and developmental prospects. We hope that this review provides some new ideas for hepatotoxicity research.

Hepatocyte selection medium-enriched hepatocellular carcinoma cells are positive for α-fetoprotein and CD44

Tissues surrounding hepatocellular carcinomas (HCCs) lack glucose. Hepatocyte selection medium (HSM) is deficient in glucose and is supplemented with galactose. HCC cells were cultured in HSM to investigate the stem cell markers α-fetoprotein (AFP) and cluster of differentiation 44 (CD44). HCC cells (HLF and PLC/PRF/5 cells) were cultured in HSM. Viable cell numbers were determined on days 0 and 7 following culture in HSM. RNA was isolated and subjected to reverse transcription-quantitative PCR (RT-qPCR) to analyze the mRNA expression levels of AFP and CD44. Immunostaining was performed to analyze the protein levels of AFP and CD44. The number of viable cells was significantly decreased on day 7 following culture in HSM. The expression levels of AFP and CD44 increased on day 7 as assessed using RT-qPCR. Immunostaining confirmed the results of RT-qPCR analysis. The number of viable HCC cells was decreased in HSM, whereas the expression levels of AFP and CD44 increased. Therefore, HSM is potentially useful for the enrichment of HCC cells with cancer stem cell characteristics.

Differentiation of human induced pluripotent stem cells in William's E initiation medium supplemented with 3‑bromopyruvate and 2‑deoxy‑d‑glucose

Hepatocyte selection medium (HSM) is deprived of glucose and supplemented with galactose, and is based on Leibovitz's‑15 (L15) medium. HSM may promote the differentiation of human induced pluripotent stem (iPS) cells towards hepatocyte lineage. These culture conditions result in increased expression of galactokinase (GALK)‑1 and GALK2. However, iPS cells do not survive in HSM. Two potential alternatives to glucose deprivation are treatment with 3‑bromopyruvate (3BP), an analogue of pyruvate, and 2‑deoxy‑d‑glucose (2DG), an analogue of glucose. The promoters of GALK1 and GALK2 were subcloned using the pMetLuc2 reporter plasmid to make pMetLuc2/GALK1 and pMetLuc2/GALK2, respectively. 201B7 human iPS cells were transfected with the reporter plasmids, cultured in HSM and analyzed by luciferase assay. Furthermore, 201B7 cells were cultured in L15, William's E (WE) or Dulbecco's modified Eagle's medium/nutrient mixture F‑12 Ham (DF12) supplemented with 3BP, 2DG or a combination of the two, for 15 days, and subjected to reverse transcription‑quantitative polymerase chain reaction to measure the levels of α‑fetoprotein (AFP) mRNA expression. Metridia luciferase activity was significantly higher in cells cultured in HSM compared with those in ReproFF medium (P<0.05). 3BP and 2DG treatment, alone or in combination, decreased AFP expression levels in cells cultured in L15 and DF12. The combination of 3BP+2DG increased the expression levels of AFP in WE. Without 3BP or 2DG, AFP expression was higher in L15 compared with WE or DF12. The promoters of GALK1 and GALK2 were activated in 201B7 cells cultured in HSM, enabling survival using galactose as an energy source. 3BP and 2DG supplementation in WE medium may promote the differentiation of iPS cells to the hepatocyte lineage.

2‑Deoxy‑D‑glucose initiates hepatocyte differentiation in human induced pluripotent stem cells

To initiate hepatocyte differentiation in human induced pluripotent stem (iPS) cells, cells are cultured in a medium lacking glucose but supplemented with galactose (hepatocyte selection medium, HSM) or in medium supplemented with oncostatin M and small molecules (hepatocyte differentiation inducer, HDI). In the present study, 2‑Deoxy‑D‑glucose (2DG), an analogue of glucose, was utilized instead of glucose deprivation and the effect of 2DG supplementation on iPS differentiation was examined. First, 201B7 cells, an iPS cell line, were cultured in HSM or HDI media for 2 days and then subjected to reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) in order to analyze expression levels of established hepatocyte markers, including cytosolic aspartate aminotransferase (AST), mitochondrial AST, alanine aminotransferase (ALT), and glycerol kinase. mRNA expression levels of mitochondrial AST, ALT, and glycogen synthase significantly increased following culture in HSM and HDI compared with ReproFF media. Cytosolic AST mRNA expression levels significantly increased following culture in HDI compared with ReproFF media, but not in HSM. To test the effect of 2DG on iPS differentiation, 201B7 cells were cultured in ReproFF, a feeder‑free medium that retains pluripotency, supplemented with 2DG. Following 7 days of culture, the cells were subjected to RT‑qPCR to analyze expression levels of α‑fetoprotein (AFP), a marker of immature hepatocytes. AFP mRNA expression levels significantly increased with the addition of 0.1 µM 2DG in the media, and galactose addition acted synergistically with 2DG to further upregulate AFP expression. In conclusion, the present study demonstrated that hepatocyte differentiation was initiated in iPS cells cultured in HSM and HDI media and that 2DG could be used as a supplement instead of glucose deprivation to initiate hepatocyte differentiation in iPS cells.

Oncostatin M in William's E medium is suitable for initiation of hepatocyte differentiation in human induced pluripotent stem cells

William's E (WE) is a suitable medium for the differentiation of human induced pluripotent stem (iPS) cells to the hepatocyte lineage. The aim of the present study was to investigate various growth factors in their ability to promote hepatocyte differentiation of iPS cells in WE medium. Human iPS 201B7 cells were cultured in WE medium supplemented with growth factors, and mRNA expression levels and promoter activities of α‑fetoprotein (AFP) and albumin were examined by reverse transcription‑quantitative polymerase chain reaction and luciferase assay, respectively. In addition, time course analysis of AFP mRNA expression was performed in 201B7 cells cultured in WE medium supplemented with oncostatin M. The results demonstrated that mRNA expression levels of AFP were significantly elevated by most growth factors tested as supplements in WE medium, except all‑trans retinoic acid, compared with cells cultured in ReproFF (a medium that maintains pluripotency). The highest increase in AFP mRNA expression levels was observed by oncostatin M stimulation. Albumin mRNA expression levels were increased by all‑trans retinoic acid and insulin‑transferrin‑selenium supplementation in WE medium compared with cells cultured in ReproFF. Oncostatin M supplementation significantly stimulated the promoter activity of the AFP gene, but no growth factor tested significantly stimulated the promoter activity of the albumin gene. By time course analysis, significant increase of AFP mRNA expression was observed on the sixth day post‑stimulation, compared with cells cultured in WE medium alone. In conclusion, the present study demonstrated that oncostatin M supplementation in WE medium was sufficient to initiate hepatocyte differentiation in iPS cells.

Proliferation of sphere-forming hepatocellular carcinoma cells is suppressed in a medium without glucose and arginine, but with galactose and ornithine

Resistance to sorafenib in hepatocellular carcinoma (HCC) cells exhibiting stemness was evaluated using a sphere formation assay. A hepatocyte selection medium (HSM) deficient in glucose and arginine was used to suppress the proliferation of cell spheres composed of HLF and PLC/PRF/5 HCC cells, which were subjected to a sphere formation assay. Cell spheres were cultured with sorafenib and subjected to a cell proliferation assay and the expression levels of cytochrome P450 (CYP3A4) were analyzed in RNA extracted from sphere-forming cells using reverse transcription-quantitative polymerase chain reaction. Sphere-forming PLC/PRF/5 cells were more resistant to sorafenib, as compared with control cells, exhibiting higher expression levels of CYP3A4. When cultured in HSM, suppressed proliferation was observed in the sphere-forming PLC/PRF/5 cells and in the control cells, with no significant variation between them. The results suggest that deprivation of glucose and arginine is a potential novel treatment for HCC.

Proliferation and motility of hepatocellular, pancreatic and gastric cancer cells grown in a medium without glucose and arginine, but with galactose and ornithine

Human primary hepatocytes are able to survive in a medium without glucose and arginine, but supplemented with galactose and ornithine (hepatocyte selection medium; HSM). To address the possibility of the application of HSM in cancer therapy, hepatocellular carcinoma cells, pancreatic cancer cells and gastric cancer cells were cultured in HSM. Cell proliferation was analyzed using an MTS assay. Morphological changes were analyzed using hematoxylin and eosin staining. Apoptosis was analyzed using a TUNEL assay and cell motility was assessed with a scratch assay. Cell proliferation was significantly suppressed in cell lines grown in HSM (P<0.01 in all the cell lines). Hematoxylin and eosin staining revealed pyknotic nuclei, suggesting that these cells had undergone apoptosis. The number of TUNEL-positive cells was significantly increased in HSM. In the scratch assay, the distance between the growing edge and the scratched edge was significantly lower (P<0.01 in all the cell lines) in cells cultured in HSM, compared with those grown in Dulbecco's modified Eagle's medium or RPMI-1640. Therefore, the proliferation and motility of hepatocellular carcinoma cells, pancreatic cancer cells and gastric cancer cells was suppressed, and these cells subsequently underwent apoptosis in a medium without glucose and arginine, but containing galactose and ornithine.

Dormant Pluripotent Cells Emerge during Neural Differentiation of Embryonic Stem Cells in a FoxO3-Dependent Manner

One major concern over the clinical application of embryonic stem cell (ESC)-derived cells is the potentiation of latent tumorigenicity by residual undifferentiated cells. Despite the use of intensive methodological approaches to eliminate residual undifferentiated cells, the properties of these cells remain elusive. Here, we show that under a serum-free neural differentiation condition, residual undifferentiated cells markedly delay progression of their cell cycle without compromising their pluripotency. This dormant pluripotency was maintained during reculture of the cells under a serum-free condition, whereas upon serum stimulation, the cells exited the dormant state and restarted proliferation and differentiation into all three germ layers. Microarray analysis revealed a set of genes that is significantly upregulated in the dormant ESCs compared with their levels of regulation in proliferating ESCs. Among them, we identified the transcription factor Forkhead box O3 (FoxO3) to be an essential regulator of the maintenance of pluripotency in dormant ESCs. Our study demonstrates that the transition into the dormant state endows residual undifferentiated cells with FoxO3-dependent and leukemia inhibitory factor/serum-independent pluripotency.

Cell death in a co-culture of hepatocellular carcinoma cells and human umbilical vascular endothelial cells in a medium lacking glucose and arginine

Human primary hepatocytes are able to survive in a medium without glucose and arginine that is instead supplemented with galactose and ornithine (hepatocyte selection medium; HSM). This is because the cells produce glucose and arginine by the action of galactokinase (GALK) and ornithine carbamoyltransferase (OTC), respectively. It was expected that hepatocellular carcinoma (HCC) cells do not survive in HSM. In the current study, HCC cell lines (namely HLE, HLF, PLC/PRL/5, Hep3B and HepG2) and human umbilical vascular endothelial cells (HUVECs) were cultured in HSM, and the expression levels of GALK1, GALK2 and OTC were analyzed by reverse transcription-quantitative polymerase chain reaction. HLE, HLF and PLC/PRL/5 cells died on day 11, while Hep3B, HepG2 and HUVECs died on day 7. HLF cells were further analyzed as these cells had lower expression levels of GALK1, GALK2 and OTC compared with adult liver cells, and survived until day 11. In these cells, the expression levels of GALK1, GALK2 and OTC did not change on days 3 and 7 as compared to day 0. In addition, a co-culture of HLF cells with HUVECs was established and the medium was changed to HSM. It was observed that HLF cells and HUVECs in co-culture were damaged in HSM. In summary, HCC cells and HUVECs died in a medium without glucose and arginine that was supplemented with galactose and ornithine. HCC cells and HUVECs were damaged in HSM, suggesting a potential application for treatment with the medium.

Enrichment of Pluripotent Stem Cell-Derived Hepatocyte-Like Cells by Ammonia Treatment

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are potential resources for the regeneration of defective organs, including the liver. However, some obstacles must be overcome before this becomes reality. Undifferentiated cells that remain following differentiation have teratoma-forming potential. Additionally, practical applications require a large quantity of differentiated cells, so the differentiation process must be economical. Here we describe a DNA microarray-based global analysis of the gene expression profiles of differentiating human pluripotent stem cells. We identified differences and commonalities among six human pluripotent stem cell lines: the hESCs KhES1, KhES2, KhES3, and H1, and the iPSCs 201B7 and 243G1. Embryoid bodies (EBs) formed without requiring supplementation with inducing factors. EBs also expressed some liver-specific metabolic genes including the ammonia-metabolizing enzymes glutamine synthetase and carbamoyl-phosphate synthase 1. Real-time PCR analysis revealed hepatocyte-like differentiation of EBs treated with ammonia in Lanford medium. Analysis of DNA microarray data suggested that hepatocyte-like cells were the most abundant population in ammonia-treated cells. Furthermore, expression levels of undifferentiated pluripotent stem cell markers were drastically reduced, suggesting a reduced teratoma-forming capacity. These results indicate that treatment of EBs with ammonia in Lanford medium may be an effective inducer of hepatic differentiation in absence of expensive inducing factors.

Improved Survival and Initiation of Differentiation of Human Induced Pluripotent Stem Cells to Hepatocyte-Like Cells upon Culture in William's E Medium followed by Hepatocyte Differentiation Inducer Treatment

BACKGROUND

Hepatocyte differentiation inducer (HDI) lacks both glucose and arginine, but is supplemented with galactose and ornithine, and is added together with other reagents such as apoptosis inhibitor and oncostatin M. Although human induced pluripotent stem (iPS) cells initiate hepatocyte differentiation, most die within 7 days. In this study, we investigated both HDI and conventional media for their potential to improve cell survival.

MATERIALS AND METHODS

201B7 iPS cells were cultured in conventional media. This consisted of three cycles of 5-day culture in William's E (WE) medium, followed by a 2-day culture in HDI.

RESULTS

Expression levels of α-feto protein (AFP) were higher in cells cultured in WE and in Dulbecco's Modified Eagle's Medium/Nutrient F-12 Ham (DF12). 201B7 cells expressed the highest AFP and albumin (ALB) when cultured in HDI for 2 days following 7-day culture in WE. After three cycles of 5-day culture in WE followed by 2 days in HDI, 201B7 cells expressed AFP and ALB 54 ± 2.3 (average ± standard deviation) and 73 ± 15.1 times higher, respectively, than those cultured in ReproFF (feeder-free condition).

CONCLUSION

201B7 cells survived culture in WE for 7 days followed HDI for 2 days. After three cycles of culture under these conditions, hepatocyte differentiation was enhanced, as evidenced by increased AFP and ALB expression.

Hepatocyte selection medium eliminating induced pluripotent stem cells among primary human hepatocytes

Hepatic insufficiency is a fatal liver disease with a significant decrease in functioning hepatocytes. If hepatocytes could be generated from human induced pluripotent stem (hiPS) cells and transplanted into patients with hepatic insufficiency, the disease may become curable. However, a major limitation to this therapeutic strategy is due to the tumorigenicity of hiPS cells and their ability to form cancer. Current methods for eliminating unwanted hiPS cells use genetic manipulation or reagents that are potentially hazardous for hepatocytes; therefore, revised methods are necessary and anticipated. Glucose and arginine are essential cell culture medium ingredients for the survival of most cells, including hiPS cells. However, hepatocytes can produce its own glucose and arginine through galactokinase and ornithine transcarbamylase, respectively. Therefore, it was hypothesized that unwanted hiPS cells could be eliminated in a medium without glucose and arginine, and supplemented with galactose and ornithine instead. This modified medium has been established as hepatocyte selection medium (HSM). So far, attempts to generate a pure colony of mature hepatocytes from hiPS cells have not been successful. After establishment of co-culture in HSM, primary human hepatocytes survive while hiPS cells die within three days. Our latest results regarding a modification of HSM will be introduced in this manuscript.

An Optimal Medium Supplementation Regimen for Initiation of Hepatocyte Differentiation in Human Induced Pluripotent Stem Cells

Human induced pluripotent stem (hiPS) cells are an ideal source for hepatocytes. Glucose and arginine are necessary for cells to survive. Hepatocytes have galactokinase (GALK), which metabolizes galactose for gluconeogenesis, and ornithine transcarbamylase (OTC), which converts ornithine to arginine in the urea cycle. Hepatocyte selection medium (HSM) lacks both glucose and arginine, but contains galactose and ornithine. Although human primary hepatocytes survive in HSM, all the hiPS cells die in 3 days. The aim of this study was to modify HSM so as to initiate hepatocyte differentiation in hiPS cells within 2 days. Hepatocyte differentiation initiating medium (HDI) was prepared by adding oncostatin M (10 ng/ml), hepatocyte functional proliferation inducer (10 nM), 2,2'-methylenebis (1,3-cyclohexanedione) (M50054) (100 μg/ml), 1× non-essential amino acid, 1× sodium pyruvate, nicotinamide (1.2 mg/ml), L-proline (30 ng/ml), and L-glutamine (0.3 mg/ml) to HSM. HiPS cells (201B7 cells) were cultured in HDI for 2 days. RNA was isolated, used as template for cDNA, and subjected to real-time quantitative polymerase chain reaction. Alpha-fetoprotein, γ-glutamyl transpeptidase, and delta-like 1 were upregulated. Expression of albumin was not observed. Expression of transcription factors specific to hepatocytes was upregulated. The expression of GALK2, OTC, and CYP3A4 were increased. In conclusion, differentiation of 201B7 cells to hepatoblast-like cells was initiated in HDI. Limitations were small number of cells were obtained, and the cells with HDI were not mature hepatocytes.

A human pluripotent stem cell surface N-glycoproteome resource reveals markers, extracellular epitopes, and drug targets

Detailed knowledge of cell-surface proteins for isolating well-defined populations of human pluripotent stem cells (hPSCs) would significantly enhance their characterization and translational potential. Through a chemoproteomic approach, we developed a cell-surface proteome inventory containing 496 N-linked glycoproteins on human embryonic (hESCs) and induced PSCs (hiPSCs). Against a backdrop of human fibroblasts and 50 other cell types, >100 surface proteins of interest for hPSCs were revealed. The >30 positive and negative markers verified here by orthogonal approaches provide experimental justification for the rational selection of pluripotency and lineage markers, epitopes for cell isolation, and reagents for the characterization of putative hiPSC lines. Comparative differences between the chemoproteomic-defined surfaceome and the transcriptome-predicted surfaceome directly led to the discovery that STF-31, a reported GLUT-1 inhibitor, is toxic to hPSCs and efficient for selective elimination of hPSCs from mixed cultures.

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496 cell surface N-glycoproteins on hPSCs

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N-glycosylation site identification dictates accessible epitopes

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>30 positive and negative selection markers for hPSCs are validated

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STF-31 is selectively toxic to hPSCs

Selective culture method for hepatocyte-like cells differentiated from human induced pluripotent stem cells

This study aimed to establish culture conditions which are able to give the differentiation of induced pluripotent (iPS) cells to hepatocytes. To this end, we examined the usefulness of a culture medium containing the components involved in the intermediary metabolism in the liver. More specifically, we examined the effect of the "modified L-15 medium" containing galactose, phenylalanine and ornitine, but deprived of glucose, tyrosine, arginine and pyruvic acid. The medium was altered according to changes in the expression of enzymes that participate in liver-specific pathways. After 25 days of differentiation, the differentiated cells expressed hepatocyte markers and drug-metabolizing enzymes. These expression levels were increased using modified L-15 medium. The survival of human fetal liver cells and the death of human fibroblasts were observed during culture in modified L-15 medium. Most of the cells that differentiated from human iPS cells using modified L-15 medium were stained by anti-human albumin antibody. These results suggest that iPS cells can be converted to high purity-differentiated hepatocytes by cultivating them in modified L-15 medium.