Retaining mTeSR1 Medium during Hepatic Differentiation Facilitates Hepatocyte-Like Cell Survival by Decreasing Apoptosis

Background/Aims: Hepatocyte-like cells derived from human pluripotent stem cells could be an important cell source for hepatocyte transplantation. The present study investigated the effect of retaining mTeSR1 medium during hepatic differentiation on hepatocyte-like cells in vitro. Methods: Human embryonic stem cell line H1 were treated with activin A and bone morphogenetic protein 4 (BMP4) for definitive endoderm (DE) cell induction and subsequently treated with BMP2 and fibroblast growth factor 4 (FGF4) for early hepatic cell induction. Hepatocyte growth factor (HGF) and fibroblast growth factor (KGF) were added for early hepatic cell expansion and then mixed with oncostatin-M for maturation. During DE induction, 0%, 25%, 50% and 75% concentrations of mTeSR1 medium were separately added for early hepatic induction and expansion. For optimization, the expression levels of SRY-related HMG-box 17 (SOX17) and forkhead box A2 (FOXA2) at day 4, alpha fetoprotein (AFP) and hepatocyte nuclear factor 4α (HNF4α) at day 15, and albumin (ALB) at day 25 were quantified in differentiated cells by qRT-PCR. The ALB-positive cell proportion was measured by flow cytometry. Functional tests including ALB secretion and indocyanine green (ICG) angiography uptake and release by ELISA, urea production by urea assay kit, and glycogen storage ability by periodic acid Schif reaction (PAS) staining were performed in the differentiated cells. The induced pluripotent stem (iPS) cells were used to examine whether the optimized method was suitable for differentiating iPS cells. DE and hepatic markers were detected by immunostaining, and functional testing was performed as described above. Flow cytometry with an Annexin V-FITC apoptosis detection kit and fluorescence microscopy with Hoechst 33258 were used to analyze apoptosis in differentiated cells derived from H1 cells. Results: All differentiated cells with retention of 0%, 25%, 50% and 75% mTeSR1 expressed SOX17, FOXA2, AFP, HNF4α, and ALB, while higher expression levels were observed in differentiated cells in the 0% and 25% groups. The flow cytometry results showed that the proportion of ALB-positive differentiated cells derived from H1 cells was higher in the 25% mTeSR1 group than in other groups. However, no significant difference in ALB secretion, urea production, ICG uptake and release and glycogen storage ability was detected between the 25% and 0% groups. The iPS cells could differentiate into hepatocyte-like cells with 25% mTeSR1 retention. The apoptosis ratio of differentiated cells was lower in the 25% mTeSR1 group than in the 0% mTeSR1 group. Conclusion: Retaining 25% mTeSR1 medium during hepatic differentiation has been proposed to increase the percentage of ALB-positive cells and cell survival by decreasing cell apoptosis.