Small Molecules Screened via Conversion Kinetics Analyses Facilitate Single Factor-mediated Hepatic Transprogramming. Mus musculus

Recent studies have shown that defined hepatic factors could lead to the direct conversion of fibroblasts into induced hepatocytes (iHeps). However, reported conversion efficiencies are vey low and the underlying mechanism of the hepatic lineage conversion is largely unknown. Here, we report that direct conversion into iHeps is a stepwise transition involving erasure of somatic memory, mesenchymal-to-epithelial transition, and induction of hepatic cell fate in a sequential manner. Throughout screening for additional factors that could potentially enhance the kinetics of the MET and hepatic programs, we have found that c-Myc and Klf4 (CK) dramatically accelerate the conversion kinetics, resulting in remarkably improved generation of iHeps (>87 fold). Furthermore, we identified small molecules that could replace the roles of CK and thus led to the highly efficient generation of iHeps without CK. Finally, we show that a single factor (Hnf1α) supported by small molecules is sufficient to robustly induce transprogramming of fibroblasts into functional hepatocyte-like cells with high yield. This novel approach might help to fully elucidate the direct conversion process and also facilitate the translation of iHep into clinic. Overall design: Cells transduced with different combinations of factors were cultured in standard Hep medium. Epithelial colonies were observed within 5 days with much higher numbers in the presence of additional factor, c-Myc and Klf4, compared to control group, indicating the number of epithelial colony was dramatically increased in the presence of additional stem cell factors. In this study, the established iHep lines (4a3, 4a1CK, and 4a3CK at passage 10) were compared with MEFs and primary hepatocytes in whole transcriptome levels.