Small Molecules Facilitate Single Factor-Mediated Hepatic Reprogramming

Recent studies have shown that defined factors could lead to the direct conversion of fibroblasts into induced hepatocyte-like cells (iHeps). However, reported conversion efficiencies are very low, and the underlying mechanism of the direct hepatic reprogramming is largely unknown. Here, we report that direct conversion into iHeps is a stepwise transition involving the erasure of somatic memory, mesenchymal-to-epithelial transition, and induction of hepatic cell fate in a sequential manner. Through screening for additional factors that could potentially enhance the conversion kinetics, we have found that c-Myc and Klf4 (CK) dramatically accelerate conversion kinetics, resulting in remarkably improved iHep generation. Furthermore, we identified small molecules that could lead to the robust generation of iHeps without CK. Finally, we show that Hnf1α supported by small molecules is sufficient to efficiently induce direct hepatic reprogramming. This approach might help to fully elucidate the direct conversion process and also facilitate the translation of iHep into the clinic. [Display omitted] •Direct conversion process toward iHeps is a sequential transition•MET activation facilitates the robust iHep generation in mouse and human•Hnf1α alone is sufficient for hepatic conversion in the presence of small molecules•Hnf1α-derived iHeps represent the more mature hepatic state Lim et al. uncover the underlying mechanisms of direct hepatic reprogramming by deciphering the conversion kinetics. Activation of MET improves iHep generation with accelerated conversion kinetics. Hnf1α alone is sufficient to robustly generate functional iHeps in the presence of small molecules, and Hnf1α-derived iHeps represent the more mature hepatic state.