Transient c-Src Suppression During Endodermal Commitment of Human Induced Pluripotent Stem Cells Results in Abnormal Profibrotic Cholangiocyte-Like Cells.

Directed differentiation of human induced pluripotent stem cells (iPSCs) toward hepatobiliary lineages has been increasingly used as models of human liver development/diseases. As protein kinases are important components of signaling pathways regulating cell fate changes, we sought to define the key molecular mediators regulating human liver development using inhibitors targeting tyrosine kinases during hepatic differentiation of human iPSCs. A library of tyrosine kinase inhibitors was used for initial screening during the multistage differentiation of human iPSCs to hepatic lineage. Among the 80 kinase inhibitors tested, only Src inhibitors suppressed endoderm formation while none had significant effect on later stages of hepatic differentiation. Transient inhibition of c-Src during endodermal induction of human iPSCs reduced endodermal commitment and expression of endodermal markers, including SOX17 and FOXA2, in a dose-dependent manner. Interestingly, the transiently treated cells later developed into profibrogenic cholangiocyte-like cells expressing both cholangiocyte markers, such as CK7 and CK19, and fibrosis markers, including Collagen1 and smooth muscle actin. Further analysis of these cells revealed colocalized expression of collagen and yes-associated protein (YAP; a marker associated with bile duct proliferation/fibrosis) and an increased production of interleukin-6 and tumor necrosis factor-α. Moreover, treatment with verteporfin, a YAP inhibitor, significantly reduced expression of fibrosis markers. In summary, these results suggest that c-Src has a critical role in cell fate determination during endodermal commitment of human iPSCs, and its alteration in early liver development in human may lead to increased production of abnormal YAP expressing profibrogenic proinflammatory cholangiocytes, similar to those seen in livers of patients with biliary fibrosis. Stem Cells 2019;37:306-317.