Elucidation of the liver pathophysiology of progressive familial intrahepatic cholestasis using patient-derived iPS cells

Abstract

Progressive familial intrahepatic cholestasis type 1 (PFIC1) is a cholestatic liver disease caused by the mutations in ATPase phospholipid transporting 8B1 (ATP8B1) gene. The precise mechanism by which mutations in the ATP8B1 gene, encoding a phospholipid flippase, trigger bile acid accumulation in liver remains elusive. Moreover, experimental animal models fail to replicate the bile acid toxicity observed in humans. Therefore, we attempted to recapitulates the liver pathophysiology of PFIC1 by using iPS cells established from PFIC1 patients (PFIC1-iPS cells). Firstly, hepatocytes and cholangiocytes were differentiated from PFIC1-iPS cells. In the coculture system consisting of PFIC1-iPS cell-derived hepatocytes and cholangiocytes, bile acid transport activity was significantly lower, with elevated expression of cytotoxicity markers, as compared to the coculture system consisting of wild-type (WT) iPS cell-derived hepatocytes and cholangiocytes. It is suggested that cholestasis is recapitulated using PFIC1-iPS cells. We also found that ATP8B1 mutations caused decrease in the hepatic differentiation capacity but did not affect cholangiocyte differentiation capacity. Additionally, RNA-sequencing analysis revealed that bile acid treatment-mediated activation of FXR signaling can be observed in WT-iPS cell-derived hepatocytes, but not in PFIC1-iPS cell-derived hepatocytes. This suggests that the responsiveness to the bile acid was impaired by ATP8B1 mutations. In conclusion, PFIC1-iPS cells can be a useful tool for understanding the liver pathophysiology of PFIC.