Taurocholate induces biliary differentiation of liver progenitor cells causing hepatic stellate cell chemotaxis in the Ductular Reaction: Role in pediatric cystic fibrosis liver disease

Cystic fibrosis liver disease (CFLD) in children causes progressive fibrosis leading to biliary cirrhosis, however its cause(s) and early pathogenesis are unclear. We hypothesised that a bile acid-induced Ductular Reaction (DR) drives fibrogenesis. We evaluated the DR by cytokeratin-7 immunohistochemistry in liver biopsies, staged for fibrosis, from 60 children with CFLD and demonstrated that the DR was significantly correlated with hepatic fibrosis stage and biliary taurocholate levels. To examine the mechanisms involved in DR induction liver progenitor cells (LPCs) were treated with taurocholate and key events in DR evolution were assessed: LPC proliferation, LPC biliary differentiation and hepatic stellate cell (HSC) chemotaxis. Taurocholate induced a time-dependent increase in LPC proliferation and expression of genes associated with cholangiocyte differentiation (cytokeratin-19, connexin-43, integrin-β4 and γ-glutamyltranspeptidase [GGT]), while the hepatocyte specification marker HNF4α was suppressed. Functional cholangiocyte differentiation was demonstrated via increased acetylated α-tubulin and SOX9 proteins, the number of primary cilia(+) LPCs and increased active GGT enzyme secretion. Taurocholate induced LPCs to release MCP-1, MIP1α and RANTES into conditioned medium causing HSC chemotaxis, which was inhibited by anti-MIP1α. Immunofluorescence confirmed chemokine expression localized to CK7(+) DR and LPCs in CFLD liver biopsies. This study suggests that taurocholate is involved in initiating functional LPC biliary differentiation and the development of the DR, with subsequent induction of chemokines that drive HSC recruitment in CFLD.