WNT signaling contributes to the extrahepatic bile duct proliferative response to obstruction in mice

Biliary obstruction and cholangiocyte hyperproliferation are important features of cholangiopathies affecting the large extrahepatic bile ducts (EHBD). The mechanisms underlying obstruction-induced cholangiocyte proliferation in the EHBD remain poorly understood. Developmental pathways, such as WNT signaling, have been implicated in regulating injury responses in many tissues, including the liver and bile ducts. To investigate the contribution of WNT signaling to the EHBD cholangiocyte proliferative response to obstructive injury, we conducted a comprehensive study using complementary in vivo and in vitro models with pharmacologic interventions and computational approaches. To model obstruction, we used bile duct ligation (BDL) in mice. Human and mouse biliary organoids and mouse biliary explants were used to investigate the effects of WNT activation and inhibition in vitro. We observed a rapid upregulation of WNT ligand expression associated with increased biliary proliferation following obstruction. Cholangiocytes were identified as both WNT ligand-expressing cells and WNT responsive cells. Inhibition of WNT signaling decreased cholangiocyte proliferation in vivo and in vitro, while activation increased proliferation. WNT proliferative effects on cholangiocytes were β-catenin-dependent. Our studies suggest that cholangiocyte-derived WNT ligands can activate canonical WNT signaling to induce proliferation after obstructive injury. These findings implicate the WNT pathway in injury-induced cholangiocyte proliferation within the EHBD.