EGFR activation in cholangiocytes promotes extrahepatic bile duct regeneration after injury

The EGF receptor family of 4 tyrosine kinases, EGFR and ERBB2-4, and their ligands regulate the development and homeostasis of digestive organs including the hepatobiliary system. It promotes intrahepatic cholangiocyte proliferation, bile duct development, and cholangiocarcinoma aggressiveness. The EGF signaling network's contribution to extrahepatic bile duct (EHBD), which is a distinct hepatobiliary entity, regeneration is poorly defined. This work aimed to determine the fundamental role of the EGF signaling network in the biliary proliferative response to EHBD obstruction.

We used mouse bile duct ligation to model obstructive EHBD injury, and human and mouse EHBD organoids for in vitro studies. We tested activating and inhibitory paradigms with recombinant EGF family ligands and receptor antagonists. Transcriptomic and immunohistochemistry analyses informed EGF signaling changes and cellular localization at homeostasis and after obstruction.

At homeostasis, the EHBD expressed EGFR ligands Tgfa, Btc, Hbegf, and Nrg4 in cholangiocytes, and Egf and Nrg2 in stromal cells. Erbb2 and Erbb3 were predominant receptors expressed in cholangiocytes, and Egfr in stromal cells at baseline. Post-injury, biliary hyperproliferation was associated with increased abundance of Tgfa, Btc, Hbegf, and Areg ligands and Egfr receptor in cholangiocytes with resulting EGFR activation. EGFR ligands induced biliary organoid growth, and inhibition of EGFR, not ERBB2, dampened organoid proliferation. EGFR inhibition in mice led to a decrease in the biliary proliferative response after EHBD obstruction.

The obstruction-induced biliary proliferation is EGFR-mediated, suggesting context-specific and receptor-specific EGF signaling network contribution to EHBD regeneration after injury.