The Effect of Bile Acids on the Sub-epithelial Layer of Mouse Extrahepatic Bile Ducts

Background Objectives: Biliary atresia is a significant pediatric liver disease, and the major indication for pediatric liver transplant. The etiology and pathogenesis of the diseases are unknown. We previously showed that in a toxic model of biliary atresia, there is loss of cell to cell adhesions of the cholangiocytes and increased permeability. This could lead to bile leakage to the sub epithelial layer. We aimed to determine the effect of various bile acids on cholangiocytes and the sub epithelial layer.

Methods: Intact extrahepatic bile ducts were isolated from 3-day-old and adult mice. The ducts were placed on roller inserts and cultured for 24 hours with various bile acids including glycochenodeoxycholate (GCDCA), cholic acid and ursodeoxycholic acid (UDCA). At 24 hours, bile ducts were fixed and stained for haematoxylin and eosin, Masson’s Trichrome or immunofluorescence stain for keratin 19 and α-smooth muscle actin (α-SMA).

Results: Low concentrations of GCDCA resulted in the disruption of monolayer integrity and patchy lumen obstruction. Higher concentrations of GCDCA caused severe damage to the cholangiocytes. Also, UDCA seemed to ameliorate GCDCA effect with less lumen obstruction and less fibrosis compared to ducts that were treated with GCDCA alone.

Conclusion: Under physiologic conditions, cholangiocytes display a striking resistance to the high concentrations of toxic bile acids. In this study we found that exposing bile ducts to bile acids from the basolateral side resulted in considerable cholangiocyte damage and fibrosis. This may explain propagation of cholangiocyte injury and extra hepatic biliary tree fibrosis after initial cholangiocyte damage.