Gastroenterology

Gastroenterology

Volume 127, Issue 1, July 2004, Pages 261-274
Gastroenterology

Basic-liver, pancreas, and biliary tract
Regurgitation of bile acids from leaky bile ducts causes sclerosing cholangitis in Mdr2 (Abcb4) knockout mice

This article is dedicated to the 70th birthday of Professor Dr. Gustav Paumgartner, Munich, Germany, and Neumarkt, Austria.
https://doi.org/10.1053/j.gastro.2004.04.009Get rights and content

Abstract

Background & Aims: Because the mechanisms leading to bile duct damage in sclerosing cholangitis are unknown, we aimed to determine the pathogenesis of bile duct injury in multidrug resistance gene (Mdr2) (Abcb4) knockout mice (Mdr2−/−) as a novel model of the disease. Methods: Mdr2−/− and wild-type controls (Mdr2+/+) were studied at 2, 4, and 8 weeks of age. Liver histology, ultrastructure, immunofluorescence microscopy (to study inflammatory cells, tight junction protein ZO-1, basement membrane protein laminin, fluorescence-labeled ursodeoxycholic acid), immunohistochemistry (for α-smooth muscle actin, nitrotyrosine), sirius red staining, bacterial cultures of intra-abdominal organs, and polymerase chain reaction (PCR) for Helicobacter bilis DNA were compared between both genotypes. Hepatic cytokine expression was determined by reverse-transcription PCR. Results: Bile ducts of Mdr2−/− showed disrupted tight junctions and basement membranes, bile acid leakage into portal tracts, induction of a portal inflammatory (CD11b, CD4-positive) infiltrate, and activation of proinflammatory (tumor necrosis factor [TNF]-α, interleukin [IL]-1β) and profibrogenic cytokines (transforming growth factor [TGF]-β1). This resulted in activation of periductal myofibroblasts, leading to periductal fibrosis, separating the peribiliary plexus from bile duct epithelial cells and, finally, causing atrophy and death of the bile duct epithelium. Bacterial translocation was not increased and H. bilis was not detectable in Mdr2−/−. Conclusions: Sclerosing cholangitis in Mdr2−/− mice is a multistep process with regurgitation of bile from leaky ducts into the portal tracts, leading to induction of periductal inflammation, followed by activation of periductal fibrogenesis, finally causing obliterative cholangitis owing to atrophy and death of bile duct epithelial cells.

Section snippets

Animals

Mdr2−/− knock-out and Mdr2+/+ wild-type mice (FVB/N background) were obtained from Jackson Laboratory (Jackson Laboratory, Bar Harbor, ME). Mice were housed with a 12-hour light-dark cycle and permitted ad libitum consumption of water and a standard mouse diet (Sniff, Soest, Germany). Livers from 2-, 4-, and 8-week-old male mice (n = 5–10 in each group owing to the small amounts of liver tissue in 2- and 4-week-old mice) were excised after cervical dislocation under general anesthesia (400 mg

Results

Severe bile duct epithelial cell (BEC) injury rarely is observed before week 4 in Mdr2−/−, 1 a time point when periductal inflammation and fibrosis, the hallmarks of the liver phenotype in this model, already are developed fully. Therefore, we established a detailed time course of the individual pathogenetic steps of sclerosing cholangitis in these animals.

Discussion

Because understanding of the pathogenesis of bile duct injury is a key prerequisite for the development of effective medical treatment for bile duct disorders including sclerosing cholangitis (e.g., primary sclerosing cholangitis [PSC]), we designed this study in Mdr2−/− as a model system to obtain novel insights into the pathogenetic principles of sclerosing cholangitis.1 We show that sclerosing cholangitis in Mdr2−/− is a multistep process initiated by leakage of bile acids from the bile

Acknowledgements

The authors thank Dr. Alan Hofmann (San Diego, California) for providing fluorescence-labeled bile acids; Dr. W. Erwa (Graz, Austria) and colleagues for performing liver function tests; and Judith Gumhold and Dagmar Silbert (Graz, Austria) for excellent technical assistance.

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    Supported by grants P-15502 (to M.T.) and P-15783 (to H.T.) from the Austrian Science Foundation and a GEN-AU project grant from the Austrian Ministry for Science (to M.T.).

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