Regurgitation of bile acids from leaky bile ducts causes sclerosing cholangitis in Mdr2 (Abcb4) knockout mice.
OBJECTIVE
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 alpha-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]-alpha, interleukin [IL]-1beta) and profibrogenic cytokines (transforming growth factor [TGF]-beta1). 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.
Fickert
Peter
P
Deparment of Medicine, Medical University, Graz, Austria.
Fuchsbichler
Andrea
A
Wagner
Martin
M
Zollner
Gernot
G
Kaser
Arthur
A
Tilg
Herbert
H
Krause
Robert
R
Lammert
Frank
F
Langner
Cord
C
Zatloukal
Kurt
K
Marschall
Hanns-Ulrich
HU
Denk
Helmut
H
Trauner
Michael
M
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000818:Animals; D001647:Bile Acids and Salts / Q000009:adverse effects* / Q000276:immunology; D001649:Bile Duct Diseases / Q000276:immunology*; D001652:Bile Ducts / Q000503:physiopathology*; D015209:Cholangitis, Sclerosing / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology; D008107:Liver Diseases / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal
D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D001647:Bile Acids and Salts; C095122:multidrug resistance protein 3