Absence of the intestinal microbiota exacerbates hepatobiliary disease in a murine model of primary sclerosing cholangitis

Abstract

Introduction Primary sclerosing cholangitis (PSC) is a chronic, idiopathic, fibro-inflammatory cholangiopathy. The role of the microbiota in PSC etiopathogenesis may be fundamentally important yet remains obscure. We tested the hypothesis that germ-free (GF) mdr2−/− mice develop a distinct PSC phenotype compared to conventionally-housed (CV) mdr2−/− mice. Methods Mdr2−/− mice (n=12) were re-derived as GF by embryo transfer, maintained in isolators, and sacrificed at 60 days in parallel with age-matched CV mdr2−/− mice. Serum biochemistries, gallbladder bile acids, and liver sections were examined. Histologic findings were validated morphometrically, biochemically, and by immunofluorescence microscopy (IFM). Cholangiocyte senescence was assessed by p16INK4a in situ hybridization in liver tissue and by β-galactosidase (SA-β-gal) staining in a culture-based model of insult-induced senescence. Results Serum biochemistries, including alkaline phosphatase, aspartate aminotransferase, and bilirubin, were significantly higher in GF mdr2−/− (p<0.01). Primary bile acids were similar, while secondary bile acids were absent in GF mdr2−/− mice. Fibrosis, ductular reaction, and ductopenia were significantly more severe histopathologically in GF mdr2−/− mice (p<0.01) and were confirmed by hepatic morphometry, hydroxyproline assay, and IFM. Cholangiocyte senescence was significantly increased in GF mdr2−/− mice and abrogated in vitro by ursodeoxycholic acid treatment. Conclusions GF mdr2−/− mice exhibit exacerbated biochemical and histologic features of PSC and increased cholangiocyte senescence, a characteristic and potential mediator of progressive biliary disease. Ursodeoxycholic acid, a commensal microbial metabolite, abrogates senescence in vitro. These findings demonstrate the importance of the commensal microbiota and its metabolites in protecting against biliary injury and suggest avenues for future studies of biomarkers and therapeutic interventions in PSC.

Gut microbiome and liver diseases

“…Investigators observed an increase in mucosal Barnesiellaceae at the family level and Blautia at the genus level. Germ-free, multidrug resistance 2 knockout mice (mdr2 −/− mice) show exacerbated biochemical and histological features of PSC and increased cholangiocyte senescence further supporting the notion that gut microbiota might play a role in disease process 65. Interestingly, primary bile acids were similar, whereas secondary bile acids were absent in germ-free mdr2 −/− mice.…”

Mechanisms of decompensation and organ failure in cirrhosis: From peripheral arterial vasodilation to systemic inflammation hypothesis

“…Hepatotoxins cause more liver injury and fibrosis in germ-free than in wild-type mice [78]. Consistently, a mouse model of primary sclerosing cholangitis shows exacerbated hepatobiliary damage under germ-free conditions [79].…”

The gut microbiota, bile acids and their correlation in primary sclerosing cholangitis associated with inflammatory bowel disease

“…7 Data from basic and clinical studies have long supported the hypothesis that the intestinal microbiota may have a role in PSC pathogenesis. [8][9][10] Recently, studies using next-generation sequencing have reported a distinct fecal or mucosal microbiota composition in PSC-IBD patients. [11][12][13][14][15][16][17][18] There is a close interplay between gut flora and BA metabolism.…”