• PRIMARY SCLEROSING CHOLANGITIS
• INFLAMMATORY BOWEL DISEASE
• ULCERATIVE COLITIS
• INTESTINAL MICROBIOLOGY
• EXPERIMENTAL COLITIS

The close association between primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) is an important starting point to understand PSC but may also be of interest to understand IBD. In Gut, Bedtke et al present an extensive set of experiments designed to test the impact of sclerosing cholangitis on IBD.1 The results show that both genetic and induced sclerosing cholangitis lead to less severe inflammation in the IL10 knock-out model of colitis. Second, Foxp3 expression is increased in the intestine of mice and humans with colitis and biliary disease, and a protective effect of sclerosing cholangitis is absent in a colitis model depleted of Foxp3⁺ T regulatory cells. Third, transfer of sclerosing cholangitis-associated and non-disease associated microbiome (of both murine and human origin) leads to less severe colitis induced by interleukin 10 receptor alpha (IL-10Ra) antibodies and dextran sulfate sodium, respectively. Taken together, these observations suggest that sclerosing cholangitis attenuate colitis, likely at least in part driven by sclerosing cholangitis-associated gut microbiota.

Clinically, it is well established that the IBD in PSC has particular features that may separate from classical ulcerative colitis or Crohn’s disease, including extensive colitis, right-sided dominance, rectal sparing and backwash ileitis.2 In line with the experimental data now presented, the IBD in PSC is often described as mild or quiescent. Besides the ‘milder’ IBD …