Studies of ulcerative colitis with concomitant primary sclerosing cholangitis : Beyond the clinical phenotype

Inflammatory bowel disease (IBD) is a group of chronically relapsing immune-related disorders, engaging the gastrointestinal tract. Symptoms vary depending on inflammatory phenotype, but may include diarrhoea, bowel pain and weight loss. The two most common entities are Crohn's disease and ulcerative colitis (UC). A minority of IBD patients, particularly UC, is concomitantly affected by primary sclerosing cholangitis (PSC) – an inflammatory bile duct disease with dismal prognosis. IBD with associated PSC has distinct clinical features, and is regarded a unique IBD phenotype (PSC-IBD or PSC-UC). These features include higher rates of pancolitis, a milder clinical course, and an unexplained increased risk of colorectal neoplasia. This thesis aimed to compare immunological conditions in PSC-UC and UC, but also to search for molecular differences, potentially facilitating PSC-UC diagnosis. In paper I and II, we compared eosinophil and lymphocyte activation and regulation. PSC-UC had down-regulated mucosal eosinophil activity, during both flare and remission. Compared with UC, PSC-UC had a dampened, and less Th2 dominated mucosal immune response. This was evident by a low quote of CRTH2/CXCR3 CD4+ cells and a cytokine milieu with no upregulated Th2 cytokines. In contrast, PSC-UC had highly up-regulated cytokines in peripheral blood. Among these, sCD40 stood out as being most important for inter-group separation according to multivariate analysis. In paper III, we gave a detailed description of colonic tissue factor (TF) expression. We found discrepancies in TF depending on UC subtype and inflammatory status, where inflammation- associated TF up-regulation was detected in UC only. Also, we identified stromal TF deposition as a sensitive indicator of acute colitis. In paper IV, PSC-UC and UC intestinal proteomes were compared using LC-MS/MS. After detecting more than 7200 unique proteins in the discovery step, the top-five most distinctive findings were chosen for verification. Of these, AGPAT1 was verified, being significantly higher in PSC-UC. Despite phenotypical differences, the overall colonic proteome comparison showed high degree of concordance. In summary, this thesis demonstrates distinct immunological and molecular properties in PSC-UC, implying phenotypical features beyond clinical observations. Moreover, serum sCD40 and colonic AGPAT1 are suggested possible PSC-UC biomarkers.