P910 Emerging role of IL-33/ST2 and Gut Microbiota axis in the inflammatory process of ulcerative colitis patients with ileal pouch-anal anastomosis.

Lopetuso, L.R.(1)*;Vetrone, L.(1);Petito, V.(1);Pugliese, D.(1);Parisio, L.(1);Laterza, L.(1);Gasbarrini, A.(1);Scaldaferri, F.(1);Papa, A.(1);

(1)Fondazione Policlinico Universitario "A. Gemelli" IRCCS- Università Cattolica del Sacro Cuore, IBD Unit- Centro Malattie dell’Apparato Digerente - CEMAD, Roma, Italy;


IL-33/ST2 axis and gut microbiota are important factors in the pathogenesis of IBD with a potential reciprocal influence. IL-33/ST2 axis controls the mucosal healing process during intestinal inflammation. Pouchitis, after restorative proctocolectomy with ileal pouch-anal anastomosis, is the most common complication. We aimed to explore the potential correlation between mucosal cytokines and gut microbiota in the inflammatory process of pouchitis.


23 patients with ileal pouch-anal anastomosis were enrolled. 13 showed pouchitis and 10 a normal pouch. Mucosal samples were collected from the afferent ileal loop and from the pouch. Multiplex analysis for cytokines was performed. ELISA, western blot and IHC were run to assess IL-33/ST2 axis. Microbiota was analyzed by 16S ribosomal RNA gene amplicon pyrosequencing. Pouchitis Disease Activity Index and Pouchitis Histological Score were calculated. Multivariate analyses were run to generate transcriptional interaction networks and identify biomarkers for patients with inflamed pouches.


IL-1Ra, IL-6, IL-8, IL-17, IP-10, MCP-1, MIP-1a, MIP-1b were increased in the inflamed pouch vs. normal pouch. No differences were registered in samples from the afferent ileal loop. In pouchitis, IL-7 resulted reduced in the inflamed pouch vs. the ileal loop. In normal pouch, no differences were recorded. In pouchitis, IL-33 and ST2 protein levels were significantly reduced in the pouch vs. the ileal loop and resulted decreased vs. normal pouch. Full-length, bioactive IL33, ST2L and sST2 were expressed in all experimental groups; the cleaved, less active form of IL33 was increased only in pouchitis. IL-33 and ST2 stainings were less intense within the inflamed and ulcerated mucosa of pouchitis compared to the normal pouch and in close proximity to areas of re-epithelialization. Microbiota analysis showed a decreased biodiversity in pouchitis vs. normal pouch (both at pouch and ileal loop level). Lower levels of Verrucomicrobia and increased abundance of Actinobacteria were recorded in inflamed pouch vs normal pouch. In pouchitis, the ileal loop and the pouch showed decreased levels of Akkermansia muciniphila and augmented abundance of Collinsella vs. samples from the normal pouch. In pouchitis, multivariate analyses evidenced a significant inverse correlation between Collinsella e Collinsella aereofaciens abundance and ST2 levels.


Pouchitis and normal pouch are characterized by divergent inflammatory molecular pathways and microbial populations with a specific pattern between the pouch and afferent ileal loop. Our results suggest a potential role for IL-33/ST2 and gut microbiota axis in driving the gut mucosal wound healing in patients with ileal pouch-anal anastomosis.