OP33 Multi-omics analysis reveals specific bio-geographical and functional characteristics in inflammatory bowel disease intestinal mucosa

Abstract Background Anatomical location and extent of disease are main factors that affect inflammatory bowel disease (IBD) course and prognosis. No explanation is available for segmental intestinal involvement in either Crohn’s disease (CD) or ulcerative colitis (UC), or for selective segmental response to therapy or disease complications. Therefore, studying the cellular composition of different intestinal segments may provide pathophysiological insights into these phenomena. Methods We compared location-specific cell composition and function by Cytometry Time-of-Flight (CyTOF), gene expression and single-cell (sc) RNAseq data obtained from 3 independent cohorts of healthy donors and IBD patients during remission and flare-ups. Using CyTOF data (n = 38 biopsies), we built a high-resolution screening of immune cell behaviour along the intestine. We validated the findings with gene expression data of 370 samples, and expanded screening resolution by computational methodologies. We then tested a specific pathway in scRNAseq data (n = 10 paired biopsies from 5 patients) and validated its significance by cell-specific Significance Analysis of Microarrays (csSAM). Results We found a location along the intestine to be a dominant feature determining immune and non-immune cell composition. We observed that inflammation reduced anatomic segregation beyond cell infiltration, and decreased the ability to cope with oxidative stress. An upregulated IL-6 pathway in T regulatory cells in UC patients was recognised as sigmoid-specific compared with known inflammatory IL-6 roles in macrophages, as seen in the right colon. This observation may be linked to colonic perforations associated with anti-IL-6R treatment. Suppressor of cytokine signalling 3 (SOCS3) may control IL-6 location-specific action. Conclusion Our study displays a unique and comprehensive cell map of IBD in a location-specific context, providing potential explanations to unexplained clinical phenomena. These observations may allow to tailor therapies to affected areas with improved therapeutic index and efficacy.