No abstract

Inflammatory bowel diseases (IBD) are emerging globally, indicating that environmental factors may be important in their pathogenesis. Colonic mucosal epigenetic changes, such as DNA methylation, can occur in response to the environment and have been implicated in IBD pathology. However, mucosal DNA methylation has not been examined in treatment-naïve patients. We studied DNA methylation in untreated, left sided colonic biopsy specimens using the Infinium HumanMethylation450 BeadChip array. We analyzed 22 control (C) patients, 15 untreated Crohn’s disease (CD) patients, and 9 untreated ulcerative colitis (UC) patients from two cohorts. Samples obtained at the time of clinical remission from two of the treatment-naïve UC patients were also included into the analysis. UC-specific gene expression was interrogated in a subset of adjacent samples (5 C and 5 UC) using the Affymetrix GeneChip PrimeView Human Gene Expression Arrays. Only treatment-naïve UC separated from control. One-hundred-and-twenty genes with significant expression change in UC (> 2-fold, P < 0.05) were associated with differentially methylated regions (DMRs). Epigenetically associated gene expression changes (including gene expression changes in the IFITM1, ITGB2, S100A9, SLPI, SAA1, and STAT3 genes) were linked to colonic mucosal immune and defense responses. These findings underscore the relationship between epigenetic changes and inflammation in pediatric treatment-naïve UC and may have potential etiologic, diagnostic, and therapeutic relevance for IBD.

Objectives In patients with inflammatory bowel diseases (IBD), the presence of non-caseating mucosal granuloma is sufficient for diagnosing Crohn disease (CD) and may represent a specific immune response or microbial-host interaction. The cause of granulomas in CD is unknown and their association with the intestinal microbiota has not been addressed with high-throughput methodologies. Methods The mucosal microbiota from three different pediatric centers was studied with 454 pyrosequencing of the bacterial 16S rRNA gene and the fungal small subunit (SSU) ribosomal region in transverse colonic biopsy specimens from 26 controls and 15 treatment naïve pediatric CD cases. Mycobacterium avium subspecies paratuberculosis (MAP) was tested with real-time PCR. The correlation of granulomatous inflammation with C-reactive protein (CRP) was expanded to 86 treatment naïve CD cases. Results The CD microbiota separated from controls by distance based redundancy analysis (dbRDA; p=0.035). Mucosal granulomata found in any portion of the intestinal tract associated with an augmented colonic bacterial microbiota divergence (p=0.013). The granuloma based microbiota separation persisted even when research center bias was eliminated (p=0.04). Decreased Roseburia and Ruminococcus in granulomatous CD were important in this separation. However, principal coordinates analysis (PCoA) did not reveal partitioning of the groups. CRP levels above 1mg/dl predicted the presence of mucosal granulomata (OR: 28 [6–134.32]; 73% sensitivity, 91% specificity). Conclusions Granulomatous CD associates with microbiota separation and CRP elevation in treatment naïve children. However, overall dysbiosis in pediatric CD appears rather limited. Geographical/center bias should be accounted for in future multi-center microbiota studies.