Project description:Inflammatory bowel diseases encompass gastrointestinal illnesseses typified by chronic inflammation, loss of epithelial integrity and gastrointestinal microbiota dysbiosis. In an effort to counteract these characteristic perturbations, we used stem cells and/or a probiotic preparation in a murine model of Dextran Sodium Sulfate induced colitis to examine both their efficacy in ameliorating disease and impact on niche-specific microbial communities of the lower GI tract. Colitis was induced in C57BL/6 mice by administering 3% DSS in drinking water for 10 days prior to administering one of three treatment plans: daily probiotic (VSL#3) supplementation for 3 days, a single tail vein injection of 1x106 murine mesenchymal stem cells, or both. Controls included DSS-untreated mice and DSS-treated mice that received no therapy. Ileal, cecal and colonic sections were collected for microbiota and histological analyses. Microbiota profiling revealed distinct bacterial community compositions in the ileum, cecum and colon of control untreated animals, all of which were predicted in silico to be enriched for a number of discrete KEGG pathways, indicating compositional and functional niche specificity in healthy animals. DSS- treatment perturbed community composition in all three niches with ileal communities exhibiting the greatest change relative to control animals. Stem cell, VSL#3 and the combination treated animals exhibited treatment-specific microbiota composition in the lower GI tract, though disease scores were only improved in VSL#3 treated animals. This VSL#3-associated shift in the ileal microbiota was characterized by significant Enterobacteriaceae enrichment compared to colitic animals (p<0.05), Mice (n=40) were randomly divided into five experimental groups, four of which received Dextran Sodium Sulfate (DSS; 3% solution in drinking water) for 10 days to induce colitis. Three of the DSS-treated groups received the following treatment modalities: VSL#3 (VSL#3, n=5), mesenchymal stem cells (MSC, n=5), or VSL#3 + mesenchymal stem cells (DUAL, n=5). The fourth DSS-treated group received no intervention (DSS; n=10). The additional fifth group of animals received neither DSS nor any therapeutic intervention and acted as untreated controls (CNTL, n=15). Following colitis induction (Day 10), DSS administration was halted and mice in the VSL#3, MSC and DUAL groups received the following interventions respectively: daily oral supplementation with 5x106 CFUs per supplement of VSL#3 in 100ul PBS (VSL#3); a single tail vein injection of 1x106 murine mesenchymal stem cells in 100_l PBS on Day 10 (MSC) or a combination of both treatments To provide control data for comparison, CNTL mice (n=5 per time point) were euthanized and sampled on days 1, 10, and 14, while DSS mice (n=5 per time point) were euthanized on days 10 and 14. All MSC, VSL#3, and DUAL mice were euthanized on Day 14. Samples collected from each animal included terminal ileum (1cm proximal to the cecum), cecum (divided transversely and stored as two separate samples), and proximal colon. All samples were added to RNAlater, prior to storage at -80C for analysis. Additional colonic samples were obtained, proximal to the initial sample site for microbiome analyses, and were preserved in paraformaldehyde for histological analyses.

Project description:The preferential localization of some neoplasms, such as serrated polyps, in specific areas of the intestine suggests that non-genetic factors may be important for their development. To test this hypothesis, we took advantage of transgenic mice that expressed HB-EGF throughout the intestine, but develop serrated polyps only in the cecum. Here we show that a host-specific microbiome was associated with serrated polyps, and that alterations of the microbiota induced by antibiotic treatment or by embryo-transfer rederivation markedly inhibited the formation of serrated polyps in the cecum. Mechanistically, development of serrated polyps was associated with a local decrease in epithelial barrier-function, bacterial invasion, production of antimicrobials, and increased expression of several inflammatory factors such as IL-17, Cxcl2, Tnf-Œ±, and IL-1. Increased number of neutrophils were found within the serrated polyps, and their depletion significantly reduced polyp growth. Together these results indicate that non-genetic factors contribute to the development of serrated polyps and suggest that the development of these intestinal neoplasms in the cecum is driven by the interplay between genetic changes in the host, an inflammatory response, and a host-specific microbiota. SUMMARY: Serrated polyps (SP) are a heterogeneous group of neoplasms found in particular areas of the gut. To define the factors contributing to their specific localization, we analyzed a strain of transgenic mice that carry a genetic alteration throughout the intestinal epithelium, but only develop SP in the cecum. Transcriptome and immunostaining analyses showed increased expression of antimicrobial genes, inflammatory factors, and the presence of bacteria within SP. Alteration of the cecal microbiota by antibiotic treatment or by embryo-transfer rederivation dramatically reduced SP incidence. Microbiome analysis implicated a limited set of bacteria in the development of SP. Together, these results point to a crucial role for the microbiota in the localized development of SP in a genetically susceptible host. We obtained serrated polyp (SP) and surrounding normal (NM) tissue from the ceca of three affected mice (paired design) and assessed expression differences by RNA-Seq.

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