Abstract
Background
The appendix has been shown to be associated with the pathogenesis and health outcomes in inflammatory bowel diseases (IBD). Specifically, post appendectomy patients are found to be protective for development of ulcerative colitis (UC); however, mechanisms of appendix involvement remain unclear.
Aims
Our aim is to examine the microbes associated with the appendix of IBD patients by identifying changes in microbe abundance and interactions with the host in patient cecum luminal washes, collected from close to the neck of the appendix during colonoscopy. We hypothesize that microbes originating in the appendix of IBD patients, through interactions with host-cells in a disrupted microenvironment in the appendix, could contribute to the pathogenesis of UC.
Methods
Shotgun metagenomics was performed on cecum luminal washes of IBD patients and non-IBD controls. Guided by the metagenomic results, we performed gentamicin protection assays to determine virulence of microbes of interest using Caco2 intestinal epithelial cells. Co-culturing them with human host cells in vitro will identify relevant disease-related factors secreted by microbes and/or host cells using disease models and multiomic approaches.
Results
Shotgun metagenomics results showed that among numerous microbes, several bacterial taxa demonstrated differences in abundance between IBD and non-IBD patients: Flavonifractor, Bacteroide fragilis, and Alistipes represented 8%, 10%, and 21% abundance respectively in non-IBD patients, while in IBD patients they were present below 0.1%. In contrast, Bacteroide vulgatus and Escherichia coli were about 9% and 69% respectively, in IBD patients, whilst they were present at 1.7% and 1.2% in non-IBD patients, respectively. Following our recent method for validating pathobionts (Armstrong, 2019), we used the gentamicin protection assays to assess the ability of these bacteria to invade Caco2 cells, demonstrating a correlation between invasive potential of these microbes and cecal abundance. Mechanistic experiments, aimed at identifying factors impacting invasion, are in progress.
Conclusions
These results provide preliminary, but promising findings suggesting mechanisms by which microbiota possibly originating in the appendix may show altered virulence, which may be related to changes in the appendix microenvironment in IBD. With plans in place to increase our patient cohort we will validate these findings. Identifying and profiling these microbes in IBD patients can help improve the understanding of mechanisms underlying microenvironment changes within the appendix and the gut, which could shed light on the role of the appendix in IBD pathogenesis and clarify how microbes drive inflammation in IBD.
Funding Agencies
CIHR
DNA Methylation and Transcription Patterns in Intestinal Epithelial Cells From Pediatric Patients With Inflammatory Bowel Diseases Differentiate Disease Subtypes and Associate With Outcome
