Published online Dec 14, 2018. doi: 10.3748/wjg.v24.i46.5223
Peer-review started: September 19, 2018
First decision: November 1, 2018
Revised: November 13, 2018
Accepted: November 16, 2018
Article in press: November 16, 2018
Published online: December 14, 2018
Pathogenesis of inflammatory bowel disease (IBD) has not been clarified yet. The gut microbiota plays a key role in the maintenance of intestinal homeostasis and the development and activation of the host immune system. The causality between IBD and alterations in microbiota remains incompletely understood but one theory is that altered microbiota composition and function in IBD result in increased immune stimulation or enhanced mucosal permeability. On the other hand, microRNAs (miRNAs) have been involved in the pathogenesis of IBD and have been explored as biomarkers and therapeutic targets. It has been shown that miRNAs regulate specific genes associated with Crohn´s disease (CD).
Identification of host and microbiota alterations in individual patients should lead to selective target interventions. In this study, we first analyzed the faecal microbiota composition in CD patients at the time of diagnosis. Secondly, we compared miRNA expression in CD gut samples obtained from endoscopically normal and affected mucosa, in order to find a marker of active IBD.
In this study, we will use deep-sequencing methods to analyze the microbiota from patients with CD and healthy controls. Moreover, a miRNAs screening will be performed to identify individual miRNA involved in inflammation process that could serve as biomarkers for disease progression on therapeutic target.
We found significant differences in microbiota composition when comparing patients with CD compared to the control population. The major differences were found in microbial biodivertiy (Shannon Index). We also found a reduction in Firmicutes and an increase in Bacteroidetes. Clostridia class was also significantly reduced in Crohn’s disease group.
We found that active non-treated CD patients had a low Firmicutes/Bacteroidetes ratio, less biodiversity in the structure of microbial communities and a significantly different pattern on gut microbiota distribution. Moreover, microbiota metabolism was altered in CD patients compared to healthy subjects. This data strongly suggests that dysbiosis may play a role in the pathogenesis of CD. Three miRNAs have been found induced in affected mucosa vs non-affected mucosa in CD, indicating that miRNA profile may serve as a biomarker for active disease.
Additional studies are needed to validate the results obtained and to identify causative roles for the microbiota. The role of miRNAs in the pathogenesis or diagnosis of IBD, including CD must be established through deeper analysis and validation in circulating tissues.