Faecal microRNA as a biomarker of the activity and prognosis of inflammatory bowel diseases.

Reasons underlying the individual differences in the clinical manifestations of inflammatory bowel diseases (IBD) and the mechanism by which the host screens the intestinal microbiota remain unclear. The presence of miRNA in faeces might be a potential clue into differences in gut microbiota among these patients. In this study, we analysed the differences in miRNA levels in faecal samples from 117 patients diagnosed with IBD. There was a significant difference in faecal miRNAs between healthy subjects and those with inactive IBD. Further analysis showed that some miRNAs might indicate the severity of IBD activity and prognosis. Sequencing analysis of the 16S RNA V4 region in faecal microbiota in these IBD patients revealed significant differences in the phylogenetic architecture between subjects with active or inactive IBD and between IBD patients and healthy subjects. Finally, in vitro studies showed that these differentially expressed miRNAs have different effects on the proliferative activity of the intestinal microorganisms Fusobacterium nucleatum (Fn), Escherichia coli (E. coli) and segmental filamentous bacteria (SFB). We observed the dynamic uptake of miRNA by these bacteria using flow cytometry. This study reveals a potential link between faecal miRNA, intestinal microbiota, IBD activity and prognosis.