Human umbilical cord-derived mesenchymal stem cells ameliorate experimental colitis by normalizing the gut microbiota.

Background: Crohn's disease (CD) is a chronic non-specific inflammatory bowel disease. Current CD therapeutics cannot fundamentally change the natural course of CD. Therefore, it is of great significance to find new treatment strategies for CD. Preclinical and clinical studies have shown that mesenchymal stromal cells (MSCs) are a promising therapeutic approach. However, the mechanism by which MSCs alleviate CD and how MSCs affect gut microbes are still unclear and need further elucidation.

Methods: We used 2,4,6-trinitrobenzenesulfonic acid (TNBS) to induce experimental colitis in mice and analysed the microbiota in faecal samples from the control group, the TNBS group and the TNBS + MSC group with faecal 16S rDNA sequencing. Subsequent analyses of alpha and beta diversity were all performed based on the rarified data. PICRUStII analysis was performed on the 16S rRNA gene sequences to infer the gut microbiome functions.

Results: MSC Treatment improved TNBS-induced colitis by increasing survival rates and relieving symptoms. A distinct bacterial signature was found in the TNBS group that differed from the TNBS + MSC group and controls. MSCs prevented gut microbiota dysbiosis, including increasing α-diversity and the amount of Bacteroidetes Firmicutes and Tenericutes at the phylum level and decreasing the amount of Proteobacteria at the phylum level. MSCs alleviated the increased activities of sulphur and riboflavin metabolism. Meanwhile some metabolic pathways such as biosynthesis of amino acids lysine biosynthesis sphingolipid metabolism and secondary bile acid biosynthesis were decreased in the TNBS group compared with the control group and the TNBS + MSC group CONCLUSIONS: Overall, our findings preliminarily confirmed that colitis in mice is closely related to microbial and metabolic dysbiosis. MSC treatment could modulate the dysregulated metabolism pathways in mice with colitis, restoring the abnormal microbiota function to that of the normal control group. This study provides insight into specific intestinal microbiota and metabolism pathways linked with MSC treatment, suggesting a new approach to the treatment of CD.