MSCs-exosomes Can Promote Macrophage M2 Polarisation via Exosomal miR-21-5p through Mesenteric Injection: A Promising Way to Attenuate Murine Colitis

Background and Aims Exosome-based therapies are gaining increasing attention, with growing evidence suggesting a link between alterations in mesentery adipose tissue [MAT] and intestinal disease in Crohn's disease [CD]. However, the specific mechanism by which mesenchymal stem cells [MSCs]-Exos may alleviate colitis through targeting MAT remains not fully understood.Methods Human umbilical cord MSCs [HucMSCs] were cultured to isolate the corresponding exosomes [HucMSCs-Exos], which were confirmed by their morphology, size distribution, and expression of markers. In vivo, 2,4,6-trinitrobenzenesulphonic acid [TNBS]- and dextran sodium sulphate [DSS]-induced mouse colitis models were used to detect the therapeutic effects of HucMSCs-Exos. Enzyme-linked immunosorbent assay [ELISA], quantitative reverse transcription-polymerase chain reaction [qRT-PCR], western blotting, and immunofluorescence determined the expression of key molecules. Luciferase reporter assay was used to confirm the relationship between miR-21-5p and SPRY2.Results Exosomes treatment through mesenteric injection demonstrated therapeutic effects on mesenteric inflammation and colitis. These therapeutic benefits were contingent on macrophages, significantly facilitating the M2 polarisation of mesenteric macrophages. The expression data from GSE159814 and GSE211008 revealed that exosomal miR-21-5p was enriched in HucMSCs-Exos and could be delivered to macrophages. Additionally, the results indicated that miR-21-5p could directly target the 3'UTR of SPRY2 and activate the phosphorylation of ERK to modify macrophage phenotypes. Mechanistically, exosomal miR-21-5p derived from HucMSCs could promote macrophage M2 polarisation via the SPRY2/ERK axis.Conclusion Mesenteric injection of HucMSCs-Exos significantly alleviates mesenteric inflammation and colitis by promoting mesenteric macrophage M2 polarisation, making it a promising approach to treat colitis and suggesting therapeutic potential role of exosomal miR-21-5p in CD. Graphical Abstract