HucMSC-Ex alleviates DSS-induced colitis in mice by decreasing mast cell activation via the IL-33/ST2 axis

Background: Inflammatory bowel disease (IBD) is a chronic inflammatory disease that poses challenges in terms of treatment. The precise mechanism underlying the role of human umbilical cord mesenchymal stem cell-derived exosome (HucMSC-Ex) in the inflammatory repair process of IBD remains elusive. Mucosal mast cells accumulate within the intestinal tract and exert regulatory functions in IBD, thus presenting a novel target for addressing this intestinal disease.

Methods: A mouse model of Dextran Sulfate Sodium (DSS)-induced colitis was established and hucMSC-Ex were administered to investigate their impact on the regulation of intestinal mast cells. An in vitro co-culture model using the human clonal colorectal adenocarcinoma cell line (Caco-2) and human mast cell line (LAD2) was also established for further exploration of the effect of hucMSC-Ex.

Results: We observed the accumulation of mast cells in the intestines of patients with IBD as well as mice. In colitis mice, there was an upregulation of mast cell-related tryptase, interleukin-33 (IL-33), and suppression of tumorigenicity 2 receptor (ST2 or IL1RL1), and the function of the intestinal mucosal barrier related to intestinal tight junction protein was weakened. HucMSC-Ex treatment significantly reduced mast cell infiltration and intestinal damage. In the co-culture model, a substantial number of mast cells interact with the epithelial barrier, triggering activation of the IL-33/IL1RL1 (ST2) pathway and subsequent release of inflammatory factors and trypsin. This disruption leads to aberrant expression of tight junction proteins, which can be alleviated by supplementation with hucMSC-Ex.

Conclusion: Our results suggest that hucMSC-Ex may reduce the release of mast cell mediators via the IL-33/IL1RL1 (ST2) axis, thereby mitigating its detrimental effects on intestinal barrier function.