HucMSC-sEV-derived miR-320d alleviates IBD by inhibiting macrophage ferroptosis through m6A-mediated BCAT2 upregulation.

N6-methyladenosine(m6A) modification has garnered significant attention due to its dynamic and reversible post-transcriptional regulation, playing a crucial role in the pathogenesis and progression of inflammatory bowel disease (IBD). Previous studies have demonstrated that human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-sEV) alleviate IBD severity by dampening excessive immune responses and fostering a balanced immune environment. Although hucMSC-sEV has been shown to alleviate IBD, whether its effects involve m6A modification remains unclear. Our findings reveal that hucMSC-sEV modulates m6A modification levels in macrophages and attenuates the inflammatory response in IBD by inhibiting the expression of m6A "eraser" ALKBH5 and "reader" YTHDF2. Branched chain amino acid transaminase 2 (BCAT2) was identified as a key target of hucMSC-sEV-mediated m6A modification, participating in the inhibition of ferroptosis in macrophages. Mechanistically, hucMSC-sEV increased the level of m6A modification by reducing the amount of ALKBH5 and YTHDF2 binding to the BCAT2 mRNA complex, thereby promoting BCAT2 expression and inhibiting ferroptosis in macrophages. We further identified that miR-320d is enriched in hucMSC-sEV and exerts its regulatory effects by targeting both ALKBH5 and YTHDF2. Taken together, these findings indicate that hucMSC-sEV delivers miR-320d to enhance BCAT2 m6A modification and expression, thereby inhibiting macrophage ferroptosis and alleviating inflammation. This finding provides a new theoretical basis for the application of engineered exosomes in the targeted treatment of IBD.