METTL3–m6A–STAT1/NF-κB axis: a key switch for the immunosuppressive capacity of mesenchymal stem cells

Owing to their immunosuppressive nature, mesenchymal stem cells (MSCs)—a type of multipotent stem cell—hold considerable promise for therapeutic applications. Functioning as the primary catalytic subunit of the RNA N6-methyladenosine (m6A) methyltransferase complex, methyltransferase-like 3 (METTL3) plays extensive roles in numerous biological processes. It is hypothesized that METTL3 participates in governing the immunomodulatory functions inherent to MSCs. However, the exact mechanisms governing METTL3’s control over MSCs’ immunosuppressive capacity are poorly defined. MSCs extracted from bone marrow were transfected with lentivirus to knockdown or overexpress METTL3, while METTL3 enzyme activity was inhibited using the METTL3 inhibitor STM2457. In vitro co-culture assays and in vivo tumor models revealed that knocking down METTL3 or inhibiting its enzyme activity in MSCs weakened its inhibitory ability on T cells, while overexpressing METTL3 increased its inhibitory ability. in both concanavalin A (ConA)-induced liver injury and dextran sulfate sodium (DSS)-induced colitis models, the therapeutic benefits of MSCs against inflammatory diseases were shown to be dependent on METTL3 Our findings establish METTL3 as a critical regulator of the immunosuppressive capacity of MSCs, mediated through inducible nitric oxide synthase (iNOS) expression. Mechanistic investigations revealed that METTL3 targets JAK1, STAT1, TAB1, and NFKB1 in an IGF2BP1/2-dependent fashion. This regulatory influence stems from METTL3’s ability to potentiate STAT1 and NF-κB signaling pathways. Supporting this, overexpression of METTL3 enhanced NF-κB and STAT1 activation, which consequently elevated iNOS expression. METTL3 enhances MSC immunosuppression via the m6A–STAT1/NF-κB–iNOS axis, presenting a dual role: it potentiates therapeutic efficacy in inflammatory diseases but exacerbates tumor progression by impairing T-cell infiltration. Targeting METTL3 offers a strategy to optimize MSC-based therapies, though context-specific modulation is essential to balance benefits and risks.