METTL3 Potentiates Corneal Allograft Rejection via Increased Pro-Inflammatory Cytokine Production and Aerobic Glycolysis.

PURPOSE: Allograft rejection is a primary cause of corneal transplantation failure. This study aims to investigate the role and underlying mechanisms of methyltransferase-like 3 (METTL3) in corneal allograft rejection. METHODS: The expression of N6-methyladenosine (m6A)-related genes, including Mettl3, in corneal grafts was examined using RNA sequencing, real-time PCR, and immunofluorescence staining. Genetic and pharmacological approaches were used to inhibit METTL3 activity, and corneal transplantation outcomes were evaluated via slit-lamp biomicroscopy, ELISA, real-time PCR, lactate assays, Seahorse metabolic assays, and Western blot. The effect of METTL3 on the inflammatory response was further examined in bone marrow-derived dendritic cells (BMDCs) using genetic and pharmacological interventions. RESULTS: The transcriptional level of METTL3 was elevated in rejected corneal grafts and colocalized with immune cells. Pharmacological inhibition of METTL3 using STM2457, as well as genetic suppression via global Mettl3 knockdown (Mettl3-KD) in donor corneas or conditional knockout (cKO) of Mettl3 in donor dendritic cells (Mettl3-cKO), significantly delayed corneal allograft rejection. This protective effect was associated with suppressed mammalian target of rapamycin (mTOR) signaling and decreased glycolysis. Similarly, METTL3 inhibition in BMDCs, either by STM2457 treatment or Mettl3-KD, attenuated inflammatory responses, glycolytic activity, and mTOR signaling. CONCLUSIONS: Our findings highlight a critical role for METTL3 in promoting corneal transplant rejection. Targeting METTL3 may represent a potential therapeutic strategy to improve corneal allograft survival, providing valuable insights for future clinical translation.