Targeting m6A writer METTL3 with engineered nanovesicles reduces neuroinflammation in vitro and in vivo

Abstract Epigenetic editing, particularly N 6 -methyladenosine (m 6 A) modification, represents a promising therapeutic strategy by silencing genes without altering DNA sequence. However, in vivo epigenetic intervention of neuroinflammation remains challenging and has rarely been explored. Here we developed a hybrid epigenetic nanomodulator, siMETTL3-hNVs, by integrating natural microglia-derived nanovesicles (NVs) with synthetic liposomes pre-loading small interfering RNA targeting the m 6 A writer methyltransferase-like 3 (METTL3). Natural NVs enabled siMETTL3-hNVs to achieve inflamed-brain delivery through CCR2-CCL2 chemotaxis and caveolae-mediated transcytosis across the blood-brain barrier. More importantly, relying on abundant cytokine receptors on the NVs, siMETTL3-hNVs served as decoys to neutralize pro-inflammatory cytokines, synergizing with the intracellular silencing of METTL3 to drive microglial M2 repolarization. In female mouse models of acute neuroinflammation and radiation-induced brain injury, siMETTL3-hNVs treatment significantly reduced cytokine levels, attenuated hippocampal damage, and ameliorated cognitive deficits. This work overcomes critical delivery bottlenecks in m 6 A-based therapeutics and establishes a robust strategy for epigenetic reprogramming of neuroinflammation.