Prmt6 Deficiency or Inhibition Restores Microglial Homeostasis and Promotes Scar-Limited Repair in Adult Spinal Cord...

Neonatal mice achieve scar-free healing after spinal cord injury (SCI) by restoring microglial homeostasis, unlike adults, where persistent microglial dyshomeostasis drives scar expansion through mechanisms that remain elusive. Using RNA sequencing, we identified protein arginine methyltransferase 6 (PRMT6) as a key regulator of this disparity, upregulated in activated microglia at adult SCI lesions but maintained at low levels in neonatal microglia after injury. In adult mice, Prmt6 deficiency restored microglial homeostasis, evidenced by increased P2Y12/TMEM119 and reduced CD68, while reducing scar formation and enhancing axonal regrowth and motor recovery. Microglia-specific Prmt6 knockdown or PRMT6 inhibitor administration recapitulated these effects. Mechanistically, PRMT6 deposits H3R2me2a at the Ppargc1a promoter to repress peroxisome proliferator-activated receptor-γ coactivator-1α（PGC-1α）, thereby inhibiting fatty acid oxidation (FAO) and disrupting microglial homeostasis. Loss of Prmt6 alleviates this epigenetic repression, restoring FAO and microglial homeostasis. These findings establish PRMT6 as a novel epigenetic regulator linking microglial dyshomeostasis and metabolic dysfunction to maladaptive scar formation in adult SCI, highlighting PRMT6 inhibition as a promising therapeutic strategy to reprogram microglial metabolism and promote neural repair.