Persistent histone H3K27 acetylation contributes to excessive scar formation after spinal cord injury through the regulation of microglial cholesterol accumulation.

Scar formation is a critical determinant of neurological recovery following spinal cord injury (SCI) because scars act as a physical support and barrier that influences axonal regeneration and remyelination. However, the regulatory mechanisms governing scar formation remain incompletely understood. Integrated multiomics analysis of publicly available single-cell RNA-seq and ATAC-seq data (GSE230765) from adult mice during the subacute/chronic phases of SCI revealed epigenetic mechanisms underlying microglial activation. Cell communication analysis revealed a connection between persistent microglial activation and excessive scar formation after SCI. Pharmacological inhibition of histone acetylation using L002 was employed to validate the H3K27ac-mediated regulation of the microglial phenotype, scar formation, and functional recovery. Persistent microglial activation post-SCI resulted in characteristic cholesterol metabolic reprogramming, with intracellular cholesterol accumulation correlated with sustained microglial activation. Single-cell ATAC-seq revealed chromatin accessibility-mediated epigenetic control of cholesterol metabolism gene expression, identifying H3K27ac as a pivotal regulator. L002-mediated H3K27ac inhibition attenuated cholesterol accumulation, mitigated neuroinflammation, and reduced scar formation through the disruption of microglia-astrocyte-fibroblast communication. Mechanistically, SPP1 secretion from activated microglia drove excessive scar formation, and inhibition of H3K27ac reduced the level of SPP1. Our study suggests that H3K27ac mediates the epigenetic regulation of myeloid cell activation in SCI pathogenesis. Targeted modulation of this histone modification site attenuates chronic microglial activation and subsequent scar formation, suggesting an innovative therapeutic strategy for neural repair. These findings establish chromatin remodeling as a promising target for improving functional recovery post-SCI.