YTHDF2 Contributes to Postoperative Cognitive Dysfunction Following Femoral Fracture

Postoperative cognitive dysfunction (POCD) is a prevalent neurological complication in older patients undergoing orthopedic surgery. N⁶-methyladenine (m⁶A) modification regulates central nervous system development and neuroinflammation. However, its specific role in POCD remains poorly understood. This study integrated the POCD-related datasets GSE178995 and GSE215410 to identify m⁶A-associated differentially expressed genes (DEGs). We further investigated the roles of YTHDF2 and its downstream targets in POCD using an LPS-induced microglial inflammation model and a femoral fracture-induced POCD mouse model, combined with a siRNA- and AAV9-mediated knockdown approaches. We identified 147 overlapping DEGs across the two datasets, including the m⁶A-related enzymes YTHDF2 and METTL3. In vitro, LPS stimulation upregulated global m⁶A levels and Ythdf2 expression in BV2 cells and promoted the release of TNF-α, IL-6, and IL-1β. Ythdf2 knockdown attenuated microglial inflammatory activation. Mechanistically, YTHDF2 bound m⁶A-modified Trem2 mRNA. In actinomycin D chase assays, Ythdf2 knockdown prolonged Trem2 mRNA half-life. This was accompanied by higher AMPK/SIRT1 pathway and reduced NF-κB signaling. In vivo, systemic AAV9-mediated Ythdf2 knockdown, which is not microglia-specific, was associated with improved spatial learning and memory in the POCD model and reduced hippocampal neuronal atrophy. This treatment also increased the expression of Map2, Psd95, and TREM2, and enhanced the AMPK/SIRT1 pathway. In conclusion, YTHDF2 acts as an m⁶A reader that exacerbates microglial neuroinflammation, and systemic Ythdf2 reduction is associated with cognitive improvement in POCD following femoral fracture. This effect is associated with YTHDF2-mediated decay of m⁶A-modified Trem2 mRNA and with downstream AMPK/SIRT1 signaling. Targeting the YTHDF2-TREM2-AMPK/SIRT1 axis may represent a potential therapeutic strategy for POCD.