A PTM Regulatory Enzyme Co expression Code Defines Microglial Functional Heterogeneity in Cerebral Ischemia Reperfusion Injury

BackgroundCerebral ischemia-reperfusion injury (CIRI) is a major determinant of poor outcome after recanalization therapy in acute ischemic stroke. Microglial functional heterogeneity underpins neuroinflammation, yet the molecular mechanisms governing microglial phenotypic transitions remain incompletely understood. Metabolite-driven post-translational modifications (PTMs) have emerged as key regulators of microglial metabolism and inflammation, but whether PTM regulatory enzymes form co-expression modules that define microglial states is unknown. MethodsWe analyzed single-cell RNA-seq datasets from five GEO studies (GSE174574, GSE227651, GSE245386, GSE267240, GSE319237) covering tMCAO reperfusion and permanent ischemia models. Microglia were purified using double filtration (P2ry12/Tmem119/Cx3cr1+, Cd68/Adgre1/Ly6c-). PTM enzyme co-expression modules were identified by non-negative matrix factorization (NMF). Spatiotemporal dynamics were assessed by module projection across timepoints (Sham, 1d, 3d, 7d) and pseudotime analysis. Independent validation was performed in an additional tMCAO dataset (GSE245386). Sex differences were explored in a mixed-sex permanent ischemia dataset (GSE267240). ResultsThree robust PTM enzyme co-expression modules were identified: Metabolic stress-associated (M1), Pro-inflammatory-associated (M2), and Reparative-associated (M3). M1 was enriched in TCA cycle enzymes, M2 in inflammatory pathways (leukocyte activation, chemotaxis), and M3 in vascular development and translation. Module proportions and scores showed dynamic transitions: M1 decreased after reperfusion, M2 peaked at day 1-3, and M3 slightly increased at day 7. Independent validation in GSE245386 yielded high module conservation (cosine similarity = 0.874). Sex-specific differences in module distribution were observed in permanent ischemia ({chi}2 = 14.98, p = 0.00056). ConclusionsPTM enzyme co-expression modules delineate metabolic, pro-inflammatory, and reparative microglial states in CIRI with distinct spatiotemporal dynamics. This transcriptional framework supports the "PTM enzyme code" hypothesis and provides stage-specific targets for stroke therapy.