Microglial P2Y12 Receptor Signaling Governs Epilepsy-Associated Neurogenesis via Bidirectional Regulation of Distinct Microglial Subpopulations

Following epileptogenesis, a pronounced escalation in microglial activation, neuronal dysfunction, and hippocampal neurogenesis is consistently observed. As principal immune sentinels of the central nervous system, microglia perform multifaceted functions including inflammatory mediator secretion, neurotrophic factor synthesis, synaptic material phagocytosis, and homeostatic regulation. Within the epileptic milieu, microglia exhibit dichotomous regulatory effects, paradoxically influencing both neurodegenerative processes and neurogenesis processes. Despite this critical dual functionality, the mechanistic underpinnings of microglial polarization in epileptogenesis remain incompletely characterized. To address this knowledge gap, we implemented an integrative multi-omics approach combining single-cell RNA sequencing (scRNA-seq) and bulk RNA sequencing (bulk RNA-seq) to delineate distinct epilepsy-associated microglial (EPAM) subpopulations. Complementary conditional knockout murine models were employed to elucidate the molecular determinants of EPAM differentiation. Our analytical pipeline identified two microglial subsets demonstrating reciprocal abundance patterns at 7 days post-epilepsy induction: a diminished P2ry12 ^high CD74 ^low H2-Ab1 ^low population and an expanded P2ry12 ^low CD74 ^high H2-Ab1 ^high subpopulation, temporally correlated with hippocampal neurogenesis onset. Genetic ablation of P2ry12 precipitated a paradoxical expansion of both subpopulations following epileptogenic challenge, concomitant with significant suppression of neurogenesis. Mechanistic investigations revealed that P2ry12 deficiency upregulated CD74 and H2-Ab1 expression within microglia, enhanced hippocampal TNF-α release, and disrupted neurogenesis processes. These findings collectively demonstrate that P2Y12 receptor-mediated signaling governs the dynamic equilibrium of EPAM subpopulations, with perturbation of this regulatory axis impairing compensatory neurogenesis during epileptogenesis.