The TGFB1-Wnt/β-catenin axis programs a neuroprotective IGF1+ microglial state during epileptogenesis.

Temporal lobe epilepsy (TLE) remains a major clinical challenge, with over one-third of patients resistant to existing medications. Microglia, the brain's resident immune cells, are highly plastic, yet their potential to adopt a protective state in epilepsy is unclear. Using time-resolved single-nucleus RNA sequencing (snRNA-seq) in a kainic acid (KA)-induced seizure model, we identified an early-emerging microglial subpopulation transcriptionally distinct from homeostatic microglia. This subpopulation was characterized by high expression of insulin-like growth factor 1 (Igf1), along with Myo1e and Apbb2. Through in vitro co-culture assays, we demonstrated that TGFB1 stimulation, but not LPS, drives the generation of this IGF1+ phenotype. These induced IGF1+ microglia significantly suppressed the secretion of pro-inflammatory cytokines under inflammatory conditions. Importantly, conditioned medium from IGF1+ microglia enhanced the proliferation and survival of KA-exposed HT22 neuronal-like cells. Mechanistically, we found that TGFB1 activates the Wnt/β-catenin pathway, promoting the nuclear translocation of β-catenin, which in turn upregulates IGF1 expression. In vitro, we abolished the TGFB1-induced neuroprotective phenotype by knocking down β-catenin using siRNA; however, exogenous supplementation with IGF1 partially rescued this effect. Our findings define a TGFB1-β-catenin-IGF1 axis that drives microglia into a neuroprotective state, revealing a novel endogenous mechanism and therapeutic direction for epilepsy.