Early and persistent thalamic astrocytic reactivity is a hallmark of post-traumatic epilepsy in mice

Post-traumatic epilepsy (PTE) is a debilitating outcome of traumatic brain injury (TBI), but treatment remains elusive due to a limited understanding of its pathophysiology and the lack of reliable biomarkers. Reactive astrogliosis is a hallmark of both TBI and acquired epilepsies, yet its role in PTE is understudied. Here, we used a murine TBI model with 50% PTE incidence by 5 months (m) and a latency of 1.5m before onset to investigate astrocytic alterations. We showed that once pathology is established, reactive, dysmorphic and dysfunctional astrocytes are a pathological hallmark of PTE, with the ipsilateral thalamus emerging as a key hub for the observed changes. To disentangle astrocytic alterations caused by ongoing seizures from epileptogenic ones, we identified an acute biomarker capable of predicting mice at high or low risk of PTE based on acute contralateral spiking activity. Leveraging this, we characterized astrocytic responses before seizure onset and observed increased GFAP aggregation and astrocytic morphological alterations in the ipsilateral thalamus of high-risk mice, indicating that astrocytic dysfunction may contribute to epileptogenesis. Single nuclei RNA-seq analyses further revealed acute astrocytic transcriptomic alterations in the thalamus of high-risk mice, shedding light on potential biological processes contributing to epileptogenesis, including BBB breakdown and neuroinflammation. Finally, we tested an immunotherapeutic intervention targeting GFAP, by promoting its clearance via opsonization, in improving TBI outcomes. Treatment improved sensorimotor performance and prevented weight loss after TBI, together with a modulation of the thalamic astrocytic neuroinflammatory microenvironment, suggesting that the acute removal of monomeric or aggregated GFAP prevents an exacerbation of neuroinflammatory processes, with potential relevance to PTE. Overall, our findings identify astrocytic reactivity in the thalamus as a central feature of PTE and demonstrate that acute astrocytic changes occur prior to seizure onset, highlighting thalamic astrocytes as promising therapeutic targets for prevention or mitigation of PTE.