Assessment of Astrocytic Mitochondrial Transfer to Brain Capillaries After Repeated Mild Traumatic Brain Injury

Traumatic brain injury (TBI) is a significant health issue, with over 80% classified as mild. Repeated mild TBI (rmTBI) exacerbates neurological outcomes through sublethal cellular changes such as mitochondrial dysfunction, oxidative stress, and vascular damage, impairing neuronal function. Our lab found that rmTBI causes acute oxidative damage and mitochondrial dysfunction in brain capillaries, suggesting energy crises within endothelial cells (ECs) and pericytes contribute to prolonged neurovascular dysfunction. Intercellular mitochondrial transfer (IMT) occurs under both pathological and physiological conditions. This proposal aims to understand the IMT response to blood-brain barrier impairment following rmTBI and explore delivering extracellular microvesicles containing mitochondria (mtEV) to enhance neurovascular recovery. Preliminary results reveal mitochondrial impairments in isolated brain capillaries post-oxidative insult and rmTBI. Using astrocyte-specific mitochondrial dendra-2 fluorescent reporter mice (Ast-mtD2), we observed IMT from astrocytes to brain capillaries. In vitro studies suggest potential for delivering cryopreserved mtEV into brain ECs. We hypothesize that capillary dysfunction will decrease IMT from astrocytes to capillaries and mtEV therapy will enhance blood-brain barrier integrity and cognitive outcomes post-rmTBI. Specific Aim 1 assesses astrocytic transfer of mitochondria to brain ECs under oxidative stress. Specific Aim 2 evaluates IMT following rmTBI and the efficacy of mtEV supplementation in brain capillary mitochondrial uptake and therapeutic efficacy on vascular function and neurobehavioral outcomes. Overall, this proposal will increase our understanding of mitochondrial transfer and uptake by brain capillaries following rmTBI.