TBI drives astrocytic mitochondrial transfer associated with neuronal mitochondrial dysfunction: therapeutic potential of astrocytic EV-mito

Mitochondria are dynamic organelles essential for neuronal survival and synaptic function, and their dysfunction is a key consequence of excitotoxicity following traumatic brain injury (TBI). While intercellular mitochondrial transfer and exogenous mitochondrial transplantation have emerged as mechanisms to restore cellular bioenergetics, its in vivo relevance in the central nervous system remains incompletely understood. Here, we used astrocyte and neuron-specific mitochondrial reporters (GFP or Dendra2) in mice to assess cell-type-specific mitochondrial morphology, bioenergetics, and transfer 24 h after TBI. Neurons exhibited marked mitochondrial dysfunction, including altered morphology and reduced bioenergetic capacity across somatic, synaptic, and non-neuronal fractions. In contrast, astrocytic mitochondria showed morphological changes but preserved bioenergetic function. Concomitantly, astrocyte-to-neuron mitochondrial transfer was significantly increased following injury, although transfer to synapses remained limited. Single-cell RNA sequencing of astrocytes revealed upregulation of genes involved in extracellular vesicle (EV) biogenesis and mitochondrial translation following injury compared to controls. In vitro co-culture studies confirmed that astrocytes transfer mitochondria to neurons via EVs containing mitochondria (EV-mito). Isolated EV-mito from astrocyte-conditioned media improves neuronal mitochondrial function under NMDA (N-methyl-D-aspartate) induced excitotoxic conditions. Together, these findings demonstrate that TBI drives astrocyte-mediated mitochondrial transfer as an adaptive response, occurring alongside neuronal mitochondrial dysfunction. This process preserves neuronal bioenergetics in the soma and neurites but not at synapses, highlighting both its therapeutic potential and spatial limitations.