Early treatment with exosomes following traumatic brain injury and hemorrhagic shock in a swine model promotes transcriptional changes associated with neuroprotection

BACKGROUND We have shown that administration of mesenchymal stem cell-derived exosomes (single dose given within 1 hour) in models of traumatic brain injury (TBI) and hemorrhagic shock is neuroprotective. The precise mechanisms responsible for the neuroprotection are not fully understood. This study was designed to investigate the transcriptomic changes in the brain that are associated with this treatment strategy. METHODS Yorkshire swine (40-45 kg) were subjected to a severe TBI (12-mm cortical impact) and hemorrhagic shock (40% estimated total blood volume). One hour into shock, animals were randomized (n = 5/cohort) to receive either lactated Ringer's (LR; 5 mL) or exosomes suspended in LR (LR + EXO; 1 x 10(13)exosome particles in 5 mL LR). Animals then underwent additional shock (1 hour) followed by normal saline resuscitation. After 6 hours of observation, brain swelling (% increase compared with the uninjured side) and lesion size (mm(3)) were assessed. Periinjured brain tissue was processed for RNA sequencing, analyzed with high through-put RNA sequencing data analysis, and results compared between control and experimental groups. RESULTS Exosome treatment significantly increased (p< 0.005) gene expression associated with neurogenesis, neuronal development, synaptogenesis, and neuroplasticity. It also significantly reduced (p< 0.005) genes associated with stroke, neuroinflammation, neuroepithelial cell proliferation, and nonneuronal cell proliferation contributing to reactive gliosis. Exosome treatment also significantly increased (p< 0.005) the genes that are associated with stability of blood-brain barrier. CONCLUSIONS Administration of a single dose of exosomes induces transcriptomic changes suggestive of neuroprotection. Their use as a treatment for TBI is promising and requires further investigation for human translation.