BACKGROUND Administration of human mesenchymal stem cell (MSC)–derived exosomes can enhance neurorestoration in models of traumatic brain injury (TBI) and hemorrhagic shock (HS). The impact of early treatment with MSC-derived exosomes on brain injury in a large animal model remains unknown. We sought to evaluate the impact of early single-dose exosome treatment on brain swelling and lesion size, blood-based cerebral biomarkers, and blood-brain barrier (BBB) integrity. METHODS Female Yorkshire swine were subjected to a severe TBI (12-mm cortical impact) and HS (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 LR + exosomes (1 × 1012 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 (mm3) were assessed. Cerebral hemodynamics and blood-based biomarkers of brain injury were compared. Immunofluorescence and RNA sequencing with differential gene expression and pathway analysis were used to assess the integrity of the perilesion BBB. RESULTS Exosome-treated animals had significantly less (p < 0.05) brain swelling and smaller lesion size. They also had significantly decreased (p < 0.05) intracranial pressures and increased cerebral perfusion pressures. Exosome-treated animals had significantly decreased (p < 0.05) albumin extravasation and significantly higher (p < 0.05) laminin, claudin-5, and zonula occludens 1 levels. Differential gene expression and pathway analysis confirmed these findings. Serum glial fibrillary acidic protein levels were also significantly lower (p < 0.05) in the exosome-treated cohort at the end of the experiment. CONCLUSION In a large animal model of TBI and HS, early treatment with a single dose of MSC-derived exosomes significantly attenuates brain swelling and lesion size, decreases levels of blood-based cerebral biomarkers, and improves BBB integrity.

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 × 1013 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 (mm3) 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.