Traumatic brain injury (TBI) produces a spectrum of pathophysiological and behavioral consequences that severely affect the quality of life of people living with these disorders, family members and caregivers. The successful translation of therapeutic interventions to the clinic to improve neurological outcomes through multicenter TBI trials is yet to be achieved. There is therefore a great need for continued research into novel post-traumatic therapeutic strategies that may target multiple cellular and molecular mechanisms of cell vulnerability, death and repair. We have developed FDA-approved protocols to isolate and grow millions of human Schwann cells (hSC) and have most recently received a compassionate use Investigational New Drug to test hSC-derived exosomes (hSC-Exos) for a neurodegenerative disorder. Based on supportive preliminary data, we propose to conduct a series of critical studies to evaluate the optimal dose and therapeutic window for hSC-Exos treatment on structural, biochemical, and long-term behavioral outcomes using an established model of severe TBI. Our overall hypothesis is that intravenous administration of hSC-Exos after TBI will target multiple secondary injury mechanisms as well as reparative processes leading to improved histopathological and longterm behavioral outcomes. We propose that a major mechanism for this benefit will include anti-inflammatory effects that will promote cytoprotection as well as enhance the opportunity for endogenous reparative processes. We also suggest that this approach can be successfully translated into humans based on the results of this study as our approach of isolating the hSC-Exos has been approved by the FDA. Specific Aim 1 will evaluate the dose- response effects (3 doses) of the hSC-Exos in sham operated and TBI animals. Specific Aim 2 will then evaluate the optimal dose of hSC-Exos on the therapeutic window on behavioral and histopathological outcomes. In Specific Aim 3 we will measure temporal and regional pattens of inflammatory mediators including inflammasome proteins in brain and blood samples after hSC-Exos treatment. To specifically study mechanisms of action, Specific Aim 4 will evaluate the hSC-Exos cargo for the first time using state-of-the-art miRNA sequenceing and informatic approaches. For all studies, we will utilize the penetrating ballistic-like brain injury model in male and female Sprague Dawley rats, clinically relevant outcome measures, biochemical analyses and include strateges to enhance scientific rigor and reproducibility. For the assemment of the hSC-Exos cargo, we will work with an established company to conduct next generation RNA sequencing and mRNA libraries, document the various molecular mechanisms of action and test cause and effect relationships while providing new knowledge to this field of neurotrauma. The results of this proposal will have a significant impact on the field of neurotrauma by investigating a new cell based neuroprotective therap...