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Introduction: Traumatic brain injury (TBI) results in widespread impairment of hemostasis, fibrinolysis, coagulation, endothelial function, and immune function. While damage control resuscitation (DCR) is a well-established treatment strategy for life-threatening hemorrhage, alternative treatment strategies should be applied to patients with concurrent TBI. Commonly used resuscitation fluids such as crystalloids or colloids have several disadvantages and may even be harmful when administered in large quantities. In contrast, pharmacologic agents, such as the histone deacetylase inhibitor valproic acid (VPA), have shown promising results in animal studies of TBI and hemorrhagic shock (HS). We previously showed that VPA not only decreases platelet hyper-activation and improves clot dynamics in in-vitro experiments, but also decreases transfusion requirements and improves survival in a porcine DCR model. In those animal models, VPA was administered in conjunction with fluid resuscitation such as fresh frozen plasma (FFP) or hextend (HEX). However, we wondered whether VPA itself induces cytoprotective properties that may underlie the restoration of hemostasis, endothelial function, and immune function that we observed in our models. This meta-analysis used computational biology to identify changes in the brain transcriptome due to VPA treatment that occurred independent of the chosen transfusion fluid. Methods: Swine underwent TBI+HS, kept in shock for 2 hours, and resuscitated with normal saline (control), FFP, FFP+VPA, HEX, or HEX+VPA (n=5/group; all VPA doses 300 mg/kg). After 6 hours of observation, brain RNA was isolated and gene expression was analyzed using a microarray. Gene expression data were normalized to a normal saline control group. Transcriptomic data were imported into iPathwayGuide to identify significantly enriched genes and Gene Ontology (GO) terms. Genes were considered to be differentially expressed if they exhibited a log-fold change (logFC) > 1.0 (fold change > 2) and a p-value < 0.05. The differences in gene expression where then summarized in a Venn-diagram. GO terms identified the Biological Processes with the greatest modulation based on both significance and number of DE genes. GO term P-values were corrected using Elim-pruning. Results: A total of 673 differentially expressed genes were identified. The FFP+VPA group exhibited 206 uniquely expressed genes and the HEX+VPA group 121. We found a total of 113 genes that were expressed in both the FFP+VPA and HEX+VPA groups, but not in the FFP and HEX only groups (Figure). Table 1 summarizes the 10 most up- and down-regulated genes that are only expressed in VPA groups (i.e. FFP+VPA and HEX+VPA). Unregulated genes specifically associated with VPA were involved in promotion of cell division, neurogenesis, cytoskeleton, and ion-channels, while down-regulated genes were involved in metalloproteins, neurodegenerative diseases, and cell cycle arrest. Significantly modulated Biological Processes identified by GO terms include: erythrocyte maturation, macrophage activation, microglial cell proliferation, signal transduction by P53, fibrinolysis and plasminogen activation, fibroblast migration, and neurogenesis. Conclusion: Overall, this meta-analysis suggests that VPA altered the expression of approximately 1/6 th of all genes that were differentially expressed in our cohort. These genes are involved in a variety of biological processes such as cell division, neurogenesis, coagulation, cytoskeleton, and inflammation. These results suggest that VPA treatment may promote an environment that favors the restoration of hemostasis, production of new neurons, removal of damaged cells, and attenuation of inflammation. Such findings suggest that VPA treatment alone may be a promising therapeutic for the treatment of life-threatening hemorrhage and TBI. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Background: Life-threatening hemorrhage and traumatic brain injury (TBI) have a significantly increasing global burden and remain leading causes of preventable deaths. Effective interventions may protect the brain against ongoing damage and improve the long-term outcomes. A growing area of interest is transfusion of cell-based therapies, particularly with bone marrow-derived mesenchymal stem cells (MSC). Transfusion using MSC derived extracellular vesicles (EVs) have shown to improve neurologic outcomes in animal models of life-threatening hemorrhage, stroke, and TBI. However, the precise mechanisms remain poorly characterized. In the present study, we aimed to elucidate some of the key cerebral genes, pathways, and networks that were modulated after transfusion of EVs in a porcine model of hemorrhagic shock (HS) and TBI. Methods: Swine were subjected to HS (40% blood volume) and severe TBI (8-mm cortical impact). After 1 hour of shock, animals were randomized (n=4/group) to treatment with either lactated Ringer's (LR) or LR+EV. Both groups received fluid resuscitation after 2 hours of shock, and autologous packed red blood cells 5 hours later. After 7-days, brains were harvested and RNA-sequencing was performed. The transcriptomic data was imported into the iPathway pipeline for bioinformatics analyses. Results: 5,273 genes were differentially expressed in the LR+EV group vs. LR alone (total 9,588 measured genes, Figure 1). Table 1 lists the top 10 genes exhibiting the greatest up- and down-expression based on fold change. Genes with the greatest up-regulation were involved in synaptic transmission and neuronal development and differentiation, while down-regulated genes were involved in inflammation. Gene Ontology terms experiencing the greatest modulation were involved in inflammation, brain development, and cell adhesion. Pathway analysis revealed significant modulation in the glutamatergic and GABAergic systems. Network analysis revealed down-regulation of inflammation (Figure 2), and up-regulation of neurogenesis, and neuron survival and differentiation. Conclusions: In a porcine model of HS+TBI, EV transfusion was associated with an attenuation of cerebral inflammatory networks and a promotion of neurogenesis and neuroplasticity. These transcriptomic changes could explain the observed neuroprotective and neurorestorative properties associated with EV transfusion. EV transfusion reduces the hyper-inflammatory response and may have great promise in improving outcomes in concurrent life-threatening hemorrhage and severe TBI. Further testing of this novel strategy and its implications in transfusion medicine are warranted. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.