TRAUMA-DERIVED EXTRACELLULAR VESICLES ARE SUFFICIENT TO INDUCE ENDOTHELIAL DYSFUNCTION AND COAGULOPATHY

Although a number of studies have demonstrated increased release of extracellular vesicles (EVs) and changes in their origin differentials after trauma, the biologic significance of EVs is not well understood. We hypothesized that EVs released after trauma/hemorrhagic shock (HS) contribute to endotheliopathy and coagulopathy. To test this hypothesis, adoptive transfer experiments were performed to determine whether EVs derived from severely injured patients in shock were sufficient to induce endothelial dysfunction and coagulopathy. Methods: Total EVs were enriched from plasma of severely injured trauma/HS patients or minimally injured patients by ultracentrifugation and characterized for size and numbers. Under isoflurane anesthesia, noninjured naive C57BL/6J mice were administered EVs at varying concentrations and compared with mice receiving equal volume vehicle (phosphate-buffered saline (PBS)) or to mice receiving EVs from minimally injured patients. Thirty minutes after injection, mice were sacrificed, and blood was collected for thrombin generation (thrombin-antithrombin, thrombin-antithrombin complex [TAT] assay) and syndecan-1 by enzyme-linked immunoabsorbent assay (ELISA). Lungs were harvested for examination of histopathologic injury and costained with von Willebrand factor and fibrin to identify intravascular coagulation. Bronchial alveolar lavage fluid was aspirated from lungs for protein measurement as an indicator of the endothelial permeability. Data are presented as mean ± SD, P < 0.05 was considered significant, and t test was used. Results: An initial proof-of-concept experiment was performed in naive mice receiving EVs purified from severely injured trauma/HS patients (Injury Severity Score [ISS], 34 ± 7) at different concentrations (5 × 106 to 3.1 × 109/100 μL/mouse) and compared with PBS (control) mice. Neither TAT nor syndecan-1 levels were significantly different between groups at 30 minutes after EV infusion. However, lung vascular permeability and histopathologic injury were significantly higher in the EV group, and lung tissues demonstrated intravascular fibrin deposition. Based on these data, EVs from severely injured trauma/HS patients (ISS, 32 ± 6) or EVs from minimally injured patients (ISS, 8 ± 3) were administered to naive mice at higher concentrations (1 × 109 to 1 × 1010 EV/100 μL/mouse). Compared with mice receiving EVs from minimally injured patients, plasma TAT and syndecan-1 levels were significantly higher in the trauma/HS EV group. Similarly, bronchial alveolar lavage protein and lung histopathologic injury were higher in the trauma/HS EV group, and lung tissues demonstrated enhanced intravascular fibrin deposition. Conclusion: These data demonstrate that trauma/HS results in the systemic release of EVs, which are capable of inducing endotheliopathy as demonstrated by elevated syndecan-1 and increased permeability and coagulopathy as demonstrated by increased TAT and intravascular fibrin deposition. Targeting trauma-induced EVs may represent a novel therapeutic strategy.