RECOVERY OF ENDOTHELIOPATHY AT 24 HOURS IN AN ESTABLISHED MOUSE MODEL OF HEMORRHAGIC SHOCK AND TRAUMA.

Introduction: The endotheliopathy of trauma develops early after injury and consists of increased vascular permeability, inflammation, and dysfunctional coagulation. Persistence of these abnormalities ultimately leads to multiorgan failure. We hypothesized that extending an established 3-hour acute mouse model of hemorrhagic shock and trauma (HS/T) to a 24-hour survival model would allow for evaluation of persistent endotheliopathy and organ injury after HS/T. Methods: Adult male C57BL/6J mice underwent laparotomy, femoral artery cannulation, and blood withdrawal to induce HS to a MAP of 35 mm Hg for 90 minutes. Mice were resuscitated with either lactated Ringer's (LR) or fresh frozen plasma (FFP). Vascular permeability in the lung and gut was assessed by measuring extravasation of a fluorescent dextran dye. Lungs were evaluated for histopathologic injury, and immunofluorescent staining was used to evaluate intercellular junction integrity. Pulmonary inflammatory gene expression was evaluated using NanoString (Seattle, WA). All endpoints were evaluated at both 3 and 24 hours after initiation of shock. Results: Lactated Ringer's- and FFP-treated mice had an equal mortality rate of 17% in the 24-hour model. Lactated Ringer's-treated mice demonstrated increased vascular permeability in the lung and gut at 3 hours compared with sham mice (lung, P < 0.01; gut, P < 0.001), which was mitigated by FFP treatment (lung, P < 0.05; gut, P < 0.001). Twenty-four hours after shock, however, there were no differences in vascular permeability between groups. Similarly, although at 3 hours, the lungs of LR-treated mice demonstrated significant histopathologic injury, loss of tight and adherens junctions, and a pro-inflammatory gene expression profile at 3 hours, these endpoints in LR mice were similar to sham mice by 24 hours. Conclusions: In an established mouse model of HS/T, endotheliopathy and lung injury are evident at 3 hours but recover by 24 hours. Polytrauma models or larger animal models allowing for more severe injury coupled with supportive care are likely necessary to evaluate endotheliopathy and organ injury outside of the acute period.