127 Plasma from Patients with Burn Injury Increases Endothelial Permeability In-Vitro

Introduction The contribution of endothelial injury to the pathogenesis of burn shock is not well characterized. Human umbilical endothelial cells (HUVECs) have been used to study endotheliopathy in myriad shock states. This work investigates the impact of burn patient plasma on the vascular endothelium and its barrier function. Methods HUVECs were seeded into the apical chambers of transwell plates and cultured over 5–7 days to a confluent monolayer which was confirmed by a transendothelial electrical resistance (TEER) of ≥30Ω. After IRB approval, plasma was collected from burn-injured patients 4 hours after admission. Demographic and injury characteristics were collected from the medical record. Plasma Syndecan-1 (SDC-1) was quantified by ELISA. HUVEC monolayers were exposed to 10% multi-donor pooled healthy human plasma (HHP) or burn patient plasma. Monolayers were subsequently incubated with FIT-C Dextran (40,000 kD). FIT-C diffusion through monolayers was measured in basal chamber supernatants. Monolayer permeability was measured with indices calculated by normalizing values to blank (transwell inserts) and HHP-treated monolayer FIT-C diffusion. HUVECs were also cultured on glass slides and exposed to HHP or burn patient plasma. Cells were fixed with 4% Paraformaldehyde and F-Actin was stained with Texas Red-Phalloidin. Intercellular gap area was calculated using imaging software. Differences between treatment conditions were analyzed with Welch’s t-test and one-way ANOVA, simple linear regression was used to characterize the relationship between plasma SDC-1 and permeability indices, significance was set at p < 0.05. Results Eight burn patient plasma samples were tested. Patients were mostly male (75%) with a mean age of 50±20 years and mean %TBSA burn of 37±34%. Five burn plasma samples significantly increased monolayer permeability. There were no significant differences between patient samples that increased permeability in age, TBSA, gender, or in-hospital mortality. Monolayer permeability indices increased between 7–15% (p< 0.05) among burn plasma treatment conditions (n=6) that increased permeability. There was a strong relationship between monolayer permeability index (%) and plasma SDC-1 (µg/mL) (p=0.03, R2=0.93). Morphological F-actin rearrangement was apparent on microscopy and intercellular gap area was increased in burn plasma treatment conditions (12% vs. 49%, p≤0.0007, n=6). Conclusions Plasma from burn patients induces endothelial damage that increases endothelial cell monolayer permeability. The endothelial biomarker SDC-1 is a reliable indicator of endothelial damage. F-actin rearrangement and an increase in intercellular gap area likely contributes to burn endotheliopathy.