PECAM1 and acute respiratory distress syndrome: We also stained vascular endothelial cells for the vascular marker CD31 and found numerous vascular endothelial cells in the TAG + ARDS group compared with the ARDS (ARDS, 10.76 ± 1.96 vs. TAG + ARDS, 16.88 ± 2.01, p < 0.01; Figures 5C, D).