Blockade of platelet endothelial cell adhesion molecule-1 (PECAM-1) protects against ischemia-reperfusion injury in muscle flaps at microcirculatory level

Several lines of evidence show that platelet endothelial cell adhesion mole cule-1 (PECAM-1), a component of endothelial cell junctions, is required fo r leukocyte transmigration through endothelial cell monolayers. Polymorphon uclear leukocytes play an important role in ischemia-reperfusion injury. We sought to determine whether administering an anti-PECAM-1 antibody would p revent or attenuate ischemia-reperfusion injury in a rat cremaster muscle f lap injury model. Eighteen male Sprague-Dawley rats were divided into three groups. Group I ( control): Cremaster muscle island flaps were dissected for baseline measure ments of eight indicators: numbers of rolling, sticking, and transmigrating neutrophils, numbers of rolling and sticking lymphocytes, number of perfus ed capillaries, endothelial edema, and vessel permeability. Group II: The p repared cremas ter flap was subjected to 4 hours of ischemia and 24 hours o f reperfusion. Group III: The muscle flap was subjected to ischemia and rep erfusion as in group II, and anti-PECAM-1 antibodies (1 mg/kg) were injecte d subcutaneously 15 minutes before reperfusion. Blood vessels were observed in vivo under an intravital microscopy system. Microvascular permeability was made visible with injected fluorescein isothiocyanate-labeled albumin a nd evaluated with Kontron Elektronik computer software. The ischemia-reperfusion-alone group (group II) presented a 225-percent inc rease in the activation of sticking leukocytes (2.4 +/- 0.4 to 7.8 +/- 0.8, p < 0.05) (p < 0.01); This leukocyte activation was reduced by 83 percent following anti-PECAM-1 monoclonal antibody treatment (1.3 +/- 0.5 per 100 m u m) (p < 0.01). At 24 hours, endothelial injury in group II was confirmed by a 4-fold increase in the number of transmigrating leukocytes into the in terstitial space (7.6 +/- 1.2 per field versus 1.9 +/- 0.4 per field in con trols). This phenomenon was reduced by 85 percent following anti-PECAM-1 mo noclonal antibody treatment (1.1 +/- 0.2 per field) (p < 0.01). Analysis sh owed that the number of flowing capillaries was 67 percent lower in group I I (6.8 +/- 0.3 to 2.2 +/- 0.7, p < 0.01). Anti-PECAM-1 antibody treatment c aused a 2.5-fold increase in this number (5.6 +/- 0.5, p < 0.01). Microcirc ulatory permeability index showed a 180-percent increase in group II (p < 0 .05) when compared with baseline values. This increased albumin leakage was effectively attenuated by antibody treatment (p < 0.05). Blocking the action of PECAM-1 in vivo by administering monoclonal antibodi es significantly attenuated ischemia-reperfusion injury, presumably by inhi biting transendothelial migration of neutrophils and by increasing capillar y perfusion at a muscle flap microcirculatory level.