Lack of in vivo function of CD31 in vascular thrombosis

A murine model of endothelial cell injury-based vascular thrombosis was use d to test the role of platelet-endothelial cell adhesion molecule-1 (PECAM- 1, CD31) in blood cell aggregate formation and vessel occlusion in vivo. Ph otochemically-induced thrombus formation was analyzed in detail using intra vital fluorescence microscopy of individual microvessels in cremaster muscl e preparations of CD31-deficient and wildtype mice. In venules, epi-illumin ation induced rapid thrombus formation with first platelet deposition after 0.56 +/- 0.11min and complete vessel occlusion within 5.05 +/- 0.45 min. I n arterioles, thrombus formation was markedly delayed with first platelet d eposition after 3.03 +/- 0.47 min and complete vessel occlusion within 10.0 4 +/- 1.26 min. Kinetics of thrombus formation in both venules (first plate let deposition: 0.52 +/- 0.1 min; vessel occlusion: 5.03 +/- 0.52 min) and arterioles (first platelet deposition: 3.06 +/- 0.68 min; vessel occlusion: 10.02 +/- 1.38 min) of CD31-deficient mice was found almost identical comp ared with that in wildtype animals. Tail bleeding time was 233 +/- 24 s in wildtype and 243 +/- 32 s in CD31-deficient mice. Moreover, CD31-deficient and wildtype mice revealed comparable interaction of leukocytes to endothel ium. This study shows for the first time in vivo that CD31 is not criticall y involved in blood cell thrombus formation upon endothelial cell injury.