Role of VASP in the regulation of platelet adhesion under pathophysiologic conditions. (A) Platelet–vessel wall interactions were assessed prior to and following intestinal ischemia-reperfusion (I/R) as described in “Materials and methods.” Fluorescent wild-type or VASP^–/– platelets were transfused into recipient mice of either genotype. Segmental jejunal ischemia (60 minutes) was induced with subsequent reperfusion. Platelet–endothelial cell interactions in intestinal arterioles and venules were analyzed by intravital videofluorescence microscopy prior to (baseline) and following I/R in arterioles (left) and venules (right).^6,35  Mean ± SEM; * indicates significant difference compared with wild type; P < .05. (B) The microphotographs show representative in vivo fluorescence microscopy images of platelet adhesion prior to (top) and following intestinal I/R (bottom) in control animals (left) or VASP^–/– mice (right). Arrowheads indicate adherent platelets. Bars represent 50 μm. (C) To evaluate the role of VASP in the regulation of platelet adhesion to the atherosclerotic vascular wall, wild-type or VASP^–/– platelets were infused intravenously into ApoE^–/– mice. Platelet adhesion was visualized in the right common carotid artery in situ by in vivo video microscopy as described above. Mean ± SEM; * indicates significant difference compared with wild-type platelets; P < .05.