Mouthon, M-A., Vereycken-Holler, V., Van der Meeren, A. and Gaugler, M-H. Irradiation Increases the Interactions of Platelets with the Endothelium In Vivo: Analysis by Intravital Microscopy. Radiat. Res. 160, 593–599 (2003).

Adhesion of platelets to the endothelium is believed to be a major factor contributing to thrombosis and vascular occlusion after radiotherapy or endovascular irradiation. In the present study, platelet–endothelium interactions were analyzed in vivo by intravital microscopy in mesenteric venules of mice according to three parameters: (1) platelet rolling, (2) platelet adhesion, and (3) the presence of platelet clusters. A 10-Gy total-body irradiation of mice resulted in an increase in the frequency of appearance of these three types of platelet–endothelium interactions in postcapillary venules 6 and 24 h after exposure, whereas only minor alterations were seen in large venules. In addition, the duration of platelet adhesion was increased 24 h after irradiation in both postcapillary and large venules. However, P-selectin was not up-regulated on the platelet membrane and platelet-leukocytes were not seen rolling together, suggesting that changes in platelet–endothelial cell interaction result from endothelial cell activation rather than platelet activation. Our data suggest that irradiation transforms resting endothelial cells to a pro-adhesive surface for platelets, which could ultimately lead to thrombosis.