RhoA−/− platelets display increased rolling velocity on VWF ex vivo and form only instable thrombi after FeCl3 injury in vivo. (A-B) Unaltered adhesion but accelerated rolling of RhoA−/− platelets on VWF ex vivo. Heparinized whole blood was perfused over immobilized murine VWF at a shear rate of 7700 seconds−1. (A) Mean distance per minute ± SD (left) and mean number of adherent platelets per 2500 μm2 ± SD (right) are shown (n = 6; *P < .05). (B) Representative phase contrast images after 1 minute of washing with Tyrode HEPES buffer are illustrated. Scale bar represents 50 μm. (C-D) RhoA−/− mice display instable thrombus formation after FeCl3-induced vascular injury. Small mesenteric arterioles were injured by topical application of FeCl3, and thrombus formation of fluorescently labeled platelets was monitored using intravital microscopy. (C) Time to stable vessel occlusion (left) and amount of stably occluded (1), recanalized (2), and nonoccluded vessels (3) after injury of wt and RhoA−/− mice (right) are shown. Each symbol represents 1 arteriole. (D) Representative pictures at the indicated time. Scale bar represents 100 μm. Asterisk indicates stable occlusion of the vessel.
