TSP1 deficiency significantly delays time to form first thrombus in presence of VWF. Using intravital microscopy time to first thrombus (>20 μm) was quantitated after 10% FeCl₃ injury. Dot plot represents the time required to form first thrombus, which was significantly delayed in Tsp1^−/− mice when compared with WT mice and the process was VWF-dependent. N = 10 to 14 mice/group. NS, nonsignificant.