TSP1 deficiency in mice prolongs mean time to complete occlusion in injured arteriole. Dot plot represents the time required for complete occlusion, which was quantitated as time required for blood to stop flowing for 30 seconds in arterioles injured with 10% FeCl₃. The mean time to complete occlusion was significantly prolonged in Tsp1^−/− mice when compared with WT (P < .05). None of the injured vessels occluded in Tsp1^−/−/Vwf^−/− and Tsp1^+/+/Vwf^−/−. The mean time to complete occlusion was significantly prolonged in Tsp1^−/−/Vwf^+/− when compared with Tsp1^+/+/Vwf^+/−, suggesting a threshold of VWF is required for TSP1 to modulate arterial thrombosis. Data represent mean ± standard error of the mean. N = 10 to 13 mice/group. NS, nonsignificant.