VWF deficiency abrogates the ADAMTS13-deficient prothrombotic state. (A) Quantification of thrombi formation in FeCl₃-injured arterioles. In VWF-expressing Adamts13^−/− mice, thrombi larger than 20 μm were observed at 5.7 (± 0.5) minutes (column 1), compared with 7.9 (± 0.4) minutes for Adamts13^+/+ mice (P < .05, column 2). In contrast, there was no difference in mean time to first thrombus formation larger than 20 μm between mice deficient for both VWF and ADAMTS13 (10.7 ± 0.4 minutes, column 3), compared with VWF-deficient mice expressing ADAMTS13 (10.6 ± 0.7 minutes, column 4). (B) Occlusion time of FeCl₃-injured arterioles. VWF-expressing Adamts13^−/− mice demonstrated an average occlusion time of 10.8 (± 1.0) minutes (column 1), compared with 14.6 (± 1.3) minutes for Adamts13^+/+ mice (P < .05, column 2). In contrast, there was no difference in occlusion time between mice deficient for both VWF and ADAMTS13 (column 3), compared with VWF-deficient mice expressing ADAMTS13 (column 4). Most of the injured arterioles did not occlude in mice of either of these 2 groups. The bars represent the mean of each group.