Stimulated aggregation of murine platelets by plasma from wild-type or VWF^–/– mice. Platelet aggregation was assessed by mixing platelet-rich plasma (PRP), test plasma, and botrocetin. Photographs were taken after 2 hours; 23°C with gentle rocking. (A) Naïve WT. PRP from VWF wild-type mice, mixed with plasma from VWF wild-type mice containing natural endogenous VWF (positive control) showing aggregation. (B) Naive, VWF^–/–. PRP from VWF^–/– mice mixed with plasma from naive VWF^–/– mice and botrocetin (negative control), illustrating the absence of functional VWF from the plasma of VWF^–/– mice. (C) VWF^–/–, control plasmid. PRP from VWF^–/– mice mixed with plasma from VWF^–/– mice that had received 100 μg irrelevant cDNA (negative control) showing no aggregation. (D) VWF^–/–, VWF plasmid, 100 μg. PRP from VWF^–/– mice mixed with plasma from VWF^–/– mice that had received 100 μg VWF cDNA shows botrocetin-stimulated aggregation of platelets indicating the presence of functional gene transfer–derived VWF. (E) VWF^–/–, VWF plasmid, 250 μg. PRP from VWF^–/– mice mixed with plasma from VWF^–/– mice that had received 250 μg VWF cDNA shows increased botrocetin-stimulated aggregation of platelets, indicating the presence of functional gene transfer–derived VWF.