Rapid and dose-dependent effect of dasatinib treatment on platelet thrombus formation on collagen under arterial flow conditions in humans and mice. DiOC6-labeled platelets in whole blood from healthy donor or patients 1 to 4 treated with dasatinib 4 hours earlier were perfused through a collagen-coated microcapillary at a shear rate of 1500 seconds for 2 minutes. Thrombus formation was visualized with a 40× long working distance objective in real time and then imaged using transmitted light microscopy. Representative images are shown (A). After a washing step with phosphate-buffered saline for 2 minutes at the same shear rate to remove nonadherent cells, slides were visualized using differential interference contrast microscopy, and representative images are shown (B). Images were visualized using an epifluorescence microscope (Axiovert 200; Carl Zeiss Inc); 40×/1.3 NA oil objective, no solution, with DiOC6. Images were acquired using a charge-coupled device camera (Cool Snap HQ; Roper Scientific) and Metamorph Version 6.21.6 software. Thrombus volume (C) was measured at 2 surface locations in each of the 4 independent experiments performed from healthy donors, dasatinib-treated patients, and imatinib-treated patients (mean ± SEM). **Significant difference (P < .005), according to Student t test. Scale bar represents 20 μm. The same experiments were performed using whole blood from mice treated with 1.25, 2.5, or 5 mg/kg dasatinib (5 mice per group) 4 hours before blood collection, and the thrombus volumes were measured (D). Results shown are representative of 2 independent experiments.
