Figure 4.

Targeting XPR1 promotes thrombus formation in blood under flow. Citrated human whole-blood preincubated with XVDL (2-200 μg/ml; 4 hours) or PPX (2 mg/ml; 30 minutes) was readjusted to physiological Ca²⁺ and Mg²⁺ concentrations and perfused for 4 minutes over a collagen-coated surface at an arterial (1000 per second) (A) or venous (100 per second) (B) shear rate. Representative phase-contrast images (top) of thrombi formed during perfusion after incubation with the indicated XVDL concentrations. Scale bars, 10 µm. Bar graphs indicate the percentage of surface area covered by thrombi. Mean ± SD; n = 3. Comparisons were performed using 1-way analysis of variance and Tukey’s multiple comparison test; *P < .05, **P < .01. (C-D) Representative bright-field and immunofluorescence images of thrombi formed at t = 4 minutes under arterial (C) or venous (D) flow. Staining for fibrin (59D8; green) and platelets (GPIb; red) and merged images are shown. Scale bars, 10 μm. (E-F) Bright-field and immunofluorescence images of thrombi formed at t = 4 minutes under arterial (E) or venous (F) flow. Representative images of 6 individual experiments. Scale bars, 10 μm. PolyP signal (PPX_Δ12, green) was quantified from 4 randomly selected high-power images by ImageJ. **P < .01, by Student t test. RU, reflectance units.