HDL reduces VWF string assembly on the endothelial surface. Human umbilical vein endothelial cells (HUVECs) cultured in parallel-plate flow chambers were stimulated with 50 ng/mL phorbol myristate acetate (PMA) for 20 minutes at 37°C under static conditions, with or without HDL (2 mg/mL). Two mL of formaldehyde-fixed platelets (7 × 104 platelets per μL) were then perfused over the stimulated cells at a shear stress of 10 to 20 dynes/cm2 with or without HDL (200 μg/mL). The cells were then washed and fixed with paraformaldehyde. The platelet-decorated VWF strings in 10 random, nonoverlapping bright-field images for each condition were counted and measured. HUVECs were stimulated with PMA and perfused with fixed platelets (A) in the absence of HDL, (B) in the presence of HDL during stimulation but not perfusion, (C) in the presence of HDL during perfusion but not during stimulation, and (D) with HDL present during both stimulation and perfusion. (E) Quantification of VWF string units on the endothelial surface (n = 3 to 6). P value (<.001) is from Welch’s t test with Bonferroni correction for the comparison of means for no HDL vs HDL during stimulation and perfusion. Platelet-decorated VWF strings are indicated by arrows in (A) and (D). Scale bar, 50 μm (A-D).
