Interaction between endothelial SDC-1 and VWF fibers in vitro. (A) Representative images of empty vector (EV)–transfected HUVECs and cells that overexpress SDC-1 (SDC-1⁺). Magnified regions (white boxes) are shown below. Scale bars, 10 µm. SDC-1 is shown in red, VWF in green, and nuclei in blue. (B) Endothelial SDC-1 promotes the VWF-mediated binding of platelets. HUVECs transfected with an EV control or with an SDC-1 vector (SDC-1⁺) were perfused at a constant shear stress of 6 dyne/cm². VWF release was induced by 50 µM of histamine, and adhering fluorescent platelets were followed by fluorescence microscopy. Where indicated, the endothelial glycocalyx was trimmed by heparinase-I (hep’nase). Scale bar, 100 µm. (C) Quantitative evaluation of the VWF-dependent platelet coverage (n = 11). **P ≤ .01 (1-way analysis and Bonferroni post hoc test).