cVWF formation under flow. (A-C) Washed platelets were perfused over histamine-stimulated HUVECs. After being stable for 10 minutes, HUVEC-bound platelet-covered VWF strings were exposed to plasmin (50 μg/mL) or vehicle control under flow. Samples were collected into PPACK and analyzed by ELISA for VWF antigen levels, cVWF levels, and fraction of VWF in a plasmin-cleaved state. Data represent 5 independently executed experiments, and are shown as means ± SD.