Von Willebrand factor, a key protein in the exposure of CD62P on platelets

When a biomaterial is introduced into the body water, electrolytes, and proteins adsorb to the surface. Platelets are then the first cells to interact with the surface adsorbed protein layer. We have studied the role of von Willebrand factor (vWF) for platelet-protein interaction by measuring different platelet responses to protein- and plasma-coated hydrophobic glass surfaces. A high exposure of CD62P on the platelet surface was seen after 10 min of incubation on platelets interacting with vWF and normal plasma-coated surfaces (79 and 67%, respectively). On the surfaces coated with albumin and factor VIII deficient plasma, the exposure was low (11 and 27%, respectively). A higher formation of filipodial extensions on the platelets was seen on the surfaces coated with vWF and normal plasma than on the surfaces coated with albumin or factor VIII deficient plasma. No significant differences were seen between the surfaces regarding the platelet release of PF4, ATP, or phospholipids. As shown by these results, vWF is a specific regulator of the exposure of CD62P by platelets and hence important for the interaction between platelets and later arriving neutrophils at biomaterial surfaces.