Role of von Willebrand factor in platelet thrombus formation

Haemostasis is the process that arrests bleeding from wounds, preventing bl ood from flowing outside of the vascular bed. Thrombosis is an abnormal con dition in which the vascular lumen becomes occluded by a mass constituted p rimarily of aggregated platelets and polymerized fibrin. These thrombi impe de the normal flow of circulating blood, becoming the acute cause of diseas es that represent a great health concern in the developed world. Haemostasi s and thrombosis are two aspects of the same function, ie the biological re sponse to vascular injury leading to formation of a thrombus, which is plat elet-rich specifically in the arteries. In either situation, von Willebrand factor is a crucial participant in the process as its main biological acti vity is to support platelet adhesion and aggregation in vessels where rapid blood flow challenges the firm attachment of thrombi to the vascular wall or exposed extravascular tissues. Advances in understanding the structure a nd function of von Willebrand factor indicate that this protein, for its un ique biomechanical properties, may be a potentially useful target of antith rombotic drugs.