Role of von Willebrand factor in platelet thrombus formation.

Haemostasis is the process that arrests bleeding from wounds, preventing blood from flowing outside of the vascular bed. Thrombosis is an abnormal condition in which the vascular lumen becomes occluded by a mass constituted primarily of aggregated platelets and polymerized fibrin. These thrombi impede the normal flow of circulating blood, becoming the acute cause of diseases that represent a great health concern in the developed world. Haemostasis and thrombosis are two aspects of the same function, ie the biological response to vascular injury leading to formation of a thrombus, which is platelet-rich specifically in the arteries. In either situation, von Willebrand factor is a crucial participant in the process as its main biological activity 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 and function of von Willebrand factor indicate that this protein, for its unique biomechanical properties, may be a potentially useful target of antithrombotic drugs.