Platelets play an important role in hemostasis. After vessel wall damage, activation of platelets leads to formation of a platelet plug to stop the bleeding, and activation of platelets supports activation of coagulation, inflammation, and wound healing. In the 1940s, it was discovered that platelets support the activation of coagulation because platelet-containing plasma clotted faster than platelet-poor plasma. Because high-speed centrifugation of platelet-poor plasma further prolonged the clotting time, it was also concluded that the platelet-poor plasma contains a factor that promotes clotting. In 1967, Wolf demonstrated that this subcellular factor, which was present in “normal plasma, serum and fractions derived therefrom” consisted of “coagulant material in minute particulate form”. This material was called “platelet dust”, and the ability of platelets and platelet dust to facilitate coagulation became known as platelet factor 3 activity. Platelet dust consists of cell-derived vesicles, nowadays called microparticles (MP), which for a long time were presumed to originate mainly from platelets in the circulation but are now thought to originate also from megakaryocytes.
This chapter provides an overview of current knowledge on platelet microparticles (PMP), with a focus on recent developments with regard to the origin, detection, and functions of PMP in health and disease.