Microparticles as a circulating source of procoagulant and fibrinolytic activities in the circulation

Circulating microparticles (MP) are small membrane vesicles derived from a variety of cell types including platelets, erythrocytes, leukocytes, and endothelial cells. They harbor a large repertoire of cell surface receptors, mRNA and biological activities that are related to their involvement in many biological functions. MP subpopulations are well known for their procoagulant activity that relies mainly on the expression of phosphatidylserine and of tissue factor, the major cellular activator of the clotting system. In this review, we will discuss a new vision of MP as complex and ambivalent structures, expressing both activators and inhibitors of coagulation, but also conveying fibrinolytic properties, counteracting their procoagulant activities and identifying MP as integrative systems tuning the hemostatic balance. (C) 2012 Published by Elsevier Ltd.