The diversity of platelet microparticles.

Abstract

Platelet microparticles are small extracellular vesicles abundant in blood. The present review will introduce the mechanisms underlying the generation of microparticles, and will describe the diverse microparticle subtypes identified to date. The most appropriate methodologies used to distinguish microparticle subtypes will be also presented. Both the megakaryocytes and platelets can generate microparticles. Circulating microparticles originating from megakaryocytes are distinguished from those derived from activated platelets by the presence of CD62P, LAMP-1, and immunoreceptor-based activation motif receptors. Close examination of platelet activation has shed light on a novel mechanism leading to microparticle production. Under physiologic flow, microparticles bud off from long membrane strands formed by activated platelets. Furthermore, mounting evidence supports the notion of microparticle heterogeneity. Platelet microparticles are commonly characterized by the expression of surface platelet antigens and phosphatidylserine. In fact, only a fraction of platelet microparticles harbor phosphatidylserine, and a distinct subset contains respiratory-competent mitochondria. During disease, the microparticle surface may undergo posttranslational modifications such as citrullination, further supporting the concept of microparticle diversity. An appreciation of the microparticle heterogeneity will support their development as potential biomarkers and may reveal functions unique to each microparticle subtype in health and disease.