Platelet microparticle: a sensitive physiological "fine tuning" balancing factor in health and disease.

Platelet microparticles (PMPs) have long been regarded as inert "platelet dusts". They have now taken a center stage on the clinical research scene of transfusion medicine, being actually seen as long-stretch hands of platelets that exert a physiological role beyond the initial site of activation. These 0.05 µm to 0.8 µm microvesicles, delimited by a phospholipidic bilayer, are released by platelet membranes following activation by agonists, complement activation, or high shear forces. They can also be generated as a result of platelets and megakaryocyte senescence or cytoskeletal abnormalities. PMPs may orchestrate a delicate hemostatic balance in health, and act as procoagulant vectors in diseases triggering thrombosis. Furthermore, through their potential cargo of growth factors, microRNA and various bioactive molecules, they may promote healing in health, but, on the other side of the coin, can act as pro-inflammatory carriers and may contribute to cancer growth as an actor of the platelet-cancer loop. Through their cellular interactions they also interplay with the immune system. Their capacity to be generated by shear forces and contact with surfaces during the processing of blood and blood components, which may trigger transfusion reactions, make them also an integral part of transfusion medicine. Given their documented association with pathological conditions, PMP may serve as biomarkers for disease status or as a possible new target for anti-platelet drugs to treat cancer or inflammation.