What are Microparticles? 

Platelet-derived microparticles range in diameter from 100nm to 1µm. Microparticles of platelet origin are the most abundant and account for 70% to 90% of circulating microparticles in the bloodstream. In addition, red blood cells, endothelial cells and white blood cells can also generate microparticles,

In circulation, microparticles are produced by platelets in the presence of strong agonist and stress (high shear stress, low temperature). During platelet activation, vesicles are formed from the plasma membrane leading to the formation of microparticles.  In addition to releasing chemokines that induce angiogenesis, microparticles have been implicated in thrombosis occurring in cardiovascular disease, cancer, diabetes, inflammation and infection. Studies have shown that microparticles are transferred from the donor blood to the corresponding platelet concentrate. 

In platelet products, microparticle concentrations have been shown to increase during platelet concentrate aging, transport, irradiation or pathogen inactivation. Consequently, high microparticle content in platelet concentrates might be an indicator that the platelets had been exposed to stress, including platelet storage lesion.