Microparticles in cardiovascular disease pathophysiology and outcomes.

Microparticles (MPs) are vesicles less than one micron in diameter shed from the plasma membranes of cells that are injured, activated, or undergoing apoptosis. MPs are shed from several types of cells, and the cells of origin can be identified using combinations of antigenic markers. Platelet MPs, which play a role in coagulation and atherogenesis, are the most abundant MPs in the circulation. In vivo studies have demonstrated platelet MP levels to be higher in patients who have had acute ischemic stroke and in patients with greater degrees of retinopathy. In addition, platelet MP levels have been shown to be higher in patients with severe hypertension and in those with increased coronary heart disease risk. Endothelial MPs affect vascular tone, permeability, and hemostasis. Higher endothelial MP levels have been shown to correlate with loss of flow-mediated dilation, arterial stiffness, and severe hypertension. Most compelling are recent cohort studies that have shown endothelial MP levels to be independent predictors of cardiovascular disease events. Although more research is needed, studies suggest that MPs may have clinical applications including utility as biomarkers, use in improving cardiovascular disease risk prediction, and as potential targets of therapy.