Particular attention had been paid to this relatively novel method of cell communication. Cells of various types release small particles into body fluids, and these particles apparently transfer messages to other cells and tissues. The term suggested for this signaling method was "rececrine," which refers to the "secretion" of an active cellular receptor that can be incorporated to the particle cargo and transferred to a target cell, where it can function and signal in an ectopic manner. 1 MP are released from the plasma membrane of cells by outward budding of membrane vesicles, following disruption of the natural asymmetrical distribution of membrane phospholipids, under conditions of cell activation, mechanical stress, and apoptosis. 2 Studies suggest that MP shedding is a highly regulated process that occurs in a spectrum of cell types, and MP have been widely detected in various biological fluids, including peripheral blood and urine.MP contain proteins derived from the parent cell, although their protein and membrane content are not identical to that of the original cell. In recent years, it has become clear that they have important biological functions, including horizontal transfer of bioactive molecules, such as receptors, integrins, 3 growth factors, RNAs, 4 and microRNAs. The function of MP is dependent on the cell type from which they originate and their content. Platelet-derived microparticles (PMP) participate in blood coagulation, whereas MP secreted by skeletal cells initiate bone mineralization, and MP secreted by normal endothelial cells have been implicated in angiogenesis. 5 It was shown that the effect of endothelial-derived MP on angiogenesis is dose-dependent and that whereas endothelialderived MP promote angiogenesis in vitro in low concentrations, high concentrations may suppress angiogenesis. 6,7 Tumor cell-derived MP have been shown to facilitate extracellular matrix invasion and evasion of the immune response. 8 It is important to discriminate MP from exosomes, which originate from intracellular multivesicular bodies. Exosomes are smaller in size (Ͻ0.1 m) and are morphologically distinct. Muralidharan-Chari et al 9 showed that MP appear to be rather heterogeneous in size, ranging from 100 nm to 1 m in diameter, whereas exosomes are more uniform and range from 50 to 80 nm in diameter. MP also pellet at less than 100 000 g, compared with exosomes, which need at least Angiogenesis is a tightly regulated process that involves endothelial cell survival, proliferation, migration, differentiation, and morphological changes, such as tube formation. It is a major process in many pathological conditions, such as tumor growth, diabetic retinopathy, and inflammation, as well as in embryonic development and wound healing. 10 In this review, we focus on MP involvement in various pathological conditions, showing their potential use as disease markers, and we present some data emphasizing their potential application in tissue regeneration.
MP Affect Endothelial CellsMost of the research regarding MP h...