Microparticles and Exosomes: Are They Part of Important Pathways in Sepsis Pathophysiology?

Microparticles are a heterogeneous population of small membrane-coated vesicles released by several cell lines upon activation or apoptosis. Microparticles generation seems to be a well regulated process, although these vesicles are highly variable in size, composition and function. Despite being previously considered inert debris without specific function, recent data demonstrated important pathophysiological mechanisms orchestrated by microparticles in vascular diseases associated with endothelial dysfunction. These vesicles have been implicated, among others, in the pathogenesis of thrombosis, inflammation, atherosclerosis and vascular cell proliferation. In addition to microparticles, activation of the endocytic-lisosomal cellular system of circulating cells induce the release of smaller vesicles denominated exosomes that can also participate in vascular derangement. This role of microparticles and exosomes in mediating vascular dysfunction suggests that they may represent novel pathways in short or long-distance paracrine transcellular signaling in vascular environment. The mechanisms involved in the origin of microparticles and exosomes, their composition and participation in the pathogenesis of sepsis will be discussed in this review.