Abstract
Microparticles (MPs) are small vesicles resulting from the shedding of cellular membrane
during activation or apoptosis processes. Beyond their well-described procoagulant
property, accumulating data show that specific endothelial cell-, leukocyte-, tumor-derived
MPs bind plasminogen and vectorize plasminogen activators, leading to an efficient
plasmin generation and matrix metalloproteinases activation. This review focuses on
the molecular equipment of MPs subpopulations that identify MPs as efficient support
for plasmin generation and the potential consequences of this new function. By the
combined facts that MPs may disseminate, concentrate active proteolytic molecules
and represent a protective environment against soluble inhibitors, MPs behave as an
efficient catalytic surface involved in vascular and matrix proteolysis–related biological
processes. The existence of this proteolytic MPs in the circulation or in body fluids
raises the question about the physiological relevance of this activity. Consequences
are suggested in many biological processes such as fibrinolysis, cell survival, matrix
remodeling, angiogenesis, and tumor metastasis. However, further studies will be necessary
to determine the extent in which in vivo MPs contribute to these pathophysiological
mechanisms and how this circulating property of MPs may represent a new biomarker
in specific clinical situations.
Keywords
microparticles - plasmin - matrix metalloproteinases - proteolysis
