Endothelial cell microparticles act as centers of matrix metalloproteinsase-2 (MMP-2) activation and vascular matrix remodeling

Endothelial cell (EC)-derived microparticles (MPs) are small membrane vesicles associated with various vascular pathologies. Here, we investigated the role of MPs in matrix remodeling by analyzing their interactions with the extracellular matrix. MPs were shown to bind preferentially to surfaces coated with matrix molecules, and MPs bound fibronectin via integrin aV. MPs isolated from EC-conditioned medium (Sup) were significantly enriched for matrix-altering proteases, including matrix metalloproteinases (MMPs). MPs lacked the MMP inhibitors TIMP-1 and TIMP-2 found in the Sup and, while Sup strongly inhibited MMP activities but MPs did not. In fact, MPs were shown to bind and activate both endogenous and exogenous proMMP-2. Taken together, these results indicate that MPs interact with extracellular matrices, where they localize and activate MMP-2 to modify the surrounding matrix molecules. These findings provide insights into the cellular mechanisms of vascular matrix remodeling and identify new targets of vascular pathologies. J. Cell. Physiol. 227: 534549, 2012. (C) 2011 Wiley Periodicals, Inc.