Matrix management: assigning different roles for MMP-2 and MMP-9 in vascular remodeling.

Abstract

Geometric remodeling is an important component of vascular pathologies, including restenosis and atherosclerosis. Although our understanding of the precise events involved in vascular remodeling is far from complete, it is generally accepted that local breakdown of extracellular matrix (ECM), smooth muscle cell migration, and matrix reorganization are important components.1 In this respect, particular attention has been directed toward the role of matrix metalloproteinases (MMPs), enzymes capable of remodeling the ECM. However, being able to understand the specific contribution of individual members of a proteinase family that share overlapping substrates is a significant challenge. See page 54 MMPs are Zn-containing neutral endopeptidases. At least 23 different MMPs have been identified that, as a family, have the capacity to degrade all components of the ECM, in addition to some nonmatrix substrates.2 Within the family, several subgroups exist, based on substrate specificities or domain structures. The activity of MMPs is controlled at several distinct levels, including transcription, activation of zymogens, and interaction with specific inhibitors, the TIMPs (tissue inhibitors of MMPs). The two gelatinases MMP-2 and MMP-9 have received particular attention in analysis of vascular remodeling due to their expression by smooth muscle cells and leukocytes and ability to breakdown components of the basement membrane and collagens. At least in vitro, both enzymes have a very similar substrate profile. However, their expression in the vascular wall is differently controlled, in that a basal expression of MMP-2 can be detected within the media, whereas MMP-9 expression is only apparent …