Matrix Metalloproteinase (MMP)-3 Activates MMP-9 Mediated Vascular Smooth Muscle Cell Migration and Neointima Formation in Mice

Abstract

Objective-Several matrix metalloproteinases (MMPs) have been implicated in extracellular matrix destruction and other actions that lead to plaque rupture and myocardial infarction. Conversely, other MMPs have been shown to promote vascular smooth muscle cell (VSMC)-driven neointima formation, which contributes to restenosis, fibrous cap formation, and plaque stability. MMP-3 knockout reduced VSMC accumulation in mouse atherosclerotic plaques, implicating MMP-3 in neointima formation. We therefore investigated the effect of MMP-3 knockout on neointima formation after carotid ligation in vivo and VSMC migration in vitro. Methods and Results-Twenty-eight days after left carotid ligation, MMP-3 knockout significantly reduced neointima formation (75%, PϽ0.01) compared with wild-type (WT) littermates, and also reduced remodeling of ligated and contralateral carotid arteries. Gelatin zymography illustrated that MMP-3 knockout abolished MMP-9 activation in ligated carotids and scratch-wounded VSMC cultures. MMP-3 knockout also attenuated VSMC migration into a scratch wound by 59% compared with WT cells. Addition of exogenous MMP-3 or activated MMP-9 restored migration of MMP-3 knockouts to that of WT VSMCs, but exogenous MMP-3 had no effect on migration in MMP-9 knockout VSMCs. MMP-9 knockout or knockdown with small interfering RNA significantly retarded VSMC migration to the same extent as MMP-3 knockout. Conclusion-These results indicate for the first time that MMP-3 mediated activation of MMP-9 is required for efficient neointima formation after carotid ligation in vivo and for VSMC migration in vitro, whereas MMP-12 plays a redundant role. These findings add to the understanding of MMP action in plaque stability and restenosis. and their associated extracellular matrix contributes to occlusive cardiovascular pathologies, including restenosis and atherosclerosis. 1 In the healthy blood vessel, VSMCs reside within the media in a quiescent state. However, after injury, they migrate into the intima, where their growth can result in restriction of normal blood flow. 2 Excessive intimal thickening may compromise lumen patency directly (eg, in the case of restenosis) or accelerate the genesis of superimposed atherosclerosis (eg, in native arteries or vein grafts). 3 On the other hand, VSMC growth within the fibrous cap of an atherosclerotic plaque is considered favorable because it is associated with a stable lesion phenotype, less susceptible to plaque rupture and its deleterious clinical sequelae. 4 The matrix-degrading metalloproteinases (MMPs) are a large family of genetically related enzymes that were defined initially by their ability to degrade many of the extracellular matrix components that are found within healthy and diseased blood vessels. More recently, a variety of nonmatrix substrates, including cytokines and cell surface proteins, have also been identified. 5 As a consequence, 2 major roles in the development of cardiovascular pathologies have been attributed to MMPs: net degradation of the extracellular ma...

Pivotal Role of Serum- and Glucocorticoid-Inducible Kinase 1 in Vascular Inflammation and Atherogenesis

“…Besides contributing to plaque progression and instability, MMP-9 probably has beneficial effects on adaptive plaque remodeling processes 50 because MMP-9 is necessary for vascular smooth muscle cell-driven fibrous cap formation promoting plaque stability. 51,52 Moreover, the results of this study reveal a putative mechanism in the SGK1-dependent upregulation of MMP-9 expression. Monocyte as well as monocyte-derived macrophage MMP-9 is tightly regulated at the transcriptional level by the transcription factor NF-κB 2,16 and rapidly increases in processes involved in vascular inflammation and atherogenesis.…”

Overexpression of mimecan in human aortic smooth muscle cells inhibits cell proliferation and enhances apoptosis and migration

“…MMPs, in particular MMP-2 and MMP-9, contribute to the pathogenesis of atherosclerosis by facilitating VSMC migration via matrix disruption (27). Numerous studies have demonstrated that MMP-2 and MMP-9 participate in the development of atherosclerosis by regulating the proliferation and migration of VSMCs (28)(29)(30)(31)(32). A knockout study demonstrated that MMP-9 is required for neointimal and arterial lesion formation by regulating the migration and proliferation of VSMCs (26,28).…”

Involvement of Angiotensin II Type 1 and 2 Receptors in Gelatinase Regulation in Human Carotid Atheroma <i>in vitro </i>

“…The gelatinase subfamily, comprising, MMP-2 and -9, most efficiently cleave denatured collagens (rather than structural fibrillar collagens) and elastin 9) and have been implicated as key players in the proliferation and migration of SMCs from the media to the fibrous cap thereby possibly providing plaque stabilising effects 10) . MMP-3 mediated activation of MMP-9 has also been implicated in efficient SMC migration and neointima formation in mice 11) . The development of an unstable plaque phenotype in a murine model with less SMCs relative to macrophages was also favoured by broad spectrum inhibition of MMP activity 12) .…”