In conclusion, we propose that MMP-9 and -12 promote intimal thickening by independent cleavage of N-cadherin, which elevates VSMC proliferation via beta-catenin signalling.

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...

Neutrophils are the most abundant innate immune cell with critical anti-microbial functions. Since the discovery of granulocytes at the end of the nineteenth century, the cells have been given many names including phagocytes, polymorphonuclear neutrophils (PMN), granulocytic myeloid derived suppressor cells (G-MDSC), low density neutrophils (LDN) and tumor associated neutrophils (TANS). This lack of standardized nomenclature for neutrophils suggest that biologically distinct populations of neutrophils exist, particularly in disease, when in fact these may simply be a manifestation of the plasticity of the neutrophil as opposed to unique populations. In this review, we profile the surface markers and granule expression of each stage of granulopoiesis to offer insight into how each stage of maturity may be identified. We also highlight the remarkable surface marker expression profiles between the supposed neutrophil populations.