DH. Cardiac matrix metalloproteinase-2 expression independently induces marked ventricular remodeling and systolic dysfunction. Am J Physiol Heart Circ Physiol 292: H1847-H1860, 2007. First published December 8, 2006; doi:10.1152/ajpheart.00434.2006.-Although enhanced cardiac matrix metalloproteinase (MMP)-2 synthesis has been associated with ventricular remodeling and failure, whether MMP-2 expression is a direct mediator of this process is unknown. We generated transgenic mice expressing active MMP-2 driven by the ␣-myosin heavy chain promoter. At 4 mo MMP-2 transgenic hearts demonstrated expression of the MMP-2 transgene, myocyte hypertrophy, breakdown of Z-band registration, lysis of myofilaments, disruption of sarcomere and mitochondrial architecture, and cardiac fibroblast proliferation. Hearts from 8-mo-old transgenic mice displayed extensive myocyte disorganization and dropout with replacement fibrosis and perivascular fibrosis. Older transgenic mice also exhibited a massive increase in cardiac MMP-2 expression, representing recruitment of endogenous MMP-2 synthesis, with associated expression of MMP-9 and membrane type 1 MMP. Increases in diastolic [control (C) 33 Ϯ 3 vs. MMP 51 Ϯ 12 l; P ϭ 0.003] and systolic (C 7 Ϯ 2 vs. MMP 28 Ϯ 14 l; P ϭ 0.003) left ventricular (LV) volumes and relatively preserved stroke volume (C 26 Ϯ 4 vs. MMP 23 Ϯ 3 l; P ϭ 0.16) resulted in markedly decreased LV ejection fraction (C 78 Ϯ 7% vs. MMP 48 Ϯ 16%; P ϭ 0.0006). Markedly impaired systolic function in the MMP transgenic mice was demonstrated in the reduced preload-adjusted maximal power (C 240 Ϯ 84 vs. MMP 78 Ϯ 49 mW/l 2 ; P ϭ 0.0003) and decreased end-systolic pressure-volume relation (C 7.5 Ϯ 1.5 vs. MMP 4.7 Ϯ 2.0; P ϭ 0.016). Expression of active MMP-2 is sufficient to induce severe ventricular remodeling and systolic dysfunction in the absence of superimposed injury. heart failure; fibrosis; mitochondria; sarcomere THE PAST DECADE HAS WITNESSED an increasing interest in the interactions of cardiomyocytes with the extracellular matrix, particularly with regard to the development of cardiac failure and fibrosis. Modulation of the cardiac extracellular matrix by various members of the large matrix metalloproteinase (MMP) gene family has provided important mechanistic insights into the evolution of left ventricular failure in the setting of both ischemic and nonischemic disease (10,11,20,29,49,51). The MMP gene family includes Ͼ20 discrete members, including the interstitial collagenases (e.g., MMP-1 and -13), the gelatinases (MMP-2, -9), and membrane-associated enzymes, including membrane type 1(MT1)-MMP (60). MMP-2 has the been the focus of considerable interest, as previous studies in animal models of heart failure, including the salt-sensitive hypertensive rat (19, 43), mitral regurgitation in the dog (52), and experimental myocardial infarction in the rat (41), have all shown excessive activation of MMP-2 as heart failure progressed. Inhibition of MMP-2 activation with nonselective agents, including an angiotensin-...

Matrix metalloproteinase-2 (MMP-2) plays an essential role in angiogenesis and arteriogenesis, two processes critical to restoration of tissue perfusion after ischemia. MMP-2 expression is increased in tissue ischemia, but the responsible mechanisms remain unknown. We studied the transcriptional activation of the MMP-2 gene in a model of hindlimb ischemia by using various MMP-2-lacZ reporter mice and chromatin immunoprecipitation. MMP-2 activity and mRNA were increased after hindlimb ischemia. Mice with targeted deletion of MMP-2 had impaired restoration of perfusion and a high incidence of limb gangrene, indicating that MMP-2 plays a critical role in ischemia-induced revascularization. Ischemia induced the expression and binding of c-Fos, c-Jun, JunB, FosB, and Fra2 to a noncanonical activating protein-1 (AP-1) site present in the MMP-2 promoter and decreased binding of the transcriptional repressor JunD. Ischemia also activated the expression and binding of p53 to an adjacent enhancer site (RE-1) and increased expression and binding of nuclear factor of activated T-cells-c2 to consensus sequences within the first intron. Deletion of either the 5 AP-1͞ RE-1 region of the promoter or substitution of the first intron abolished ischemia-induced MMP-2 transcription in vivo. Thus, AP-1 transcription factors and intronic activation by nuclear factor of activated T-cells-c2 act in concert to drive ischemia-induced MMP-2 transcription. These findings define a critical role for MMP-2 in ischemia-induced revascularization and identify both previously uncharacterized regulatory elements within the MMP-2 gene and the cognate transcription factors required for MMP-2 activation in vivo after tissue ischemia.angiogenesis ͉ gelatinase ͉ gene expression ͉ skeletal muscle ͉ transcription factor T issue ischemia secondary to arterial ischemia remains a major source of morbidity and mortality. Despite their importance, the cellular and molecular mechanisms that drive transcription of the genes essential for reversal of ischemia in vivo remain largely undefined. Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes important in tissue remodeling and repair. MMP-2 has been implicated in the collateral arterial enlargement that occurs in response to tissue ischemia (1), and its expression is essential for retinal and tumor-induced angiogenesis (2, 3). MMP-2 (gelatinase A) can cleave most extracellular matrix proteins, including collagen, and can proteolytically activate other proenzymes, such as MMP-9. The lack of MMP-14 (membrane-type 1-MMP), the cell surface protease that cleaves proMMP-2 to its active form, abolishes postnatal angiogenesis (4), and targeted deletion of MMP-9 impairs revascularization after hindlimb ischemia (5). Experimental hindlimb ischemia increases expression of MMP-2, MMP-9, and MMP-14 (6). Despite the potential importance of MMP-2 in ischemia-induced angiogenesis and arteriogenesis, the role of MMP-2 in this process and the transcriptional regulatory mechanisms that regulate MMP-2 in tissue is...

Postthrombotic syndrome remains a significant clinical problem after deep venous thrombosis (DVT), but the cellular and molecular mechanisms involved in thrombus resolution and vein wall fibrosis remain undefined. Matrix metalloproteinase (MMP) enzymes are critical to cell migration and matrix breakdown. We identify gene transcription and activity of two MMP isoforms, MMP-2 and MMP-14 (membrane type MMP 1, MT1-MMP) in the resolution phase of experimental DVT and in thrombin-treated endothelial cells. These studies define new proteases potentially important to resolution of DVT and development of postthrombotic syndrome.

SUMMARY Introduction Coronary artery ectasia (CAE) is generally diagnosed in patients undergoing arteriography for presumptive atherosclerotic coronary artery disease. CAE is commonly considered as a variant of atherosclerotic disease; however, recent studies suggest that CAE is the result of a systemic vascular disorder. There is increasing evidence that aneurysmal vascular disease is a systemic disorder characterized by enhanced expression of pro-inflammatory cytokines and increased synthesis of enzymes capable of degrading elastin and other components of the vascular wall. Matrix metalloproteinase-2 degrades a number of extracellular substrates, including elastin and has been shown to play a critical role in the development of abdominal aortic aneurysms. This study characterizes the development of CAE in a unique murine transgenic model with cardiac-specific expression of active MMP-2. Methods Trangenic mice were engineered to express an active form of MMP-2 under control of the α-myosin heavy chain promoter. Coronary artery diameters were quantified, along with studies of arterial structure, elastin integrity and vascular expression of the MMP-2 transgene. Latex casts quantified total coronary artery volumes and arterial branching. Results Midventricular coronary luminal areas were increased in the MMP-2 transgenics, coupled with foci of aneurysmal dilation, ectasia and perivascular fibrosis. There was no evidence for atherogenesis. Coronary vascular elastin integrity was compromised and coupled with inflammatory cell infiltration. Latex casts of the coronary arteries displayed ectasia with fusiform dilatation. Conclusions The MMP-2 transgenic closely replicates human CAE and supports a critical and initiating role for this enzyme in the pathogenesis of this disorder.

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