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.