Selective Disruption of MMP-2 Gene Exacerbates Myocardial Inflammation and Dysfunction in Mice with Cytokine-induced Cardiomyopathy

Tumor necrosis factor-alpha (TNF-alpha) plays a pathophysiological role in the development and progression of heart failure. Matrix metalloproteinase (MMP)-2 is involved in extracellular matrix remodeling. Recent evidence suggests a protective role for this protease against tissue inflammation. Although MMP-2 is upregulated in the failing heart, little is known about its pathophysiological role. We thus hypothesized that ablation of the MMP-2 gene could affect cardiac remodeling and failure in TNF-alpha-induced cardiomyopathy. We crossed transgenic mice with cardiac-specific overexpression of TNF-alpha (TG) with MMP-2 knockout (KO) mice. Four groups of male and female mice were studied: wild-type (WT) with wild MMP-2 (WT/MMP(+/+)), WT with MMP-2 KO (WT/MMP(-/-)), TNF-alpha TG with wild MMP-2 (TG/MMP(+/+)), and TG with MMP-2 KO (TG/MMP(-/-)). The upregulation of MMP-2 zymographic activity in TG/MMP(+/+) mice was completely abolished in TG/MMP(-/-) mice, and other MMPs and tissue inhibitors of metalloproteinase were comparable between groups. Survival was shorter for male TG/MMP(-/-) than TG/MMP(+/+) mice. Female TG/MMP(-/-) mice were more severely affected than TG/MMP(+/+) mice with diminished cardiac function. Myocardial TNF-alpha and other proinflammatory cytokines were increased in TG/MMP(+/+) mice, and this increase was similarly observed in TG/MMP(-/-) mice. The extent of myocardial infiltrating cells including macrophages was greater in TG/MMP(-/-) than in TG/MMP(+/+) mice. Selective ablation of the MMP-2 gene reduces survival and exacerbates cardiac failure in association with the increased level of myocardial inflammation. MMP-2 may play a cardioprotective role in the pathogenesis of cytokine-induced cardiomyopathy.