Cardiac matrix metalloproteinase-2 expression independently induces marked ventricular remodeling and systolic dysfunction

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 alpha-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 +/- 3 vs. MMP 51 +/- 12 mu l; P = 0.003] and systolic ( C 7 +/- 2 vs. MMP 28 +/- 14 mu l; P = 0.003) left ventricular ( LV) volumes and relatively preserved stroke volume ( C 26 +/- 4 vs. MMP 23 +/- 3 mu l; P = 0.16) resulted in markedly decreased LV ejection fraction ( C 78 +/- 7% vs. MMP 48 +/- 16%; P = 0.0006). Markedly impaired systolic function in the MMP transgenic mice was demonstrated in the reduced preload-adjusted maximal power ( C 240 +/- 84 vs. MMP 78 +/- 49 mW/mu l(2); P = 0.0003) and decreased end-systolic pressure-volume relation ( C 7.5 +/- 1.5 vs. MMP 4.7 +/- 2.0; P = 0.016). Expression of active MMP-2 is sufficient to induce severe ventricular remodeling and systolic dysfunction in the absence of superimposed injury.