Myocardial overexpression of TIMP3 after myocardial infarction exerts beneficial effects by promoting angiogenesis and suppressing early proteolysis

Myocardial infarction (MI) results in loss of cardiomyocytes, adverse extracellular matrix (ECM) and structural remodeling, and left ventricular (LV) dilation and dysfunction. Tissue inhibitors of metalloproteinase (TIMPs) inhibit matrix metalloproteinases (MMPs), the main regulators of ECM turnover. TIMPs also have MMP-independent functions. TIMP3 levels are reduced in the heart within 24 h of MI in mice. We investigated if overexpression of TIMP3 post-MI limits adverse remodeling and LV dilation and dysfunction. MI was induced by left anterior descending coronary artery ligation in 10- to 12-wk-old male C57BL/6J mice, and adenoviral constructs expressing human (h)TIMP3 (Ad-hTIMP3) or no TIMP (Ad-Null) were injected in the peri-infarct zone (5.4 × 10 plaque-forming units/heart, 5 injections/heart). Cardiac function assessed by echocardiography showed improved LV physiology and reduced LV dilation after TIMP3 overexpression compared with the Ad-Null-MI group. Post-MI adverse remodeling was attenuated in the Ad-hTIMP3-MI group, as assessed by greater cardiomyocyte density, less infarct expansion, and ECM disruption. TIMP3 overexpression blunted the early rise in proteolytic activities post-MI. A higher density of coronary arteries and a greater number of proliferating endothelial cells were detected in the infarct and peri-infarct regions in the Ad-hTIMP3-MI group compared with the Ad-Null-MI group. In vitro three-dimensional angiogenesis assay confirmed that recombinant TIMP3 promotes angiogenesis in human endothelial cells, although biphasically and in a dose-dependent manner. Intriguingly, overexpression of Ad-hTIMP3 at 10-fold higher concentration had no beneficial effects, consistent with antiangiogenic effects of TIMP3 at higher doses. In conclusion, optimal overexpression of TIMP3 can be a promising therapeutic approach to limit adverse post-MI remodeling by dually inhibiting early proteolysis and promoting angiogenesis. Here, we report that tissue inhibitor of metalloproteinase 3 overexpression after myocardial infarction improves myocardial structural remodeling and function by promoting angiogenesis and inhibiting early proteolysis. This demonstrates the therapeutic potential of preserving the local balance of tissue inhibitor of metalloproteinase 3 in the heart given its diverse functions in modulating different processes involved in the adverse postmyocardial infarction remodeling.