Deletion of extracellular matrix metalloproteinase inducer/CD147 induces altered cardiac extracellular matrix remodeling in aging mice.

Extracellular matrix metalloproteinase inducer (EMMPRIN), known for its ability to induce matrix metalloproteinase (MMP) expression, was proposed to play a role in the adverse cardiac extracellular matrix remodeling. After observing an age-associated increase in cardiac EMMPRIN expression in both mice and rats, the role and mechanism of action of EMMPRIN was investigated in the myocardial age-associated changes using 3, 12 and 24 month old EMMPRIN knock-out (KO) vs. wild-type (WT) mice, by cardiac echocardiography, Western blots, immunohistochemistry, ELISA and histology. Adilated cardiomyopathy characterized by a decreased ejection fraction and an enlargement of left ventricular chamber (LV) associated with LV hypertrophy, occurred in KO mice as soon as 12 month old. The increase in interstitial collagen deposition during aging in WT mice could not be detected in KO mice. This may be related to the reduced activation (48% reduction; P < 0.05) and signaling (smad2/3 nuclear translocation) of TGF-ß in the 12 month old KO mice which paralleled with a greater reduction in the TGF-ß known activating enzymes such as MT1-MMP and MMP-1 (33% and 37% reduction respectively, between 3 and 12 month old in KO mice; P < 0.05) as well as uPA. These findings demonstrate that EMMPRIN gene silencing is associated with an aberrant extracellular matrix remodeling, characterized by the absence of a detected age-associated fibrosis and consequently to dilated cardiopathy, indicating that a fine regulation of EMMPRIN is essential for the coordinated ECM remodeling during aging.

Intramyocardial protein therapy with vascular endothelial growth factor (VEGF-165) induces functional angiogenesis in rat senescent myocardium.

Myocardial capillary density and angiogenesis are impaired during aging but whether growth factor therapy is able to induce functional neovascularization in senescent heart have never been studied. In 3, 24, 28 and 32 mo male Wistar rats, cardiac hemodynamic measurements indicated heart failure at 28 and 32 mo, associated with left ventricular hypertrophy. VEGF/VEGF-R2, Ang-1/Ang-2/Tie-2 and PTN levels, quantitated in left ventricle by western blotting and immunohistochemistry, showed that VEGF and VEGF-R2 levels were specifically decreased during aging. In vitro angiogenesis ± rhVEGF-165 (5 and 50 ng/mL) was measured in aortic segments in 3D-collagen. Aortic sprouting was decreased during aging but restored by VEGF treatment (P<0.001), similarly in 3 and 24 mo with 50 ng/mLVEGF. Finally, 3 and 24 mo rats were submitted to in vivo intramyocardial rhVEGF-165 (10 micrograms) or saline solution injection and angiogenesis was measured by SPECT imaging of the alpha(v)beta(3) integrin-targeted tracer (99m)Tc-RAFT-RGD, capillary fluorescence staining in isolated perfused heart and vWF and alpha smooth muscle actin immunohistochemistry, 7 and 21 days later. VEGF administration increased capillary density in 3 but also in 24 mo rats at days 7 (+26%, P<0.01) and 21 (+41%, P<0.01) and arteriolar density at day 21 (+36%, P<0.01). Activity of (99m)Tc-RAFT-RGD and capillary fluorescence labeling indicated that new formed capillaries were functional. Cardiac aging was associated with strong VEGF/VEGF-R2 pathway downregulation. VEGF-165 protein therapy was able to induce in vitro and in vivo angiogenesis during aging. In 24 mo hearts, in vivo angiogenesis was functional, sustained and comparable to neovascularization observed in 3 mo hearts.