Abstract P108: Circulating Matrix Metalloproteinase-2 Invades the Heart and Causes Heart Failure

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Background: An increase in MMP-2 levels is reported in heart failure (HF). However the role of MMP-2 in the pathogenesis of HF remains unclear. The aim of the present study was to determine the effect of increased circulating levels of MMP-2 on heart morphology and function. Methods and Results: Purified MMP-2 catalytic domain fused to GFP (catMMP-2/GFP) or saline (control) was injected into 11-wk-old male C57BL/6 mice for four weeks. The fluorescent active protein was tracked in vivo and homed in the heart. Cardiomyocyte diameter not changed between groups (catMMP-2/GFP: 11.37 ± 0.25 μm, n=7; Control: 11.38 ± 0.13 μm, n=7; P =0.97). On the other hand, fibrosis increased in the hearts of catMMP-2/GFP mice (0.82 ± 0.05% area/field, n=7 vs Control: 0.58 ± 0.02% area/field, n=7; P< 0.05). Apoptotic stained nuclei in the left ventricle (LV) of catMMP-2/GFP injected-mice amounted to 7.24%, n=4, P<0,05, whilst the LV of control animals only exhibited 0.27%, n=4. catMMP-2/GFP localized in the heart interstitium, where increased proteolytic activity (15.13 ± 1.33 U, n=5 vs Control: 9.70 ± 0.42 U, n=5; P <0.05). Hearts of catMMP-2/GFP mice showed 25% decrease in cardiac output (13 ± 1 mL/min, n=9 vs Control: 17 ± 1 mL/min, n=9), 30% decrease in ejection fraction (40 ± 2 %, n=9 vs Control: 56 ± 2 %, n=9) and stroke volume (28 ± 2 μL, n=9 vs Control: 40 ± 2 μL, n=9), and 34% decrease in fractional shortening (18 ± 1 %, n=9 vs Control: 28 ± 1 %, n=9) ( P <0.05 for all data).Western blotting showed 40% decrease in N-cadherin in animals that received catMMP-2/GFP (0.53 ± 0.08 U, n=6 vs control: 0.89 ± 0.11 U, n=6; P <0.05). Expression of signaling proteins also changed in LV of catMMP-2/GFP mice: TGF-β1 expression increased by 30% (0.60 ± 0.07 U, n=7 vs control: 0.40 ± 0.05 U, n=7, P<0,05), pAkt/Akt decreased by 40% (0.46 ± 0.05 U, n=7 vs control: 0.76 ± 0.11 U, n=7; P <0.05), pSMAD2/total SMAD2 ratio increased (1.88 ± 0.22 U, n=6 vs control: 0.93±0.12 U, n=6, P<0,05), and pSMAD3/total SMAD3 ratio increased (1.24 ± 0.22 U, n=7 vs control: 0.33 ± 0.07 U, n=7; P <0.05). Conclusions: Circulating active MMP-2 homing to the heart interstitium degrades N-cadherin and induces TGF-β1 overexpression, leading to apoptosis, and fibrosis. This mechanism may account for heart function loss when plasma levels of MMP-2 increase.