Grant: Travel Awards - Institute Community Support

Background: In the development of cardiac injury and contractile dysfunction caused by ischemia/reperfusion, matrix mettaloproteinase-2(MMP-2) may be one of the important proteins related to the mechanism of contractile dysfunction. We have shown that phosphorylation of myosin light chain 1 and 2 (MLC1, 2) leads to their increased degradation by MMP-2. Pharmacological approaches have been developed to inhibit MMPs and the development of cardiac injury and contractile dysfunction. However, none of the pharmacological compounds is specific against MMP-2. Small interfering RNA (siRNA) specifically reduces gene expression in cells. Using MMP-2 siRNA as a selected and specific inhibitor of MMP-2, we evaluated the effect of MMP-2 inhibition in cardiomyocytes subjected to ischemia/reperfusion (I/R). We hypothesized that using MMP-2 siRNA will show a protective effect on contractility of cardiomyocytes subjected to I/R. Methods/Results: Adult male rats were anaesthetized and hearts removed. Cardiomyocytes were obtained by enzymatic dissociation. After stabilization period, MMP-2 siRNA was added to cadiomyocytes and incubated for 24 hours and control group was transfected with scramble siRNA according to the manufacturer's protocol. Cardiomyocytes were subjected to ischemia after transfection. Viability, contractility and percentage of contractile cells decreased both after transfection and ischemia in control group. Transfection of MMP-2 siRNA improved these three parameters. Gelatin zymography demonstrated that both MMP-2 and pro-MMP-2 activities were reduced in the MMP-2 siRNA group. Western blot analysis showed increased levels of MLC1 and 2 and decreased level of MMP-2 in MMP-2 siRNA group. Conclusion: We show that MMP-2 siRNA reduces MMP-2 protein and activity levels preventing the degradation of contractile proteins such as MLC1,2 by MMP-2. Therefore we conclude that inhibition of MMP-2 protects contractility of the cardiomyocyte subjected to I/R.