Abstract Body (Do not enter title and authors here): Background:
We previously discovered that chronic deficiency of cardiac natriuretic peptides (NP) sensitized mice to sudden death and ventricular arrhythmias after acute myocardial stress. Likewise, it has been shown in humans with heart failure that despite elevated circulating levels of cardiac NP there is a functional deficiency at the cellular level. We hypothesized that selectively increasing cardiomyocyte protein kinase G 1 (PKG1) protein levels could counteract the cardiomyocyte effects of functional NP deficiency in cardiomyopathy.
Methods:
We utilized a murine model of dilated cardiomyopathy (DCM) caused by deletion of cardiac myosin binding protein 3 (Mybpc3^-/-) and a murine model of hypertrophic cardiomyopathy (HCM) caused be a mutation in myosin heavy chain 6 (Myh6^R404Q/WT). We selectively overexpressed human PKG1 in cardiomyocytes using a AAV9 viral vector and a cardiac troponin T minimal promoter (AAV9-cTnT-hPKG1). Heart structure and function were assessed using echocardiography. Immunohistochemistry and biochemical analyses were conducted to characterize the effects of PKG1 overexpression.
Results:
We found that despite elevated circulating NP levels, there was a significant reduction in myocardial cGMP concentrations in Mybpc3^-/- left ventricular (LV) tissue (Wildtype 54.1 ± 4.3 vs Mybpc3^-/- 42.7 ± 3.7 fmoles/mg tissue, P=0.03). Selective cardiomyocyte overexpression of PKG1 caused a significant improvement in LV systolic function in adult Mybpc3^-/- animals after 30 days (Figure 1). Cardiomyocyte overexpression of PKG1 had no significant impact on LV structure in the Mybpc3^-/- model. To determine if cardiomyocyte overexpression of PKG1 can improve LV diastolic function, we utilized the Myh6^R404Q/WT murine HCM model which develops LV hypertrophy with preserved LV systolic function (IVSd (mm) Wildtype 0.85 ± 0.05 vs Myh6 1.2 ± 0.05, P<0.0001). Interestingly, overexpression of cardiomyocyte PKG1 normalized LV diastolic function in this HCM model (Figure 2). The improvement in diastolic function in this HCM model occurred without any significant changes in LV systolic function (LV FS (%) pre 31 ± 2.2 vs post 33 ± 2.8, P=0.7) or hypertrophy (IVSd (mm) pre 1.2 ± 0.05 vs post 1.25 ± 0.06, P=0.41).
Conclusions:
Collectively, our results show that a AAV9 viral vector selectively overexpressing PKG1 in cardiomyocytes can rapidly improve LV systolic and diastolic function in murine models of dilated and hypertrophic cardiomyopathy.