Selective HDL-Raising Human Apo A-I Gene Therapy Counteracts Cardiac Hypertrophy, Reduces Myocardial Fibrosis, and Improves Cardiac Function in Mice with Chronic Pressure Overload

Abstract

Epidemiological studies support an independent inverse association between high-density lipoprotein (HDL) cholesterol levels and heart failure incidence. The effect of selective HDL-raising adeno-associated viral serotype 8-human apolipoprotein (apo) A-I (AAV8-A-I) gene transfer on cardiac remodeling induced by transverse aortic constriction (TAC) was evaluated in C57BL/6 low-density lipoprotein receptor-deficient mice. Septal wall thickness and cardiomyocyte cross-sectional area were reduced by 16.5% (p < 0.001) and by 13.8% (p < 0.01), respectively, eight weeks after TAC in AAV8-A-I mice (n = 24) compared to control mice (n = 39). Myocardial capillary density was 1.11-fold (p < 0.05) higher and interstitial cardiac fibrosis was 45.3% (p < 0.001) lower in AAV8-A-I TAC mice than in control TAC mice. Lung weight and atrial weight were significantly increased in control TAC mice compared to control sham mice, but were not increased in AAV8-A-I TAC mice. The peak rate of isovolumetric contraction was 1.19-fold (p < 0.01) higher in AAV8-A-I TAC mice (n = 17) than in control TAC mice (n = 29). Diastolic function was also significantly enhanced in AAV8-A-I TAC mice compared to control TAC mice. Nitro-oxidative stress and apoptosis were significantly reduced in the myocardium of AAV8-A-I TAC mice compared to control TAC mice. In conclusion, selective HDL-raising human apo A-I gene transfer potently counteracts the development of pressure overload-induced cardiomyopathy.

Keywords: apolipoprotein A-I; cardiac function; cardiac hypertrophy; gene therapy; heart failure; high-density lipoproteins; oxidative stress; pressure overload.

Figure 1

Comparison of Kaplan–Meier survival curves during an eight week follow-up period after transverse aortic constriction (TAC). Control TAC mice (red line) and adeno-associated viral serotype 8-human apolipoprotein A-I (AAV8-A-I) TAC mice (green line) are compared. The 0 day time-point corresponds to the induction of TAC at the age of 14 weeks. Survival analysis was performed by log-rank test.

Figure 2

Representative Sirius red-stained cross-sections of sham hearts and transverse aortic constriction (TAC) hearts at day 56 after operation. Scale bar represents 1 mm.

Figure 3

(Immuno)histochemical analysis of the myocardium of sham mice and transverse aortic constriction (TAC) mice at day 56 after operation. Representative photomicrographs show laminin-stained cardiomyocytes, CD31-positive capillaries, and Sirius red-stained interstitial collagen viewed under polarized light. Scale bar represents 50 μm. Insets show a 4× magnification of the boxed region.

Figure 4

Quantification of oxidative stress and cardiomyocyte apoptosis in sham mice and in transverse aortic constriction (TAC) mice at day 56 after operation. Sham mice and TAC mice are indicated by open bars and closed bars, respectively. Plasma thiobarbituric acid-reactive substances (TBARS) expressed as plasma malondialdehyde equivalents, the percentage of 3-nitrotyrosine-positive myocardial area, and cleaved caspase-3-positive cells in the myocardium are shown in panels (A–C), respectively. Panel (D) illustrates representative photomicrographs showing myocardial sections stained for 3-nitrotyrosine. All data represent means ± SEM (n = 10). Scale bar represents 50 µm.