OBJECTIVEChronic myocardial ischemia (CMI) has become the most important cause of heart failure (HF) all over the world. The aim of the current study was to investigate the effects of Sarco-endoplasmic reticulum calcium ATPase 2a (SERCA2a) gene transfer on cardiac function and endoplasmic reticulum stress (ERS) associated myocardial apoptosis in a minipig HF animal model induced by CMI.

METHODSHF was induced in minipigs by implantation of ameroid constrictor in the initial segment of left anterior descending (LAD) branch of coronary artery. After confirmation of myocardial perfusion defects and cardiac function impairment by myocardial perfusion imaging and echocardiography, animals were divided into 4 groups (n = 4 each): HF group, HF + enhanced green fluorescent protein (EGFP) group, HF + SERCA2a group, and shamed animals as control group. A total amount of 1 × 10(12) v.g. of rAAV1-EGFP or rAAV1-SERCA2a were injected intramyocardially to each animal of HF + EGFP and HF + SERCA2a groups. Sixty days after gene transfer, protein level and activity of SERCA2a were examined, cardiac functions and changes of serum inflammatory and neuro-hormonal factors were determined. Apoptotic index of the ischemic myocardium, protein levels of ER stress marker glucose regulated protein 78 (GRP 78) and ER stress specific apoptotic marker caspase-12 were also assayed.

RESULTSAt the study end, echocardiographic and hemo dynamic measurements indicated a significant improvement of both cardiac systolic and diastolic function in HF + SERCA2a group compared with HF/HF + EGFP groups [LVEF (60.2 ± 8.6)% vs (44.2 ± 7.1)% and (46.8 ± 6.7)%, Ev/Av 1.28 ± 0.24 vs 0.77 ± 0.17 and 0.80 ± 0.21, +dp/dt(max) (2713.9 ± 434.0) mm Hg/s (1 mm Hg = 0.133 kPa) vs (1892.3 ± 434.2) mm Hg/s and (1931.2 ± 397.4) mm Hg/s, -dp/dt(max) (1422.1 ± 334.4) mm Hg/s vs (848.3 ± 308.3) mm Hg/s and (849.5 ± 278.3) mm Hg/s, P < 0.05], along with increase in both SERCA2a protein level (1.13 ± 0.26 vs 0.73 ± 0.17 and 0.64 ± 0.18, P < 0.05) and activity [(16.2 ± 5.5) IU/ml vs (7.9 ± 3.1) IU/ml and (7.5 ± 2.8) IU/ml, P < 0.05] compared with HF/HF + EGFP groups. Serum concentrations of inflammatory factor tumor necrotic factor α [(382.3 ± 114.4) ng/L vs (732.3 ± 201.4) ng/L and (689.8 ± 192.5) ng/L, P < 0.05], neural-hormonal factors brain natriuretic peptide [(142.6 ± 45.3) ng/L vs (422.3 ± 113.6) ng/L and (393.7 ± 103.3) ng/L, P < 0.01], endothelin-1 [(111.4 ± 37.5) ng/L vs (193.5 ± 54.3) ng/L and (201.0 ± 72.1) ng/L, P < 0.05] and angiotensin II [(189.7 ± 65.2) µg/L vs (538.3 ± 135.2) µg/L and (525.5 ± 144.1) µg/L, P < 0.01] were also significantly decreased in HF + SERCA2a group compared with HF/HF + EGFP groups. The apoptotic index [(12.71 ± 4.11)% vs (23.22 ± 7.23)% and (24.31 ± 6.38)%, P < 0.05], protein levels of GRP 78 (1.27 ± 0.33 vs 3.23 ± 1.14 and 4.18 ± 1.13, P < 0.05) and protein level ratios of cleaved caspase-12 to total caspase-12 [(4.62 ± 1.93)% vs (9.71 ± 2.70)% and (10.14 ± 2.81)%, P < 0.05] were also significantly reduced in the ischemic myocardium of HF + SERCA2a group compared with the HF/HF + EGFP groups.

CONCLUSIONOverexpression of SERCA2a significantly improved cardiac systolic and diastolic function in this HF model partly through attenuation of ER stress related myocardial apoptosis, suggesting its therapeutic potential for CMI related heart failure.