Abstract 2097: Cardiac-specific Overexpression of EcSOD From an AAV9-Pseudotyped Vector Increases Capillary Density and Reduces Infarct Size
Introduction: We hypothesized that AAV9-mediated overexpression of extracellular superoxide dismutase (EcSOD) using the cardiac Troponin-T (cTnT) promoter would increase capillary density and protect the LV against myocardial infarction (MI).
Methods: AAV vectors cross-packaged into AAV9 capsids expressing EcSOD or eGFP from the cTnT promoter (AcTnTEcSod or AcTnTeGFP) were injected IV into 4 –5 wk old C57Bl/6 mice (3×1011 vp/mouse). Four wks after injection, MI was induced by a 30 min coronary occlusion. Infarct size and area at risk (A@R) were measured 24 h later by TTC and Phthalo blue staining, respectively. Capillary density was measured 4 wks post injection in myocardial sections immunostained for PE-CAM. Myocardial perfusion was measured by MRI using arterial spin labeling, both prior to and 4 wks after vector injection.
Results: IV injection of AcTnTEcSOD provided uniform EcSOD overexpression throughout the myocardium (Panel A). Infarct size (as % A@R, Panel B) was reduced by 45% in the EcSOD group (33.9 ± 6.3, mean ± SEM, n=4) compared to the eGFP group (61.3 ± 3.8, n=4, p<0.05). Capillary density was 23.6% higher in EcSOD mice (5446 ± 368/mm2) compared to eGFP mice (4405 ± 271/mm2, p<0.05). EcSOD expression increased myocardial perfusion by 30% from 4.3 ± 0.5 before to 5.6 ± 0.3 ml/g-min at 4 wks post injection (p<0.05).
Conclusions: Transcriptional targeting with the cTnT promoter in combination with the high-efficiency AAV9 capsid provides therapeutic levels of cardiac-specific gene expression. AAV-mediated cardiac overexpression of EcSOD significantly increases capillary density, improves myocardial perfusion and reduces infarct size in the murine heart.