Preserved Myocardial Energetics After In Vivo Overexpression of Cardiac b-Adrenergic Receptor Kinase Inhibitor Using scAAV6-Mediated Molecular Cardiac Surgery with Recirculating Delivery (MCARDTM)

Transgenic alteration of b-adrenergic signaling has produced new insight into the role of G protein-coupled receptor kinases (GRK) in heart failure (HF). GRK2/bARK1, specifically, has been implicated in the pathogenesis of dysfunctional cardiac bAR signaling and worsening HF. Murine studies have demonstrated bARKct as an effective in vivo inhibitor of bARK1 activity via Gbg sequestration, highlighting a potential therapeutic target. This study's aim was to examine the effects of scAAV6-mediated bARKct on mechanoenergetics of normal cardiomyocytes using MCARDTM, a novel delivery platform. Specifically, we investigated bARKct's ability to increase BAR activity while preserving resting potential energy, the reverse found in HF patients. Six sheep were randomized to receive 10 super(14) genome copies of scAAV6-bARKct, using MCARDTM, which provided for dual cardiac and systemic perfusion. Western blot/qPCR analysis confirmed robust bARKct density at euthanasia (12-16 wks). Using a 5F high-fidelity LV pressure transducer catheter, CINE cardiac MRI series were generated (t = pre-gene, 4 and 8 wks - post gene delivery). Systolic-diastolic pressure-volume area (PVA), potential energy per 100 gr (PE), myocardial oxygen consumption (MVO2), maximum elastance (Emax), end arterial elastance (Ea), and heart rate (HR) were evaluated at baseline and after isoproterenol stimulation. There were no significant differences in PVA, Emax, Ea and ejection fraction (EF) in control and bARKct-transfected hearts after 4 or 8 wks post infusion. Following isoproterenol infusion, however, the increase in CO from baseline was found significant in 8 weeks 692.2c231.6 vs. Control 32.7c176.7 (p