Adenovirus-mediated gene transfer of the β₂-adrenergic receptor to donor hearts enhances cardiac function

Gene transfer to modify donor heart function during transplantation has significant therapeutic implications. Recent studies by our laboratory in transgenic mice have shown that overexpression of β₂-adrenergic receptors (β₂-ARs) leads to significantly enhanced cardiac function. Tuus, we investigated the functional consequences of adenovirus-mediated gene transfer of the human β₂-AR in a rat heterotopic heart transplant model. Donor hearts received 1 ml of solution containing 1 x 10¹⁰ p.f.u. of adenovirus encoding the β₂-AR or an empty adenovirus as a control. Five days after transplantation, basal left ventricular (LV) pressure was measured using an isolated, isovolumic heart perfusion apparatus. A subset of hearts was stimulated with the β₂-AR agonist, zinterol. Treatment with the β₂-AR virus resulted in global myocardial gene transfer with a six-fold increase in mean β-AR density which corresponded to a significant increase in basal contractility (LV + dP/dt(max), control: 3152.1 ± 286 versus β₂-AR, 6250.6* ± 432.5 mmHg/s; n = 10, *P < 0.02). β₂-AR overexpressing hearts also had higher contractility after zinterol administration compared with control hearts. Our results indicate that myocardial function of the transplanted heart can be enhanced by the adenovirus-mediated delivery of β₂-ARs. Thus, genetic manipulation may offer a novel therapeutic strategy to improve donor heart function in the postoperative setting.