Preservation of myocardial function after adenoviral gene transfer in isolated myocardium

Adenoviral gene transfer to the heart represents a promising model for structure-function analyses. Rabbit hearts were subjected to an ex vivo perfusion protocol that achieves gene transfer in >90% of cardiac myocytes. Contractile function of isolated myocardial preparations of these hearts was then observed for 2 days in a recently developed trabecula culture system. In sham-infected hearts, the initial developed force (F(init)) (15.6 ± 3.7 mN/mm²; n = 12) did not change significantly after 48 h (17.0 ± 1.9 mN/mm²; P = 0.46). In adenovirus-infected preparations, F(init) (14.3 ± 1.8 mN/mm²; n = 21) did not significantly differ from the control (P = 0.75) and was unchanged after 48 h (15.3 ± 2.5 mN/mm²; P = 0.93). After 2 days of continuous contractions, we observed homogenous and high-level expression of the reporter genes LacZ coding for β-galactosidase and Luc coding for firefly luciferase. Luciferase activity increased more than 2,500-fold from background levels of 8.7 x 10³ ± 5.0 x 10³ relative light units (RLU)/mg protein (from hearts transfected with promotorless adenovirus with luciferase transgene construct AdNULLLuc, n = 5) to 23.4 x 10⁶ ± 11.1 x 10⁶ RLU/mg protein (from hearts tranfected with adenovirus with Rous sarcoma virus promotor and luciferase transgene construct AdRSVLuc, n = 5) in infected myocardial preparations (P <0.005). Our results demonstrate a new ex vivo approach to achieve homogenous and high-level expression of recombinant adenoviral genes in contracting myocardium without adverse functional effects.