EX-VIVO ADENOVIRUS-MEDIATED GENE-TRANSFER TO THE ADULT-RAT HEART

Objective: The ability to transfer genes to adult myocardium may have therapeutic implications for cardiac transplantation. We investigated the feasibility of adenovirus-mediated transfer of marker genes LacZ a nd Luciferase, as well as the potentially therapeutic gene of the huma n beta(2)-adrenergic receptor in a rat heterotopic heart transplant mo del. Methods: Donor hearts were flushed with 10(12) total viral partic les of one of three transgenes. Hearts were harvested at various time points after transplantation. LacZ-treated hearts were assessed by his tologic staining and Luciferase-treated hearts were assayed for specif ic luminescence activity. Hearts treated with beta(2)-adrenergic recep tor underwent radioligand binding assays and immunohistochemistry with the use of an antibody specific for the human beta(2)-adrenergic rece ptor. Results: LacZ hearts revealed diffuse myocyte staining as oppose d to none within controls at 5 days. Luciferase hearts demonstrated a mean activity of 970,000 +/- 220,000 arbitrary light units versus 500 +/- 200 for the controls (p = 0.001). Total beta(2)-adrenergic recepto r densities (fmol/mg membrane protein) for hearts that received the be ta(2)-adrenergic receptor transgene at 3, 5, 7, 10, and 14 days after infection were as follows: right ventricle, 488.5 +/- 126.8, 519.4 +/- 81.8, 477.1 +/- 51.8,* 183.0 +/- 6.5,* and 82.7 +/- 19.1; left ventr icle, 511.0 +/- 167.6, 1206.4 +/- 321.8, 525.3 +/- 188.7, 183.5 +/- 1 8.6, and 75.9 +/- 15.2 (*p < 0.05 vs control value of 75.6 +/- 6.4). Immunohistochemical analysis revealed diffuse staining of varying inte nsity within myocardial sarcolemmal membranes. Conclusions: We conclud e that global overexpression of different transgenes is possible durin g cardiac transplantation and, ultimately, adenovirus-mediated gene tr ansfer map provide a unique opportunity for genetic manipulation of th e donor organ, potentially enhancing its function.