ADENOVIRUS-MEDIATED IN-VIVO GENE-TRANSFER IN A RABBIT MODEL OF ALLOGRAFT VASCULOPATHY

Background: The long-term success of heart transplantation continues t o be in jeopardy because of the development of accelerated vascular my ointimal proliferation. Transfer of genes encoding products that can m odulate the adverse consequences of phenomena that cause myointimal pr oliferation, into the allograft vessel wall, may modify these patholog ic processes. The purpose of this study was to assess the feasibility of gene transfer and to evaluate the duration of gene expression in a rabbit heterotopic aortic transplant model of allograft vasculopathy. Methods: The abdominal aortas of 32 outbred New Zealand rabbits were h arvested and cross-sectionally bisected (n = 64). Six donor and recipi ent animals were used in a preliminary study to examine neointimal pro liferation without accompanying gene transfer. Of the remaining 26 rab bits (52 allografts), one half of each allograft aorta was administere d a control solution, while the other half was incubated with a replic ation-defective, recombinant, adenoviral vector-encoding, cytomegalovi rus promoter-regulated beta-galactosidase. After a 20-minute incubatio n period, bilateral aorto-carotid transplantations were performed in 2 6 recipient rabbits. All animals received cyclosporine immunosuppressi on (10 mg/kg/day subcutaneously). The allografts were harvested at 3, 7, 10, 21, and 28 days after transplantation and assayed for beta-gala ctosidase activity. Results: Neointimal areas showed an initially slow increase for the first 10 days, followed by a rapid increase up to 21 days, and tended to plateau thereafter. Significant beta-galactosidas e was apparent in aortic sections dissected from host rabbits for all time points, except at 28 days. At the 21-day time point, the aortic s ection from one rabbit was positive, whereas the other two remained ne gative. However, the one positive section showed intense beta-galactos idase activity, suggesting variability in the experimental model. At 2 8 days, all aortic sections were negative. Conclusions: Our findings c onfirm that genes delivered by this method are expressed for the durat ion of early rapid intimal proliferation in this heterotopic rabbit mo del of aortic allograft vasculopathy. These findings suggest that this animal model can be used to assess the therapeutic potential of gene transfer at the time of vascular transplantation and may provide a nov el therapeutic approach to prevent or ameliorate the genesis of allogr aft vasculopathy.