Retrovirus-mediated gene transfer to photocoagulation-induced choroidal neovascular membranes

PURPOSE. To determine the feasibility of experimental gene transfer to laser-induced choroidal neovascular membrane (CNVM) in rats, with a retroviral vector containing the reporter construct β-galactosidase (β- gal). METHODS. Laser photocoagulation was used to induce CNVM in rats. To ascertain the duration of β-gal expression in the CNVM, 23 rats received 10 burns (75 μm, 100 mW, 0.1 seconds) in their right eyes, and β-gal expression was examined from day 3 to 4 months. In addition, 14 pigmented rats were treated with 3 photocoagulation burns in their right eyes. β-gal vector was injected into the vitreous or subretinal space 2 days later. On day 14, fluorescein angiography was performed to detect choroidal neovascularization. Then, β-gal expression in each photocoagulation-induced CNVM was examined by observing the exposed fundus of the eyes stained with the β-gal substrate X-Gal. RESULTS. β-gal expression was identified in the CNVM induced by photocoagulation from day 5 (16.2% ± 6.8% of the lesions) to 4 months (3.7% ± 2.4%). Histopathologic examination revealed β-gal- transduced macrophages and spindle-shaped cells, which amounted to 1.12% ± 0.58% (at 2 weeks) of the total cells in the CNVM. β-gal expression was restricted to the CNVM, and there was no β-gal transduction in surrounding normal retinochoroidal tissue. There was no correlation between choroidal neovascularization formation and β-gal expression. CONCLUSIONS. The feasibility of gene transduction targeted to the photocoagulation-induced CNVM was demonstrated using retroviral vectors. By transducing functional genes, this model could be useful for investigating the possibility of gene therapy to inhibit formation of the CNVM in age-related macular degeneration.