Gene delivery of calreticulin anti-angiogenic domain attenuates the development of choroidal neovascularization in rats

Choroidal neovascularization (CNV) is a common pathological feature in neovascular age-related macular degeneration, which is the leading cause of vision loss among elderly populations in developed countries. This study evaluated the effect of a novel endogenous inhibitor of angiogenesis, calreticulin anti-angiogenic domain (CAD), subconjunctivally delivered by an adenoviral vector (Ad-CAD) in a rat model of laser-induced CNV. CAD was expressed in Ad-CAD-infected cells and inhibited the angiogenic activity in human umbilical vein endothelial cells in vitro. CAD expression was also found in various ocular tissues after in vivo subconjunctival Ad-CAD injection. Via bioluminescence imaging it is shown that a single subconjunctival injection of Ad-luciferase induced the expression of the transgene in the injected eyes within 24 h, which lasted for at least 112 days. Forty-two days after subconjunctival injection of Ad-CAD, retinal structure and function were unaffected, as measured using optical coherence tomography and electroretinography, respectively. After laser injury, subconjunctival Ad-CAD gene delivery significantly inhibited CNV lesions as measured via choroid flat-mounts (51% reduction at 21 days; p < 0.001), as well as by fundus fluorescein angiography (19.3%, 28.2%, 31%, and 27.5% reductions at days 21, 28, 35, and 42, respectively; p < 0.05) in rats. The data suggest that subconjunctival Ad-CAD gene therapy could effectively inhibit laser-induced CNV and might be an attractive therapeutic approach for the management of choroidal neovascularization.