PEDF and photoreceotor protection: a naked DNA approach. Photoreceptor cell death is an irreversible event in many blinding diseases including retinitis pigmentosa, age-related macular degeneration and retinal detachment. Pigment epithelium derived factor (PEDF), a secreted protein with both neurotrophic and anti-angiogenic properties, is made in vivo by a variety of cells in both fetal and adult animals. Within the retina, it is secreted by retinal pigment epithelial (RPE) cells into the interphotoreceptor matrix, placing it in a prime physical location to affect the underlying photoreceptor cells. We recently reported that the intravitreal injection of PEDF protected photoreceptor cells against constant light induced damage in a rat model. An alternative method for delivering a protein factor to cells and tissues is to use only the DNA which codes for the protein. Our preliminary data show that primary cell cultures of rat retinal neurons can be transfected with a naked DNA coding for enhanced green fluorescent protein under the control of the photoreceptor cell-specific promoter, mouse interphotoreceptor retinol binding protein. We have performed similar experiments expressing other reporter genes under control of other photoreceptor cell specific promoters. These experiments suggest that we are able to transfect PEDF cDNA into retinal neurons which will then express the PEDF protein. I am seeking three years of funding in this proposal to develop a novel approach using plasmid DNA cassettes expressing PEDF and apply it to the retina to prolong useful vision by delaying or preventing retinal degeneration. This novel method is actually being employed in phase I clinical trials with the injection of a naked DNA encoding the angiogenesis factor, VEGF, into the hearts of cardiac patients. In several phase II trials, direct injection of DNA has also demonstrated significant therapeutic effects in cancer patients.
The specific aims of this proposal are: I) To demonstrate the expression and protection efficiency of transfected naked plasmid DNA, encoding PEDF, in cultured rodent retinal cells. 2) To maximize the in vivo expression of naked plasmid PEDF in the eye, through the optimization of the route of administration, such as topical application, anterior chamber/intravitreal/subretinal injection. 3) To evaluate the protective efficacy of this protocol to prevent the retinal degeneration induced by light or by heredity. The proposed studies are innovative and could have a significant clinical impact as a novel therapeutic approach to delay or prevent retinal degeneration and to prolong useful vision.
