Abstract
Purpose:
The application of viruses as carriers to deliver genes to eye tissue was successful, though unsafe. A safer, non-viral, biocompatible lipid-based nanoparticle to treat blinding eye diseases has never been tested in vivo. In this study, we created an artificial virus using a nanoparticle, liposome-protamine-DNA complex (LPD), to deliver a functional gene with sustained expression to eye tissues in a cell-specific manner for the treatment of eye disease.<br />
Methods:
Liposomes were prepared by standard liposome technology and mixed with DNA, protamine, and nuclear localization signaling (NLS) peptide to generate lipid-protamine-DNA complex (LPD). We used LPD-complexed with GFP-reporter to monitor the in vivo gene transduction. Chicken Rpe65 cDNA or control plasmid DNA was complexed with LPD and injected into Rpe65 knockout mice. Cone function was assessed by electroretinography (ERG). Cone density was measured by lectin cytochemical analysis using peanut agglutinin (PNA). Localization of Rpe65 was examined by immunohistochemistry.<br />
Results:
Our studies suggest that LPD can deliver GFP-reporter in vivo. Rpe65 protein is the key enzyme in regulating the availability of photochemicals. A deficiency of this gene results in blinding eye disease. Rpe65 mice do not show any ERG, due to the absence of chromophore regeneration. These mice also exhibit progressive cone cell loss by four weeks of age. LPD-Rpe65-gene delivery to Rpe65 knockout mice produced vision improvements. Our results indicated a complete loss of cones in Rpe65 knockout mice injected with control DNA, and preservation of cones in LPD-Rpe65 gene delivered Rpe65 knockout mice, comparable to wild-type controls. The immunohistochemistry results showed that Rpe65 expression was restricted to the retinal pigment epithelium layer in Rpe65-injected Rpe65 knockout mice.<br />
Conclusions:
Our results demonstrate, for the first time, that LPD promotes efficient delivery in a cell-specific manner, and delivers a long-term expression of Rpe65 gene to mice lacking Rpe65 protein, leading to in vivo correction of blindness. Thus, LPD nanoparticles could provide a promising, efficient, non-viral method of gene delivery with clinical applications in eye disease treatment.<br />