Abstract
Purpose: :
At present only limited retinal transduction can be achieved following intravitreal delivery of AAV vectors. We hypothesized that the vitreous, inner limiting lamina, retinal extracellular matrix and cell surface proteoglycans pose anatomical barriers to tissue penetration by the vector particles. In this study we investigated the effects of disruption of these barriers using glycosidic enzymes.
Methods: :
The green fluorescent protein (GFP)-expressing AAV2 vector was co-injected intravitreally with hyaluronan lyase, chondroitin ABC lyase or heparinase III used at increasing concentrations. The efficacy of the virus transduction was evaluated after two weeks by visualizing fluorescence in retina flat mounts using confocal microscopy followed by ImageJ software. We also analyzed retinal function using electroretinography.
Results: :
Chondroitin ABC lyase and heparinase III led to a significant improvement in retinal transduction, with hyaluronan lyase producing a lesser effect. These enzymes markedly improved both the proportion of inner retinal cells transduced and the depth of AAV2 penetration into the retina. Electroretinograms survived at much higher doses of enzymes than were needed for optimal retinal transduction.
Conclusions: :
When AAV2 is delivered into the vitreous in conjunction with heparinase III or chondroitin ABC lyase retinal transduction efficiency is dramatically improved. This treatment strategy has potential advantages over current gene delivery by subretinal injections, which can be associated with severe complications.
Keywords: gene transfer/gene therapy • adenovirus • retina