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 physical barriers to tissue penetration by the vector particles from the vitreous. In this study we investigated the effects of enzymatic digestion of these barriers on the depth of vector penetration into the retina.
Methods: :
The green fluorescent protein (GFP)-expressing AAV2 vector was co-injected intravitreally with chondroitin ABC lyase or heparinase III at their optimal concentration. The efficacy of the virus transduction was evaluated after two weeks by visualizing fluorescence in histological cross-sections using fluorescent microscopy. We also analyzed safety of these treatments and retinal function using electroretinography.
Results: :
Both chondroitin ABC lyase and heparinase III led to a significant improvement in retinal transduction following intravitreal delivery. These enzymes both markedly improved transduction of the outer retina, including photoreceptor cells. Electroretinograms survived at much higher doses of enzymes than were needed for optimal retinal transduction.
Conclusions: :
AAV2-mediated retinal transduction is improved by co-injection of heparinase III or chondroitin ABC lyase. Improved transduction efficiency may allow intravitreal injection to become the preferred route for delivering gene therapy to both the inner and outer retina.
Keywords: adenovirus • retina • gene transfer/gene therapy