Abstract
Purpose: :
This study characterizes the cell tropism of AAV8, AAV9 and AAV10 in the mouse retina after intravitreal injection.
Methods: :
Adult mice were injected intravitreally with AAV8, AAV9, or AAV10 carrying GFP and allowed to survive for 5 weeks. Animals were then sacrificed and their eyes were surgically removed. The corneas were removed to produce eye cups that were fixed, embedded, and cryosectioned. Retinas were then imaged for GFP expression using confocal microscopy. While some cell types could be determined using location and morphology, we also performed immunocytochemistry for several cell-specific markers to help determine the cell types which were transduced. We also performed immunocytochemistry for glial fibrillary acidic protein (GFAP) to assay for potential cell stress in the transduced areas.
Results: :
AAV8 largely transduced amacrine cells and cells in the ganglion cell layer (GCL), as well as some horizontal cells, Müller cells, and putative bipolar cells. AAV9’s transduction pattern was similar to AAV8, but AAV9 was also able to efficiently transduce photoreceptors. AAV10 had the largest range of transduced cell types, including cells in the GCL, several cell types in the INL, photoreceptors, and an extremely robust transduction of horizontal cells. All AAV serotypes were able to transduce retinal pigment epithelium (RPE). Only the areas with GFP expression showed upregulated GFAP-like immunoreactivity (-LI) and the levels of GFAP-LI were stronger in regions with stronger GFP expression.
Conclusions: :
Previous work using AAV for gene delivery in the retina suggests that AAV can primarily transfect the cell layer closest the site of injection. However, this study suggests that this limitation can be overcome using different viral serotypes. AAV8 is ideal for gene delivery to the GCL, amacrine cells, and horizontal cells. AAV9 may be better suited for targeting the ONL. AAV10 is extremely efficient at transducing horizontal cells, and also very good at transducing nearly every other cell type in the retina, including RPE. The ability of AAV10 to efficiently infect every cell layer from the GCL to the RPE from an intravitreal injection supports the idea that the inability of AAV to transfect away from the point of injection is not a barrier issue, but instead one of serotype tropism. The fact that GFAP levels were increased in all transduced regions for each viral serotype, however would suggest further study is needed to assess the health of the retinal cells after infection.
Keywords: gene transfer/gene therapy