Abstract
Purpose: :
Due to its high ocular transduction and low immune clearance properties, Adeno-associated virus serotype-9 (AAV-9) has been considered as one of the promising delivery vectors for retinal disease gene therapy. We recently demonstrated that AAV-9 efficiently transduced the retinal outer plexiform layer (OPL). Here, we explored the cellular pathway(s) involved in AAV-9 OPL transduction.
Methods: :
One microliter of AAV-9 vectors carrying the enhanced green fluorescent protein (eGFP) gene (AAV-9.CMV.eGFP, 1x10e10 viral genome particles) were administered subretinally to four young (16-day-old) and four adult (3-month-old) mice. Four weeks after subretinal injection, we examined eGFP expression in the retina. CtBP2 (C-terminal binding protein 2) and PSD95 (postsynaptic density protein) were used as markers of photoreceptor terminals. Protein kinase C alpha (PKCalpha) and mGluR6 (metabotropic glutamate receptor subtype 6) were used to label the rod bipolar cells and the dendrites of ON bipolar cells, respectively. Calbindin was used as a marker of horizontal cell. Nuclei were revealed with 4’,6¬diamidino-2-phenylindole dihydrocholoride (DAPI).
Results: :
In both young and adult mice, we observed eGFP expression in the retinal pigment epithelia, outer nuclear layer, OPL, Mueller cells in the inner nuclear layer, inner plexiform layer and ganglion cell layer. We also observed robust expression in the photoreceptors (including the inner and outer segments). Interestingly, eGFP co-localized with CtBP2 and PSD95, the markers for the distal region of the OPL but not with calbindin, the marker for the proximal region the OPL.
Conclusions: :
In this study, we demonstrated robust photoreceptor and OPL transduction by AAV-9. Furthermore, our results suggest that OPL transduction is very likely mediated by the photoreceptors rather than the inner nuclear layer neurons.
Keywords: gene transfer/gene therapy • photoreceptors • synapse