Abstract
Purpose: :
To investigate age-related differences of recovery of visual function in Royal College of Surgeons (RCS) rats which received Channelrhodopsin-2 (ChR2) gene transfer.
Methods: :
An adeno-associated virus vector encoding ChR2 fused with Venus (AAV-ChR2V) was intravitreously injected into young (6 months-old) or aged RCS (10 months-old) rats. All experiments were performed after 4 months of injection. To estimate the transduction efficiencies, ChR2V-expressing cells and retrograde labeled retinal ganglion cells (RGCs) were counted. Visually evoked potentials (VEPs) were periodically recorded. The function of retinal cells was studied on frozen sections by immunostainigs of Glial fibrillary acidic protein (GFAP).
Results: :
ChR2V was expressed in the RGCs of both groups, young- and aged- rats, and there was no significant difference in the transduction efficiency between groups. However, the number of RGCs in aged RCS rats was significantly less than that in young RCS rats. In addition, the amplitudes and latencies from young RCS rats were higher and shorter, respectively, than those from aged RCS rats. High immunoreactivity of GFAP was observed in no-treated RCS rats and their immunoreactivity was strengthened according to the age, whereas immunoreactivity in ChR2V-treated RCS rats was weaker than those of no-treated rats. There were differences in expression profiles between no-treated and ChR2V-treated RCS rats. In no-treated RCS rats, GFAP immuno-reactivity was observed in INL and the IPL in addition to the staining of the ILM. On the other hand, in the ChR2-treated RCS, the immunoreactivity was restricted in ILM.
Conclusions: :
ChR2 transduction produced photosensitive RGCs in both young and aged rats. Histological studies showed that expression of ChR2 had some protective effects on inner retinal neurons. These results demonstrated that the degree of recovery depended on the age at the time of transduction.
Keywords: gene transfer/gene therapy • photoreceptors • regeneration