Abstract
Purpose :
Previously we demonstrated that transient transcorneal electrical stimulation is neuroprotective for retinal neurons in vivo. Therefore it is possible that chronic electrical stimulation by an implantable device such as a retinal prosthesis exerts neuroprotection. In this study we investigated the effect of chronic trans-scleral electrical stimulation (ES) on the survival of axotomized retinal ganglion cells (RGCs) in vivo.
Methods :
Adult Long-Evans rats were used. The left optic nerve (ON) was transected 3 mm from the posterior eye pole. Subsequently, a small sponge soaked in 2% Fluorogold (FG), a fluorescent tracer for retrograde labeling of RGCs was placed on the ON stump.
Ring electrodes with a diameter of 1.5 mm were sutured onto the sclera at the upper equator of the eye. The electrodes were connected to an implantable pulse generator unit (ISE1000SA; UNIMEC,Tokyo, Japan). The electrical stimuli consisted of 20 Hz, anodic first biphasic rectangular current pulses (50 µA, 1ms/phase ) that were delivered from the generator for a week. Seven days after ON transection, Only the left (transected) eye was enucleated, then the retinas were flat-mounted. The surviving FG-labeled RGCs were counted in 12 areas covering the whole retina under a fluorescent microscope, and the densities of RGCs were determined. The density of RGCs in the retina one day after ON cut was set as a control. In sham stimulation group, electrodes were sutured, but were not connected to the generator.
Results :
Seven days after ON transection with sham stimulation, the mean RGC density (1246±142 cells/mm2 (mean ± SD), n = 8) significantly decreased to 52.1 % of control retinas (2390±194 cells/mm2, n = 8). ES exerted the neuroprotective effect on injured RGCs. the mean RGC densities were 86.7% of control value (2073±149 cells/mm2 , n = 8 ; P < 0.001 vs sham).
Conclusions :
Chronic ES promotes the survival of axotomized RGCs in adult rats. These results propose the beneficial information for the clinical application of chronic ES such as retinal prosthesis to prevent or delay the degeneration of retinal neurons.
This is a 2020 ARVO Annual Meeting abstract.