Neuro-protective effect of physical exercise on retinal ganglion cells in acute intraocular pressure elevation models in rats

Abstract

PURPOSE: The neuro-protective effect of physical exercise has been found in a number of neurodegenerative diseases; however, limited evidences were present for glaucoma models with elevated intraocular pressure (IOP). The purpose of this study was to evaluate the potential beneficial effect of physical exercise in promoting retinal ganglion cell (RGC) survival in acute IOP elevation models in rats. METHODS: Sprague Dawley Rats of 4-5 weeks old were divided into exercise group(n=5) and control group(n=8). In exercise group, the rats were housed separately in cage with a free running wheel while in control group the rats were housed separately in the same cage without running wheel system. The IOP was elevated to 140mmHg for 75 minutes after 30 days of housing in right eyes of all rats. On day 37, RGC was retrogradely labeled by fluorogold (FG). The rats were sacrificed on day 44 for RGCs counting. One-way ANOVA was used to analyze the data by Prism 6; GraphPad Software, Inc, CA. p<0.05 was considered as significant difference. RESULTS: Compared to the untreated eyes, the RGC densities in IOPelevated eyes were reduced by 19.68% and 19.25% in the exercise and control group respectively (p <0.05). However, the density of RGC in exercise group (1754±326/mm2) was not higher than that in control group (2022±240/mm2) although no significant difference was found(p>0.05). CONCLUSIONS: No improvement in RGC density to suggest a potential neuro-protective effect after IOP elevation was demonstrated in rats which had undergone physical exercise in our current study. More laboratory tests including electrophysiology, histologic examination, apoptosis assay by TUNEL, immunohistochemistry and western blot analysis for apoptosis-related proteins would be required to verify such result because of presence of potential confounding factors.