Abstract
Purpose :
Retinal ganglion cell (RGC) death occurs in many retinal diseases and increasing evidence suggests that RGCs are susceptible to injuries in a type specific manner. Glutamate excitotoxicity is thought to play a central role in the death of RGCs. However, the type specific vulnerability of RGCs to glutamate excitotoxicity has not been fully characterized. We hypothesize that the susceptibility of RGCs to glutamate excitotoxicity varies among different types of RGCs and we characterized the susceptibility of several genetically identified RGC types to glutamate excitotoxicity induced by N-methyl-D-aspartate (NMDA).
Methods :
Four transgenic mouse lines provided 4 groups (8 types) of YFP-expressing RGCs for this study. NMDA was injected intraocularly at various concentrations (1.25 – 25 mmol/L) to induce in vivo glutamate excitotoxicity. One eye of each mouse was injected with NMDA and the contralateral eye was injected with saline as a control. Both the NMDA treated and control eyes were enucleated 24 hours after injection. The retinas were isolated and fixed with 4% PFA. Fluorescent signals of YFP-expressing RGCs was enhanced by antibody staining and the retinas were flat-mounted for confocal microscopy. The number of YFP-expressing RGCs of NMDA treated eyes was measured and normalized to the control eyes to calculate the survival rate. Two-tailed Student's t-test and c2 test were used for statistical analysis.
Results :
The susceptibility of different types of RGCs to NMDA excitotoxicity varies significantly, specifically, αRGCs were the most resistant type of RGCs while BD-RGCs and J-RGCs were the most sensitive cells to NMDA excitotoxicity. The survival rates of αRGCs, W3-RGCs, BD-RGCs and J-RGCs after intraocular injection of 3.125mmol/L NMDA were 47.4±1.8% (n=5), 18.8±2.3% (n=5), 1.8±1.6% (n=6), and 2.1±1.2% (n=5), respectively (p < 0.001). In addition, RGCs were found to lose dendrites before death but the kinetics of dendritic retraction in RGCs does not directly correlate to the susceptibility of type specific RGC death.
Conclusions :
Our results are consistent with our hypothesis that the susceptibility of RGCs to glutamate excitotoxicity varies among different types of RGCs in a type specific manner.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.