Accelerated structural and functional loss of retinal ganglion cells in a transgenic mouse model of retinopathy

Abstract

Purpose : In the course of phenotyping an aldose reductase transgenic (AR-Tg) mouse model for diabetic retinopathy, we observed a marked alteration in the pattern ERG compared to nontransgenic controls. The purpose of our study was to utilize genetic and pharmacological approaches to evaluate the impact of AR gene expression on the structure and function of retinal ganglion cells (RGC).

Methods : AR-Tg mice and nontransgenic controls on C57BL/6J background were confirmed by PCR to be negative for the Rd8 mutation of the Crb1 gene. Some animals received life-long treatment with the AR inhibitor Sorbinil (Pfizer). Retinal morphology was assessed by H&E staining of paraffin-fixed histological sections. Immunofluorescence was used for detection and quantitation of Brn3a as a marker for RGCs. Pattern electroretinogram (PERG) recordings (Jorvec) were obtained at various ages. GraphPad Prism was used to measure differences in comparison groups according to either t-test or one way ANOVA followed by Tukey's Multiple Comparison Test. A P value <0.05 was considered statistically significant. All research was conducted in compliance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research.

Results : Human AR (hAR) gene expression driven by a hybrid lens crystallin gene promoter in AR-Tg mice showed, in addition to strong immunostaining in lens, an unexpected and statistically-significant (p<0.01) increase in the number of AR-immunopositive cells in the RGC and inner nuclear layers compared to nontransgenic controls. By 18 weeks of age, and in the absence of experimentally-induced diabetes, AR-Tg mice developed marked abnormalities characterized by a thickened and vacuole-rich RGC layer as compared to wild type controls (p=0.003). Treatment of AR-Tg mice from birth with sorbinil, an AR inhibitor, reversed these changes (p=0.003). Serial pattern ERG (PERG) recordings from age 7 to 35 weeks showed a gradual loss of ganglion cell amplitude in AR-Tg mice (>60% reduction by age 24 weeks) that was substantially delayed (50% rescue) by sorbinil treatment. By 35 weeks of age, the abundance of Brn3a-positive RGC decreased by 58% in AR-Tg mice (p=0.017). Sorbinil treatment essentially prevented the loss of Brn3a-positive RGC in AR-Tg mice.

Conclusions : These results point to increased AR gene expression as a risk factor for RGC loss even in the absence of diabetes.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.