Erythropoietin Gene Therapy Delays Retinal Degeneration Resulting from Oxidative Stress in the Retinal Pigment Epithelium.

Manas R Biswal,Zhaoyao Wang,Alfred S Lewin,Ping Zhu,Hong Li,Yao Tong,Ryan J Paulson,Rukshana R Uddin

doi:10.3390/antiox10060842

Abstract

Erythropoietin (EPO) plays an important role in erythropoiesis by its action in blocking apoptosis of progenitor cells and protects both photoreceptors and retinal ganglion cells from induced or inherited degeneration. A modified form of EPO, EPO-R76E has attenuated erythropoietic activity but is effective in inhibiting apoptosis, oxidative stress, and inflammation in several models of retinal degeneration. In this study, we used recombinant Adeno Associated Virus (AAV) to provide long-term sustained delivery of EPO-R76E and demonstrated its effects in a mouse model of dry-AMD in which retinal degeneration is induced by oxidative stress in the retinal pigment epithelial (RPE) cells. Experimental vector AAV-EPO-R76E and control vector AAV-GFP were packaged into serotype-1 (AAV1) to enable RPE selective expression. RPE oxidative stress-mediated retinal degeneration was induced by exon specific deletion of the protective enzyme MnSOD (encoded by Sod2) by cre/lox mechanism. Experimental mice received subretinal injection of AAV-EPO-R76E in the right eye and AAV-GFP in the left eye. Western blotting of RPE/choroid protein samples from AAV-EPO-R76E injected eyes showed RPE specific EPO expression. Retinal function was monitored by electroretinography (ERG). EPO-R76E over-expression in RPE delayed the retinal degeneration as measured by light microscopy in RPE specific Sod2 knockout mice. Delivery of EPO-R76E vector can be used as a tool to prevent retinal degeneration induced by RPE oxidative stress, which is implicated as a potential cause of Age-Related Macular Degeneration.

Highlights

Age related Macular Degeneration (AMD) is one of the leading causes of permanent vision loss in people over the age of 60 [1,2]
We show that the presence of EPO-R76E slowed down the rate of functional decline and preserved retinal thickness caused by oxidative stress in the Retinal Pigment Epithelium (RPE)
Even though AAV-GFP were packaged into serotype-1 (AAV1) transduces both Müller glia and RPE following intravitreal injection, Müller glia expression is much less than the RPE [41]

Summary

Introduction

Age related Macular Degeneration (AMD) is one of the leading causes of permanent vision loss in people over the age of 60 [1,2]. Antioxidants 2021, 10, 842 macular RPE atrophy leads to photoreceptors loss, affecting vision. Dysfunction and loss of RPE in AMD are associated with several genetic and environmental factors. These factors can induce oxidative stress and inflammation that play pathological roles in RPE degeneration [3]. Many endogenous and exogenous factors can damage mitochondrial DNA (mtDNA) in the neural retina and RPE cells resulting in reactive oxygen species (ROS) overproduction [8]. High mitochondrial ROS production imbalances antioxidant and cytoprotective systems in the RPE and play a pivotal role in AMD pathogenesis [8]. Antioxidants, growth factors, and neurotrophic factors are widely proposed to protect RPE cells from oxidative damage-associated changes [9]

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