Regeneration of the zebrafish retinal pigment epithelium after widespread genetic ablation.

Nicholas J Hanovice,Edward A Burton,Kira L Lathrop,Lyndsay L Leach,Enhua Shao,Ana E Gabriel,Jeffrey M Gross,Dwight Romanovicz,Ross Collery,Kayleigh Slater,Brian A Link

doi:10.1371/journal.pgen.1007939

Abstract

The retinal pigment epithelium (RPE) is a specialized monolayer of pigmented cells within the eye that is critical for maintaining visual system function. Diseases affecting the RPE have dire consequences for vision, and the most prevalent of these is atrophic (dry) age-related macular degeneration (AMD), which is thought to result from RPE dysfunction and degeneration. An intriguing possibility for treating RPE degenerative diseases like atrophic AMD is the stimulation of endogenous RPE regeneration; however, very little is known about the mechanisms driving successful RPE regeneration in vivo. Here, we developed a zebrafish transgenic model (rpe65a:nfsB-eGFP) that enabled ablation of large swathes of mature RPE. RPE ablation resulted in rapid RPE degeneration, as well as degeneration of Bruch’s membrane and underlying photoreceptors. Using this model, we demonstrate for the first time that zebrafish are capable of regenerating a functional RPE monolayer after RPE ablation. Regenerated RPE cells first appear at the periphery of the RPE, and regeneration proceeds in a peripheral-to-central fashion. RPE ablation elicits a robust proliferative response in the remaining RPE. Subsequently, proliferative cells move into the injury site and differentiate into RPE. BrdU incorporation assays demonstrate that the regenerated RPE is likely derived from remaining peripheral RPE cells. Pharmacological disruption using IWR-1, a Wnt signaling antagonist, significantly reduces cell proliferation in the RPE and impairs overall RPE recovery. These data demonstrate that the zebrafish RPE possesses a robust capacity for regeneration and highlight a potential mechanism through which endogenous RPE regenerate in vivo.

Highlights

The retinal pigment epithelium (RPE) is a polarized monolayer of pigment-containing cells that separates the retina from the choroid and performs many critical functions for vision
Diseases resulting in retinal pigment epithelium (RPE) degeneration are among the leading causes of blindness worldwide, and no therapy exists that can replace RPE or restore lost vision
One intriguing possibility is the development of therapies focused on stimulating endogenous RPE regeneration

Summary

Introduction

The RPE is a polarized monolayer of pigment-containing cells that separates the retina from the choroid and performs many critical functions for vision. AMD is commonly divided into two types: atrophic (dry) and exudative (wet). In the early stages of atrophic AMD, RPE cells in the parafovea become dysfunctional and progressively degenerate, and this is thought to result in death of parafoveal rods [7,8,9]. RPE dysfunction and degeneration spread to the fovea, resulting in loss of cone photoreceptors, and loss of high-acuity vision [10,11,12]. Exudative AMD occurs in a subset of atrophic AMD cases when choroidal vasculature invades the retina [11,13]

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Conclusion