Abstract
Purpose: :
The retinas of the recently identified nm3342 mutant mouse spontaneously detach similarly to that observed in human central serous retinopathy (CSR; Chang et al., ARVO e-abstract #5225, 2008). The purpose of this study was to identify structural and/or protein changes at the interface between the retina and RPE that could account for the loss of retinal adhesion.
Methods: :
Wild-type (C57BL/6J) and nm3342 mice were euthanized on P30, 60, 90 and 120 and the eyes prepared for light, electron and confocal microscopy. Probes included the lectin peanut agglutinin (PNA), as well as antibodies to rod and cone opsin, the RPE proteins ezrin (cytoskeletal protein in the apical microvilli) and aquaporin 1 (integral membrane fluid transport protein), and the mitochondrial protein cytochrome oxidase (COX). Confocal microscopy was used to image whole mount preparations and 100-micron thick vibratome sections.
Results: :
Light and electron microscopy revealed small shallow detachments beginning at P30 that appeared to increase in size and height over time. Photoreceptor outer segments remained relatively long and intact even in areas of detachment. Numerous macrophages were observed in the subretinal space in both attached and detached areas. Confocal microscopy revealed a dramatic loss of PNA binding from the interphotoreceptor matrix (IPM) and a concomitant increase in the ONL at P30. Rod and cone opsin immunolabeling showed relatively normal patterns even in regions lacking PNA binding. RPE whole mounts revealed a dramatic but patchy loss in immunolabeling for both ezrin and aquaporin 1. Anti-COX labeling showed a large increase in number and size of mitochondria in photoreceptors and the RPE.
Conclusions: :
These data indicate significant changes in the IPM and apical surface of the RPE at the same post-natal time detachment begins; changes that may define the pathology and pathways responsible for initiating the loss of retinal adhesion. The presence of spontaneous detachment with maintenance of relatively intact outer segments, suggests that this mutation may serve as a good model for serous retinal detachment in humans.
Keywords: retinal adhesion • retinal pigment epithelium • photoreceptors