Ultrastructural Changes and Expression of PCNA and RPE65 in Sodium Iodate-Induced Acute Retinal Pigment Epithelium Degeneration Model

Abstract

Alteration in retinal pigment epithelium (RPE) results in the visual dysfunction and blindness of retinal degenerative diseases. Injection of sodium iodate (NaIO) generates degeneration of RPE. We analyzed the sequential ultrastructure and expression of proliferating cell nuclear antigen (PCNA) and retina-specific RPE65 in NaIO-induced retinal degeneration model. Adult male rats were injected 1% NaIO (50 mg/kg) and eyes were enucleated at 1, 3, 5, 7 and 14 days post-injection (DPI), fixed, and processed for histological analysis. NaIO-induced retinal degeneration was successfully established. At 1 DPI, most RPE cells were degenerated and replaced by a few proliferating RPE cells in the peripheral area. At 3 DPI, the RPE and photoreceptor out segments (POS) underwent a marked morphological change, including POS disruption, accumulation of residual bodies in RPE and POS, and hyperplasia of the RPE cell. At 5 DPI, POS showed a maximum increase in the outer segment debris and the retina showed partial detachment. These abnormal morphological changes gradually decreased by day 7. At 14 DPI, the damaged RPE and POS were partially regenerated from the peripheral to the central region. Expression of PCNA and RPE65 increased from day 3 onward. The damaged RPE showed earlier expression of PCNA and RPE65 than POS. The RPE damaged by NaIO rapidly proliferated to put down roots on Bruch's membrane from the peripheral retina and proliferation and hyperplasia of the RPE had a regular direction of progress. Therefore, NaIO-induced acute changes in retina mimic the patho-morphologic features of RPE-related diseases.

Sodium iodate-induced retina degeneration observed in non-separate sclerochoroid/retina pigment epithelium/retina whole mounts

“…RPE65-positive cells were rarely observed even at ONL, PR layer ( Figure 4B , arrow heads), and the inward moving RPE65-possitive cells were not stained by phalloidin. The morphology of intra-retinal migrating RPE cells was also not epithelium, suggesting an epithelial to mesenchymal transition of RPE cells, similar to a report from another SI-induced retina damage ( 13 ). Further, activated RPE migration has been reported in human AMD as an early AMD phenotype ( 16 , 17 ) and in rat SI-damaged retina ( 13 ).…”

“…The morphology of intra-retinal migrating RPE cells was also not epithelium, suggesting an epithelial to mesenchymal transition of RPE cells, similar to a report from another SI-induced retina damage ( 13 ). Further, activated RPE migration has been reported in human AMD as an early AMD phenotype ( 16 , 17 ) and in rat SI-damaged retina ( 13 ).…”

“…In damaged RPE layer, RPE65 expression dramatically disappeared, only occasionally were migrating ectopic RPE cells that maintained RPE65 expression still visible. The RPE cells that migrated intraretinally in this and previous SI-AMD model studies ( 13 ) might represent the clinically observed RPE inward movement at early and intermediate AMD stages before GA ( 16 , 17 ). Rosette formation, a feature of retinal degeneration induced by SI-injection has also been observed in human cases of RP and retinal detachment ( 19 – 21 ).…”

“…We especially aimed to clarify whether SI-induced the formation of outer nuclear layer (ONL) rosettes/folds in mice. Previously, these rosettes/folds were reported in rats ( 6 , 13 , 14 ), but still they had not yet been visualized in mice. In this study, we confirmed the formation of ONL folds in Sprague-Dawley (SD) rats, and both C57BL/6J and BALB/C mice.…”

A Novel HDL-Mimetic Peptide HM-10/10 Protects RPE and Photoreceptors in Murine Models of Retinal Degeneration

“…We and others have shown that the RPE damage results from increased ROS levels both in vitro and in vivo [10,31,32,33]. Several oxidative stress regulatory pathways such as Akt phosphorylation, PTEN, Nrf2, and mTOR have been shown to be involved [32,34,35]. The mechanism of cell death in RPE with NaIO3 is through apoptotic pathways although necroptosis has also been reported [36].…”