Introducing a new model for studying retinal detachment/replacement: an electron microscopic study

Retinal detachment, separation of the neurosensory retina from the underlying retinal pigment epithelium, is a sight threatening condition that is considered one of the few ocular emergencies. In the current experiment, electron microscopic study of the retina of toad buffo marienes was done to evaluate the morphological changes due to retinal detachment and the possibility of spontaneous reattachment and to confirm the possibility of the use of the toad retina as a model for retinal detachment studies in mammals. The study focused on the retinal pigment epithelium and the outer segment of the neural retina. The retinal pigment epithelium of the control retina expressed the main features of the cells including the apical processes, the melanin granules and the phagosomes. The apical processes were firmly interdigitating with the neural retina outer segment and the melanin granules appear near the apical part of the cells. The outer segment of the neural retina appeared with parallel plates of flattened membranous desks. At 30 minutes after retinal detachment, a subretinal space appeared and the interdigitation between the processes of retinal pigment epithelium and the outer segment of the neural retina was lost. Two hours after retinal detachment, no continuity appeared between the retinal pigment epithelium and the outer segment of the neural retina. At 5 and 10 hours after retinal detachment, the interdigitation between the retinal pigment epithelium and the outer segment of the neural retina was restored. The tight junctions between different neural retina outer segments appeared to be not affected. In the current experiment, a simple model for experimental study of retinal pigment epithelium, neural retina and retinal detachment has been introduced. Due to the ultrastructural similarities of toad retinal pigment epithelium with that of mammals, the toad can serve as an excellent model for the study of retinal detachment/reattachment and their cellular and molecular mechanisms

Introducing a new model for studying retinal detachement/replacement: a light microscopy and electrophysiological study

The toad's [Bufo maranus] retinal pigment epithelium [RPE] has been used in many studies as a model for understanding its role and interaction with the neural retina. In the current study, the toad's retina has been used to establish a new in vitro model of experimental retinal detachment [RD] and replacement. The toad was chosen according to a previous study of our research group showed that the toad RPE is similar to the mammalian RPE. In this report, light microscopy was used to characterize the morphologic changes that occur in the RPE and neural retina following RD/replacement and to correlate these findings with recovery of electrophysiological function. The neural retina was completely detached from the RPE in vitro and then replaced. At various times after replacement, neural retina-RPE tissues were processed for light microscopy. At 30 min. after replacement, the subretinal space was greatly expanded, and the apical processes that normally ensheath the outer segments of neural retina were short and no longer contacted the outer segments of neural retina. The RPE was swollen, contained many vacuoles and the apical surface was rounded. By 2 hours after replacement, the subretinal space was significantly resorbed and contained many shredded neural retina outer segments; RPE cells were still, although less, swollen. During the next 5-10 hours, shredded neural retina outer segment in the subretinal space appeared decreased. RPE cells regained their normal size and interdigitation of apical processes and neural retina outer segment were observed. In conclusion, these results demonstrate the re-establishment of morphological interactions between the RPE and neural retina within hours following RD/replacement. Morphological recovery coincides with recovery of electrophysiological parameters. This is a good model to investigate the retinal pigment epithelium [RPE] and neural retina mechanisms involved in retinal adhesion and recovery from retinal detachment and is easier to be applied than previously described models