Behavior tests and immunohistochemical retinal response analyses in RCS rats with subretinal implantation of Okayama-University-type retinal prosthesis

Abstract

We have developed a photoelectric dye-coupled polyethylene film as a prototype of retinal prosthesis, named "Okayama University-type retinal prosthesis. The purposes of this study are to conduct behavior tests to assess vision in Royal College of Surgeons (RCS) rats which underwent subretinal implantation of the dye-coupled film, and are also to reveal the retinal response to the dye-coupled film by immunohistochemistry.Polyethylene films were made of polyethylene powder at refined purity, and photoelectric dyes were coupled to the film surface at higher density, compared with the prototype. The dye-coupled film or the dye-uncoupled plain film, as a control, was implanted subretinally from a scleral incision in both eyes of a RCS rat at 6 weeks of the age. Behavior tests, 2, 4, 6, and 8 weeks after the implantation, were conducted by observing head-turning or body-turning in the direction, consistent with clockwise or anticlockwise rotation of a black-and-white-striped drum around a transparent cage, housed with a rat. After the behavior tests at 8 weeks, rats' eyes were enucleated to confirm the subretinal implantation of the films and were processed for immunohistochemistry. In the behavior tests, the number of head-turning, consistent with the direction of the drum rotation, was significantly larger in RCS rats with dye-coupled film implantation, compared with rats with plain film implantation (P<0.05, 3 repeated-measure ANOVA). The number of apoptotic neurons was significantly smaller in the eyes with the dye-coupled film implantation, compared to the eyes with the plain film (P<0.05, Mann-Whitney U-test). In conclusion, subretinal implantation of the photoelectric dye-coupled films restored the vision in RCS rats and prevented the remaining retinal neurons from apoptosis.

Inner retinal preservation in rat models of retinal degeneration implanted with subretinal photovoltaic arrays

“…Previous studies show that normal retinas respond to both acute epiretinal electrical stimulation (Ray et al, 2009; Ray et al, 2011), or chronic subretinal implantation (Chow et al, 2001; Pardue et al, 2001; Tamaki et al, 2008; Yu et al, 2009) with an upregulation of GFAP expression and degenerative changes to the dendrites of rod bipolar cells. One study in which photosensitive dye-coupled film was subretinally implanted into RCS rat eyes showed preservation within the implant site of rod bipolar cell morphology via PKCα labeling (Alamusi et al, 2013), consistent with the findings we report here.…”

“…Previous studies have attempted to characterize the condition of implanted and/or electrically stimulated retinal tissue histologically and immunohistochemically (Alamusi et al, 2013; Chow et al, 2001; Pardue et al, 2001; Ray et al, 2009; Ray et al, 2011; Tamaki et al, 2008). However, many of these studies have examined the effects only of certain aspects of the treatment paradigm, such as acute electrical stimulation or biocompatibility of a prosthetic device in wild-type animals that do not exhibit degenerative pathology.…”

Visual Evoked Potential Recovery by Subretinal Implantation of Photoelectric Dye‐Coupled Thin Film Retinal Prosthesis in Monkey Eyes With Macular Degeneration

“…Photoelectric dye molecules, 2‐[2‐[4‐(dibutylamino)phenyl]ethenyl]‐3‐carboxymethylbenzothiazolium bromide (NK‐5962, Hayashibara, Inc., Okayama, Japan), were coupled to carboxyl moieties of the polyethylene film surface via ethylenediamine, as described previously 16, 18, 26. The dye‐coupled films were manufactured under a quality management system at a clean‐room facility in the Okayama University Incubator.…”

“…In our previous studies, we showed vision recovery in retinal dystrophic rats (RCS rats) with dye‐coupled film implantation 26, 27, 28. In this study, the dye‐coupled films were implanted by vitreous surgery in the subretinal space of monkey eyes with cobalt chloride‐induced macular degeneration.…”

Photoelectric Dye Used for Okayama University-Type Retinal Prosthesis Reduces the Apoptosis of Photoreceptor Cells

“…12,13 Our previous studies showed that OUReP could reduce neuronal apoptosis in the eyes of Royal College of Surgeons (RCS) rats. 15,16 In this study, we tested whether intravitreous injection of the photoelectric dye would rescue photoreceptor cells from the apoptosis in RCS rats. 17–19 …”