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Shihui Liu, Toshihiko Matsuo, Osamu Hosoya, Tetsuya Uchida; Apoptosis reduction by a photoelectric dye used for Okayama University-type retinal prosthesis (OURePTM). Invest. Ophthalmol. Vis. Sci. 2016;57(12):3725.
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© ARVO (1962-2015); The Authors (2016-present)
We previously demonstrated that the photoelectric dye-coupled polyethylene film (OURePTM), which was implanted in subretinal space of Royal College of Surgeons (RCS) rat’s eyes, prevented retinal neurons from apoptotic death. In addition, the photoelectric dye was proven safe in several biological tests for cytotoxicity and for systemic and immunological toxicities. In this study, we verified whether the photoelectric dye, in itself, would protect retinal neurons from apoptosis using RCS rats, a model of retinitis pigmentosa.
Twenty RCS rats at 4 weeks of age were randomly assigned to 5 groups, with each group comprising 4 rats. The rats had intravitreous injection of 3 μl solution at different concentrations of the dye, a 10-fold dilution series from 0.0082 μg/ml to 82 μg/ml, in the left eyes of each group. Saline injection at the same volume served as control in the right eyes of each group. The rats were housed under a 12-hour light/dark cycle for 14 days. As an additional experiment, another group of 3 rats with dye injection at 82 μg/ml were covered with a lightproof box to keep them in 24-hour daily dark condition. Two weeks after the dye injection, rats were sacrificed. Apoptosis was detected in frozen sections of the eyes, and also stained immunohistochemically for glial fibrillary acidic protein (GFAP) and protein kinase C alpha (PKC-α). The immunreactive areas were measured by the Image J software.
The number of apoptotic cells significantly decreased in the retina of dye-injected eyes, compared with saline-injected eyes (P<0.05, two-way analysis of variance, ANOVA), under 12-hour light/dark cycle. Significant decrease of apoptotic cells was also noted in the retina of rats with dye injection, kept under 24-hour dark condition. The area immunoreactive for GFAP was significantly decreased in the retina of dye-injected eyes when compared with controls (P<0.05, two-way analysis of variance, ANOVA). No significant difference was seen in PKC-α immunostaining between the dye-injected and saline-injected eyes.
Photoelectric dye injection exerts an inhibiting effect on apoptotic death of photoreceptors in RCS rats and also suppresses GFAP-expression in the retinal Müller cell. The photoelectric dye is a promising molecule for developing new medications used for retinitis pigmentosa.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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