Induction of local photoreceptor degeneration by a subretinal injection of N-Methyl-N-nitrosourea in rats

Abstract

Purpose : Local photoreceptor degenerations are often induced in patients with age-related macular degeneration. To know the progress of the degeneration, it is important to evaluate local retinal functions. In this study, we tried to make a rat model with local photoreceptor degenerations and also developed the multifocal ERG (mfERG) system for rodents by using a ERG system that has been used for recording standard full-field ERGs to assess the progress in condition in rat retinas with local photoreceptor degenerations.

Methods : The experiments were conducted on 3-6 months-old Sprague Dawley (SD) rats. The rats were kept under cyclic light conditions (12 h on/off). Under aesthetic conditions, one microliter of N-Methyl-N-nitrosourea solution (NMU: 0.3 mg/ml) was injected by using an automatic syringe into a subretinal space on the temporal position in the eye to induce the local photoreceptor degeneration. Images of the optical coherence tomography (OCT) were taken a week after the injection. To evaluate local photoreceptor functions, the mfERG system consisting of a stimulus screen and a software working on the standard ERG system (PuREC, Mayo Corp, Japan) was newly developed.

Results : The local photoreceptor degeneration was clearly shown in the OCT image on the temporal position in the NMU-treated retina. In the same retina, the thickness of the outer nuclear layer in other area apart from the temporal position were well-preserved. There is no significant difference on the amplitudes of a- and b-wave from standard full-field ERGs between in PBS-treated and NMU-treated retina. However, some differences were detected in the results of mfERGs. The decreased responses were observed in the temporal position on the NMU-treated retina.

Conclusions : The subretinal injection of NMU induced the local photoreceptor degeneration. It is useful model to research the restoration of local vision by transplantation of iPS cells and optogenetic gene therapies but not to investigate the mechanisms of the degenerations and the protection of photoreceptor cells. We also demonstrated that our developed mfERG system was suitable for the detection of local degeneration in rodent retinas.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.