Analysis of the Inner Retina following Implantation of a Subretinal Artificial Silicon Retina in RCS Rats

Abstract

Abstract: : Purpose: An artificial silicon retina (ASR) implanted in the subretinal space may provide a possible treatment for photoreceptor degeneration by activating inner retinal circuitry to generate a visual signal. Here we evaluate retinal morphology in an animal model of photoreceptor degeneration, the RCS rat, after ASR implantation to determine if subretinal electrical stimulation has any beneficial or deleterious effects on inner retinal cell layers or bipolar cell populations. Methods: The ASR was implanted into the subretinal space of RCS rats at 3-4 weeks of age. In each rat, one eye was implanted with an active implant while the other eye served as an unoperated control, underwent a sham procedure or was implanted with an inactive ASR. At 8 to 52 weeks post-implantation, the eyes were enucleated and fixed in mixed aldehydes. Eye cups were processed into plastic and sectioned vertically at 0.5µm or frozen and processed for immunohistochemistry using antibodies for PKC and recoverin. For evaluation of retinal thickness, digital images of plastic sections were taken and each retinal layer measured at ten locations across the retina using an image analysis program. Results: The thickness of the ganglion cell layer, inner nuclear layer and inner plexiform layer were similiar between eyes implanted with active implants vs. inactive implants, sham operated or unoperated eyes. Antibodies to PKC and recoverin labeled rod and cone bipolar cells, respectively, with a similar distribution in all eyes. Conclusions: The presence of an electrically active ASR within the subretinal space of RCS rats causes no apparent loss of inner retinal cells. In addition, ASR stimulation does not appear to induce reorganization of inner retinal circuitry.

Keywords: microscopy: light/fluorescence/immunohistochem • retina: proximal(bipolar, amacrine, and gangli • animal model