Abstract
Purpose :
Patients suffering from retinal degenerative diseases, e.g. retinitis pigmentosa (RP), can regain visual functionality by prostheses. Electrical stimulation of retinal cells is conducted by microelectrode arrays. In order to test retinal implants and establish surgical procedures, large-eye animal models mimicking the properties of RP are required. Here, we describe experiments performed to establish a unilateral UV-induced photoreceptor degeneration model in the mouse. Our results will be used to transfer the method to the large-eye rabbit model.
Methods :
Left eyes of female C57Bl/6J mice (PW 8-12), were irradiated with a UV-LED at 370 nm for 3-10 minutes. In a first group of 10 animals, dosages between 2.8 and 9.3 J/cm2 were tested. A lens was inserted between LED and cornea to optimize radiation conditions, illuminating about one third of the retina. Weekly examinations post irradiation were performed, including macroscopy, optical coherence tomography (OCT) and full field electroretinography (ERG). Four weeks after irradiation the animals were sacrificed and eyes prepared for hematoxylin-eosin (HE) staining. Right eyes served as control.
Results :
Results from the first group showed that a dosage between 6.5 and 9.3 J/cm2 was needed to achieve retinal degeneration. Among retinal layers, only photoreceptors were directly affected by the irradiation, as revealed by HE staining. In OCT measurements a decreased thickness was visible at week one post irradiation, dropping to 51 % (SD 4 %) at week four. Also, in ERG recordings the a-wave decreased to 70 % (SD 13 %), while the b-wave fell to 58 % (SD 13 %). In several cases a neovascularization of the cornea was observed which occurred independently of UV-dosage. It was treated with anti-inflammatory and antibiotic eye ointment.
Conclusions :
UV-irradiation is a suitable method to induce photoreceptor degeneration in the mouse retina, while leaving the other retinal layers intact. In future experiments we will employ immunohistochemistry to investigate whether inner retinal cells are affected by illumination. This model is easy and safe to handle. The restriction that only a third of the retina can be irradiated is compensated by localization of the degenerated area using OCT scans. After the study in mice is completed, the approach will be transferred to the large-eye rabbit model enabling testing and optimization of newly developed retinal devices.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.