Establishing a novel preclinical laser-induced model for regenerative therapies of the outer retina

Abstract

Purpose : Degenerative conditions affecting the outer retina, such as geographic atrophy (GA) and laser-induced retinal injury, involve death of photoreceptor and retinal pigmented epithelium (RPE) cells leading to vision loss. Models aimed at mimicking these conditions either do not fully reproduce the complete RPE and outer retinal atrophy (cRORA) or involve damage to additional structures of the retina such as inner retinal layers and choroid. To overcome these limitations, we have developed and characterized a novel laser-induced swine model that mimics the anatomical defects of GA and laser injury and provides a preclinical model amenable to cell and gene-based regenerative therapies.

Methods : Optical coherence tomography (OCT) guided micro-focal laser (532nm) beam was applied in 10 Yucatan pigs to induce targeted focal areas of degeneration affecting the RPE and photoreceptors. Laser damage was targeted to the visual streak which contains the highest cone density resembling the human macula. Different laser conditions were tested to define the optimal parameters. Evaluation of structural laser damage was performed weekly by fundus photography, OCT and dye angiography up to one-month post-laser and correlated with functional assessment by multifocal electroretinogram (mfERG). Cellular changes were further evaluated by immunofluorescence analysis.

Results : Optimization of laser parameters using the new laser system achieved focal areas of degeneration affecting both RPE and photoreceptor cells, with no overt abnormal changes in inner retinal layers. Following optimized laser time exposure (120 mW, 88 sec”) full ablation of the photoreceptor and RPE layers was achieved at 2 weeks post-laser, while the rest of the retinal layers were preserved and showed no obvious signs of inflammation or remodeling. Importantly, laser injury did not lead to neovascularization, significant choroidal damage, hemorrhage, anomalies of the retinal arterial vasculature, or retinal holes. Furthermore, degeneration of RPE and photoreceptor layers correlated with a decrease in mfERG response.

Conclusions : We have established and characterized a Yucatan minipig model of laser-induced retinal degeneration that mimics the anatomical defects of GA and laser injury. This model provides new opportunities for pre-clinical assessment of regenerative therapies for patients affected by GA and laser-induced retinal trauma.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.