Subretinal Saline Protects the Neuroretina From Thermic Damage During Laser Induction of Experimental Choroidal Neovascularization in Pigs

Abstract

Purpose The purpose of this study was to develop a porcine model for photocoagulation induced choroidal neovascularization (CNV) with high success rate and minimal thermic damage to the neuroretina. Methods Experimental CNV was induced by laser photocoagulation in both eyes of 16 domestic pigs. In the left eyes, photocoagulation was preceded by subretinal injection of saline to protect the neuroretina from thermic damage, whereas the right eyes were treated with photocoagulation only. The development of the CNV after 3, 7, 14, 28, and 42 days was evaluated by optical coherence tomography (OCT) scanning, fluorescein angiography, and OCT angiography, and by histology after enucleation. Results From day 7 after the photocoagulation, OCT showed subretinal density in all lesions of 14 alive animals, and either fluorescein or OCT angiography confirmed CNV formation in 11 of 14 of the eyes that had received photocoagulation alone and those in which photocoagulation had been preceded by subretinal injection of saline. In all cases pretreated with subretinal saline, the neuroretina was protected from immediate thermic damage. The formation of CNVs were confirmed by histology. For both groups, the largest lesions were observed within 14 days after photocoagulation. Conclusions Injection of subretinal saline can protect the retina from thermic damage induced by retinal photocoagulation without reducing the success rate in producing experimental CNV. The effect of interventional studies aimed at reducing photocoagulation induced experimental CNV in pigs can be evaluated within 2 weeks after photocoagulation. Translational Relevance This model provides a fundament to develop and evaluate novel treatment methods for neovascular retinal diseases.

Animal Models of Choroidal Neovascularization: A Systematic Review

“…As emphasized by Ryan in 1979, 28 the laser-induced animal model of CNV in rhesus monkeys resembles an acute, traumatic-inflammatory process with substantial neuroretinal damage rather than a chronic, progressive, age-related degeneration. 29 , 30 Such biological differences between the model and modeled disease warrant cautious extrapolation of, for example, evidence of inflammatory processes.…”

Subretinal AAV delivery of RNAi-therapeutics targeting VEGFA reduces choroidal neovascularization in a large animal model

“…FI and OCT images at baseline revealed normal retinas for all animals with discrete variations of retinal pigmentation observed among the experimental animals similar to our previous study. 40 However, from D14 and onwards most eyes injected with scAAV2.8/GFP displayed pigmentary changes on FI (D14 = 43%; D28 = 80%; D42 = 100% of the eyes) ( Figures 5 A and 5B). Additional observations on OCT scans included the loss of distinct layering of the RPE/PR complex (D14 = 29%; D28 = 100%; D42 = 100% of the eyes), hyperreflective irregularities adjacent to the RPE (D28 = 80%; D42 = 100% of the eyes), and a single case (P1, OS, D14) of sparse cells in the vitreous body ( Figures 4 B, 5 A, 5B, and S5 ; Table S1 ).…”

“…For this purpose the construct was packaged in a serotype 8 capsid with a single-stranded genome configuration (ssAAV2.8/13-12) and tested in a porcine laser-induced CNV model. 40 To increase efficacy and to account for a potentially weaker transgene expression by the VMD2 promotor compared with the CMV promotor 42 a slightly higher dose (3 × 10 10 vg/eye) than in the delivery study was chosen. On D0, 10 animals received a subretinal injection of ssAAV2.8/13-12 in one eye and an irrelevant, non-targeting control (ssAAV2.8/S1-S2) in the other eye ( Figure 6 A).…”

“…The therapeutic potential of VEGFA -targeting miR-agshRNA was evaluated in a porcine laser-induced CNV model that has been experimentally validated. 40 , 43 Laser perforation of Bruch’s membrane is an established method of CNV induction that has been amply used to evaluate anti-angiogenic therapies. 43 Most studies have been performed in rodents.…”

“…In addition, the unpaired analysis not accounting for inter-eye correlation is expected to reduce statistical power. 45 As alternative strategies, optimization via another laser system 28 or protection of the neuroretina by subretinal injection of saline before laser application 40 could be explored.…”