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Repeated retinal photocoagulation in monkeys for optimization of laser-induced choroidal neovascularization model.

08:00 EDT 27th March 2019 | BioPortfolio

Summary of "Repeated retinal photocoagulation in monkeys for optimization of laser-induced choroidal neovascularization model."

Laser-induced choroidal neovascularization (CNV) model in nonhuman primates has played a critical role in the development of new therapies for neovascular age-related macular degeneration. The widespread use of this model, however, has been limited by its high costs, mainly due to the lower efficiency of animal use. To address this problem, we optimized the CNV model by repeated photocoagulation in the same eye of each animal and preliminarily evaluated this model for assessment of an anti-vascular endothelial growth factor (VEGF) agent. Seven rhesus monkeys were included and divided into two groups, which were named the laser-only and laser-bevacizumab groups. Each animal underwent 3 retinal photocoagulation sessions in the same eye at 4-week intervals to induce CNV. The animals in the laser-bevacizumab group received treatment in both eyes during the first photocoagulation session. Three weeks after the first laser treatment, the animals in the laser-bevacizumab group were given an intravitreal injection of bevacizumab in the repeated photocoagulation eye, while no medicine was administered to the contralateral eye. To assess the severity and development of CNV produced by each laser treatment, fluorescein angiography (FA) was performed in all animals at multiple time points. The laser lesions produced in each photocoagulation session were analysed separately using grading and densitometric methods, and CNV severity was represented by the CNV incidence and the mean integrated fluorescence intensity (MIFI), respectively. Our results showed that in the animals in the laser-only group, the average CNV incidence rates were 62.5%, 42% and 50% at 2 weeks after each laser treatment, and the average MIFI values (x10) were 3.83 ± 2.36, 2.66 ± 1.42 and 2.52 ± 0.18, respectively. No significant differences were found among treatments. Meanwhile, the time course of CNV development in each animal was generally the same after each photocoagulation session. In the laser-bevacizumab group, however, the average CNV incidence rates of each laser treatment were 50%, 0 and 37.5%, respectively, and the average MIFI values were 3.79 ± 0.47, 1.09 ± 0.35 and 2.37 ± 1.35, respectively. The differences between treatments 1 and 2 were statistically significant. Meanwhile, the CNVs induced by laser treatment 1 were reduced after bevacizumab administration. The average CNV incidence decreased from 50% at week 3-4.2% at week 4, and the average MIFI decreased from 4.62 ± 1.15 to 1.76 ± 0.81, both of which were statistically significant. However, the CNVs of treatments 2 and 3 did not show any significant changes over time. Additionally, the CNVs induced in both eyes of these animals during the first laser treatment showed no significant differences. Our study demonstrated that repeated retinal photocoagulation in the monkey eye produces relatively consistent CNVs, which can be used to assess the efficacies of anti-angiogenic agents more efficiently.

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This article was published in the following journal.

Name: Experimental eye research
ISSN: 1096-0007
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Medical and Biotech [MESH] Definitions

The coagulation of tissue by an intense beam of light, including laser (LASER COAGULATION). In the eye it is used in the treatment of retinal detachments, retinal holes, aneurysms, hemorrhages, and malignant and benign neoplasms. (Dictionary of Visual Science, 3d ed)

A technique utilizing a laser coupled to a catheter which is used in the dilatation of occluded blood vessels. This includes laser thermal angioplasty where the laser energy heats up a metal tip, and direct laser angioplasty where the laser energy directly ablates the occlusion. One form of the latter approach uses an EXCIMER LASER which creates microscopically precise cuts without thermal injury. When laser angioplasty is performed in combination with balloon angioplasty it is called laser-assisted balloon angioplasty (ANGIOPLASTY, BALLOON, LASER-ASSISTED).

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Treatment using irradiation with LASER light of low power intensity so that the effects are not due to heat, as in LASER THERAPY. These non-thermal effects are thought to be mediated by a photochemical reaction that alters CELL MEMBRANE PERMEABILITY, leading to increased mRNA synthesis and CELL PROLIFERATION. Low-level laser therapy has been used for a wide variety of conditions, but most frequently for wound healing and pain control.

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