Electrophysiological study of an animal model for Retinopathy of Prematurity

Abstract

Retinopathy of prematurity is a developmental eye disease associated with abnormal retinal vascular growth. It occurs in infants that are born before the 32nd gestational week and that are subjected to long periods in incubators typically rich in oxygen. The disease has two phases: (1) a delayed pathologic retinal neovascularization, due to the hyperoxia induced by the incubator environment; (2) aberrant vascularization after removal from the incubator, due to increased growth factors triggered by low oxygen availability. The aim of this study is to assess visual function in an animal model of retinopathy of prematurity treated intravitreally with an angiogenesis inhibitor. Electroretinograms (ERGs) will be performed in control mice (Mus musculus) and in animals subjected to large amounts of oxygen in a hyperbaric chamber, in order to understand the visual loss resulting from neovascularization. Forty animals will be divided into four groups with 10 subjects each: (a) sham 1: the left eye of each animal will be injected intraocularly with vehicle (phosphate-buffered saline -PBS) and the right eye will not be injected; (b) sham 2: the left eye of each animal will be injected with an angiogenesis inhibitor (a peptide that interacts with the R3 receptor of VEGF) and the right eye will be injected with a scrambled version of the same peptide with no physiological action; (c) hyperoxygenated 1: animals will undergo hyperoxygenation in a hyperbaric chamber ; (d) hyperoxygenated 2: animals will undergo hyperoxygenation in a hyperbaric chamber and will be injected intraocularly in the left eye with the active peptide and in the right eye with the scrambled peptide. Intraocular injections will be performed at the limbo-corneal-scleral region. Scotopic and photopic ERGs to 480 nm stimulation will be carried out in 30-40 minutes long sessions at P17, P21 and P30, as well as in adults. Amplitudes and latencies of the a and b waves will be measured, and intensity-response relationships fitted with Hill equations for comparison purposes. The obtained Hill parameters will be compared by ANOVA and Student's t tests with Bonferroni corrections.