Abstract
PurposeRetinal vein occlusion (RVO) has been investigated in several laser-induced animal models using pigs, rabbits and rats. However, laser-induced RVO has been rarely reported in mice, despite the impressive number of available mutants, ease of handling and cost effectiveness. The aim of this study was to further assess the feasibility of a RVO mouse model for gene expression analysis and its possible use to investigate effects of hypoxia.MethodsC57Bl/6J mice were injected with eosin Y for photo-sensitization. Subsequently, large retinal veins were laser-treated in one eye to induce vascular occlusion. Contralateral control eyes received non-occlusive retinal laser treatment sparing large vessels. The animals were followed for up to eight days and assessed by funduscopy, angiography, hypoxyprobe staining, histopathology and gene expression analysis by qPCR and RNA sequencing (RNAseq). Another group of mice was left untreated and studied at a single time point to determine baseline characteristics.ResultsLaser-induced RVO persisted in half of the treated veins for three days, and in a third of the veins for the whole observation period of 8 days. Funduscopy revealed large areas of retinal swelling in all laser-treated eyes, irrespective of vascular targeting or occlusion status. Damage of the outer retina, retinal pigment epithelium (RPE), and even choroid and sclera at the laser site was observed in histological sections. Genes associated with inflammation or cell damage were highly up-regulated in all laser-treated eyes as detected by RNAseq and qPCR. Retinal hypoxia was observed by hypoxyprobe staining in all RVO eyes for up to 5 days with a maximal extension at days 2 and 3, but no significant RVO-dependent changes in gene expression were detected for angiogenesis- or hypoxia-related genes.ConclusionThe laser-induced RVO mouse model is characterized by a predominant general inflammatory and tissue damage response, which may obscure distinct hypoxia- and angiogenesis-related effects. A non-occlusive laser treatment control is essential to allow for proper data interpretation and should be mandatory in animal studies of laser-induced RVO to dissect laser-induced tissue damage from vascular occlusion effects.
Highlights
Retinal vein occlusion (RVO) is a common vascular eye disease that causes vision loss due to macular edema, retinal bleeding and ischemia [1,2]
Laser-induced RVO persisted in half of the treated veins for three days, and in a third of the veins for the whole observation period of 8 days
Damage of the outer retina, retinal pigment epithelium (RPE), and even choroid and sclera at the laser site was observed in histological sections
Summary
Retinal vein occlusion (RVO) is a common vascular eye disease that causes vision loss due to macular edema, retinal bleeding and ischemia [1,2]. Appropriate animal models to study tissue regeneration following RVO are still being developed. The most commonly reported method to occlude retinal veins is the intravenous injection of a photosensitizier such as rose bengal, fluorescein, erythrosin B, or neutral red and subsequent localized activation by an appropriate laser treatment. This strategy appears to work well in pigs [7,8,9,10,11], rabbits [12,13], and rats [14,15,16,17]
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