Comparative analysis of intraocular pressure and laser-induced hypertension in mice of different strains and ages

Abstract

Purpose : We recently provided the first evidence showing that Prox-1, the master control gene for lymphatic development, is expressed in Schlemm’s canal, a critical structure in the drainage of aqueous humor. This study was designed to investigate the effect of mouse strain and age on intraocular pressure (IOP), and to characterize a laser-induced model of elevated IOP. This model may overcome barriers of other animal models of elevated IOP that hinder the study of Schlemm’s canal.

Methods : IOP was measured in mouse strains of BALB/c, C57BL/6 and CD1 at 8 weeks of age for 7 consecutive days using a non-invasive TonoLab tonometer. Anterior chamber angles were evaluated by anterior segment optical coherence tomography (OCT). IOPs were also measured in CD1 mice at 5 weeks of age, and CD1 mice aged 5 and 8 weeks were examined for IOP elevation induced by laser photocoagulation. We also assessed the difference between occlusion of episcleral veins alone and when combined with 270° limbal vessel occlusion. Whole-mount retinae were harvested at day 7 post-procedure and immunostained for Brn3a. Positive staining retinal ganglion cells (RGCs) were quantified with NIH ImageJ software.

Results : Baseline IOP in CD1 mice was significantly higher than in BALB/c and C57BL/6 mice at 8 weeks of age. No significant difference was found for baseline IOPs in CD1 mice aged 5 and 8 weeks. After single or combined laser treatment in CD1 mice aged 5 weeks or 8 weeks, IOP was significantly elevated for 5 to 6 days before returning to the baseline by day 7 post-procedure. OCT assessment indicated less synechiae in the anterior chamber angles with single versus combined laser treatment. The density of RGCs was significantly reduced after both single and combined laser treatment.

Conclusions : Laser photocoagulation of episcleral veins in CD1 mice aged 5 to 8 weeks may be used to induce ocular hypertension. The model permits the study of both Schlemm’s canal and the posterior segment.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.