Neuroretinal Cell Death In A Murine Model Of Closed Globe Injury; Pathological And Functional Characterisation

Abstract

 

Purpose:

 

Blunt ocular trauma causes a spectrum of retinal injury from transient dysfunction, with full recovery, to severe damage with neuroretinal cell death and permanent visual loss. The cell death mechanisms underlying the injury responses are not known and there are currently no therapies to improve visual outcome. We aimed to develop a rat model of blunt ocular trauma-induced retinal injury and hypothesised that photoreceptor apoptosis would cause reduced visual function in this model.

 

Methods:

 

The eyes of anaesthetised adult rats were injured by a standardised projectile impact (20m/s, 0.095g, .22 inch) to inferior sclera. We confirmed injury by dilated indirect fundoscopy and retinal pathology using: (i), light and electron microscopy (EM; n=4 animals per time point) at 2 hours and 2 and 14 days after bilateral injury to monitor structural changes; (ii), terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL; n=4 animals) at 2 days after unilateral injury to assess apoptosis;(iii), flash electroretinography (ERG; n=8 animals) at 2 hours and 7 and 14 days after unilateral injury to assess retinal function.

 

Results:

 

We demonstrate a reproducible retinal injury model displaying retinal necrosis at the impact site (shown by nuclear morphology), surrounding commotio retinae with photoreceptor outer segment disruption (Fig. 1b) and apoptosis demonstrated by nuclear changes (Fig. 1c) and TUNEL positive cells confined to the outer nuclear layer and specific photoreceptor loss by 2 weeks with sparing of the inner retinal layers (Fig. 1d). There was marked a wave attenuation on ERG consistent with the observed photoreceptor death.

 

Conclusions:

 

This is the first murine closed globe injury model and the only retinal trauma model causing specific photoreceptor cell death. The clinical appearance mirrors severe retinal injury after blunt ocular trauma in humans and the EM features are consistent with previous human and animal studies of commotio retinae. The results indicate a rationale for developing anti-apoptotic therapies for retinal injury.  

 

Keywords: trauma • apoptosis/cell death • retina: distal (photoreceptors, horizontal cells, bipolar cells)