Longitudinal in vivo Study of Chronic Intraocular Hypertensive Injury to the Mouse Retinal Ganglion Cells Using a Novel SLO Imaging Technique

Abstract

Purpose: : Elevation of intraocular pressure (IOP) to the retina and the optic nerve are frequently incriminated as vision reducing events. Multiple variables are of interest in the subsequent disease development, such as general changes to blood flow, and adaption of retinal ganglion cells (RGCs). Applying advanced imaging tools may increase insight to relevant changes in disease development, furthermore, key to future prevention.

Methods: : We induced chronic elevation of IOP to the mouse eye by a one-time injection of microspheres to the anterior chamber in transgenic mice (Thy-1 YFP H), thus allowing to observe morphological responses of single RGCs. In vivo imaging was performed with a scanning laser ophthalmoscope (SLO), specifically built for the mouse eye, to observe longitudinal changes over 4 months. At the endpoint, a confocal microscopy of the retinal flat mount allowed a morphological comparison. The optic nerves were examined by traditional histological stains and immunohistochemistry.

Results: : The longitudinal in vivo observation, showed changes in retinal blood flow, sprouting in RGC dendrites and their absence of regression. The axonal density in the retinal flat mount was diminished in the hypertensive eye and correlated well to the observation during the in vivo imaging. Histopathology of optic nerve sections showed expectedly ipsilateral atrophy.

Conclusions: : The combined approach of a recently developed mouse model of chronic ocular hypertension and a SLO, specifically developed for the mouse eye, allowed observation of longitudinal changes on an RGC level. The in vivo observation of RGC changes in the neural retina, as confirmed by confocal microscopy and immunohistochemistry in retinal flat mount, has enhanced our understanding of important physiopathological mechanisms of injury to neuronal tissue.

Keywords: ganglion cells • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • transgenics/knock-outs