Microglial Population In Contralateral Mice Retina To Experimental Glaucoma: A Qualitative And Quantitative Study

Abstract

Purpose: : To analyse the qualitative and quantitative changes of laser-induced ocular hypertension (OHT) in microglial population of eyes with OHT (OHT-eyes) and contralateral eyes two weeks after lasering.

Methods: : Adult albino Swiss mice were divided in two groups: naive; (age-matched control; n=6) and lasered (n= 6). Retinal whole-mounts were immunostained with anti-Iba1, and the morphology, density, and distribution of Iba1+ microglial cells were analysed.

Results: : In the three study groups, Iba1+ microglias were observed throughout the retina, distributed in the subretinal space (SS), outer plexiform layer (OPL), inner plexiform layer (IPL), ganglion-cell layer (GCL) and nerve-fibre layer (NFL). In naïve eyes, Iba1+ microglias in the OPL and IPL exhibited a branched morphology emanating from small cell bodies. By contrast, Iba1+ microglias in the SS had rounded bodies with fewer and shorter processes; in the NFL and in the GCL, Iba1+ microglias were less ramified and were distributed parallel to axons of the retinal ganglion cells. Iba1+ cells in contralateral and OHT-eyes exhibited morphological features that differed from naïve:i) Iba1+ microglial bodies were more robust; ii) Iba1+ microglial processes were thicker and more branched in contralateral eyes and thicker and retracted in OHT-eyes. The number of Iba1+ microglias in OHT-eyes and contralateral untreated eyes increased in comparison to naïve (p< 0.001 and p< 0.041 respectively).

Conclusions: : Two weeks of laser induced-OHT triggered microglial retinal changes in the contralateral untreated and OHT-eyes. The microglial behaviour in contralateral untreated eyes, lead us to suggest that the use of contralateral eyes as internal controls in experimental unilateral OHT, should be reconsidered.

Keywords: microglia • retina • immunohistochemistry