Microglia in mouse retina contralateral to experimental glaucoma exhibit multiple signs of activation in all retinal layers

Abstract

BackgroundGlaucomatous optic neuropathy, a leading cause of blindness, can progress despite control of intraocular pressure - currently the main risk factor and target for treatment. Glaucoma progression shares mechanisms with neurodegenerative disease, including microglia activation. In the present model of ocular hypertension (OHT), we have recently described morphological signs of retinal microglia activation and MHC-II upregulation in both the untreated contralateral eyes and OHT eyes. By using immunostaining, we sought to analyze and quantify additional signs of microglia activation and differences depending on the retinal layer.MethodsTwo groups of adult Swiss mice were used: age-matched control (naïve, n = 12), and lasered (n = 12). In the lasered animals, both OHT eyes and contralateral eyes were analyzed. Retinal whole-mounts were immunostained with antibodies against Iba-1, MHC-II, CD68, CD86, and Ym1. The Iba-1+ cell number in the plexiform layers (PL) and the photoreceptor outer segment (OS), Iba-1+ arbor area in the PL, and area of the retina occupied by Iba-1+ cells in the nerve fiber layer-ganglion cell layer (NFL-GCL) were quantified.ResultsThe main findings in contralateral eyes and OHT eyes were: i) ameboid microglia in the NFL-GCL and OS; ii) the retraction of processes in all retinal layers; iii) a higher level of branching in PL and in the OS; iv) soma displacement to the nearest cell layers in the PL and OS; v) the reorientation of processes in the OS; vi) MHC-II upregulation in all retinal layers; vii) increased CD68 immunostaining; and viii) CD86 immunolabeling in ameboid cells. In comparison with the control group, a significant increase in the microglial number in the PL, OS, and in the area occupied by Iba-1+ cells in the NFL-GCL, and significant reduction of the arbor area in the PL. In addition, rounded Iba-1+ CD86+ cells in the NFL-GCL, OS and Ym1+ cells, and rod-like microglia in the NFL-GCL were restricted to OHT eyes.ConclusionsSeveral quantitative and qualitative signs of microglia activation are detected both in the contralateral and OHT eyes. Such activation extended beyond the GCL, involving all retinal layers. Differences between the two eyes could help to elucidate glaucoma pathophysiology.

MicroRNA regulation in an animal model of acute ocular hypertension

“…2014; Rojas et al. 2014). In addition, our miRNA analysis revealed, through a bioinformatics analysis, a cluster of signalling pathways predicted to be regulated by the differentially expressed miRNAs.…”

Different Ipsi- and Contralateral Glial Responses to Anti-VEGF and Triamcinolone Intravitreal Injections in Rats

“…For example, topical instillation of saline to one eye resulted in marked upregulation of the mRNA expression levels of fibroblast growth factor 2 (FGF2) in the intact, contralateral fellow retina. 57 More recently, a detailed study of the macro-and microglia has shown that following elevation of the intraocular pressure in one eye, there are marked changes in the contralateral fellow intact eye, [58][59][60][61][62] highlighting the observation that activation of the retinal macro-and microglia in the uninjured eye may result as a consequence of injury to the contralateral fellow eye-thus confirming original observations that unilateral injury to one adult rat optic nerve may cause multiple cellular responses in the contralateral site. 63 In this work we studied the retinal glial response (microglia, astrocytes and Müller cells) of the rodent retina after single or repeated IVI of the substances most used at present in ophthalmology, anti-VEGF and corticosteroids, and their respective vehicles.…”

“…59 In this latter context, the microglial response may be subtle and not reach statistical significance, as in this study, or may be more intense when the insult is clearly damaging, such as after axotomy 37 or elevation of the intraocular pressure. [59][60][61][62] In summary, this work shows that there are important reactions of the glial cells in the retina to single or repeated IVI of different substances. All the injected substances cause an important micro-and macroglial response locally at the injection site and widely spread throughout the injected retina that is exacerbated by repeated injections.…”

“…Recent studies have shown that certain stimuli applied to one eye may trigger molecular and cellular responses in the contralateral untouched retina. This was the case after optic nerve axotomy, 37,63 topical instillation of saline drops, 57 ocular hypertension induced by laser photocoagulation to the limbal tissues, 58,[60][61][62] or after anti-VEGF injection. [29][30][31] At present we do not know the mechanism responsible for the response in the contralateral fellow eyes, but one possibility is the limited systemic absorption of the injected substances, and, alternatively, that retinal or eye injury results in systemic inflammatory or paracrine-mediated effects that reach the fellow eye.…”

A Magnetic Microbead Occlusion Model to Induce Ocular Hypertension-Dependent Glaucoma in Mice

“…Perfuse intact, non-operated mice as described in 4.1 and use them as uninjured controls. The use of contralateral eyes from operated mice is not recommended to assess RGC survival because changes in contralateral eyes following injury have been reported 15,16 and can confound data interpretation. Alternatively, use sham-operated eyes injected with 1.5 µl of BSS as controls.…”