Qualitative early signs of microglial activation in mice retinas contralateral to experimental glaucoma

Abstract

PurposeTo analyze qualitative retinal microglia signs of activation after 24 h of unilateral laser‐induced ocular hypertension (OHT) in OHT‐eyes and their contralateral eyes.MethodsAlbino Swiss mice were divided into two groups, naïve (n=6) and lasered (n=9). Retinal whole mounts were immunolabeled with antibodies against Iba‐ 1 and MHC‐II.ResultsBoth in OHT eyes and in contralateral eyes Iba‐1+ cells: i)had morphological signs of activation, being these more intense in OHT eyes than in the contralateral eyes. Iba‐1+cells showed hypertrophy, soma displacement both in their own retinal layer and towards the nearest one and in some instances, reoriented microglial processes from being parallel to being perpendicular to the retinal surface. ii) were dystrophic in some instances in the photoreceptor layer (PRL); iii) in the outer plexiform layer sent processes to the PRL and this was mainly found in contralateral eyes; iv) overall, did not up‐regulate the expression of MHCII .Only in OHT eyes MHCII+ rounded cells were observed in the nerve fiber layer‐ganglion cell layer, being more numerous in the peripheral superior zone of the retina and near the optic disc. These cells were surrounded and phagocyted by numerous ameboid Iba‐1+ cells. In addition, beneath the retinal areas where this event was occurring, microglial cells of the inner plexiform layer and outer plexiform layer oriented their processes towards those areas and surrounding them.ConclusionsAt 24 h after unilateral OHT, microglial features of activation were observed not only in OHT eyes but, interestingly, also in the contralateral untreated eyes. Whether this activation favors neuroprotection or neurodegeneration needs to be clarify.