Early signs of microglial activation in mice retinas contralateral to experimental glaucoma: quantitative analysis of cells number, processes retraction and reorientation

Abstract

PurposeTo quantify 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 = 6). Retinal whole‐mounts were immunolabeled with anti Iba‐1 to quantify the: i) number of microglial cells in the photoreceptor layer (PRL), outer plexiform layer (OPL) and inner plexiform layer (IPL); ii) the area of the retina occupied by Iba‐1 + in the nerve fiber layer‐ganglion cells layer (NFL‐GCL) and; iii) the arbor area of microglial cells in the OPL and IPL. iv) the number of microglial vertical processes connecting the OPL and PRL.ResultsIn OHT eyes and contralateral eyes had no significant differences in cell number with respect to naïve. OHT eyes presented a significant decrease in microglial arbor area in the OPL in comparison with control (p < 0.01) and in the IPL in comparison with control and contralateral eyes (p < 0.01 and p < 0.05 respectively). However the retinal area occupied by Iba‐1 + cells in the NFL‐GCL was significantly increased: i) in both contralateral and OHT eyes with respect to control (p < 0.01 in both instances); and ii) in OHT eyes with respect to contralateral eyes (p < 0.05). In contralateral untreated eyes, the number of microglial vertical processes connecting the OPL and PRL were significantly increased in comparison with control and OHT eyes (p < 0.01 and p < 0.05 respectively).ConclusionsAt 24 h, laser‐induced OHT produces a reactive non‐proliferative microgliotic response both in OHT eyes and in contralateral untreated eyes. Whether this response favors neuroprotection or neurodegeneration needs to be clarify.