Rod microglia is absent from microglial changes in mice retina contralateral to experimental glaucoma

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Abstract

Purpose

The aim of the present study was to analyze the presence of rod microglia in a model of unilateral laser-induced ocular hypertension (OHT.

Methods

Adult albino Swiss mice were divided into two groups: naïve (age-matched control; n=6) and lasered (n= 6). Retinal whole-mounts were analyzed by immunostaining using antibodies against Iba1, MHC-II, ED1 and NF-200.

Results

The nerve-fiber layer (NFL) of contralateral and OHT-eyes had ramified microglia related to blood vessels, similar to those of aged-matched control eyes. However, only OHT-eyes had rod microglia. Rod microglia lay parallel to and close to the axons and were related to retinal ganglion cells (RGCs) showing signs of degeneration (NF-200+RGCs). In some instances, rod microglia processes surrounded the soma and proximal dendrites of NF-200+RGCs and penetrated the underlying RGC layer and inner plexiform layer. Microglia had morphological signs of activation and MHC-II expression up-regulation in both, the contralateral and OHT-eyes. However, only in OHT-eyes did rod microglia show ED1 staining throughout the NFL. With respect both to morphological features and to ED1 immunostaining patterns, three stages of rod microglia were detected, with processes shortening, somas thickening, and ED1 immunostaining increasing progressively from stage 1 to 3.

Conclusion

After 15 days of unilateral laser-induced OHT, rod microglia was restricted to eyes with OHT and degenerated NF-200+RGCs but absent in contralateral eyes. The microglia activation observed in contralateral eyes could be related with neuroprotection.

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