Rod-like microglia are restricted to eyes with laser-induced ocular hypertension but absent from the microglial changes in the contralateral untreated eye

PLoS One. 2013 Dec 18;8(12):e83733. doi: 10.1371/journal.pone.0083733. eCollection 2013.

Abstract

In the mouse model of unilateral laser-induced ocular hypertension (OHT) the microglia in both the treated and the normotensive untreated contralateral eye have morphological signs of activation and up-regulation of MHC-II expression in comparison with naïve. In the brain, rod-like microglia align to less-injured neurons in an effort to limit damage. We investigate whether: i) microglial activation is secondary to laser injury or to a higher IOP and; ii) the presence of rod-like microglia is related to OHT. Three groups of mice were used: age-matched control (naïve, n=15); and two lasered: limbal (OHT, n=15); and non-draining portion of the sclera (scleral, n=3). In the lasered animals, treated eyes as well as contralateral eyes were analysed. Retinal whole-mounts were immunostained with antibodies against, Iba-1, NF-200, MHC-II, CD86, CD68 and Ym1. In the scleral group (normal ocular pressure) no microglial signs of activation were found. Similarly to naïve eyes, OHT-eyes and their contralateral eyes had ramified microglia in the nerve-fibre layer related to the blood vessel. However, only eyes with OHT had rod-like microglia that aligned end-to-end, coupling to form trains of multiple cells running parallel to axons in the retinal surface. Rod-like microglia were CD68+ and were related to retinal ganglion cells (RGCs) showing signs of degeneration (NF-200+RGCs). Although MHC-II expression was up-regulated in the microglia of the NFL both in OHT-eyes and their contralateral eyes, no expression of CD86 and Ym1 was detected in ramified or in rod-like microglia. After 15 days of unilateral lasering of the limbal and the non-draining portion of the sclera, activated microglia was restricted to OHT-eyes and their contralateral eyes. However, rod-like microglia were restricted to eyes with OHT and degenerated NF-200+RGCs and were absent from their contralateral eyes. Thus, rod-like microglia seem be related to the neurodegeneration associated with HTO.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Astrocytes / pathology
  • Astrocytes / radiation effects
  • Axons / pathology
  • Axons / radiation effects
  • Biomarkers / metabolism
  • Calcium-Binding Proteins / metabolism
  • Intraocular Pressure / radiation effects
  • Lasers / adverse effects*
  • Male
  • Mice
  • Microfilament Proteins / metabolism
  • Microglia / metabolism
  • Microglia / pathology*
  • Microglia / radiation effects*
  • Ocular Hypertension / etiology*
  • Ocular Hypertension / metabolism
  • Ocular Hypertension / pathology*
  • Ocular Hypertension / physiopathology
  • Retinal Ganglion Cells / pathology*
  • Retinal Rod Photoreceptor Cells / pathology*
  • Sclera / pathology
  • Sclera / physiopathology
  • Sclera / radiation effects

Substances

  • Aif1 protein, mouse
  • Biomarkers
  • Calcium-Binding Proteins
  • Microfilament Proteins

Grants and funding

This work was supported by RETICs ENFERMEDADES OCULARES: “Prevención, detección precoz y tratamiento de la patología ocular prevalente degenerativa y crónica.” (Grant RD12/0034/0002 and RD12/0034/0014, ISCIII, Spanish Ministry of Science and Innovation); Grant SAF-2012-38328 (Spanish Ministry of Economy and Innovation); Grant PI10/01496 (ISCIII); and 04446/GERM/07 (Regional Government of Murcia, Fundación Séneca). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.