Retinal Microglia in Glaucoma
Jia-Wei Wang1, Shi-Da Chen, Xiu-Lan Zhang
1*State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, P.R. China †Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Karls-University, Heidelberg, Germany.
Objective:
To review the current research on microglia as it relates to glaucoma, and summarize the potential microglia-targeted therapies.
Data Sources:
The data were collected from PubMed and Google Scholar databases published in English up to July 2014. Keywords used, both alone and in combination, in the database search included retinal microglia, over-activation and inhibition of microglia, and glaucoma.
Study Selection:
Articles were selected and reviewed if they involved microglia in animal models or human patients with glaucoma. Moreover, we also cited some comprehensive amalgamation of published literature.
Results:
Together with the macroglia [astrocytes, ependymal cells, oligodendrocytes, radial (Müller) cells], the microglia form the supportive tissue of the central nervous system (CNS). Glial cells are generally smaller than the neural cells, but outnumber them by a factor of 5 to 10 with marked regional differences in the CNS. Approximately half of the volume of the CNS is composed of glial cells. Because of the blood-retina barrier, blood-born immunologic cells cannot penetrate into the retina under physiological conditions; the retinal microglial cells are the primary immunocompetent cells in the retina. The microglial cells are involved in any process of cell degeneration and loss, including retinal ganglion fiber and cell loss. Surveying the retinal tissue in normal situations as "spiders in a net," the retinal microglial cells change their form from a resting dendritic-like shape to an activated ameboid form in the case of invading microorganisms or cell damage. They are involved in the process of cell apoptosis and removal of the dead cells. Studies suggested that inhibition of the microglial cell activation in the case of optic nerve damage can increase the number of surviving retinal ganglion cells and may thus be neuroprotective.
Conclusions:
Activated microglia appear early in the glaucomatous process and may contribute detrimentally to the neuronal apoptosis in the later stage. Neuroprotective strategies that inhibit activated microglia may provide novel treatment modalities for glaucomatous optic neuropathy and any other retinal and optic nerve disease.
Insights
Microglia, the immune cells of the retina, become activated in glaucoma and may harm retinal ganglion cells. Inhibiting this microglial activation shows promise for neuroprotection in glaucoma.
Area of Science:
- Neuroscience
- Immunology
- Ophthalmology
Background:
- Microglia are the primary immunocompetent cells in the retina, acting as the central nervous system's resident immune cells.
- Under physiological conditions, retinal microglia adopt a resting, dendritic-like surveillance state.
- Upon injury or disease, microglia transform into an activated ameboid form, participating in cellular debris removal and apoptosis.
Purpose of the Study:
- To review current research on the role of microglia in glaucoma.
- To summarize potential therapeutic strategies targeting microglia for glaucoma treatment.
Main Methods:
- Literature search of PubMed and Google Scholar databases up to July 2014.
- Keywords included 'retinal microglia,' 'glaucoma,' 'microglia activation,' and 'neuroprotection.'
- Selected articles focused on microglia in animal models or human patients with glaucoma.
Main Results:
- Microglia are involved in retinal ganglion cell loss and degeneration in glaucoma.
- Activated microglia contribute to neuronal apoptosis in later stages of glaucoma.
- Inhibition of microglial activation in optic nerve damage increased retinal ganglion cell survival, suggesting a neuroprotective effect.
Conclusions:
- Activated microglia play a detrimental role in the pathogenesis of glaucoma.
- Targeting and inhibiting microglial activation presents a potential novel therapeutic strategy for glaucomatous optic neuropathy.
- Microglia-targeted therapies may offer neuroprotection for various retinal and optic nerve diseases.
