Microglia are the macrophages of the brain and retina. They play important roles in tissue homeostasis, recovery from injury and in some retinal diseases In the healthy retina, microglia cells are normally located in the plexiform layers. They exhibit elaborate ramified processes and are responsible for immune surveillance of the retina. Oxidative stress, hypoxia or inherited mutations that cause retinal injury will trigger microglia reactivity. The microglia cells will adopt an amoeboid morphology, increase proliferation and migrate to the sites of injury. This inflammatory response from the microglia can rapidly enhance tissue repair and return to homeostasis. However, sustained microglial inflammatory responses can instigate severe alterations in retinal integrity, and lead to neuronal demise . Changes in microglia inflammatory responses may play a key role in various retinopathies such as glaucoma, age-related macular degeneration and retinitis pigmentosa (Langmann et al., 2019).
Schematic depicting the different cell types and layers that make up the neural retina in an adult zebrafish adapted from Baden et al., 2019. Microglia can be found throughout the retina, they are the macrophages of the neural retina.
References
Rashid K, Akhtar-Schaefer I, Langmann T(2019)
Microglia in Retinal Degeneration
Front. Immunol. https://doi.org/10.3389/fimmu.2019.01975