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Izzy Livne-Bar, Adrian Nahirny, Jeremy Sivak; Activation of Retinal Astrogliosis Compromises Ganglion Cell Survival. Invest. Ophthalmol. Vis. Sci. 2013;54(15):420.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal astrocytes (RA) play an important role in maintaining retinal ganglion cell (RGC) homeostasis. In glaucomatous eyes, astrocyte activation accompanies pathological changes in the RGC layer and optic nerve head. However, roles of RA in glaucoma-associated pathology remain unclear. In order to study the specific roles activation of RA plays in RGC damage, we took advantage of an in vivo model for activation of RA and Muller cells. This model allows us to establish whether activation of retinal glia exerts protective or neurotoxic effect on RGCs exposed to excitotoxic damage.
Adult C57BL/6 mice were anesthetized and their corneas were mechanically debrided to remove the entire corneal epithelium. Corneal debridement has been reported to induce glial reactivity in the retina, independent of any acute retinal damage. Debridement-induced glial activation was validated by elevated expression of the glial fibrilary acidic protein (GFAP) in retinal astroglia. Excitotoxic damage was induced in control and experimental eyes by ocular injection of Kainic Acid (KA). The KA treated eyes were fixed and processed for TUNEL to detect retinal apoptotsis. In addition we evaluated markers of immune infiltration and inflammation.
Quantification of apoptosis revealed that debridement-induced astrogliosis does not cause RGC cell death. However, analysis of KA-induced apoptosis indicates that activation of retinal astroglia generates a five-fold increase in RGC cell death compared to controls. The astroglia activation is not associated with ocular infiltration of immune cells (microglia, macrophages, or neutrophils), indicating the effect is due to local activity.
Our results demonstrate that activation of retinal glia produces neurotoxic activity that increases RGC apoptosis following excitotoxic insult. We are currently working to identify signaling pathways mediating this activity, and whether blocking glial-activation improves RGC survival.
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