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Microglia serve key homeostatic roles, and respond to neuronal perturbation and decline with high spatiotemporal resolution. The course of all chronic CNS pathologies is thus paralleled by local microgliosis and microglia activation beginning at early stages. However, the possibility of using live monitoring of microglia during early disease progression to predict the severity of neurodegeneration has not been unexplored. Since the retina allows live tracking of fluorescent microglia in their intact niche, here we investigated their early changes in relation to later optic nerve neurodegeneration. Thus, we used the DBA/2J mouse model of inherited glaucoma, which develops progressive retinal ganglion cell degeneration of variable severity during aging, and thus represents a useful model to study pathogenic mechanisms of retinal ganglion cell decline similar to human glaucoma. We imaged CX3CR1(+/GFP) microglial cells in vivo at ages ranging from 1 to 5 months by confocal scanning laser ophthalmoscopy (cSLO) and quantified cell density and morphological activation. We detected early microgliosis at the optic nerve head (ONH), where axonopathy first manifests, and could track attenuation of this microgliosis induced by minocycline. We also observed heterogeneous and dynamic patterns of early microglia activation in the retina. When the same animals were aged and analyzed for the severity of optic nerve pathology at 10 months of age, we found a strong correlation with the levels of ONH microgliosis at 3 to 4 months. Our findings indicate that live imaging and monitoring the time course and levels of early retinal microgliosis and microglia activation in glaucoma could serve as indicators of future neurodegeneration severity.
Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, Utah 84132 alejandra.bosco@neuro.utah.edu.
Full article5.1 Rodent (Part of: 5 Experimental glaucoma; animal models)
11.8 Neuroprotection (Part of: 11 Medical treatment)