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B. Lorber, K. R. Martin; Enhanced Neurite Outgrowth of Adult Rat Retinal Ganglion Cells After Elevation of Intraocular Pressure Is Mediated by Activated Retinal Glia. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1674.
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© ARVO (1962-2015); The Authors (2016-present)
Elevation of intraocular pressure (IOP) has a detrimental effect on retinal ganglion cell (RGC) survival in human glaucoma and in experimental models of the disease. However, the responses of RGC to pressure-induced injury are not fully understood. We used a retinal cell culture model to dissect out the cellular responses of RGC to IOP elevation, and in particular to explore the interactions between RGC and activated retinal glia.
Retinae were dissected from untreated adult Sprague-Dawley rats and from rats that had received IOP elevation using a well-established trabecular laser model. Retinal cells were dissociated and cultured at the same density for 3 days in the presence or absence of a glial-specific toxin, aminoadipic acid. Cells were subsequently stained for βIII-tubulin to identify RGC, and glial-fibrillary acidic protein (GFAP) to identify activated retinal glia. Mean RGC survival, neurite outgrowth, and numbers of activated retinal glia were quantified. Experiments were repeated at least three times.
Adult RGC from experimental glaucoma eyes showed significantly enhanced neurite outgrowth (119 ± 11µm; p<0.05) compared to RGC derived from contralateral eyes (40 ± 22µm) or control animals (63 ± 14µm). This enhanced neurite outgrowth correlated with survival of GFAP+ glia (186 ± 43) in retinal cultures from laser-treated eyes. Treatment with aminoadipic acid, a selective glial toxin, reduced the numbers of GFAP+ glia by around 70% (56 ± 7; p<0.05), without affecting RGC survival. However, aminoadipic acid treatment significantly reduced the neurite outgrowth potential of RGC in retinal cultures from experimental glaucoma eyes (45 ± 3µm; p<0.03).
Elevation of IOP leads to enhanced RGC neurite outgrowth when retinal neurons are subsequently cultured. This effect appears to be mediated by activated retinal glia and the effect can be blocked by selective glial toxicity. Future studies will investigate the mechanisms of this glial-dependent RGC neurite outgrowth, potentially revealing novel trophic factors for the treatment of retinal injury and disease.
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