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Ellen Miller, Chris Zelinka, Andrew Fischer, Colleen Cebulla; A Novel Glial Cell in the Human Retina. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5585. doi: https://doi.org/.
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To test the hypothesis that the novel type of glial cell termed non-astrocytic inner retinal glial-like (NIRG) is present in the human retina and optic nerve.
Cadaver eyes (n=3) from the Central Ohio Lions Eyebank were fixed with 4% paraformaldehyde and frozen sections were evaluated with immunohistochemical markers to identify NIRG cells. In previous studies of other mammalian retina and optic nerve heads, NIRG cells have a unique immunohistochemical labeling profile: GFAP negative and positive for Pax2, Sox2, Sox9, nestin, and S100 beta. The NIRG cells also express Nkx2.2 in the optic nerve head in large mammals such as dog and monkey. This is different from Muller glia and astrocyte immunohistochemical labeling phenotype in the retina. Muller glia have been shown to be GFAP positive, Nkx2.2 negative. Astrocytes are GFAP and Nkx2.2 positive, with negative labeling for Sox2 and Sox9.
Inner retinal cells positive for nuclear Pax2 and negative for GFAP were identified, consistent with NIRG phenotype. Nestin and Sox2 or Sox9 dual-positive cells were scattered across inner layers in the retina and optic nerve head. Nkx2.2 positive cells were not identified in the retina or optic nerve head of these specimens. S100beta and Sox2 dual-positive cells, consistent with Muller glia, were also scattered across inner layers of the retina.
This study supports that a novel type of GFAP-negative glial cell exists in human retinas. Further work is required to determine if these are NIRG cells analogous to those identified in chick, dog, and monkey retinas. If NIRG cells exist in human retinas, this will change our understanding of the types and roles of neuronal support cells in the retina.
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