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Julie Sanderson, Ning Ma, Jeremy D. Rhodes, David C. Broadway; Localisation Of The P2X7 Receptor In The Human Retina Using A Novel mRNA Profiling Technique. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2244.
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We have previously shown that activation of P2X7 receptors in the human retina causes loss of retinal ganglion cells (RGCs). However, currently the localization of the P2X7 receptor in the retina is not clear. The purpose of these experiments was to determine the localisation of the P2X7 receptor in the human retina using a novel mRNA profiling technique.
Human retina was obtained from the East Anglian Eye Bank within 24 hours post mortem. The macula region of the retina was dissected, mounted and cryosectioned (20µm sections) in the plane of the retinal nuclear layers. RNA was extracted and QRT-PCR conducted for retinal markers (RCVRN; photoreceptors, CALB; horizontal cells, CHAT; amacrine cells and THY-1; RGCs) and P2X7 (P2X7R) mRNA (n=6). Immunohistochemistry was carried out on transverse sections for P2X7 receptor using an antibody raised to the extracellular domain.
P2X7 receptor mRNA was found to be expressed in the human retina. There was no significant difference between expression in the macula and expression in peripheral retina (n=4). Expression was low in the outer retina with no coincidence with the photoreceptor marker recoverin (RCVRN). The initial peak of P2X7 expression corresponded with calbindin (CALB) expression and then remained elevated, including in the retinal ganglion cell layer. Immunohistochemistry showed labelling in the outer plexiform layer with less intense labelling evident in the inner plexiform layer.
The P2X7 receptor was located in the outer and inner plexiform layers of the human retina. There was no evidence for expression in the photoreceptors, but P2X7R mRNA expression was coincident with the horizontal cell marker CALB. In the inner retina, P2X7R expression was coincident with both amacrine and RGC markers. This suggests that RGCs do express the P2X7 receptor and that RGC death occurring as a result of P2X7 stimulation could be mediated by direct mechanisms although indirect mechanisms may also play a role.
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