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Katharina Bell, Corina Wilding, Jana Holz-Müller, Sebastian Funke, Norbert Pfeiffer, Franz H Grus; Glutamine synthetase shift involved in protective effects of GFAP antibody on retinal ganglion cells. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2567.
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© ARVO (1962-2015); The Authors (2016-present)
Glaucoma is a multifactorial, neurodegenerative disease. In the past up- as well as down-regulations were detected in the autoantibody profile in the serum of glaucoma patients. Previous studies were able to demonstrate protective effects of the down-regulated antibody against GFAP on a neuroretinal cell line. With this study we wanted to analyse the protective antibody effect in more detail using a porcine retinal organ culture.
The retina along with the RPE was isolated from porcine eyes derived from 3-6 month old pigs. The retinal explants were incubated either with 1 µg/ml GFAP antibodies for 24 h or without antibodies as control. Mass spectrometric analysis of the retinae were conducted. Following incubation Brn3a, DAPI, TUNEL and glutamine synthetase staining were performed. A quantification of retinal ganglion cells was performed as well as an analysis of the glutamine synthetase intensity. Glutamine synthetase analysis was performed by analyzing the overall staining in the retinae as well as the intensity of staining in the retinal ganglion cell layer.
Rgc/mm increased significantly in GFAP ab incubated retinal explants (30 % more RGC/mm) (17.9 rgc/mm) (p=0.04) in comparison to the untreated controls (13.8 rgc/mm). Mass spectrometric analysis revealed elevated glutamine synthetase levels (2.5 fold upregulated in the GFAP ab incubated retinae). The overall intensity of glutamine synthetase in the retinae was slightly elevated in the GFAP group. When then analyzing the glutamine synthetase staining of the inner boarder of the retinae, significant differences between the ab incubated retinae and the control retinae (Intensity control retinae: 58.05; GFAP ab treated retinae: 85.96) (p< 0.05) were detected.
Low concentrations of GFAP antibodies have a protective effect on retinal ganglion cells. We conclude that there is a strong Müller cell participation in the demonstrated protective ab effects leading to a shift of glutamine synthetase towards the inner border of the retina. This could be either triggered via direct antibody/müller cell contact or indirectly via rgc/müller cell contact.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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