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KH Wu, FA Billson, PL Penfold; Quantitative Analysis of GFAP Expression in Dry AMD . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2808.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: GFAP is an established marker of retinal glia and has been shown to be modulated by cytokines and retinal pathology. Upregulation of GFAP expression following retinal injury has been demonstrated in both astrocytes and Müller cells. This study aims to investigate and quantify changes in GFAP expression in human neural retinae associated with age-related macular degeneration (AMD) compared with age-matched and young adult normal retinae, at three levels of expression: constitutive (astrocytes), aberrant (Müller cells) and total. Methods: Human eyes obtained from the Lion's NSW Eye Bank were classified following histopathologic survey into young-normal (n=3), aged-normal (n=3), drusen (n=5) and Dry AMD (geographic atrophy-GA) (n=6) groups. All groups were matched for postmortem delay, gender, and the latter three groups matched for age. Immunohistochemistry using GFAP antibody and Cy-3 fluorochrome was carried out on paramacular cryosections of 15 micrometer thickness. The intensity of GFAP immunoreactivity was analyzed and quantified using confocal microscopy followed by digital image analysis (NIH). Statistical analyses were performed using unpaired two-tailed Student's t-tests. Results: Quantification revealed significant increases in both GFAP immunoreactivity and distribution in drusen-associated retinae compared with both aged (p=0.0298) and young (p=0.0036) controls for constitutive expression; and in Dry AMD retinae compared with the normal controls for both aberrant and total expression (p<0.05 in all groups). Both GFAP immunoreactivity (p=0.0359) and distribution (p=0.0267) was significantly higher in Dry AMD compared with drusen-associated retinae for aberrant expression. Increased area of GFAP labeling was observed in aged-normal compared with young-normal for total expression (p=0.0383). Conclusion: We have previously demonstrated that neither prolonged postmortem delay up to 30 hours nor duration of tissue storage in fixatives produces significant changes in GFAP immunoreactivity in normal human adult retinae. The increased constitutive GFAP expression observed in the present study was found only in retinae associated with drusen; whilst increased aberrant expression was observed only with dry AMD. Increased distribution of GFAP was associated with aged- vs young-normal retinae. We have established methods for quantification and analysis of modulation of GFAP expression in AMD-affected retinae. This study will facilitate further elucidation of the significance of modulation of GFAP expression in the pathogenesis of AMD.
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