INTERMEDIATE FILAMENT EXPRESSION IN HUMAN RETINAL MACROGLIA - HISTOPATHOLOGIC CHANGES ASSOCIATED WITH AGE-RELATED MACULAR DEGENERATION

Purpose: Intermediate filament expression by retinal macroglia was stu died in normal eyes, normal eyes of older subjects, and eyes of subjec ts with age-related macular degeneration (AMD), classified on the basi s of histopathologic assessment of the retinal pigment epithelium (RPE ), choroid, and donor age. Methods. Adult human retinae (N = 43) were divided into three groups: normal (< 50 years of age, with normal RPE and choroid); normal eyes of older subjects (> 50 years with histopath ologic findings indicative of AMD), on the basis of histopathologic as sessment of the RPE/choroid and donor age. Intermediate filament expre ssion by retinal macroglia was studied in cryostat sections and in ret inal flatmounts using avidin-biotin-peroxidase immunolabeling of antib odies to glial fibrillary acidic protein (GFAP) and vimentin. Results. Analyses of immunohistochemically labeled retinal sections revealed s imilar distributions of vimentin reactivity in retinae of each group. Distributions of GFAP in normal and normal aged retinae were similar, but sections of AMD-affected retinae showed evidence of GFAP expressio n by Muller cells. In flatmounts, vimentin distribution was similar in the three groups, but GFAP labeling revealed hypertrophic astrocytes, which were absent from normal retinae, in 17% of aged retinae and 55% of AMD-affected retinae. Deeply penetrating, GFAP-positive processes were observed in 17%, 27%, and 55% of normal, normal aged, and AMD-aff ected retinae, respectively. Conclusions: Variation in GFAP and viment in expression in retinal macroglia is affected by increasing age, and a distinctive variation of intermediate filament expression in retinal macroglia is associated with the pathogenesis of AMD.