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C.–M. Li, M.E. Clark, M.F. Chimento, C.A. Curcio; Apolipoprotein Localization in Isolated Drusen and Retinal Apolipoprotein Gene Expression . Invest. Ophthalmol. Vis. Sci. 2006;47(13):855.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate apolipoprotein (apo) gene expression in native human retinal pigment epithelium (RPE) and neurosensory retina; to detect apolipoproteins within age–related, extra–macular drusen.
Drusen were isolated manually from 10 eyes of 10 donors (age, 58–93 yr) with grossly normal maculas that were preserved in 4% paraformaldehyde within 6 hr post–mortem. In cryosections of druse–enriched pellets (6–57 drusen per eye), apo's A–I, A–II, B, C–I, C–II, C–III, E, and J were detected by indirect immunofluorescence. Two graders assessed immunoreactivity prevalence and pattern. mRNA transcripts were detected by reverse–transcriptase polymerase chain reaction (RT–PCR), with human hepatoma HepG2 as positive control.
Extra–macular drusen were classified in two groups on gross appearance, transparent with a reflective shell and cloudy; the proportion of the latter increased significantly with age. All apo's examined were detectable, in descending order of prevalence: apoE (99.5%), apoJ (99.5%), apoC–I (93.1%), apoB (80.4%), apoA–I (61.0%), apoA–II (59.2%), apoC–II (57.7%), and apoC–III (16.6%). Immunoreactivity was either diffusely distributed throughout drusen (56.7%), confined to the druse rim (16.0%), or both (21.2%). Six percent displayed evidence of organized substructure reminiscent of active remodeling. The proportion of diffusely labeled drusen decreased significantly with age for apoE (p=0.034) and apoE/C–I combined (p=0.027). RT–PCR products for apo's C–I, C–II, E, and J were found in retina and RPE; for apoA–II, retina only; apoC–III message was undetectable.
To an emerging model of an RPE–secreted large lipoprotein particle implied by previous work, this study adds apoC–I and apoC–II, major modulators of lipoprotein lipase activity, and confirms previously demonstrated apo's A–I, B–100, and E. It is possible that a neutral lipid rich druse shell containing apo's will be visible in the living fundus.
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