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Alistair J Barber, Wei-Wei Wang, Justin Etzel, Cassandra Ondeck, Jeffrey M Sundsrom; Fibulin-3 distribution in sections of postmortem human retina containing drusen. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2439.
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© ARVO (1962-2015); The Authors (2016-present)
Fibulin-3 (FBLN-3) is a secreted glycoprotein known to carry a point mutation in Doyne honeycomb retinal dystrophy, which is characterized by the early onset of drusen formation. The potential role of FBLN-3 in formation of drusen in age-related macular degeneration (AMD), however, has not been established. The aim of this study was to further characterize the distribution of FBLN-3 in human retinas with AMD compared to those with no history of retinal disease.
Formalin-fixed frozen sections were purchased from the National Disease Research Interchange (NDRI). Donors were considered either “Normal” with no history of retinal disease (n=3) or “AMD” with known medical history of macular degeneration (n=4); both female and male donors were included. Immunohistochemistry was performed using primary antibodies to FBLN-3 (Santa Cruz), drusen marker, ApoE (Millipore) and ALIX (Santa Cruz), a marker of extracellular vesicles. Secondary antibodies with Alexafluor tags were used (Jackson). Some sections were treated with Sudan Black (Sigma) to quench lipofuscin autofluorescence. Imaging was by confocal microscopy (Leica SP8).
Globular FBLN-3 immunoreactivity (IR) was abundant within retinal pigment epithelial cells (RPE). FBLN-3 IR was also observed within the outer segments of the photoreceptors but was absent from the other parts of the retina apart from occasional diffuse FBLN-3 immunoreactivity surrounding large inner-retina blood vessels. The edges of some small drusen in Normal retinas were positive for FBLN-3 IR, while AMD retinas contained abundant punctate FBLN-3 IR embedded throughout large drusen. There was no consistent colocalization between FBLN-3, ApoE and ALIX IR. ApoE immunoreactivity was homogeneous throughout drusen and also appeared within photoreceptors, vascular structures and the nerve fiber layer of the retina. ALIX immunoreactivity also appeared within the nerve fiber layer, inner segments of photoreceptors, and as discrete puncta in drusen.
FBLN-3 is abundant in RPE and photoreceptors, suggesting a role in both cell types. Its punctate appearance suggests a vesicle-like localization but it is not associated with ALIX. FBLN-3 is preferentially embedded within drusen associated with AMD. Our results suggest that FBLN-3 may play a role in the pathogenesis of drusen formation in Doyne honeycomb retinal dystrophy and AMD.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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