May 2008
Volume 49, Issue 13
ARVO Annual Meeting Abstract  |   May 2008
Retinal Pigment Epithelium Contribution to the Protein Component of Drusen and Age-Related Extracellular Deposits
Author Affiliations & Notes
  • H. Kochounian
    University of Southern California, Los Angeles, California
    Molecular Microbiology and Immunology,
  • E. Barron
    Doheny Eye Institute, Los Angeles, California
  • H. K. W. Fong
    University of Southern California, Los Angeles, California
    Department of Ophthalmology,
  • Footnotes
    Commercial Relationships  H. Kochounian, None; E. Barron, None; H.K.W. Fong, None.
  • Footnotes
    Support  NIH EY03040 and EY08364 (HKWF)
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 1747. doi:
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      H. Kochounian, E. Barron, H. K. W. Fong; Retinal Pigment Epithelium Contribution to the Protein Component of Drusen and Age-Related Extracellular Deposits. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1747. doi:

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : Human retinal pigment epithelial (RPE) cells, the sub-RPE space, Bruch's membrane and choriocapillaris undergo prominent aging changes not seen in most other mammals. In elderly eyes, age-related deposits may accumulate on both sides of the RPE basement membrane. The origin of the age-related material in Bruch's membrane is thought to include the RPE. Human RPE cells synthesize an extraneous splice isoform of the retinal G protein-coupled receptor (RGR), and an epitope of this exon-skipping protein variant (RGR-d) is released from the RPE into Bruch's membrane in young and old persons. The purpose of this work is to investigate the presence of extracellular RGR-d in drusen and age-related deposits in Bruch's membrane. We investigated the different types of drusen in which the RGR-d epitope is present and analyzed what types of organelle or structure, if any, are associated with RGR-d at the ultrastructural level.

Methods: : RGR-d was analyzed in human donor eyes by immunohistochemical localization at the light and electron microscopic levels. Pre-embed immunohistochemical localization at the electron microscopic level was performed by peroxidase-based detection of electron dense diaminobenzidine reaction product.

Results: : We have shown that extracellular RGR-d is present in most types of drusen, including hard, soft, large confluent and early-stage drusen. We have demonstrated the presence of the RGR-d epitope in vesicular deposits (diameter ~100 nm) and membranous debris in the inner collagenous zone and intercapillary regions at the electron microscopic level.

Conclusions: : These results confirm that particular extracellular deposits in Bruch's membrane indeed originate from the RPE. RGR-d, an RPE-specific marker, is a constituent not only of various types of drusen, but of basal linear deposits consisting of a diffuse layer of vesicular and planar material external to the RPE basement membrane.

Keywords: age-related macular degeneration • drusen • proteins encoded by disease genes 

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