Comparison of lectin binding of drusen, RPE, Bruch's membrane, and photoreceptors.
OBJECTIVE
Drusen are deposits located between the retinal pigment epithelium and Bruch's membrane in age-related maculopathy. They are believed to be photoreceptor byproducts that are incompletely metabolized by the retinal pigment epithelium. This study therefore compares the lectin histochemistry of drusen, photoreceptors, retinal pigment epithelium, and Bruch's membrane.


METHODS
Semithin sections of three eyes with age-related maculopathy were studied using 19 biotinylated lectins and an avidin-peroxidase-revealing system with and without neuraminidase pretreatment.


RESULTS
High mannose, bi and tri-antennary nonbisected and bisected complex N-glycan, N-acetyl glucosamine and galactose were expressed by drusen, retinal pigment epithelium, Bruch's membrane, and photoreceptors while N-acetyl galactosamine and fucose were absent; treatment with neuraminidase exposed subterminal galactose in both sites and sparse N-acetyl galactosamine residues in drusen alone. Overall, there were striking similarities between the lectin binding of drusen, retinal pigment epithelium, and the photoreceptor outer segments, though cone outer segments were distinct in some features of their O-linked glycosylation.


CONCLUSIONS
The results suggest that the pathogenesis of drusen is a combined mechanism, involving photoreceptors, Bruch's membrane, and the retinal pigment epithelium.
D'Souza
Yvonne B
YB
Academic Unit, Manchester Royal Eye Hospital, Manchester, UK. yvonnedsouza@fsmail.net
Jones
Carolyn J P
CJ
Bonshek
Richard E
RE
D001710:Biotin / Q000378:metabolism; D016570:Bruch Membrane / Q000378:metabolism* / Q000648:ultrastructure; D006651:Histocytochemistry; D006801:Humans; D037102:Lectins / Q000378:metabolism*; D008268:Macular Degeneration; D009439:Neuraminidase / Q000378:metabolism; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D015593:Retinal Drusen / Q000378:metabolism*; D055213:Retinal Pigment Epithelium / Q000378:metabolism* / Q000648:ultrastructure
D037102:Lectins; D001710:Biotin; D009439:Neuraminidase