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D.D. Hunter, S. Aisenbrey, D. Bacher, W.J. Brunken; RPE Cells Adhere to Bruch's Membrane Laminins Using –3– and –6–Integrins . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2319.
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© ARVO (1962-2015); The Authors (2016-present)
Macular degenerations are characterized by alterations in the structure of Bruch’s membrane (BrM) leading (among others) to changes in adhesion properties, perhaps via changes in interactions with extracellular matrix (ECM) proteins. RPE cells express ECM proteins including laminins, and can form a matrix containing those laminins. We previously showed that RPE cells synthesize several laminin chains in vivo and in vitro including components of laminins 1, 5, and 10/11. The aim of this study is to identify specific laminin receptors expressed by RPE cells and test adhesion to laminin substrates accordingly.
Immunohistochemistry was performed on retinal sections and RPE cell lines using antibodies against laminin and integrin chains, and components of adhesion complexes (FAK, ILK, pyk2). Cell adhesion assays were performed using laminins 1, 5, and 10/11 as substrates and anti–integrin antibodies as inhibitors. ILK siRNA was transfected and ILK protein reduction was quantified using manufacturer’s recommendations.
As reported previously, the laminin chains α1, α3, α5, ß1, ß2, ß2, γ1, and γ2 are produced by RPE cells in vivo and in vitro, suggesting that RPE cells can synthesize laminins including laminin 1 (α1ß1γ1), 5 (α3ß3γ2), 10/11 (α5ß1/2γ1). RPE cells produce and localize receptors (integrins α3, α6, ß1 and ß4), and downstream components (FAK, ILK, and pyk2). RPE cells preferentially adhere to laminin 5, and adhesion to laminins 1, 5, and 10/11 is inhibited by antibodies to integrins known to be receptors for each laminin. RPE cell adhesion is attenuated by lowering expression of ILK with siRNA.
Laminins are expressed by RPE cells, which secrete them into BrM. Adhesion of RPE cells to BrM laminins is mediated by specific integrins and integrin–linked kinases. Composition of matrix molecules is likely to play a critical role in diseases involving the Bruch’s membrane–RPE complex and would, therefore, be critical for culture and transplantation approaches of RPE cells and their possible substitutes.
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