Retinal pigment epithelial cells synthesize laminins, including laminin 5, and adhere to them through α3- and α6-containing integrins

PURPOSE. Retinal diseases are often accompanied by changes in the structure of the multilayered extracellular matrix underlying the retina, Bruch's membrane (BrM). These structural revisions potentially lead to alterations in retinal pigment epithelium (RPE) adhesion, likely via modification of interactions with extracellular matrix (ECM) proteins including laminins in BrM. The purpose of this study was to identify specific laminins in BrM and their receptors in RPE cells. METHODS. The laminin composition of BrM was determined using biochemical, molecular biological, and immunohistochemical techniques of rat, bovine, and human tissue and cell lines. An adhesion assay was used to test RPE attachment to laminins and the receptors used for this attachment. RESULTS. BrM contained laminin chains that could form laminin heterotrimers including laminins 1, 5, 10, and 11. RPE cells synthesized these laminin chains in vitro. Therefore, RPE cells may synthesize BrM laminins. The RPE cells preferentially adhered to potential BrM laminins. Although the cells adhered to the BrM component collagen IV, these cells preferentially adhered to laminins. Of the laminins tested, the RPE cells adhered preferentially to laminin 5. The cells interacted with these laminins via specific integrins and attained a different morphology on each laminin. In particular, the RPE cells rapidly attached and flattened on laminin 5. CONCLUSIONS. BrM contains specific laminins, and RPE cells express integrin receptors for those laminins. The interaction of these specific laminins and integrins most likely leads to differential behavior of RPE cells.