Purpose: To examine the adhesion of human trabecular meshwork cells with various extracellular matrix (ECM) proteins and to evaluate the roles and distribution of integrin receptors.
Methods: Cultured human trabecular meshwork cells were added to 96-well plates either uncoated or coated with proteins including fibronectin, laminin, and vitronectin, as well as collagen types I, III, IV, V, and VI. After incubation for 1 hour, the adhesion of cells was measured. Expression of cell surface integrins was determined by cell enzyme-linked immunoadsorbent assay (ELISA) and immunoprecipitation. Distribution was visualized by immunofluorescence staining using integrin-specific antibodies. For function perturbation and peptide inhibition studies, cells were preincubated with either integrin antibodies or synthetic peptides before the adhesion assays.
Results: Human trabecular meshwork cells attached to plates coated with ECM proteins in a dose-dependent manner. Fibronectin, vitronectin, and collagen types I and IV were the preferred ECM substrates. Cell ELISA revealed the presence of integrins alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, alpha v, beta 1, beta 3, beta 5, alpha 5 beta 1, and alpha v beta 3 and the absence of beta 2 and beta 4 on human trabecular meshwork cells. Results from immunostaining experiments were consistent with those from cell ELISA studies. Attachment of cells to ECM proteins was blocked by specific integrin antibodies. Cell adhesion to fibronectin and vitronectin was inhibited by peptides containing the Arg-Gly-Asp sequence.
Conclusions: Extracellular matrix proteins mediate the adhesion of human trabecular meshwork cells in culture. Integrin receptors appear to have functional roles in the cell-matrix interactions.