Advanced glycation endproducts interefere with integrin-mediated osteoblastic attachment to a type-I collagen matrix.

The adhesion of osteoblasts to bone extracellular matrix, of which type-I collagen constitutes >85%, can modulate diverse aspects of their physiology such as growth, differentiation and mineralisation. In this study we examined the adhesion of UMR106 rat osteoblast-like cells either to a control (Col) or advanced-glycation-endproduct-modified (AGEs-Col) type I collagen matrix. We investigated the possible role of different integrin receptors in osteoblastic adhesion, by co-incubating these cells either with beta-peptide (conserved sequence 113-125 of the beta subunit of integrins) or with two other peptides, RGD (Arg-Gly-Asp) and DGEA (Asp-Gly-Glu-Ala), which are recognition sequences for the alpha-subunits of alpha(1,5)beta(1) and alpha(2)beta(1) integrins. Collagen glycation inhibited the adhesion of UMR106 osteoblasts to the matrix (40% reduction versus Col, P > 0.001). beta-Peptide showed a dose- and glycation-dependent inhibitory effect on adhesion, and at a concentration of 100 microM decreased the attachment of UMR106 cells to both matrices (42% to Col, P<0.001and 25% to AGEs-Col, P<0.01). The synthetic peptides RGD (1mM) and DGEA (5mM) inhibited the attachment of UMR106 cells to Col (30 and 20%, P > 0.01 and P< 0.001, respectively), but not to AGEs-Col. beta-Peptide induced an increase in UMR106 cell clumping and a decrease in cellular spreading, while DGEA increased spreading with cellular extensions in multiple directions. These results indicate that both alpha and beta integrin subunits participate in osteoblastic attachment to type-I collagen, probably through the alpha(1,5)beta(1) and alpha(2)beta(1) integrins. AGEs-modification of type-I collagen impairs the integrin-mediated adhesion of osteoblastic cells to the matrix, and could thus contribute to the pathogenesis of diabetic osteopenia.