ALTERED INTERACTION OF HUMAN GRANULATION-TISSUE FIBROBLASTS WITH FIBRONECTIN IS REGULATED BY ALPHA-5-BETA-1 INTEGRIN

Granulation-tissue fibroblasts express an unique phenotype distinct fr om normal fibroblasts. Due to the importance of the cell-matrix intera ctions in the regulation of cell morphology and behavior, we have comp ared the cell adhesion apparatus, especially integrin-type receptors, in fibroblasts cultured from healthy human periodontal connective tiss ues and from chronic and wound granulation tissues. The spreading of g ranulation-tissue cells on fibronectin, but not on type I collagen or laminin, was slower when compared with the normal fibroblasts. Cell sp reading on fibronectin could be inhibited by RGD-containing peptide, s uggesting integrin-mediated interaction. Both cell types expressed bet a 1 integrin subunit, which associated with several integrin alpha sub units, namely alpha 1, alpha 2 alpha 3, alpha 5 and alpha v. In additi on to beta 1 subunit, alpha v chain formed heterodimers with beta 3 an d beta 5 subunits. Thus, these cells have multiple putative fibronecti n, laminin, collagen, and vitronectin receptors. Cell spreading of bot h cell types on fibronectin was inhibited with anti-beta 1 and anti-al pha 5 antibodies, but antibodies against other putative FN-binding int egrins (alpha 3, alpha v, and alpha v beta 3) had no effects. Furtherm ore, granulation-tissue fibroblasts showed delayed spreading on substr ates coated with anti-beta 1 or anti-alpha 5 integrin antibodies. On s ubstrates coated with anti-alpha 3 antibody, both cell types spread eq ually well. By FACS analysis, the amount of beta 1 and alpha 5 integri n subunits expressed on the cell surfaces was slightly elevated in GTF s compared with HGFs. Thus, the findings in this study indicate that t he weakened interaction of granulation-tissue fibroblasts with fibrone ctin is regulated by altered function of alpha 5 beta 1 integrin.