Primary human marrow stromal cells and Saos-2 osteosarcoma cells use different mechanisms to adhere to hydroxylapatite

One important step in bone formation on hard tissue implants is adhesion of osteoblast precursors to the implant surface. In this study, we used function-blocking antibodies against integrin subunits to characterize the mechanisms used by human marrow stromal cells and Saos-2 osteosarcoma cells to adhere to protein-coated hydroxylapatite (HA). We found that Saos-2 use both alpha(5)- and alpha(v)-containing integrins, whereas stromal cells use alpha(v)-containing integrins but not a.-containing integrins, despite the presence of alpha(5)-containing integrins on cell surfaces. On the basis of this difference, we examined binding of these cell types to HA coated with fibronectin (FN) or vitronectin (VN), to determine whether these ligands for alpha(5) and alpha(v) integrins could enhance the numbers or morphology of cells adhered to them. We also examined the adhesion of cells to HA coated with RGD peptides designed to bind to FN or VN receptors. Morphology and number of adherent stromal cells were markedly enhanced on serum-coated surfaces compared with IN or VN alone, whereas, surprisingly, Saos-2 cells failed to spread on serum-coated HA and displayed superior spreading and stress fiber formation,on VN-coated HA. Collectively, these results have important implications for the design of protein coatings to enhance the performance of HA implants. (C) 2003 Wiley Periodicals, Inc.