Formation of focal adhesions by osteoblasts adhering to different substrata.

In this study, the adhesion of an osteoblast cell line to glass and titanium surfaces coated with different extracellular matrix components has been examined. On uncoated glass or titanium surfaces, osteoblasts attached but failed to spread. On these surfaces the cells did not develop focal adhesions or stress fibers. Precoating glass coverslips or titanium disks with fibronectin enhanced spreading and resulted in the rapid formation of focal adhesions and their associated stress fibers. Osteoblasts also spread and developed focal adhesions and stress fibers on glass or titanium coated with serum. In this situation the spreading was less rapid than that on fibronectin. Following incubation with serum, we demonstrated that the surfaces became coated with vitronectin. On the vitronectin-coated surfaces, it was shown that the osteoblast focal adhesions contained integrins of the beta 3 family. In contrast, osteoblasts adhering to fibronectin-coated surfaces accumulated beta 1 integrins within their focal adhesions. The enhanced formation of focal adhesions by osteoblasts plated on surfaces coated with extracellular matrix proteins suggests that precoating titanium and other implant materials with extracellular matrix proteins may improve osseointegration.