Kinetic study of the expression of beta-catenin, actin and vinculin during osteoblastic adhesion on grooved titanium...

Intercellular adhesions are known to play an important role in differentiation of osteoblasts and in the development of bone tissue architecture. However, to our knowledge, they have never been studied during the formation of bone tissue in contact with a biomaterial surface. In an in vitro kinetic study, we followed the expression of proteins involved in cell-cell interactions (beta-catenin), in cell-material interactions (vinculin) and in cytoskeleton (actin) of human osteoblastic cells cultured on grooved titanium-based substrates during 1, 2, 4, 6, 24, 48, and 72 hours. The human osteoblasts aligned themselves in the 150 microm wide grooves only after 24 hours. The distribution of vinculin-positive focal contacts, actin cytoskeleton and beta-catenin positive-adherens junctions was not significantly influenced by the cell alignment. beta-catenin-positive adherens junctions were expressed by human osteoblasts as soon as 1 hour after inoculation. At this time, they showed a patch-like aspect along cytoplasmic processes in contact with an underlying or an adjacent cell. After 2 hours, the patches were more and more numerous underlining the connections between cells. After 4 hours and more, the patches were organised in a parallel arrangement perpendicular to the two connected cells forming a "zip-like" aspect. Additionally, using double immuno-staining, we demonstrated that sometimes beta-catenin and vinculin appeared co-localised and sometimes not. The linkage of catenin/cadherin complex and vinculin-positive focal contacts with actin filaments may explain this apparent co-localisation.