Surface Composition of Orthopaedic Implant Metals Regulates Cell Attachment, Spreading, and Cytoskeletal Organization of Primary Human Osteoblasts In Vitro

Abstract

The nature of orthopaedic implant surfaces affects the interaction between bone and the implant. To analyze this interaction at a cellular level, this study examined the early phase of cell adhesion to implant surfaces. Using an in vitro model, the cell adhesion of primary human osteoblasts cultured on Ti6A14V (Ti), CoCrMo (CC), and tissue culture polystyrene (PS) was characterized. The osteoblasts were found to adhere in greater numbers to Ti compared with PS and CC during a 12 hour period. Other cellular characteristics related to cell adhesion, such as cell spreading, cytoskeletal organization, and focal contact formation, were also examined. Osteoblasts cultured on Ti were significantly larger, and spread better, compared with those on PS and CC. Also, the rate of cytoskeletal reorganization was enhanced on Ti. Focal contacts remained peripherally located in cells on Ti and CC as cytoskeletal reorganization proceeded. However, for cells on PS, the focal contacts quickly became dispersed along actin filaments. There was no difference between surfaces in the number of cells forming focal contacts, although the cells used a larger percentage of their membrane to attach to CC. These data suggest that osteoblast attachment to Ti is greater because cell spreading and cytoskeletal organization are enhanced. Furthermore, the mechanisms of osteoblast attachment to the underlying substrate may be significantly different between biometals and tissue culture plastic. Substrate specific information regarding the characteristics and mechanisms of cell adhesion may be helpful in the design of implants to optimize bone growth at the interface.