ROCK-regulated synergistic effect of macropore/nanowire topography on cytoskeletal distribution and cell differentiation

Nanotopographical modification of implants has been proved to be a promising approach to inducing osteogenesis, which has also been utilized to promote the biological property of plasma sprayed titanium coating possessing macropores. However, less attention has been paid to the detailed process of cell-surface interaction and its mechanism especially related to the macro/nano structure. In this study, focus has been put on the early MC3T3 cell adhesion behaviors on macro/nano structured surfaces and its correlation with cell differentiation. A nanowire titanium (NT) structure has been produced by a hydrothermal method, and introduced onto a traditional plasma sprayed titanium coating (TPS) to obtain the nano-structured plasma sprayed titanium coating (NTPS). The results showed that the NT surface was beneficial for filopodia generation and cell spreading, while cells on the TPS surface could adapt themselves to the rough macroporous topography but poor spreading could be observed. The hierarchical NTPS surface was able to make a synergistic effect, with better cell spreading attributed to nano topography and multi-dimensional cytoskeleton distribution caused by the macroporous structure. Accordingly, different levels of cytoskeleton tension, with moderate Rho-associated kinase (ROCK) activity on NT and TPS but higher expression on NTPS could be observed. Consequently, NTPS had better differentiation performance compared to the NT and TPS surface. After ROCK was inhibited, the difference between all the groups diminished. It can be concluded that the better performance of NTPS in triggering cell differentiation may attribute to its higher cytoskeleton tension than NT and TPS, which was obtained by the synergistic effect of macro/nano-topography on cell spreading and cytoskeletal distribution.