Abstract
Proper immune responses are critical for successful biomaterial implantation. Here, four scales of honeycomb-like TiO(2) structures were custom made on titanium (Ti) substrates to investigate cellular behaviors of RAW 264.7 macrophages and their immunomodulation on osteogenesis. We found that the reduced scale of honeycomb-like TiO(2) structures could significantly activate the anti-inflammatory macrophage phenotype (M2), in which the 90-nanometer sample induced the highest expression level of CD206, interleukin-4, and interleukin-10 and released the highest amount of bone morphogenetic protein-2 among other scales. Afterward, the resulting immune microenvironment favorably triggered osteogenic differentiation of murine mesenchymal stem cells in vitro and subsequent implant-to-bone osteointegration in vivo. Furthermore, transcriptomic analysis revealed that the minimal scale of TiO(2) honeycomb-like structure (90 nanometers) facilitated macrophage filopodia formation and up-regulated the Rho family of guanosine triphosphatases (RhoA, Rac1, and CDC42), which reinforced the polarization of macrophages through the activation of the RhoA/Rho-associated protein kinase signaling pathway.