Preferred Orientation of Hydroxyapatite Ceramics Along the c-Axis Promotes Osteoblast Differentiation

Hydroxyapatite (HAp) is similar to the main inorganic components of bone and tooth enamel. Furthermore, it possesses biocompatibility, making it suitable for clinical use in artificial bones. This study aimed to verify whether the preferred orientation of HAp influences osteogenesis. Using the templated grain growth method, we successfully fabricated HAp ceramics with a preferred orientation to <i>m</i> (<i>a</i>)-planes (aHAp) and examined the effects of this orientation on bone differentiation. Osteosarcoma-derived osteoblasts (MG-63) were cultured on aHAp and HAp ceramics made from commercially available powder (iHAp). Electron backscatter diffraction analysis revealed the crystal orientation distribution of HAp ceramics and the numerous exposed <i>a</i>-planes of aHAp. The MG-63 cultured on aHAp exhibited significantly higher alkaline phosphatase activity, a marker of early bone differentiation, compared to iHAp. Furthermore, the two-dimensional electrophoresis results indicated that the expressed proteins differed between aHAp and iHAp. These results indicate that controlling HAp's crystal structure may promote the osteogenic potential of osteoblasts. In this study, we propose that the <i>a</i>-plane of HAp promotes bone differentiation during the early stages, presenting a promising approach for novel biomaterials, such as high-performance artificial bones.