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Abstract_Masanobu Kamitakahara

ABSTRACT

Calcium phosphate ceramics, such as hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂) and β-tricalcium phosphate (β-TCP, Ca₃(PO₄)₂), are widely used as artificial bones for bone repair because of their high biocompatibility to bone tissues. However, the calcium phosphate ceramics with higher bone-regeneration ability are desired because the present artificial bones show lower bone-regeneration ability than the autografts which are normally used in orthopaedic surgery. It is expected that the material design to be incorporated in bone metabolism is important to achieve the bone regeneration. In this presentation, the design to obtain the calcium phosphate ceramics incorporated in bone methabolism is shown.

By controlling the composition and microstructures of calcium phosphate ceramics, their properties of can be improved. In the case of HA, creating a Ca-deficient composition can increase its solubility. Additionally, controlling the morphology of HA crystals can lead to differences in the exposed crystal faces, which is expected to result in the control of protein adsorption. Ioku et al. revealed that the hydrothermal treatment of a-tricalcium phosphate (a-TCP) compacts or porous bodies can provide porous ceramics composed of Ca-deficient HA rod-like particles [1]. The hydrothermal treatment is useful to control the microstructure of porous HA ceramics [2]. We examined the in vivo behaviors of porous ceramics composed of Ca-deficient HA rod-like particles, and revealed that the ceramics showed excellent osteoconductive properties and biodegradability when implanted into rabbit femurs [3]. It is speculated that the control of composition and microstructure activated osteoclasts, thereby promoting bone regeneration [4]. The activation of osteoclasts may be related with the specific protein adsorption [5]. The obtained ceramics were incorporated in the bone metabolism by the activation of osteoclasts. We also revealed that the porous granules composed of Ca-deficient HA rod-like particles are useful to reduce the amount of autograft needed for the regeneration of large bone defects by combining Masquelet’s induced membrane technique [6]. In addition, the calcium phosphate cements with macropores and micropores can be obtained by binding these granules [7]. These calcium phosphate ceramics incorporated in bone metabolism are expected to be useful for bone regeneration.

References

1. Ioku, G. Kawachi, S. Sasaki, H. Fujimori, S. Goto, J. Mater. Sci., 41, 1341-1344 (2006).
2. Kamitakahara, C. Ohtsuki, G. Kawachi, D. Wang, K. Ioku, J. Ceram. Soc. Japan, 116, 6-9 (2008).
3. Okuda, K. Ioku, I. Yonezawa, H. Minagi, Y. Gonda, G. Kawachi, M. Kamitakahara, Y. Shibata, H. Murayama, H. Kurosawa, T. Ikeda, Biomaterials, 29, 2719-2728 (2008).
4. Morishita, E. Tatsukawa, Y. Shibata, F. Suehiro, M. Kamitakahara, T. Yokoi, K. Ioku, M. Umeda, M. Nishimura, T. Ikeda, Acta Biomaterialia, 39, 180–191 (2016).
5. Ikeda, M. Kasai, E. Tatsukawa, M. Kamitakahara, Y. Shibata, T. Yokoi, T.K. Nemoto, K. Ioku, J. Cell. Mol. Med., 18, 170-180 (2014).
6. Suzuki, M. Kamitakahara, W. Kihara, C. Xie, H. Kato, Y. Fukawa, M. Hamagaki, K. Aoki, S. Ichihara, M. Ishijima, T. Ikeda, T. Okuda, Scientific Reports, 15, 8304 (2025).
7. Kamitakahara, K. Asahara, H. Matsubara, J. Asian. Ceram. Soc., 10, 731-738 (2022).