Osteoinduction in Novel Micropores of Partially Dissolved and Precipitated Hydroxyapatite Block in Scalp of Young Rats

Masaru Murata; Jun Hino; Md Arafat Kabir; Kenji Yokozeki; Michiko Sakamoto; Takehiko Nakajima; Toshiyuki Akazawa

doi:10.3390/ma14010196

Osteoinduction in Novel Micropores of Partially Dissolved and Precipitated Hydroxyapatite Block in Scalp of Young Rats

Materials (Basel). 2021 Jan 3;14(1):196. doi: 10.3390/ma14010196.

Authors

Masaru Murata¹, Jun Hino¹, Md Arafat Kabir¹, Kenji Yokozeki¹, Michiko Sakamoto², Takehiko Nakajima², Toshiyuki Akazawa³

Affiliations

¹ Division of Oral Regenerative Medicine, Health Sciences University of Hokkaido, Hokkaido 061-0293, Japan.
² HOYA Technosurgical Corporation, Tokyo 160-0004, Japan.
³ Industrial Technology Research Department, Hokkaido Research Organization, Hokkaido 060-0819, Japan.

Abstract

Osteoinduction in muscles by porous ceramics has been reported to be a real phenomenon. In this study, osteoinduction in connective tissues was found in highly porous hydroxyapatite (HAp) ceramics with large specific surface areas. We have developed the combination method of the partial dissolution-precipitation (PDP) technique involving the stirring-supersonic treatment in 1.7 × 10^-2 N HNO₃ solution containing Ca²⁺ and PO₄^3- to improve the surface and the bulk of commercially available synthetic HAp block (82.5% in porosity, 50-300 µm in pore size). The modified HAp was named as a partially dissolved and precipitated HAp (PDP-HAp). The PDP-HAp exhibited the porosities of 85-90%, the macropore sizes of 50-200 µm, and the specific surface areas of 1.0-2.0 m²/g, with microcracks. The aim of this study was to observe bone induction by the PDP-HAp with or without BMP-2 in scalp tissues of four-week-old rats. Young rats were divided into the PDP-HAp alone group and the PDP-HAp/BMP-2 group for a long-term observation. In the PDP-HAp group, bone induction occurred inside the many pores at nine months, and the ratio of induced bone was 12.0%. In the PDP-HAp/BMP-2 group, bone induction occurred in almost all pores at three months, and compact bone was found at nine months. The ratios of induced bone were 77.0% at three months and 86.0% at nine months. We believe that osteoinduction by the PDP-HAp might be different from the process of BMP-loaded HAp-induced bone formation, because the PDP-HAp has osteogenic microporous compartments with partially absorbable HAp crystals. The PDP technique may contribute to create bioceramics with osteoinductive property for bone regenerative medicine.

Keywords: BMP-2; HAp; bone; dissolution-precipitation; micropore; osteoinduction.