Papers by Author: Takashi Kumagai

Abstract: The present study was designed to investigate whether bone morphogenetic protein-2 (BMP-2) adsorbed onto octacalcium phosphate (OCP) and hydroxyapatite (HA) surfaces influences osteoblastic cell differentiation. Osteoblastic cell line, UAMS32, were cultured on plastic plate that was coated of synthetic OCP and HA. BMP-2 was pre-adsorbed on these calcium phosphates at 4°C or room temperature for 24h. The cells more proliferated on the BMP-2 pre-adsorbed OCP and HA than that of the controls (OCP and HA coating without BMP-2). ALP activities were higher on HA than on OCP when BMP-2 were pre-adsorbed at 4°C than at room temperature. The results suggest that pre-adsorption of BMP-2 in different temperature affects osteoblastic cell differentiation, most probably through different adsorption state of BMP-2 on this calcium phosphate.

Abstract: Bone regeneration by calcium phosphates has been known to be intricately dependent on material properties or implanted milieu of host animals, such as site and species. Critical sized calvarial defects of mouse were recently used as the model for investigating bone regeneration ability and the mechanisms. The purpose of the present study is to investigate whether the critical sized mouse calvarial defects can be utilized to examine bone regeneration with synthetic octacalcium phosphate (OCP). OCP , prepared by wet synthesis methods, was sieved 0.3 ~ 0.5 mm in diameter and used for the animal experiment. At 14 days after surgery, histological examination showed that implantation of OCP grafted defects significantly enhanced bone formation compared with the control defect. OCP tended to convert to hydroxyapatite with time. The tartrate-resistant acid phosphatase (TRAP) positive osteoclastic cells were observed around the OCP particles. The results suggest that the mouse critical sized calvarial bone defects are useful model to investigate the bone formation by the OCP implantation.

Abstract: It has been shown that fluoride ions enhance OCP hydrolysis into Ca-deficient apatite and that fluoridation in hydroxyapatite (HA) affects osteoblast activity. The present study was designed to investigate whether fluoridated Ca-deficient apatite (F-HA) formed via OCP enhances bone regeneration. F-HA was obtained through hydrolysis of the OCP in a solution containing 2 ppm fluoride at 37 °C and pH 7.4. A standardized critical-sized defect was made in the rat calvarium, and granules of F-HA were implanted into the defect. Five rats from each group were fixed through four to twelve weeks after implantation. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) confirmed that F-HA corresponded well to apatite structure. In week four, new bone matrix was formed around F-HA. In week twelve of F-HA group, newly formed bone matrix was more abundant, whereas the implanted F-HA was unresorbed and still remained. A statistical analysis in week twelve showed that the newly formed bone in the defect with F-HA was higher than that with untreated group. The fact that new bone was directly formed on F-HA implant suggests F-HA formed via OCP could be used as a bone substitute material.