Papers by Author: Osamu Suzuki

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Authors: Yoshitomo Honda, Shinji Kamakura, Takashi Kumagai, Osamu Suzuki
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.
Authors: Osamu Suzuki, Shinji Kamakura, Takahisa Anada
Abstract: The present study was designed to investigate the mechanism of in vivo conversion from synthetic octacalcium phosphate (OCP) into hydroxyapatite (HA) at ultrastructural level, where the implanted OCP is enhancing bone regeneration in mouse calvarial bone defect. OCP granules were implanted into the subperiosteal area of the calvaria of 7-week-old BALB/c mice for 3 weeks. Transmission electron microscopy of undecalcified frontal sections, obtained from the acrylic resin-embedded skull specimens showed that the bone crystals in newly formed bone directly bonded to the OCP particles implanted. The morphological characteristic of original plate-like OCP particles was remained unchanged even after the implantation, whereas a number of de novo nano-particles were also directly formed onto the plate-like OCP particles. Some of OCP particles were linked with other OCP particles through these nano-particles. The results suggest that the OCP-apatite conversion, involving the enhanced bone regeneration, advances via topotaxial conversion without changing the original OCP morphology, accompanied by solution-mediated de novo nano-apatite formation, in the vicinity of the implanted OCP particles.
Authors: Kentaro Suzuki, Takahisa Anada, Yoshitomo Honda, Koshi N. Kishimoto, Naohisa Miyatake, Masami Hosaka, Hideki Imaizumi, Eiji Itoi, Osamu Suzuki
Abstract: We have previously shown that synthetic octacalcium phosphate (OCP) displays highly osteoconductive and biodegradable characteristics. However, OCP cannot be sintered without thermal decomposition due to the existence of water molecules in the structure. The acquisition of the moldability and the improvement of the handling property in this material are subjects for the clinical use. In the present study, we prepared OCP complex with hyaluronic acid (Hya) that could be used in the injectable form and further examined the bone tissue reaction to cortical bone by placing the complex directly on an 8-weeks-old ICR mouse calvaria in comparison with the placement of OCP granules only. The granule form of OCP (between 300 to 500 μm in diameter) was mixed with sodium hyaluronic acid with molecular weights 90 x 104. The complex revealed an injectable characteristic if it was utilized in a syringe. After polytetrafluoroethylen ring was mounted on mouse calvaria, the inner space of the ring was filled with the complex and left the complex as it is for 6 weeks. Histological examination using the decalcified specimens indicated that the OCP/Hya complex exhibited greater bone formation than OCP granules only group within the ring at 6 weeks. The results suggested that the OCP/Hya complex could be used as an injectable and osteoconductive bone substitute material in many clinical situations.
Authors: Yoshitomo Honda, Shinji Kamakura, Kazuo Sasaki, Takahisa Anada, Taisuke Masuda, Osamu Suzuki
Authors: Shinji Kamakura, Kazuo Sasaki, Yoshitomo Honda, Taisuke Masuda, Takahisa Anada, Tadashi Kawai, Aritsune Matsui, Keiko Matsui, Seishi Echigo, Osamu Suzuki
Abstract: Our previous studies showed that synthetic octacalcium phosphate (OCP) enhances bone regeneration more than hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). Also, a synthetic bone substitute constructed of synthetic octacalcium phosphate (OCP) and porcine atelocollagen sponge (OCP/Col) showed stable bone regeneration. The present study was designed to investigate the difference of bone regeneration by OCP/Col and other calcium phosphate-collagen composites. OCP/Col, β-TCP$-collagen% composite (β-TCP/Col), or HA$-collagen% composite (HA/Col) sponge was prepared from pepsin-digested atelocollagen isolated from the porcine dermis and OCP, β-TCP, or HA granules, respectively. A standardized critical-sized defect was made in the rat calvarium, and various calcium phosphate-collagen composites were implanted into the defect. The rats were fixed at four weeks after implantation and radiographic and histological examinations were performed by undecalcified cross sections of implants. Radiographic examination showed that uniform radiopaque masses were observed in the created defects treated with OCP/Col, whereas granulous and foggy radiopacity was observed in β-TCP/Col and HA/Col. Histological examination showed that newly formed bone was observed in the reticulum of OCP/Col and around the implanted OCP. The regenerated bone by β-TCP/Col or HA/Col seemed to be less than that by OCP/Col and would not to be nucleated by the granules of β-TCP or HA. The present study indicated that bone regeneration by OCP/Col was different from those of β-TCP/Col and HA/Col. Application of OCP/Col would be expected for clinical use in the future.
Authors: Takahisa Anada, Akihiro Araseki, Shou Matsukawa, Tomokazu Yamasaki, Shinji Kamakura, Osamu Suzuki
Abstract: Our previous studies suggested that synthetic octacalcium phosphate (OCP) enhances bone regeneration more than hydroxyapatite (HA). However, the molecular mechanisms to induce osteogenic phenotype in osteoblast by OCP have not been identified. OCP tended to convert into an apatite structure in vivo and in vitro, and its process was accompanied by calcium consumption from the surrounding solution and the release of phosphate ions into the solution at a physiological condition. The present study was designed to investigate whether the dissolution of ionic products of OCP affects on proliferation and differentiation of mouse bone marrow stromal ST-2 cells in vitro. The number of cells treated with OCP-conditioned medium was slightly decreased in comparison to that of control at day 7. On the other hand, the level of alkaline phosphatase activity increased in OCP-conditioned medium. These results demonstrated that OCP is capable of inducing osteoblastic cell differentiation in ST-2 cells.
Authors: Osamu Suzuki, Takahisa Anada
Abstract: The characteristics and the biological responses of octacalcium phosphate (OCP) crystals, obtained in the presence of natural polymers, were summarized based on our studies reported. OCP obtained with collagen molecules in the solution had a plate-like morphology while OCP obtained with gelatin molecules in the solution exhibited elongated morphology toward long axis of the crystals. Oriented bone matrix formation was observed by the OCP inclusion in gelatin sponge in a critical-sized rat calvaria defect within the implantation periods around 8 weeks. It seems likely that specific crystal property of OCP obtained in distinct preparation conditions may affect bone tissue response probably through the modulation of OCP crystal characteristics.
Authors: Yusuke Orii, Hiroshi Masumoto, Takashi Goto, Yoshitomo Honda, Takahisa Anada, Keiichi Sasaki, Osamu Suzuki
Abstract: The surface oxide films were prepared by Electron Cyclotron Resonance (ECR) plasma oxidation on Ti substrates. Octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) peaks were formed after calcification by supersaturated calcium and phosphate solutions. Calcification ability was enhanced with increasing the oxidation time and the total pressure of ECR plasma treatment during oxidation. The results demonstrated that the calcium phosphate nucleation and the deposition can be controlled by various ECR plasma conditions.
Authors: Ryo Akatsuka, Ken Matsumura, Miyoko Noji, Chihiro Nishikawa, Kei Sato, Takayuki Hagiwara, Takahisa Anada, Osamu Suzuki, Tunemoto Kuriyagawa, Keiichi Sasaki
Abstract: This study aimed to create a thick hydroxyapatite (HAp) film on the surface of a human tooth by using a newly developed powder jet deposition (PJD) device for dental handpieces, and sought to examine the microstructural and mechanical properties of the resulting HAp film. The film was evaluated on three-dimensional view, surface roughness, Vickers hardness, and bonding strength before and after artificial aging through thermal cycling (555°C) for 500 cycles (30 sec for each cycle, 20 sec of dwell time).The HAp particles in the deposited film were densely packed, and the HAp films three-dimensional microstructure and its rough surface were maintained after thermal cycling. There was no significant difference in either the HAp films Vickers hardness or the bonding strength between the film and the enamel substrate before and after thermal cycling. The HAp films created in this study demonstrated excellent microstructural and mechanical properties even after the application of thermal stress. We demonstrated the possibility of using a new type of powder jet deposition (PJD) method we developed to form a new type of interface between the tooth and biomaterials. Consequently, we propose the use of this method in new dental treatments.
Authors: Shinji Kamakura, Takashi Kumagai, Yoshitomo Honda, Takahisa Anada, Keiichi Sasaki, Hidetoshi Shimauchi, Osamu Suzuki
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.
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