神経誘導因子Netrin-1は軟骨形成や骨形成においてBMPまたはNogginにより調節される

This is the first report describing neurogenic factor of Netrin-1 related to chondrogenesis or osteogenesis in a human cells. Netrin is a morphogenetic factor that induces a growth cone of an axial filament of the nervous system. However, the roles of Netrin in chondrogenesis or osteogenesis are not yet understood. We analyzed the relationship between Netrin and bone morphogenetic protein-2 (BMP-2) in chondrogenesis or osteogenesis, using a human chondrocyte-like cell line (USAC), which also retains multi-potency to differentiate into osteoblasts and adipocytes. Netrin-1 mRNA was decreased in USAC cells, though the expression was increased during osteogenic differentiation at the stage when osteocalcin mRNA were increased by BMP-2. Furthermore, inhibition of Netrin-1 gene increased Cbfa1 mRNA expression, and decreased Sox9 mRNA expression. We also found that Netrin-1was strongly expressed in immature chondrocytes of cartilage-like tissues that were formed in an exo vivo experiment with diffusion chambers. The se findings indicate that Netrin-1 and BMP-2 regulates in the stage dependent process of mesenchymal cell differentiation to chondrocytes or osteoblasts.骨芽細胞または脂肪細胞への分化多能を保持するヒト軟骨細胞様細胞系(USAC)を用い、軟骨形成または骨形成におけるNetrinと骨形成蛋白質-2(BMP-2)との関係を調べた。Netrin-1 mRNAはUSAC細胞中では減少するが、オステオカルシンmRNA濃度がBMPによって上昇する際の骨芽細胞分化時にNetrin-1 mRNAの発現が増加した。Netrin-1遺伝子を阻害すると、Cbfal mRNA発現は増加しSox9 mRNA発現は減少した。またNetrin-1は軟骨様組織の未成熟軟骨細胞において強く発現した。Netrin-1とBMP-2が、間葉細胞の軟骨細胞または骨芽細胞へ分化プロセスを制御すると考えた

Atelocollagen enhanced osteogenesis in a geometricstructured beta–TCP scaffold by VEGF induction.

In order to establish the convertibility of a host for bone augmentation, we herein developed a new honeycombshaped β-tricalcium phosphate (37H) using atelocollagen as a scaffold, which exhibited unique geometric properties for in vitro and in vivo studies.Human mesenchymal stem cells (MSC) were cultured with 37H or atelocollagen-coated honeycomb-shaped β-tricalcium phosphate (Col37H), and their osteoblastic differentiation was then analyzed. Atelocollagen promoted cell adhesion and formation of vessel-like structures in the tunnels of scaffolds of cultured MSC. The mRNA expression levels of type I collagen, osteocalcin, and VEGF were greater in MSC cultured with Col37H than with 37H. Bone generation with Col37H in the rat calvaria was greater than with 37H, and this was attributed to early vessel construction. A large number of blood vessels invaded tunnels from the periosteum and existing bone surface. A strong VEGF signal was detected immediately before the new bone surface in the tunnels of Col37H. These results indicate that the addition of atelocollagen to Col37H has potential in the construction of functional artificial bone

A case of mandibular fracture including coronoid process fracture

The incidence of mandibular fractures is the highest among facial bone fractures. Addi-tionally, most of mandibular fractures occur in the mandibular angle and condylar process. On the other hand, the incidence of fracture of coronoid process is extremely low. We experienced a case of mandibular fractures involving mandibular body, condylar process as well as the coronoid process in a man aged 3₉–years–old who had received strong direct external force to the mandible. Mandibular fractures usually occur in the condylar process and mandibular angle because direct external force is more likely to transmit to these re-gions. Based on the classification of mandibular fractures, the incidence of mandibularfractures involving coronoid process increases with an increased number of fractures lines that means complicated fracture. At the viewpoint of anatomical portion, direct external force dose not transmit to coronoid process; however, it is possible that direct external force may transmit coronoid process in the case of complicated fracture. In this case report, we considered the potential mechanism of fracture of coronoid process by using a three–dimensional finite element model of a human mandible stress distribution analysis

Biochemical Mechanism of Titanium Fixation into Living Bone: Acid Soluble Phosphoproteins in Bone Binds with Titanium and Induced Endochondral Ossification in vivo

In 2014, we discovered that bone phosphoproteins, which are collectively called SIBULING family of proteins, are equipped with titanium-binding ability. Furthermore, the titanium implant devices which were coated with titanium-bound SIBLING induced more than 100 times faster bone formation of early stage when implanted into rat calvaria. These findings led us to an explanation why titanium implants could be fixed into living bone. Several other phosphoproteins including, phosvitin, caseins and phosphophoryn (a dentin phosphoprotein) were also found to bind with titanium by use of a chromatographic column packed with titanium beads. In this study we demonstrated that a typical phosphoprotein, phosvitin lost its titanium-binding ability in a time-dependent manner by the reaction with λ-protein phosphatase. The fact confirmed that certain specific phosphoserines λresidues in this protein were responsible for the titanium-protein interaction. For an additional confirmation of SIBLING-titanium interaction, we extracted bone and dentin proteins with a new and simple method of acidic condition and applied them to the chromatographic column packed with titanium beads. The results showed that definite portions of the acid soluble proteins from both bone and dentin were retained in the column. Electrophoretic analysis showed the retained fractions were Stains-all positive, indicating that both bone and dentin contain multiple phosphoproteins which have affinity with titanium. The titanium-bound fraction of acid extract was again coated on the titanium device and implanted into rat calvaria. After one week, histology showed that in addition to definite pattern of bone formation, process of endochondral ossification was clearly observed. In the control implant of uncoated titanium device, only collagenous tissues were observed, without any cartilage nor bone formation. Based upon these findings we reconfirmed that the core biochemical mechanisms underlying the strong bond between the titanium and living bone is based upon the interaction between the implanted titanium and multiple bone phosphoproteins in the host tissue

Discovery of Ti-Binding Abilities of Phosphorylated-Chitin and -Collagen

Previously we have discovered that titanium (Ti) binds with bone phosphoproteins SIBLING protein family, by using a Ti beads chromatography. Furthermore, we showed that the isolated bone phosphoproteins remarkably enhanced bone formation when we coated the Ti device with them and implanted into rat calvaria. Therefore, we have called the Ti-binding bone phosphoproteins as “the implant proteins.” This discovery encouraged us to create a new biomolecule that can simulate the functions of the implant proteins. Since significant characteristics of the implant proteins are the presence of multiple phosphate groups and the occurrence of single cell-adhering RGD sequence, we decided for the first place to phosphorylate chitin and collagen to see whether they acquire or increase Ti-binding ability. Results showed that more than 70% of phosphorylated chitin bound with Ti, and phosphorylated collagen enhanced about 7% of its Ti-binding ability. These modified biomolecules, P-chitin and P-collagen will become highly useful for new development of Ti-related bone regenerative medicine

Phosphorylated chitin increased bone formation when implanted into rat calvaria with the Ti-device

BACKGROUND: Previously we found that a group of phosphorylated proteins (SIBLINGs) in bone binds with the Ti-device, and increases the early bone formation around the Ti-implants remarkably. From these results, we explained the biochemical mechanism of a strong bond between living bone and Ti, which was discovered by Branemark and colleagues. For the clinical application of our findings, we need a large amount of these proteins or their substitutes. OBJECTIVE: We aimed to create a new molecule that equips with essential functions of SIBLINGs, Ti-binding, and bone enhancement around the Ti implant. METHODS: We chemically phosphorylated chitin and obtained a soluble form of phosphorylated chitin (P-chitin). In this solution, we immersed the Ti-devices of web-form (TW) which we previously developed and obtained the P-chitin coated TWs. Then we tested the P-chitin coated TWs for their calcification ability in vitro, and bone enhancing ability in vivo, by implanting them into rat calvaria. We compared the P-chitin coated TW and the non-coated TW in regard to their calcification and bone enhancing abilities. RESULTS: Ti-devices coated with phosphorylated-chitin induced a ten times higher calcification in vitro at 20 days, and four times more elevated amount of bone formation in vivo at two weeks than the uncoated Ti-device. CONCLUSIONS: Phosphorylated chitin could be a partial substitute of bone SIBLING proteins and are clinically applicable to accelerate bone formation around the Ti implants, thereby achieving the strong bond between living bone and Ti