SP7 Inhibits Osteoblast Differentiation at a Late Stage in Mice

RUNX2 and SP7 are essential transcription factors for osteoblast differentiation at an early stage. Although RUNX2 inhibits osteoblast differentiation at a late stage, the function of SP7 at the late stage of osteoblast differentiation is not fully elucidated. Thus, we pursued the function of SP7 in osteoblast differentiation. RUNX2 induced Sp7 expression in Runx2−/− calvarial cells. Adenoviral transfer of sh-Sp7 into primary osteoblasts reduced the expression of Alpl, Col1a1, and Bglap2 and mineralization, whereas that of Sp7 reduced Bglap2 expression and mineralization at a late stage of osteoblast differentiation. Sp7 transgenic mice under the control of 2.3 kb Col1a1 promoter showed osteopenia and woven-bone like structure in the cortical bone, which was thin and less mineralized, in a dose-dependent manner. Further, the number of processes in the osteoblasts and osteocytes was reduced. Although the osteoblast density was increased, the bone formation was reduced. The frequency of BrdU incorporation was increased in the osteoblastic cells, while the expression of Col1a1, Spp1, Ibsp, and Bglap2 was reduced. Further, the osteopenia in Sp7 or Runx2 transgenic mice was worsened in Sp7/Runx2 double transgenic mice and the expression of Col1a1 and Bglap2 was reduced. The expression of Sp7 and Runx2 was not increased in Runx2 and Sp7 transgenic mice, respectively. The expression of endogenous Sp7 was increased in Sp7 transgenic mice and Sp7-transduced cells; the introduction of Sp7 activated and sh-Sp7 inhibited Sp7 promoter; and ChIP assay showed the binding of endogenous SP7 in the proximal region of Sp7 promoter. These findings suggest that SP7 and RUNX2 inhibit osteoblast differentiation at a late stage in a manner independent of RUNX2 and SP7, respectively, and SP7 positively regulates its own promoter

Bioinspired mineralization of calcium carbonate in peptide hydrogel acting as a multifunctional three-dimensional template

Biomineralization is the process by which biominerals, minerals composed of bioinorganic matter possessing a controlled structure and orientation and a biomacromolecular assembly with an ordered structure that acts as a 3D template, are formed. In this study, we investigated the fabrication of organic/inorganic hybrid gels by bioinspired mineralization in peptide hydrogels. An Ac-(VHVEVS)3-CONH2 peptide was used as a multifunctional template with a mineral source supply capability and structural controllability that facilitates the formation of hydrogels via self-assembly. Hydrogels with varying viscoelastic strengths were prepared from the designed peptide by controlling the concentration of calcium ions added as cross-linking agents. The peptide hydrogel supplied carbonate anions as the mineral source through the hydrolysis of urea and mineralized CaCO3 with controlled morphology on the peptide network. With increases in the concentration of calcium ions added, the morphology of the mineralized CaCO3 changed from a fibrous structure to a thin film. This implies that the nucleation and growth mechanisms of CaCO3 formed by bioinspired mineralization were affected not only by the morphology and supply rate of the mineral source by the peptide network acting as a multifunctional template, but also by the viscoelastic strength of the hydrogel that served as a 3D reaction field

Pt/WO3 Nanoparticle-Dispersed Polydimethylsiloxane Membranes for Transparent and Flexible Hydrogen Gas Leakage Sensors

Hydrogen gas is a promising, clean, and highly efficient energy source. However, to use combustible H2 gas safety, high-performance and safe gas leakage sensors are required. In this study, transparent and flexible platinum-catalyst-loaded tungsten trioxide (Pt/WO3) nanoparticle-dispersed membranes were prepared as H2 gas leakage sensors. The nanoparticle-dispersed membrane with a Pt:W compositional ratio of 1:13 was transparent and exhibited a sufficient color change in response to H2 gas. The membrane containing 0.75 wt.% of Pt/WO3 nanoparticles exhibited high transparency over a wide wavelength range and the largest transmittance change in response to H2 gas among the others. The heat treatment of the particles at 573 K provided sufficient crystallinity and an accessible area for a gasochromic reaction, resulting in a rapid and sensitive response to the presence of H2 gas. The lower limit of detection of the optimized Pt/WO3 nanoparticle-dispersed membrane by naked eye was 0.4%, which was one-tenth of the minimum explosive concentration. This novel membrane was transparent as well as flexible and exhibited a clear and rapid color response to H2. Therefore, it is an ideal candidate sensor for the safe and easy detection of H2 gas leakage

Substitutional and interstitial impurity p-type doping of thermoelectric Mg2Si: a theoretical study

The narrow-gap magnesium silicide semiconductor Mg2Si is a promising mid-temperature (600–900 K) thermoelectric material. It intrinsically possesses n-type conductivity, and n-type dopants are generally used for improving its thermoelectric performance; however, the synthesis of p-type Mg2Si is relatively difficult. In this work, the hole doping of Mg2Si with various impurity atoms is investigated by performing first principles calculations. It is found that the Ag-doped systems exhibit comparable formation energies ΔE calculated for different impurity sites (Mg, Si, and interstitial 4b ones), which may explain the experimental instability of their p-type conductivity. A similar phenomenon is observed for the systems incorporating alkali metals (Li, Na, and K) since their ΔE values determined for Mg (p-type) and 4b (n-type) sites are very close. Among boron group elements (Ga and B), Ga is found to be favorable for hole doping because it exhibits relatively small ΔE values for Si (p-type) sites. Furthermore, the interstitial insertion of Cl and F atoms into the crystal lattice leads to hole doping because of their high electronegativity