Yasushi Suetsugu

DNA microarray analysis of human gingival fibroblasts from healthy and inflammatory gingival tissues.

In the inflammatory gingival tissues of patients with periodontitis, cytokines such as interleukin (IL)-1 alpha, IL-1 beta, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha have been detected. Gingival fibroblasts are the major constituents of gingival tissue. We recently demonstrated that lipopolysaccharide (LPS) from periodontopathic bacteria induces inflammatory reactions in various tissues via CD14 and/or Toll-like receptors (TLRs) in gingival tissues [Biochem. Biophys. Res. Commun. 273 (2000) 1161]. To confirm this, we examined the expression of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF-alpha, CD14, TLR2, and TLR4 in human gingival fibroblasts (HGFs) obtained from patients with healthy or inflammatory gingiva using DNA microarray analysis. We also studied the expression levels of these proteins by flow cytometric analysis (FACS). The expression levels of all eight genes in the HGFs of the Inflammatory group were significantly higher than those in the Healthy group on DNA microarray analysis. FACS revealed that the expression levels of all eight proteins on the HGFs of the Inflammatory group were higher than those on the Healthy group. Our data indicated that these eight proteins in HGFs are involved in inflammatory conditions in the gingiva, including periodontal disease. Our results suggested that these eight proteins, in turn, act directly or indirectly on the immune response by activating host cells involved in inflammatory processes.

Biomimetic configurational arrays of hydroxyapatite nanocrystals on bio-organics

Biomimetic configurational arrays of hydroxyapatite (HAp) nanocrystals on several bio-organics, collagen (Col), chondroitin sulfate (ChS), and their mixture, were comparatively studied. The nanocomposites of HAp/Col, HAp/ChS, and HAp/Col/ChS were synthesized through a precipitation method with calcium hydroxide suspension and phosphoric acid solution containing Col, ChS, and their mixture, respectively. The (0 0 2) diffraction of the synthesized HAp crystals on a Col fiber showed an around 60 arching angle, while that on a ChS fiber showed just around 10 degrees. The same configurational arrays of HAp crystals could also be obtained on the mixture of Col and ChS fibers. The different electron diffraction patterns of the HAp crystals on the Col and ChS fibers were explained by the different macromolecular configurations of the Col and ChS fibrils which compose their fibers. The results may be applicable to develop a bone substitute which mimics the peculiar configurational arrays of HAp crystals found in bone and their detailed organic composition.

Novel Long-Term Immobilization Method for Radioactive Iodine-129 Using a Zeolite/Apatite Composite Sintered Body

The amount of radioactive iodine generated from nuclear power plants is expected to increase with the proliferation of nuclear energy production, and long-term immobilization methods for such radioactive elements need to be developed to make nuclear energy sustainable. The standard immobilization method of radioactive elements, vitrification, is not very effective for radioactive iodine-129 because of the low solubility of iodine in silicate melts, its very high volatility at standard vitrification process temperatures, and its instability in the alkaline environment of deep geological layers below 300 m. We have developed a novel three-phase ceramic composite produced by a sintering process. Iodine adsorbed onto Ca-type zeolite A was covered with a hydroxyapatite nanolayer through the exchange reaction of ammonium with calcium. Clusters of iodine of 30 nm within the zeolite structure were found to be thermally stable up to 1253 K because of the partial blockage of the alpha-cage apertures by ammonium ions and the partial change from a crystalline phase to an amorphous phase at 473 K. No gasification of iodine molecules was found to occur during the sintering process. The outer phase was highly crystalline hydroxyfluorapatite in which the hydroxyapatite nanolayer plays an important role for successful sintering. The elution of iodine in low-dioxygen water, similar to that found within the Earths crust, was investigated and was found to occur only in the surface layer of the sintered body.

Crystal growth and structure analysis of twin-free monoclinic hydroxyapatite

Single crystals of hydroxyapatite were grown by a flux method using Ca3(PO4)2 and Ca(OH)2 under 100 MPa of Ar gas. The crystals obtained had stoichiometric composition of Ca10(PO4)6(OH)2 and some of them were twin-free single crystals. From X-ray diffraction analyses, the space group was confirmed to be monoclinic P21/b with cell parameters a=0.9419(3) nm, b=1.8848(6) nm, c=0.6884(2) nm, and γ=119.98(2)°. The detailed crystal structure was determined with a reliability factor Rw=0.033; the O atoms of OH were located just on the 21 axis while the H atoms of OH occupied the positions a little deviated from the 21 axis. The origin of this structure was ascribed to the formation of hydrogen bonds between the H atoms of the OH ions and the specific O atoms of the PO4 ions.

Structural and Tissue Reaction Properties of Novel Hydroxyapatite Ceramics with Unidirectional Pores

Porous ceramics of hydroxyapatite was fabricated utilizing the crystal growth of thin ice columns parallel to one another in gelatin gel containing hydroxyapatite nanoparticles. The obtained ceramics possessed unidirectional pore channels with a porosity of around 75% and showed compressive strength of up to 13.1 MPa. As control materials, porous hydroxyapatite ceramics with a directionless pore structure were also fabricated by isotropic freezing and compared with the unidirectional samples regarding compressive strength and tissue reaction in vivo. Although the porosity and pore size distribution were similar, the compressive strength and new bone formation ability of the unidirectional samples were significantly greater than those of the random structured porous ceramics.

Compositional distribution of hydroxyapatite surface and interface observed by electron spectroscopy

The surfaces of single crystals and polycrystalline specimens of hydroxyapatite were measured by auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). Compared to P content, Ca content was found to be enriched near the surface of the hydroxyapatite single crystal. A Ca-deficient and carbonate-containing phase was observed at the grain boundaries of the polycrystalline specimen. Ca content at fracture surface increased as a function of time. It is suggested that Ca ions in the hydroxyapatite crystals migrated from inside the crystal to the surface, and that carbonate ions were incorporated from the gas phase into the crystal interior.

Bone Regeneration at Cortical Bone Defect with Unidirectional Porous Hydroxyapatite In Vivo

Unidirectional porous hydroxyapatite (UDPHAp) was developed which has microstructure in that cross sectionally oval pores 100 ~ 300µm in diameter penetrate through the material, and that is suitable for osteogenesis and angiogenesis.The porosity of the UDPHAp was 75 % and the compression strength was 14 MPa. A cortical bone defect was made at proximal tibia of Japanese white rabbit, and a trapezoidal prisms shaped UDPHAp was implanted. By histlogical evaluation, 2 weeks after implantation, new bone and new capillary was observed inside UDPHAp. Twelve weeks after implantation, new bone formation was observed in 41.6 % of the porous area. The results of this study suggest a great possibility of utilizing it in actual clinical setting as a bone substitution.

Bone Regeneration and Remodeling within a Unidirectional Porous Hydroxyapatite Bone Substitute at a Cortical Bone Defect Site: Histological Analysis at One and Two Years after Implantation

Unidirectional porous hydroxyapatite (UDPHAp) is an artificial bone substitute with a unique microstructure consisting of 100–300-µm oval pores that present the material unidirectionally. UDPHAp has a compression strength of 14 MPa and a porosity of 75%, which promotes cell migration and capillary formation within the material. Despite these advantageous properties, bone remodeling and bone formation with UDPHAp remain unclear. To examine long-term remodeling and differences in bone formation based on the defect site, trapezoidal prism-shaped UDPHAp blocks were implanted into rectangular-shaped cortical bone defects in the proximal tibia of Japanese white rabbits. Histological analysis performed at 52 and 104 weeks after implantation revealed that bone and capillaries had formed within the implanted UDPHAp material. Bone formed within the UDPHAp implanted in the cortical defect of rabbit tibia and remodel up to two years. The percentage of new bone area within UDPHAp was larger in cortical lesions than that in medullary lesions. These findings suggest that UDPHAp is a promising material for the repair of non-critical-sized cortical bone defects.

Inhibition of Nifedipine-induced Proliferation of Cultured Human Gingival Fibroblasts by Saireito, a Chinese Herbal Medicine

Saiko is predominantly contained in Saireito, a Chinese herbal medicine. The present study was conducted to determine whether or not Saiko is involved in the inhibition by Saireito of nifedipine-induced proliferation and collagen synthesis in gingival fibroblasts. Nifedipine (10 microM) significantly enhanced the proliferation starting on day 5 of the culture period. When added together with nifedipine, Saiko at concentrations of 0.05%-0.2% (w/v) dose-dependently inhibited the nifedipine-induced proliferation, and at the highest concentration tested (0.2%), Saiko inhibited the nifedipine-induced proliferation by about 40%. Moreover, Saiko (0.2%) also inhibited the normal proliferation at days 11 and 14. Sole application of nifedipine (10 microM) augmented the release of bFGF, and Saiko concentration-dependently reduced the level of bFGF in the nifedipine-containing culture medium. Nifedipine (10 microM) increased the production of type I collagen to almost twice that of the control (normal medium), and Saiko at concentrations above 0.1% significantly reduced the nifedipineinduced production of collagen. In conclusion, the present findings demonstrate that Saiko inhibited the nifedipine-induced proliferation of gingival fibroblasts by reducing the release of bFGF and that Saiko is involved in the Saireito-induced inhibition of nifedipine-stimulated proliferation and collagen synthesis in gingival fibroblasts.

Study of the Mechanical Properties of a Novel Unidirectional Porous Hydroxyapatite Implanted in the Femoral Marrow of a Rabbit

The objective of this study was to assess the long-term stability and mechanical strength of a novel unidirectional porous hydroxyapatite (UDPHAp). Thirty-five Japanese white rabbits were used in the study. A cylindrical piece of UDPHAp was implanted in the femoral marrow. The animals were sacrificed 6, 12, 52 and 104 weeks after implantation. Compression strength was measured in a direction parallel to that of the unidirectional pores. The mean compression strength of the control sample before implantation was 13.4 MPa. The mean compression strength was 29.5 MPa, 43.5 MPa, 49.2 Mpa, 39.4 MPa and 45.8 MPa at 6, 12, 26, 52 and 104 weeks after implantation, respectively. Statistically significant differences were observed between the control samples and the implanted samples at all time points and between the implanted samples tested at 6 and 26 weeks after implantation. UDPHAp offers an advantage with regard to mechanical strength in that the compression strength in the direction parallel to that of the unidirectional pores increases at an early stage after implantation in the living bone tissue and is maintained for at least 2 years.