A gene cluster for the synthesis of serotype g-specific polysaccharide antigen in Aggregatibacter actinomycetemcomitans.

Aggregatibacter actinomycetemcomitans is an important pathogen related to aggressively progressive periodontal breakdown in adolescents and adults. The species can be divided into six serotypes (a-f) according to their surface carbohydrate antigens. Recently, a new serotype g of A. actinomycetemcomitans was proposed. The aim of the present study was to sequence the gene cluster associated with the biosynthesis of the serotype g-specific polysaccharide antigen and develop serotype-specific primers for PCR assay to identify serotype g strains of A. actinomycetemcomitans. The serotype-specific polysaccharide (SSPS) gene cluster of the NUM-Aa 4039 strain contained 21 genes in 21,842-bp nucleotides. The similarity of the SSPS gene cluster sequence was 96.7 % compared with that of the serotype e strain. Seventeen serotype g genes showed more than 90 % homology both in nucleotide and amino acids to the serotype e strain. Three additional genes with 1,579 bp in NUM-Aa 4039 were inserted into the corresponding ORF13 of the serotype e strain. The serotype g-specific primers were designed from the insertion region of NUM-Aa 4039. Serotypes of the a-f strains were not amplified by serotype-specific g primers; only NUM-Aa 4039 showed an amplicon band. The NUM-Aa 4039 strain was three genes in the SSPS gene cluster different from those of serotype e strain. The specific primers derived from these different regions are useful for identification and distribution of serotype g strain among A. actinomycetemcomitans from clinical samples.

Micromolar Levels of Sodium Fluoride Promote Osteoblast Differentiation Through Runx2 Signaling.

Bone remodeling is a vital physiological process of healthy bone tissue in humans. Imbalances in this vital process lead to pathological conditions, including periodontal diseases. In this study, we characterized the effects of micromolar levels of NaF on the proliferation and osteogenic differentiation of MC3T3-E1 osteoblastic cells. NaF significantly enhanced the proliferation, alkaline phosphatase (ALP) activity, and mineralization of MC3T3-E1 cells. Quantitative real-time PCR analysis revealed that the expression of mRNAs encoding runt-related transcription factor 2 (Runx2), Osterix, Osteopontin and Osteocalcin was up-regulated in NaF-treated MC3T3-E1 cells compared with untreated controls. Western blot analysis demonstrated that Runx2 and Osterix were inhibited by Runx2 siRNA but were re-activated by treatment with NaF. Furthermore, in vivo evidence indicated that NaF protects against Porphyromonas gingivalis-induced periodontal inflammation and alveolar bone loss in a P. gingivalis-challenged experimental periodontitis animal model. These data suggest that NaF promotes the osteoblastic differentiation of MC3T3-E1 cells through the Runx2/Osterix pathway and may be effective for the treatment of bone-related disorders.

In vitro study of collagen coating of titanium implants for initial cell attachment.

The aim of this study was to examine the influence of collagen coating on titanium on the initial attachment of human gingival fibroblasts for the development of the implant with periimplant soft tissue attachment. The morphological changes of cultured human gingival fibroblasts were investigated by scanning electron microcopy (SEM). Four different surfaces, i.e. non-coated mirror-polished titanium, collagen-coated titanium, non-coated tissue-culture polystyrene, and collagen-coated polystyrene were examined. Collagen coating of titanium was effective for enhancing the initial cell attachment. It is expected that collagen coating of titanium implants will improve the attachment of the peri-implant soft tissue to titanium at early stages after the implantation. SEM observation revealed the morphological effect of collagen coating on both titanium and polystyrene surfaces. Many lamellipodia and filopodia were recognized on collagen-coated titanium or polystyrene. Collagen coating improved the activity of human gingival fibroblasts.