Tooth movement is a result of mutual physiologic responses between the periodontal ligament and alveolar bone stimulated by mechanical strain. The PDL cell and osteoblast are known to have an influence on bone formation by controlling collagen synthesis and alkaline phosphatase activation. Moreover, recent studies have shown that the PDL cell and osteoblast release osteoprotegerin (OPG) and the receptor activator of nuclear factor kappa B ligand (RANKL) to control the level of osteoclast differentiation and activation which in turn influences bone resorption. In this study, progressively increased, continuous tensional force was applied to PDL cells. The objective was to find out which kind of biochemical reactions occur after tensional force application and to illuminate the alveolar bone resorption and apposition mechanism. Continuous and progressively increased tensile force was applied to PDL cells cultured on a petriperm dish with a flexible membrane. The amount of PGE2 and ALP synthesis were measured after 1, 3, 6 and 12 hours of force application. Secondly, RT-PCR analysis was carried out for OPG and RANKL which control osteoclast differentiation and MMP-1, -8, -9, -13 and TIMP-1 which regulate the resolution of collagen and resorption of the osteoid layer. According to the results, we concluded that progressively increased, continuous force application to human PDL cells reduces PGE2 synthesis, and increases OPG mRNA expression.
Alkaline Phosphatase ; Bone Resorption ; Collagen ; Dinoprostone ; Humans ; Membranes ; Osteoblasts ; Osteoclasts ; Osteogenesis ; Osteoprotegerin* ; Periodontal Ligament ; RANK Ligand* ; Receptor Activator of Nuclear Factor-kappa B* ; RNA, Messenger* ; Tissue Inhibitor of Metalloproteinase-1 ; Tooth Movement

The hyperosmotic stimulus is regarded as a mechanical factor for bone remodeling. However, whether the hyperosmotic stimulus affects 1alpha, 25-dihydroxyvitamin D3 (1alpha,25(OH)2D3)-induced osteoclastogenesis is not clear. In the present study, the effect of the hyperosmotic stimulus on 1alpha,25(OH)2D3-induced osteoclastogenesis was investigated in an osteoblast-preosteoclast co-culture system. Serial doses of sucrose were applied as a mechanical force. These hyperosmotic stimuli significantly evoked a reduced number of 1alpha,25(OH)2D3-induced tartrate-resistant acid phosphatase-positive multinucleated cells and 1alpha,25(OH)2D3-induced bone-resorbing pit area in a co-culture system. In osteoblastic cells, receptor activator of nuclear factor kappaB ligand (RANKL) and Runx2 expressions were down-regulated in response to 1alpha,25(OH)2D3. Knockdown of Runx2 inhibited 1alpha,25(OH)2D3-induced RANKL expression in osteoblastic cells. Finally, the hyperosmotic stimulus induced the overexpression of TonEBP in osteoblastic cells. These results suggest that hyperosmolarity leads to the down-regulation of 1alpha,25(OH)2D3-induced osteoclastogenesis, suppressing Runx2 and RANKL expression due to the TonEBP overexpression in osteoblastic cells.
Bone Remodeling ; Coculture Techniques ; Down-Regulation ; Osteoblasts ; RANK Ligand ; Sucrose

OBJECTIVETo understand the mechanism of invasion by Legionella dumoffii.

METHODSThe L. dumoffii strain Tex-KL was mutated using the Tn903 derivative, Tn903dIIlacZ. After screening 799 transposon insertion mutants, we isolated one defective mutant. We then constructed the gene-disrupted mutant, KL16, and studied its invasion of and intracellular growth in HeLa and A549 cells, and in A/J mice survival experiments. The structure of traC-traD operon was analyzed by RT-PCR.

RESULTSThe transposon insertion was in a gene homologous to Salmonella typhi traC, which is required for the assembly of F pilin into the mature F pilus structure and for conjugal DNA transmission. Results from RT-PCR suggested that the traC-traD region formed an operon. We found that when the traC gene was disrupted, invasion and intracellular growth of L. dumoffii Tex-KL were impaired in human epithelial cells. When mice were infected by intranasal inoculation with a traC deficient mutant, their survival significantly increased when compared to mice infected with the wild-type strain..

CONCLUSIONOur results indicated that the traC-traD operon is required for the invasion and intracellular growth abilities of L. dumoffii Tex-KL in epithelial cells.

A549 Cells ; Animals ; Genes, Bacterial ; HeLa Cells ; Humans ; Legionella ; genetics ; physiology ; Male ; Mice ; Mutation ; Operon