title: Mechanical stress directly suppresses osteoclast differentiation in RAW264.7 cells.
abstract: Although it is known that mechanical stress to osteoblast and periodontal ligament cells suppresses osteoclast differentiation, little is known about the direct effect of mechanical stress on osteoclast differentiation. In this study, we examined the role of mechanical stress on osteoclast differentiation using murine pre-osteoclastic RAW264.7 cells treated with receptor activator of nuclear factor-kappaB ligand (RANKL). RAW cells were cultured with RANKL, and mechanical stress was applied for a given period. We counted the number of osteoclast cells which were tartrate-resistant acid phosphatase (TRAP)-positive and multinucleated (2 nuclei or more), and measured mRNA by RT-PCR. There was a decrease in the number of osteoclasts under mechanical stress compared with the number under no mechanical stress. The number of nuclei per osteoclast also decreased compared to the number of nuclei per osteoclast cultured with the application of mechanical stress. As the cells were cultured for a period of 1-7 days and/or for different periods of mechanical stress application, osteoclast differentiation decreased with mechanical stress and increased after removing mechanical stress. Expression of mRNA for the osteoclast-specific genes, TRAP, matrix metalloproteinase-9, cathepsin-K and calcitonin receptor, decreased with mechanical stress and was associated with the number of osteoclasts. Inducible nitric oxide synthase mRNA which inhibits osteoclast differentiation, increased with mechanical stress. In spite of the decrease in osteoclast number with mechanical stress, nuclear factor of activated T cell cytoplasmic 1 (NFATc1) and NFATc2 mRNA expression increased with mechanical stress. These findings indicate that mechanical stress directly suppresses osteoclast differentiation and increases NFATc1 and NFATc2 suggesting delayed differentiation.
authors.affiliation: Department of Oral Diagnosis and Oral Medicine, Hokkaido University Graduate School of Dental Medicine, Sapporo 060-8586, Japan.
authors.forename: Nobumitsu
authors.initials: N
authors.lastname: Suzuki
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Deyama
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Suzuki
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Kitagawa
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects; D053245:RANK Ligand / Q000494:pharmacology; D013314:Stress, Mechanical; D000071681:Tartrate-Resistant Acid Phosphatase; D013997:Time Factors
chemical_list: D007527:Isoenzymes; D053245:RANK Ligand; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase