title: Short-term mechanical stress inhibits osteoclastogenesis via suppression             of DC-STAMP in RAW264.7 cells.
abstract: Mechanical stress is an important factor in bone homeostasis, which is maintained by a balance between bone resorption by osteoclasts and bone formation by osteoblasts. However, little is known about the effects of mechanical stress on osteoclast differentiation. In this study, we examined the effects of short-term mechanical stress on osteoclastogenesis by applying tensile force to RAW264.7 cells stimulated with receptor activator of nuclear factor-κB ligand (RANKL) using a Flexercell tension system. We counted the number of osteoclasts that were tartrate-resistant acid phosphatase (TRAP)-positive and multinucleated (two or more nuclei) with or without application of mechanical stress for 24 h. Osteoclast number was lower after mechanical stress compared with no mechanical stress. Furthermore, mechanical stress for up to 24 h caused downregulation of osteoclast-specific gene expression and fusion-related molecule [dendritic cell specific transmembrane protein (DC-STAMP), osteoclast stimulatory transmembrane protein (OC-STAMP), E-cadherin, Integrin αV and Integrin β3] mRNA levels. Protein expression of DC-STAMP decreased with mechanical stress for 24 h compared to the control without mechanical stress, whereas the expression of E-cadherin, Integrin αV and Integrin β3 was slightly decreased. Nuclear factor of activated T cells c1 (NFATc1) mRNA levels were decreased at 6 h and increased at 12 and 24 h compared with the control. The levels of NFATc2, NFATc3 mRNA did not change compared with the control group. By contrast, mechanical stress for 24 h significantly enhanced NFAT transcriptional activity compared with the control, despite a decrease in DC-STAMP mRNA and protein levels. These results suggest that short-term mechanical stress strongly inhibits osteoclastogenesis through the downregulation of DC-STAMP and other fusion-related molecules and that short-term mechanical stress induces a negative regulatory mechanism that cancels the enhancement of NFAT transcriptional activity.
authors.affiliation: Department of Orthodontics, Hokkaido University Graduate School                     of Dental Medicine, Sapporo 060-8586, Japan.
authors.forename: Sumika
authors.initials: S
authors.lastname: Kameyama
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kameyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikuiri
authors.forename: Mino
authors.initials: M
authors.lastname: Matsuno
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Deyama
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Suzuki
authors.forename: Junichiro
authors.initials: J
authors.lastname: Iida
mesh_terms: D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002452:Cell Count; D002454:Cell Differentiation; D002460:Cell Line; D015536:Down-Regulation; D018507:Gene Expression Regulation, Developmental; D039564:Integrin alphaV / Q000235:genetics / Q000378:metabolism; D039661:Integrin beta3 / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D009000:Monocytes / Q000166:cytology / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology* / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D013314:Stress, Mechanical
chemical_list: D015820:Cadherins; C499636:DC-STAMP protein, mouse; D039564:Integrin alphaV; D039661:Integrin beta3; D008565:Membrane Proteins; D050778:NFATC Transcription Factors; D009419:Nerve Tissue Proteins; D053245:RANK Ligand; D012333:RNA, Messenger