title: Nuclear factor of activated T cells mediates fluid shear stress- and tensile strain-induced Cox2 in human and murine bone cells.
abstract: Mechanical loading such as interstitial fluid shear stress and tensile strain stimulates bone cells, which respond by changing bone mass and structure to maintain optimal skeletal architecture. Bone cells also adapt to bone implants and altered mechanical loading. Osseous integration between host bone and implants is a prerequisite for the stability of implants. Fluctuating fluid pressure and interfacial strains occur between bone cells and implants due to mechanical loading during walking and other daily activities. In this study, we examined the signaling mechanism by which mechanical stimulation activates a novel transcription factor in human and mouse bone cells. Nuclear factor of activated T cells (NFAT) is one of the transcription factors that act downstream of the Ca(++)/calcineurin (Ca(++)/Cn) network: a well-known pathway of inflammation. In this study, we hypothesized that NFAT2 is activated in response to mechanical stimulation and mediates Cox2 expression. Fluid shear stress and tensile strain results in nuclear translocation of NFAT in cells of the osteoblastic lineage. A peptide inhibitor of the Cn/NFAT axis was found to block the mechanical stimulation-mediated Cox2 induction. Further, chromatin immunoprecipitation assay shows direct interaction between NFAT2 and the human Cox2 promoter region. Additionally, CnAbeta knockout calvarial bone cells were found to be less sensitive than control bone cells to mechanical stimulation. Our study provides new evidence for a novel role for NFAT in bone mechanotransduction in the context of cytokine gene induction in bone cells.
authors.affiliation: Department of Orthopaedic Surgery, Columbia University Medical Center, 630 W 168th Street, Black Building 14-1412, New York, NY 10032, USA.
authors.forename: Ayse B
authors.initials: AB
authors.lastname: Celil Aydemir
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Minematsu
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Gardner
authors.forename: Kyung Ok
authors.initials: KO
authors.lastname: Kim
authors.forename: Jae Mok
authors.initials: JM
authors.lastname: Ahn
authors.forename: Francis Young-In
authors.initials: FY
authors.lastname: Lee
mesh_terms: D000818:Animals; D015153:Blotting, Western; D047369:Chromatin Immunoprecipitation; D019295:Computational Biology; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D050778:NFATC Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D013314:Stress, Mechanical
chemical_list: D050778:NFATC Transcription Factors; D009842:Oligopeptides; C121611:VIVIT peptide; D051546:Cyclooxygenase 2