title: Tensile strain increases expression of CCN2 and COL2A1 by activating TGF-β-Smad2/3 pathway in chondrocytic cells.
abstract: Physiologic mechanical stress stimulates expression of chondrogenic genes, such as multifunctional growth factor CYR61/CTGF/NOV (CCN) 2 and α1(II) collagen (COL2A1), and maintains cartilage homeostasis. In our previous studies, cyclic tensile strain (CTS) induces nuclear translocation of transforming growth factor (TGF)-β receptor-regulated Smad2/3 and the master chondrogenic transcription factor Sry-type HMG box (SOX) 9. However, the precise mechanism of stretch-mediated Smad activation remains unclear in transcriptional regulation of CCN2 and COL2A1. Here we hypothesized that CTS may induce TGF-β1 release and stimulate Smad-dependent chondrogenic gene expression in human chondrocytic SW1353 cells. Uni-axial CTS (0.5Hz, 5% strain) stimulated gene expression of CCN2 and COL2A1 in SW1353 cells, and induced TGF-β1 secretion. CCN2 synthesis and nuclear translocalization of Smad2/3 and SOX9 were stimulated by CTS. In addition, CTS increased the complex formation between phosphorylated Smad2/3 and SOX9. The CCN2 promoter activity was cooperatively enhanced by CTS and Smad3 in luciferase reporter assay. Chromatin immunoprecipitation revealed that CTS increased Smad2/3 interaction with the CCN2 promoter and the COL2A1 enhancer. Our results suggest that CTS epigenetically stimulates CCN2 transcription via TGF-β1 release associated with Smad2/3 activation and enhances COL2A1 expression through the complex formation between SOX9 and Smad2/3.
authors: Department of Orthopaedic Surgery, Science of Functional Recovery and Reconstruction, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama 700-8558, Japan. matino@md.okayama-u.ac.jp
authors: Takayuki
authors: T
authors: Furumatsu
authors: Emi
authors: E
authors: Matsumoto
authors: Tomoko
authors: T
authors: Kanazawa
authors: Masataka
authors: M
authors: Fujii
authors: Zhichao
authors: Z
authors: Lu
authors: Ryotaro
authors: R
authors: Kajiki
authors: Toshifumi
authors: T
authors: Ozaki
mesh_terms: D002460:Cell Line; D019902:Chondrocytes / Q000502:physiology*; D024043:Collagen Type II / Q000235:genetics*; D055513:Connective Tissue Growth Factor / Q000235:genetics*; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D006801:Humans; D055758:SOX9 Transcription Factor / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D013314:Stress, Mechanical; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D000099222:betaIG-H3 Protein
chemical_list: D024043:Collagen Type II; D055513:Connective Tissue Growth Factor; D016326:Extracellular Matrix Proteins; D055758:SOX9 Transcription Factor; D051899:Smad2 Protein; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D000099222:betaIG-H3 Protein; C526317:CCN2 protein, human; C499177:COL2A1 protein, human; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C527932:SOX9 protein, human