title: Oxygen tension modulates the effects of TNFα in compressed chondrocytes.
abstract: OBJECTIVE
  Oxygen tension and biomechanical signals are factors that regulate inflammatory mechanisms in chondrocytes. We examined whether low oxygen tension influenced the cells response to TNFα and dynamic compression.
  
  
  METHODS
  Chondrocyte/agarose constructs were treated with varying concentrations of TNFα (0.1-100 ng/ml) and cultured at 5 and 21 % oxygen tension for 48 h. In separate experiments, constructs were subjected to dynamic compression (15 %) and treated with TNFα (10 ng/ml) and/or L-NIO (1 mM) at 5 and 21 % oxygen tension using an ex vivo bioreactor for 48 h. Markers for catabolic activity (NO, PGE2) and tissue remodelling (GAG, MMPs) were quantified by biochemical assay. ADAMTS-5 and MMP-13 expression were examined by real-time qPCR. 2-way ANOVA and a post hoc Bonferroni-corrected t test were used to analyse data.
  
  
  RESULTS
  TNFα dose-dependently increased NO, PGE2and MMP activity (all p < 0.001) and induced MMP-13 (p < 0.05) and ADAMTS-5 gene expression (pp < 0.01) with values greater at 5 % oxygen tension than 21 %. The induction of catabolic mediators by TNFα was reduced by dynamic compression and/or L-NIO (all p < 0.001), with a greater inhibition observed at 5% than 21 %. The stimulation of GAG synthesis by dynamic compression was greater at 21 % than 5 % oxygen tension and this response was reduced with TNFα or reversed with L-NIO.
  
  
  CONCLUSIONS
  The present findings revealed that TNFα increased production of NO, PGE2and MMP activity at 5 % oxygen tension. The effects induced by TNFα were reduced by dynamic compression and/or the NOS inhibitor, linking both types of stimuli to reparative activities. Future therapeutics should develop oxygen-sensitive antagonists which are directed to interfering with the TNFα-induced pathways.
authors.affiliation: Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
authors.forename: R K
authors.initials: RK
authors.lastname: Tilwani
authors.affiliation: Biotherapeutics Group, National Institute for Biological Standards and Control, South Mimms, Potters Bar, Hertfordshire, EN6 3QG, UK.
authors.forename: S
authors.initials: S
authors.lastname: Vessillier
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, 50603, Malaysia.
authors.forename: B
authors.initials: B
authors.lastname: Pingguan-Murphy
authors.affiliation: Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
authors.forename: D A
authors.initials: DA
authors.lastname: Lee
authors.affiliation: Faculty of Health Sciences, Southampton General Hospital, University of Southampton, Southampton, SO16 6YD, UK.
authors.forename: D L
authors.initials: DL
authors.lastname: Bader
authors.affiliation: Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, UK. t.t.chowdhury@qmul.ac.uk.
authors.forename: T T
authors.initials: TT
authors.lastname: Chowdhury
mesh_terms: D000071116:ADAMTS5 Protein / Q000235:genetics; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D015232:Dinoprostone / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism; D053509:Matrix Metalloproteinase 13 / Q000235:genetics; D009569:Nitric Oxide / Q000378:metabolism; D010100:Oxygen / Q000502:physiology*; D013314:Stress, Mechanical; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D006025:Glycosaminoglycans; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D000071116:ADAMTS5 Protein; D053509:Matrix Metalloproteinase 13; D015232:Dinoprostone; D010100:Oxygen
keywords: Chondrocyte; Mechanotransduction; Osteoarthritis; Oxygen tension; TNF-α