Low oxygen tension increased fibronectin fragment induced catabolic activities - response prevented with biomechanical signals

• Main Authors: Parker, E., Vessillier, S., Pingguan-Murphy, Belinda, Wan Abas, Wan Abu Bakar, Bader, D.L., Chowdhury, T.T.
• Format: Article
• Language: English
• Published: 2013
• Subjects: T Technology (General); TA Engineering (General). Civil engineering (General)
• Online Access: http://eprints.um.edu.my/9528/1/Low_oxygen_tension_increased_fibronectin_fragment_induced_catabolic_activities_-_response_prevented_with_biomechanical_signals.pdf; http://eprints.um.edu.my/9528/; http://www.ncbi.nlm.nih.gov/pubmed/24286132

Introduction: The inherent low oxygen tension in normal cartilage has implications on inflammatory conditions associated with osteoarthritis (OA). Biomechanical signals will additionally contribute to changes in tissue remodelling and influence the inflammatory response. In this study, we investigated the combined effects of oxygen tension and fibronectin fragment (FN-f) on the inflammatory response of chondrocytes subjected to biomechanical signals. Methods: Chondrocytes were cultured under free-swelling conditions at 1, 5 and 21 oxygen tension or subjected to dynamic compression in an ex vivo 3D/bioreactor model with 29 kDa FN-f, interleukin-1beta (IL-1 beta) and/or the nitric oxide synthase (NOS) inhibitor for 6 and 48 hours. Markers for catabolic activity (NO, PGE(2)), tissue remodelling (GAG, MMPs) and cytokines (IL-1 beta, IL-6 and TNF alpha) were quantified by biochemical assay. Aggrecan, collagen type II, iNOS and COX-2 gene expression were examined by real-time quantitative PCR. Two-way ANOVA and a post hoc Bonferroni-corrected t-test were used to analyse data. Results: Both FN-fs and IL-1 beta increased NO, PGE(2) and MMP production (all P < 0.001). FN-f was more active than IL-1 beta with greater levels of NO observed at 5 than 1 or 21 oxygen tension (P < 0.001). Whilst FN-f reduced GAG synthesis at all oxygen tension, the effect of IL-1 beta was significant at 1 oxygen tension. In unstrained constructs, treatment with FN-f or IL-1 beta increased iNOS and COX-2 expression and reduced aggrecan and collagen type II (all P < 0.001). In unstrained constructs, FN-f was more effective than IL-1 beta at 5 oxygen tension and increased production of NO, PGE(2), MMP, IL-1 beta, IL-6 and TNF alpha. At 5 and 21 oxygen tension, co-stimulation with compression and the NOS inhibitor abolished fragment or cytokine-induced catabolic activities and restored anabolic response. Conclusions: The present findings revealed that FN-fs are more potent than IL-1 beta in exerting catabolic effects dependent on oxygen tension via iNOS and COX-2 upregulation. Stimulation with biomechanical signals abolished catabolic activities in an oxygen-independent manner and NOS inhibitors supported loading-induced recovery resulting in reparative activities. Future investigations will utilize the ex vivo model as a tool to identify key targets and therapeutics for OA treatments.