Background: Wnt/β-catenin signalling stimulates matrix catabolic activity in articular chondrocytes. However, little is known about the effects of hyperbaric oxygen (HBO) on the Wnt/β-catenin signalling in human osteoarthritic (OA) chondrocytes.
Methods: OA chondrocytes were separated from the OA cartilages by performing sequential enzymatic digestion. Control cells were maintained in 5% CO2 / 95% air throughout the experiment. The hyperoxic cells were exposed to 100% O2 for 25 min and then to 5% CO2/95% air for 5 min at 2.5 ATA in a hyperbaric chamber. The mRNA or protein levels of low-density-lipoprotein receptor-related protein 5 (LRP-5), β-catenin, aggrecan, type II collagen as well as NO, MMPs, and ADAMTSs were analyzed after HBO treatment. The translocation of β-catenin from cytosol to nucleus after HBO treatment was detected by western blot. To determine the β-catenin-Tcf/Lef transcriptional activity, we measured the activity of Tcf/Lef reporter gene Topflash (optimal Tcf-binding site) or Fopflash (mutated Tcf-binding site) in OA chondrocytes.
Results: The mRNA levels of TADAMTS4 and ADAMTS5 were down-regulated while that of aggrecan and type II collagen were up-regulated in OA chondrocytes after HBO treatment. ELISA data showed decreased proteins expression of NO, MMP3, MMP9, and MMP13 in OA chondrocytes after HBO treatment. The relative density ratio (phosho-protein/protein) for LRP5 was down-regulated after HBO treatment. Western blot analysis showed decreased levels of translocated β-catenin after HBO treatment. There was decreased TOP flash activity following HBO stimulation, whereas the FOP flash activity was not affected. HBO decreased Tcf-dependent transcription and suppressed the expression of MMP-9.
Conclusion: HBO treatment suppresses Wnt/β-catenin signalling, ADAMTSs, and MMPs expression through LRP5 catabolic activity in human OA chondrocytes.
Disclosure: The authors declared no competing interests.