Background: The activation of Wnt/β-catenin signalling promotes cellular senescence and induces matrix metalloproteinases (MMPs) expression in intervertebral disc (IVD). We investigated the effects of hyperbaric oxygen (HBO) on the Wnt/β-catenin signalling in degenerated human IVD cells and rabbit IVD models.
Methods: In vitro, nucleus pulposus cells (NPCs) were separated from the degenerated disc nucleus tissue by performing sequential enzymatic digestion. Control cells were maintained in 5% CO2 / 95% air. The hyperoxic cells were exposed to 100% O2 at 2.5 ATA in a hyperbaric chamber. The mRNA or protein levels of Wnt3a, β-catenin, aggrecan, type II collagen as well as MMP-3 and 9 were analyzed after HBO treatment. The translocation of β-catenin was detected by western blot after HBO treatment. In vivo, external axial loading in the rabbit IVD was used to induce the disc degeneration. After 14 days of mechanical loading, the custom-made external loading devices were removed. The HBO group was exposed to 100% oxygen at 2.5 ATM for 2 h daily. The control group was kept in housing cages with normal air. After 8 weeks, we investigated the effects of HBO on degenerated rabbit IVD by immunohistochemical assays.
Results: In vitro, the mRNA level of Wnt3a was down-regulated while that of aggrecan and type II collagen were up-regulated after HBO treatment. Western blot analysis showed decreased levels of translocated β-catenin in nucleus after HBO treatment. ELISA data showed HBO suppressed the expression of MMP-3 and MMP-9. In vivo, Safranin-O and TUNEL staining showed that mechanical loading induced IVD degeneration that increased proteoglycan (PG) lost and apoptosis of IVD. The levels of Wnt3a and β-catenin were down-regulated in degenerated disc tissue section after HBO treatment.
Conclusion: HBO treatment suppresses Wnt/β-catenin signalling and MMPs expression in degenerated human IVDs and rabbit model.
Disclosure: The authors declared no competing interests.