Low ozone concentrations promote <i>in vitro</i> preservation of explanted articular cartilage: an ultrastructural study

Ozone (O3) is an oxidizing natural gas widely applied as adjunctive therapeutic treatment for a variety of pathological conditions. Currently, O3-based therapies rely on the low-dose concept i.e., the administration of low O3 concentrations able to induce a mild oxidative stress stimulating antioxidant and anti-inflammatory response without causing cell damage. In addition, low O3 concentrations are thought to activate cellular and molecular mechanisms responsible for analgesic and regenerative effects. Due to these properties, in the last decade interest has arisen in the fields of orthopedics and regenerative medicine on the potential of O3 to counteract joint diseases involving cartilage degeneration. In this pilot study, we have explored the anti-degenerative potential of O3 on knee articular cartilage explanted from a healthy adult rabbit and maintained in vitro. Light and transmission electron microscopy were used to monitor chondrocyte and extracellular matrix features of cartilage samples undergoing O3 treatment every three days for two weeks. Results demonstrated that low O3 concentrations act on chondrocytes and the molecular components of the extracellular matrix of articular cartilage explants, significantly improving their preservation under in vitro conditions, likely by promoting both protective and pro-regenerative pathways. This opens promising perspectives for further investigations on the therapeutic potential of O3 for the treatment of cartilage degeneration not only as painkilling and anti-inflammatory agent but also as a cartilage regenerative agent.