Abstract
Chronic degenerative changes in cartilage and subchondral bone that lead to instability of the cartilage microenvironment are essential for the development of osteoarthritis (OA) in the old. Synchronous repair of cartilage and subchondral bone may be a key strategy for OA treatment. PDGF-BB effectively promoted chondrocyte regeneration and angiogenesis. However, the mechanisms by which PDGF-BB affects subchondral bone and the delivery of PDGF-BB to the joint cavity need to be further explored. In this study, we used sodium hyaluronate to deliver PDGF-BB (SH-PDGF) to the joint space and aimed to determine the mechanisms of SH-PDGF in repairing cartilage and subchondral bone and stabilising the cartilage microenvironment. In this research, we determined the pharmacokinetics of PDGF-BB and SH-PDGF in cartilage. Moreover, we investigated the effects of PDGF-BB and SH-PDGF on cartilage and the subchondral bone microenvironment by identifying changes in the HIF-VEGF-Notch axis and SDF-1-CXCR4 axis in an OA rat model. The results showed that PDGF-BB increased cell viability, decreased HIF-1α levels, inhibited inflammation and improved matrix metabolism in osteoarthritic chondrocytes under hyperoxic or hypoxic conditions. We also found that PDGF-BB and SH-PDGF showed similar effects on repairing cartilage and subchondral bone simultaneously. However, SH-PDGF had some advantages over PDGF-BB in prolonging the injection interval and decreasing the injection time. These protective effects were mediated by the inhibition of both the HIF-1α-VEGF-Notch axis and the SDF-1-CXCR4 axis. The underlying mechanisms include the inhibition of HIF-1α-VEGF-Notch-mediated vessel invasion and SDF-1-CXCR4 axis-mediated crosstalk between cartilage and subchondral tissue.