Polydatin protects against articular cartilage degeneration by regulating autophagy mediated by the AMPK/mTOR signaling pathway.

BACKGROUND: Knee osteoarthritis (KOA) is one of the leading causes of disability. Polydatin has a potential effect on KOA treatment but the therapeutic mechanism is not clear. This study aims to investigate the therapeutic action of polydatin in KOA and its mechanism in activating autophagy via the AMP-activated protein kinase (AMPK)/mTOR signaling pathway.

METHODS: After a KOA rat model was established by anterior cruciate ligament transection surgery, model rats were treated with polydatin 40 mg/kg for 30 days. Subsequently, cartilage tissues were collected, and hematoxylin-eosin (HE), Safranin-O, and TUNEL staining, and western blotting were performed to evaluate the pathological damage and autophagy-related protein expression. Then, human chondrocyte C28/I2 cells were stimulated with lipopolysaccharide (LPS), and the effects of polydatin on C28/I2 cell viability, apoptosis, and autophagy-related protein expression were detected by MTT, Flow Cytometry, and western blot. In addition, an AMPK inhibitor (Dorsomorphin 2HCl) was used to probe the cell proliferation and apoptosis of polydatin-administered C28/I2 cells.

RESULTS: Polydatin ameliorated the pathological damage in rat cartilage tissues and inhibited cell apoptosis in KOA rats. Meanwhile, in C28/I2 cells, polydatin promoted viability and reduced apoptosis. In addition, the protein expression of collagen II, LC3II/LC3I, Beclin-1, and p-AMPK/AMPK were upregulated, and p62 and p-mTOR/mTOR were downregulated by polydatin treatment. Interestingly, relative results showed that the protective effect of polydatin in LPS-stimulated-C28/I2 cells was blocked by the AMPK/mTOR inhibitor, dorsomorphin 2HCl.

CONCLUSION: Our research showed that polydatin reduced apoptosis and activated autophagy both in vivo and in vitro by the AMPK/mTOR signaling pathway to protect against KOA, which provided the basis for further investigation into the potential therapeutic impact of polydatin on KOA.