Non-weight-bearing exercise attenuates papain-induced knee osteoarthritis in rats via the TLR4/MyD88/NF-κB signaling pathway

Background and Aim Knee osteoarthritis (KOA) is characterized by joint wear and degeneration. Unfortunately, the medical community currently lacks effective treatment options for this disease. Suspension exercise therapy is considered an effective form of non-weight-bearing exercise for treating KOA. However, its mechanism of intervention in KOA is unclear. Therefore, this study aimed to evaluate the protective effects of non-weight-bearing exercise on rats with KOA and attempted to explore the underlying mechanisms. Methods In this study, a papain-induced KOA model was constructed, and the pathological changes in cartilage tissue were observed by hematoxylin and eosin (H&E) staining and scored according to the Mankin scoring principle. The serum levels of interleukin (IL)-1 beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha) were detected by enzyme-linked immunosorbent assay. Reverse transcription-quantitative polymerase chain reaction and Western blotting were used to detect the expression of mRNA and proteins in the TLR4/MyD88/NF-kappa B signaling pathway. Results H&E staining and Mankin score data confirmed that non-weight-bearing exercise significantly improved articular cartilage degradation compared with that in the model group. Further, we observed that non-weight-bearing exercise differentially reduced serum levels of IL-1 beta, IL-6, and TNF-alpha. Mechanistically, non-weight-bearing exercise downregulated gene and protein expression of TLR4, MyD88, and NF-kappa B in cartilage tissue. Conclusion Non-weight-bearing exercise resulted in the progression of KOA by modulating the TLR4/MyD88/ NF-kappa B signaling pathway and decreasing the levels of the inflammatory cytokines IL-1 beta, IL-6, and TNF-alpha to slow down the degeneration of articular cartilage.