The aim of this study was to investigate the effect of Iguratimod (T-614) on rat knee osteoarthritis (KOA) and further to explore its underlying mechanism.
In this study, papain-induced KOA model was constructed. Hematoxylin and eosin (H&E) staining was conducted to observe the pathological changes of cartilage tissue and Mankin scoring principle was used for quantitative scoring. Transmission electron microscopy (TEM) was applied to observe the ultrastructure of cartilage tissue. ELISA was used to measure the levels of matrix metalloproteinase 13 (MMP-13) and inflammatory factors (interleukin (IL)-6 and tumor necrosis factor a (TNF-a)) in serum. RT-qPCR and immunohistochemistry were conducted to detect mRNA expression and protein expression of key genes in Wnt/β-catenin pathway.
H&E, Mankin scoring, and TEM data confirmed that compared with model group, T-614 significantly improved the degeneration of articular cartilage. Besides, we observed that low, middle, and high doses of T-614 could decrease the levels of MMP13, TNF-α, and IL-6 in serum to different degrees. Mechanically, T-614 downregulated the mRNA and protein expression of β-catenin and MMP13 in cartilage tissue via a dose-dependent manner, and on the contrary upregulated the mRNA and protein expression of glucogen synthase kinase-3 beta (GSK-3β).
Our results suggested that T-614 can reduce the level of its downstream target gene MMP-13 and downregulate the expression of inflammatory cytokines TNF-α and IL-6 by regulating the Wnt/β-catenin signaling pathway, thereby inhibiting joint inflammation and controlling KOA degeneration of articular cartilage.