ABSTRACT
BACKGROUND:Previous studies have found that electroacupuncture can delay articular cartilage degeneration mediated by JAK-STAT signaling pathway through upregulating the expression level of transforming growth factor β1 as well as mRNA expression levels of STAT3, Smad3 and LepR. In the meanwhile, electroacupuncture can inhibit the mRNA expression of p38 and Fas mRNA mediated by MAPK signaling pathways, further inhibiting the apoptosis of chondrocytes. OBJECTIVE: To explore the effect of electroacupuncture on the degeneration of articular cartilage in rats with knee osteoarthritis based on Ras-Raf-MEK1/2-ERK1/2 signaling pathway. METHODS:120 male healthy Sprague-Dawley rats aged 2 months olds were selected and randomly divided into normal, model, 15-minite electroacupuncture and 30-minute electroacupuncture groups (n=30 per group). The rats in the latter three groups received the intra-articular injection of 4% papain bilaterally, and the remaining rats received no intervention. At 2 weeks after modeling, the latter two groups were respectively given 15- and 30-minute electroacupuncture, five times weekly for consecutive 12 weeks. The morphology of the cartilage was observed by hematoxylin-eosin staining, the expression level of interleukin-1β in the synovium was detected by ELISA assay, and the protein expression levels of Ras, Raf, MEK1/2, ERK1/2, C-MYC, C-FOS, and C-JUN were detected by western blot analysis. RESULTS AND CONCLUSION: Hematoxylin-eosin staining showed that: in the model group, the cartilage surface was rough, the cartilage layer became thinner, and the cartilage structure was damaged with incomplete tidal line; in the 15- and 30-minute electroacupuncture groups, the cartilage structure was complete with clear layers and complete tidal line. ELISA showed that the expression level of interleukin-1β in the model group was significantly higher than that in the normal group (P< 0.01), and the level in the 15- and 30-minute electroacupuncture groups was significantly lower than that in the model group (P < 0.05). Western blot assay found that compared with the normal group, the protein expression levels of Ras, Raf, MEK1/2, ERK1/2, C-MYC, C-FOS, and C-JUN were increased in the model group. However, all above protein levels except ERK1/2 in the 15- and 30-minute electroacupuncture groups were significantly lower than those in the model group (P < 0.01,P < 0.05). To conclude, electroacupuncture inhibits the degeneration of articular cartilage in osteoarthritisvia Ras-Raf-MEK1/2-ERK1/2 signaling pathway and downregulating the expression level of interleukin-1β.