Effect of electroacupuncture at Wnt/β-catenin signaling pathway on inhibiting cartilage degeneration in rats with knee osteoarthritis

Abstract

To explore the action mechanism of electroacupuncture (EA) for knee osteoarthritis (KOA) based on Wnt/beta-catenin (Wnt/β-catenin) signaling pathway. Ten rats were randomly selected into a sham-operation group among 50 male 2-month-old SD rats, and the KOA model was established in the remaining 40 rats by modified Hulth method. Four weeks after the model establishment, the rats were randomly divided into a model group, an experimental A group, an experimental B group and an experimental C group, 10 rats in each group. The rats in the sham-operation group and model group did not receive any intervention. The rats in the experimental A group were treated with EA at "Neixiyan" (EX-LE 4) and "Dubi"(ST 35) for 15 min. The rats in the experimental B group were treated with EA at "Neixiyan" (EX-LE 4) and "Dubi"(ST 35) for 30 min. The rats in the experimental C group were treated with EA at non-acupoint for 15 min. EA intervention was given once a day, five times a week, and totally 12-week treatment was given. After 12 weeks, the knee cartilage tissues were stained and the morphological changes were observed under light microscopy; the severity of cartilage degeneration was evaluated by modified Mankin's score; the content of interleukin-1β (IL-1β) in synovium tissues was detected by ELISA method; the content of Wnt-4, β-catenin and matrix metalloprotein-13 (MMP-13) in cartilage tissues was detected by Western blot method. Compared with the sham-operation group, in the model group the morphology and structure of cartilage were disordered, the number of cells was significantly reduced, the matrix was decontaminated and tidal line was incomplete; the Mankin's score was significantly increased (P<0.01), the content of IL-1β in synovium tissues were significantly increased (P<0.01), and the expressions of Wnt-4, β-catenin and MMP-13 at protein level were significantly increased (P<0.01). Compared with the model group, in the experimental A group and experimental B group the morphology and structure of cartilage were more orderly, the number of cells was increased, the matrix staining was deepened and the tidal line was more complete; Mankin's scores were decreased significantly (P<0.01); the contents of IL-1β in synovium tissues were decreased significantly (P<0.01), and the expressions of Wnt-4, β-catenin and MMP-13 at protein level were decreased significantly (P<0.01). Compared with the model group, no improvement was observed in the experimental C group. Compared with the experimental A group, in the experimental C group the morphology and structure of cartilage were disordered, the number of cells was significantly reduced, the matrix was decontaminated and the tidal line was incomplete; Mankin's score was significantly increased (P<0.01), the content of IL-1β in synovium tissues was significantly increased (P<0.01), and the expressions of Wnt-4, β-catenin and MMP-13 at protein level were significantly increased (P<0.01). The morphological structure of cartilage in the experimental B group was similar to that in the experimental A group, and there was no significant difference in Mankin's score, IL-1β content in synovium tissues and the expressions of Wnt-4, β- catenin and MMP-13 at protein level between the two groups (P>0.05). EA at "Neixiyan" (EX-LE 4) and "Dubi"(ST 35) may reduce the expression of MMP-13 and the production of inflammatory factor IL-1β through Wnt/β-catenin signaling pathway, thus inhibit the degradation of cartilage matrix and the apoptosis of chondrocyte, and improve the morphology and structure of cartilage.