[Warm acupuncture stimulation improves cartilage damage and motor function by regulating JAK2/STAT3 signaling pathway in rabbits with knee osteoarthritis].

Objective: To observe the effect of warm acupuncture on the expression of Janus protein tyrosine kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway and inflammatory factors of articular cartilage in rabbits with knee osteoarthritis (KOA), so as to explore its underlying mechanisms in improving KOA.

Methods: New Zea-land rabbits were randomly divided into blank, model, warm acupuncture and medication groups (12 rabbits in each group). The KOA model was prepared by using the right hind limb tubular plaster extension fixation method. The rabbits in the warm acupuncture group received acupuncture of "Neixiyan"(EX-LE4),"Waixiyan"(ST35),"Heding"(EX-LE2) and "Zusanli"(ST36), followed by attaching an ignited moxa-stick segment to the acupuncture-handle. The treatment was conducted for 15 min, once a week for 4 weeks. The rabbits in the medication group received gavage of diclofenac sodium solution(0.35 mg/kg), once daily for 4 weeks. The dysfunction severity state of the rabbit's knee-joint was evaluated using Lequesne scale (0-3 points), and the histopathological changes of cartilage were observed under microscope after H.E. staining and the state of distribution of chondrocytes in different layers and the extracellular matrix was assessed using Mankin score (0-6 points). The contents of serum interleukin (IL)-6, tumor necrosis factor-α (TNF-α) and matrix metalloproteinase-9 (MMP-9) were measured by using ELISA, and the expression levels of p-JAK2/JAK2, p-STAT3/STAT3 and MMP-9 in knee cartilage tissue were detected using Western blot.

Results: Compared with the blank group, the Lequesne score, Mankin score, and the contents of serum IL-6, TNF-α and MMP-9, and the ratios of p-JAK2/JAK2 and p-STAT3/STAT3, and the expression level of MMP-9 protein in knee cartilage tissue were significantly increased in the model group (<0.01). In comparison with the model group, the Lequesne score, Mankin score, contents of serum IL-6, TNF-α and MMP-9, and the ratios of p-JAK2/JAK2 and p-STAT3/STAT3, and the expression of MMP-9 protein in knee cartilage tissue were notably decreased in both the warm acupuncture and medication groups (<0.01,<0.05). The levels of Lequesne score, Mankin score, contents of serum IL-6, TNF-α and MMP-9, and the ratios of p-JAK2/JAK2 and p-STAT3/STAT3 in knee cartilage tissue were significantly lower in the warm acupuncture group than in the medication group (<0.01, <0.05). No significant difference was found between the warm acupuncture and medication groups in the expression of MMP-9 protein (>0.05). Outcomes of H.E. showed injury of the perichondrium of knee joint, obvious reduction of the cartilage matrix staining, cystic changes, clustered and disordered arrangement and severe pyknosis and necrosis of the surface cells with reduction of number of cells and increase of vacuoles in the model group, which was milder in both warm acupuncture and medication groups.

Conclusion: Warm acupuncture can improve motor function and reduce cartilage injury in KOA rabbits, which may be related to its functions in inhibiting the secretion of pro-inflammatory factors and regulating JAK2/STAT3 signaling and downregulating MMP-9 expression in the cartilage tissue.