[Exploration on the mechanism of warm needle-moxibustion in protecting cartilage in rabbits with knee osteoarthritis based on the Hippo-YAP signaling pathway].

OBJECTIVES: To observe the effect of warm-needle moxibustion on the synthesis and catabolism of extracellular matrix (ECM) in chondrocytes by regulating the Hippo-YAP signaling pathway in rabbits with knee osteoarthritis (KOA), so as to explore its mechanisms underlying protection of knee cartilage.

METHODS: Male New Zealand rabbits were randomly divided into blank control, KOA model, warm-needle moxibustion (moxibustion), and medication groups, with 7 rabbits in each group. The KOA model was established by using the right hind limb knee joint extension position plaster fixation method. For rabbits of the moxibustion group, warm-needle moxibustion was applied to "Heding"(EX-LE2), "Neixiyan" (EX-LE4 ) and "Waixiyan" (ST35) for 15 min, once a day, for 14 d. The rabbits of the medication group received gavage of celecoxib (20 mg/kg) once a day for a total of 14 d. The degree of pain, swelling and limitation of movement function of the knee joint were assessed by using Lequesne MG score. The HE staining was used to observe the histopathological changes of knee cartilage tissue. The immunoactivity of Type Ⅱ collagen (COLⅡ) and Aggrecan in the knee cartilage was detected using immunohistochemistry. The expression levels of Yes-associated protein (YAP), box transcription factor 9 (SOX9), transforming growth factor-β1(TGF-β1), matrix metalloproteinase 3 (MMP-3), and adamalysin-like metalloproteinase with thrombospondin motifs 5 (ADAMTS5) mRNAs and proteins in the knee cartilage tissue were detected by using qPCR and Western blot, separately.

RESULTS: In contrast to the blank control group, the model group showed a significant increase in the Lequesne MG score, and the mRNA and protein expressions of MMP-3 and ADAMTS5 (P<0.01, P<0.05), and a considerable decrease in the immunoactivity of COLⅡand Aggrecan, and the mRNA and protein expression levels of YAP, SOX9, TGF-β1 (P<0.01, P<0.05). After intervention with warm needle-moxibustion and medication, the modeling induced increase and decrease of the levels of the indexes mentioned above were reversed (P<0.01, P<0.05). No significant differences were found between the moxibustion and medication groups in all the increased and decreased levels of the aforementioned indexes. Observation on changes of the gross morphological structure of the knee joint displayed that the surface of the knee joint in the model group is rough and dark, with obvious congestion, and HE staining showed apparent damage of the ECM, severe disruption of the tidal line and invasion of capillaries into the tidal line in the model group. These injury situations of the knee joint were relatively milder in both the moxibustion and medication groups, including bright joint surface, no obvious congestion in gross morphology, and relatively intact cartilage, and relatively uniform of the ECM, etc., in HE staining.

CONCLUSIONS: Warm needle-moxibustion can improve the pain reaction, swelling and movement function and protect the cartilage of knee joint in KOA rabbits, which may be related to its functions in regulating Hippo-YAP signaling, promoting the synthesis of cartilage ECM and inhibiting its degradation.