[Mechanism of electroacupuncture in improving cartilage tissue injury in rats with knee osteoarthritis by regulating miR-335-5p expression].

Objectives: To observe the protective effect of electroacupuncture (EA) on the knee joint cartilage tissue of rats with knee osteoarthritis (KOA), so as to explore the potential mechanism of miR-335-5p involved in the treatment of EA for KOA.

Methods: A total of 42 adult male Sprague-Dawley (SD) rats were randomly divided into blank, model and EA groups, with 14 rats in each group. The model was established by injecting a sodium glutamate iodoacetate solution (80 μg/μL) into the right joint cavity. On the 15^th day after the model establishment, rats in the EA group received EA intervention at "Yanglingquan" (GB34) and "Xuehai" (SP10) on the right side, and the needles were retained for 15 minutes. The intervention was carried out every other day for a total of two weeks. After the two-week intervention, the paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) of the rats were detected;a gait analyzer was used to detect the gait adaptability changes induced by pain;the pathological changes of the knee joint cartilage tissue were observed after hematoxylin-eosin (HE) staining;qPCR and Western blot were used to detect the expression levels of miR-335-5p, Dickkopf related protein 1 (DKK-1), β-catenin, and matrix metalloproteinase 13 (MMP-13) mRNAs and proteins in the cartilage tissue respectively;immunofluorescence staining was used to observe the positive fluorescence expression of β-catenin in the right knee joint cartilage tissue.

Results: In the model group, HE staining showed a large area of chondrocyte necrosis, with the dissolution and disappearance of cell nuclei, accompanied by a macrophages-predominant inflammatory cell infiltration;cartilage surface defects in local areas, necrosis of trabecular bone and proliferation of fibrous tissue in local areas, and new capillary formation in the proliferative areas were also observed. In the EA group, pathological manifestations such as inflammatory cell infiltration and fibrous tissue proliferation were significantly alleviated. Compared with the blank group, the PWMT, PWTL, the support duration, footprint area, and average ground pressure of the right hind paw, and the mRNA and protein expressions of DKK-1 in the right knee joint cartilage tissue were decreased (P<0.001) in the model group, while the expressions of miR-335-5p, mRNA and protein expressions of β-catenin and MMP-13, and the fluorescence intensity of β-catenin in the right knee joint cartilage tissue were increased (P<0.001, P<0.01). All the above indicators in the EA group were all reversed (P<0.001, P<0.05, P<0.01) in comparison with the model group.

Conclusions: EA can significantly improve the pain symptoms of KOA rats, promote the recovery of motor function, and improve the pathological morphology of the knee joint cartilage tissue. This may be related to regulating the expression of miR-355-5p and Wnt/β-catenin pathway, as well as inhibiting the release of cartilage extracellular matrix-related degrading enzymes.