Fire Needling Acupuncture Suppresses Cartilage Damage by Mediating Macrophage Polarization in Mice with Knee Osteoarthritis

Purpose: Macrophage polarization contributes to the mechanisms of treating knee osteoarthritis (KOA). In previous studies, fire needling acupuncture has been shown to affect KOA favorably. However, the mechanism of fire needling acupuncture on macrophage polarization is not well-defined. Thus, this study was conducted to determine that fire needling acupuncture exerts a therapeutic role in KOA by modulating macrophage polarization. Methods: Thirty mice were allocated at random into three groups of ten. The groups were labeled as "control", "model", and "fire needling acupuncture". Each group consisted of ten mice. From the second day of intra-articular injection MIA, the right "xiyan" (EX-LE5), "dubi" (ST35), "liangqiu" (ST34), and "xuehai" (SP10) acupoints were manipulated once every other day for two weeks in the fire needling acupuncture group. Mechanical withdrawal threshold and weight distribution were evaluated for behavioral testing in each group. The synovial morphology was monitored by HE staining. Pathological morphology was observed by HE staining, Saf-O staining, and toluidine blue staining. The polarization of macrophages in synovial tissue was detected using immunofluorescence (F4/80, CD86, and CD206). Results: Fire needling acupuncture increased the percentage weight-bearing difference and the mechanical withdrawal threshold, and improved synovial inflammation and cartilage damage in MIA-induced KOA mice. F4/80 and CD86 expression were downregulated by fire needling acupuncture, but CD206 was increased. Conclusion: Fire needling acupuncture decreases pain behaviors in KOA mice and improves synovial membrane injury and pathological cartilage damage. The macrophage polarization is involved in the mechanism of fire needling acupuncture's amelioration of articular cartilage damage.