RESUMO
BACKGROUND: Studies have shown that osteoclasts induce aberrant in growth of sensory nerves into the subchondral bone by secreting netrin-1, resulting in a reduced pain threshold in an osteoarthritis animal model. Therefore, we assume that inhibition of osteoclasts can alleviate sensory nerve-mediated pain symptoms. OBJECTIVE: To investigate whether artesunate inhibits subchondral bone osteoclasts and reduces sensory nerve-mediated pain, providing experimental data for the treatment of osteoarthritis pain using artesunate. METHODS: C57BL/6J male mice were randomly assigned to a sham operation group, a placebo group and an artesunate group, with 10 mice per group. The mice in the sham operation group were only subjected to right knee capsulotomy with no damage to the other structures. Moreover, there was no intervention after operation. In the other two groups, the mice received an anterior cruciate ligament transection of the right knee to establish the osteoarthritis model, followed by treatment with artesunate (artesunate group, 100 mg/kg per day) or equivalent volume of 5% NaHCO3 (placebo group) via intraperitoneal injection. Fourteen days after surgery, the footprint trial was performed, and the levels of tartrate-resistant acid phosphatase 5b (TRAcP5b), cathepsin K and carboxy-terminal telopeptide of type I collagen (CTX-I) in the peripheral blood were detected using ELISA. The knee joint specimens of each group were subjected to Safranin O-Fast Green staining, histological scoring, tartrate-resistant acid phosphatase (TRAP) staining and immunohistochemical staining with netrin-1 and calcitonin gene-related peptide (CGRP). RESULTS AND CONCLUSION: The percentage of ipsilateral contact area of the right hindpaw in the footprint trial was significantly higher in the sham operation group and artesunate group than the placebo group (P 0.05). No significant differences were observed in the serum levels of TRAcP5b, cathepsin K and CTX-I between the groups (P > 0.05). Based on the Safranin O-Fast Green staining, the cartilage histology score was significantly lower in the sham operation group and the artesunate group than the placebo group (P 0.05). TRAP staining indicated that compared with the placebo group, the Trap+ osteoclasts were significantly lower in the sham operation group and the artesunate group (P 0.05). Compared with the placebo group, the netrin-1+ and CGRP+ sensory nerves in the subchondral bone were significantly decreased in the sham operation group and the artesunate group (P 0.05). Our findings from this study indicate that artesunate improves sensory nerve-mediated pain by inhibiting netrin-1 secreted by subchondral bone osteoclasts, and has therapeutic potential to alleviate osteoarthritis pain.