OBJECTIVETo observe the effect of Icariin (ICA) on serum receptor activator of NFkappaB-ligand (RANKL)/osteoprotegerin (OPG) production and bone destruction in type II collagen-induced arthritis (CIA) rats.

METHODSThe CIA rat model was established in all rats, except those in the normal group (n = 8) using bovine type II collagen and complete Freund's adjuvant. Totally 24 CIA rats with arthritis index (AI) > or = 6 were selected and divided into the model group, the methotrexate (MTX) group, and the ICA group according to the AI score, 8 in each group. Normal saline was given to rats in the normal group and the model group by gastrogavage. MTX at the weekly dose of 5 mg/kg was given to rats in the MTX group. ICA at the daily dose of 20 mg/kg was given to rats in the ICA group. All medication lasted for 4 weeks. The AI scores were recorded once a week. Histomorphologic changes of the ankle joint were observed by HE staining. The bone destruction and the osteoporosis of the foot phalanx were detected by X-ray. Serum levels of RANKL and OPG were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTSAfter 4-week intervention, when compared with the model group, AI score and Larsen score were significantly lower, the serum RANKL concentration and the RANKL/OPG ratio obviously decreased, while the serum OPG concentration obviously increased in the CIA group (P < 0.05, P < 0.01). In the MTX group, the aforesaid indices decreased, but without statistical difference (P > 0.05). Results of HE staining indicated that hyperplasia of joint synovium, infiltration of inflammatory cells, and the degree of articular cartilage destruction were obviously alleviated in the ICA group.

CONCLUSIONICA could alleviate or lessen the degree of articular cartilage destruction in CIA rats, and its mechanism might be associated with reducing serum levels of RANKL and elevating levels of OPG, thus further decreasing the ratio of RANKL/OPG.