Intra-articular injection of ozone on serum receptor activator for nuclear factor-κB ligand and osteo-protegerin level in collagen-induced arthritis rats

Objective To evaluate the clinical efficacy of intra-articular injection of ozone in collagen-induced arthritis (CIA) rats and to assess its effects on serum receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG) levels. Methods Forty weight age malched Wistar rats were randomly divided into normal control group (normal group), the CIA model group (CIA group), ozone (O3 group), and methotrexate (MTX group). In addition to the normal control group, Freund's complete adjuvant and bovine type Ⅱ collagen were injected to establish the rat model of CIA. After the model was sucessfully developed, double ankle injection concentration ozone group of 40 μg/ml of O3 each 1 ml, 1 times a week, a total of injection for 3 weeks for the experimenal group. MTX group of 0.9 mg/kg was injected 1 times a week for 3 weeks for the MTX group. Degree of foot swelling was measured, and radiographic assessment of arthritis index (AI) score was performed. One week after treatment, angular vein blood was collected for the rats after the intervention, flow multi-factor detection technology was used to test each rat. T test or Wilcoxon rank test was used to compare the difference between groups. Results ① After 3 week administration with O3, dcgree of foot swelling, and AI of the O3 group was reduced significanly than the CIA group during the same period (foot swelling degree: O3 group: (4.21±0.14) ml, CIA group (9.12±0.17) ml, T=64.08, P=0.00; AI O3 group: [(2.97±0.18) ml, CIA group: 5.76±0.13, T=37.24, P=0.00], and X-ray showed joint damage was alleviated. ② The serum level of RANKL in the CIA group was significantly higher than of the normal group [CIA model group 1 890.70(797.03, 10 571.94)], normal group [74.46(29.21, 95.37), T=43, P=0.005] during the same period; The serum level of RANKL in the O3 group was significantly lower than the CIA group [O3 group 28.09(14.11, 207.30), CIA group 1 890.70(797.03, 10 571.94), T=39, P 0.05). ③ Serum RANKL/OPG of the CIA group was significantly higher than that of the normal group during this period, the difference was statistically significant [CIA group 250.68(42.33, 2 959.78), normal group 4.32(3.16, 5.30), T=36, P 0.05). Conclusion Intra-articular injection of concentration of 40 μg/ml of O3 can reduce RA rat joint swelling degree, which may relate to the mechanism that O3 can lower levels of serum RANKL and RANKL/OPG ratio, reduce osteoclast formation and activation. Key words: Ozone; Arthritis, experimental; Osteoprotegerin; Receptor activator for nuclear factor-κB ligand