Effect of osteoprotegerin in combination with interleukin-6 on inhibition of osteoclast differentiation.

OBJECTIVE To observe the effect of recombinant interleukin-6 (IL-6) and osteoprotegerin (OPG) on inhibiting bone absorption induced by receptor activator for nuclear factor-kB ligand (RANKL) in murine osteoclast precursor cells (OCPs) model. METHODS RAW 264.7 cells were solely treated with 50 ng/ml RANKL for 1 day, and then they were divided into three groups: RANKL (control group), RANKL+IL-6 (IL-6 group) and RANKL+IL-6+OPG (combination group). These cells were harvested and investigated by means of HE staining under light microscope after consecutive 9 days. Furthermore, staining tartrate-resistant acid phosphatase(TRAP)-positive multinucleated cells were detected by inverted phase contrast microscope. The absorption pits of bone slices were observed under scanning electron microscope. RESULTS The number of mature osteoclast cells in control group was more than that in IL-6 alone or IL-6 combined with OPG group (P less than 0.05). Interestingly, this experiment has also demonstrated that there was a large number of TRAP-positive multinucleated osteoclasts (more than 3 nuclei) and several bone absorption formation in the control group, whereas the outcome was completely different in both IL-6 group and IL-6+OPG group (P less than 0.05). CONCLUSION IL-6 can suppress the differentiation of mature osteoclasts as directly adding it into the RAW 264.7 cells induced by 50 ng/ml RANKL, and further the effect of osteolysis is remarkably reduced. When treatment with IL-6 combined with OPG, a more effective strategy for the treatment of osteoporosis is reached.

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