BACKGROUNDBisphosphonates (BPs) have been reported to reduce local recurrence in giant cell tumor (GCT) of bone because of their osteoclast-suppressing effect; however, the optimal mode of delivery and the dose and duration of treatment of BPs remain to be established. To address these issues, it is first necessary to clarify the manner of action of BPs on osteoclasts. We herein evaluated the osteoclast-suppressing effect of sodium ibandronate in vitro.

METHODSMouse osteoclasts (OCLs) were generated in vitro using mouse bone marrow mononuclear cells. First, various concentrations of sodium ibandronate and equal amounts of phosphate-buffered saline were added to cell culture media. The number of multinucleated cells (over three nuclei) was recorded in each group, OCL formation was compared, and the most effective concentration of sodium ibandronate was determined. Then, high concentrations of sodium ibandronate were added to the experimental cell culture media; no ibandronate was given in the control group. Comparisons were made between the two groups in terms of OCL adhesion, migration, and bone resorption.

RESULTSOCL formation was suppressed by sodium ibandronate in vitro; the most pronounced effect was observed at the concentration of 10(-5) mol/L. OCL migration and bone resorption were significantly suppressed at this concentration, though there was no effect on OCL adhesion.

CONCLUSIONSSodium ibandronate was effective in suppressing OCLs and decreasing resorption in GCT. The strong anti-OCL effectiveness at a high concentration in vitro indicates a topical mode of application.