Abstract
We investigated the regulatory effects of the macrophage migration inhibitory factor (MIF) on osteoclast formation. MIF plays an important role not only in the immune system, but also in cell proliferation and differentiation in a variety of organs. MC 3 T 3-E 1 cells and mouse bone marrow cells were cocultured, and formation of osteoclastic multinuclear cells was examined. MIF reduced the number of multinuclear cells differentiating from bone marrow cells. It was not due to either impairment of receptor activator of nuclear factor-kappa B ligand (RANKL) mRNA expression or activation of osteoprotegerin production in MC 3 T 3-E 1 cells. MIF almost completely suppressed the formation of mature osteoclasts while the total number of the nuclei of osteoclastic cells per well was unaffected. These results suggest that MIF inhibits formation of mature osteoclasts by preventing the multinucleation process.
