Identification of macrophage migration inhibitory factor in murine neonatal calvariae and osteoblasts.

Bone resorption and formation are dynamic processes that occur in both normal and injured bone tissues. Regulation of these processes is mediated at the local level by cytokines and growth factors. Macrophage migration inhibitory factor (MIF) is one of the proinflammatory cytokines that activates macrophages and regulates production of other cytokines, such as tumour necrosis factor-alpha and interleukin-1. We here demonstrate, by reverse transcription-polymerase chain reaction, high expression of MIF mRNA in murine osteoblasts obtained from mouse neonatal calvariae and murine osteoblastic MC3T3-E1 cells. The presence of MIF protein in the osteoblasts was confirmed by Western blot analysis using anti-rat MIF antibody. Moreover, the immunohistochemical study revealed that MIF was localized largely in the cytoplasm. The pathophysiological function of MIF remains undefined; however, the present results suggest that MIF takes part in the osseous metabolism as well as in immunological events.