Detection of transcripts for the receptor for macrophage colony-stimulating factor, c-fms, in murine osteoclasts

Macrophage colony-stimulating factor (M-CSF), whose action is restricted to the cell populations of the mononuclear phagocyte system, has recently been found to be required for osteoclastogenesis and bone resorption. To investigate the cells involved in the action of M-CSF in these processes, expression of c-fms mRNA, encoding the M-CSF receptor, was studied by in situ hybridization. Paws from murine embryos and newborn mice, tibiae from 2-day-old animals, as well as isolated osteoclasts, were hybridized with a c-fms-specific RNA probe. In bone, c-fms mRNA was detected only in cells at the late stages of osteoclastogenesis and in mature osteoclasts. The findings strengthen the relation between osteoclasts and the mononuclear phagocyte system. Furthermore, they suggest that M-CSF acts directly on osteoclast precursors and on mature osteoclasts during osteoclastogenesis.