Abstract:

Objective: Both ODF (osteoclast differentiation factor, a newly identified member of the tumor necrosis factor super-family) and M-CSF (macrophage colony-stimulating factor) are indispensable for OC (osteoclast) formation. The purpose of this study was to test the possibility that the combination of ODF and M-CSF was sufficient for OC development in primary murine marrow cell culture. Methods: Bone marrow cells were isolated from 5- to 6- week-old mice and incubated in M-CSF (10 ng/ml). After 24 hours, non-adherent cells were harvested and resuspended in a-MEM /BCS. The suspension was added to the wells of 24-well plates with different concentration of ODF and/or M-CSF. TRAP (tartrate-resistant acid phosphatase) staining was used to identify OC. The bone resorption pits on slices of bovine cortical bone were examined with inverted phase contrast microscope, and the changes of Ca2+ concentration in the medium during whole culture period were measured by atomic absorption spectrophotometer. Results: When bone marrow cells were cultured for up to 11 days either in the presence of M-CSF (10 ng/ml) or ODF (50 ng/ml) , no cells expressing TRAP and bone obvious resorption was found. But in the presence of ODF and M-CSF, many TRAP-positive mono- and multi-nucleated cells were formed after 7 days. The number of TRAP-positive miJti-nucleated cells and the change of Ca2+ in the culture medium increased dose-dependently with ODF concentration. Conclusion: The combination of ODF and M-CSF can induce OC formation and bone resorption in murine marrow cell culture, and it can be employed to investigate the direct effects of factors on OC differentiation and activation.

Key words: Osteoelast differentiation factor, macrophage colony-stimulating factor osteoclast, mice, bone marrow cell