IN-VITRO DIFFERENTIATION OF THE MURINE MACROPHAGE CELL-LINE BDM-1 INTO OSTEOCLAST-LIKE CELLS

Osteoclasts are derived from hematopoietic stem cells, but details abo ut their precursor are still obscure. We present here a mouse macropha ge cell line, BDM-1 cells, that showed a high potential to differentia te into osteoclast-like multinucleate cells (MNCs) when cocultured wit h primary osteoblasts for 14 days in the presence of 10(-8) M 1 alpha, 25-dihydroxyvitamin D-3. These MNCs had tartrate-resistant acid phosph atase (TRAP) activity and strong ability to resorb dentine. In this cu lture system, 10(-10)-10(-8) M 12-O-tetradecanoylphorbol-13-acetate st imulated the formation of TRAP-positive MNCs, whereas salmon calcitoni n inhibited it. Time-course effect studies showed that 12-O-tetradecan oylphorbol-13-acetate had an effect on the late phase of osteoclast di fferentiation but not on precursor proliferation. By immunocytochemica l staining, all BDM-1 cells expressed Mac-1, Mac-2, and MOMA-2 antigen s, and a large number of them expressed F4/80 antigen, but the rest of them were negative for this antigen. To select subclones able to diff erentiate into TRAP-positive MNCs, we sought to isolate several subclo nes from BDM-1 cells by mean of different specificity for F4/80 antige n expression. TRAP-positive MNCs were not generated from F4/80-positiv e subclones, but were obtained from subclones containing F4/80-negativ e cells. These results suggest that an F4/80-negative macrophage subpo pulation is responsible for the differentiation of this cell line into osteoclasts.