Bone remodeling is accomplished by bone formation and bone resorption. The major bone resorbing cell is osteoclast. Osteoclasts arise from hematopoietic mononuclear cells in the bone marrow. They are multinucleated cells fused by the precursors. Osteoclasts are very inaccessible cells, and so direct studies on these cells have been difficult to perform. Osteoclast-like cell can be derived from spleen pluripotent stem cell. In this study an enrichment for primitive hematopoietic progenitors can be derived in mice by the treatment with a high dose of 5-fluorouracil. Then small colonies can form in the culture with the recombinant interleukin-3 and 6.These cells differentiated under the presence of recombinant granulocyte-macrophage colony stimulating factor (GM-CSF). In cultured with 1,25(OH)2VitD3, multinucleated cells appeared with some characteristics of osteoclasts such as tartrate-resistant acid phosphatase (TRAP) and forming the excavation. This experimental model has become a useful tool for further study of osteoclast formation in vitro.
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