Culture of human osteoclasts

OBJECTIVE: To establish a stable, useful culture system for human osteoclasts and to investigate the effect of osteoblasts on the differentiation, proliferation and activation of osteoclasts so as to provide a base for the studies on prevention and treatment of osteolysis and osteoporosis. METHODS: In the presence of 1,25-(OH)2D3, monocytes abstracted from human bone marrow were cultured in three groups: co-culture of monocytes and osteoblasts, monocytes alone, monocytes with conditional media (CM) of osteoblasts. Differentiation process of the cultured cells was observed under biological microscope. HE staining and tartrate-resistant acid phosphatase (Trap) staining were employed to assay the cultured cells. The resorption pits on bone slices, on which cells were cultured, were observed under scanning electronic microscope (SEM). RESULTS: In the group of co-culture of monocytes and osteoblasts, monocytes gradually fused to form multinucleated cells (MNCs), and the MNCs were also indicated in HE staining and Trap staining. The SEM showed a number of resorption pits on bone slices. In the other two groups, Trap-positive MNCs were not obtained, and resorption pits were not observed on bone slices. CONCLUSION: In this culture, monocytes obtained from human marrow fused to form multinucleated cells (MNCs) that express the main characteristics of the osteoclast phenotype, such as Trap-positive and the ability to form resorption lacunae when cultured on bone slices. Cell-to-cell contact with osteoblasts was necessary for the differentiation, proliferation and activation of osteoclasts.