Cadmium induces the differentiation of duck embryonic bone marrow cells into osteoclasts in vitro

This study aimed to determine the in vitro effect of cadmium on the differentiation of duck embryonic bone marrow cells into osteoclasts. Bone marrow cells were harvested from 23-day old Gaoyou duck embryos and were cultured with either 50 nmol/L cadmium alone or different cadmium concentrations (0, 5, 10, 20 and 50 nmol/L) in combination with macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL). Tartrate-resistant acid phosphatase (TRAP) staining, pit formation assay with bovine cortical bone slices, and co-staining with tetramethyl rhodamine isothiocyanate (TRITC)-conjugated phalloidin and Hoechst 33258 were performed to determine the number of TRAP-positive cells and bone resorption activity. Cadmium at a concentration ⩾ 10 nmol/L in the presence of M-CSF and RANKL significantly increased in a concentration-dependent manner both the number of TRAP-positive cells (35-160%) and bone resorption activity (36-261%) (P<0.05). High cadmium concentrations in the presence of M-CSF and RANKL markedly promoted the formation of filamentous (F)-actin rings in differentiated osteoclasts. In conclusion, cadmium promotes in vitro the differentiation of duck embryonic osteoclasts in the presence of M-CSF and RANKL.