Effects of sodium fluoride treatment in vitro on cell proliferation, apoptosis and caspase-3 and caspase-9 mRNA expression by neonatal rat osteoblasts

Long-term excessive fluoride intake is linked to skeletal disease. Skeletal health is influenced by the balance between bone formation and resorption of which osteoblast function is critical. The objectives of this study were to determine the effect of fluoride treatment on osteoblast proliferation, apoptosis and caspase-3 and caspase-9 mRNA expression in vitro. Neonatal rat osteoblasts were cultured in the presence of varying concentrations (0.5–30 mg/l) of sodium fluoride and effects of treatments were determined. Treatment with sodium fluoride inhibited osteoblast proliferation in a dose-dependent fashion and effects were maximal after 120 h incubation. A significant increase in osteoblast apoptosis was observed (after 24 and 72-h treatment) in response to the lowest dose of sodium fluoride (0.5 mg/l) and osteoblast apoptosis was further increased in response to higher doses. Increased-osteoblast caspase-3 and caspase-9 mRNA was also observed in response to sodium fluoride treatment (5 mg/l) for 72 h. Results indicate that negative effects of excess fluoride on skeletal health may be mediated in part by inhibition of osteoblast survival.