Effects of lanthanum on formation and bone-resorbing activity of osteoclast-like cells

The effect of La³⁺ on formation of osteoclast-like cells in rabbit bone marrow cells induced by 1,25-di-hydroxyvitamin D₃ and their bone-resorbing activity was evaluated by counting the number of tartrate resistant-acid phosphatase-positive [TRAP(+)] multi-nucleated cells and measuring the number and surface area of bone re-sorption pits with photomicrography and image analysis. The formation and morphological characteristics of osteoclast-like cells and bone resorption pits were observed under a phase contrast inverted microscope. La³⁺ promotes the formation of osteoclast-like cells at the concentration of 1.00 × 10 mol·L compared with the control group (P <0.01), whereas no significant change in cell number is observed at higher concentrations (1.00 × 10^-5, 1.00 × 10^-6 and 1.00 × 10^-7 mol·L^-1) (P > 0.05). La³⁺ at the concentration of 1.00 × 10^-8 mol·L^-1 also increases the number and surface area of the resorption pits (P <0.01), but inhibits the bone-resorbing activity dose-dependently (P <0.01) at higher concentrations (1.00 × 10^-5, 1.00 × 10^-6 and 1.00 × 10^-7 mol·L^-1). These findings suggest that La³⁺ may promote or inhibit the formation and bone-resorbing activity of osteoclast-like cells depending on its concentration.