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-dihydroxyvitamin 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 resorption 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 1.00×10-8mol·L-1 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 1.00×10-8mol·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.