Osteoclast formation and function.

(A) Effect of MM cells on osteoclast formation and function in vitro. MM cell lines as well as patients' MM cells were cocultured with rabbit bone cells on dentine slices as described in “Materials and methods.” The data represent the number of TRAP⁺ MNCs (open bars) and pits on dentine slices (hatched bars). Results were expressed as a mean of 5 samples with an error bar of SD. * and ** indicate significantly different from the control culture in the number of TRAP⁺ MNCs and pits, respectively (P < .05, ANOVA with Scheffe post hoc tests). (B) Contact- and soluble factor–dependent stimulation of osteoclast formation and function by MM cells. ARH77 cells were cocultured with rabbit bone cells on dentine slices. Membrane filters were used to prevent cell-cell contact between MM cells and rabbit bone cells. Conditioned media (CM) from ARH77 cells were added at a dilution of 1:2 into rabbit bone cell cultures. Results were shown as a mean of 5 samples with an error bar of SD. * and ** indicate significantly different from cocultures in the number of TRAP⁺ MNCs and pits, respectively (P < .05, ANOVA with Scheffe post hoc tests).