Effect of GCT-CM on the chemotaxis and proliferation of rat osteoclast precursor cells (rOPCs). (a) rOPCs were cultured in serum-free medium overnight and washed twice with PBS. The cells were added to the upper compartment of a modified Boyden chamber. GCT-CM and VEGF (10 ng/mL) with or without ZD4190 were added to the lower compartments, and the chambers were incubated for 6 h at 37°C. The migrated cells were stained and counted as described in the Materials and Methods. The results are shown as the means ± SD of two independent experiments that were performed triplicate (* p < 0.01). (b) rOPCs in a 96-well plate were cultured in a serum-free medium for 24 h and washed with PBS. Then, the cells were stimulated with VEGF and GCT-CM with or without ZD4190 for 24 h. Cellular proliferation was assessed by the Celltiter-Glo Luminescent Cell Viability Assay. Results show the means ± SD of two independent experiments that were performed in triplicate. (* p < 0.01).