Figure 7.

Osteoblasts are required for estrogen-mediated apoptosis. (A) Human monocytes were differentiated with M-CSF and RANKL to osteoclasts, without or (B) with osteoblasts (MC3T3 cells), and (left) without or (right) with 10 nM E2 for 8 days. The cells were then fixed and stained for TRAP. (C) The number of multinucleated cells per field from (A) and (B) was counted and expressed as a percentage of the vehicle control-treated cells. Each treatment was counted in triplicate and error bars represent ±1 s.d. (D) Bone marrow cells from wild-type or ERαKO mice were co-cultured with or without MC3T3 cells and without or with 10 nM E2 under osteoclastic conditions for 8 days. The cells were then fixed and stained for TRAP. The number of multinucleated cells per field was counted and expressed as a percentage of the vehicle control-treated cells. (E) Cells were cultured as in part D, except that 10 nM E2 was added at day 6 for 16 h. The cells were then fixed and apoptosis was detected by TUNEL. Quantification was performed with a laser scanning cytometer.