ERαLysM−/− mice exhibit increased number of osteoclast progenitors and osteoclasts. A, Number of TRAP-positive cells developed from bone marrow cells, extracted from femurs of 12-wk-old mice, and cultured in the presence of M-CSF and RANKL for 5 d. Triplicate cultures were performed from each of seven individual animals. B and C, Histomorphometric analysis of longitudinal undecalcified sections of L1–L3 vertebrae from 12-wk-old female mice (n = 8 mice per group). D, BMDs determined by DEXA in two cohorts (4–12 and 18–28 wk of age) of female ERαLysM−/− and ERαf/f littermate mice (n = 7–23 mice per group). Oc, Osteoclasts; Ob, osteoblasts; BFR, bone formation rate; BA/TA, bone area per tissue area. *, P < 0.05 vs. ERαf/f mice.