Figure 1.

Estrogen receptor α (ERα) expression increases bone mass in different bone compartments through its action in different cell types. ERα deletion in osteoclasts (Cathepsin K-cre and LysM-cre) reduced trabecular bone mass in female, but not in male, mice, whereas its deletion in osteocytes (DMP1-cre) reduced trabecular bone mass in male but not in female mice. Cortical bone in female mice was reduced by deletion of ERα in osteoblasts (Osteoclacin-cre, osterix-cre) and pre-osteoblasts (Prx-cre). In male mice, deletion of ERα in osteoblasts (osteoclacin-cre, Col1A1-cre) had no effect on male cortical bone, whereas its deletion in pre-osteoblasts (Prx-cre) reduced cortical thickness.