Abstract: Objective · To investigate the effects of estrogen on proliferation, apoptosis and differentiation of bone marrow macrophage (BMM) and the mechanism. Methods · BMMs were isolated normal C57BL/6J mice and induced to differentiate to osteoclasts in vitro. BMMs in experimental group were administered with 10-8 mol/L exogenous estrogen and antagonist group with both estrogen and 1 μmol/L ICI-182780, an antagonist of estrogen receptor, and control group was designed as well. Five 12-week-old C57BL/6J mice underwent ovariectomy (OVX group) and sham group (n5) underwent sham surgery. All mice were sacrificed after 3 months to isolate BMM. Proliferation ability of BMM was assessed using Prestoblue, TUNEL assay was performed to detect apoptosis in each group. Caspase 3 and caspase 8 were detectedWestern blotting. Quantitative real time PCR was used to detect tartrate-resistant acid phosphatase (Trap) and cathepsin K (Ctsk) mRNA levels during osteoclastogenesis. TRAP staining of osteoclasts showed osteoclastogenesis ability. In addition, the downstream moleculars activatedreceptor activator for nuclear factor-κB ligand (RANKL) in BMM were detectedWestern blotting. Results · BMM multiplication ability was attenuated in experiment group compared with control group and it was stronger in OVX group than that in sham group. TUNEL assay showed that the apoptotic BMM in experimental group were more than those in control group and caspase 3 and caspase 8 were consisted with the results of TUNEL assay. PCR analysis showed that Trap and Ctsk mRNA levels significantly decreased in experiment group compared with control group. The mRNAs increased in OVX group in contrast to sham group. TRAP staining of osteoclasts and quantitative analysis showed that osteoclasts in experiment group were less than those in control group and osteoclasts in OVX group were more than those in sham group. The effects of estrogen on proliferation, apoptosis and differentiation of BMM were blockedantagonist of estrogen receptor. Western blotting showed that the phosphorylation of IκKα/β, p65and JNK activatedRANKL were attenuated in experimental group compared with that in control group. Conclusion · Estrogen inhibits proliferation and osteoclastogenesis of BMM, and aggravates their apoptosis through estrogen receptor.

Key words: bone marrow macrophage, osteoclast, estrogen, estrogen receptor