Ginsenoside Rg1 promotes bone marrow stromal cells proliferation via the activation of the estrogen receptor-mediated signaling pathway1

To investigate the possible mechanisms of ginsenoside Rg1 promoting bone marrow stromal cell (BMSC) proliferation. BMSC were isolated from bone marrow of Sprague-Dawley rats and maintained in vitro. After stimulation with 1 μmol/L ginsenoside Rg1 for the indicated time, the proliferation ability of BMSC were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and [3 H]-thymidine incorporation assays. The estrogen receptor (ER) binding activity of BMSC was determined by a specific ER antagonist and an ER binding assay. Furthermore, the influence of ginsenoside Rg1 on the expression of ERα was investigated by RT-PCR and Western blotting assays. BMSC proliferation stimulated by 1 μmol/L ginsenoside Rg1 can be completely blocked by 1 μmol/L ER antagonist ICI 182, 780, or ERα-specific antagonist methylpiperidinopyrazole. Moreover, Rg1 failed to displace the specific binding of [3 H]17 β-estradiol to BMSC cell lysates, suggesting that no direct interaction of Rg1 with the ER is needed for its estrogenic effects. In addition, 1 μmol/L Rg1 had no effects on the expression of ERα in either the mRNA or protein levels. Our results indicate that ERα is essential for mediating the effects of Rg1 on stimulating BMSC proliferation, which might involve the ligand/receptor-independent activation of ERα.