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

AIM: To investigate the possible mechanisms of ginsenoside Rg1 promoting bone marrow stromal cell (BMSC) proliferation.

METHODS: BMSC were isolated from bone marrow of Sprague-Dawley rats and maintained in vitro. After stimulation with 1 micromol/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 [3H]-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 ERalpha was investigated by RT-PCR and Western blotting assays.

RESULTS: BMSC proliferation stimulated by 1 micromol/L ginsenoside Rg1 can be completely blocked by 1 micromol/L ER antagonist ICI 182, 780, or ERalpha- specific antagonist methylpiperidinopyrazole. Moreover, Rg1 failed to displace the specific binding of [3H]17beta-estradiol to BMSC cell lysates, suggesting that no direct interaction of Rg1 with the ER is needed for its estrogenic effects. In addition, 1 micromol/L Rg1 had no effects on the expression of ERalpha in either the mRNA or protein levels.

CONCLUSION: Our results indicate that ERalpha is essential for mediating the effects of Rg1 on stimulating BMSC proliferation, which might involve the ligand/receptor-independent activation of ERalpha.