Effect of 17#beta#-estradiol (E_(2)) on the gene expression of osteoprotegerin in human osteoblast and MG-63 cells.

Objective To investigate the effects of 17 β estradiol (E 2) on the gene expression of osteoprotegerin (OPG) in human osteoblast (HOB) and MG 63 osteosarcoma cell lines at various maturity stages of cultures, and to make a better understanding of the mechanism of E 2 deficient osteoporosis. Methods The activities of alkaline phosphatase (ALP), osteocalcin (OC) secreted by cultured cells at different stages of cell proliferation, maturity and collagen mineralization, as well as the effect of E 2 on the OPG gene expression were determined. HOB was prepared from ilial bone tissue in adults, OPG gene expression was quantified by RT PCR, and the activity of ALP, OC was corrected with Bradford′s method. Results For both kinds of cells, expression of OPG at the 12th days′ culture reached the highest levels without any treatment, and 10 -8 mol/LofE 2increasedOPGmRNA to a maximum of about 10 times (P0.001) in MG 63 and 7～8 times (P0.01) in HOB. Conclusion OPG can be expressed by HOB and by MG 63 cells, while E 2 shows a positive role to osteoblasts to amplify OPG gene expression in vitro, suggesting that deficiency of E 2 in postmenopausal osteoporosis women may result in a dysfunctional expression of the OPG gene.