Objective    To study the effect of rhein-estrone

a hybrid compound of estrone and rehein

on expressions of TGF-β1 and its receptorⅡ (TβRⅡ) in the long bones of fetal mice in vitro for postulating the mechanism by which rhein-estrone exerts its effect on bone.     Methods    The fetuses of pregnant mice were removed on day 16 of gestation

then the long bones of the forelimbs of female fetal mice were freed of muscle and soft tissues and cultured in a specifically manufactured device for 48 h in BGJb medium treated

respectively with 1×10

-6

mol/L rhein-estrone

estrone

rhein and the mixture of estrone and rhein in the final medium. Aft

er cultured for 48 h

the long bones were harvested and immunohistochemical analysis was performed for determination of TGF-β1 and TβRⅡ proteins expression in epiphyseal plates. The number and their area of positive cells in the resting zone

the proliferative zone and the hypertrophic zone in epiphyseal plate were determined under image analytic system.     Results    When compared with the control group

the levels of TGF-β1 and TβRⅡ proteins were significantly up-regulated after treated respectively with 1×10

-6

mol/L rhein-estrone

estrone or the complex of estrone and rhein

but no obvious up-regulation in both proteins were observed in each zone except TβRⅡ protein in the hypertrophic zone after treated with 1×10

-6

mol/L rhein. When compared with the estrone group

the expression of TGF-β1 and TβRⅡ proteins in rhein-estrone group were enhanced in the resting zone and the proliferation zone.     Conclusion    The expressions of TGF-β1 and its receptor can be up-regulated by rhein-estrone and the up-regulated expressions may be related to promoting fetal mouse long bone growth in vitro.