RESUMO
OBJECTIVE To study the protective effect and possible mechanism of soybean isoflavones against threatened miscarriage rats. METHODS Female mice were selected to promote estrus and mate with male mice. After pregnancy， they were randomly divided into normal group （purified water， i.g.， n＝10）， model group （purified water， i.g.， n＝9）， positive control drug group （progesterone 4 mg/kg， i.m.， n＝9）， low-， medium- and high-dose soybean isoflavone groups （25， 50 and 100 mg/kg， i.g.， n＝10）. Except for the normal group， the rest were given mifepristone+misoprostol on the 8th day of pregnancy to establish threatened miscarriage model， and then given purified water or drugs， once a day， on days 1-7 and 9-12 of pregnancy， respectively. At 14 days of pregnancy， the rates of fetal protection were counted. Serum levels of β-human chorionic gonadotrophin （β-HCG） and progesterone （P） in rats were detected. Pathological and morphological changes in rat placenta and decidua tissues were observed， and the apoptosis indexes of cells were detected； mRNA and protein expressions of factor of apoptosis related （Fas）， factor of apoptosis related ligand （FasL）， proliferating cell nuclear antigen （PCNA） and heparin binding epidermal growth factor （HB-EGF） were determined in placenta tissues， and mRNA and protein expressions of Fas， PCNA and HB-EGF in decidua tissues were detected. RESULTS In the model group， the placental tissues of rats were hyperemia and dilatation， with fewer and irregular blood vessels； severe stromal edema，inflammatory cell infiltration and iron-choledrin depositionwere observed. Compared with model group， the fetal survival rates， serum levels of β-HCG and P， the expressions of PCNA and HB-EGF mRNA and proteins in the placenta and decidua tissue of soybean isoflavone groups increased significantly （P＜ 0.05）， while pathological changes were improved significantly； cell apoptosis index in the placenta and decidua tissue， the expressions of Fas， FasL mRNA and proteins in the placenta and Fas mRNA and protein in the decidua tissue decreased significantly （P＜0.05）. The effect of soybean isoflavones was dose-dependent （P＜0.05）. CONCLUSIONS Soybean isoflavone has protective effect on threatened miscarriage， the mechanism of which is related to down-regulating the expressions of Fas and FasL mRNA and protein at the maternal-fetal interface， and up-regulating the expressions of mRNA and protein of PCNA and HB- EGF.
