Study On The Mechanism Of Maternal Cadmium Exposure During Pregnancy Impairs Placental Angiogenesis And Fetal Growth In Mice

Objective:The purpose of this study was to investigate the effect of maternal cadmium（Cd）exposure during different pregnancy on fetal growth,and to explore the role and mechanism of progesterone/progesterone receptor signaling inhibition in Cd-induced placental vascular injury and fetal growth restriction.Methods:In this study,the key period of Cd-induced fetal growth restriction and the mechanism of Cd-impaired placental angiogenesis were investigated by whole animal experiment and in vitro cell experiment.The whole animal experiment consists of two experiments.Experiment 1,CD-1 pregnant mice were exposed to Cd Cl₂（150 mg/L）through drinking water at early（GD0-GD6）,middle（GD7-GD12）and late gestation（GD13-GD17）.Maternal blood,placenta and fetal mice were collected at GD18.The effects of Cd exposure at different gestational stages on the fetal growth were observed.The concentration of Cd in maternal serum and placenta were detected after maternal Cd exposure at different gestational stages.Experiment 2,CD-1 pregnant mice were treated with Cd Cl₂（5 mg/kg,i.p.）at GD8.The maternal blood and placenta were collected at 8 and 24 h after Cd exposure.The progesterone level and vascular endothelial growth factor A（VEGF-A）expression in mouse placenta were detected.In vitro cell research consists of three experiments.Experiment 1,HTR8/SVneo cells were treated with Cd Cl₂（40μM）for 0,6,12 and 24 h,progesterone synthesis and the expression of VEGF-A were detected.Experiment 2,HTR8/SVneo cells were pretreated with progesterone for 1 h,then treatment with Cd Cl₂（40μM）for 12 h,and the expression of progesterone receptor（PR）and VEGF-A were detected.Experiment3,HTR8/SVneo cells were pretreated with overexpression of progesterone receptor（PR）for 48 h,then treatment with Cd Cl₂（40μM）for 12 h,and the expression of progesterone receptor（PR）and VEGF-A were detected.Results:Maternal exposure to Cd at late gestation reduced fetal weight and length,and increased the incidence of fetal growth restriction.Correspondingly,Cd concentration in placenta from late gestational exposure was the highest among three different gestational stages.Placental labyrinth layer blood sinuses and placental angiogenesis,as determined by HE staining and immunostaining,was impaired in mice exposed to Cd during late pregnancy.Western blot results showed that Cd down-regulated the expression of VEGF-A,progesterone receptor（PR）and progesterone synthetases（St AR and CYP11A1）in mouse placenta and human placental trophoblasts.Cd significantly reduced the concentration of progesterone（P4）in maternal serum and cell culture medium,as determined by ELISA.Further studies showed that P4 pretreatment obviously antagonized the inhibitory effect of Cd on the expression of PR and the synthesis of VEGF-A in human placental trophoblast cells,and PR overexpression also significantly reversed the inhibitory effect of Cd on the synthesis of VEGF-A in human placental trophoblast cells.Conclusion:Late gestation is the key period of Cd-induced fetal growth restriction.Cd impaired placental angiogenesis and induced fetal growth restriction by down-regulating P4/PR signaling.