Benzo (a) Pyrene Exposure Promotes Proliferation Of Spongytrophoblast Cells In The Placenta Leading To Placental Dysfunction

Objective:Benzo[a]pyrene(BaP)is an environmental estrogen endocrine disruptor.Previous studies have found that exposure to BaP during pregnancy leads to decreased number of embryo implantation,embryo loss and interference with the proliferation and differentiation of placental trophoblast cells.Placenta plays essential roles during gestation.Fetal nutrition,support and protection,gas exchange are dependent on this organ.Embryo development is inseparable from the structure and function of the normal placenta.Existing studies on the effects of BaP on the placenta are mostly based on the observation of single trophoblasts in vitro,ignoring the mutual regulation of trophoblasts in the placenta.Therefore,this study aims to explore the effect of BaP on trophoblasts during the placental development in vivo.Methods:(1)Animals and treatment:The pregnant mice were divided into BaP treatment group and control group randomly.From the first day of pregnancy,the mice in the treatment group was given 0.2 and 2 mg/kg body weight BaP by gastric administration respectively,and the mice in the control group was administered corn oil.The mice were killed on E9,E12,E14 and E18.The uterus and placenta were collected.(2)HE staining was used to observe the morphology of placenta at various developmental stages,and the secretion function of placenta was detected by ELISA(3)IHC,IF and real-time PCR were used to detect the key factors related to proliferation and differentiation in placenta formation.(4)Real-time PCR,PAS and HE were used to detect the functions of trophoblast cell subtypes.(5)The expression of Notch and PI3K-AKT signaling pathway related factors in the placenta was detected by IHC and western blot.Results:(1)BaP exposure affects the structure of placenta and impaired the development of embryo.(2)BaP disturbs the formation process of functional placenta.The structure of Ectoplacental cone of the placenta was changed on E9,the proportion of each trophoblast area of the placenta was changed on E12,and the secretion of placental hormone is disordered.(3)BaP affects the proliferation and differentiation of Ectoplacental cone of by increasing the expression of transcription factor Mash2,cha nging the morphology of trophoblast giant cells.(4)BaP led to an imbalance in the differentiation of TPBPA~+subtypes of trophoblast cells,resulting in excessive proliferation of spongetrophoblast cells,and altered distribution of glycogen trophoblast cells.(5)BaP increased the expression of RBPJ and P110 in the placenta and promoted the differentiation of TPBPA~+trophoblast cells into sponge trophoblast cells.Conclusion:Exposure to BaP during pregnancy leads to an increase in the area of the placenta junction area,a decrease in the area of the decidual layer and labyrinth layer,disturbance of the placental secretory function.These changes caused adverse pregnancy outcomes in fetal growth restriction and abortion.By observing the formation process of the placenta,it was found that the intervention of BaP disrupted the balance of proliferation and differentiation of placental trophoblast cells in EPC.After BaP intervention,the expression of transcription factor Mash2 in the placenta is enhanced,which promotes the differentiation of TPBPA~+trophoblast cells into sponge trophoblast cells.Notch and PI3K-AKT signaling pathway may be involved in BaP-induced abnormal differentiation of EPC.