Establishment And Phenotype Analysis Of Placenta Accreta Mice Model

Background Placenta accreta is defined as a serial of diseases that placental villi invade myometrium and even the surrounding organs,often accompanies with severe postpartum hemorrhage,uterine perforation,adjacent organ damage and even death.In recent years,with the increase of cesarean section rate and advanced age pregnancy,the incidence of placenta accreta has increased significantly,which has brought huge challenges to the control of maternal mortality.Clinical studies have found that the occurrence of placenta accreta is mainly related to decidual development defects,abnormal uterine artery remodeling,and excessive invasion of trophoblasts,but the molecular mechanism of its pathogenesis is not yet clear,at the same time,it’s lack of effective early clinical intervention.The treatment of placenta accreta is to terminate the pregnancy by cesarean section at 34 to 36 gestational weeks to reduce the risk of maternal and infant.there is no mature placenta accreta animal model at present and researches on the pathogenesis and intervention of placenta accreta is very limited.Therefore,it’s very urgent to establish a placenta accreta animal model to study its pathogenesis and clinical intervention technology to solve major clinical problems in obstetrics.Purpose We establish placenta accreta mice model by causing trauma on uterus,then compare the differences of mice model with different genetic backgrounds by analyzing the phenotypes of pregnancy outcome and placenta accreta at different period of pregnancy.Methods 1.Female mice were grouped at 10-12 week old.The uterine trauma mice were SU group,and the control mice were CON group.We divided mice into different groups according to the strain,genotype and gestational days,the ICR mice were grouped as E10.5d CON,E10.5d SU,E12.5d CON,E12.5d SU,E14.5d CON,E14.5d SU,E17.5d CON,E17.5d SU,C57 BL / 6J wildtype mice were grouped as E12.5d WT-CON,E12.5d WT-SU,E17.5d WT-CON,E17.5d WT-SU,Nrf2 knockout mice model were grouped into WT-CON♀×KO♂,WT-SU♀×KO♂,KO-CON♀×WT♂,KO-SU♀×WT♂;2.Establishmentof placenta accreta mice model: we created a surgery method by causing an wound on uterus.cut 0.5 cm incision in the right uterus,then continuously sewed with 6-0 absorbable thread,sent it back to mice cage until it woke up on constant temperature workbench,then mated with male mice after postoperative 3 weeks;3.Experimental sample collection: placenta was collected at different gestational age.Intrauterine bleeding,absorption,FGR,litter size,fetal weight and weight gain during pregnancy were recorded when collecting samples;4.Observed the development of the placenta by HE staining;5.Observed the invasion of trophoblast cells by IHC.Results 1.In ICR mice model,we found that the litter size,fetal weight and weight gain during pregnancy of the SU group were lower than that of the CON group(litter size: E14.5d P<0.01,E17.5d P<0.05,fetal weight: E14.5d P<0.01,weight gain: E14.5d P<0.01,E17.5d P<0.01).There was also a downward trend in SU group of C57 BL / 6J mice(little size: E14.5d P<0.01),but not as significant as ICR mice.There were strain differences in the litter size and fetal weight between ICR mice and C57 BL / 6J mice;2.The incidence of intrauterine bleeding,absorption,and FGR in the SU group of ICR mice was higher than that of the CON group(intrauterine bleeding: E12.5d P<0.01,absorption: E12.5d P<0.01,FGR: E12.5d P<0.05),but the difference was most obvious at E12.5d.The adverse pregnancy outcomes also increased significantly in SU group of C57 BL / 6J mice(intrauterine bleeding: E12.5d P<0.01,absorption: E12.5d P<0.05),but fetuses of ICR mice in the surgical side of uterus in the SU group were more prone to lethality(E10.5d P<0.01,E12.5d P<0.01,E14.5d P<0.05,E17.5d P<0.05);3.The incidence of placental abnormality in ICR mice and C57 BL / 6J mice was almost higher in SU group than in CON group,but increased more significantly in SU group of C57 BL / 6J mice(P<0.05).The incidence of placenta accreta in SU group of ICR mice and C57 BL / 6J mice was higher in SU group than in CON group,the phenotype was the most obvious at E17.5d,and the proportion of trophoblast cells in the accreted placenta decidua of the SU group was significantly higher than that of the CON group(P<0.01),and the functional area of accreted placenta was not affected by surgery;4.The fetal weight in WT-SU♀×KO♂ group was significantly lower than that of WT-CON♀×KO♂ group(P<0.01),but litter size was not affected by surgery and genotype.the incidence of FGR in WT-SU♀×KO♂ group increased significantly compared to WT-CON♀×KO♂(P<0.05),and.In the WT-SU♀×KO♂ group,the incidence of placenta accreta was significantly higher in surgical side of uterus than in the control side(P<0.05),The proportion of trophoblast cells in accreted placenta of WT-SU♀×KO♂and KO-SU♀×WT♂group was significantly higher than that of the WT-CON♀×KO♂ and KO-CON♀×WT♂ groups(P<0.05),and the functional area of accreted placenta was not affected by genotype and surgery.Conclusions It is feasible to operate surgery on ICR mice,C57 BL / 6J mice and Nrf2 KO mice to establish placenta accreta animal model.Surgery will increase the invasiveness of trophoblast cells,Nrf2 knockout increases the incidence of placenta accrete,but not make trophoblast invasion in uterus deeper.The mice with different genetic background certainly exist some different phenotype.surgery will decrese the litter size,fetal weight,and weight gain during pregnancy in ICR mice and C57 BL / 6J mice,meanwhile,the incidence of adverse pregnancy outcomes and placental abnormality will increase.The impact of surgery on ICR mice is more significant in litter size and fetal weight compared to C57 BL / 6J mice,and the embryos at the surgical side of uterus are more likely to die.In C57 BL / 6J mice,surgery is more likely to cause placental abnormality,and Nrf2 may affect fetal development.