Migration Of Gut Fusobacterium Nucleatum To Placenta Induces The Onset Of Pre-eclampsia

Background and objectives:Pre-eclampsia(PE)is a specific pregnancy complication characterized by new-onset hypertension and proteinuria,and it may possibly progress to organs dysfunction after 20 weeks of gestation.It affects an estimated 2%-8%of pregnancies worldwide and it not only affects the health of women,but also affects the long-term prognosis of offspring.Besides,the pathogenic mechanism of PE is not yet clear and there are no effective preventive and therapeutic measures for it so far.In recent years,it has been reported to be associated with gut microbiome.We previously found that gut-derived Fusobacterium plays an important role in the development of PE.However,which bacterial strain of Fusobacterium and by what mechanisms contribute to this is still unknown.The aim of this study is to further explore the role of Fusobacterium nucleatum in pre-eclampsia.Research contents and methods:1.Fusobacterium nucleatum induces the onset of pre-eclampsia through migrating from gut to placenta.(1)Preparation of fluorescent-labeled strains:Fusobacterium nucleatum with a Green fluorescent protein(GFP-Fn)and Escherichia coli with mCherry(mCherry-E.coli)were prepared by introducing fluorescent plasmids into bacteria by electrotransformation.(2)Construction of an animal model for pre-eclampsia:Female C57/BL6 mice treated with antibiotics for 5 days were randomly divided into 3 groups and gavaged with GFP-Fn,mCherry-E.coli and saline,respectively,and after 1 week of continuous gavage,all female mice were housed with male mice overnight and the gestating mice were continued to gavage until 17.5 days of gestation.(3)Confirmation of PE-like phenotype:The changes of blood pressure in mice before and after pregnancy were continuously monitored.The changes of urinary protein levels in mice were detected before and after the intervention.The number and weight of fetal litters and placenta,the pathomorphological changes of mouse kidney,and colonization of placenta by bacteria were observed after pregnancy.2.Fusobacterium nucleatum acts by disrupting the intestinal barrier to migrate the placenta.(1)The colonization of the target bacteria in the intestine was observed by isolated tissue imaging,qPCR,frozen fluorescent sections and HE stainings.(2)The indicators of intestinal barrier function were examined including the relative expression of ZO-1,Claudin4 and Occludin.(3)Histomorphological changes in placenta were observed,and the relative expression of placental inflammatory factors was measured.Results:1.GFP-Fn and mCherry-E.coli,the two fluorescently labeled strains were successfully prepared and identified by the methods of agarose gel electrophoresis and MALDI-TOF,and then they could be cultured in vitro.2.F.nucleatum-intervened mice showed a significant increase in blood pressure at the 9.5 days of gestation,which further elevated until the end of gestation,along with PE-like clinical phenotypes such as higher urinary protein,significant renal lesions,and lower fetal and placental weights.3.F.nucleatum could colonize the intestinal tract,leading to gut dysbiosis and promoting intestinal inflammation,which in turn disrupts intestinal barrier function.4.F.nucleatum intestinal intervention,which could migrate to the placenta and colonize the placenta,led to structural disorders in the vagal zone of placenta and a significant increase in the expression of inflammatory factors in the placenta.Conclusions:These findings collectively suggest that intestinal intervention of Fusobacterium nucleatum can migrate from the intestine to the placenta by disrupting the intestinal barrier and colonize the placenta,causing local inflammation and dysfunction of the placenta,which in turn induces the development of pre-eclampsia.