MiRNA-101 Participates In The Pathogenesis Of Gestational Diabetes Mellitus By Regulating Trophoblast Cellfunction

【Background】 Gestational diabetes mellitus(GDM)is one of the most common medical conditions women encounter during pregnancy.Contrary to other obstetric complications,its prevalence has increased over the past decades.GDM prevalence in China has been reported to be as high as 17.5%.Despite plenty of researches explaining the mechanisms of GDM,the underlying molecular mechanisms are not fully understood.Current research suggests that epigenetic modifications during pregnancy may be an important mediator.Epigenetics refers to coding,excluding that of the DNA sequence,which can influence the transcriptional rate.These variations in the epigenetic programming can be caused by environmental factors and can activate or silence gene expression.The most common types of modification are DNA methylation,modification of histones or regulation of gene expression by microRNA(miRNA,miRs).miRNAs are a class of noncoding RNAs(nc RNA)which regulate gene expression at post-transcriptional level.Recent findings show that the placenta produces numerous miRNAs with some of them being released in the maternal circulation.They were shown to be dysregulated in plasma and placenta from women suffering from GDM and associated with pregnancy and birth-related outcomes.EZH2 is part of the polycomb repressor complex 2,a multisubunit complex,which initiates and maintains the trimethylation of histone H3 on lysine 27(H3K27me3),an epigenetic mark associated with heterochromatin formation and gene silencing.It is well known that placenta is a highly specialized organ in the interface between maternal and fetal circulation with fundamental functions for pregnancy.Therefore,placental dysfunction has deleterious effects on adequate pregnancy support.Among placental cells,trophoblasts permit the embryo implantation and nutrition in the early pregnancy and thereafter they will contribute considerably to thedevelopment and function of the placenta.There has been study showing that GDM impairs HUVEC functions through a mechanism involving miR-101 and EZH2.The regulation of EZH2 by miRNAs in trophoblast cells is still unexplored.In this study,we focused on miR-101 targeting EZH2 in regulating trophoblast cell’s function and its potential mechanism in GDM.【Objective】 To study the difference of expression of miRNA-101(microRNA-101-3p)and EZH2 in placentas between patients with gestational diabetes mellitus(GDM)and normal pregnant women,and to study the effect of miRNA-101 on the proliferation and migration of placental trophoblast cells and its possible mechanism in GDM by overexpression or knockdown of microRNA-101 in human placental trophoblast cell(HTR-8/SVneo).【Methods】 The expression of EZH2 and H3K27me3 in placenta of GDM patients and normal pregnant women was detected by immunohistochemistry;the expression of miRNA-101 and EZH2 in placenta of GDM patients and normal pregnant women was detected by PCR and Western blot;after over-expression or knockdown of mi RNA-101 in HTR-8/SVneo cells,the expression of EZH2 mRNA was detected by PCR,the expression of EZH2 and H3K27me3 was detected by Western blot,and then CCK-8 and Transwell experiments were conducted.【Results】 EZH2 and H3K27me3 were expressed in placentas of both GDM patients and normal pregnant women,and localized in placental trophoblast cells;the expression of miRNA-101 mRNA in placentas of GDM patients was significantly higher than that of normal pregnant women,the expression of EZH2 mRNA was lower than that of control group,the expression of EZH2 and H3K27me3 was lower than that of control group;after over-expression of microRNA-101,the expression of EZH2 andH3K27me3 decreased,and the proliferation ability and migration ability of placental trophoblasts decreased;while the expression of EZH2 and H3K27me3 increased after knocking down the microRNA-101.The proliferation ability of placental trophoblasts did not change significantly,and the migration ability increased.【Conclusions】 miRNA-101 negatively targeting EZH2 decreases the proliferation and migration ability of placental trophoblasts,which leads to abnormal placental structure and function during embryonic development and participates in the pathogenesis of GDM.