26: Severe placental insufficiency, acidemia and imminent stillbirth are associated with changes in circulating levels of mRNA coding NR4A2, RCBTB2 and EMP1

Abstract

To identify mRNA in the maternal circulation associated with severe preterm fetal growth restriction (FGR), fetal acidemia and imminent stillbirth. We performed a prospective study across six referral hospitals. We obtained maternal blood from 128 cases of FGR delivered by cesarean section <34 weeks due to fetal compromise, and 84 healthy gestation matched controls. FGR samples were collected within 2 hours prior to birth and umbilical cord pH was measured to determine fetal acidemia status. We performed RNA-seq on all 212 samples and bioinformatics (linear model, switch box and PLSDA) to identify genes differentially expressed in the FGR group. We used PCR to validate top genes (ie those consistently deranged in cases compared to controls, identified by bioinformatics), and also to examine those genes differentially expressed with fetal acidemia. We then measured the top genes in a separate cohort of six women whose pregnancies were affected by preterm FGR and ended in stillbirth. The baseline clinical characteristics of the FGR and control cohort are shown on the table. There were global changes in mRNA gene expression (11,402 genes differentially expressed with adjusted p<0.05) in the maternal circulation among the FGR cohort (n=128) vs gestationally matched controls (n=84). Using bioinformatics on the RNA-Seq data followed by PCR validation, we identified 8 genes that were differentially expressed with FGR with a very high level of significance. Of those, NR4A2 (Fig. A,B) and RCBTB2 were also differentially expressed when the FGR cohort was split according to whether umbilical cord pH at delivery was ≤7.2 (low pH, acidemic fetus) or >7.2. Notably, of these 8 genes that were differentially expressed with FGR, mRNA coding NR4A2 (Fig. C), RCBTB2 and EMP1 were consistently deranged in the circulation of six women with imminent stillbirth (last blood before demise, gestational age range 19-28 weeks) compared to 24 gestational age-matched controls (ongoing pregnancies). Severe preterm fetal growth restriction, in utero acidemia and imminent stillbirth are associated with differential expression of mRNA coding NR4A2, RCBTB2 and EMP1 in maternal blood. They have potential as markers of severe placental insufficiency and the ‘at risk’ fetus.View Large Image Figure ViewerDownload Hi-res image Download (PPT)