Prediction of severe preeclampsia and intrauterine growth restriction based on serum placental exosome miR-520a-5p levels during the first-trimester

Background: To assess the predictive capabilities of serum exosomal levels of micro-RNA-520a-5p (miR-520a-5p) concerning the occurrence of severe preeclampsia (sPE) and fetal growth restriction (FGR) during the first trimester of pregnancy. Methods: During the period spanning from October 2020 to October 2021, serum samples were procured from the first trimester and subsequently preserved by freezing at -80 degree celsius. These samples were obtained from 105 pregnant women in a nested case-control study. This cohort consisted of individuals who later developed sPE (sPE group, n = 35) and FGR (FGR group, n = 35) during the third trimester. Additionally, 35 women with normal blood pressure were denoted as normal pregnancy group. Serum samples from the first trimester were retrieved from all groups for further analysis after thawing. Exosomes were extracted from the serum samples collected during the first trimester and examined using transmission electron microscopy, western blot, and nanoparticle tracking analysis. Additionally, the determination of their placental origin was also established during the course of the study. Exosome miR-520a-5p levels were measured using real-time quantitative polymerase chain reaction assays, primarily involving quantitative reverse transcription polymerase chain reactions. Fetal placental tissues from the 3 groups were collected shortly after birth, and miR-520a-5p expression was measured using real-time quantitative polymerase chain reaction. Serum placental exosomes and fetal placental tissues were compared for miR-520a-5p levels. Placental trophoblasts were identified as the source of serum exosomes in all 3 groups. Results: It was found that serum placental exosomes exhibited lower levels of miR-520a-5p in both the sPE and FGR groups when compared to the normal pregnancy group. This finding was consistent with observations made in postpartum placental tissues. The predictive accuracy for sPE using miR-520a-5p levels in serum placental exosomes during the first trimester was notably higher (area under the receiver operating characteristic curve = 0.806, P <.05) compared to the prediction of FGR (area under the receiver operating characteristic curve = 0.628, P <.05). Conclusion: Placenta-derived exosomes can be extracted from maternal serum during the first trimester of pregnancy and miR-520a-5p detected from the exosomes. The downregulation of miR-520a-5p serves as a more predictive indicator for the subsequent development of sPE compared to predicting FGR.