Variation in expression of fetal nucleic acids in maternal blood in pregnancies affected by congenital anomalies

Abstract

The discovery of cell free fetal DNA has opened a new door for non-invasive prenatal screening and diagnosis. Other cell free nucleic acids, like microRNAs, may also be of value in detecting fetal anomalies. miRNAs control developmental processes and may therefore be useful as biomarkers for fetal abnormalities and placental function. We aimed to develop the laboratory skills for reliable analysis of cell free miRNA and to collect some pilot data looking at variation in cell free fetal miRNA expression with fetal abnormality. Blood was collected into three types of collection tubes (EDTA, STRECK and CITRATE) and kept at 4ºC or room temperature up to 96 hours. Six miRNAs, previously defined as being placental specific, were measured using qRT-PCR. Further comparative studies were made between pregnancies affected by fetal abnormality and controls. Optimisation studies using blood from 14 normal pregnancies suggest that cell free miRNAs are best extracted from either STECK (room temperature) or EDTA (4ºC) tubes and that plasma should be extracted within 72 hours. Three miRNAs (miR-518, miR-520 and miR-525) that were previously described as being placental specific were also detected in plasma of three non-pregnant women; miR-525 appeared to be significantly up-regulated in pregnancy. miRNA expression from 16 normal, 15 chromosomally abnormal, 6 cardiac anomalies and 4 neural tube defects were compared. No significant differences in the relative expression of these six miRNAs were seen between control and anomalous pregnancies with the exception of significant up-regulation of miR-520 in two fetuses with hypoplastic left heart syndrome. The results of this study have established the best tube and conditions of blood collections for future investigations into fetal miRNAs.