High-throughput miRNA sequencing of the human placenta: expression throughout gestation

To understand miRNA changes across gestation in healthy human placentae. This is essential before miRNAs can be used as biomarkers or prognostic indicators during pregnancy. Using next-generation sequencing, we characterize the normative human placenta miRNome in first (n = 113) and third trimester (n = 47). There are 801 miRNAs expressed in both first and third trimester, including 182 with similar expression across gestation (p ≥ 0.05, fold change ≤2) and 180 significantly different (false discovery rate 2). Of placenta-specific miRNA clusters, chromosome 14 miRNA cluster decreases across gestation and chromosome 19 miRNA cluster is overall highly expressed. Chromosome 13 clusters are upregulated in first trimester. This work provides a rich atlas of healthy pregnancies to direct functional studies investigating the epigenetic differences in first and third trimester placentae. The human body produces miRNAs which affect the expression of genes and proteins. This study uses next-generation sequencing to identify the miRNA profile of first and third trimester human placentae using a large cohort (n = 113 first trimester; n = 47 third trimester). All pregnancies resulted in healthy babies. We identify miRNAs with significantly different expression between first and third trimester, as well as stably expressed miRNAs. This work provides a baseline for future studies which may use miRNAs to monitor maternal–fetal health throughout pregnancy.