Aim: 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. Materials & methods: Using next-generation sequencing, we characterize the normative human placenta miRNome in first (n = 113) and third trimester (n = 47). Results & conclusion: 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 <0.05, fold change >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.
Keywords: chorionic villi; gestational differences; human transcriptome; miRNA; miRNA atlas; miRNome; placenta; pregnancy; stable miRNAs; uncomplicated pregnancies.
Lay abstract 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.