Urinary microRNA profiling in pregnant women identifies placental microRNAs that are candidate biomarkers for monitoring placental health

MicroRNAs are among the key modulators of placental transcriptome dynamics. This study aimed at comparative profiling of urinary (sampling at 228-230 gestational days, g.days), serum (217-230 g.days), and placental (279-286 g.days) microRNAs in three healthy pregnant women using miRNome sequencing. Placenta showed significant enrichment of microRNAs compared with serum and urine (1174, 341, and 193, respectively; P < 10(-5)). All sample types shared 153 microRNAs, representing candidate biomarkers for placental health. Urine samples contained eight of 56 transcripts from the placenta-specific chromosome 19 microRNA cluster C19MC and one of 91 transcripts (miR-432-5p) from the chromosome 14 cluster C14MC. These data suggest an active filtering at the maternal-fetal interface in passing through only selected microRNAs. Urine represents a valid source to monitor the signature of placenta-expressed microRNAs that are differentially expressed in pregnancy complications.