Characterization of placenta-specific microRNAs in fetal growth restriction pregnancy.

Objective: The aim of this study was to characterize placenta-specific microRNAs in fetal growth restriction (FGR) pregnancy.

Method: Placenta-specific miRNAs were identified by next-generation sequencing analysis. Subsequently, quantitative real-time reverse-transcription polymerase chain reaction was used to identify FGR placenta-specific miRNAs whose level of expression was significantly decreased in FGR placenta (n = 45) compared with uncomplicated placenta (n = 50). FGR pregnancy-associated, placenta-specific microRNAs were identified in maternal plasma after delivery at significantly decreased concentrations, and their circulating levels in maternal plasma was compared between FGR pregnancies (n = 10) and uncomplicated pregnancies (n = 10).

Results: Out of the ten placenta-specific microRNAs that we identified, seven placenta-specific microRNAs (hsa-miR-518b, hsa-miR-1323, hsa-miR-516b, hsa-miR-515-5p, hsa-miR-520h, hsa-miR-519d, and hsa-miR-526b) from the chromosome 19 microRNA cluster were identified as FGR placenta-specific microRNAs. Four FGR placenta-specific microRNAs (hsa-miR-518b, hsa-miR-1323, hsa-miR-520h, and hsa-miR-519d) were confirmed as FGR pregnancy-associated, placenta-specific miRNAs, but their circulating levels in maternal plasma showed no significant differences between FGR pregnancy and uncomplicated pregnancy.

Conclusion: Our data suggest that reduced expression in placenta of certain FGR placenta-specific miRNAs is associated with FGR and that the discrepancy between expression in FGR placenta and their circulating levels in maternal plasma will be crucial to understanding how placenta-specific microRNAs are released into the maternal circulation.