The Regulatory Network Played by miRNAs During Normal Pregnancy and Preeclampsia: A Comparative Study.

Background: Preeclampsia is a pregnancy-specific syndrome, characterized by hypertension, proteinuria, and edema. Affecting between 2% and 8% of gestations worldwide, it accounts for 10% to 15% of maternal deaths. Although its etiology remains unclear, it includes complex pathological processes involving microRNAs, small non-coding RNA molecules with post-transcriptional repression effects on target mRNAs.

Objective: To assess the expression of miRNAs during normal pregnancies and those complicated by preeclampsia, a sample of Venezuelan women were studied.

Method: Nine placental microRNAs (hsa-miR- 20a-5p, 21-3p, 26a-5p, 181a-5p, 199a-5p, 210-3p, 222-5p, 223-3p, 424-3p) were measured in maternal plasma during the second and third trimesters of normal pregnancies, using a SYBR Green®-based real-time PCR, and compared the results against women affected by preeclampsia.

Results: All assessed miRNAs were detected in maternal plasma in pregnancies with and without preeclampsia. All except miR-222 were over-expressed during disease when compared to the second and to third-trimester controls. miR-20a, miR-21, miR-26a, and miR-223 were down-regulated in the third trimester in comparison to the second trimester in normal pregnancies.

Conclusion: The variation of the miRNAs expression through normal pregnancies suggested their involvement in normal physiological pregnancy processes. In contrast, the significant deregulation of the nine studied miRNAs during preeclampsia indicated the involvement of their target genes in the pathogenesis of the disease. miR-199a and miR-21-3p showed the greatest changes in expression. This study shows for the first time the presence of miR-20a, miR-199, and miR-424 and the variations they undergo in the plasma of pregnant women with preeclampsia.