Downregulations of circulating miR-31 and miR-21 are associated with preeclampsia

MicroRNAs (miRNAs/miRs) are highly stable in circulating, which suppress target gene expression by base-pairing to the 3'-untranslated region. We compared the expressions of 3 circulating miRs (miR-31, miR-21, and miR-16), which are related to the control of cell apoptosis, invasion, angiogenesis and immune tolerance in non-pregnancy (n = 10), 20-34 gestational weeks normal pregnancy (20-34 GW NP, n = 20), early onset preeclampsia (EOPE, n = 20), 34-41 gestational weeks normal pregnancy (34-41 GW NP, n = 20) and late onset preeclampsia (LOPE, n = 20). Using quantitative RT-PCR, we found the levels of miR-31, miR-21 and miR-16 changed throughout different stages of pregnancy with the non-pregnancy as the calibrator. The plasma miR-31 levels were significantly down-regulated in EOPE rather than in LOPE when compared to gestational age matched normal pregnancy (P < 0.001). MiR-21 levels were significantly lower in LOPE compared to healthy controls (P < 0.001), while no significant difference was found between EOPE and 20-34 gestational weeks normal pregnancy (P = 0.376). The miR-16 expressions were at similar levels between preeclampsia (PE) and normal pregnancy. Receiver operating characteristic (ROC) curve analyses indicated the miR-31 differentiated EOPE patients from healthy controls with an area under the curve (AUC) of 0.875 with 95.0% sensitivity and 70.0% specificity. ROC curves also discriminated the LOPE patients from healthy pregnancy with an AUC of 0.793, 65.1% sensitivity and 90.3% specificity for plasma miR-21 levels. This study is the first to demonstrate the difference, and circulating miR-31 may serve as a diagnostic biomarker for early onset preeclampsia meanwhile miR-21 might be a diagnostic biomarker for late onset preeclampsia.