[Detection of placenta-specific microRNAs in maternal circulation]

We focused on the detection of microRNAs in maternal circulation during the course of physiological pregnancy. We tested initially microRNAs (mir-135b and miR-517a) which presence in maternal circulation had been previously demonstrated and those microRNAs (miR-518b and miR-517a) with up-regulated expression profile in placentas derived from pregnancies during the onset of preeclampsia. Further we selected those microRNAs, which were reported to be placenta specific according to the miRNAMap database (these microRNAs were significantly expressed in the placenta and simultaneously showed no or minimal expression in other tissues).

Division of Molecular Biology and Cell Pathology, Department of Gynaecology and Obstetrics, Third Faculty of Medicine, Charles University, Prague.

RNA enriched for small RNAs (including microRNAs) was isolated from 1 ml of maternal plasma during the 12th, 16th and 36th week of gestation and 200 microl of peripheral blood derived from healthy non-pregnant women. Consequently relevant microRNA was transcribed into cDNA using specific stem-loop primer and detected by specific real-time PCR assay.

From the cohort of tested microRNAs we excluded those ones, which were not detectable in maternal circulation during pregnancy (miR-136 and miR-519a) and/or were demonstrated in peripheral blood of healthy non-pregnant women (miR-34c, miR-224, miR-512-5p, miR-515-5p, miR-516-5p, miR-518f*, miR-519d, miR-519e).

On the base of the current study results we finally selected 6 most suitable microRNAs (miR-517*, miR-518b, miR-520a*, miR-520h, miR-525 and miR-526a) for subsequent studies concerning the follow-up of placenta specific microRNAs in maternal circulation during pregnancy and the differentiation between normal and pathologic pregnancies (preeclampsia, IUGR) within the same gestational age.