Introduction: microRNAs (miRNAs) play important role in the regulation of placental
development, and abnormal miRNA expression is associated with preeclampsia (PE).
miRNAs are released from trophoblast cells to maternal blood flow, where they are highly
stable, being encapsulated inside extracellular vesicles, like exosomes or bound to Argonaute
proteins. In PE, placental dysfunction leads to aberrant extracellular miRNA secretion. hsamiR-
210 is a hypoxia-sensitive miRNA found to be upregulated in PE, however, it is
unknown whether it is the cause or the consequence of the disease.
Objective: Our aim was to analyze the expression of several miRNAs, including hsa-miR-
210 in placenta, exosome and Ago-bound fractions comparing normal (N) and PE
pregnancies. We performed in vitro analyses of extracellular hsa-miR-210 secretion of
trophoblast cell cultures (of villous and extravillous origin) under hypoxic condition.
Methods: PE and N placenta samples were collected from C-sections, and blood samples
were drawn from each pregnant woman in the third trimester. Htr-8 and Jar cell lines were
cultured in exosome-free media and treated with hypoxia-mimetic agents. Exosome and Agobound
fractions were isolated by membrane affinity spin column method from plasma and cell
media. Short RNAs were extracted from exosomes and vesicle-free fractions, and total-RNA
was isolated from the placenta samples. The RNA purity and concentration were measured by
spectrophotometry. Expression analysis was carried out by qPCR with specific primers to
target and reference miRNAs.
Results: The level of hsa-miR-210 was significantly higher in PE placentas, which could
cause a minor increase of exosomal and a high elevation of Ago-bound miR-210 in
circulation. Hypoxia leads to intracellular hsa-miR-210 upregulation in trophoblast cell lines.
In extravillous cell (HTR8) media, only the level of exosomal hsa-miR-210 was increased but
no change in Ago-bound hsa-miR-210 level was observed. In contrast, in villous cell (JAR)
media, the level of exosomal hsa-miR-210 was increased and enhanced release of Ago-bound
hsa-miR-210 was also observed.
Conclusion: Based on our data, we postulate that in PE, exosomal hsa-miR-210 are secreted
actively from the trophoblast, and by intercellular communication, it may have a role in
disease etiology. In addition, there is a passive release of Ago-bound hsa-miR-210 into the
circulation, which may represent by-products of cell-death and is thereby a possible
consequence of the disease