Maternal peripheral blood natural killer cells incorporate placenta-associated microRNAs during pregnancy

Abstract

Although recent studies have demonstrated that microRNAs (miRNAs or miRs) regulate fundamental natural killer (NK) cellular processes, including cytotoxicity and cytokine production, little is known about the miRNA-gene regulatory relationships in maternal peripheral blood NK (pNK) cells during pregnancy. In the present study, to determine the roles of miRNAs within gene regulatory networks of maternal pNK cells, we performed comprehensive miRNA and gene expression profiling of maternal pNK cells using a combination of reverse transcription quantitative PCR (RT-qPCR)-based miRNA array and DNA microarray analyses and analyzed the differential expression levels between first- and third-trimester pNK cells. Furthermore, we constructed regulatory networks for miRNA-mediated gene expression in pNK cells during pregnancy by Ingenuity Pathway Analysis (IPA). PCR-based array analysis revealed that the placenta-derived miRNAs [chromosome 19 miRNA cluster (C19MC) miRNAs] were detected in pNK cells during pregnancy. Twenty-five miRNAs, including six C19MC miRNAs, were significantly upregulated in the third- compared to first-trimester pNK cells. The rapid clearance of C19MC miRNAs also occurred in the pNK cells following delivery. Nine miRNAs, including eight C19MC miRNAs, were significantly downregulated in the post-delivery pNK cells compared to those of the third-trimester. DNA microarray analysis identified 69 NK cell function-related genes that were differentially expressed between the first- and third-trimester pNK cells. On pathway and network analysis, the observed gene expression changes of pNK cells likely contribute to the increase in the cytotoxicity, as well as the cell cycle progression of third- compared to first-trimester pNK cells. Thirteen of the 69 NK cell function-related genes were significantly down-regulated between the first- and third-trimester pNK cells. Nine of the 13 downregulated NK-function-associated genes were in silico target candidates of 12 upregulated miRNAs, including C19MC miRNA miR-512-3p. The results of this study suggest that the transfer of placental C19MC miRNAs into maternal pNK cells occurs during pregnancy. The present study provides new insight into maternal NK cell functions.

Imprinted MicroRNA Gene Clusters in the Evolution, Development, and Functions of Mammalian Placenta

“…Of note, C19MC-mediated paracrine effects are very likely virus-specific, because they do not protect, and even potentiate, CMV infection (Delorme-Axford et al, 2013). Other studies also demonstrated an involvement of exosomal C19MC miRNAs in cell-to-cell communication, notably between placenta and immune cells (Kambe et al, 2014; Ishida et al, 2015). In vitro , miR-517a-3 secreted from human choriocarcinoma (BeWo) cells can be transferred into the immortalized T lymphocyte (Jurkat) cells, where it downregulates the expression of endogenous PRKG1 mRNA.…”

“…Their levels rapidly decline after delivery, further arguing that exosome-mediated delivery of C19MC in immune cells occurs during pregnancy. Yet, their putative roles in immunity pathways remain to be unveiled (Ishida et al, 2015). Altogether, these data lend experimental support to the concept that C19MC miRNA-containing exosomes mount cellular responses to protect fetus from maternal immune activation and viral infection (Bullerdiek and Flor, 2012; Mouillet et al, 2014; Tong et al, 2018).…”

The expression of miRNA encoded by C19MC and miR-371-3 strongly varies among individual placentas but does not differ between spontaneous and induced abortions

“…C19MC is nearly exclusively expressed in the placenta (Bentwich et al 2005;Luo et al 2009), suggesting an important role in placental development and function. Specific function and regulation of C19MC in the placenta is not completely clear yet (reviewed by (Mouillet et al 2015)), but three functional complexes are likely to be influenced by C19MC: these are viral resistance (Delorme-Axford et al 2013), AR: induced abortion; MSA: spontaneous abortion; TE: delivery at term + − 2 weeks; SD: standard deviation; nfold max/min: ratio of highest expression divided by lowest expression implantation and placenta development (Anton et al 2015;Ding et al 2015;Xie et al 2014), and immunomodulation in terms of fetal-maternal cross talk (Bullerdiek and Flor 2012;Ishida et al 2015;Kambe et al 2014). This is, to our knowledge, the first report investigating the expression of C19MC miRNAs and miR-371-3 cluster in the placental tissue comparing three groups (induced and spontaneous abortions and full-term placentas) in a large cohort.…”

“…The authors found that placental trophoblast cells are highly resistant to several virus infections and additionally confer their resistance to other nonplacental cells via exosomes containing, among others, specific miRNAs of C19MC. Furthermore, immunomodulatory functions related to the establishment and maintenance of embryo-maternal tolerance have also been assumed to be influenced by these miRNAs (Bullerdiek and Flor 2012;Ishida et al 2015;Kambe et al 2014). In addition, there is an increasing evidence that contribution to proper implantation and placenta development is another group of functions addressed by the miRNAs of both clusters (Xie et al 2014).…”

Reference values for circulating pregnancy‐associated microRNAs in maternal plasma and their clinical usefulness in uncomplicated pregnancy and hypertensive disorder of pregnancy

“…In accordance with this and other previous studies, the reference values of pregnancy‐associated placental miRNAs on C19MC (miR515‐3p, miR‐517a, miR‐517c and miR‐518b) increased as pregnancy progressed and rapidly decreased 1 day after delivery. Additionally, one study showed that the expression of C19MC miRNAs in pNK cells were significantly upregulated in the third trimester compared with the first‐trimester, and the rapid clearance of C19MC miRNAs from the pNK cells occurred after delivery . This suggests that C19MC miRNA regulates migratory and invasive behaviors of extravillous trophoblasts and plays a role in the establishment of the maternal–fetal interface .…”