桑田 知之

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 downregulated 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.

To construct a model to calculating probability of requiring allogeneic blood transfusion on cesarean section (CS) for placenta previa (PP). A retrospective cohort study involving all 205 patients with PP who underwent CS in our institute. We determined the relationship between allogeneic blood transfusion and nine preoperative factors: (1) maternal age, (2) parity, (3) uterine myoma, (4) previous CS, (5) the placenta covering the previous CS scar (referred to as "scar covering"), (6) degree of previa, (7) ultrasound finding of lacunae, (8) preoperative anemia, and (9) preparation of autologous blood. Independent risk factors of allogeneic blood transfusion were identified by multivariate logistic regression analysis. These significant factors were included in the final model, and, the probability of allogeneic blood transfusion was calculated. Independent risk factors of allogeneic blood transfusion were scar covering, previous CS without scar covering, and lacunae. These three factors were used to create a predictive model. The model revealed that patients with scar covering and lacunae had the highest probability (0.73), while those with no risk factors had the lowest probability (0.02). This simple model may be useful to calculate probability of requiring allogeneic blood transfusion on CS for placenta previa.

During pregnancy, human placenta-associated microRNAs (miRNAs) derived from the miRNA cluster in human chromosome 19 are expressed in villous trophoblasts and secreted into maternal circulation via exosomes; however, little is known about whether circulating placenta-associated miRNAs are transferred into maternal immune cells via exosomes, and modulate expression of target genes in the recipient cells. We employed an in vitro model of trophoblast-immune cell communication using BeWo cells (a human trophoblast cell line) and Jurkat cells (a human leukemic T-cell line) and investigated whether BeWo exosomal placenta-associated miRNAs can suppress expression of target genes in the recipient Jurkat cells. Using this system, we identified PRKG1 as a target gene of placenta-associated miRNA miR-517a-3p. Moreover, we demonstrated that BeWo exosomal miR-517a-3p was internalized into Jurkat cells and subsequently suppressed the expression of PRKG1 in recipient Jurkat cells. Furthermore, using peripheral blood natural killer (NK) cells in vivo, we confirmed that circulating miR-517a-3p was delivered into maternal NK cells as it was into Jurkat cells in vitro. Placenta-associated miR-517a-3p was incorporated into maternal NK cells in the third trimester, and it was rapidly cleared after delivery. Expression levels of miR-517a-3p and its target mRNA PRKG1 were inversely correlated in NK cells before and after delivery. These in vitro and in vivo results suggest that exosome-mediated transfer of placenta-associated miRNAs and subsequent modulation of their target genes occur in maternal NK cells. The present study provides novel insight into our understanding of placentamaternal communication.