Human Villous Trophoblasts Express and Secrete Placenta-Specific MicroRNAs into Maternal Circulation via Exosomes1

Abstract

In this study, we performed small RNA library sequencing using human placental tissues to identify placenta-specific miRNAs. We also tested the hypothesis that human chorionic villi could secrete miRNAs extracellularly via exosomes, which in turn enter into maternal circulation. By small RNA library sequencing, most placenta-specific miRNAs (e.g., MIR517A) were linked to a miRNA cluster on chromosome 19. The miRNA cluster genes were differentially expressed in placental development. Subsequent validation by real-time PCR and in situ hybridization revealed that villous trophoblasts express placenta-specific miRNAs. The analysis of small RNA libraries from the blood plasma showed that the placenta-specific miRNAs are abundant in the plasma of pregnant women. By real-time PCR, we confirmed the rapid clearance of the placenta-specific miRNAs from the plasma after delivery, indicating that such miRNAs enter into maternal circulation. By using the trophoblast cell line BeWo in culture, we demonstrated that miRNAs are indeed extracellularly released via exosomes. Taken together, our findings suggest that miRNAs are exported from the human placental syncytiotrophoblast into maternal circulation, where they could target maternal tissues. Finally, to address the biological functions of placenta-specific miRNAs, we performed a proteome analysis of BeWo cells transfected with MIR517A. Bioinformatic analysis suggests that this miRNA is possibly involved in tumor necrosis factor-mediated signaling. Our data provide important insights into miRNA biology of the human placenta.

Identification of aberrant circulating miRNAs in Parkinson's disease plasma samples

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Influence of maternal BMI on the exosomal profile during gestation and their role on maternal systemic inflammation

“…In this study, we demonstrated that maternal BMI is a factor that explains for >20% of 401 the observed variation in plasma exosomes concentration (Figure 3 has not been established, however, the levels of placental miRNA, which are secreted 434 from placental cells into exosomes, decrease dramatically after delivery [51]. of exosomes (100 µg/ml) isolated from plasma obtained from lean, overweight (OW), 687…”

Horizontal transfer of microRNAs: molecular mechanisms and clinical applications

“…Recent studies have demonstrated that functional miRNAs are also horizontally transferred via this mechanism. The presence of a miRNA pool has been reported in exosomes and shedding vesicles derived from a variety of sources, including mast cells (Valadi et al, 2007), blood (Hunter et al, 2008), stem cells (Yuan et al, 2009;Collino et al, 2010), adipocytes (Ogawa et al, 2010;Müller et al, 2011), syncytiotrophoblasts (Luo et al, 2009) and milk (Hata et al, 2010). Valadi et al pioneered the description of the so-called "exosomal shuttle miRNA," showing that exosomes isolated from a mouse mast cell line MC/9, a human mast cell line HMC-1 and from primary bone marrow-derived mast cells contain substantial miRNA populations (Valadi et al, 2007).…”

“…However, the biological significance of miRNAs derived from adipocyte microvesicles remains uncertain at this moment. In a different system, Luo et al hypothesized that syncytiotrophoblasts secrete miRNAs into maternal circulation via exosomes (Luo et al, 2009). In an attempt to prove this hypothesis, they isolated exosomes from the villous trophoblast model cell line, BeWo.…”

“…In an attempt to prove this hypothesis, they isolated exosomes from the villous trophoblast model cell line, BeWo. The placenta-specific miRNA miR-517a was detected in the exosome-enriched fraction (Luo et al, 2009). This finding suggests that placenta-specific miRNAs are released extracellularly via exosomes from chorionic villous trophoblasts into maternal circulation, where they could target maternal tissues (e.g.…”