BeWo exomeres are enriched for bioactive extracellular placenta-specific C19MC miRNAs.

Extracellular vesicles (EVs), including exosomes, are carriers of extracellular microRNAs (miRNAs). Exomeres, non-vesicular extracellular nanoparticles (NVEPs), are novel extracellular cargo carriers. However, little is known of the characteristics of placental trophoblast-derived exomeres. In this study, we characterized trophoblast-derived exomeres and investigated the cell-cell communication of placenta-specific miRNAs carried by those exomeres using an in vitro model system (BeWo trophoblasts and Jurkat T cells). BeWo exomeres (∼ 40 nm diameter) had pilling-like nanoparticle structures, which were distinct from cup-shaped exosomes (∼ 90-110 nm diameter). BeWo cells secreted more exomeres than exosomes. Exomeres were positive for AGO2 but negative for exosome markers (CD63, CD9, CD81, FLOT1, and TSG101). The levels of placenta-specific miRNAs in exomeres were significantly higher than in exosomes. In a cell-cell communication analysis using a placenta-specific miRNA, BeWo exomeres delivered significantly more miR-517a-3p to recipient Jurkat cells compared with exosomes. Moreover, exomere-miR-517a-3p significantly reduced the expression of PRKG1 in miR-517a-3p-inhibitor (-) Jurkat cells compared with miR-517a-3p-inhibitor (+) cells, suggesting that miR-517a-3p inhibition reversed the exomere-miR-517a-3p-mediated repression of PRKG1 expression in recipient cells. Therefore, BeWo trophoblast exomeres are enriched with bioactive extracellular placenta-specific miRNAs, which were formerly considered to be carried by exosomes. Our findings provide insight into trophoblast-derived NVEPs.

Cytoplasmic and nuclear DROSHA in human villous trophoblasts.

In villous trophoblasts, DROSHA is a key ribonuclease III enzyme that processes pri-microRNAs (pri-miRNAs) into pre-miRNAs at the placenta-specific, chromosome 19 miRNA cluster (C19MC) locus. However, little is known of its other functions. We performed formaldehyde crosslinking, immunoprecipitation, and sequencing (fCLIP-seq) analysis of terminal chorionic villi to identify DROSHA-binding RNAs in villous trophoblasts. In villous trophoblasts, DROSHA predominantly generated placenta-specific C19MC pre-miRNAs, including antiviral C19MC pre-miRNAs. The fCLIP-seq analysis also identified non-miRNA transcripts with hairpin structures potentially capable of binding to DROSHA (e.g., SNORD100 and VTRNA1-1). Moreover, in vivo immunohistochemical analysis revealed DROSHA in the cytoplasm of villous trophoblasts. DROSHA was abundant in the cytoplasm of villous trophoblasts, particularly in the apical region of syncytiotrophoblast, in the full-term placenta. Furthermore, in BeWo trophoblasts infected with Sindbis virus (SINV), DROSHA translocated to the cytoplasm and recognized the genomic RNA of SINV. Therefore, in trophoblasts, DROSHA not only regulates RNA metabolism, including the biogenesis of placenta-specific miRNAs, but also recognizes viral RNAs. After SINV infection, BeWo DROSHA-binding VTRNA1-1 was significantly upregulated, and cellular VTRNA1-1 was significantly downregulated, suggesting that DROSHA soaks up VTRNA1-1 in response to viral infection. These results suggest that the DROSHA-mediated recognition of RNAs defends against viral infection in villous trophoblasts. Our data provide insight into the antiviral functions of DROSHA in villous trophoblasts of the human placenta.

Interstitial Pregnancy in the Third Trimester with Severe Preeclampsia: A Case Report and Literature Review.

An interstitial pregnancy that continues beyond the second trimester is a rare phenomenon. We report a patient with an interstitial pregnancy undiagnosed until the third trimester. A multiparous woman was referred to us because of preeclampsia at 26 weeks of gestation. The placental position was the right fundus, and color Doppler ultrasound revealed myometrial thinning and subplacental hypervascularity, leading to a suspicion of placenta accreta spectrum (PAS). Emergency cesarean section was performed at 281/7 weeks of gestation due to severe preeclampsia. The right tubal horn to the isthmus of the fallopian tube bulged with placental adhesion and a part of the tube had ruptured, with the omentum adhering to the ruptured part. Interstitial and tubal isthmic pregnancy with uterine rupture was diagnosed.