Our objective was to determine the expression of the elements of the Lin28/Let-7 system, and related microRNAs (miRNAs), in early stages of human placentation and ectopic pregnancy, as a means to assess the potential role of this molecular hub in the pathogenesis of ectopic gestation. Seventeen patients suffering from tubal ectopic pregnancy (cases) and forty-three women with normal on-going gestation that desired voluntary termination of pregnancy (VTOP; controls) were recruited for the study. Embryonic tissues were subjected to RNA extraction and quantitative PCR analyses for LIN28B, Let-7a, miR-132, miR-145 and mir-323-3p were performed. Our results demonstrate that the expression of LIN28B mRNA was barely detectable in embryonic tissue from early stages of gestation and sharply increased thereafter to plateau between gestational weeks 7–9. In contrast, expression levels of Let-7, mir-132 and mir-145 were high in embryonic tissue from early gestations (≤6-weeks) and abruptly declined thereafter, especially for Let-7. Opposite trends were detected for mir-323-3p. Embryonic expression of LIN28B mRNA was higher in early stages (≤6-weeks) of ectopic pregnancy than in normal gestation. In contrast, Let-7a expression was significantly lower in early ectopic pregnancies, while miR-132 and miR-145 levels were not altered. Expression of mir-323-3p was also suppressed in ectopic embryonic tissue. We are the first to document reciprocal changes in the expression profiles of the gene encoding the RNA-binding protein, LIN28B, and the related miRNAs, Let-7a, mir-132 and mir-145, in early stages of human placentation. This finding suggests the potential involvement of LIN28B/Let-7 (de)regulated pathways in the pathophysiology of ectopic pregnancy in humans.

Our objective was to investigate the miRNA profile of embryonic tissues in ectopic pregnancies (EPs) and controlled abortions (voluntary termination of pregnancy; VTOP). Twenty-three patients suffering from tubal EP and twenty-nine patients with a normal ongoing pregnancy scheduled for a VTOP were recruited. Embryonic tissue samples were analyzed by miRNA microarray and further validated by real time PCR. Microarray studies showed that four miRNAs were differentially downregulated (hsa-mir-196b, hsa-mir-30a, hsa-mir-873, and hsa-mir-337-3p) and three upregulated (hsa-mir-1288, hsa-mir-451, and hsa-mir-223) in EP compared to control tissue samples. Hsa-miR-196, hsa-miR-223, and hsa-miR-451 were further validated by real time PCR in a wider population of EP and control samples. We also performed a computational analysis to identify the gene targets and pathways which might be modulated by these three differentially expressed miRNAs. The most significant pathways found were the mucin type O-glycan biosynthesis and the ECM-receptor-interaction pathways. We also checked that the dysregulation of these three miRNAs was able to alter the expression of the gene targets in the embryonic tissues included in these pathways such as GALNT13 and ITGA2 genes. In conclusion, analysis of miRNAs in ectopic and eutopic embryonic tissues shows different expression patterns that could modify pathways which are critical for correct implantation, providing new insights into the understanding of ectopic implantation in humans.

Background: Ectopic pregnancy (EP) is a life-threatening condition, for which novel screening tools enabling early accurate diagnosis would improve clinical outcomes. Kisspeptins, encoded by KISS1, play an essential role in human reproduction, at least partially by regulating placental function and possibly embryo implantation. Kisspeptin levels are massively elevated in normal pregnancy and reportedly altered in various gestational pathologies. Yet, the pathophysiological role of KISS1/kisspeptin in EP has not been investigated previously. Methods: Measurements of plasma kisspeptins and KISS1 expression analyses in human embryonic/placental tissue were conducted in EP and their controls (women undergoing voluntary termination of pregnancy, VTOP) during early gestational window (<12-wks). Putative miRNA regulators of KISS1 were predicted in silico, followed by expression analyses of selected miRNAs and validation of repressive interactions in vitro. Circulating levels of these miRNAs were also assayed in EP vs. VTOP. Results: Circulating kisspeptins gradually increased during the first trimester of normal pregnancy, but were massively reduced in EP. This profile correlated with expression levels of KISS1 in human embryonic/placental tissue, which increased in VTOP but remained suppressed in EP. Bioinformatic predictions and expression analyses identified miR-27b-3p and miR-324-3p as putative repressors of KISS1 in human embryonic/placental tissue at <12-wks gestation, when expression of both miRNAs was low in VTOP controls, but significantly increased in EP. Yet, a significant repressive interaction was documented only for miR-324-3p, occurring at the predicted 3'-UTR of KISS1. Interestingly, circulating levels of miR-324-3p, but not of miR-27b-3p, were dramatically suppressed in EP, despite elevated tissue expression of the pre-miRNA, suggesting defective export in EP. A decision-tree model using kisspeptin and miR-324-3p levels was successful in discriminating EP vs. VTOP, with a receiver-operating characteristic (ROC) AUC of 0.95 ± 0.02 (95% CI). Conclusions: Our results document a massive down-regulation of KISS1/kisspeptins in early stages of EP, likely via a repressive interaction with miR-324-3p. Our data identify circulating kisspeptins and miR-324-3p as novel biomarkers for accurate for screening of EP at early gestational ages.

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