Circ_0007121 Facilitates Trophoblastic Cell Proliferation, Migration, and Invasion via the Regulation of the miR-421/ZEB1 Axis in Preeclampsia

Current understanding of circular RNAs in preeclampsia

Preeclampsia (PE) is a multiple organ and system disease that seriously threatens the safety of the mother and infant during pregnancy, and has a profound impact on the morbidity and mortality of the mother and new babies. Presently, there are no remedies for cure of PE as to the mechanisms of PE are still unclear, and the only way to eliminate the symptoms is to deliver the placenta. Thus, new therapeutic targets for PE are urgently needed. Approximately 95% of human transcripts are thought to be non-coding RNAs, and the roles of them are to be increasingly recognized of great importance in various biological processes. Circular RNAs (circRNAs) are a class of non-coding RNAs, with no 5' caps and 3' polyadenylated tails, commonly produced by back-splicing of exons. The structure of circRNAs makes them more stable than their counterparts. Increasing evidence shows that circRNAs are involved in the pathogenesis of PE, but the biogenesis, functions, and mechanisms of circRNAs in PE are poorly understood. In the present review, we mainly summarize the biogenesis, functions, and possible mechanisms of circRNAs in the development and progression of PE, as well as opportunities and challenges in the treatment and prevention of PE.

MicroRNA analysis of medium/large placenta extracellular vesicles in normal and preeclampsia pregnancies

Background

Preeclampsia (PE) is a hypertensive disorder of pregnancy, affecting 2%-8% of pregnancies worldwide, and is the leading cause of adverse maternal and fetal outcomes. The disease is characterized by oxidative and cellular stress and widespread endothelial dysfunction. While the precise mechanisms are not entirely understood, the pathogenesis of PE is closely linked to placental dysfunction and, to some extent, syncytiotrophoblast extracellular vesicle release (STB-EVs). These vesicles can be divided into the less well-studied medium/large EVs (220-1,000 nm) released in response to stress and small EVs (<220 nm) released as a component of intercellular communication. The previously described production of m/lSTB-EVs in response to cellular stress combined with the overwhelming occurrence of cellular and oxidative stress in PE prompted us to evaluate the microRNAome of PE m/lSTB-EVs. We hypothesized that the microRNAome profile of m/lSTB-EVs is different in PE compared to normal pregnancy (NP), which might permit the identification of potential circulating biomarkers not previously described in PE.

Methods/study design

We performed small RNA sequencing on medium/large STB-EVs isolated from PE and NP placentae using dual-lobe ex vivo perfusion. The sequencing data was bioinformatically analyzed to identify differentially regulated microRNAs. Identified microRNAs were validated with quantitative PCR analysis. We completed our analysis by performing an in-silico prediction of STB-EV mechanistic pathways.

Results

We identified significant differences between PE and NP in the STB-EVs micro ribonucleic acid (microRNA) profiles. We verified the differential expression of hsa-miR-193b-5p, hsa-miR-324-5p, hsa-miR-652-3p, hsa-miR-3196, hsa-miR-9-5p, hsa-miR-421, and hsa-miR-210-3p in the medium/large STB-EVs. We also confirmed the differential abundance of hsa-miR-9-5p in maternal serum extracellular vesicles (S EVs). In addition, we integrated the results of these microRNAs into the previously published messenger RNA (mRNA) data to better understand the relationship between these biomolecules.

Conclusions

We identified a differentially regulated micro-RNA, hsa-miR-9-5p, that may have biomarker potential and uncovered mechanistic pathways that may be important in the pathophysiology of PE.

The role of circular RNA in preeclampsia: From pathophysiological mechanism to clinical application

Preeclampsia (PE) is a common pregnancy-induced hypertension disorder that poses a significant threat to the health of pregnant women and fetuses, and has become a leading cause of maternal, fetal, and neonatal mortality. Currently, the therapy strategy for PE is mainly prevention management and symptomatic treatment, and only delivery can completely terminate PE. Therefore, a deeper understanding of the pathogenesis of PE is needed to make treatment and prevention more effective and targeted. With the deepening of molecular etiology research, circular RNAs (circRNAs) have been found to be widely involved in various processes of PE pathogenesis. As a kind of RNA with a special "head to tail" loop structure, the characteristics of circRNAs enable them to play diverse roles in the pathophysiology of PE, and can also serve as ideal biomarkers for early prediction and monitoring progression of PE. In this review, we summarized the latest research on PE-related circRNAs, trying to elucidate the unique or shared roles of circRNAs in various pathophysiological mechanisms of PE, aiming to provide a whole picture of current research on PE-related circRNAs, and extend a new perspective for the precise screening and targeted therapy of PE.

Hsa_circ_0002348 regulates trophoblast proliferation and apoptosis through miR-126-3p/BAK1 axis in preeclampsia

BACKGROUND

Preeclampsia is a common pregnancy complication characterized by high blood pressure and damage to organs. Abnormal placenta and vascular function can lead to preeclampsia. Accumulating evidence has suggested a potential link between circular RNAs (circRNAs) and preeclampsia. As a placenta and endothelial-expressed circRNA, hsa_circ_0002348, may be promising to be the novel molecular target for preeclampsia. However, the function and mechanism of hsa_circ_0002348 in preeclampsia has not been elucidated.

MATERIALS AND METHODS

An overlap analysis of two circRNA profiles from placenta and endothelial cells was used to identify a functionally unknown circRNA, hsa_circ_0002348. Quantitative real-time PCR (qRT-PCR) and in situ hybridization (ISH) were used to detect its expression in the trophoblast cells and placental tissues. The mouse model of lipopolysaccharide (LPS)-induced preeclampsia was established to determine the in vivo role of hsa_circ_0002348. RNA immunoprecipitation (RIP), Luciferase reporter assay, qRT-PCR, western blot, gain- and loss-of-function and rescue experiments were conducted to uncover the role of hsa_circ_0002348 and its interaction with miR-126-3p and BAK1 in regulating trophoblast proliferation and apoptosis. Fluorescence in situ hybridization (FISH) and Immunohistochemistry (IHC) were performed to examine the expression of miR-126-3p and BAK1 in mice and human placentas, respectively.

RESULTS

Hsa_circ_0002348 was significantly increased in the preeclampsia placentas, and positively correlated with the severity of preeclampsia patients' clinical manifestations. Its overexpression exacerbated preeclampsia-like features in the mouse model of LPS-induced preeclampsia. Functionally, hsa_circ_0002348 was found to inhibit trophoblast proliferation and promote trophoblast apoptosis. Mechanistically, hsa_circ_0002348, as an endogenous miR-126-3p sponge, upregulated the expression of BAK1. Additionally, both hsa_circ_0002348 knockdown and miR-126-3p overexpression enhanced the mammalian target of rapamycin (mTOR) and ERK1/2 signaling pathway.

CONCLUSIONS

Hsa_circ_0002348 might be a novel regulator of trophoblast proliferation and apoptosis through miR-126-3p/BAK1 axis in preeclampsia, which may serve as a potential target for detecting and treating preeclampsia.

Re-expression of circ_0043610 contributes to trophoblast dysfunction through the miR-558/RYBP pathway in preeclampsia

An increasing number of data have shown the pathogenesis of preeclampsia (PE) involves circular RNA (circRNA). The study aims to investigate the function and the potential mechanism of circ_0043610 in PE. The study was performed on two human placental trophoblastic cell lines (JEG-3 and HTR-8/SVneo). The expression of circ_0043610, microRNA-558 (miR-558), and RING1 and YY1 binding protein (RYBP) was detected by quantitative real-time polymerase chain reaction. The protein levels of N-cadherin, E-cadherin, and RYBP were assessed by Western blotting. Cell viability, proliferation, apoptosis, invasion, and migration were evaluated by cell counting kit-8, 5-Ethynyl-29-deoxyuridine, flow cytometry analysis, transwell invasion assay, and wound-healing assay, respectively. Dual-luciferase reporter assay, RNA immunoprecipitation assay, and RNA pull-down assay were performed to identify the associations among circ_0043610, miR-558, and RYBP. Compared with normal placental controls, the increased expression of circ_0043610 and RYBP and the decreased miR-558 expression were detected in PE placental tissues. The overexpression of circ_0043610 led to decreased trophoblast cell proliferation, invasion, and migration but increased cell apoptosis. Mechanistically, circ_0043610 acted as a miR-558 sponge, and miR-558 bound to RYBP. Besides, miR-558 introduction remitted circ_0043610-mediated effects in JEG-3 and HTR-8/SVneo cells. Moreover, RYBP participated in the regulation of miR-558 on trophoblast cell behaviors. Further, the ectopic expression of circ_0043610 led to RYBP upregulation through miR-558. Circ_0043610 induced RYBP production to promote trophoblast dysfunction by binding to miR-558 in PE.

Role of microRNAs in trophoblast invasion and spiral artery remodeling: Implications for preeclampsia

It is now well-established that microRNAs (miRNAs) are important regulators of gene expression. The role of miRNAs in placental development and trophoblast function is constantly expanding. Trophoblast invasion and their ability to remodel uterine spiral arteries are essential for proper placental development and successful pregnancy outcome. Many miRNAs are reported to be dysregulated in pregnancy complications, especially preeclampsia and they exert various regulatory effects on trophoblasts. In this review, we provide a brief overview of miRNA biogenesis and their mechanism of action, as well as of trophoblasts differentiation, invasion and spiral artery remodeling. We then discuss the role of miRNAs in trophoblasts invasion and spiral artery remodeling, focusing on miRNAs that have been thoroughly investigated, especially using multiple model systems. We also discuss the potential role of miRNAs in the pathogenesis of preeclampsia.

Regulatory roles of non-coding RNAs and m6A modification in trophoblast functions and the occurrence of its related adverse pregnancy outcomes

Adverse pregnancy outcomes, such as preeclampsia, gestational diabetes mellitus, fetal growth restriction, and recurrent miscarriage, occur frequently in pregnant women and might further induce morbidity and mortality for both mother and fetus. Increasing studies have shown that dysfunctions of human trophoblast are related to these adverse pregnancy outcomes. Recent studies also showed that environmental toxicants could induce trophoblast dysfunctions. Moreover, non-coding RNAs (ncRNAs) have been reported to play important regulatory roles in various cellular processes. However, the roles of ncRNAs in the regulation of trophoblast dysfunctions and the occurrence of adverse pregnancy outcomes still need to be further investigated, especially with exposure to environmental toxicants. In this review, we analyzed the regulatory mechanisms of ncRNAs and m6A methylation modification in the dysfunctions of trophoblast cells and the occurrence of adverse pregnancy outcomes and also summarized the harmful effects of environmental toxicants. In addition to DNA replication, mRNA transcription, and protein translation, ncRNAs and m6A modification might be considered as the fourth and fifth elements that regulate the genetic central dogma, respectively. Environmental toxicants might also affect these processes. In this review, we expect to provide a deeper scientific understanding of the occurrence of adverse pregnancy outcomes and to discover potential biomarkers for the diagnosis and treatment of these outcomes.

Circular RNAs in Pregnancy and the Placenta

The emerging field of circular RNAs (circRNAs) has identified their novel roles in the development and function of many cancers and inspired the interest of many researchers. circRNAs are also found throughout the healthy body, as well as in other pathological states, but while research into the function and abundance of circRNAs has progressed, our overall understanding of these molecules remains primitive. Importantly, recent studies are elucidating new roles for circRNAs in pregnancy, particularly in the placenta. Given that many of the genes responsible for circRNA production in cancer are also highly expressed in the placenta, it is likely that the same genes act in the production of circRNAs in the placenta. Furthermore, placental development can be referred to as ‘controlled cancer’, as it shares many key signalling pathways and hallmarks with tumour growth and metastasis. Hence, the roles of circRNAs in this field are important to study with respect to pregnancy success but also may provide novel insights for cancer progression. This review illuminates the known roles of circRNAs in pregnancy and the placenta, as well as demonstrating differential placental expressions of circRNAs between complicated and uncomplicated pregnancies.