The profile analysis of circular RNAs in human placenta of preeclampsia

Role of circular RNAs in preeclampsia (Review)

Preeclampsia (PE) is a hypertensive disorder of pregnancy characterized by new-onset hypertension and proteinuria after 20 weeks of gestation, which affects 3-8% of pregnant individuals worldwide each year. Prevention, diagnosis and treatment of PE are some of the most important problems faced by obstetrics. There is growing evidence that circular RNAs (circRNAs) are involved in the pathogenesis of PE. The present review summarizes the research progress of circRNAs and then describes the expression patterns of circRNAs in PE and their functional mechanisms affecting PE development. The role of circRNAs as biomarkers for the diagnosis of PE, and the research status of circRNAs in PE are summarized in the hope of finding novel strategies for the prevention and treatment of PE.

Value of Non-Coding RNA Expression in Biofluids to Identify Patients at Low Risk of Pathologies Associated with Pregnancy

Pregnancy-related complications (PRC) impact maternal and fetal morbidity and mortality and place a huge burden on healthcare systems. Thus, effective diagnostic screening strategies are crucial. Currently, national and international guidelines define patients at low risk of PRC exclusively based on their history, thus excluding the possibility of identifying patients with de novo risk (patients without a history of disease), which represents most women. In this setting, previous studies have underlined the potential contribution of non-coding RNAs (ncRNAs) to detect patients at risk of PRC. However, placenta biopsies or cord blood samples are required, which are not simple procedures. Our review explores the potential of ncRNAs in biofluids (fluids that are excreted, secreted, or developed because of a physiological or pathological process) as biomarkers for identifying patients with low-risk pregnancies. Beyond the regulatory roles of ncRNAs in placental development and vascular remodeling, we investigated their specific expressions in biofluids to determine favorable pregnancy outcomes as well as the most frequent pathologies of pregnant women. We report distinct ncRNA panels associated with PRC based on omics technologies and subsequently define patients at low risk. We present a comprehensive analysis of ncRNA expression in biofluids, including those using next-generation sequencing, shedding light on their predictive value in clinical practice. In conclusion, this paper underscores the emerging significance of ncRNAs in biofluids as promising biomarkers for risk stratification in PRC. The investigation of ncRNA expression patterns and their potential clinical applications is of diagnostic, prognostic, and theragnostic value and paves the way for innovative approaches to improve prenatal care and maternal and fetal outcomes.

Circ_0030042 inhibits trophoblast cell growth, invasion and epithelial-mesenchymal transition process in preeclampsia via miR-942-5p/LITAF

BACKGROUND

There is increasing evidence that circular RNAs (circRNAs) are involved in the processes of preeclampsia (PE). Circ_0030042 was found to be abnormally expressed in PE patients. However, the role and molecular mechanism of circ_0030042 in PE progression remains unclear.

METHODS

Quantitative real-time PCR was used for determining the expression of circ_0030042, microRNA (miR)- 942-5p and lipopolysaccharide induced TNF-α factor (LITAF). Trophoblast cell functions were determined using cell counting kit 8 assay, EdU assay, flow cytometry and transwell assay. The protein levels of epithelial-mesenchymal transition (EMT)-related markers and LITAF were examined using western blot analysis. Dual-luciferase reporter assay and RNA pull-down assay were used to verify RNA interaction.

RESULTS

Circ_0030042 had an elevated expression in PE patients, and its overexpression inhibited trophoblast cell growth, invasion, and EMT process. Circ_0030042 served as miR-942-5p sponge, and miR-942-5p inhibitor also reversed the regulation of circ_0030042 on trophoblast cell growth, invasion and EMT process. LITAF was targeted by miR-942-5p, and its knockdown abolished the inhibition effect of miR-942-5p on trophoblast cell growth, invasion, and EMT process. Also, circ_0030042 regulated LITAF expression via sponging miR-942-5p.

CONCLUSION

Circ_0030042 regulated trophoblast cell growth, invasion, and EMT process via the miR-942-5p/LITAF axis, providing a novel insight for PE treatment.

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.

Identification of m6A Modification Regulated by Dysregulated circRNAs in Decidua of Recurrent Pregnancy Loss

N6-methyladenosine (m6A) modification is a prevalent modification of messenger ribonucleic acid (mRNA) in eukaryote cells and is closely associated with recurrent pregnancy loss (RPL). Circular RNAs (circRNAs) play critical roles in embryo implantation, trophoblast invasion and immune balance, which are important events during pregnancy. However, how m6A modification is regulated by circRNAs and the potential regulatory mechanism of circRNAs on RPL occurrence remain largely unclassified. We displayed the expression profiles of circRNAs and mRNAs in the decidua of normal pregnancies and RPL patients based on circRNA sequencing and the Gene Expression Omnibus database. A total of 936 differentially expressed circRNAs were identified, including 509 upregulated and 427 downregulated circRNAs. Differentially expressed circRNAs were enriched in immune, metabolism, signaling and other related pathways via the analysis of Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. The competitive endogenous RNA (ceRNA) network was predicted to supply the possible role of circRNAs in RPL occurrence, and we further analyzed the profiles of nine m6A regulators (seven readers, one writer and one eraser) managed by circRNAs in this network. We also showed the expression profiles of circRNAs in the serum, trying to seek a potential biomarker to help in the diagnosis of RPL. These data imply that circRNAs are involved in pathogenesis of RPL by changing immune activities, metabolism and m6A modification in the ceRNA network. Our study might provide assistance in exploring the pathogenesis and diagnosis of RPL.

circ_0014736 induces GPR4 to regulate the biological behaviors of human placental trophoblast cells through miR-942-5p in preeclampsia

Previous studies have indicated that the development of preeclampsia (PE) involves the regulation of circular RNA (circRNA). However, the role of hsa_circ_0014736 (circ_0014736) in PE remains unknown. Thus, the study proposes to reveal the function of circ_0014736 in the pathogenesis of PE and the underlying mechanism. The results showed that circ_0014736 and GPR4 expression were significantly upregulated, while miR-942-5p expression was downregulated in PE placenta tissues when compared with normal placenta tissues. circ_0014736 knockdown promoted the proliferation, migration, and invasion of placenta trophoblast cells (HTR-8/SVneo) and inhibited apoptosis; however, circ_0014736 overexpression had the opposite effects. circ_0014736 functioned as a sponge for miR-942-5p and regulated HTR-8/SVneo cell processes by interacting with miR-942-5p. Additionally, GPR4, a target gene of miR-942-5p, was involved in miR-942-5p-mediated actions in HTR-8/SVneo cells. Moreover, circ_0014736 stimulated GPR4 production through miR-942-5p. Collectively, circ_0014736 inhibited HTR-8/SVneo cell proliferation, migration, and invasion and induced cell apoptosis through the miR-942-5p/GPR4 axis, providing a possible target for the treatment of PE.

The Role of Non-Coding RNAs in the Human Placenta

Non-coding RNAs (ncRNAs) play a central and regulatory role in almost all cells, organs, and species, which has been broadly recognized since the human ENCODE project and several other genome projects. Nevertheless, a small fraction of ncRNAs have been identified, and in the placenta they have been investigated very marginally. To date, most examples of ncRNAs which have been identified to be specific for fetal tissues, including placenta, are members of the group of microRNAs (miRNAs). Due to their quantity, it can be expected that the fairly larger group of other ncRNAs exerts far stronger effects than miRNAs. The syncytiotrophoblast of fetal origin forms the interface between fetus and mother, and releases permanently extracellular vesicles (EVs) into the maternal circulation which contain fetal proteins and RNA, including ncRNA, for communication with neighboring and distant maternal cells. Disorders of ncRNA in placental tissue, especially in trophoblast cells, and in EVs seem to be involved in pregnancy disorders, potentially as a cause or consequence. This review summarizes the current knowledge on placental ncRNA, their transport in EVs, and their involvement and pregnancy pathologies, as well as their potential for novel diagnostic tools.

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.

CircPAPPA Regulates the Proliferation, Migration, Invasion, Apoptosis, and Cell Cycle of Trophoblast Cells Through the miR-3127-5p/HOXA7 Axis

Abnormal function of trophoblast cells is one of the important causes of preeclampsia (PE). Circular RNA (circRNA) is thought to be involved in the regulation of various diseases progression, including PE. However, the role of circRNA pregnancy-associated plasma protein A (circPAPPA) in PE is less studied. The expression levels of circPAPPA, miR-3127-5p, and homeobox A7 (HOXA7) were determined by quantitative real-time PCR. Cell proliferation was evaluated using MTT assay and colony formation assay. Besides, flow cytometry was used to detect cell apoptosis and cell cycle distribution. In addition, the interaction between miR-3127-5p and circPAPPA or HOXA7 was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assay. CircPAPPA was lowly expressed in the placental tissues of PE patients. Knockdown of circPAPPA inhibited proliferation, migration, and invasion, while induced apoptosis and cell cycle arrest in trophoblast cells. MiR-3127-5p could be targeted by circPAPPA, and its inhibitor reversed the effect of circPAPPA silencing on the biological function of trophoblast cells. Moreover, HOXA7 was a target of miR-3127-5p. HOXA7 overexpression reversed the effect of miR-3127-5p on the biological function of trophoblast cells. Our research indicated that circPAPPA positively regulated the biological function of trophoblast cells to mediate the progression of PE by miR-3127-5p/HOXA7 axis, which suggested that circPAPPA might be a potential biomarker for PE.

Placental transcriptome sequencing combined with bioinformatics predicts potential genes and circular RNAs associated with hemoglobin Bart's hydrops fetalis syndrome

AIM

Hemoglobin Bart's hydrops fetalis syndrome (BHFS) is the most severe form of α-thalassemia. Histological alternations can be observed in placenta, but placental transcriptome profile and circular RNAs have not been studied in this disease. The aim of this study was to define the placental transcriptional changes and find relevant circular RNAs in BHFS.

METHODS

We performed high-throughput RNA sequencing to detect placental samples from fetuses affected by BHFS (n = 5) and normal fetuses (NF, n = 5), quantitative reverse transcription polymerase chain reaction (RT-qPCR), and Sanger sequencing to validate the differentially expressed circRNAs and their potentially related miRNAs (BHFS, n = 22; NF, n = 11). Bioinformatics methods were performed for further analysis.

RESULTS

Our results showed 152 differentially expressed genes (DEGs), 112 circRNAs, and 45 microRNAs that were differentially expressed. DEGs were found to be involved in Gene Ontology terms related to gas transport, cell adhesion, oxidative stress, organ development, hemopoiesis, and others. RT-qPCR results showed that hsa_circ_0003961 and hsa_circ_0006687 were upregulated (p < 0.05). The competing endogenous RNA and co-expression networks showed that hsa_circ_0003961 and hsa_circ_0006687 were connected with 3 miRNAs and some DEGs, including cell adhesion genes (e.g., CLDN19), hemoglobin related genes (e.g., SOX6 and HBZ) and angiogenesis related genes (e.g., EPHB2). Downregulations of hsa-miR-1299 and hsa-miR-625-5p in ceRNA network were also validated by RT-qPCR. Gene set enrichment analysis results for the two circRNAs showed that some gene sets associated with cell adhesion, hematopoietic system and apoptosis were significantly enriched.

CONCLUSIONS

Our study characterized the placental transcriptome of BHFS. The circRNAs hsa_circ_0003961 and hsa_circ_0006687 in placenta may be relevant to BHFS.

Circular RNA PUM1 (CircPUM1) attenuates trophoblast cell dysfunction and inflammation in recurrent spontaneous abortion via the MicroRNA-30a-5p (miR-30a-5p)/JUNB axis

Recurrent spontaneous abortion (RSA) is a threat to human reproductive health worldwide. CircPUM1 has been reported to participate in the pathogenesis of various diseases. However, there has been no report on its association with RSA yet. In this study, gene expressions were examined by RT-qPCR. Protein levels of JUNB and cleaved caspases-3 were detected by Western blotting. ELISA was used to detect TNF-α, IL-6, and IL-8 levels. Cell viability, migration, invasion, and apoapsis were analyzed using CCK-8, transwell, and flow cytometry assays. The association between miR-30a-5p and circPUM1 or JUNB was identified by bioinformatics analysis, dual-luciferase reporter assay, and RIP assay. Herein, we found circPUM1 was significantly downregulated in RSA placental samples. CircPUM1 knockdown induced decreased proliferation, migration, and invasion, but increased apoptosis, pro-apoptotic protein (cleaved caspases-3) level, and proinflammatory factor (TNF-α, IL-6, and IL-8) secretion in trophoblast cells. Furthermore, we confirmed that circPUM1 was a sponge for miR-30a-5p, and JUNB was directly targeted by miR-30a-5p. It was demonstrated that miR-30a-5p inhibition could reverse trophoblast cell dysfunction and inflammation induced by circPUM1 knockdown. In addition, we found that JUNB expression was negatively modulated by miR-30a-5p and positively regulated by circPUM1. Moreover, circPUM1 inhibition exacerbated dysfunction and inflammation in trophoblast cells via targeting JUNB. To sum up, our study indicated that circPUM1 could impair RSA occurrence and development by facilitating trophoblast cellular processes and protecting against inflammation via the miR-30a-5p/JUNB axis, providing a new target for the improvement of RSA diagnosis and treatment.

Roles of noncoding RNAs in preeclampsia

Preeclampsia (PE) is an idiopathic disease that occurs during pregnancy. It comprises multiple organ and system damage, and can seriously threaten the safety of the mother and infant throughout the perinatal period. As the pathogenesis of PE is unclear, there are few specific remedies. Currently, the only way to eliminate the clinical symptoms is to terminate the pregnancy. Although noncoding RNA (ncRNA) was once thought to be the "junk" of gene transcription, it is now known to be widely involved in pathological and physiological processes, including pregnancy-related disorders. Moreover, there is growing evidence that the unbalanced expression of specific ncRNA is involved in the pathogenesis of PE. In the present review, we summarize the expression patterns of ncRNAs, i.e., microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), and the functional mechanisms by which they affect the development of PE, and examine the clinical significance of ncRNAs as biomarkers for the diagnosis of PE. We also discuss the contributions made by genetic polymorphisms and epigenetic ncRNA regulation to PE. In the present review, we wish to explore and reinforce the clinical value of ncRNAs as noninvasive biomarkers of PE.

Current approaches and developments in transcript profiling of the human placenta

BACKGROUND

The placenta is the active interface between mother and foetus, bearing the molecular marks of rapid development and exposures in utero. The placenta is routinely discarded at delivery, providing a valuable resource to explore maternal-offspring health and disease in pregnancy. Genome-wide profiling of the human placental transcriptome provides an unbiased approach to study normal maternal–placental–foetal physiology and pathologies.

OBJECTIVE AND RATIONALE

To date, many studies have examined the human placental transcriptome, but often within a narrow focus. This review aims to provide a comprehensive overview of human placental transcriptome studies, encompassing those from the cellular to tissue levels and contextualize current findings from a broader perspective. We have consolidated studies into overarching themes, summarized key research findings and addressed important considerations in study design, as a means to promote wider data sharing and support larger meta-analysis of already available data and greater collaboration between researchers in order to fully capitalize on the potential of transcript profiling in future studies.

SEARCH METHODS

The PubMed database, National Center for Biotechnology Information and European Bioinformatics Institute dataset repositories were searched, to identify all relevant human studies using ‘placenta’, ‘decidua’, ‘trophoblast’, ‘transcriptome’, ‘microarray’ and ‘RNA sequencing’ as search terms until May 2019. Additional studies were found from bibliographies of identified studies.

OUTCOMES

The 179 identified studies were classifiable into four broad themes: healthy placental development, pregnancy complications, exposures during pregnancy and in vitro placental cultures. The median sample size was 13 (interquartile range 8–29). Transcriptome studies prior to 2015 were predominantly performed using microarrays, while RNA sequencing became the preferred choice in more recent studies. Development of fluidics technology, combined with RNA sequencing, has enabled transcript profiles to be generated of single cells throughout pregnancy, in contrast to previous studies relying on isolated cells. There are several key study aspects, such as sample selection criteria, sample processing and data analysis methods that may represent pitfalls and limitations, which need to be carefully considered as they influence interpretation of findings and conclusions. Furthermore, several areas of growing importance, such as maternal mental health and maternal obesity are understudied and the profiling of placentas from these conditions should be prioritized.

WIDER IMPLICATIONS

Integrative analysis of placental transcriptomics with other ‘omics’ (methylome, proteome and metabolome) and linkage with future outcomes from longitudinal studies is crucial in enhancing knowledge of healthy placental development and function, and in enabling the underlying causal mechanisms of pregnancy complications to be identified. Such understanding could help in predicting risk of future adversity and in designing interventions that can improve the health outcomes of both mothers and their offspring. Wider collaboration and sharing of placental transcriptome data, overcoming the challenges in obtaining sufficient numbers of quality samples with well-defined clinical characteristics, and dedication of resources to understudied areas of pregnancy will undoubtedly help drive the field forward.

Recent Advances of MicroRNAs, Long Non-coding RNAs, and Circular RNAs in Preeclampsia

Preeclampsia is a clinical syndrome characterized by multiple-organ dysfunction, such as maternal hypertension and proteinuria, after 20 weeks of gestation. It is a common cause of fetal growth restriction, fetal malformation, and maternal death. At present, termination of pregnancy is the only way to prevent the development of the disease. Non-coding RNAs, including microRNAs, long non-coding RNAs, and circular RNAs, are involved in important pathological and physiological functions in life cycle activities including ontogeny, reproduction, apoptosis, and cell reprogramming, and are closely associated with human diseases. Accumulating evidence suggests that non-coding RNAs are involved in the pathogenesis of preeclampsia through regulation of various physiological functions. In this review, we discuss the current evidence of the pathogenesis of preeclampsia, introduce the types and biological functions of non-coding RNA, and summarize the roles of non-coding RNA in the pathophysiological development of preeclampsia from the perspectives of oxidative stress, hypoxia, angiogenesis, decidualization, trophoblast invasion and proliferation, immune regulation, and inflammation. Finally, we briefly discuss the potential clinical application and future prospects of non-coding RNA as a biomarker for the diagnosis of preeclampsia.

Circular RNAs: Novel potential regulators in embryogenesis, female infertility, and pregnancy-related diseases

Circular RNAs (circRNAs) are endogenous noncoding RNAs with unique cyclic structures. Although they were previously considered as nonfunctional transcription byproducts, numerous studies have demonstrated that circRNAs regulate gene transcription and expression via different mechanisms. Reproductive health influences the quality of life and affects offspring propagation in women. CircRNAs have been found to modify pregnancy-related diseases, gynecologic cancers, polycystic ovary syndrome, aging, gamete, and embryo development. It's promising for circRNAs to be the novel diagnostic and therapeutic targets for multiple reproductive diseases. With the widespread application of assisted reproduction technology (ART), it has been revealed that circRNA identification contributes to estimating the quality of gametes and embryos, reflecting the success rate of ART. CRISPR-Cas9 gene editing technology has enabled the discovery of new roles of circRNAs. So far, the roles of circRNAs in the reproductive system remain poorly defined. In this review, we describe the classification and functions of circRNAs in embryogenesis and the female reproductive system diseases, revealing potential roles of circRNAs physiologically and pathologically. In so-doing, we provide ideas for developing circRNA-based therapeutic treatment and clinical application of various female reproductive system diseases.

Identification and comparison of circular RNAs in preeclampsia

Background

Preeclampsia (PE) is a pregnancy-specific syndrome, belongs to the gestational hypertension diseases category and is considered among the causes of maternal and perinatal mortality and morbidity. However, the pathogenesis of PE is still vague.

Methods

In the present study, the circular RNA (circRNA) expression patterns of normal pregnant women and PE patients were investigated using whole RNA sequencing.

Results

A total of 151 differential expressed circRNAs were identified including 121 upregulated and 30 downregulated ones. Functional and pathway enrichment analysis was conducted on the differentially expressed circRNAs using Gene Ontology and KEGG databases. The results of this analysis indicated that several crucial biological processes and pathways were enriched in PE patients. circRNA–microRNA (miRNA) interaction analysis indicated that the reported differentially expresse circRNAs may be associated with some regulatory functions through miRNAs in PE patients. Two ceRNAs networks were constructed according to the targeting relationship between circRNAs/miRNAs and miRNAs/mRNAs. One sub-network contained one upregulated circRNA, four downregulated miRNAs and five upregulated mRNAs, and another sub-network contained 10 downregulated circRNAs, 21 upregulated miRNAs and 15 downregulated mRNAs.

Conclusion

CircRNA expression patterns have been investigated and this analysis revealed their potential regulatory mechanisms in PE patients. We constructed the ceRNAs (competing endogenous RNA) to reveal the potential molecular roles of dysregulated circRNAs in the PE patients using RNA sequencing data. circRNA_13301 was the only one upregulated circRNA in ceRNA being targeted by four miRNAs.

New views on endothelial dysfunction in gestational hypertension and potential therapy targets

The placenta has vital roles in metabolite exchange, fetal growth, and pre-eclampsia (PE). In this review, we discuss the pathogenesis of hypertension in pregnancy, focusing on four major theories to explain PE, discussing endothelial roles in those theories. We focus in particular on the roles of nitric oxide (NO) and prostacyclin (PGI₂) in placental endothelium, and propose new hypotheses for the influence and mechanisms of endothelial NO and PGI₂ signaling pathways in PE.

Decreased circUBAP2 Expression Is Associated with Preeclampsia by Limiting Trophoblast Cell Proliferation and Migration

Preeclampsia (PE) is a common obstetric disease and a major cause of maternal, newborn, and fetal death. This condition is a multisystem disorder characterized by hypertension, proteinuria, and involvement of the kidney, liver, and nervous system. It is generally believed that the placenta is the main cause of PE. circRNAs are a special class of noncoding RNAs that can form covalently closed continuous ring structures with tissue-specific conservation, and they have been reported to play a wide range of regulatory functions in various diseases, including PE. In this study, we reported a novel circUBAP2 (hsa_circ_0003496) and found that it was downregulated in placental tissues from patients with PE compared to healthy controls. After knocking down circUBAP2 in trophoblast cells, we found that cell proliferation and migration were significantly suppressed. In addition, preliminary mechanistic studies showed that circUBAP2 can sponge miR-1244, and FOXM1 was identified as a target gene for miR-1244. Cotransfection of si-circUBAP2 and a miR-1244 inhibitor partially reversed the suppressive effect induced by circUBAP2 depletion on proliferation and migration. In conclusion, the circUBAP2/miR-1244/FOXM1 axis might be a promising molecular marker for the diagnosis and treatment of PE.

Circ_0001438 participates in the pathogenesis of preeclampsia via the circ_0001438/miR-942/NLRP3 regulatory network

INTRODUCTION

Preeclampsia (PE) is a common pregnancy disorder with multisystem complications. The growing data suggest that circular RNAs (circRNAs) involve in the development of PE. This study proposed to investigate the function and potential mechanisms of circ_0001438 in PE.

METHODS

The expression of circ_0001438, miR-942 and NOD-like receptor pyrin domain-containing protein 3 (NLRP3) was measured by quantitative real-time polymerase chain reaction (qRT-PCR). The expression at the protein level of NLRP3, interleukin 1 beta (IL-1β), interleukin 10 (IL-10), B-cell lymphoma 2 (Bcl-2), Cleaved-caspase-3 (Cleaved-casp-3), N-cadherin and E-cadherin was detected by Western blot. Cell proliferation was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and colony formation assay. Cell apoptosis was determined by flow cytometry assay. Cell migration and invasion were monitored by transwell assay. The target genes were obtained and verified by the online bioinformatics tool and dual-luciferase reporter assay.

RESULTS

The expression of circ_0001438 and NLRP3 was enhanced in PE placenta tissues. Circ_0001438 knockdown promoted cell proliferation, migration and invasion but inhibited apoptosis and inflammatory responses in HTR-8/Svneo cells, and these effects were reversed by the inhibition of miR-942, a target of circ_0001438. Moreover, NLRP3 was bounded by miR-942. The enrichment of miR-942 accelerated cell proliferation, migration and invasion but depleted apoptosis and inflammatory responses, while these impacts were partly abolished by NLRP3 overexpression.

DISCUSSION

Circ_0001438 sponged miR-942 to regulate the expression of NLRP3, and circ_0001438 aggravated the dysfunctions of human villous trophoblasts by mediating the miR-942/NLRP3 axis at least in part.

circCRAMP1L is a novel biomarker of preeclampsia risk and may play a role in preeclampsia pathogenesis via regulation of the MSP/RON axis in trophoblasts

Background

Preeclampsia is a severe disease in pregnant women, which is primarily managed by early screening and prevention. Circular RNAs (circRNAs) have increasingly been shown to be important biological regulators involved in numerous diseases. Further, increasing evidence has demonstrated that circRNAs can be used as diagnostic biomarkers. This study was conducted to evaluate the potential of circCRAMP1L, previously identified to be downregulated in preeclampsia, as a novel biomarker for predicting the development of preeclampsia.

Methods

We measured the expression of circCRAMP1L, which is reportedly relevant to trophoblast physiology, in plasma samples from 64 patients with preeclampsia and 64 age-, gestational age-, and body mass index-matched healthy pregnant women by qRT-PCR. MTT proliferation and transwell invasion assays revealed the biological role of circCRAMP1L in preeclampsia pathogenesis. RNA immunoprecipitation and dual-luciferase reporter assays clarified the mechanism underlying the biological function of circCRAMP1L in TEV-1 cells.

Results

circCRAMP1L circulating levels were significantly lower in patients with preeclampsia (2.66 ± 0.82, △Ct value) than in healthy pregnant women (3.95 ± 0.67, △Ct value, p <  0.001). The area under the receiver operating characteristic curve for circCRAMP1L was 0.813. Univariate and multivariate analyses identified circCRAMP1L as an independent predictor of preeclampsia. Furthermore, when circCRAMP1L was utilised in combination with its target protein macrophage stimulating protein (MSP), the predictive performance increased, with an area under the receiver operating characteristic curve of 0.928 (95% CI 0.882–0.974), 80.0% sensitivity, and 80.0% specificity. The in vitro results indicated that circCRAMP1L regulates cell proliferation, and invasion via MSP and RON proteins. We investigated the molecular mechanisms of these effects. In vitro, relative to the control group, circCRAMP1L overexpression significantly enhanced cell proliferation; furthermore, trophoblast cell invasion increased proportionally with circCRAMP1L expression. RNA immunoprecipitation and luciferase reporter gene illustrated that circCRAMP1L participated in regulation of trophoblast cell by regulating MSP.

Conclusion

Reduced plasma levels of circCRAMP1L may be associated with an increased risk of preeclampsia, and circCRAMP1L may be a novel biomarker of preeclampsia risk.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12884-020-03345-5.

Differentially expressed circular RNAs and the competing endogenous RNA network associated with preeclampsia

INTRODUCTION

Circular RNAs (circRNAs) are non-coding RNAs that are implicated in preeclampsia (PE) pathogenesis; however, their expression and functions in PE remain unclear. In this study, we aimed to investigate the expression of circRNAs in PE and construct a competing endogenous RNA (ceRNA) network, and analyze the associated pathways in PE pathogenesis.

METHODS

We performed circRNA sequencing to identify the differential expression profile of circRNAs in PE as compared to normal pregnancy. The circRNA candidates were validated using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Subsequently, we used datasets from the GEO database to generate the interaction network between circRNAs, microRNAs (miRNAs), and mRNAs. GO and KEGG enrichment analyses were performed to understand the functional significance of the differentially expressed circRNAs in PE.

RESULTS

We identified 361 differentially expressed circRNAs (252 upregulated and 109 downregulated) in preeclamptic placentas. Within the selected 31 circRNAs, 6 of them were verified by qRT-PCR. GO and KEGG analyses revealed the potential pathways affected by these circRNAs, e.g., T cell receptor signaling and MAP kinase pathways. A total of 134 miRNAs and 199 mRNAs were revealed to be differentially expressed in PE by analyzing datasets from the GEO database. The circRNA-miRNA-mRNA network comprised 206 circRNAs, 50 miRNAs, and 38 mRNAs. KEGG analysis of the 38 mRNAs included pathways involved in AMPK and PI3K-Akt signaling.

DISCUSSION

Our results reported the differential expression profile of circRNAs and the circRNA-miRNA-mRNA network in PE, which provides potential therapeutic targets for this disease.

Circ_0063517 acts as ceRNA, targeting the miR-31-5p-ETBR axis to regulate angiogenesis of vascular endothelial cells in preeclampsia

AIMS

Accumulated evidence indicates that the dysregulation of circular RNAs (circRNAs) plays pivotal roles in many human diseases including preeclampsia (PE). Circ_0063517 has been verified to be down-regulated in PE. But the role of circ_0063517 in PE is still unclear. This research aims to probe into the effect of circ_0063517 on angiogenesis in PE development.

MAIN METHODS

The expression of circ_0063517, endothelin receptor type B (ETBR) and miR-31-5p was assessed by quantitative reverse transcription polymerase chain reaction (RT-qPCR). MTT assay, colony formation assay, scratch assay, transwell assay, and tube formation assay were performed to detect proliferation, migration, and angiogenesis, respectively. Dual luciferase reporter system and RNA immunoprecipitation (RIP) assay were carried out to determine the interaction between miR-31-5p and circ_0063517(or ETBR). ETBR, VEGFRA, and VEGFR2 levels were detected by western blot analysis. The effect of circ_0063517 and ETBR on angiogenesis was evaluated in N-nitro-L-arginine methyl ester hydrochloride (L-NAME)-induced PE in vivo.

KEY FINDINGS

The levels of circ_0063517 and ETBR were down-regulated in the placenta tissue of PE patients. Conversely, the level of miR-31-5p was up-regulated in PE. Overexpression of circ_0063517 or knockdown of miR-31-5p facilitated growth, migration, and angiogenesis of vascular endothelial cells. Circ_0063517 knockdown-induced repression of the expression of ETBR, VEGFA, and VEGFR2 was partly counteracted by ETBR overexpression. Mechanistically, circ_0063517 sponged miR-31-5p to regulate ETBR expression. Finally, circ_0063517 promoted angiogenesis via enhancing ETBR expression in PE in vivo.

SIGNIFICANCE

Our findings suggest that circ_0063517-miR-31-5p-ETBR axis regulates angiogenesis during the pathological process of PE.

A Narrative Review of Placental Contribution to Adverse Pregnancy Outcomes in Women With Polycystic Ovary Syndrome

CONTEXT

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy of reproductive-aged women. In pregnancy, women with PCOS experience increased risk of miscarriage, gestational diabetes, preeclampsia, and extremes of fetal birth weight, and their offspring are predisposed to reproductive and cardiometabolic dysfunction in adulthood. Pregnancy complications, adverse fetal outcomes, and developmental programming of long-term health risks are known to have placental origins. These findings highlight the plausibility of placental compromise in pregnancies of women with PCOS.

EVIDENCE SYNTHESIS

A comprehensive PubMed search was performed using terms "polycystic ovary syndrome," "placenta," "developmental programming," "hyperandrogenism," "androgen excess," "insulin resistance," "hyperinsulinemia," "pregnancy," and "pregnancy complications" in both human and animal experimental models.

CONCLUSIONS

There is limited human placental research specific to pregnancy of women with PCOS. Gestational androgen excess and insulin resistance are two clinical hallmarks of PCOS that may contribute to placental dysfunction and underlie the higher rates of maternal-fetal complications observed in pregnancies of women with PCOS. Additional research is needed to prevent adverse maternal and developmental outcomes in women with PCOS and their offspring.

Down-regulated circPAPPA suppresses the proliferation and invasion of trophoblast cells via the miR-384/STAT3 pathway

Preeclampsia (PE) is the main cause of maternal death in primipara, and commonly results in severe maternal and neonatal complications such as multiple organ dysfunction syndrome. However, the exact pathogenesis of this disease remains unclear. Circular RNAs (circRNAs) are noncoding RNAs that have been shown to be extensively involved in numerous physiological processes, but there is limited knowledge of their functions and mechanisms in PE. In the present study, we found the expression of a circRNA, hsa_circ_0088227 (circRNA of pregnancy-associated plasma protein A, circPAPPA), was down-regulated in both placenta and plasma samples from subjects with PE. Knockdown of circPAPPA led to decreased proliferation and invasion in HTR8-S/Vneo trophoblast cells. miR-384 was identified as a direct target of circPAPPA, and the gene encoding signal transducer and activator of transcription 3 (STAT3) was targeted by miR-384. We found that miR-384 was unregulated in PE, and overexpression of miR-384 could inhibit cell proliferation and invasion. In addition, we showed that the expression of STAT3 was decreased with knockdown of circPAPPA or the overexpression of miR-384 in trophoblast cells, but this decrease was partially reversed when co-transfection was performed with mimics of miR-384 inhibitor and si-circPAPPA. Together, these results suggest that down-regulation of circPAPPA facilitates the onset and development of PE by suppressing trophoblast cells, with involvement of the miR-384/STAT3 signaling pathway. Our study significantly increases the understanding of the occurrence and development of PE, and also provides a molecular target for the treatment of this disorder.

Could circRNA be a new biomarker for pre-eclampsia?

Pre-eclampsia is a devastating complication of pregnancy which is characterized by hypertension and proteinuria in pregnant women. Pre-eclampsia is important as it is the leading cause of death. Moreover, untreated pre-eclampsia might lead to other lethal complications, for both fetus and mother. Pre-eclampsia can also affect the quality of life in affected women. Despite a large number of risk factors for pre-eclampsia, these risk factors are able to detect just 30% of women who are susceptible to pre-eclampsia. Heterogeneous manifestations of pre-eclampsia necessitate the discovery of potential biomarkers required for its early detection. Circular RNAs (circRNAs) are a type of RNA which are more abundant, specific, and highly organized compared with other types of RNA. Accordingly, circRNAs have been suggested as one of the potential biomarkers for different diseases. Recently, researchers have shown interest in the effects of circRNAs in pre-eclampsia, although the current evidence is limited. The majority of obstetricians are probably not aware of circRNAs as a useful biomarker. Here, we aimed to summarize recent supporting evidence and assess the mechanisms by which circRNAs are involved in pre-eclampsia.

Circular RNAs in hypertension: challenges and clinical promise

Hypertension (HT), or high blood pressure (BP), is a chronic disease that is common among populations worldwide. The occurrence of HT is one of the leading causes of cardiovascular morbidity and mortality in adults. Although multiple studies have stressed the multifactorial and multigenic nature of HT, uncertainties about its etiology persist, and current diagnostic biomarkers can explain only a small part of the phenotypic variance of BP. Hence, the search for novel biomarkers that enable early disease prevention and guided therapy is warranted. Regulatory circRNAs have emerged as the newest player in HT-related gene networks and hold promise for improving the accuracy of diagnosis. These RNAs are genome products that are formed through back-splicing of specific regions of pre-mRNAs. Evidence suggests that these RNA species are involved in various metabolic diseases. Recent studies have revealed that aberrant expression of circRNAs is relevant to the occurrence and development of HT. Accordingly, circRNAs are proposed as a new generation of predictive biomarkers and potential therapeutic targets for different forms of HT, including pulmonary hypertension and preeclampsia. This paper presents an overview of the findings from current research focusing on the emerging role of circRNAs in the pathogenesis of hypertension. Furthermore, some of the challenges encountered by circRNA studies are highlighted, and perspectives are provided on the future of research in this area.

Role of Circular RNAs in Preeclampsia

Circular RNAs (circRNAs) are noncoding RNAs characterized by circular covalently closed structures, which are generated by back-splicing. circRNA is more stable and conserved than linear RNA and exists in various organisms. Preeclampsia (PE), a common hypertensive disorder of pregnancy, has a profound impact on maternal and neonatal mortality and morbidity. Recent studies demonstrated that circRNAs were differentially expressed in PE maternal-fetal interface compared with those in the control and might mediate pathological processes in pregnancy complications. However, the mechanisms of action of circRNAs in PE are still unclear. Here, we provide a comprehensive review on the current state of knowledge on circRNAs associated with PE. We summarize the known expression profiles of circRNAs and discuss their potential application as biomarkers of PE. The possible mechanisms underlying circRNA dysregulation in the etiology of PE are also explored.