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

Circ_0008440 Inhibits Proliferation and Promotes Apoptosis of Trophoblast Cells through the miR-194-5p/PFKFB2 Axis

Preeclampsia (PE), an idiopathic hypertensive disorder that arises during pregnancy, poses a serious threat to the health of expectant mothers. Human chorionic trophoblast cells (HTR-8/SVneo) are associated with the development of PE. It has been reported that circ_0008440 expression is abnormally increased in the placental tissues of PE patients. However, the function of circ_0008440 within HTR-8/SVneo cells during PE has yet to be fully elucidated. The study used RT-qPCR and western blot assay to evaluate the expression levels of 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 2 (PFKFB2), circ_0008440, and miR-942-5p in PE patients. Cells viability was measured using cell counting kit-8 (CCK-8) assay. Cell cycle assay and 5-ethynyl-2'-deoxyuridine (EDU) assay were used to measure cell proliferation. Cell apoptosis was assessed using flow cytometry assay. Western blot assay was used to detect protein expression. Dual-luciferase reporter assay and RNA pull-down assay were used to assess the interactions among circ_0008440, miR-942-5p, and PFKFB2 in HTR-8/SVneo cells. The study showed that the expression levels of circ_0008440 and PFKFB2 were significantly increased, while the expression of miR-942-5p was significantly decreased in the placental tissues of PE patients. Silencing of circ_0008440 promoted proliferation and tube formation and inhibited apoptosis of HTR-8/SVneo cells. In terms of molecular mechanism, miR-942-5p inhibitor or overexpression of PFKFB2 could partially reverse the effects of circ_0008440 silencing on the biological characteristics of HTR-8/SVneo cells. Collectively, circ_0008440 could act as a sponge of miR-942-5p to regulate the expression of PFKFB2, which further inhibited viability and proliferation of HTR-8/SVneo cells and promoted cell apoptosis.

Non-coding RNAs: the architects of placental development and pregnancy success

Noncoding RNAs (ncRNAs) constitute a significant portion of the transcriptome that lacks evident protein-coding functions; however, they have been confirmed to be crucial in various biological processes, including placental development. Notwithstanding the existence of various ncRNAs, research on their role in placental development and pregnancy has been constrained. The predominant category of identified ncRNAs specific to placental tissue is microRNAs (miRNAs). Given their prevalence, the significantly larger cohort of other non-coding RNAs, such as circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs), is anticipated to exert a considerably greater influence than miRNAs. Syncytiotrophoblast, a fetal-derived cell, serves as a conduit between the fetus and mother by secreting extracellular vesicles that contain fetal proteins and RNA. Alterations in ncRNAs within placental tissue, especially in trophoblast cells and extracellular vesicles, may be linked to placental dysfunction that leads to pregnancy complications, serving either as a causative factor or a result. This review encapsulates the existing understanding of ncRNAs in placental development, pregnancy success, pregnancy-related complications, extracellular vesicle conveyance, and their capacity as innovative diagnostic instruments and therapeutic strategies.

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.

Unveiling the Network regulatory mechanism of ncRNAs on the Ferroptosis Pathway: Implications for Preeclampsia

Non-coding RNAs (ncRNAs) are transcripts originating from the genome that do not serve as templates for protein synthesis. They function as epigenetic and translational regulators in various pathophysiological mechanisms, including cell proliferation and apoptosis. The ferroptosis signaling pathway, a novel mode of cell death, participates in numerous pathophysiological processes. Its signaling transmission is both complex and precise, featuring interconnected and interdependent pathways. Recent studies suggest that ncRNAs can finely regulate key genes in the ferroptosis pathway, thus modulating cellular functions, reducing oxidative stress, and maintaining maternal-fetal interface homeostasis. Future strategies targeting the ncRNA/ferroptosis axis may provide new perspectives and potential intervention points for treating preeclampsia. This article clarifies how the ncRNA/ferroptosis axis impacts preeclampsia, revealing how ncRNAs interact with ferroptosis, and pinpointing new molecular targets for the treatment of preeclampsia, thereby providing theoretical support for clinical strategies.

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.

Excessive ER-phagy mediated by FAM134B contributes to trophoblast cell mitochondrial dysfunction in preeclampsia

Autophagy dysregulation and Ca 2+-induced mitochondrial dysfunction in trophoblast cells are proposed to contribute to preeclampsia (PE) development. FAM134B is identified as a receptor associated with endoplasmic reticulum autophagy (ER-phagy). In this study, the placentas of normal pregnant women and PE patients are collected and analyzed by immunohistochemistry, quantitative real-time PCR, and western blot analysis. The effects of ER-phagy are investigated in HTR8/SVneo cells. Significantly increased levels of FAM134B, inositol-1,4,5-triphosphate receptor type 1 (IP3R), calnexin, cleaved caspase 3 and cytochrome C are detected in the PE placenta and sodium nitroprusside (SNP)-treated HTR-8/SVneo cells. Overexpression of FAM134B in HTR-8/SVneo cells results in increased apoptosis, impaired invasion capacity, and diminished mitochondrial function, while an autophagy inhibitor improves mitochondrial performance. Excessive ER-phagy is also associated with an increased concentration of gamma linolenic acid. Our findings suggest that FAM134B contributes to trophoblast apoptosis by mediating ER-mitochondria Ca 2+ transfer through mitochondria-associated endoplasmic reticulum membranes (MAMs) and subsequent mitochondrial function, further enhancing our understanding of PE etiology.

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.

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.

CircCRIM1 mediates proliferation, migration, and invasion of trophoblast cell through regulating miR-942-5p/IL1RAP axis

BACKGROUND

Preeclampsia (PE) is a severe complication that occurs during pregnancy and a main cause of perinatal mortality of mothers as well as infants, which is characterized by abnormal placental trophoblast. Previous study reported that aberrant circular RNA (circRNA) was involved in the pathogenesis and progression of PE. Herein, we aimed to investigate the role of circCRIM1 and explore the mechanism of circCRIM1 in PE.

METHODS

The quantitative real-time PCR (qRT-PCR) was conducted to determine the relative expression of circCRIM1, miR-942-5p, and IL1RAP in tissues and cells. Cell proliferation viability was assessed by both MTT and EdU assays. Cell cycle distribution was analyzed using flow cytometry. Transwell assay was performed to test the cell migration and invasion. The protein levels of CyclinD1, MMP9, MMP2, and IL1RAP were measured by western blot. The putative binding sites between miR-942-5p and circCRIM1 or IL1RAP 3'UTR were verified by dual-luciferase reporter gene assay. Rescue experiment was performed to confirm that miR-942-5p/IL1RAP axis was functional target of circCRIM1 in trophoblast cells.

RESULTS

CircCRIM1 was upregulated in placenta tissues of PE and its expression was inversely related to infant weight. Overexpression of circCRIM1 suppressed proliferation, migration, and invasion and reduced the protein levels of CyclinD1, MMP9, MMP2 of trophoblast cells, whereas its knockdown exerted the opposite effect. CircCRIM1 could interact with miR-942-5p, and introduction of miR-942-5p partially abated the inhibitory effect of circCRIM1 on trophoblast cell behaviors. IL1RAP was directly targeted and negatively regulated by miR-942-5p. miR-942-5p played its regulatory role on cell proliferation, migration, and invasion of trophoblast by IL1RAP. Further analysis showed that circCRIM1 modulated IL1RAP expression via sponging miR-942-5p.

CONCLUSION

The results of the present study demonstrated that circCRIM1 inhibited the proliferation, migration, and invasion of trophoblast cells through sponging miR-942-5p and up-regulating IL1RAP, providing a possible new mechanism of PE.

Emerging role of miRNAs, lncRNAs, and circRNAs in pregnancy-associated diseases

ABSTRACT

Accumulating studies have demonstrated that non-coding RNAs (ncRNAs), functioning as important regulators of transcription and translation, are involved in the establishment and maintenance of pregnancy, especially the maternal immune adaptation process. The endometrial stromal cells (ESCs), trophoblast cells, and decidua immune cells that reside at the maternal-fetal interface are thought to play significant roles in normal pregnancy and pregnancy-associated diseases. Here, we reviewed the up-to-date evidence on how microRNA, long non-coding RNA, and circular RNA regulate ESCs, trophoblast cells, and immune cells and discussed the potential applications of these ncRNAs as diagnostic and therapeutic markers in pregnancy complications.

circ_0004904 regulates the trophoblast cell in preeclampsia via miR-19b-3p/ARRDC3 axis

Circular RNAs have been demonstrated to act as vital participants in various diseases, including preeclampsia (PE). This study aimed to research the effects of circ_0004904 on PE. The contents of circ_0004904, microRNA-19b-3p (miR-19b-3p) and arrestin domain containing 3 (ARRDC3) were quantified by quantitative real-time PCR and western blot. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and 5-ethynyl-2'-deoxyuridine assays were enforced to assess cell proliferation. The transwell assay and flow cytometry were applied to detect the cell migration, invasion, and apoptosis. The liaison between miR-19b-3p and circ_0004904 or ARRDC3 was demonstrated by dual-luciferase reporter assay. Thereafter, circ_0004904 and ARRDC3 were augmented, and miR-19b-3p was restrained in PE. Circ_0004904 silencing contributed to cell proliferation, migration, and invasion, but restrained cell apoptosis in trophoblast cells. Further, miR-19b-3p was a target of circ_0004904, and miR-19b-3p could target ARRDC3. Additionally, circ_0004904 accelerated PE evolution via changing ARRDC3 level by binding to miR-19b-3p. In all, circ_0004904 encouraged PE progress via miR-19b-3p/ARRDC3 axis.

CircRNA_06354 might promote early-onset preeclampsia in humans via hsa-miR-92a-3p/vascular endothelial growth factor-A

BACKGROUND

Early-onset preeclampsia (EOPE) is a serious pregnancy disorder with multisystem complications. Recently, circRNA was reported to participate in the progression of EOPE. However, the role and mechanism of circRNA_06354 in the pathophysiological development of EOPE remain unclear.

METHODS

Blood samples from patients with EOPE and healthy pregnant controls (CTRL) were analyzed by RNA-seq. functions and mechanisms of circRNA_06354 in EOPE were investigated by a series of experiments. An EOPE rat model was constructed to detect the expression levels of circRNA_06354.

RESULTS

The level of circRNA_06354 was altered in EOPE and CTRL individuals, as well as EOPE and CTRL rats. CircRNA_06354 had a sensitivity of 88.9% and a specificity of 100% in predicting EOPE. Subcellular localization indicated that circRNA_06354 was primarily detected in the cytoplasm of HTR8-/SV-neo cells and the cytotrophoblast of EOPE placentas. In addition, circRNA_06354 transcription was markedly higher than that of its linear counterpart. RNA pull-down assays implied that hsa-miR-92a-3p might sponge circRNA_06354. Vascular endothelial growth factor-A (VEGF-A) levels were found to be increased in EOPE patients. Moreover, overexpression of circRNA_06354 suppressed the migration, invasion and tube formation of trophoblastic cells invading spiral arteries or the endometrium.

CONCLUSION

CircRNA_06354 inhibits trophoblastic cell invasion, migration and tube formation toward the endometrium in the initiation of EOPE. The circRNA_06354/hsa-miR-92a-3p/VEGF-A axis might be a therapeutic target in the prevention and treatment of EOPE.

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.

Long noncoding RNA maternally expressed gene 3 improves trophoblast dysfunction and inflammation in preeclampsia through the Wnt/β-Catenin/nod-like receptor pyrin domain-containing 3 axis

Inadequate trophoblastic infiltration and resulting placental hypoxia and inflammation comprise the core pathological basis of preeclampsia (PE). Maternally expressed gene 3 (MEG3) is known to be involved in the pathogenesis of preeclampsia by inhibiting the migration and invasion of trophoblasts and promoting their apoptosis. Nevertheless, the specific underlying downstream molecular mechanism of MEG3 is less well characterized. In this study, we detected lower expression levels of MEG3 and β-Catenin and higher expression of nod-like receptor pyrin domain-containing 3 (NLRP3) in placental tissues of pregnant women with severe preeclampsia (sPE) than in normal pregnancies. Elevated serum levels of IL-1β and TNF-α were also observed in the sPE group. Then, we established a hypoxia/reoxygenation (H/R) model to mimic preeclampsia. Similar results with sPE group were found in the H/R group compared with the control group. In addition, suppressive trophoblast proliferation, migration and invasion and increases in the apoptotic rate and inflammation were also detected in the H/R group. Notably, overexpressing MEG3 markedly improved trophoblast dysfunction and inflammation caused by H/R. However, the effects of MEG3 on trophoblasts, whether upregulated or downregulated, can be reversed by DKK-1 (Wnt/β-Catenin inhibitor) and MCC950 (NLRP3 inhibitor). The current study revealed that MEG3 regulates trophoblast function and inflammation through the Wnt/β-Catenin/NLRP3 axis and provided new insights into the pathogenesis of preeclampsia.

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.

circRNA circ_0055724 Inhibits Trophoblastic Cell Line HTR-8/SVneo’s Invasive and Migratory Abilities via the miR-136/N-Cadherin Axis

Preeclampsia (PE) is one of the major causes of morbidity and mortality in pregnancy. According to recent research, circular RNAs (circRNA) may act as sponges for microRNAs (miRNAs) and modulate gene expression. Low expression of hsa_circ_0055724 (circ_0055724) in PE tissues was recently reported in literatures. However, its mechanism and function have not been reported. Therefore, we were committed to investigating the role and mechanism of circ_0055724 in PE. Our study first verified the low expression of circ_0055724 in PE tissues. Overexpression or knockdown of circ_0055724 enhances/weakens the trophoblast cell survival, migration, and invasion. Furthermore, CircInteractome predicted the binding sites of circ_0055724 and miR-136, while Starbase predicted miR-136 targeted N-cadherin. Luciferase reporter gene assay confirmed that circ_0055724 directly interacts with miR-136 and miR-136 directly interacts with N-cadherin. More results indicated that high expression of miR-136 and low expression of N-cadherin appeared in PE. Increased expression of circ_0055724 resulted in decreased miR-136 but increased N-cadherin expression. Hence, circ_0055724 and N-cadherin were positively correlated, while circ_0055724 and miR-136 had a negative correlation. In terms of mechanism, circ_0055724 may induce the expression of N-cadherin and regulate the proliferation, migration, and invasion of trophoblast cells through decreasing miR-136, which can be a promising biomarker for early diagnosis and prognosis of patients with PE.

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.

circ_0085296 inhibits the biological functions of trophoblast cells to promote the progression of preeclampsia via the miR-942-5p/THBS2 network

Insufficient invasion of trophoblast cells is one of the important causes of preeclampsia (PE). Circular RNA (circRNA) has been proven to regulate the biological functions of trophoblast cells and mediate the progression of PE. The expression of circ_0085296, microRNA (miR)-942-5p, and thrombospondin 2 (THBS2) was detected by quantitative real-time PCR. In addition, the interaction between miR-942-5p and circ_0085296 or THBS2 was confirmed by dual-luciferase reporter assay and RIP assay. Our data showed that circ_0085296 was upregulated in the placental tissues of PE patients. Silenced circ_0085296 could enhance the proliferation, migration, invasion, and angiogenesis of HTR-8/SVneo cells. Besides, circ_0085296 was found to act as miR-942-5p sponge. Function analysis results suggested that miR-942-5p inhibitor reversed the positive regulation of circ_0085296 knockdown on the biological functions of HTR-8/SVneo cells. Moreover, THBS2 was a target of miR-942-5p, and its overexpression also reversed the promotion effect of miR-942-5p on the proliferation, migration, invasion, and angiogenesis of HTR-8/SVneo cells. Also, circ_0085296 was discovered to positively regulate THBS2 by sponging miR-942-5p. To sum up, our results revealed that circ_0085296 could inhibit trophoblast cells proliferation, migration, invasion, and angiogenesis by regulating miR-942-5p/THBS2, confirming that circ_0085296 might be a potential therapeutic target for PE.

Non-coding RNA-based regulation of inflammation

Inflammation is a multifactorial process and various biological mechanisms and pathways participate in its development. The presence of inflammation is involved in pathogenesis of different diseases such as diabetes mellitus, cardiovascular diseases and even, cancer. Non-coding RNAs (ncRNAs) comprise large part of transcribed genome and their critical function in physiological and pathological conditions has been confirmed. The present review focuses on miRNAs, lncRNAs and circRNAs as ncRNAs and their potential functions in inflammation regulation and resolution. Pro-inflammatory and anti-inflammatory factors are regulated by miRNAs via binding to 3'-UTR or indirectly via affecting other pathways such as SIRT1 and NF-κB. LncRNAs display a similar function and they can also affect miRNAs via sponging in regulating levels of cytokines. CircRNAs mainly affect miRNAs and reduce their expression in regulating cytokine levels. Notably, exosomal ncRNAs have shown capacity in inflammation resolution. In addition to pre-clinical studies, clinical trials have examined role of ncRNAs in inflammation-mediated disease pathogenesis and cytokine regulation. The therapeutic targeting of ncRNAs using drugs and nucleic acids have been analyzed to reduce inflammation in disease therapy. Therefore, ncRNAs can serve as diagnostic, prognostic and therapeutic targets in inflammation-related diseases in pre-clinical and clinical backgrounds.

Circular RNA circ_0111277 Serves as ceRNA, Targeting the miR-424-5p/NFAT5 Axis to Regulate the Proliferation, Migration, and Invasion of Trophoblast Cells in Preeclampsia

Preeclampsia is the main reason for maternal and fetal deaths during the second half of pregnancy. Trophoblast cells play a pivotal role in preeclampsia progression. Circular RNA (circRNA) circ_0111277 has been reported to be related to the development of trophoblast cells. This study is designed to explore the role and mechanism of circ_0111277 on trophoblast cell behavior in preeclampsia. Circ_0111277, microRNA-424-5p (miR-424-5p), and nuclear factor of activated T-cell 5 (NFAT5) levels were measured by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, migration, invasion, and angiogenesis were measured by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay, transwell assay, tube formation assay, and wound healing assay. Protein levels of matrix metallopeptidase 2 (MMP2), vascular endothelial growth factor-A (VEGF-A), NFAT5, phospho-phosphatidylinositol 3 kinase (p-PI3K), PI3K, phospho-protein kinase B (p-AKT), and AKT were examined by western blot assay. The binding relationship between miR-424-5p and circ_0111277 or NFAT5 was predicted by circBank or starBase and then verified by a dual-luciferase reporter assay. Circ_0111277 and NFAT5 expression were increased in placenta tissues of preeclampsia patients, and miR-424-5p was decreased. Moreover, circ_0111277 knockdown could boost cell viability, migration, invasion, and angiogenesis in trophoblast cells. The mechanical analysis discovered that circ_0111277 acted as a sponge of miR-424-5p to regulate NFAT5 expression. Besides, circ_0111277 silencing promoted the PI3K/AKT signaling pathway in trophoblast cells. Circ_0111277 downregulation could facilitate cell growth and metastasis in trophoblast cells partly by regulating the miR-424-5p/NFAT5 axis, providing an underlying circRNA-targeted therapy for preeclampsia.

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.