Long non-coding RNA MALAT1 regulates trophoblast functions through VEGF/VEGFR1 signaling pathway

Long non-coding RNAs: a summary of their roles in placenta development and pathology†

Long non-coding RNAs are cellular transcripts that have ˃200 nucleotides in length and do not code for proteins. Due to their low expression levels, long non-coding RNAs were previously considered as mere transcriptional noise. However, current evidence indicates that they regulate a myriad of biological processes such as cell proliferation, invasion, and apoptosis. Hence, their expression patterns are crucial indicators of the physiological or pathological states of cells, tissues, and organs. The utilization of long non-coding RNAs as biomarkers and therapeutic targets for the clinical management of several diseases have been suggested. Gradually, long non-coding RNAs are gaining a substantial attention in the field of feto-maternal medicine. After embryo implantation, the interactions between the trophoblast cells from the embryo and the uterus of the mother facilitate placenta development and pregnancy progression. These processes are tightly regulated, and their impairments result in pregnancy pathologies such as miscarriage and preeclampsia. Accumulating evidence implicates long non-coding RNAs in these processes. Herein, we have summarized the roles of several long non-coding RNAs in human placenta development, have proposed some mechanisms by which they participate in physiological and pathological placentation, have revealed some knowledge deficits, and have recommended ideal experimental approaches that will facilitate the clarification of the mechanistic actions of each long non-coding RNA at the feto-maternal interface during healthy and pathological pregnancies.

Mechanistic actions of long non-coding RNA MALAT1 within the ovary and at the feto-maternal interface

Long non-coding RNAs (LncRNAs) are being unveiled as crucial regulators of several biological processes and pathways. Among the lncRNAs is metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), which is also known as nuclear enriched abundant transcript 2 (NEAT2). MALAT1 is highly conserved in mammals, and controls cellular processes such as proliferation, migration, invasion, angiogenesis, and apoptosis in both physiological and pathological conditions. Roles of MALAT1 in the female reproductive system are gradually getting explored. Within the ovarian micro-environment, the physiological expression of MALAT1 potentially modulates folliculogenesis while its upregulation promotes the metastasis of epithelial ovarian cancers. Interestingly, women with polycystic ovary syndrome have been shown to exhibit aberrant ovarian expression of MALAT1 and this is believed to contribute to the development of the disease. At the feto-maternal interface, MALAT1 potentially promotes trophoblast development. While its placental downregulation is linked to the pathogenesis of preeclampsia, its placental upregulation is associated with placenta increta and placenta percreta. Hence, abnormal expression of MALAT1 is a candidate molecular biomarker and therapeutic target for the treatment of these obstetric and gynecologic anomalies. To enhance a quick uncovering and detailed characterization of the mechanistic actions of MALAT1 in the female reproductive system, we have highlighted some knowledge deficits and have recommended ideal experimental models to be employed in prospective investigations.

Noninvasive preeclampsia prediction using plasma cell-free RNA signatures

BACKGROUND

Preeclampsia, especially preterm preeclampsia and early-onset preeclampsia, is a life-threating pregnancy disorder, and the heterogeneity and complexity of preeclampsia make it difficult to predict risk and to develop treatments. Plasma cell-free RNA carries unique information from human tissue and may be useful for noninvasive monitoring of maternal, placental, and fetal dynamics during pregnancy.

OBJECTIVE

This study aimed to investigate various RNA biotypes associated with preeclampsia in plasma and to develop classifiers to predict preterm preeclampsia and early-onset preeclampsia before diagnosis.

STUDY DESIGN

We performed a novel, cell-free RNA sequencing method termed polyadenylation ligation-mediated sequencing to investigate the cell-free RNA characteristics of 715 healthy pregnancies and 202 pregnancies affected by preeclampsia before symptom onset. We explored differences in the abundance of different RNA biotypes in plasma between healthy and preeclampsia samples and built preterm preeclampsia and early-onset preeclampsia prediction classifiers using machine learning methods. Furthermore, we validated the performance of the classifiers using the external and internal validation cohorts and assessed the area under the curve and positive predictive value.

RESULTS

We detected 77 genes, including messenger RNA (44%) and microRNA (26%), that were differentially expressed in healthy mothers and mothers with preterm preeclampsia before symptom onset, which could separate participants with preterm preeclampsia from healthy samples and that played critical functional roles in preeclampsia physiology. We developed 2 classifiers for predicting preterm preeclampsia and early-onset preeclampsia before diagnosis based on 13 cell-free RNA signatures and 2 clinical features (in vitro fertilization and mean arterial pressure), respectively. Notably, both classifiers showed enhanced performance when compared with the existing methods. The preterm preeclampsia prediction model achieved 81% area under the curve and 68% positive predictive value in an independent validation cohort (preterm, n=46; control, n=151); the early-onset preeclampsia prediction model had an area under the curve of 88% and a positive predictive value of 73% in an external validation cohort (early-onset preeclampsia, n=28; control, n=234). Furthermore, we demonstrated that downregulation of microRNAs may play vital roles in preeclampsia through the upregulation of preeclampsia-relevant target genes.

CONCLUSION

In this cohort study, a comprehensive transcriptomic landscape of different RNA biotypes in preeclampsia was presented and 2 advanced classifiers with substantial clinical importance for preterm preeclampsia and early-onset preeclampsia prediction before symptom onset were developed. We demonstrated that messenger RNA, microRNA, and long noncoding RNA can simultaneously serve as potential biomarkers of preeclampsia, holding the promise of prevention of preeclampsia in the future. Abnormal cell-free messenger RNA, microRNA, and long noncoding RNA molecular changes may help to elucidate the pathogenic determinants of preeclampsia and open new therapeutic windows to effectively reduce pregnancy complications and fetal morbidity.

The Role of ncRNAs in the Immune Dysregulation of Preeclampsia

The main complications causing practically 75% of all maternal deaths are severe bleeding, infections, and high blood pressure during pregnancy (preeclampsia (PE) and eclampsia). The usefulness of ncRNAs as clinical biomarkers has been explored in an extensive range of human diseases including pregnancy-related diseases such as PE. Immunological dysregulation show that the Th1/17:Th2/Treg ratio is "central and causal" to PE. However, there is evidence of the involvement of placenta-expressed miRNAs and lncRNAs in the immunological regulation of crucial processes of placenta development and function during pregnancy. Abnormal expression of these molecules is related to immune physiopathological processes that occur in PE. Therefore, this work aims to describe the importance of miRNAs and lncRNAs in immune dysregulation in PE. Interestingly, multiple ncRNAS are involved in the immune dysregulation of PE participating in type 1 immune response regulation, immune microenvironment regulation in placenta promoting inflammatory factors, trophoblast cell invasion in women with Early-Onset PE (EOPE), placental development, and angiogenesis, promotion of population of M1 and M2, proliferation, invasion, and migration of placental trophoblast cells, and promotion of invasion and autophagy through vias such as PI3K/AKT/mTOR, VEGF/VEGFR1, and TLR9/STAT3.

Trophoblast Cell Function in the Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a complex thrombo-inflammatory autoimmune disease characterized by the presence of antiphospholipid antibodies (aPL). Women with APS are at high risk of recurrent early pregnancy loss as well as late obstetrical complications-premature birth due to placental insufficiency or severe preeclampsia. Accumulating evidence implies that vascular thrombosis is not the only pathogenic mechanism in obstetric APS, and that the direct negative effect of aPL on the placental cells, trophoblast, plays a major role. In this review, we summarize the current findings regarding the potential mechanisms involved in aPL-induced trophoblast dysfunction. Introduction on the APS and aPL is followed by an overview of the effects of aPL on trophoblast-survival, cell function and aPL internalization. Finally, the implication of several non-coding RNAs in pathogenesis of obstetric APS is discussed, with special emphasis of their possible role in trophoblast dysfunction and the associated mechanisms.

Biogenesis and function of exosome lncRNAs and their role in female pathological pregnancy

Preeclampsia, gestational diabetes mellitus, and recurrent spontaneous abortion are common maternal pregnancy complications that seriously endanger women's lives and health, and their occurrence is increasing year after year with a rejuvenation trend. In contrast to biomarkers found freely in tissues or body fluids, exosomes exist in a relatively independent environment and provide a higher level of stability. As backbone molecules, guidance molecules, and signaling molecules in the nucleus, lncRNAs can regulate gene expression. In the cytoplasm, lncRNAs can influence gene expression levels by modifying mRNA stability, acting as competitive endogenous RNAs to bind miRNAs, and so on. Exosomal lncRNAs can exist indefinitely and are important in intercellular communication and signal transduction. Changes in maternal serum exosome lncRNA expression can accurately and timely reflect the progression and regression of pregnancy-related diseases. The purpose of this paper is to provide a reference for clinical research on the pathogenesis, diagnosis, and treatment methods of pregnancy-related diseases by reviewing the role of exosome lncRNAs in female pathological pregnancy and related molecular mechanisms.

LncRNA Tuna is activated in cadmium-induced placental insufficiency and drives the NRF2-mediated oxidative stress response

Cadmium (Cd) is a toxic heavy metal found throughout the environment and one of the top ten toxicants of major public health concern identified by the World Health Organization. In utero Cd exposure causes fetal growth restriction, malformation, and spontaneous abortion; however, the mechanisms by which Cd impacts these outcomes are poorly understood. Cd accumulates in the placenta, suggesting that these negative outcomes may be a consequence of disrupted placental function and placental insufficiency. To understand the impact of Cd on gene expression within the placenta, we developed a mouse model of Cd-induced fetal growth restriction through maternal consumption of CdCl2 and performed RNA-seq on control and CdCl2 exposed placentae. The top differentially expressed transcript was the Tcl1 Upstream Neuron-Associated (Tuna) long non-coding RNA, which was upregulated over 25-fold in CdCl2 exposed placentae. Tuna has been shown to be critical for neural stem cell differentiation. However, within the placenta, there is no evidence that Tuna is normally expressed or functional at any developmental stage. To determine the spatial expression of Cd-activated Tuna within the placenta, we used in situ hybridization as well as placental layer-specific RNA isolation and analysis. Both methods confirmed the absence of Tuna expression in control samples and determined that Cd-induced Tuna expression is specific to the junctional zone. Since many lncRNAs regulate gene expression, we hypothesized that Tuna forms part of the mechanism of Cd-induced transcriptomic changes. To test this, we over-expressed Tuna in cultured choriocarcinoma cells and compared gene expression profiles to those of control and CdCl2 exposed cells. We demonstrate significant overlap between genes activated by Tuna overexpression and genes activated by CdCl2 exposure, with enrichment in the NRF2-mediated oxidative stress response. Herein we analyze the NRF2 pathway and show that Tuna increases NRF2/NRF2 both at the transcript and protein levels. Tuna drives increased NRF2 target gene expression, a result that is abrogated with the use of an NRF2 inhibitor, confirming that Tuna activates oxidative stress response genes through this pathway. This work identifies the lncRNA Tuna as a potential novel player in Cd-induced placental insufficiency.

Pregnancy-Specific Glycoprotein 9 Enhances Store-Operated Calcium Entry and Nitric Oxide Release in Human Umbilical Vein Endothelial Cells

We explored changes in pregnancy-specific glycoprotein 9 (PSG9) levels in the serum of patients with preeclampsia and the effects and underlying mechanisms of PSG9 effects on calcium (Ca2+) homeostasis and nitric oxide (NO) release in human umbilical vein endothelial cells (HUVECs). Western blotting was used to detect protein expression levels, and an NO fluorescence probe was used to examine NO production. Intracellular Ca2+ concentrations were measured using a Ca2+-sensitive fluorescent dye under a fluorescence microscope. Compared with those in healthy pregnant women, serum PSG9 levels were significantly decreased in patients with preeclampsia. PSG9 (0.1 μg/mL) treatment of HUVECs significantly enhanced the expression levels of store-operated calcium entry (SOCE) channel proteins Orai1 and Orai2, but not Orai3, and of endothelial nitric oxide synthase (eNOS) and NO production. Pretreatment with an inhibitor of SOCE (BTP2) abolished PSG9-enhanced Orai1, Orai2, and eNOS expression levels and NO production in HUVECs. The mechanisms underlying SOCE that were PSG9 enhanced in HUVECs appear to involve the Ca2+/eNOS/NO signaling pathway. These findings suggest that serum PSG9 levels may be a potential biomarker for monitoring the occurrence or development of preeclampsia in pregnancy and that PSG9 may be a potential therapeutic target for the treatment of preeclampsia.

A novel risk score model based on four angiogenesis long non-coding RNAs for prognosis evaluation of pancreatic adenocarcinoma

BACKGROUND

Long non-coding RNAs (lncRNAs) have been reported to play significant roles in tumour angiogenesis which prominently facilitates pancreatic adenocarcinoma (PAAD) progression.

METHODS

The clinical PAAD data were obtained from TCGA database and clinical specimens of 122 PAAD patients. The Molecular Signatures Database v4.0 was used to identify angiogenesis-related long non-coding RNAs (ARLNRs). Survival-related ARLNRs (sARLNRs) were further validated by univariate and multivariate COX regression analyses. The expressions of CASC8, AC015660.1, Z97832.2 and PAN3-AS1 in PAAD cell lines and tissues were examined by qPCR. The correlations between sARLNRs (CASC8 and AC015660.1) and clinicopathological characteristics of the 122 PAAD patients were analyzed by the chi-square test and Fisher's exact probability method.

RESULTS

590 lncRNAs were identified as ARLNRs, of which four sARLNRs were further used to establish an angiogenesis-related risk score model (ARRS), by which patients in the low-risk group have better survival probabilities than those in the high-risk group. The expression levels of CASC8 and AC015660.1 were significantly higher in PAAD cell lines and tumor tissues especially in patients with advanced grades and T-stages, while Z97832.2 and PAN3-AS1 were inverse. In addition, the higher expression of CASC8 and AC015660.1 prominently associated with the larger tumour size, and the more advanced grade and T-stage. However, the relevance between the sARLNRs (CASC8 and AC015660.1) expression and lymph node metastasis status was not significant.

CONCLUSIONS

In the study, we illuminate the clinical significance, angiogenesis relevance and prognosis-predictive value of four sARLNRs for PAAD. The results build a bridge between sARLNRs and tumour vascularization, and also establish a reliable and accurate risk scoring model for PAAD antiangiogenic strategy.

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.

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.

(Dis)similarities between the Decidual and Tumor Microenvironment

Placenta-specific trophoblast and tumor cells exhibit many common characteristics. Trophoblast cells invade maternal tissues while being tolerated by the maternal immune system. Similarly, tumor cells can invade surrounding tissues and escape the immune system. Importantly, both trophoblast and tumor cells are supported by an abetting microenvironment, which influences invasion, angiogenesis, and immune tolerance/evasion, among others. However, in contrast to tumor cells, the metabolic, proliferative, migrative, and invasive states of trophoblast cells are under tight regulatory control. In this review, we provide an overview of similarities and dissimilarities in regulatory processes that drive trophoblast and tumor cell fate, particularly focusing on the role of the abetting microenvironments.

The Role of Long Non-Coding RNAs in Trophoblast Regulation in Preeclampsia and Intrauterine Growth Restriction

Preeclampsia (PE) and Intrauterine Growth Restriction (IUGR) are two pregnancy-specific placental disorders with high maternal, fetal, and neonatal morbidity and mortality rates worldwide. The identification biomarkers involved in the dysregulation of PE and IUGR are fundamental for developing new strategies for early detection and management of these pregnancy pathologies. Several studies have demonstrated the importance of long non-coding RNAs (lncRNAs) as essential regulators of many biological processes in cells and tissues, and the placenta is not an exception. In this review, we summarize the importance of lncRNAs in the regulation of trophoblasts during the development of PE and IUGR, and other placental disorders.