Comparison of activin A and cell-free fetal DNA levels in maternal plasma from patients at high risk for preeclampsia

Activin A and pathologies of pregnancy: a review

Activin A is a two-subunit protein belonging to the transforming growth factor β superfamily. First discovered almost three decades ago, it has since been implicated in diverse physiological roles, ranging from wound repair to reproduction. After 30 years of research, altered activin A levels are now understood to be associated with the development of various diseases, making activin A a potential therapeutic target. In pregnancy, the placenta and fetal membranes are major producers of activin A, with significantly enhanced serum concentrations now recognised as a contributor to numerous gestational disorders. Evidence now suggests that circulating levels of activin A may be clinically relevant in the early detection of pregnancy complications, including miscarriage and preeclampsia. This review aims to summarise our current understanding of activin A as a potential diagnostic marker in common pregnancy pathologies.

Activin A promotes human trophoblast invasion by upregulating integrin β3 via ALK4-SMAD4 signaling

INTRODUCTION

Activin A has been widely regarded as an important promoter of trophoblast invasion during the first trimester of pregnancy. However, whether integrin β3 is involved in activin A-upregulated trophoblast invasion and the underlying molecular mechanisms remain largely unknown.

METHODS

We utilized immortalized (HTR8/SVneo) and primary human extravillous trophoblast (EVT) cells, as well as first-trimester chorionic villous explants as study models to investigate the function and underlying molecular mechanisms of integrin β3 in activin A-promoted human trophoblast invasion.

RESULTS

We found that activin A increased integrin β3 mRNA and protein levels in both HTR8/SVneo and primary EVT cells, and knockdown of integrin β3 significantly decreased basal and activin A-upregulated trophoblast invasion. Moreover, SB431542 (a specific inhibitor of TGF-β type Ι receptor kinase) abolished activin A-upregulated integrin β3 expression and SMAD2/3 phosphorylation. In addition, siRNA-mediated knockdown of ALK4 or SMAD4 both abolished activin A-upregulated integrin β3 expression in HTR8/SVneo cells, while knockdown of ALK4 or SMAD4 attenuated activin A-upregulated integrin β3 expression in primary EVTs.

DISCUSSION

Our findings reveal the mediation role of integrin β3 in activin A-upregulated human trophoblast invasion and that activin An upregulates integrin β3 expression in an ALK4-SMAD4 signaling-dependent manner.

Sustained Elevated Circulating Activin A Impairs Global Longitudinal Strain in Pregnant Rats: A Potential Mechanism for Preeclampsia-Related Cardiac Dysfunction

Mediators of cardiac injury in preeclampsia are not well understood. Preeclamptic women have decreased cardiac global longitudinal strain (GLS), a sensitive measure of systolic function that indicates fibrosis and tissue injury. GLS is worse in preeclampsia compared to gestational hypertension, despite comparable blood pressure, suggesting that placental factors may be involved. We previously showed that Activin A, a pro-fibrotic factor produced in excess by the placenta in preeclampsia, predicts impaired GLS postpartum. Here, we hypothesized that chronic excess levels of Activin A during pregnancy induces cardiac dysfunction. Rats were assigned to sham or activin A infusion (1.25–6 µg/day) on a gestational day (GD) 14 (n = 6–10/group). All animals underwent blood pressure measurement and comprehensive echocardiography followed by euthanasia and the collection of tissue samples on GD 19. Increased circulating activin A (sham: 0.59 ± 0.05 ng/mL, 6 µg/day: 2.8 ± 0.41 ng/mL, p < 0.01) was associated with impaired GLS (Sham: −22.1 ± 0.8%, 6 µg/day: −14.7 ± 1.14%, p < 0.01). Activin A infusion (6 µg/day) increased beta-myosin heavy chain expression in heart tissue, indicating cardiac injury. In summary, our findings indicate that increasing levels of activin A during pregnancy induces cardiac dysfunction and supports the concept that activin A may serve as a possible mediator of PE-induced cardiac dysfunction.

Circulating Activin A is elevated at 36 weeks' gestation preceding a diagnosis of preeclampsia

Activin A is aberrantly expressed by the preeclamptic placenta and circulating levels have been investigated as a potential biomarker for the disease. In a nested case-control study we measured Activin A levels in maternal plasma at 28- and 36-weeks' gestation preceding term preeclampsia diagnosis. At 28 weeks Activin A was not significantly altered (n = 73 destined to develop preeclampsia vs n = 191 controls). At 36 weeks' gestation Activin A was significantly increased in 40 women destined to develop preeclampsia relative to 201 controls (p < 0.0001). These findings provide further validation of Activin A as a potential biomarker for subsequent term preeclampsia.

Serum and urine levels of activin A in primigravidae and multigravidae: a prospective cross-sectional study

The aim of the present study was to investigate serum and urine levels of activin A in different moments of gestation, in primigravidae and in multigravidae, to understand whether these variables (biological sample and first gestation) affect activin A as a biomarker in pregnancy. We prospectively included 43 pairs of serum and urine samples from 25 women examined at different gestational ages (range 45 to 268 days). In the group of primigravidae (n = 16 samples from 9 participants), there was no significant change in serum activin A levels across gestation. Conversely, the group of multigravidae (n = 27 samples from 16 women) had higher serum activin A levels in the third trimester (2676 ± 840 pg/ml) compared to the first (583 ± 408 pg/ml) and second (1040 ± 384) trimesters (p = .025). Urine activin A concentrations did not differ between the two groups and did not change according to the gestation phase. There was no correlation between serum and urinary levels of activin A (r = 0.149, p = .359). These data suggest that activin A secretion may vary less during the first pregnancy, while urine activin A is unlikely to be a surrogate for the systemic levels of this hormone in pregnant women.

Integrated analysis of multiple microarray studies to identify novel gene signatures in preeclampsia

INTRODUCTION

Preeclampsia (PE) is one of the major causes of maternal and fetal morbidity and mortality in pregnancy worldwide. However, the intrinsic molecular mechanisms underlying the pathogenesis of PE have not yet been fully elucidated.

METHODS

Robust rank aggregation (RRA), weighted correlation network analysis (WGCNA) and protein-protein interaction (PPI) methods were used to identify robust differentially expressed genes (DEGs) and hub genes in preeclampsia and subgroups based on 10 Gene Expression Omnibus (GEO) datasets. Subsequently, enrichment analysis and correlation analysis were performed to explore the potential function of the robust DEGs and hub genes. The diagnostic role of hub genes was further investigated by GSE12767. The miRNA regulators and the effect of hypoxia on hub genes were explored by using GSE84260 and GSE65271, respectively.

RESULTS

Robust DEGs were identified in each subgroup including preeclampsia. Totally, 24 hub genes enriched in inflammatory response, renin-angiotensin system and JAK-STAT pathway, and 24 related miRNA regulators were identified.

DISCUSSION

Our integrated analysis identified novel gene signatures in preeclampsia and subgroups and will contribute to the understanding of comprehensive molecular changes in preeclampsia.

The transforming growth factor β superfamily as possible biomarkers of preeclampsia: a comprehensive review

The etiology of preeclampsia - an abnormal placentation-mediated disease - is not fully understood; and there are very few biomarkers with which to predict and diagnose it. Early prediction and diagnosis of this pathology can lead to a significant improvement in maternal and perinatal outcomes. Since members of the transforming growth factor β superfamily influence placentation, and are released from the placenta into the maternal circulatory system, several studies have investigated the involvement of these cytokines in preeclampsia and the possibility of using their serum levels as biomarkers of the disease. In this review, we have summarized the reported relationships between the levels of this superfamily of cytokines and preeclampsia. The available information indicates that altered levels of some of these cytokines are involved in the pathogenesis and pathophysiology of preeclampsia, suggesting their likelihood of serving as predictive and diagnostic biomarkers of the disease.

Activin A in Mammalian Physiology

Activins are dimeric glycoproteins belonging to the transforming growth factor beta superfamily and resulting from the assembly of two beta subunits, which may also be combined with alpha subunits to form inhibins. Activins were discovered in 1986 following the isolation of inhibins from porcine follicular fluid, and were characterized as ovarian hormones that stimulate follicle stimulating hormone (FSH) release by the pituitary gland. In particular, activin A was shown to be the isoform of greater physiological importance in humans. The current understanding of activin A surpasses the reproductive system and allows its classification as a hormone, a growth factor, and a cytokine. In more than 30 yr of intense research, activin A was localized in female and male reproductive organs but also in other organs and systems as diverse as the brain, liver, lung, bone, and gut. Moreover, its roles include embryonic differentiation, trophoblast invasion of the uterine wall in early pregnancy, and fetal/neonate brain protection in hypoxic conditions. It is now recognized that activin A overexpression may be either cytostatic or mitogenic, depending on the cell type, with important implications for tumor biology. Activin A also regulates bone formation and regeneration, enhances joint inflammation in rheumatoid arthritis, and triggers pathogenic mechanisms in the respiratory system. In this 30-yr review, we analyze the evidence for physiological roles of activin A and the potential use of activin agonists and antagonists as therapeutic agents.

Activins in reproductive biology and beyond

BACKGROUND

Activins are members of the pleiotrophic family of the transforming growth factor-beta (TGF-β) superfamily of cytokines, initially isolated for their capacity to induce the release of FSH from pituitary extracts. Subsequent research has demonstrated that activins are involved in multiple biological functions including the control of inflammation, fibrosis, developmental biology and tumourigenesis. This review summarizes the current knowledge on the roles of activin in reproductive and developmental biology. It also discusses interesting advances in the field of modulating the bioactivity of activins as a therapeutic target, which would undoubtedly be beneficial for patients with reproductive pathology.

METHODS

A comprehensive literature search was carried out using PUBMED and Google Scholar databases to identify studies in the English language which have contributed to the advancement of the field of activin biology, since its initial isolation in 1987 until July 2015. 'Activin', 'testis', 'ovary', 'embryonic development' and 'therapeutic targets' were used as the keywords in combination with other search phrases relevant to the topic of activin biology.

RESULTS

Activins, which are dimers of inhibin β subunits, act via a classical TGF-β signalling pathway. The bioactivity of activin is regulated by two endogenous inhibitors, inhibin and follistatin. Activin is a major regulator of testicular and ovarian development. In the ovary, activin A promotes oocyte maturation and regulates granulosa cell steroidogenesis. It is also essential in endometrial repair following menstruation, decidualization and maintaining pregnancy. Dysregulation of the activin-follistatin-inhibin system leads to disorders of female reproduction and pregnancy, including polycystic ovary syndrome, ectopic pregnancy, miscarriage, fetal growth restriction, gestational diabetes, pre-eclampsia and pre-term birth. Moreover, a rise in serum activin A, accompanied by elevated FSH, is characteristic of female reproductive aging. In the male, activin A is an autocrine and paracrine modulator of germ cell development and Sertoli cell proliferation. Disruption of normal activin signalling is characteristic of many tumours affecting reproductive organs, including endometrial carcinoma, cervical cancer, testicular and ovarian cancer as well as prostate cancer. While activin A and B aid the progression of many tumours of the reproductive organs, activin C acts as a tumour suppressor. Activins are important in embryonic induction, morphogenesis of branched glandular organs, development of limbs and nervous system, craniofacial and dental development and morphogenesis of the Wolffian duct.

CONCLUSIONS

The field of activin biology has advanced considerably since its initial discovery as an FSH stimulating agent. Now, activin is well known as a growth factor and cytokine that regulates many aspects of reproductive biology, developmental biology and also inflammation and immunological mechanisms. Current research provides evidence for novel roles of activins in maintaining the structure and function of reproductive and other organ systems. The fact that activin A is elevated both locally as well as systemically in major disorders of the reproductive system makes it an important biomarker. Given the established role of activin A as a pro-inflammatory and pro-fibrotic agent, studies of its involvement in disorders of reproduction resulting from these processes should be examined. Follistatin, as a key regulator of the biological actions of activin, should be evaluated as a therapeutic agent in conditions where activin A overexpression is established as a contributing factor.

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

Correlation between cell-free mRNA expressions and PLGF protein level in severe preeclampsia

BACKGROUND

Preeclampsia is a major cause of morbidity and mortality, both maternal and perinatal. The etiology and pathophysiology of preeclampsia remain unknown. Research shows the implantation of the placenta in preeclampsia occurs due to incomplete angiogenic imbalance as one of the preeclampsia pathogenesis. PlGF is angiogenic protein which is synthesized in placenta by mRNA PlGF. When damage occurs, mRNA will be released from cell and form cell-free mRNA. This study aims to analyze the differences between the PlGF mRNA expression in severe preeclampsia and normal pregnancy as well as to measure the relationship between cell-free mRNA and levels of PlGF with the incidence of severe preeclampsia.

METHODS

The method used in this study is an observational analytic study with cross-sectional design. Blood samples were obtained from patients with preeclampsia and normal pregnancies as the controlling factors in accordance with inclusion and exclusion criterias. Examination of the PlGF level was measured by ELISA method and mRNA PIGF expression was measured by RT-PCR. Physical and laboratory examinations of patients were recorded and collected as data. Calculations were done by statistical analysis.

RESULTS

Mean of the cell-free mRNA PlGF expression level in severe preeclampsia is 2.2983 ng/mL within the scale of 1.96-2.83 ng/mL and deviation standard of 0.1897. Using Pearson Analysis Test, the result shows that there is a positive correlation between cell-free mRNA expression and PlGF protein level in severe preeclampsia, with r = 0.640 dan p < 0.004.

CONCLUSION

There is no difference between expression of cell-free mRNA PlGF in severe preeclampsia serum and normal pregnancy. There is a significant correlation between expression of cell-free mRNA and PlGF protein level in severe preeclampsia.

Can the quantity of cell-free fetal DNA predict preeclampsia: a systematic review

OBJECTIVE

Previous studies have demonstrated an increase in the quantity of cell-free fetal DNA (cffDNA) before the onset of preeclampsia. It would be beneficial if the quantity of cffDNA predicted preeclampsia in order to implement preventative trials and strategies to decrease maternal and fetal morbidity. Our objective was to review the literature on using cffDNA levels as a predictor of preeclampsia.

METHODS

We performed a systematic review following the Meta-analyses and Systematic Review of Observational Studies guidelines. Included studies evaluated cffDNA levels in pregnant women before the clinical onset of preeclampsia.

RESULTS

Thirteen studies met inclusion criteria. There was considerable heterogeneity between included studies, and all received a quality grade of C on the Grading of Recommendations Assessment, Development, and Evaluation scale. Of the 13 studies, 11 found an increase in cffDNA among pregnant women who subsequently developed preeclampsia. In addition, all four studies analyzing early-onset or severe preeclampsia found significantly elevated cffDNA levels prior to disease onset.

CONCLUSION

Cell-free fetal DNA quantification is a promising marker for preeclampsia prediction, especially for the development of early-onset or severe preeclampsia. However, because of the heterogeneity in published studies, a precise conclusion about the statistical and clinical relevance cannot be made.

Endocannabinoids as biomarkers of human reproduction

BACKGROUND

Infertility is a condition of the reproductive system that affects ∼10-15% of couples attempting to conceive a baby. More than half of all cases of infertility are a result of female conditions, while the remaining cases can be attributed to male factors, or to a combination of both. The search for suitable biomarkers of pregnancy outcome is a challenging issue in human reproduction, aimed at identifying molecules with predictive significance of the reproductive potential of male and female gametes. Among the various candidates, endocannabinoids (eCBs), and in particular anandamide (AEA), represent potential biomarkers of human fertility disturbances. Any perturbation of the balance between synthesis and degradation of eCBs will result in local changes of their tone in human female and male reproductive tracts, which in turn regulates various pathophysiological processes, oocyte and sperm maturation included.

METHODS

PubMed and Web of Science databases were searched for papers using relevant keywords like 'biomarker', 'endocannabinoid', 'infertility', 'pregnancy' and 'reproduction'.

RESULTS

In this review, we discuss different studies on the measurements of AEA and related eCBs in human reproductive cells, tissues and fluids, where the local contribution of these bioactive lipids could be critical in ensuring normal sperm fertilizing ability and pregnancy.

CONCLUSION

Based on the available data, we suggest that the AEA tone has the potential to be exploited as a novel diagnostic biomarker of infertility, to be used in association with assays of conventional hormones (e.g. progesterone, β-chorionic gonadotrophin) and semen analysis. However further quantitative research of its predictive capacity is required.

Alterations of maternal serum and placental follistatin-like 3 and myostatin in pre-eclampsia

AIM

To clarify the alterations of myostatin, a member of the transforming growth factor-β superfamily, and follistatin-like 3 (FSTL3), a binding protein for myostatin, in pre-eclamptic women.

METHODS

Samples of blood and placenta were collected from 40 pre-eclamptic women and 40 controls. The serum level and placental expression of FSTL3 and myostatin were determined with enzyme-linked immunosorbent assay, real-time polymerized chain reaction and western blotting.

RESULTS

The serum levels of myostatin and FSTL3 were significantly higher in pre-eclamptic women than in the controls (P < 0.001 for both). Placental expression of myostatin and FSTL3 were also significantly increased in the pre-eclamptic placenta compared with that of the controls (P < 0.001 for both); however, there were no significant differences in myostatin or FSTL3 in either the maternal serum or the placenta in women with mild or severe pre-eclampsia (P > 0.05 for both).

CONCLUSION

The serum levels and placental expression of myostatin and FSTL3 are elevated in pre-eclampsia, suggesting the role of myostatin and its binding protein in pre-eclampsia.

Circulating predictive biomarkers in preeclampsia

The aim of the paper was to review promising prediction biomarkers for preeclampsia. The methods included review of abstracts on PubMed, using "preeclampsia", "biomarker", "prediction" as key words, followed by review of primary papers investigating blood based biomarkers. Angiogenic factors, such as PlGf and sFlt1, and PP13 seem presently to have the best predictive test values for preeclampsia, but sensitivity and specificity is still too low to prove useful in a population screening setting. Biomarker testing should still be part of research protocols. Biomarkers could provide useful in selecting high-risk women for prophylactic trials as well as identifying pregnancies that could profit from closer follow-up.

Potential markers of preeclampsia--a review

Preeclampsia is a leading cause of maternal and fetal/neonatal mortality and morbidity worldwide. The early identification of patients with an increased risk for preeclampsia is therefore one of the most important goals in obstetrics. The availability of highly sensitive and specific physiologic and biochemical markers would allow not only the detection of patients at risk but also permit a close surveillance, an exact diagnosis, timely intervention (e.g. lung maturation), as well as simplified recruitment for future studies looking at therapeutic medications and additional prospective markers. Today, several markers may offer the potential to be used, most likely in a combinatory analysis, as predictors or diagnostic tools. We present here the current knowledge on the biology of preeclampsia and review several biochemical markers which may be used to monitor preeclampsia in a future, that, we hope, is not to distant from today.

Non-invasive prenatal diagnosis: implications for antenatal diagnosis and management of high-risk pregnancies

There has been a huge effort in the last 2-3 decades to develop non-invasive prenatal diagnosis to avoid the risks to the fetus caused by invasive procedures. Obtaining fetal nucleic material for molecular analysis without the need of invasive procedures has been a goal of prenatal diagnosis for many years; this is now been made possible by the use of non-cellular fetal nucleic acids circulating in maternal blood. The placenta is the primary source of these nucleic acids, raising the possibility that they could be a marker for pregnancy complications resulting from placental disease/dysfunction such as pre-eclampsia and fetal growth restriction. If so, these markers might be able to identify cases at risk, predict disease and/or its severity or allow early diagnosis. This has the potential to allow improvements in the management of complicated pregnancies.