Serum levels of GDF15 are reduced in preeclampsia and the reduction is more profound in late-onset than early-onset cases

GDF-15 Alleviates Hypoxia-Reoxygenation-Induced Damage to Human Placental Vascular Endothelial Cells by Regulating SIRT1

OBJECTIVE

Pregnancy-induced hypertension (PIH) is a common disease during pregnancy, which arises from maternal placental vascular endothelial cell dysfunction. Growth differentiation factor 15 (GDF-15) has a protective effect on the cardiovascular system. The purpose of this study is to explore the protective effect of GDF-15 against hypoxia-reoxygenation (H/R)-induced damage to human placental vascular endothelial cells (HPVECs) and the regulatory mechanism of SIRT1 in this effect.

METHODS

Serum samples from healthy pregnant women and those with PIH were collected, and their GDF-15 and SIRT1 levels were examined. HPVECs were cultured in vitro and induced with H/R and GDF-15 at varying concentrations. The optimal concentration of GDF-15 in protecting HPVECs was determined by measuring cell viability via the CCK-8 assay. In H/R-induced HPVECs treated with GDF-15 and compound C (the AMPK inhibitor), expression levels of SIRT1, p-AMPK, and t-AMPK were detected. Cell apoptosis was examined by flow cytometry.

RESULTS

Serum SIRT1 and GDF-15 were significantly higher in healthy pregnant women than in PIH patients. Suppressed viability and activated apoptosis in H/R-induced HPVECs were partially reversed by the treatment of GDF-15 at a concentration of 100 ng/mL. H/R induction significantly downregulated SIRT1 and p-AMPK in HPVECs, which were then upregulated by GDF-15. Moreover, the protective effect of GDF-15 on H/R-induced HPVECs was blocked by inhibiting the AMPK signaling pathway.

CONCLUSION

GDF-15 protects against H/R-inhibited cell viability and H/R-stimulated apoptosis in HPVECs by activating the AMPK signaling pathway to upregulate SIRT1.

Association between plasma growth differentiation factor 15 levels and pre-eclampsia in China

Background

Growth differentiation factor-15 (GDF-15) is a stress response protein and is related to cardiovascular diseases (CVD). This study aimed to investigate the association between GDF-15 and pre-eclampsia (PE).

Method

The study involved 299 pregnant women, out of which 236 had normal pregnancies, while 63 participants had PE. Maternal serum levels of GDF-15 were measured by using enzyme-linked immunosorbent assay kits and then translated into multiple of median (MOM) to avoid the influence of gestational week at blood sampling. Logistic models were performed to estimate the association between GDF-15 MOM and PE, presenting as odd ratios (ORs) and 95% confidence intervals (CIs).

Results

MOM of GDF-15 in PE participants was higher compared with controls (1.588 vs. 1.000, p < 0.001). In the logistic model, pregnant women with higher MOM of GDF-15 (>1) had a 4.74-fold (95% CI = 2.23-10.08, p < 0.001) increased risk of PE, adjusted by age, preconceptional body mass index, gravidity, and parity.

Conclusions

These results demonstrated that higher levels of serum GDF-15 were associated with PE. GDF-15 may serve as a biomarker for diagnosing PE.

GDF15 knockout does not substantially impact perinatal body weight or neonatal outcomes in mice

Growth differentiation factor-15 (GDF15) increases in circulation during pregnancy and has been implicated in food intake, weight loss, complications of pregnancy, and metabolic illness. We used a Gdf15 knockout mouse model (Gdf15-/- ) to assess the role of GDF15 in body weight regulation and food intake during pregnancy. We found that Gdf15-/- dams consumed a similar amount of food and gained comparable weight during the course of pregnancy compared to Gdf15+/+ dams. Insulin sensitivity on gestational day 16.5 was also similar between genotypes. In the postnatal period, litter size, and survival rates were similar between genotypes. There was a modest reduction in birth weight of Gdf15-/- pups, but this difference was no longer evident postnatal day 3.5 to 14.5. We observed no detectable differences in milk volume production or milk fat percentage. These data suggest that GDF15 is dispensable for changes in food intake, and body weight as well as insulin sensitivity during pregnancy in a mouse model.

MiR-3074-5p Regulates Trophoblasts Function via EIF2S1/GDF15 Pathway in Recurrent Miscarriage

Dysfunction of extravillous trophoblasts (EVTs) might cause early pregnancy failure by interfering with embryo implantation and/or placentation. We previously reported that the villus miR-3074-5p expression level was increased, whereas the peripheral level of GDF15, a predict target gene of miR-3074-5p, was decreased in recurrent miscarriages (RM) patients, and miR-3074-5p could enhance apoptosis but reduce invasion of human extravillous trophoblast cells (EVTs). The aim of this study was to further explore roles of miR-3074-5p/GDF15 pathway in regulation of EVTs function. It was validated that GDF15 was not the direct target of miR-3074-5p, whereas EIF2S1, an upstream regulator of GDF15 maturation and secretion, was the direct target of miR-3074-5p. The villus expression levels of GDF15 and EIF2S1 were significantly decreased in RM patients. Knockdown of GDF15 expression presented inhibitory effects on proliferation, migration, and invasion of HTR8/SVneo cells. Up-regulated miR-3074-5p expression led to the significant decreased GDF15 expression in HTR8/SVneo cells, and this effect could be efficiently reversed by the overexpression of EIF2S1. Meanwhile, the suppressive effects of miR-3074-5p on proliferation, migration, and invasion of HTR8/SVneo cells could be intercepted by the treatment of recombinant human GDF15 protein. Collectively, these data suggested that miR-3074-5p could reduce GDF15 production via targeting inhibition of EIF2S1 expression, and the deficiency in GDF15 function might lead to the early pregnancy loss by attenuating proliferation and invasion of EVTs.

Roles of bone morphogenetic proteins in endometrial remodeling during the human menstrual cycle and pregnancy

BACKGROUND

During the human menstrual cycle and pregnancy, the endometrium undergoes a series of dynamic remodeling processes to adapt to physiological changes. Insufficient endometrial remodeling, characterized by inadequate endometrial proliferation, decidualization and spiral artery remodeling, is associated with infertility, endometriosis, dysfunctional uterine bleeding, and pregnancy-related complications such as preeclampsia and miscarriage. Bone morphogenetic proteins (BMPs), a subset of the transforming growth factor-β (TGF-β) superfamily, are multifunctional cytokines that regulate diverse cellular activities, such as differentiation, proliferation, apoptosis, and extracellular matrix synthesis, are now understood as integral to multiple reproductive processes in women. Investigations using human biological samples have shown that BMPs are essential for regulating human endometrial remodeling processes, including endometrial proliferation and decidualization.

OBJECTIVE AND RATIONALE

This review summarizes our current knowledge on the known pathophysiological roles of BMPs and their underlying molecular mechanisms in regulating human endometrial proliferation and decidualization, with the goal of promoting the development of innovative strategies for diagnosing, treating and preventing infertility and adverse pregnancy complications associated with dysregulated human endometrial remodeling.

SEARCH METHODS

A literature search for original articles published up to June 2023 was conducted in the PubMed, MEDLINE, and Google Scholar databases, identifying studies on the roles of BMPs in endometrial remodeling during the human menstrual cycle and pregnancy. Articles identified were restricted to English language full-text papers.

OUTCOMES

BMP ligands and receptors and their transduction molecules are expressed in the endometrium and at the maternal-fetal interface. Along with emerging technologies such as tissue microarrays, 3D organoid cultures and advanced single-cell transcriptomics, and given the clinical availability of recombinant human proteins and ongoing pharmaceutical development, it is now clear that BMPs exert multiple roles in regulating human endometrial remodeling and that these biomolecules (and their receptors) can be targeted for diagnostic and therapeutic purposes. Moreover, dysregulation of these ligands, their receptors, or signaling determinants can impact endometrial remodeling, contributing to infertility or pregnancy-related complications (e.g. preeclampsia and miscarriage).

WIDER IMPLICATIONS

Although further clinical trials are needed, recent advancements in the development of recombinant BMP ligands, synthetic BMP inhibitors, receptor antagonists, BMP ligand sequestration tools, and gene therapies have underscored the BMPs as candidate diagnostic biomarkers and positioned the BMP signaling pathway as a promising therapeutic target for addressing infertility and pregnancy complications related to dysregulated human endometrial remodeling.

Molecular pathways in placental-fetal development and disruption

The first trimester of pregnancy ranks high in priority when minimizing harmful exposures, given the wide-ranging types of organogenesis occurring between 4- and 12-weeks' gestation. One way to quantify potential harm to the fetus in the first trimester is to measure a corollary effect on the placenta. Placental biomarkers are widely present in maternal circulation, cord blood, and placental tissue biopsied at birth or at the time of pregnancy termination. Here we evaluate ten diverse pathways involving molecules expressed in the first trimester human placenta based on their relevance to normal fetal development and to the hypothesis of placental-fetal endocrine disruption (perturbation in development that results in abnormal endocrine function in the offspring), namely: human chorionic gonadotropin (hCG), thyroid hormone regulation, peroxisome proliferator activated receptor protein gamma (PPARγ), leptin, transforming growth factor beta, epiregulin, growth differentiation factor 15, small nucleolar RNAs, serotonin, and vitamin D. Some of these are well-established as biomarkers of placental-fetal endocrine disruption, while others are not well studied and were selected based on discovery analyses of the placental transcriptome. A literature search on these biomarkers summarizes evidence of placenta-specific production and regulation of each biomarker, and their role in fetal reproductive tract, brain, and other specific domains of fetal development. In this review, we extend the theory of fetal programming to placental-fetal programming.

Insufficient GDF15 expression predisposes women to unexplained recurrent pregnancy loss by impairing extravillous trophoblast invasion

Insufficient extravillous trophoblast (EVT) invasion during early placentation has been shown to contribute to recurrent pregnancy loss (RPL). However, the regulatory factors involved and their involvement in RPL pathogenesis remain unknown. Here, we found aberrantly decreased growth differentiation factor 15 (GDF15) levels in both first-trimester villous and serum samples of unexplained recurrent pregnancy loss (URPL) patients as compared with normal pregnancies. Moreover, GDF15 knockdown significantly reduced the invasiveness of both HTR-8/SVneo cells and primary human EVT cells and suppressed the Jagged-1 (JAG1)/NOTCH3/HES1 pathway activity, and JAG1 overexpression rescued the invasion phenotype of the GDF15 knockdown cells. Induction of a lipopolysaccharide-induced abortion model in mice resulted in significantly reduced GDF15 level in the placenta and serum, as well as increased rates of embryonic resorption, and these effects were reversed by administration of recombinant GDF15. Our study thus demonstrates that insufficient GDF15 level at the first-trimester maternal-foetal interface contribute to the pathogenesis of URPL by impairing EVT invasion and suppressing JAG1/NOTCH3/HES1 pathway activity, and suggests that supplementation with GDF15 could benefit early pregnancy maintenance and reduce the risk of early pregnancy.

Two distinct molecular faces of preeclampsia revealed by single-cell transcriptomics

INTRODUCTION

Preeclampsia is a multisystemic, pregnancy-specific disorder united by new-onset hypertension but with considerable variation in clinical manifestation, onset, and severity. For symptoms to regress, delivery of the placenta is required. For symptoms to regress, delivery of the placenta is required, making the placenta central to preeclampsia pathophysiology. To dissect which placental functions were impacted in two forms of preeclampsia, we studied molecular changes across the cell types of the placenta.

METHODS

We performed a transcriptomic survey of single-cells and single-nuclei on cases of early- and late-onset preeclampsia with gestation-matched controls.

FINDINGS

Our data revealed massive dysregulation of gene expression in all cell classes that was almost exclusive to early preeclampsia. For example, an important known receptor/ligand imbalance hallmarking angiogenic disfunction, sFLT1/placental growth factor (PGF), was reflected in striking, cell-autonomous dysregulation of FLT1 and PGF transcription in the syncytium in early preeclampsia only. Stromal cells and vasculature echoed an inflamed, stressed, anti-angiogenic environment. Finally, the placental immune niche set the tone for inflammation in early but not late preeclampsia. Here, fetal-origin Hofbauer and maternal-origin TREM2 macrophages were revealed as surprising main actors, while local cells of the adaptive immune system were largely unaffected. Late preeclampsia showed minimal cellular impact on the placenta.

CONCLUSIONS

Our survey provides systematic molecular evidence for two distinct diseases. We resolved systematic molecular dysregulation to individual cell types with strong implications for definition, early detection, diagnosis, and treatment.

FUNDING

Funded by the Preeclampsia Foundation through the Peter Joseph Pappas Research Grant.

Growth differentiation factor 15 (GDF-15) in endocrinology

Human growth differentiation factor 15 (GDF-15) is a widely distributed protein that has shown to play multiple roles in both physiological and pathological conditions. In healthy individuals, GDF-15 is mainly expressed in the placenta, followed by the prostate, although low levels of expression have also been detected in different organs. GDF-15 acts through a recently identified receptor called glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL) which signals through the rearranged during transfection (RET) tyrosine kinase receptor. The effects of GDF-15 are pleiotropic and include appetite regulation, and actions on metabolism, pregnancy, cell survival, immune response, and inflammation. GDF-15 also plays different roles in the pathophysiology of cardiovascular disease, autoimmunity, cancer-associated anorexia/cachexia, and diabetes. In recent years, several studies have reported a link between GDF-15 and the endocrine system. In this review, we up-date and summarize the relevant investigations of the relationships between GDF-15 and different endocrine conditions. We also assess the potential pathogenic role and potential therapeutic applications of GDF-15 in the field of endocrinology.

Adipokines in Pregnancy: A Systematic Review of Clinical Data

Adipokines are signaling proteins involved in metabolic, endocrinological, vascular and immunogenic processes. Associations of various adipokines with not only insulin resistance but also with increased insulin sensitivity, increased systolic blood pressure, and atherosclerosis highlight the significance of adipokines in several components of metabolic syndrome and metabolic diseases in general. As pregnancy presents a unique metabolic state, the role of adipokines in pregnancy, and even in various pregnancy complications, appears to be key to elucidating these metabolic processes. Many studies in recent years have attempted to clarify the role of adipokines in pregnancy and gestational pathologies. In this review, we aim to investigate the changes in maternal adipokine levels in physiological gestation, as well as the association of adipokines with pregnancy pathologies, such as gestational diabetes mellitus (GDM) and preeclampsia (PE). Furthermore, we will analyze the association of adipokines in both maternal serum and cord blood with parameters of intrauterine growth and various pregnancy outcomes.

Impact of maternal iron deficiency anemia on fetal iron status and placental iron transporters in human pregnancy

Iron deficiency anemia is associated with maternal morbidity and poor pregnancy outcomes. Heme and non-heme iron transport proteins expressed in the placenta help in adequate iron supply from anemic mother to fetus. Here we examined the expression of placental iron trafficking molecules and their association with maternal and neonatal iron status in pregnant women with iron deficiency anemia (IDA). Pregnant women who received prenatal care at Christian Medical College, Vellore, India for childbirth were recruited. Pregnant women who were 18-35 years old with gestational age (GA) of ≥36 weeks were eligible to participate in the study. In a prospective cohort of pregnant women, 22 % were iron deficiency anemia and 42 % were iron replete. Samples were collected (Maternal blood, placental tissue, and cord blood) from pregnant women with a gestational age of ≥38 weeks at the time of delivery. The mean gestational age at the first visit and delivery was 12.8 ± 2.72 weeks and 39 ± 1.65 weeks, respectively. Hemoglobin (9.3 ± 0.9 g/dl) and ferritin (15.4(0.8-28.3) ng/ml) levels at delivery were significantly decreased in IDA as compared to controls. The fetal hemoglobin and ferritin levels were in the normal range in both groups. There was no correlation between maternal and cord blood hepcidin with fetal iron status in IDA. We further analyzed the expression of iron transport genes in the placenta of controls and the IDA group. Under maternal iron insufficiency, the expression of placental iron transporters DMT1, FPN1, and GDF15 was upregulated at the protein level. In IDA, placental GDF15 and ferroportin protein had an association with fetal iron status. These findings confirm that placental iron traffickers respond to maternal iron deficiency by increasing their expression and allowing sufficient iron to pass to the fetus.

Circulating Growth Differentiation Factor 15 and Preeclampsia: A Meta-Analysis

Growth differentiation factor 15 (GDF-15) has been suggested as a potential biomarker of preeclampsia. However, previous studies evaluating circulating GDF-15 in women with preeclampsia showed inconsistent results. A meta-analysis was performed accordingly in this study. Observational studies comparing circulating GDF-15 between women with preeclampsia normal pregnancy were identified by search of electronic databases including PubMed, Embase, Web of Science, Wanfang, and CNKI. The Newcastle-Ottawa Scale (NOS) was used for assessing the quality of the studies. A randomized-effect model incorporating the possible between-study heterogeneity was used to pool the results. Eleven observational studies including 498 women with preeclampsia and 2349 women with normal pregnancy contributed to the meta-analysis. Results showed that compared to controls of women with normal pregnancy at least matched for gestational ages, women with preeclampsia had significantly higher circulating GDF-15 at the diagnosis [standard mean difference (SMD): 0.66, 95% confidence interval (CI): 0.16 to 1.17, p=0.01, I2=93%]. Subgroup analysis showed consistent results in women with preterm and term preeclampsia in Asian and non-Asian women and in studies with different quality scores, which were not statistically significant between subgroups (p for subgroup difference>0.05). Moreover, a higher level of GDF-15 was also found before the diagnosis in women who subsequently developed preeclampsia than those who did not (SMD: 1.32, 95% CI: 0.45 to 2.18, p=0.003, I2=89%). In conclusion, a higher circulating GDF-15 is observed in women with preeclampsia even before the diagnosis of the disease.

Circulating cardiovascular biomarkers during and after preeclampsia: Crosstalk with placental function?

Cardiovascular disease (CVD) is the leading cause of death in women, yet sex-specific risk factors remain understudied. Preeclampsia and other adverse pregnancy outcomes imply an increased maternal cardiovascular risk. We hypothesized that cardiac troponin T (cTnT), N-terminal pro-Brain Natriuretic Peptide (NT-proBNP) and growth differentiation factor 15 (GDF-15) are increased in such pregnancies and correlate with markers of placental dysfunction. We also investigated these cardiovascular biomarkers 1 or 3 years postpartum. Prior to delivery, we included serum from 417 pregnant women: 55 early-onset preeclampsia (EO-PE), 63 late-onset preeclampsia (LO-PE), 30 gestational hypertension (GH) and 269 healthy controls. Postpartum, we included 341 women 1 or 3 years after delivery: 26 EO-PE, 107 LO-PE, 61 GH, and 147 healthy pregnancies. Prior to delivery, median cTnT and NT-proBNP concentrations were higher in women with EO-PE, LO-PE, or GH than in controls. Median GDF-15 was higher in EO-PE and LO-PE compared to controls. Postpartum, GDF-15 was elevated in women with previous EO-PE. Markers of placental dysfunction correlated with CVD biomarkers in pregnancy, but not postpartum. Our findings underscore the cardiovascular burden of hypertensive disorders of pregnancy and the crosstalk with placental function. The upregulation of circulating GDF-15 following early-onset preeclampsia is in line with the epidemiological excessive risk of premature CVD in this group of women. GDF-15 may be explored for targeting postpartum women with most to gain from intensified preventive follow-up for CVD.

NRF2 Serves a Critical Role in Regulation of Immune Checkpoint Proteins (ICPs) During Trophoblast Differentiation

Using cultured human trophoblast stem cells (hTSCs), mid-gestation human trophoblasts in primary culture, and gene-targeted mice, we tested the hypothesis that the multinucleated syncytiotrophoblast (SynT) serves a critical role in pregnancy maintenance through production of key immune modulators/checkpoint proteins (ICPs) under control of the O2-regulated transcription factor, NRF2/NFE2L2. These ICPs potentially act at the maternal-fetal interface to protect the hemiallogeneic fetus from rejection by the maternal immune system. Using cultured hTSCs, we observed that several ICPs involved in the induction and maintenance of immune tolerance were markedly upregulated during differentiation of cytotrophoblasts (CytTs) to SynT. These included HMOX1, kynurenine receptor, aryl hydrocarbon receptor, PD-L1, and GDF15. Intriguingly, NRF2, C/EBPβ, and PPARγ were markedly induced when CytTs fused to form SynT in a 20% O2 environment. Notably, when hTSCs were cultured in a hypoxic (2% O2) environment, SynT fusion and the differentiation-associated induction of NRF2, C/EBPβ, aromatase (CYP19A1; SynT differentiation marker), and ICPs were blocked. NRF2 knockdown also prevented induction of aromatase, C/EBPβ and the previously mentioned ICPs. Chromatin immunoprecipitation-quantitative PCR revealed that temporal induction of the ICPs in hTSCs and mid-gestation human trophoblasts cultured in 20% O2 was associated with increased binding of endogenous NRF2 to putative response elements within their promoters. Moreover, placentas of 12.5 days postcoitum mice with a global Nrf2 knockout manifested decreased mRNA expression of C/ebpβ, Pparγ, Hmox1, aryl hydrocarbon receptor, and Nqo1, another direct downstream target of Nrf2, compared with wild-type mice. Collectively, these compelling findings suggest that O2-regulated NRF2 serves as a key regulator of ICP expression during SynT differentiation.

Increased serum concentrations of growth differentiation factor-15 in children with acute rheumatic fever

AIM

In this single-centre prospective study, we aimed to evaluate the role of growth differentiation factor-15 in children with acute rheumatic fever.

METHODS

The study group included 25 children with acute rheumatic fever, and the control group included 25 healthy children. In addition to routine laboratory tests used in the diagnosis and treatment of acute rheumatic fever, growth differentiation factor-15 levels of the study group (at the time of diagnosis and after the treatment) and the control group were assessed and compared.

RESULTS

The mean growth differentiation factor-15 level of the study group at the time of diagnosis (918.40 ± 605.65 pg/ml) was significantly higher than the mean post-treatment level (653.08 ± 330.92 pg/ml) (p = 0.015). Similarly, the mean growth differentiation factor-15 level of the study group at the time of diagnosis was significantly higher than the control group (p = 0.04). However, mean growth differentiation factor-15 levels were similar between the groups after the treatment. Growth differentiation factor-15 was positively correlated with both C-reactive protein (p < 0.001) and erythrocyte sedimentation rate (p = 0.001) at the time of diagnosis.

CONCLUSION

Growth differentiation factor-15 levels are significantly increased in children with acute rheumatic fever at the time of diagnosis and return to similar levels with healthy children after treatment. Growth differentiation factor-15 is positively and significantly correlated with erythrocyte sedimentation rate and C-reactive protein at the time of diagnosis.

Placental energy metabolism in health and disease-significance of development and implications for preeclampsia

The placenta is a highly metabolically active organ fulfilling the bioenergetic and biosynthetic needs to support its own rapid growth and that of the fetus. Placental metabolic dysfunction is a common occurrence in preeclampsia although its causal relationship to the pathophysiology is unclear. At the outset, this may simply be seen as an "engine out of fuel." However, placental metabolism plays a vital role beyond energy production and is linked to physiological and developmental processes. In this review, we discuss the metabolic basis for placental dysfunction and propose that the alterations in energy metabolism may explain many of the placental phenotypes of preeclampsia such as reduced placental and fetal growth, redox imbalance, oxidative stress, altered epigenetic and gene expression profiles, and the functional consequences of these aberrations. We propose that placental metabolic reprogramming reflects the dynamic physiological state allowing the tissue to adapt to developmental changes and respond to preeclampsia stress, whereas the inability to reprogram placental metabolism may result in severe preeclampsia phenotypes. Finally, we discuss common tested and novel therapeutic strategies for treating placental dysfunction in preeclampsia and their impact on placental energy metabolism as possible explanations into their potential benefits or harm.

Serum and urine profiles of TGF-β superfamily members in reproductive aged women

BACKGROUND

TGF-β superfamily members are important biomarkers of reproductive health in women desiring fertility and during pregnancy. TGF-β proteins derived from the ovary and/or placenta have been detected in serum in women, but there have been very few attempts to measure them non-invasively, such as in urinary samples, and to compare them to serum concentrations.

METHODS

We measured inhibin A, inhibin B, total inhibin, AMH, activin A, activin B, activin AB, follistatin, the GDF-9/BMP-15 complex, and GDF-15 in paired serum and urine samples from healthy reproductive aged women and in pregnant (second trimester) women.

RESULTS

We detected all hormones in serum in both pregnant and non-pregnant women. Inhibin A, total inhibin, activin A, activin AB, follistatin, and GDF-15 were significantly higher in pregnant than in non-pregnant women. GDF-15 was the only hormone consistently detected in urine. We also measured, for the first time, the GDF-9/BMP-15 functional heterodimer and the GDF-15 protein harboring the H202D polymorphism.

CONCLUSIONS

We report the successful measurement of the GDF-9/BMP-15 heterodimer (its native form) in serum and the ability to measure GDF-15 non-invasively, in urinary samples. This novel GDF-15 assay also captures the antigen in the presence of a common genetic variant.

Circulating Growth Differentiation Factor 15 Is Increased Preceding Preeclampsia Diagnosis: Implications as a Disease Biomarker

Background

We investigated the biomarker potential of growth differentiation factor 15 (GDF‐15), a stress response protein highly expressed in placenta, to predict preeclampsia.

Methods and Results

In 2 prospective cohorts (cohort 1: 960 controls, 39 women who developed preeclampsia; cohort 2: 950 controls, 41 developed preeclampsia), plasma concentrations of GDF‐15 at 36 weeks' gestation were significantly increased among those who developed preeclampsia (P<0.001), area under the receiver operating characteristic curves (AUC) of 0.66 and 0.71, respectively. In cohort 2 a ratio of sFlt‐1/PlGF (a clinical biomarker for preeclampsia) had a sensitivity of 61.0% at 83.2% specificity to predict those who will develop preeclampsia (AUC of 0.79). A ratio of GDF‐15×sFlt‐1/PlGF yielded a sensitivity of 68.3% at 83.2% specificity (AUC of 0.82). GDF‐15 was consistently elevated across a number of international cohorts: levels were higher in placenta and blood from women delivering <34 weeks' gestation due to preterm preeclampsia in Melbourne, Australia; and in the blood at 26 to 32 weeks' gestation among 57 women attending the Manchester Antenatal Vascular Service (MAViS, UK) who developed preeclampsia (P=0.0002), compared with 176 controls. In the Preeclampsia Obstetric adVerse Events biobank (PROVE, South Africa), plasma GDF‐15 was significantly increased in women with preeclampsia with severe features (P=0.02; n=14) compared to controls (n=14).

Conclusions

We conclude circulating GDF‐15 is elevated among women more likely to develop preeclampsia or diagnosed with the condition. It may have value as a clinical biomarker, including the potential to improve the sensitivity of sFlt‐1/PlGF ratio.

Fragile X-Related Protein 1 (FXR1) Promotes Trophoblast Migration at Early Pregnancy via Downregulation of GDF-15 Expression

Fragile X-related protein 1 (FXR1) is an RNA-binding protein that can regulate specific mRNA decay in cells. Our previous study showed that FXR1 expression was significantly decreased in trophoblasts from patients with unexplained recurrent spontaneous abortion (RSA); however, the role of FXR1 in trophoblast function during early placenta development has not been fully elucidated. In this study, we found that knockdown of FXR1 using siRNA effectively inhibited the migration of HTR-8 cells and extravillous trophoblast (EVT) outgrowth in an ex vivo extravillous explant culture model. Furthermore, through analysis of a panel of cytokines, we found that the GDF-15 protein was upregulated after knockdown of FXR1 in HTR-8/SVneo cells. This was further confirmed by western blotting and immunofluorescence in HTR-8/SVneo cells and an extravillous explant. Our data also showed that FXR1 expression was downregulated and GDF-15 was upregulated in chorionic villous tissues from RSA patients compared with those from healthy controls (HCs). Further, immunohistochemistry showed a strong expression of GDF-15 in chorionic villous tissue in the RSA group, which was mainly distributed in villous trophoblasts (CTBs) and syncytiotrophoblasts (STBs). Moreover, knockdown of GDF-15 enhanced the migration of HTR-8 cells, while overexpression of GDF-15 using plasmid or treatment with recombinant human GDF-15 protein inhibited trophoblast migration. Importantly, RNA-binding protein immunoprecipitation showed that FXR1 directly bound to the 3'-UTR of GDF-15 mRNA to promote GDF-15 mRNA decay. Together, our data provide new insight into the function of FXR1 in human placenta via regulation of GDF-15 expression in trophoblasts and suggest a possible pathological process involved in RSA.

Maternal genetics influences fetal neurodevelopment and postnatal autism spectrum disorder-like phenotype by modulating in-utero immunosuppression

Genetic studies in ASD have mostly focused on the proband, with no clear understanding of parental genetic contributions to fetal neurodevelopment. Among parental etiological factors, perinatal maternal inflammation secondary to autoimmunity, infections, and toxins is associated with ASD. However, the inherent impact of maternal genetics on in-utero inflammation and fetal neurodevelopment in the absence of strong external inflammatory exposures is not known. We used the PtenWT/m3m4 mouse model for ASD to demonstrate the impact of maternal genetics on the penetrance of ASD-like phenotypes in the offspring. PtenWT/m3m4 (Momm3m4) or PtenWT/WT (MomWT) females, their offspring, and placental interface were analyzed for inflammatory markers, gene expression, and cellular phenotypes at E17.5. Postnatal behavior was tested by comparing pups from Momm3m4 vs. MomWT. Mothers of the PtenWT/m3m4 genotype (Momm3m4) showed inadequate induction of IL-10 mediated immunosuppression during pregnancy. Low IL-10 in the mother was directly correlated with decreased complement expression in the fetal liver. Fetuses from Momm3m4 had increased breakdown of the blood-brain-barrier, neuronal loss, and lack of glial cell maturation during in-utero stages. This impact of maternal genotype translated to a postnatal increase in the risk of newborn mortality, visible macrocephaly and ASD-like repetitive and social behaviors. Depending on maternal genotype, non-predisposed (wildtype) offspring showed ASD-like phenotypes, and phenotypic penetrance was decreased in predisposed pups from MomWT. Our study introduces the concept that maternal genetics alone, without any added external inflammatory insults, can modulate fetal neurodevelopment and ASD-related phenotypes in the offspring via alteration of IL-10 mediated materno-fetal immunosuppression.

RNA Network Interactions During Differentiation of Human Trophoblasts

In the human placenta, two trophoblast cell layers separate the maternal blood from the villous basement membrane and fetal capillary endothelial cells. The inner layer, which is complete early in pregnancy and later becomes discontinuous, comprises the proliferative mononuclear cytotrophoblasts, which fuse together and differentiate to form the outer layer of multinucleated syncytiotrophoblasts. Because the syncytiotrophoblasts are responsible for key maternal-fetal exchange functions, tight regulation of this differentiation process is critical for the proper development and the functional role of the placenta. The molecular mechanisms regulating the fusion and differentiation of trophoblasts during human pregnancy remain poorly understood. To decipher the interactions of non-coding RNAs (ncRNAs) in this process, we exposed cultured primary human trophoblasts to standard in vitro differentiation conditions or to conditions known to hinder this differentiation process, namely exposure to hypoxia (O₂ < 1%) or to the addition of dimethyl sulfoxide (DMSO, 1.5%) to the culture medium. Using next generation sequencing technology, we analyzed the differential expression of trophoblastic lncRNAs, miRNAs, and mRNAs that are concordantly modulated by both hypoxia and DMSO. Additionally, we developed a model to construct a lncRNA-miRNA-mRNA co-expression network and inferred the functions of lncRNAs and miRNAs via indirect gene ontology analysis. This study improves our knowledge of the interactions between ncRNAs and mRNAs during trophoblast differentiation and identifies key biological processes that may be impaired in common gestational diseases, such as fetal growth restriction or preeclampsia.

Cardiac Biomarkers in hypertensive disorders of pregnancy

In recent years, biomarkers have taken a central place in the assessment of cardiovascular diseases – from prediction to management and prognosis. On the other hand, enough evidence exists to assume that hypertensive disorders of pregnancy share a certain connection with cardiovascular diseases – from common risk factors and underlying mechanisms to the presence of a higher risk for women for the development of a great number of cardiovascular diseases, such as arterial hypertension, coronary atherosclerosis, stroke, peripheral artery disease, venous thromboembolism, and even a higher cardiovascular mortality. The key to a better understanding of the unfavorable cardiovascular profile of women with a hypertensive disorder of pregnancy may lie in their assessment with biomarkers, typically used in the field of cardiology. In this review, we have included studies investigating the use of cardiovascular biomarkers during or after a hypertensive pregnancy, namely, natriuretic peptides, high-sensitivity cardiac troponins, growth/differentiation factor 15 (GDF15), soluble suppression of tumorigenicity-2 (sST2), and galectin-3.

Roles of TGF-β Superfamily Proteins in Extravillous Trophoblast Invasion

Following embryo implantation, extravillous trophoblasts (EVTs) invade the maternal decidua to a certain extent during early pregnancy, which is critical for normal placentation and successful pregnancy in humans. Although sharing a similar protein structure, the transforming growth factor-β (TGF-β) superfamily members exert divergent functions in regulating EVT invasion, which contributes to a relative balance of TGF-β superfamily proteins in precisely modulating this process at the maternal-fetal interface during the first trimester of pregnancy. This review details recent advances in our understanding of the functions of TGF-β superfamily members and their corresponding receptors, signaling pathways, and downstream molecular targets in regulating human EVT invasion from studies using various in vitro or ex vivo experimental models. Also, the relevance of these discoveries about TGF-β superfamily members to adverse pregnancy outcomes is summarized. The application of 3D culture trophoblast organoids, single-cell sequencing, and microfluidic assays in EVT invasion studies will help better reveal the molecular mechanisms through which TGF-β superfamily members regulate human EVT invasion, shedding light on the development of innovative strategies for predicting, diagnosing, treating, and preventing adverse human pregnancy outcomes related to EVT invasion dysfunction.

Second- and third-trimester serum levels of growth-differentiation factor-15 in prediction of pre-eclampsia

OBJECTIVE

Pre-eclampsia (PE) is a significant contributor to adverse maternal and perinatal outcome; however, accurate prediction and early diagnosis of this condition remain a challenge. The aim of this study was to compare serum levels of growth-differentiation factor-15 (GDF-15) at three different gestational ages between asymptomatic women who subsequently developed preterm or term PE and healthy controls.

METHODS

This was a case-control study drawn from a prospective observational study on adverse pregnancy outcomes in women attending for their routine second- and third-trimester hospital visits. Serum GDF-15 was determined in 300 samples using a commercial GDF-15 enzyme-linked immunosorbent assay: 120 samples at 19-24 weeks of gestation, 120 samples at 30-34 weeks and 60 samples at 35-37 weeks. Multiple linear regression was applied to logarithmically transformed GDF-15 control values to evaluate the influence of gestational age at blood sampling and maternal characteristics on GDF-15 results. GDF-15 multiples of the normal median (MoM) values, adjusted for gestational age and maternal characteristics, were compared between pregnancies that subsequently developed preterm or term PE and healthy controls.

RESULTS

Values of GDF-15 increased with gestational age. There were no significant differences in GDF-15 MoM values between cases of preterm or term PE and normotensive pregnancies at 19-24 or 35-37 weeks of gestation. At 30-34 weeks, GDF-15 MoM values were significantly increased in cases of preterm PE, but not in those who later developed term PE. Elevated GDF-15 MoM values were associated significantly with a shorter interval between sampling at 30-34 weeks and delivery with PE (P = 0.005).

CONCLUSION

Serum GDF-15 levels at 19-24 or 35-37 weeks of gestation are not predictive of preterm or term PE. At 30-34 weeks, GDF-15 levels are higher in women who subsequently develop preterm PE; however, this difference is small and GDF-15 is unlikely to be useful in clinical practice when used in isolation. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

The GDF15-GFRAL Pathway in Health and Metabolic Disease: Friend or Foe?

GDF15 is a cell activation and stress response cytokine of the glial cell line-derived neurotrophic factor family within the TGF-β superfamily. It acts through a recently identified orphan member of the GFRα family called GFRAL and signals through the Ret coreceptor. Cell stress and disease lead to elevated GDF15 serum levels, causing anorexia, weight loss, and alterations to metabolism, largely by actions on regions of the hindbrain. These changes restore homeostasis and, in the case of obesity, cause a reduction in adiposity. In some diseases, such as advanced cancer, serum GDF15 levels can rise by as much as 10-100-fold, leading to an anorexia-cachexia syndrome, which is often fatal. This review discusses how GDF15 regulates appetite and metabolism, the role it plays in resistance to obesity, and how this impacts diseases such as diabetes, nonalcoholic fatty liver disease, and anorexia-cachexia syndrome. It also discusses potential therapeutic applications of targeting the GDF15-GFRAL pathway and lastly suggests some potential unifying hypotheses for its biological role.

Growth/Differentiation Factor-15 (GDF-15): From Biomarker to Novel Targetable Immune Checkpoint

Growth/differentiation factor-15 (GDF-15), also named macrophage inhibitory cytokine-1, is a divergent member of the transforming growth factor β superfamily. While physiological expression is barely detectable in most somatic tissues in humans, GDF-15 is abundant in placenta. Elsewhere, GDF-15 is often induced under stress conditions, seemingly to maintain cell and tissue homeostasis; however, a moderate increase in GDF-15 blood levels is observed with age. Highly elevated GDF-15 levels are mostly linked to pathological conditions including inflammation, myocardial ischemia, and notably cancer. GDF-15 has thus been widely explored as a biomarker for disease prognosis. Mechanistically, induction of anorexia via the brainstem-restricted GDF-15 receptor GFRAL (glial cell-derived neurotrophic factor [GDNF] family receptor α-like) is well-documented. GDF-15 and GFRAL have thus become attractive targets for metabolic intervention. Still, several GDF-15 mediated effects (including its physiological role in pregnancy) are difficult to explain via the described pathway. Hence, there is a clear need to better understand non-metabolic effects of GDF-15. With particular emphasis on its immunomodulatory potential this review discusses the roles of GDF-15 in pregnancy and in pathological conditions including myocardial infarction, autoimmune disease, and specifically cancer. Importantly, the strong predictive value of GDF-15 as biomarker may plausibly be linked to its immune-regulatory function. The described associations and mechanistic data support the hypothesis that GDF-15 acts as immune checkpoint and is thus an emerging target for cancer immunotherapy.

Pre-eclampsia: pathophysiology and clinical implications

Pre-eclampsia is a common disorder that particularly affects first pregnancies. The clinical presentation is highly variable but hypertension and proteinuria are usually seen. These systemic signs arise from soluble factors released from the placenta as a result of a response to stress of syncytiotrophoblast. There are two sub-types: early and late onset pre-eclampsia, with others almost certainly yet to be identified. Early onset pre-eclampsia arises owing to defective placentation, whilst late onset pre-eclampsia may center around interactions between normal senescence of the placenta and a maternal genetic predisposition to cardiovascular and metabolic disease. The causes, placental and maternal, vary among individuals. Recent research has focused on placental-uterine interactions in early pregnancy. The aim now is to translate these findings into new ways to predict, prevent, and treat pre-eclampsia.

Placenta-derived exosomes: potential biomarkers of preeclampsia

Preeclampsia remains a leading cause of maternal and fetal mortality, due to ineffective treatment and diagnostic strategies, compounded by the lack of clarity on the etiology of the disorder. Although several clinical and biological markers of preeclampsia have been evaluated, they have proven to be ineffective in providing a definitive diagnosis during the various stages of the disorder. Exosomes have emerged as ideal biomarkers of pathological states, such as cancer, and have more recently gained interest in pregnancy-related complications, due to their role in cellular communication in normal and complicated pregnancies. This occurs as a result of the specific placenta-derived exosomal molecular cargo, which may be involved in normal pregnancy-associated immunological events, such as the maintenance of maternal-fetal tolerance. This review provides perspectives on placenta-derived exosomes as possible biomarkers for the diagnosis/prognosis of preeclampsia. Using keywords, online databases were searched to identify relevant publications to review the potential use of placenta-derived exosomes as biomarkers of preeclampsia.

Multiple Soluble TGF-β Receptors in Addition to Soluble Endoglin Are Elevated in Preeclamptic Serum and They Synergistically Inhibit TGF-β Signaling

CONTEXT

Preeclampsia (PE) can be classified into early-onset (<34 weeks of gestation) and late-onset (>34 weeks of gestation) subtypes. Soluble endoglin, an auxiliary receptor for transforming growth factor (TGF)-β ligands, is increased in PE circulation and believed to inhibit TGF-β action by sequestering the ligands. However, soluble endoglin, with a low affinity to TGF-β ligands, has been demonstrated to have little effect by itself on TGF-β action.

OBJECTIVES

We examined whether multiple soluble TGF-β receptors are elevated in PE circulation and whether they synergistically block TGF-β signaling.

DESIGN

TGF-β receptors were measured using enzyme-linked immunosorbent assay in sera collected from preeclamptic pregnancies and gestation-age-matched controls. TGF-β signaling was assessed using an in vitro bioassay and a tube formation assay.

RESULTS

TGF-β type I, II, and III receptors were all identified in pregnant serum; all were substantially elevated in early-onset but not late-onset PE. Endoglin was increased in both subtypes. At the greatest concentrations detected in PE, none of these soluble TGF-β receptors alone, including endoglin, inhibited TGF-β signaling. However, when all four soluble receptors were present, signaling of both TGF-β1 and TGF-β2 was substantially reduced. Removal of any one of these soluble receptors alleviated TGF-β1 inhibition; however, removal of soluble TGFβRIII was necessary to relieve TGF-β2 inhibition.

CONCLUSIONS

Multiple soluble TGF-β receptors are present in pregnant circulation and elevated in early-onset PE; they synergistically inhibit TGF-β signaling, which might be more likely to occur in early-onset than late-onset PE. Reducing soluble TGFβRIII, rather than endoglin, would be more effective in alleviating the inhibition of both TGF-β1 and TGF-β2 signaling in PE.

High levels of HtrA4 observed in preeclamptic circulation drastically alter endothelial gene expression and induce inflammation in human umbilical vein endothelial cells

Introduction

Preeclampsia (PE) is a life-threatening pregnancy disorder characterized by wide-spread endothelial dysfunction. Placental factors circulating in the maternal blood are believed to cause endothelial dysfunction. Our previous study identified HtrA4 as a placenta-specific serine protease that is released into the maternal circulation and significantly increased in early-onset PE. In this study, we examined the impact of HtrA4 on expression of endothelial genes related to vessel biology, using human umbilical vein endothelial cells (HUVECs) as a model.

Methods

HUVECs were treated with 0 or 3 μg/ml HtrA4 (highest concentration seen in PE circulation) for 24 h and analysed by an endothelial cell biology PCR array containing 84 genes. HtrA4-induced changes were then validated by real-time RT-PCR and ELISA for time and dose dependency.

Results

High levels of HtrA4 significantly altered the expression of a range of genes related to inflammation, vaso-activity, angiogenesis, cell adhesion, platelet activation and coagulation. In particular, pro-inflammatory genes IL6, PTGS2 (COX2) and IL1B were significantly increased by HtrA4. IL6 protein in HUVEC media was also drastically increased. THBD, an anticoagulant factor reported to be increased in PE, was significantly up-regulated by HtrA4. In contrast, THBS1, which is involved in many regulatory processes of endothelial cell biology, was severely down-regulated by HtrA4.

Discussion

HtrA4 significantly increased the inflammatory responses of HUVECs, and altered their expression of a number of genes important for vessel biology. These data suggest that placenta-derived HtrA4 that is increased in PE circulation is a potential causal factor of endothelial dysfunction.

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HtrA4 altered expression of endothelial genes involved in vessel biology.

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HtrA4 significantly induced inflammation in endothelial cells.

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Placental-derived HtrA4 is a potential causal factor of endothelial dysfunction.