Pattern of secretion of pregnancy-associated plasma protein-A (PAPP-A) during pregnancies complicated by fetal aneuploidy, in vivo and in vitro

Placenta: an old organ with new functions

The transition from oviparity to viviparity and the establishment of feto-maternal communications introduced the placenta as the major anatomical site to provide nutrients, gases, and hormones to the developing fetus. The placenta has endocrine functions, orchestrates maternal adaptations to pregnancy at different periods of pregnancy, and acts as a selective barrier to minimize exposure of developing fetus to xenobiotics, pathogens, and parasites. Despite the fact that this ancient organ is central for establishment of a normal pregnancy in eutherians, the placenta remains one of the least studied organs. The first step of pregnancy, embryo implantation, is finely regulated by the trophoectoderm, the precursor of all trophoblast cells. There is a bidirectional communication between placenta and endometrium leading to decidualization, a critical step for maintenance of pregnancy. There are three-direction interactions between the placenta, maternal immune cells, and the endometrium for adaptation of endometrial immune system to the allogeneic fetus. While 65% of all systemically expressed human proteins have been found in the placenta tissues, it expresses numerous placenta-specific proteins, whose expression are dramatically changed in gestational diseases and could serve as biomarkers for early detection of gestational diseases. Surprisingly, placentation and carcinogenesis exhibit numerous shared features in metabolism and cell behavior, proteins and molecular signatures, signaling pathways, and tissue microenvironment, which proposes the concept of "cancer as ectopic trophoblastic cells". By extensive researches in this novel field, a handful of cancer biomarkers has been discovered. This review paper, which has been inspired in part by our extensive experiences during the past couple of years, highlights new aspects of placental functions with emphasis on its immunomodulatory role in establishment of a successful pregnancy and on a potential link between placentation and carcinogenesis.

The role of pregnancy associated plasma protein-A in triple negative breast cancer: a promising target for achieving clinical benefits

Pregnancy associated plasma protein-A (PAPP-A) plays an integral role in breast cancer (BC), especially triple negative breast cancer (TNBC). This subtype accounts for the most aggressive BC, possesses high tumor heterogeneity, is least responsive to standard treatments and has the poorest clinical outcomes. There is a critical need to address the lack of effective targeted therapeutic options available. PAPP-A is a protein that is highly elevated during pregnancy. Frequently, higher PAPP-A expression is detected in tumors than in healthy tissues. The increase in expression coincides with increased rates of aggressive cancers. In BC, PAPP-A has been demonstrated to play a role in tumor initiation, progression, metastasis including epithelial-mesenchymal transition (EMT), as well as acting as a biomarker for predicting patient outcomes. In this review, we present the role of PAPP-A, with specific focus on TNBC. The structure and function of PAPP-A, belonging to the pappalysin subfamily, and its proteolytic activity are assessed. We highlight the link of BC and PAPP-A with respect to the IGFBP/IGF axis, EMT, the window of susceptibility and the impact of pregnancy. Importantly, the relevance of PAPP-A as a TNBC clinical marker is reviewed and its influence on immune-related pathways are explored. The relationship and mechanisms involving PAPP-A reveal the potential for more treatment options that can lead to successful immunotherapeutic targets and the ability to assist with better predicting clinical outcomes in TNBC.

The effect of a vanishing twin on first- and second-trimester maternal serum markers and ultrasound screening for aneuploidy

A vanishing twin (VT) is the early demise of a twin fetus. It is estimated to occur in 20-30% of pregnancies associated with assisted reproductive technology. VT becomes increasingly prominent when assisted fertilization is used, because one or more embryos are transferred to the uterus. Maternal serum screening tests during pregnancy can screen for trisomy chromosomes 21, 18, and 13 and are divided into first- and second-trimester tests. In singleton pregnancies, the first trimester screening test is performed at 11-13 weeks and 6 days of gestation. It consists of two serum markers, pregnancy-associated plasma protein A and β-human chorionic gonadotropin (β-hCG), and measures nuchal translucency thickness. The second-trimester screening test was performed at 15-20 weeks and 6 days of gestation. It consists of four serum markers: alpha-fetoprotein, β-hCG, unconjugated estriol, and inhibin A. More effective screening for trisomy 21 in singleton pregnancies is achieved by analyzing cell-free DNA in the maternal blood. A VT includes a demise of the fetus. Although it affects maternal serum markers, it has not been corrected. Five studies examined the effect of VT on maternal serum markers, but the results were controversial. This study aimed to review the patterns of changes in maternal serum markers in VTs, interpret prenatal tests for pregnant women with VTs in clinical practice, and consider what information should be provided.

First trimester low maternal serum pregnancy associated plasma protein-A (PAPP-A) as a screening method for adverse pregnancy outcomes

OBJECTIVES

To evaluate different cut-off values of first trimester pregnancy associated plasma protein-A (PAPP-A) in screening for adverse pregnancy outcomes in a retrospective cohort study.

METHODS

During the study period of 1.1.2014-31.12.2018, total of 23,482 women with singleton pregnancies participated in first trimester combined screening for chromosomal abnormalities. Maternal serum PAPP-A multiple of medians (MoM) levels were measured, and study population was divided into three study groups of PAPP-A ≤0.40 (n=1,030), ≤0.35 (n=630) and ≤0.30 (n=363) MoM.

RESULTS

Small for gestational age (SGA), preterm birth (PTB) and composite outcome (SGA, hypertensive disorder of pregnancy (HDP) and/or PTB) were more frequent in all three PAPP-A MoM study groups and pre-eclampsia in ≤0.40 and ≤0.35 study groups than in their control groups (p < 0.05). The odds ratio (OR) for SGA varied from 3.7 to 5.4 and sensitivity and specificity from 6.9 to 13.8% and from 95.9 to 98.6%, between study groups. Using PAPP-A ≤0.30 MoM as a screening cut-off instead of PAPP-A ≤0.40 MoM, resulted in approximately 50% reduction in screening detection of SGA and PTB.

CONCLUSIONS

PAPP-A ≤0.40 MoM should be considered as a primary screening cut-off for adverse pregnancy outcomes as approximately 23% will develop either SGA, HDP or PTB. It seems to be the best cut-off to screen for SGA.

Emerging Protein Biomarkers for the Diagnosis or Prediction of Gestational Diabetes-A Scoping Review

Introduction: Gestational diabetes (GDM), defined as hyperglycemia with onset or initial recognition during pregnancy, has a rising prevalence paralleling the rise in type 2 diabetes (T2DM) and obesity. GDM is associated with short-term and long-term consequences for both mother and child. Therefore, it is crucial we efficiently identify all cases and initiate early treatment, reducing fetal exposure to hyperglycemia and reducing GDM-related adverse pregnancy outcomes. For this reason, GDM screening is recommended as part of routine pregnancy care. The current screening method, the oral glucose tolerance test (OGTT), is a lengthy, cumbersome and inconvenient test with poor reproducibility. Newer biomarkers that do not necessitate a fasting sample are needed for the prompt diagnosis of GDM. The aim of this scoping review is to highlight and describe emerging protein biomarkers that fulfill these requirements for the diagnosis of GDM. Materials and Methods: This scoping review was conducted according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines for scoping reviews using Cochrane Central Register of Controlled Trials (CENTRAL), the Cumulative Index to Nursing & Allied Health Literature (CINAHL), PubMed, Embase and Web of Science with a double screening and extraction process. The search included all articles published in the literature to July 2020. Results: Of the 3519 original database citations identified, 385 were eligible for full-text review. Of these, 332 (86.2%) were included in the scoping review providing a total of 589 biomarkers studied in relation to GDM diagnosis. Given the high number of biomarkers identified, three post hoc criteria were introduced to reduce the items set for discussion: we chose only protein biomarkers with at least five citations in the articles identified by our search and published in the years 2017-2020. When applied, these criteria identified a total of 15 biomarkers, which went forward for review and discussion. Conclusions: This review details protein biomarkers that have been studied to find a suitable test for GDM diagnosis with the potential to replace the OGTT used in current GDM screening protocols. Ongoing research efforts will continue to identify more accurate and practical biomarkers to take GDM screening and diagnosis into the 21st century.

Pregnancy-Associated Plasma Protein-A (PAPP-A) in Ewing Sarcoma: Role in Tumor Growth and Immune Evasion

BACKGROUND

Ewing sarcoma (EWS) manifests one of the lowest somatic mutation rates of any cancer, leading to a scarcity of druggable mutations and neoantigens. Immunotherapeutics targeting differentially expressed cell surface antigens could provide therapeutic benefit for such tumors. Pregnancy-associated plasma protein A (PAPP-A) is a cell membrane-associated proteinase produced by the placenta that promotes fetal growth by inducing insulinlike growth factor (IGF) signaling.

METHODS

By comparing RNA expression of cell surface proteins in EWS (n = 120) versus normal tissues (n = 42), we comprehensively characterized the surfaceome of EWS to identify highly differentially expressed molecules. Using CRISPR/Cas-9 and anti-PAPP-A antibodies, we investigated biological roles for PAPP-A in EWS in vitro and in vivo in NSG xenograft models and performed RNA-sequencing on PAPPA knockout clones (n = 5) and controls (n = 3). All statistical tests were two-sided.

RESULTS

EWS surfaceome analysis identified 11 highly differentially overexpressed genes, with PAPPA ranking second in differential expression. In EWS cell lines, genetic knockout of PAPPA and treatment with anti-PAPP-A antibodies revealed an essential survival role by regulating local IGF-1 bioavailability. MAb-mediated PAPPA inhibition diminished EWS growth in orthotopic xenografts (leg area mm2 at day 49 IgG2a control (CTRL) [n = 14], mean = 397.0, SD = 86.1 vs anti-PAPP-A [n = 14], mean = 311.7, SD = 155.0; P = .03; median OS anti-PAPP-A = 52.5 days, 95% CI = 46.0 to 63.0 days vs IgG2a = 45.0 days, 95% CI = 42.0 to 52.0 days; P = .02) and improved the efficacy of anti-IGF-1R treatment (leg area mm2 at day 49 anti-PAPP-A + anti-IGF-1R [n = 15], mean = 217.9, SD = 148.5 vs IgG2a-CTRL; P < .001; median OS anti-PAPP-A + anti-IGF1R = 63.0 days, 95% CI = 52.0 to 67.0 days vs IgG2a-CTRL; P < .001). Unexpectedly, PAPPA knockout in EWS cell lines induced interferon (IFN)-response genes, including proteins associated with antigen processing/presentation. Consistently, gene expression profiles in PAPPA-low EWS tumors were enriched for immune response pathways.

CONCLUSION

This work provides a comprehensive characterization of the surfaceome of EWS, credentials PAPP-A as a highly differentially expressed therapeutic target, and discovers a novel link between IGF-1 signaling and immune evasion in cancer, thus implicating shared mechanisms of immune evasion between EWS and the placenta.

Placental production of progestins is fully effective in villous cytotrophoblasts and increases with the syncytiotrophoblast formation

Placental syncytiotrophoblast (ST) is considered as the main placental endocrine tissue secreting progesterone, a steroid essential for maintenance of pregnancy. However, each step of progestins production has been poorly investigated in villous cytotrophoblast (VCT) regarding ST formation. We aimed to characterize progestins production during human differentiation of VCT into ST. VCTs were isolated from term placenta and cultivated, with or without forskolin (FSK), to stimulate trophoblast differentiation. Secreted progestins concentrations were determined by immuno-assay and Gas Chromatography-tandem mass spectrometry. Intracellular expression of cholesterol transporter and enzymes involved in steroidogenesis were studied by immunofluorescence, western-blot, and RT-qPCR. Progesterone and pregnenolone are produced by VCT and their secretion increases with VCT differentiation while 17-hydroxyprogesterone concentration remains undetectable. HSD3B1 enzyme expression increases whereas MLN64, the cholesterol placental mitochondrial transporter and P450SCC expressions do not. FSK induces progestins production. Progestins placental synthesis is effective since VCT and increases with ST formation thanks to mitochondria.

Spontaneous and in vitro fertilization pregnancies have comparable first trimester screening profiles for Down syndrome

Objective

We aimed to compare the first trimester screening profiles of spontaneous (n=972) and in in vitro fertilization (IVF) pregnancies (n=339) in a population of patients who had uncomplicated singleton pregnancies comparable for maternal age, gestation, body mass index, and ethnicity.

Material and Methods

A non-interventional analysis of retrospective cohort data and review of the literature.

Results

All IVF pregnancies were achieved via intracytoplasmic sperm injection using the same ovarian stimulation protocol with recombinant follicle-stimulating hormone and a gonadotropin-releasing hormone antagonist, cetrorelix acetate. The means of the multiple of median (MoM) of pregnancy-associated plasma protein-A (PAPP-A) were slightly lower in the fresh (1.19±0.6 vs 1.33±0.7, respectively; p=0.056) and frozen embryo transfer (1.03±0.5 vs 1.33±0.7, respectively; p=0.036) IVF pregnancies compared with natural conceptions. However, when the medians of the MoMs of PAPP-A and beta-human chorionic gonadotrophin (β-hCG), and their distributions were compared across the mode of conception, there were no differences between IVF pregnancies spontaneous pregnancies. Furthermore, the scatterplot diagram and curve fitting regression analyses revealed no difference in the temporal relations of β-hCG and PAPP-A with each other and gestational age between spontaneous and IVF pregnancies.

Conclusion

These results support the notion that uncomplicated singleton IVF pregnancies have similar first trimester screening profiles to spontaneous conceptions.

Study of Human T21 Placenta Suggests a Potential Role of Mesenchymal Spondin-2 in Placental Vascular Development

Placental development is particularly altered in trisomy of chromosome 21 (T21)-affected pregnancies. We previously described in T21-affected placentae an abnormal paracrine crosstalk between the villus mesenchymal core and villus trophoblasts. T21-affected placentae are known to be characterized by their hypovascularity. However, the causes of this anomaly remain not fully elucidated. Therefore, the hypothesis of an abnormal paracrine crosstalk between fetal mesenchymal core and placental endothelial cells (PLECs) was evocated. Villus mesenchymal cells from control (CMCs) and T21 placentae (T21MCs) were isolated and grown in culture to allow their characterization and collection of conditioned media for functional analyses (CMC-CM and T21MC-CM, respectively). Interestingly, PLEC proliferation and branching ability were less stimulated by T21MC-CM than by CMC-CM. Protein array analysis identified secreted proangiogenic growth factors in CMC-CM, which were reduced in T21MC-CM. Combined mass spectrometry and biochemical analysis identified spondin-2 as a factor decreased in T21MC-CM compared with CMC-CM. We found that exogenous spondin-2 stimulated PLEC proliferation and established that T21MC-CM supplemented with spondin-2 recovered conditioned media ability to induce PLEC proliferation and angiogenesis. Hence, this study demonstrates a crosstalk between villus mesenchymal and fetal endothelial cells, in which spondin-2 secreted from mesenchymal cells plays a central role in placental vascular functions. Furthermore, our results also suggest that a reduction in spondin-2 secretion may contribute to the pathogenesis of T21 placental hypovascularity.

The human placental proteome secreted into the maternal and fetal circulations in normal pregnancy based on 4-vessel sampling

We sought to identify proteins secreted by the human placenta into the maternal and fetal circulations. Blood samples from the maternal radial artery and uterine vein and umbilical artery and vein were obtained during cesarean section in 35 healthy women with term pregnancy. Slow off-rate modified aptamer (SOMA) protein-binding technology was used to quantify 1310 known proteins. The uteroplacental and umbilical venoarterial concentration differences were calculated. Thirty-four proteins were significantly secreted by the placenta into the maternal circulation, including placental growth factor, growth/differentiation factor 15, and matrix metalloproteinase 12. There were 341 proteins significantly secreted by the placenta into the fetal circulation. Only 7 proteins were secreted into both the fetal and maternal circulations, suggesting a distinct directionality in placental protein release. We examined changes across gestation in the proteins found to be significantly secreted by the placenta into the maternal circulation using serial blood samples from healthy women. Among the 34 proteins secreted into the maternal circulation, 8 changed significantly across gestation. The identified profiles of secreted placental proteins will allow us to identify novel minimally invasive biomarkers for human placental function across gestation and discover previously unknown proteins secreted by the human placenta that regulate maternal physiology and fetal development.-Michelsen, T. M., Henriksen, T., Reinhold, D., Powell, T. L., Jansson, T. The human placental proteome secreted into the maternal and fetal circulations in normal pregnancy based on 4-vessel sampling.

Correlation of Pregnancy Associated Plasma Protein A and Zinc with Calculated Risk Ratio of Dual Test

INTRODUCTION

First trimester screening by dual test is the most preferred method of antenatal screening. The detection rate of foetal aneuploidy using dual test is 95%. This test uses maternal serum free β human Chorionic Gonadotropin (free β hCG) and Pregnancy Associated Plasma Protein A (PAPP-A) along with maternal demographic and foetal sonographic indices to calculate risk for foetal aneuploidy. PAPP-A is a zinc binding metalloproteinase which is also responsible for placental development and foetal growth. So, zinc might also have some role in first trimester screening. No studies are available substantiating the role of zinc in first trimester screening.

AIM

To measure and correlate maternal serum zinc with PAPP-A and calculated risk ratio of first trimester screening.

MATERIALS AND METHODS

PAPP-A and zinc were measured from the serum of 84 pregnant women aged 20-40 years in 11th-13th weeks+6 days of gestation who underwent dual test during their antenatal check-up. Risk calculation was done using Screening Software for Downs Windows Lab (SSDWL).

RESULTS

Maternal serum PAPP-A showed a significant positive correlation with maternal serum zinc (p-value <0.001). Maternal serum PAPP-A and zinc both showed a significant positive correlation with calculated risk ratio (p-value<0.01).

CONCLUSION

As PAPP-A is a zinc binding metalloproteinase, zinc showed significant pattern of correlation with aneuploidy risk as shown by PAPP-A. So there could be a possible role for serum zinc in first trimester of screening.

Transcriptome profile of the human placenta

The human placenta is a particular organ that inseparably binds the mother and the fetus. The proper development and survival of the conceptus relies on the essential interplay between maternal and fetal factors involved in cooperation within the placenta. In our study, high-throughput sequencing (RNA-seq) was applied to analyze the global transcriptome of the human placenta during uncomplicated pregnancies. The RNA-seq was utilized to identify the global pattern of the gene expression in placentas (N = 4) from women in single and twin pregnancies. During analyses, we obtained 228,044 transcripts. More than 91% of them were multi-exon, and among them 134 were potentially unknown protein coding genes. Expression levels (FPKM) were estimated for 38,948 transcriptional active regions, and more than 3000 of genes were expressed with FPKM >20 in each sample. Additionally, all unannotated transcripts with estimated FPKM values were localized on the human genome. Highly covered splice junctions unannotated in the human genome (6497) were identified, and among them 30 were novel. To gain a better understanding of the biological implications, the assembled transcripts were annotated with gene ontology (GO) terms. Single nucleotide variants were predicted for the transcripts assigned to each analyzed GO category. Our results may be useful for establishing a general pattern of the gene expression in the human placenta. Characterizing placental transcriptome, which is crucial for a pregnancy’s outcome, can serve as a basis for identifying the mechanisms underlying physiological pregnancy, as well as may be useful for an early detection of the genomic defects.

The endocrine function of human placenta: an overview

During pregnancy, several tightly coordinated and regulated processes take place to enable proper fetal development and gestational success. The formation and development of the placenta is one of these critical pregnancy events. This organ plays essential roles during gestation, including fetal nourishment, support and protection, gas exchange and production of several hormones and other mediators. Placental hormones are mainly secreted by the syncytiotrophoblast, in a highly and tightly regulated way. These hormones are important for pregnancy establishment and maintenance, exerting autocrine and paracrine effects that regulate decidualization, placental development, angiogenesis, endometrial receptivity, embryo implantation, immunotolerance and fetal development. In addition, because they are released into maternal circulation, the profile of their blood levels throughout pregnancy has been the target of intense research towards finding potential robust and reliable biomarkers to predict and diagnose pregnancy-associated complications. In fact, altered levels of these hormones have been associated with some pathologies, such as chromosomal anomalies or pre-eclampsia. This review proposes to revise and update the main pregnancy-related hormones, addressing their major characteristics, molecular targets, function throughout pregnancy, regulators of their expression and their potential clinical interest.