Discordant secretion of pregnancy specific beta 1-glycoprotein and human chorionic gonadotropin by human pre-embryos cultured in vitro

An Early Gestation Plasma Inflammasome in Rural Bangladeshi Women

Circulating α1-acid glycoprotein (AGP) and C-reactive protein (CRP) are commonly measured to assess inflammation, but these biomarkers fail to reveal the complex molecular biology of inflammation. We mined the maternal plasma proteome to detect proteins that covary with AGP and CRP. In 435 gravida predominantly in <12-week gestation, we correlated the relative quantification of plasma proteins assessed via a multiplexed aptamer assay (SOMAScan®) with AGP and CRP, quantified by immunoassay. We defined a plasma inflammasome as protein correlates meeting a false discovery rate <0.05. We examined potential pathways using principal component analysis. A total of 147 and 879 of 6431 detected plasma proteins correlated with AGP and CRP, respectively, of which 61 overlapped with both biomarkers. Positive correlates included serum amyloid, complement, interferon-induced, and immunoregulatory proteins. Negative correlates were micronutrient and lipid transporters and pregnancy-related anabolic proteins. The principal components (PCs) of AGP were dominated by negatively correlated anabolic proteins associated with gestational homeostasis, angiogenesis, and neurogenesis. The PCs of CRP were more diverse in function, reflecting cell surface and adhesion, embryogenic, and intracellular and extra-hepatic tissue leakage proteins. The plasma proteome of AGP or CRP reveals wide proteomic variation associated with early gestational inflammation, suggesting mechanisms and pathways that merit future research.

Pro-angiogenic effects of pregnancy-specific glycoproteins in endothelial and extravillous trophoblast cells

We previously reported that binding to heparan sulfate (HS) is required for the ability of the placentally secreted pregnancy-specific glycoprotein 1 (PSG1) to induce endothelial tubulogenesis. PSG1 is composed of four immunoglobulin-like domains but which domains of the protein bind to HS remains unknown. To analyze the interaction of PSG1 with HS, we generated several recombinant proteins, including the individual domains, chimeric proteins between two PSG1 domains, and mutants. Using flow cytometric and surface plasmon resonance studies, we determined that the B2 domain of PSG1 binds to HS and that the positively charged amino acids encompassed between amino acids 43-59 are required for this interaction. Furthermore, we showed that the B2 domain of PSG1 is required for the increase in the formation of tubes by endothelial cells (EC) including a human endometrial EC line and two extravillous trophoblast (EVT) cell lines and for the pro-angiogenic activity of PSG1 observed in an aortic ring assay. PSG1 enhanced the migration of ECs while it increased the expression of matrix metalloproteinase-2 in EVTs, indicating that the pro-angiogenic effect of PSG1 on these two cell types may be mediated by different mechanisms. Despite differences in amino acid sequence, we observed that all human PSGs bound to HS proteoglycans and confirmed that at least two other members of the family, PSG6 and PSG9, induce tube formation. These findings contribute to a better understanding of the pro-angiogenic activity of human PSGs and strongly suggest conservation of this function among all PSG family members.

Quantitative proteomic analysis of down syndrome biomarkers in maternal serum using isobaric tags for relative and absolute quantification (iTRAQ)

Prenatal diagnosis of Down syndrome (DS) is based on calculated risk involving maternal age, biochemical and ultrasonographic markers, and, more recently, cell-free DNA (cfDNA). The present study was designed to identify Down Syndrome biomarkers in maternal serum. We quantified the changes in maternal serum protein levels between 10 non-pregnant women, 10 pregnant women with healthy fetuses, and 10 pregnant women with DS fetuses using isobaric tags for relative and absolute quantification (iTRAQ). We subsequently conducted a Gene Ontology (GO) analysis. A total of 470 proteins were identified, 11 of which had significantly different serum levels between the DS fetus group and Healthy fetuses group. Our data shows the identified proteins may be relevant to DS and constitute potential DS biomarkers.

Comparison of serum human pregnancy-specific beta-1-glycoprotein 1 levels in pregnant women with or without preeclampsia

The aim of this study was to investigate the relationship between the maternal serum levels of pregnancy-specific beta-1-glycoprotein 1 (PSG1) and preeclampsia, and to compare levels of PSG1 in pregnancies with preeclampsia and uneventful pregnancies. A case-control study was conducted in a research and training hospital. A total of 40 women with preeclampsia and 42 healthy pregnant women who were gestational age-matched were included. Serum PSG1 levels were measured using enzyme-linked immunosorbent assay. The maternal serum PSG1 levels were significantly lower in patients with preeclampsia compared with controls (11.60 ± 8.08 vs. 17.58 ± 9.72 ng/mL, p = .003). Circulating PSG1 levels were negatively correlated with age in the preeclampsia and control groups (r = -0.322, p = .043), (r = -0.430, p = .005). PSG1 levels, age, blood urea nitrogen levels and birth weight were significantly associated with high odds of having preeclampsia. Receiver operating characteristic (ROC) curve analysis confirmed that the area under ROC curve was 0.707 (95% CI: [0.595-0.819], p < .001) for PSG1. The optimal cut-off value of PSG1 for detecting preeclampsia was ≤ 11.80 ng/mL. There may be a decrease in PSG1 production in preeclampsia-complicated pregnancies where there are pathologies related to placenta formation. A decline in PSG1 concentrations may reflect placental dysfunction.Impact StatementWhat is already known on this subject? Previous studies have reported abnormal pregnancy-specific glycoprotein (PSG) levels in complicated pregnancies and demonstrated their importance in maintaining a healthy pregnancy. Human PSG homologues have been identified in species with haemochorial placentation such as non-human primates, rats and mice, where foetal cells are in direct contact with the maternal circulation. There are studies in which there is no clear relationship between PSGs and preeclampsia.What the results of this study add? We have demonstrated that circulating PSG1 levels were significantly lower in women with preeclampsia than in healthy pregnant women. There may be a decrease in PSG1 production in preeclampsia-complicated pregnancies where there are pathologies related to placenta formation and function. The results obtained from this current study could be used to clarify the relationship between PSG1 levels and preeclampsia.What the implications are for clinical practice and/or further research? Evaluation of the role of circulating PSG1 levels in preeclampsia would be helpful in order to design further studies to determine the feasibility of using PSG1 as a serum marker to predict the risk of developing preeclampsia. The screening performance of PSG1 for preeclampsia is not yet clinically relevant, but may become so when evaluated together with other placental proteins. This will give a lead to further researches which could focus on the early detection of preeclampsia with the combination of several serum markers.

iTRAQ and PRM-based quantitative proteomics in early recurrent spontaneous abortion: biomarkers discovery

Background

Early recurrent spontaneous abortion (ERSA) is a common condition in pregnant women. To prevent ERSA is necessary to look for abortion indicators, such as hormones and proteins, in an early stage.

Methods

Thirty patients with ERSA were enrolled in the case group. In the control group, we recruited 30 healthy women without a history of miscarriage undergoing voluntary pregnancy termination. The differentially expressed proteins in the serum were identified between the two groups using PRM and iTRAQ.

Results

Seventy-eight differentially expressed proteins were identified. Using GO functional annotation and KEGG pathway analysis, we detected that the most significant changes occurred in the pathway of Fc gamma R-mediated phagocytosis. Meanwhile, using PRM, we identified three proteins that were closely related to abortion, B4DTF1 (highly similar to PSG1), P11464 (PSG1), and B4DF70 (highly similar to Prdx-2). The levels of B4DTF1 and P11464 were down-regulated, while the level of B4DF70 was up-regulated.

Conclusions

CD45, PSG1, and Prdx-2, were significantly dysregulated in the samples of ERSA and could become important biomarkers for the prediction and diagnosis of ERSA. Larger‑scale studies are required to confirm the diagnostic value of these biomarkers.

Soluble ligands and their receptors in human embryo development and implantation

Extensive evidence suggests that soluble ligands and their receptors mediate human preimplantation embryo development and implantation. Progress in this complex area has been ongoing since the 1980s, with an ever-increasing list of candidates. This article specifically reviews evidence of soluble ligands and their receptors in the human preimplantation stage embryo and female reproductive tract. The focus will be on candidates produced by the human preimplantation embryo and those eliciting developmental responses in vitro, as well as endometrial factors related to implantation and receptivity. Pathways to clinical translation, including innovative diagnostics and other technologies, are also highlighted, drawing from this collective evidence toward facilitating joint improvements in embryo quality and endometrial receptivity. This strategy could not only benefit clinical outcomes in reproductive medicine but also provide broader insights into the peri-implantation period of human development to improve fetal and neonatal health.

Human chorionic gonadotropin (hCG) in the secretome of cultured embryos: hyperglycosylated hCG and hCG-free beta subunit are potential markers for infertility management and treatment

Human chorionic gonadotropin (hCG) is produced by trophoblast cells throughout pregnancy, and gene expression studies have indicated that hCG-beta subunit (hCGβ) expression is active at the 2 blastomere stage. Here, we investigated the qualitative hCG output of developing embryos in culture and hCG isoforms expressed in the secretome as a novel sensitive method for detecting hCG. Culture media was collected from the culture plates of 118 embryos in culture (including controls and embryos at different stages of culture) from 16 patients undergoing routine fertility treatment. The hCGβ was detectable in media from 2 pronuclear (2PN) stage embryos through to the blastocyst stage. The hCGβ was absent in 1PN and arrested embryos as well as all media controls. Prior to hatching, hyperglycosylated hCG (hCGh) was observed selectively in 3PN embryos, but after hatching, along with hCG, became the dominant hCG molecule observed. We have reported at the 2PN stage the earliest evidence of hCGβ expression in embryos. There is a suggestion this may be indicative of quality in early embryos, and hCGh seen at the pronuclear stage may suggest triploid abnormality. The dominance of hCG, and hCGh expression, seen after blastocyst hatching may be indicative of potential implantation success. Thus, hCG isoforms have potential roles as biomarkers of embryo viability for embryo/blastocyst transfer.

Early expression of pregnancy-specific glycoprotein 22 (PSG22) by trophoblast cells modulates angiogenesis in mice

Mouse and human pregnancy-specific glycoproteins (PSG) are known to exert immunomodulatory functions during pregnancy by inducing maternal leukocytes to secrete anti-inflammatory cytokines that promote a tolerogenic decidual microenvironment. Many such anti-inflammatory mediators also function as proangiogenic factors, which, along with the reported association of murine PSG with the uterine vasculature, suggest that PSG may contribute to the vascular adaptations necessary for successful implantation and placental development. We observed that PSG22 is strongly expressed around the embryonic crypt on Gestation Day 5.5, indicating that trophoblast giant cells are the main source of PSG22 during the early stages of pregnancy. PSG22 treatment up-regulated the secretion of transforming growth factor beta 1 and vascular endothelial growth factor A (VEGFA) in murine macrophages, uterine dendritic cells, and natural killer cells. A possible role of PSGs in uteroplacental angiogenesis is further supported by the finding that incubation of endothelial cells with PSG22 resulted in the formation of tubes in the presence and absence of VEGFA. We determined that PSG22, like human PSG1 and murine PSG17 and PSG23, binds to the heparan sulfate chains in syndecans. Therefore, our findings indicate that despite the independent evolution and expansion of human and rodent PSG, members in both families have conserved functions that include their ability to induce anti-inflammatory cytokines and proangiogenic factors as well as to induce the formation of capillary structures by endothelial cells. In summary, our results indicate that PSG22, the most abundant PSG expressed during mouse early pregnancy, is likely a major contributor to the establishment of a successful pregnancy.

Human pregnancy specific beta-1-glycoprotein 1 (PSG1) has a potential role in placental vascular morphogenesis

Previous studies suggest that human pregnancy specific beta-1-glycoproteins (PSGs) play immunomodulatory roles during pregnancy; however, other possible functions of PSGs have yet to be explored. We have observed that PSGs induce transforming growth factor beta 1 (TGFB1), which among its other diverse functions inhibits T-cell function and has proangiogenic properties. The present study investigates a potential role for PSG1, the most abundant PSG in maternal serum, as a possible inducer of proangiogenic growth factors known to play an important role in establishment of the vasculature at the maternal-fetal interface. To this end, we measured TGFB1, vascular endothelial growth factors (VEGFs) A and C, and placental growth factor (PGF) protein levels in several cell types after PSG1 treatment. In addition, tube formation and wound healing assays were performed to investigate a possible direct interaction between PSG1 and endothelial cells. PSG1 induced up-regulation of both TGFB1 and VEGFA in human monocytes, macrophages, and two human extravillous trophoblast cell lines. We did not observe induction of VEGFC or PGF by PSG1 in any of the cells tested. PSG1 treatment resulted in endothelial tube formation in the presence and absence of VEGFA. Site-directed mutagenesis was performed to map the essential regions within the N-domain of PSG1 required for functional activity. We found that the aspartic acid at position 95, previously believed to be required for binding of PSGs to cells, is not required for PSG1 activity but that the amino acids implicated in the formation of a salt bridge within the N-domain are essential for PSG1 function.

Implantation-dependent expression of trophinin by maternal fallopian tube epithelia during tubal pregnancies: possible role of human chorionic gonadotrophin on ectopic pregnancy

Trophinin, tastin, and bystin have been identified as molecules potentially involved in human embryo implantation. Both trophoblasts and endometrial epithelial cells express trophinin, which mediates apical cell adhesion through homophilic trophinin-trophinin binding. We hypothesized that trophinin's function in embryo implantation is unique to humans and investigated the expression of trophinin, tastin, and bystin in ectopic pregnancy, a condition unique to humans. In tubal pregnancies, high levels of all three were found in both trophoblasts and fallopian tubal epithelia. Trophinin expression in maternal cells was particularly high in the area adjacent to the trophoblasts, whereas trophinin was barely detectable in intact fallopian tubes from women with in utero pregnancies or without pregnancies. When explants of intact fallopian tube were incubated with the human chorionic gonadotrophin (hCG), trophinin expression was enhanced in epithelial cells. Since the trophectoderm of the human blastocyst secretes hCG before and after implantation, these results suggest that hCG from the human embryo induces trophinin expression by maternal cells. As both beta-subunit of hCG and trophinin genes have diverged in mammals, the present study suggests a unique role of hCG and trophinin in human embryo implantation, including the pathogenesis of ectopic pregnancy.

Variability in the expression of trophectodermal markers beta-human chorionic gonadotrophin, human leukocyte antigen-G and pregnancy specific beta-1 glycoprotein by the human blastocyst

Improved culture conditions that support the development of human embryos to the blastocyst stage in vitro led to the prospect of blastocyst transfer to increase pregnancy rates. Thus, there is a need for characterization of possible biochemical markers able to predict the implantation potential of human blastocysts. In this study, the expression of three placental markers that are expressed prior to implantation, beta-human chorionic gonadotrophin (HCG), human leukocyte antigen (HLA)-G and pregnancy specific beta-1 glycoprotein (SP-1), was investigated. beta-HCG transcript could be detected as early as the two-cell stage, which is one to two cleavage divisions earlier than previously reported. Both beta-HCG and HLA-G transcripts could be detected in the majority of blastocysts, but their levels were highly variable. No association could be found between the amount of transcript for these genes, total cell number or cell death rate. Interestingly, there was a highly positive correlation between accumulation of beta-HCG and HLA-G transcripts. SP-1 protein concentrations were assessed in the culture medium of blastocysts using enzyme-linked immunosorbent assay. There was a significant positive correlation between SP-1 concentrations and blastocyst cell numbers. Moreover, synthetic oviductal medium enriched with potassium resulted in an SP-1 concentration twice as high as that observed using human tubal fluid medium. These data suggest that SP-1 may be used to select blastocysts with higher cell number, possibly resulting in higher pregnancy rates.

Pregnancy-specific glycoprotein gene expression in recurrent aborters: a potential correlation to interleukin-10 expression

PROBLEM

The expression of the pregnancy-specific glycoprotein (PSG) genes in the uterine endometrium of women experiencing recurrent first-trimester abortions, and potential correlations to cytokine expression were examined.

METHOD OF STUDY

Endometrial RNA, isolated from women with a history of either repetitive first-trimester pregnancy losses or uncomplicated pregnancies, was isolated and analyzed for PSG transcripts by the reverse transcriptase-polymerase chain reaction method. PSG genes showing different patterns of expression were expressed in baculovirus, and the purified proteins examined for their effects on cytokine expression.

RESULTS

The expression of PSG11 in the endometria of recurrent aborters was significantly lower than in that of controls (P < 0.01). When tested on monocytes, PSG11 stimulated secretion of interleukin (IL)-10.

CONCLUSIONS

The level of expression of the PSG11 gene in the uterine endometrium, during the peri-implantation period, correlates with the risk of pregnancy loss in some women experiencing recurrent spontaneous abortions. The ability of PSG11 to influence the secretion of IL-10 suggests that PSG11 may contribute to the local modulation of the inflammatory T helper-1 response seen in the endometrium of these women.

Highly specific monoclonal antibody demonstrates that pregnancy-specific glycoprotein (PSG) is limited to syncytiotrophoblast in human early and term placenta

Pregnancy specific glycoproteins (PSG) in humans constitute a family of 11 closely related glycoproteins (PSG1-8, PSG11-13) of unknown function(s), which are produced in large amounts by the placenta. As a step toward understanding the biology of PSG, specific monoclonal antibodies (mAbs) against PSG were developed and used to investigate the ultrastructural localization of PSG in the early and term placenta and in first trimester decidua. One mAb, BAP-3, was found to react with all six individually expressed PSGs representing five alternatively spliced forms, but not with any of the seven expressed members of the carcinoembryonic antigen (CEA) subfamily. The BAP-3 epitope is located in the PSG B2 domain. Using the BAP-3 mAb, PSGs were found to be expressed exclusively by the syncytiotrophoblast of first trimester and term villi. The intensity of the staining was much higher in early than in term placenta. All three main cellular compartments involved in the biosynthesis pathway of secreted proteins, i.e. rough endoplasmic reticulum, the Golgi complex and secretory vesicles, were stained for PSG. A second PSG-reactive mAb, BAP-1, also stained the apical plasma membrane of some glandular epithelial cells in first trimester decidua in addition to syncytiotrophoblast. This staining was most likely due to cross-reactivity with biliary glycoprotein (BGP).

Schwangerschaftsprotein 1 (SP1) as a maternal serum marker for Down syndrome in the first and second trimesters

The potential of the maternal serum concentration of schwangerschaftsprotein 1 (MSSP1) as a marker for Down syndrome (DS) pregnancies was evaluated in the fifth to the 20th gestational week using 156 DS pregnancies and 546 unaffected control pregnancies. In DS pregnancies, the median of the multiple of the median (MOM) of MSSP1 was 0.27 [95 per cent confidence interval (CI) 0.11-0.59] in weeks 5-9 (n = 25) and 1.28 (CI 1.11-1.49) in weeks 14-20 (n = 117), significantly different from controls (P < 10(-6). In weeks 10-12, the median MSSP1 MOM was 0.89 (CI 0.20-2.09) (n = 14), not different from controls (P = 0.42). Using MSSP1 alone as a marker for DS gave--in empirical receiver-operator-characteristics (ROC) analysis--a detection rate of about 44 percent for a false-positive rate of about 5 per cent in weeks 5-9 (using MSSP1 MOM < or = cut-off), whereas a sensitivity of about 20 percent was found for a false-positive rate of 5 percent in weeks 14-20 (using MSSP1 MOM > or = cut-off). In parameterized ROC analysis, the detection rates were 38 and 18 percent for a false-positive rate of 5 per cent in weeks 5-9 and 14-20, respectively.

Three-dimensional structures of gonadotropins

Most secreted proteins are modified post-translationally with the addition of carbohydrate. It has been difficult to use crystallography to solve the structures of these proteins due to the inherent heterogeneity of the carbohydrate. The structure of the chemically deglycosylated form (hydrogen fluoride treated) of human chorionic gonadotropin (hCG) has been solved through crystallographic techniques. Unfortunately this form of hCG is not biologically active, and exhibits immunochemical differences from native hormone. In addition, subunit interactions appear altered after chemical deglycosylation as indicated by the increased thermal stability of the HF-treated hormone. The Asn 52 glycan on the alpha-subunit of hCG has been identified as being required for biological activity, it is, therefore, of physiological importance to determine the structure of the hormone with its carbohydrate intact. Also, it has not been possible to obtain crystals of the individual glycosylated subunits of hCG. Therefore an alternative method to solve the structure of the biologically active form of the hormone in solution as well as its separated subunits is necessary. Structural information utilizing NMR techniques can be obtained from native hCG subunits in solution if they can be uniformly labeled with 13C and 15N isotopes. We have developed a universal nonradioactive isotope, labeling medium enriched in 13C and 15N which can be used to express uniformly labeled hCG from Chinese hamster ovary cells suitable for solving the structure of the individual subunits and ultimately that of the native, biologically active hormone. The isotopically labeled recombinant hCG and its purified subunits are essentially identical to urinary hCG on comparison by biochemical, immunochemical, biological activity and the ability of the isolated subunits to recombine to form a biologically active dimer. Mass spectrometric analysis and preliminary structural NMR data indicate that the labeling is uniform and there is greater than 90% incorporation, sufficient for complete structural determination studies. This labeled growth medium represents a technological advance which will enable the rapid solution of the structures of the other glycoprotein hormones, as well as other glycoproteins which have proven unsuitable for crystallographic study.

Progress in the development of human chorionic gonadotropin antifertility vaccines

Prototype human chorionic gonadotropin (hCG) vaccines have demonstrated the feasibility of effectively eliciting antibodies in women and inhibiting fertility in both humans and nonhuman primates. Also, no serious side-effects due to immunization against self antigens have been revealed to date. However, the formulations so far tested in clinical trials are not suitable for widespread applications due to problems associated with complexities in production, burdensome application procedures, the need for frequent booster immunizations or cost of manufacture. Current research efforts involve the development of delivery systems to permit annual or biannual intervals between immunizations for protection from pregnancy, procedures for mucosal immunizations, methods to reduce hypersensitivity and local reactions, and procedures for reducing the cost of production. Recent progress in understanding the crystalline structure of the hCG molecule has stimulated further studies to define immunological epitope sequences that might constitute immunogens in future vaccines. The incorporation of vaccine components into biodegradable microspheres has resulted in formulations that elicit elevated antibody levels in rabbits for more than one year. Preclinical and clinical studies with such formulations are planned. Studies using totally synthetic peptide immunogens constituting hCG B-cell epitopes and "promiscuous" T-cell epitopes from bacterial or viral proteins have been shown to be equally immunogenic as conjugates of hCG peptides with macromolecular carriers. Still other peptide immunogens have been developed that can elicit antibody production without detectable proliferation of helper T cells. Some of these peptides can induce systemic immunity from oral immunization or systemic injections. Alternative vehicles for administering vaccine components with reduced local reactivity show promise for new vaccine formulations.