Glycodelin-A protein interacts with Siglec-6 protein to suppress trophoblast invasiveness by down-regulating extracellular signal-regulated kinase (ERK)/c-Jun signaling pathway

Upregulation of Siglec-6 induces mitochondrial dysfunction by promoting GPR20 expression in early-onset preeclampsia

BACKGROUND

Preeclampsia, especially early-onset preeclampsia (EO-PE), is a pregnancy complication that has serious consequences for the health of both the mother and the fetus. Although abnormal placentation due to mitochondrial dysfunction is speculated to contribute to the development of EO-PE, the underlying mechanisms have yet to be fully elucidated.

METHODS

The expression and localization of Siglec-6 in the placenta from normal pregnancies, preterm birth and EO-PE patients were examined by RT-qPCR, Western blot and IHC. Transwell assays were performed to evaluate the effect of Siglec-6 on trophoblast cell migration and invasion. Seahorse experiments were conducted to assess the impact of disrupting Siglec-6 expression on mitochondrial function. Co-IP assay was used to examine the interaction of Siglec-6 with SHP1/SHP2. RNA-seq was employed to investigate the mechanism by which Siglec-6 inhibits mitochondrial function in trophoblast cells.

RESULTS

The expression of Siglec-6 in extravillous trophoblasts is increased in placental tissues from EO-PE patients. Siglec-6 inhibits trophoblast cell migration and invasion and impairs mitochondrial function. Mechanismly, Siglec-6 inhibits the activation of NF-κB by recruiting SHP1/SHP2, leading to increased expression of GPR20. Notably, the importance of GPR20 function downstream of Siglec-6 in trophoblasts is supported by the observation that GPR20 downregulation rescues defects caused by Siglec-6 overexpression. Finally, overexpression of Siglec-6 in the placenta induces a preeclampsia-like phenotype in a pregnant mouse model.

CONCLUSIONS

This study indicates that the regulatory pathway Siglec-6/GPR20 has a crucial role in regulating trophoblast mitochondrial function, and we suggest that Siglec-6 and GPR20 could serve as potential markers and targets for the clinical diagnosis and therapy of EO-PE.

Siglec-6 as a therapeutic target for cell migration and adhesion in chronic lymphocytic leukemia

Siglec-6 is a lectin receptor with restricted expression in the placenta, mast cells and memory B-cells. Although Siglec-6 is expressed in patients with chronic lymphocytic leukemia (CLL), its pathophysiological role has not been elucidated. We describe here a role for Siglec-6 in migration and adhesion of CLL B cells to CLL- bone marrow stromal cells (BMSCs) in vitro and compromised migration to bone marrow and spleen in vivo. Mass spectrometry analysis revealed interaction of Siglec-6 with DOCK8, a guanine nucleotide exchange factor. Stimulation of MEC1-002 CLL cells with a Siglec-6 ligand, sTn, results in Cdc42 activation, WASP protein recruitment and F-actin polymerization, which are all associated with cell migration. Therapeutically, a Siglec-6/CD3-bispecific T-cell-recruiting antibody (T-biAb) improves overall survival in an immunocompetent mouse model and eliminates CLL cells in a patient derived xenograft model. Our findings thus reveal a migratory role for Siglec-6 in CLL, which can be therapeutically targeted using a Siglec-6 specific T-biAb.

Sialic Acid-Siglec-E Interactions Regulate the Response of Neonatal Macrophages to Group B Streptococcus

The mammalian Siglec receptor sialoadhesin (Siglec1, CD169) confers innate immunity against the encapsulated pathogen group B Streptococcus (GBS). Newborn lung macrophages have lower expression levels of sialoadhesin at birth compared with the postnatal period, increasing their susceptibility to GBS infection. In this study, we investigate the mechanisms regulating sialoadhesin expression in the newborn mouse lung. In both neonatal and adult mice, GBS lung infection reduced Siglec1 expression, potentially delaying acquisition of immunity in neonates. Suppression of Siglec1 expression required interactions between sialic acid on the GBS capsule and the inhibitory host receptor Siglec-E. The Siglec1 gene contains multiple STAT binding motifs, which could regulate expression of sialoadhesin downstream of innate immune signals. Although GBS infection reduced STAT1 expression in the lungs of wild-type newborn mice, we observed increased numbers of STAT1+ cells in Siglece-/- lungs. To test if innate immune activation could increase sialoadhesin at birth, we first demonstrated that treatment of neonatal lung macrophages ex vivo with inflammatory activators increased sialoadhesin expression. However, overcoming the low sialoadhesin expression at birth using in vivo prenatal exposures or treatments with inflammatory stimuli were not successful. The suppression of sialoadhesin expression by GBS-Siglec-E engagement may therefore contribute to disease pathogenesis in newborns and represent a challenging but potentially appealing therapeutic opportunity to augment immunity at birth.

The functional roles of protein glycosylation in human maternal-fetal crosstalk

BACKGROUND

The establishment of maternal-fetal crosstalk is vital to a successful pregnancy. Glycosylation is a post-translational modification in which glycans (monosaccharide chains) are attached to an organic molecule. Glycans are involved in many physiological and pathological processes. Human endometrial epithelium, endometrial gland secretions, decidual immune cells, and trophoblasts are highly enriched with glycoconjugates and glycan-binding molecules important for a healthy pregnancy. Aberrant glycosylation in the placenta and uterus has been linked to repeated implantation failure and various pregnancy complications, but there is no recent review summarizing the functional roles of glycosylation at the maternal-fetal interface and their associations with pathological processes.

OBJECTIVE AND RATIONALE

This review aims to summarize recent findings on glycosylation, glycosyltransferases, and glycan-binding receptors at the maternal-fetal interface, and their involvement in regulating the biology and pathological conditions associated with endometrial receptivity, placentation and maternal-fetal immunotolerance. Current knowledge limitations and future insights into the study of glycobiology in reproduction are discussed.

SEARCH METHODS

A comprehensive PubMed search was conducted using the following keywords: glycosylation, glycosyltransferases, glycan-binding proteins, endometrium, trophoblasts, maternal-fetal immunotolerance, siglec, selectin, galectin, repeated implantation failure, early pregnancy loss, recurrent pregnancy loss, preeclampsia, and fetal growth restriction. Relevant reports published between 1980 and 2023 and studies related to these reports were retrieved and reviewed. Only publications written in English were included.

OUTCOMES

The application of ultrasensitive mass spectrometry tools and lectin-based glycan profiling has enabled characterization of glycans present at the maternal-fetal interface and in maternal serum. The endometrial luminal epithelium is covered with highly glycosylated mucin that regulates blastocyst adhesion during implantation. In the placenta, fucose and sialic acid residues are abundantly presented on the villous membrane and are essential for proper placentation and establishment of maternal-fetal immunotolerance. Glycan-binding receptors, including selectins, sialic-acid-binding immunoglobulin-like lectins (siglecs) and galectins, also modulate implantation, trophoblast functions and maternal-fetal immunotolerance. Aberrant glycosylation is associated with repeated implantation failure, early pregnancy loss and various pregnancy complications. The current limitation in the field is that most glycobiological research relies on association studies, with few studies revealing the specific functions of glycans. Technological advancements in analytic, synthetic and functional glycobiology have laid the groundwork for further exploration of glycans in reproductive biology under both physiological and pathological conditions.

WIDER IMPLICATIONS

A deep understanding of the functions of glycan structures would provide insights into the molecular mechanisms underlying their involvement in the physiological and pathological regulation of early pregnancy. Glycans may also potentially serve as novel early predictive markers and therapeutic targets for repeated implantation failure, pregnancy loss, and other pregnancy complications.

Siglecs as potential targets of therapy in human mast cell- and/or eosinophil-associated diseases

Siglecs (sialic acid-binding immunoglobulin-like lectins) are a family of vertebrate glycan-binding cell-surface proteins. The majority mediate cellular inhibitory activity once engaged by specific ligands or ligand-mimicking molecules. As a result, Siglec engagement is now of interest as a strategy to therapeutically dampen unwanted cellular responses. When considering allergic inflammation, human eosinophils and mast cells express overlapping but distinct patterns of Siglecs. For example, Siglec-6 is selectively and prominently expressed on mast cells while Siglec-8 is highly specific for both eosinophils and mast cells. This review will focus on a subset of Siglecs and their various endogenous or synthetic sialoside ligands that regulate eosinophil and mast cell function and survival. It will also summarize how certain Siglecs have become the focus of novel therapies for allergic and other eosinophil- and mast cell-related diseases.

Siglecs family used by pathogens for immune escape may engaged in immune tolerance in pregnancy

The Siglecs family is a group of type I sialic acid-binding immunoglobulin-like receptors that regulate cellular signaling by recognizing sialic acid epitopes. Siglecs are predominantly expressed on the surface of leukocytes, where they play a crucial role in regulating immune activity. Pathogens can exploit inhibitory Siglecs by utilizing their sialic acid components to promote invasion or suppress immune functions, facilitating immune evasion. The establishing of an immune-balanced maternal-fetal interface microenvironment is essential for a successful pregnancy. Dysfunctional immune cells may lead to adverse pregnancy outcomes. Siglecs are important for inducing a phenotypic switch in leukocytes at the maternal-fetal interface toward a less toxic and more tolerant phenotype. Recent discoveries regarding Siglecs in the reproductive system have drawn further attention to their potential roles in reproduction. In this review, we primarily discuss the latest advances in understanding the impact of Siglecs as immune regulators on infections and pregnancy.

The human placenta: new perspectives on its formation and function during early pregnancy

The placenta has evolved to support the development of the embryo and fetus during the different intrauterine periods of life. By necessity, its development must precede that of the embryo. There is now evidence that during embryogenesis and organogenesis, the development of the human placenta is supported by histotrophic nutrition secreted from endometrial glands rather than maternal blood. These secretions provide a plentiful supply of glucose, lipids, glycoproteins and growth factors that stimulate rapid proliferation and differentiation of the villous trophoblast. Furthermore, evidence from endometrial gland organoids indicates that expression and secretion of these products are upregulated following sequential exposure to oestrogen, progesterone and trophoblastic and decidual hormones, in particular prolactin. Hence, a feed-forward signalling dialogue is proposed among the trophoblast, decidua and glands that enables the placenta to stimulate its own development, independent of that of the embryo. Many common complications of pregnancy represent a spectrum of disorders associated with deficient trophoblast proliferation. Increasing evidence suggests that this spectrum is mirrored by one of impaired decidualization, potentially compromising histotroph secretion through diminished prolactin secretion and reduced gland function. Optimizing endometrial wellbeing prior to conception may therefore help to prevent common pregnancy complications, such as miscarriage, growth restriction and pre-eclampsia.

Siglecs in allergy and asthma

The term "allergic diseases" encompasses several common, IgE-mediated conditions that range from being annoying to those that are life-threatening. Available treatments include active avoidance of the instigating allergen and the use of a variety of oral, inhaled, intranasal, intraocular and injected agents. While most individuals with allergies do well with existing therapies, there are still unmet therapeutic needs. Siglecs (sialic acid-binding, immunoglobulin-like lectins) are a family of single-pass transmembrane I-type lectins found on various subsets of cells, especially those of the immune system. All Siglecs have extracellular domains recognizing sialoside ligands, and most contain cytoplasmic domains with inhibitory signaling activity. This review focuses on Siglecs that likely play a role in regulating allergic and asthmatic responses, and how specific Siglecs, expressed on cells such as eosinophils and mast cells, are being targeted for therapeutic benefit.

Roles of N-linked glycosylation and glycan-binding proteins in placentation: trophoblast infiltration, immunomodulation, angiogenesis, and pathophysiology

Protein N-linked glycosylation is a structurally diverse post-translational modification that stores biological information in a larger order of magnitude than other post-translational modifications such as phosphorylation, ubiquitination and acetylation. This gives N-glycosylated proteins a diverse range of properties and allows glyco-codes (glycan-related information) to be deciphered by glycan-binding proteins (GBPs). The intervillous space of the placenta is richly populated with membrane-bound and secreted glycoproteins. Evidence exists to suggest that altering the structural nature of their N-glycans can impact several trophoblast functions, which include those related to interactions with decidual cells. This review summarizes trophoblast-related activities influenced by N-glycan-GBP recognition, exploring how different subtypes of trophoblasts actively adapt to characteristics of the decidualized endometrium through cell-specific expression of N-glycosylated proteins, and how these cells receive decidua-derived signals via N-glycan-GBP interactions. We highlight work on how changes in N-glycosylation relates to the success of trophoblast infiltration, interactions of immunomodulators, and uterine angiogenesis. We also discuss studies that suggest aberrant N-glycosylation of trophoblasts may contribute to the pathogenesis of pregnancy complications (e.g. pre-eclampsia, early spontaneous miscarriages and hydatidiform mole). We propose that a more in-depth understanding of how N-glycosylation shapes trophoblast phenotype during early pregnancy has the potential to improve our approach to predicting, diagnosing and alleviating poor maternal/fetal outcomes associated with placental dysfunction.

Endometrial small extracellular vesicles regulate human trophectodermal cell invasion by reprogramming the phosphoproteome landscape

A series of cyclical events within the uterus are crucial for pregnancy establishment. These include endometrial regeneration following menses, under the influence of estrogen (proliferative phase), then endometrial differentiation driven by estrogen/progesterone (secretory phase), to provide a microenvironment enabling attachment of embryo (as a hatched blastocyst) to the endometrial epithelium. This is followed by invasion of trophectodermal cells (the outer layer of the blastocyst) into the endometrium tissue to facilitate intrauterine development. Small extracellular vesicles (sEVs) released by endometrial epithelial cells during the secretory phase have been shown to facilitate trophoblast invasion; however, the molecular mechanisms that underline this process remain poorly understood. Here, we show that density gradient purified sEVs (1.06-1.11 g/ml, Alix⁺ and TSG101⁺, ∼180 nm) from human endometrial epithelial cells (hormonally primed with estrogen and progesterone vs. estrogen alone) are readily internalized by a human trophectodermal stem cell line and promote their invasion into Matrigel matrix. Mass spectrometry-based proteome analysis revealed that sEVs reprogrammed trophectoderm cell proteome and their cell surface proteome (surfaceome) to support this invasive phenotype through upregulation of pro-invasive regulators associated with focal adhesions (NRP1, PTPRK, ROCK2, TEK), embryo implantation (FBLN1, NIBAN2, BSG), and kinase receptors (EPHB4/B2, ERBB2, STRAP). Kinase substrate prediction highlighted a central role of MAPK3 as an upstream kinase regulating target cell proteome reprogramming. Phosphoproteome analysis pinpointed upregulation of MAPK3 T204/T202 phosphosites in hTSCs following sEV delivery, and that their pharmacological inhibition significantly abrogated invasion. This study provides novel molecular insights into endometrial sEVs orchestrating trophoblast invasion, highlighting the microenvironmental regulation of hTSCs during embryo implantation.

Patient-derived Siglec-6-targeting antibodies engineered for T-cell recruitment have potential therapeutic utility in chronic lymphocytic leukemia

BACKGROUND

Despite numerous therapeutic options, safe and curative therapy is unavailable for most patients with chronic lymphocytic leukemia (CLL). A drawback of current therapies such as the anti-CD20 monoclonal antibody (mAb) rituximab is the elimination of all healthy B cells, resulting in impaired humoral immunity. We previously reported the identification of a patient-derived, CLL-binding mAb, JML-1, and identified sialic acid-binding immunoglobulin-like lectin-6 (Siglec-6) as the target of JML-1. Although little is known about Siglec-6, it appears to be an attractive target for cancer immunotherapy due to its absence on most healthy cells and tissues.

METHODS

We used a target-specific approach to mine for additional patient-derived anti-Siglec-6 mAbs. To assess the therapeutic utility of targeting Siglec-6 in the context of CLL, T cell-recruiting bispecific antibodies (T-biAbs) that bind to Siglec-6 and CD3 were engineered into single-chain variable fragment-Fc and dual-affinity retargeting (DART)-Fc constructs. T-biAbs were evaluated for their activity in vitro, ex vivo, and in vivo.

RESULTS

We discovered the anti-Siglec-6 mAbs RC-1 and RC-2, which bind with higher affinity than JML-1 yet maintain similar specificity. Both JML-1 and RC-1 T-biAbs were effective at activating T cells and killing Siglec-6+ target cells. The RC-1 clone in the DART-Fc format was the most potent T-biAb tested and was the only anti-Siglec-6 T-biAb that eliminated Siglec-6+ primary CLL cells via autologous T cells at pathological T-to-CLL cell ratios. Tested at healthy T-to-B cell ratios, it also eliminated a Siglec-6+ fraction of primary B cells from healthy donors. The subpicomolar potency of the DART-Fc format was attributed to the reduction in the length and flexibility of the cytolytic synapse. Furthermore, the RC-1 T-biAb was effective at clearing MEC1 CLL cells in vivo and demonstrated a circulatory half-life of over 7 days.

CONCLUSION

Siglec-6-targeting T-biAbs are highly potent and specific for eliminating Siglec-6+ leukemic and healthy B cells while sparing Siglec-6- healthy B cells, suggesting a unique treatment strategy for CLL with diminished suppression of humoral immunity. Our data corroborate reports that T-biAb efficacy is dependent on synapse geometry and reveal that synapse architecture can be tuned via antibody engineering. Our fully human anti-Siglec-6 antibodies and T-biAbs have potential for cancer immunotherapy.

TRIAL REGISTRATION NUMBER

NCT00923507.

Human placental development and function

The placenta is a transient fetal organ that plays a critical role in the health and wellbeing of both the fetus and its mother. Functionally, the placenta sustains the growth of the fetus as it facilitates delivery of oxygen and nutrients and removal of waste products. Not surprisingly, defective early placental development is the primary cause of common disorders of pregnancy, including recurrent miscarriage, fetal growth restriction, pre-eclampsia and stillbirth. Adverse pregnancy conditions will also affect the life-long health of the fetus via developmental programming[1]. Despite its critical importance in reproductive success and life-long health, our understanding of placental development is not extensive, largely due to ethical limitations to studying early or chronological placental development, lack of long-term in vitro models, or comparative animal models. In this review, we examine current knowledge of early human placental development, discuss the critical role of the maternal endometrium and of the fetal-maternal dialogue in pregnancy success, and we explore the latest models of trophoblast and endometrial stem cells. In addition, we discuss the role of oxygen in placental formation and function, how nutrient delivery is mediated during the periods of histotrophic nutrition (uptake of uterine secretions) and haemotrophic nutrition (exchange between the maternal and fetal circulations), and how placental endocrine function facilitates fetal growth and development.

Elevated trophoblastic Siglec6 contributes to the impairment of vascular endothelial cell functions by downregulating Wnt6/β-catenin signaling in preeclampsia

Preeclampsia (PE), a systemic vascular disorder, is the leading cause of maternal and perinatal morbidity and mortality, and its pathogenesis has yet to be fully elucidated. Siglec6, a transmembrane protein, is highly expressed in human placental trophoblasts, and previous studies have shown that Siglec6 overexpression correlates with PE, but the role of Siglec6 during PE progression is unknown. Here, we demonstrated that the mRNA and protein expression levels of Siglec6 were upregulated in early-onset PE placentas compared with uncomplicated pregnancies, and Siglec6 was primarily located in syncytiotrophoblasts (STBs) and extravillous trophoblasts (EVTs). Moreover, our results showed that chemical reagent-induced HIF-1α accumulation promoted the mRNA and protein levels of Siglec6 in HTR8/SVneo and BeWo cells. Although Siglec6 overexpression did not affect HTR8/SVneo cell proliferation, migration, and invasion, the conditional medium derived from the Siglec6 overexpressed HTR8/SVneo cells (Siglec6-OE-CM) significantly impaired the proliferation, migration, invasion, and tube formation of human umbilical vein endothelial cells (HUVECs). Subsequently, the transcriptome sequencing results revealed that Siglec6 overexpression led to the downregulation of Wnt6 in HTR8/SVneo cells, which was further confirmed by qPCR and ELISA. Recombinant human Wnt6 reversed Siglec6-OE-CM-mediated suppression of HUVEC functions by reactivating the Wnt/β-catenin signaling pathway. Altogether, our study found that elevated trophoblastic Siglec6 contributed to the impairment of vascular endothelial cell functions by downregulating Wnt6/β-catenin signaling.

Functional and Phenotypic Characterization of Siglec-6 on Human Mast Cells

Mast cells are tissue-resident cells that contribute to allergic diseases, among others, due to excessive or inappropriate cellular activation and degranulation. Therapeutic approaches to modulate mast cell activation are urgently needed. Siglec-6 is an immunoreceptor tyrosine-based inhibitory motif (ITIM)-bearing receptor selectively expressed by mast cells, making it a promising target for therapeutic intervention. However, the effects of its engagement on mast cells are poorly defined. Siglec-6 expression and endocytosis on primary human mast cells and mast cell lines were assessed by flow cytometry. SIGLEC6 mRNA expression was examined by single-cell RNAseq in esophageal tissue biopsy samples. The ability of Siglec-6 engagement or co-engagement to prevent primary mast cell activation was determined based on assessments of mediator and cytokine secretion and degranulation markers. Siglec-6 was highly expressed by all mast cells examined, and the SIGLEC6 transcript was restricted to mast cells in esophageal biopsy samples. Siglec-6 endocytosis occurred with delayed kinetics relative to the related receptor Siglec-8. Co-crosslinking of Siglec-6 with FcεRIα enhanced the inhibition of mast cell activation and diminished downstream ERK1/2 and p38 phosphorylation. The selective, stable expression and potent inhibitory capacity of Siglec-6 on human mast cells are favorable for its use as a therapeutic target in mast cell-driven diseases.

Radiographical Evaluation of Tumor Immunosuppressive Microenvironment and Treatment Outcomes in Gastric Cancer: A Retrospective, Multicohort Study

BACKGROUND

The tumor immunosuppressive microenvironment can influence treatment response and outcomes. A previously validated immunosuppression scoring system (ISS) assesses multiple immune checkpoints in gastric cancer (GC) using tissue-based assays. We aimed to develop a radiological signature for non-invasive assessment of ISS and treatment outcomes.

METHODS

A total of 642 patients with resectable GC from three centers were divided into four cohorts. Radiomic features were extracted from portal venous-phase CT images of GC. A radiomic signature for predicting ISS (RISS) was constructed using the least absolute shrinkage and selection operator (LASSO) regression method. Moreover, we investigated the value of the RISS in predicting survival and chemotherapy response.

RESULTS

The RISS, which consisted of 10 selected features, showed good discrimination of immunosuppressive status in three independent cohorts (area under the curve = 0.840, 0.809, and 0.843, respectively). Multivariate analysis revealed that the RISS was an independent prognostic factor for both disease-free survival (DFS) and overall survival (OS) in all cohorts (all p < 0.05). Further analysis revealed that stage II and III GC patients with low RISS exhibited a favorable response to adjuvant chemotherapy (OS: hazard ratio [HR] 0.407, 95% confidence interval [CI] 0.284-0.584); DFS: HR 0.395, 95% CI 0.275-0.568). Furthermore, the RISS could predict prognosis and select stage II and III GC patients who could benefit from adjuvant chemotherapy independent of microsatellite instability status and Epstein-Barr virus status.

CONCLUSION

The new, non-invasive radiomic signature could effectively predict the immunosuppressive status and prognosis of GC. Moreover, the RISS could help identify stage II and III GC patients most likely to benefit from adjuvant chemotherapy and avoid overtreatment.

Regulation of the innate immune cells during pregnancy: An immune checkpoint perspective

The foetus can be regarded as a half‐allograft implanted into the maternal body. In a successful pregnancy, the mother does not reject the foetus because of the immune tolerance mechanism at the maternal‐foetal interface. The innate immune cells are a large part of the decidual leukocytes contributing significantly to a successful pregnancy. Although the contributions have been recognized, their role in human pregnancy has not been completely elucidated. Additionally, the accumulated evidence demonstrates that the immune checkpoint molecules expressed on the immune cells are co‐inhibitory receptors regulating their activation and biological function. Therefore, it is critical to understand the immune microenvironment and explore the function of the innate immune cells during pregnancy. This review summarizes the classic immune checkpoints such as PD‐1, CTLA‐4 and some novel molecules recently identified, including TIM‐3, CD200, TIGIT and the Siglecs family on the decidual and peripheral innate immune cells during pregnancy. Furthermore, it emphasizes the role of the immune checkpoint molecules in pregnancy‐associated complications and reproductive immunotherapy.

Mapping themes trends and knowledge structure of trophoblastic invasion, a bibliometric analysis from 2012-2021

OBJECTIVES

Trophoblastic invasion at the maternal-fetal interface can affect pregnancy outcomes. To describe an intuitive theme trends and knowledge structure of trophoblastic invasion-related literature from a bibliometric perspective, and provide researchers with new research hotspots.

STUDY DESIGN

The literature form PubMed database related to trophoblastic invasion from January 1, 2012 to April 30, 2021 were extracted, and then biclustering analysis, co-word analysis, strategy diagram and social network analysis were performed to provide immature, or newly emerging research hotspots for researchers.

RESULTS

A total of 96 high-frequency medical subjects heading terms were extracted and classified into 6 clusters. Themes in the first and second quadrant of strategy diagram, including trophoblasts metabolism, placenta metabolism, pre-eclampsia, etc., as the mature parts of the research on trophoblastic invasion have been well developed. On the other hand, themes in the third and fourth quadrants of strategy diagram, such as embryo implantation and trophoblasts immunology, pregnancy complication, matrix metalloproteinase and trophoblasts metabolism, habitual abortion and trophoblasts metabolism, etc., are immature themes. Social network analysis suggests that themes at the edge, such as habitual abortion / metabolism, placenta / immunology, natural killer cells / physiology, natural killer cells / immunology, embryo implantation / immunology, are considered new research hotspots and have considerable research space.

CONCLUSION

By analyzing the research hotspots related to trophoblastic invasion, immature themes and emerging hotspots deserve more attention and can be considered as hints when launching new research projects.

Vaginal sialoglycan foraging by Gardnerella vaginalis: mucus barriers as a meal for unwelcome guests?

Bacterial vaginosis (BV) is a condition of the vaginal microbiome in which there are few lactobacilli and abundant anaerobic bacteria. Members of the genus Gardnerella are often one of the most abundant bacteria in BV. BV is associated with a wide variety of poor health outcomes for women. It has been recognized since the 1980s that women with BV have detectable and sometimes markedly elevated levels of sialidase activity in vaginal fluids and that bacteria associated with this condition produce this activity in culture. Mounting evidence collected using diverse methodologies points to the conclusion that BV is associated with a reduction in intact sialoglycans in cervicovaginal secretions. Here we review evidence for the contributions of vaginal bacteria, especially Gardnerella, in the processes of mucosal sialoglycan degradation, uptake, metabolism and depletion. Our understanding of the impacts of vaginal sialoglycan degradation is still limited. However, the potential implications of sialic acid depletion are discussed in light of our current understanding of the roles played by sialoglycans in vaginal physiology.

Decidual glycodelin-A polarizes human monocytes into a decidual macrophage-like phenotype through Siglec-7

Decidual macrophages constitute 20-30% of the total leukocytes in the uterus of pregnant women, regulating the maternal immune tolerance and placenta development. Abnormal number or activities of decidual macrophages (dMs) are associated with fetal loss and pregnancy complications, such as preeclampsia. Monocytes differentiate into dMs in a decidua-specific microenvironment. Despite their important roles in pregnancy, the exact factors that regulate the differentiation into dMs remain unclear. Glycodelin-A (PAEP, hereafter referred to as GdA) is a glycoprotein that is abundantly present in the decidua, and plays an important role in fetomaternal defense and placental development. It modulates the differentiation and activity of several immune cell types residing in the decidua. In this study, we demonstrated that GdA induces the differentiation of human monocytes into dM-like phenotypes in terms of transcriptome, cell surface marker expression, secretome, and regulation of trophoblast and endothelial cell functions. We found that Sialic acid-binding Ig-like lectin 7 (Siglec-7) mediates the binding and biological actions of GdA in a sialic acid-dependent manner. We, therefore, suggest that GdA, induces the polarization of monocytes into dMs to regulate fetomaternal tolerance and placental development.

Glycodelin-A stimulates the conversion of human peripheral blood CD16-CD56bright NK cell to a decidual NK cell-like phenotype

STUDY QUESTION

Does glycodelin-A (GdA) induce conversion of human peripheral blood CD16-CD56bright natural killer (NK) cells to decidual NK (dNK) cells to facilitate placentation?

SUMMARY ANSWER

GdA binds to blood CD16-CD56bright NK cells via its sialylated glycans and converts them to a dNK-like cells, which in turn regulate endothelial cell angiogenesis and trophoblast invasion via vascular endothelial growth factor (VEGF) and insulin-like growth factor-binding protein 1 (IGFBP-1) secretion, respectively.

WHAT IS KNOWN ALREADY

dNK cells are the most abundant leucocyte population in the decidua. These cells express CD16-CD56bright phenotype. Peripheral blood CD16-CD56bright NK cells and hematopoietic precursors have been suggested to be capable of differentiating towards dNK cells upon exposure to the decidual microenvironment. These cells regulate trophoblast invasion during spiral arteries remodelling and mediate homoeostasis and functions of the endothelial cells. GdA is an abundant glycoprotein in the human decidua with peak expression between the 6th and 12th week of gestation, suggesting a role in early pregnancy. Indeed, GdA interacts with and modulates functions and differentiation of trophoblast and immune cells in the human feto-maternal interface. Aberrant GdA expression during pregnancy is associated with unexplained infertility, pregnancy loss and pre-eclampsia.

STUDY DESIGN, SIZE, DURATION

CD16+CD56dim, CD16-CD56bright and dNK cells were isolated from human peripheral blood and decidua tissue, respectively, by immuno-magnetic beads or fluorescence-activated cell sorting. Human extravillous trophoblasts were isolated from first trimester placental tissue after termination of pregnancy. Biological activities of the cells were studied after treatment with GdA at a physiological dose of 5 μg/mL. GdA was purified from human amniotic fluid by immuno-affinity chromatography.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Expression of VEGF, CD9, CD49a, CD151 and CD158a in the cells were determined by flow cytometry. Angiogenic proteins in the spent media of NK cells were determined by cytokine array and ELISA. Blocking antibodies were used to study the functions of the identified angiogenic proteins. Endothelial cell angiogenesis was determined by tube formation and trans-well migration assays. Cell invasion and migration were determined by trans-well invasion/migration assay. Binding of normal and de-sialylated GdA, and expression of L-selectin and siglec-7 on the NK cells were analysed by flow cytometry. The association between GdA and L-selectin on NK cells was confirmed by immunoprecipitation. Extracellular signal-regulated protein kinases (ERK) activation was determined by Western blotting and functional assays.

MAIN RESULTS AND THE ROLE OF CHANCE

GdA treatment enhanced the expression of dNK cell markers CD9 and CD49a and the production of the functional dNK secretory product VEGF in the peripheral blood CD16-CD56bright NK cells. The spent media of GdA-treated CD16-CD56bright NK cells promoted tube formation of human umbilical vein endothelial cells and invasiveness of trophoblasts. These stimulatory effects were mediated by the stimulatory activities of GdA on an ERK-activation dependent production of VEGF and IGFBP-1 by the NK cells. GdA had a stronger binding affinity to the CD16-CD56bright NK cells as compared to the CD16+CD56dim NK cells. This GdA-NK cell interaction was reduced by de-sialylation. GdA interacted with L-selectin, expressed only in the CD16-CD56bright NK cells, but not in the CD16+CD56dim NK cells. Anti-L-selectin functional blocking antibody suppressed the binding and biological activities of GdA on the NK cells.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Some of the above findings are based on a small sample size of peripheral blood CD16-CD56bright NK cells. These results need to be confirmed with human primary dNK cells.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study on the biological role of GdA on conversion of CD16-CD56bright NK cells to dNK-like cells. Further investigation on the glycosylation and functions of GdA will enhance our understanding on human placentation and placenta-associated complications with altered NK cell biology.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Hong Kong Research Grant Council Grant 17122415, Sanming Project of Medicine in Shenzhen, the Finnish Cancer Foundation, Sigrid Jusélius Foundation and the Finnish Society of Clinical Chemistry. The authors have no competing interests to declare.

Identification of unexplored substrates of the serine protease, thrombin, using N-terminomics strategy

The function and regulation of thrombin is a complex as well as an intriguing aspect of evolution and has captured the interest of many investigators over the years. The reported substrates of thrombin are coagulation factors V, VIII, XI, XIII, protein C and fibrinogen. However, these may not be all the substrate of thrombin and therefore its functional role(s), may not have been completely comprehended. The purpose of our study was to identify hitherto unreported substrates of thrombin from human plasma using a N-terminomics protease substrate identification method. We identified 54 putative substrates of thrombin of which 12 are already known and 42 are being reported for the first time. Amongst the proteins identified, recombinant siglec-6 and purified serum alpha-1-acid glycoprotein were validated by cleavage with thrombin. We have discussed the probable relevance of siglec-6 cleavage by thrombin in human placenta mostly because an upregulation in the expression of siglec-6 and thrombin has been reported in the placenta of preeclampsia patients. We also speculate the role of alpha-1-acid glycoprotein cleavage by thrombin in the acute phase as alpha-1-acid glycoprotein is known to be an inhibitor of platelet aggregation whereas thrombin is known to trigger platelet aggregation.

Analysis of Glycodelin Levels Before and After Hysteroscopic Polypectomy in Infertile Patients

Glycodelin (or placental protein 14) is a glycoprotein located in the glandular and thin epithelium of the endometrium. It is considered an important factor in the implantation process, and its traces can be found in elevated concentrations in the uterine flushing obtained at the time of implantation, while in the proliferative phase of the cycle, its levels are low. A certain concentration has been found to inhibit the binding of spermatozoids to the zona pellucida of the oocites therefore, it effects conception. It has a role in angiogenesis and is in high concentrations in the tissues of both benign and malignant gynaecological tumours.

The aim of this study is to analyse and display the glycodelin level changes before and after hysteroscopic polypectomy in infertile patients in the uterine flushing fluid and serum. This survey covers 80 infertile patients, who were divided into two groups. The first group, the experimental group, consisted of 50 infertile patients with endometrial polyps, and a control group of 30 infertile patients without endometrial polyps was also included.

The results primarily indicate the existence of changes in glycodelin levels preoperatively in the flushing and venous blood in infertile patients with endometrial polyps compared with the levels after surgery. In the control group of patients, no significant change in the glycodelin levels was detected in the flushing and venous blood. When comparing these two groups, statistically significant differences in the glycodelin levels in the flushing and venous blood were noted. We conclude that the presence of endometrial polyps in the cavum uteri affects the increase in the glycodelin concentration in the flushing fluid and in the plasma. Increased glycodelin concentrations complicate fertilization and implantation.

Glycodelin is a potential novel follow-up biomarker for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and aggressive tumor with a short survival time arising from the mesothelial cells of the pleura. Soluble mesothelin-related peptide (SMRP), osteopontin or EFEMP1 (Fibulin-3) are well described biomarkers for malignant mesothelioma with moderate sensitivity and specificity. In this study, we characterized the expression of glycodelin, a marker for risk pregnancy, in MPM by RNA and protein analyses and investigated its potential as a MPM biomarker. We were able to detect glycodelin in the serum of MPM patients. Compared to benign lung diseases, the serum levels were significant increased. Patients with high glycodelin serum levels revealed a worse overall survival. The glycodelin serum levels correlated with the tumor response to treatment. A comparison of SMRP and glycodelin serum measurement in a large patient cohort demonstrated that the detection of both soluble factors can increase the reliable diagnostic of MPM. Glycodelin was highly expressed in MPM tumors. Analyses of a tissue micro array indicated that the immunomodulatory form glycodelin A was expressed in MPM and correlated with the survival of the patients. Altogether, glycodelin seems to be a new potential biomarker for the aggressive malignant pleural mesothelioma.

The maternal plasma proteome changes as a function of gestational age in normal pregnancy: a longitudinal study

OBJECTIVE

Pregnancy is accompanied by dramatic physiological changes in maternal plasma proteins. Characterization of the maternal plasma proteome in normal pregnancy is an essential step for understanding changes to predict pregnancy outcome. The objective of this study was to describe maternal plasma proteins that change in abundance with advancing gestational age and determine biological processes that are perturbed in normal pregnancy.

STUDY DESIGN

A longitudinal study included 43 normal pregnancies that had a term delivery of an infant who was appropriate for gestational age without maternal or neonatal complications. For each pregnancy, 3 to 6 maternal plasma samples (median, 5) were profiled to measure the abundance of 1125 proteins using multiplex assays. Linear mixed-effects models with polynomial splines were used to model protein abundance as a function of gestational age, and the significance of the association was inferred via likelihood ratio tests. Proteins considered to be significantly changed were defined as having the following: (1) >1.5-fold change between 8 and 40 weeks of gestation; and (2) a false discovery rate-adjusted value of P < .1. Gene ontology enrichment analysis was used to identify biological processes overrepresented among the proteins that changed with advancing gestation.

RESULTS

The following results were found: (1) Ten percent (112 of 1125) of the profiled proteins changed in abundance as a function of gestational age; (2) of the 1125 proteins analyzed, glypican-3, sialic acid-binding immunoglobulin-type lectin-6, placental growth factor, C-C motif-28, carbonic anhydrase 6, prolactin, interleukin-1 receptor 4, dual-specificity mitogen-activated protein kinase 4, and pregnancy-associated plasma protein-A had more than a 5-fold change in abundance across gestation (these 9 proteins are known to be involved in a wide range of both physiological and pathological processes, such as growth regulation, embryogenesis, angiogenesis immunoregulation, inflammation etc); and (3) biological processes associated with protein changes in normal pregnancy included defense response, defense response to bacteria, proteolysis, and leukocyte migration (false discovery rate, 10%).

CONCLUSION

The plasma proteome of normal pregnancy demonstrates dramatic changes in both the magnitude of changes and the fraction of the proteins involved. Such information is important to understand the physiology of pregnancy and the development of biomarkers to differentiate normal vs abnormal pregnancy and determine the response to interventions.

Sialic Acid Mimetics to Target the Sialic Acid-Siglec Axis

Sialic acid sugars are vital regulators of the immune system through binding to immunosuppressive sialic acid-binding immunoglobulin-like lectin (Siglec) receptors on immune cells. Aberrant sialic acid-Siglec interactions are associated with an increasing number of pathologies including infection, autoimmunity, and cancer. Therefore, the sialic acid-Siglec axis is an emerging target to prevent or affect the course of several diseases. Chemical modifications of the natural sialic acid ligands have led to sialic acid mimetics (SAMs) with improved binding affinity and selectivity towards Siglecs. Recent progress in glycobiotechnology allows the presentation of these SAMs on nanoparticles, polymers, and living cells via bioorthogonal synthesis. These developments now enable the detailed study of the sialic acid-Siglec axis including its therapeutic potential as an immune modulator.

Analysis of the placental tissue transcriptome of normal and preeclampsia complicated pregnancies

Preeclampsia is one of the most severe gestational complications which is one of the leading causes of maternal and perinatal morbidity and mortality. A growth in the incidence of severe and combined forms of the pathology has been observed in recent years. According to modern concepts, inadequate cytotrophoblast invasion into the spiral arteries of the uterus and development of the ischemia-reperfusion syndrome in the placental tissue play the leading role in the development of preeclampsia, which is characterized by multipleorgan failure. In this regard, our work was aimed at studying the patterns of placental tissue transcriptome that are specific to females with PE and with physiological pregnancy, as well as identifying the potential promising biomarkers and molecular mechanisms of this pathology. We have identified 63 genes whose expression proved to differ significantly in the placental tissue of females with PE and with physiological pregnancy. A cluster of differentially expressed genes (DEG) whose expression level is increased in patients with preeclampsia includes not only the known candidate genes that have been identified in many other genome-wide studies (e.g., LEP, BHLHB2, SIGLEC6, RDH13, BCL6), but also new genes (ANKRD37, SYDE1, CYBA, ITGB2, etc.), which can be considered as new biological markers of preeclampsia and are of further interest. The results of a functional annotation of DEG show that the development of preeclampsia may be related to a stress response, immune processes, the regulation of cell-cell interactions, intracellular signaling cascades, etc. In addition, the features of the differential gene expression depending on preeclampsia severity were revealed. We have found evidence of the important role of the molecular mechanisms responsible for the failure of immunological tolerance and initiation of the pro-inflammatory cascade in the development of severe preeclampsia. The results obtained elaborate the concept of the pathophysiology of preeclampsia and contain the information necessary to work out measures for targeted therapy of this disease. ;

The role of glycans in immune evasion: the human fetoembryonic defence system hypothesis revisited

Emerging data suggest that mechanisms to evade the human immune system may be shared by the conceptus, tumour cells, persistent pathogens and viruses. It is therefore timely to revisit the human fetoembryonic defense system (Hu-FEDS) hypothesis that was proposed in two papers in the 1990s. The initial paper suggested that glycoconjugates expressed in the human reproductive system inhibited immune responses directed against gametes and the developing human by employing their carbohydrate sequences as functional groups. These glycoconjugates were proposed to block specific binding interactions and interact with lectins linked to signal transduction pathways that modulated immune cell functions. The second article suggested that aggressive tumour cells and persistent pathogens (HIV, H. pylori, schistosomes) either mimicked or acquired the same carbohydrate functional groups employed in this system to evade immune responses. This subterfuge enabled these pathogens and tumour cells to couple their survival to the human reproductive imperative. The Hu-FEDS model has been repeatedly tested since its inception. Data relevant to this model have also been obtained in other studies. Herein, the Hu-FEDS hypothesis is revisited in the context of these more recent findings. Far more supportive evidence for this model now exists than when it was first proposed, and many of the original predictions have been validated. This type of subterfuge by pathogens and tumour cells likely applies to all sexually reproducing metazoans that must protect their gametes from immune responses. Intervention in these pathological states will likely remain problematic until this system of immune evasion is fully understood and appreciated.

Soluble human leukocyte antigen-g5 activates extracellular signal-regulated protein kinase signaling and stimulates trophoblast invasion

Soluble human leukocyte antigen-G (HLA-G) is a non-classical class Ib HLA molecule that is secreted from blastocysts. Soluble HLA-G modulates the immune tolerance of the mother and can be used as a prognostic factor for the clinical pregnancy rate. However, the underlying mechanism of how soluble HLA-G5 affects pregnancy remains largely unknown. We hypothesized that soluble HLA-G5 promotes successful implantation and pregnancy by modulating trophoblast invasion through receptor binding and activation of extracellular signal-regulated protein kinase (ERK) signaling pathway. Recombinant HLA-G5 protein over-expressed in E. coli BL21 was purified to near homogeneity. We studied the expression of HLA-G5 and its receptors, the leukocyte immunoglobulin-like receptor subfamily B1 (LILRB1) and killer cell immunoglobulin-like receptor 2DL4 (KIR2DL4), in primary trophoblasts and trophoblastic (JAr and JEG-3) cell lines by florescence-labeled HLA-G5. HLA-G5 was detected in the primary trophoblasts and JEG-3 cells. The LILRB1 and KIR2DL4 receptors were expressed in both primary trophoblasts and trophoblastic cell lines. HLA-G5 stimulated cell invasion (p<0.05) and increased urokinase (uPA) and matrix metalloproteinases (MMPs) transcripts and their activity (p<0.05) in trophoblastic cells. HLA-G5 activated the ERK signaling pathway and induced ERK1/2 phosphorylation in the trophoblastic cell lines. Addition of ERK inhibitors (U0126 and PD98059) nullified the stimulatory effect of HLA-G5 on trophoblastic cell invasion. Taken together, HLA-G5 induced trophoblast invasion by binding to KIR2DL4 and LILRB1, by increasing uPA and MMPs expressions and by activating the ERK signaling pathway.

Identification of CD147 (basigin) as a mediator of trophoblast functions

STUDY QUESTION

Does CD147 regulate trophoblast functions in vitro?

SUMMARY ANSWER

CD147 exists as a receptor complex on human trophoblast and regulates the implantation, invasion and differentiation of trophoblast.

WHAT IS KNOWN ALREADY

CD147 is a membrane protein implicated in a variety of physiological and pathological conditions due to its regulation of cell-cell recognition, cell differentiation and tissue remodeling. Reduced placental CD147 expression is associated with pre-eclampsia, but the mechanism of actions remains unclear.

STUDY DESIGN, SIZE, DURATION

A loss of function approach or functional blocking antibody was used to study the function of CD147 in primary human cytotrophoblasts isolated from first trimester termination of pregnancy and/or in the BeWo cell line, which possesses characteristics of human cytotrophoblasts.

PARTICIPANTS/MATERIALS, SETTING METHODS

CD147 expression was analyzed by immunofluorescence staining and western blotting. CD147-associated protein complex on plasma membrane were separated by blue native gel electrophoresis and identified by reversed-phase liquid chromatography coupled with quadrupole time-of-flight hybrid mass spectrometer. Cell proliferation and invasion were determined by fluorometric cell proliferation assays and transwell invasion assays, respectively. Matrix metalloproteinases (MMPs) and urokinase plasminogen activator (uPA) activities were measured by gelatin gel zymography and uPA assay kits, respectively. Cell migration was determined by wound-healing assays. Cell fusion was analyzed by immunocytochemistry staining of E-cadherin and 4',6-diamidino-2-phenylindole. The transcripts of matrix proteinases and trophoblast lineage markers were measured by quantitative PCR. Extracellular signal-regulated kinase (ERK) activation was analyzed by western blot using antibodies against ERKs.

MAIN RESULTS AND THE ROLE OF CHANCE

CD147 exists as protein complexes on the plasma membrane of primary human cytotrophoblasts and BeWo cells. Several known CD147-interacting partners, including integrin β1 and monocarboxylate transporter-1, were identified. Suppression of CD147 by siRNA significantly (P < 0.05) reduced trophoblast-endometrial cell interaction, cell invasion, syncytialization, differentiation and ERK activation of BeWo cells. Consistently, anti-CD147 functional blocking antibody suppressed the invasiveness of primary human cytotrophoblasts. The reduced invasiveness was probably due to the restrained (P < 0.05) enzyme activities of MMP-2, MMP-9 and uPA.

LIMITATIONS, REASONS FOR CAUTION

Most of the above findings are based on BeWo cell lines. These results need to be confirmed with human first trimester primary cytotrophoblast.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study on the role of CD147 in trophoblast function. Further investigation on the function of CD147 and its associated protein complexes will enhance our understanding on human placentation.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by the University of Hong Kong Grant 201011159200. The authors have no competing interests to declare.

Glycodelin in reproduction

To achieve a successful pregnancy in humans, sperm is required for capacitation, followed by binding to and entry into an oocyte. Maternal endometrial epithelial cells (EECs) prepare the appropriate implantation environment through regulation of immune cells and endometrial cells. After acquiring endometrial receptivity, a successful pregnancy consists of complex and finely regulated steps involving apposition, adhesion, invasion, and penetration. Glycodelin is a secretory glycoprotein that affects cell proliferation, differentiation, adhesion, and motility. Glycodelin has four glycoforms (glycodelin-A, -S, -F. and -C); differences in glycosylation affect each characteristic function. Glycodelin has a unique temporospatial pattern of expression, primarily in the reproductive tract where glycodelin is mid-secretory phase-dominant. Recent studies have demonstrated that glycodelin protein has the potential to regulate various processes, including immunosuppression, fertilization, and implantation. This review details the orchestrated regulation of successful pregnancy by glycodelin as well as a discussion of the basic characteristics of glycodelin.

A lesson for cancer research: placental microarray gene analysis in preeclampsia

Tumor progression and pregnancy share many common features, such as immune tolerance and invasion. The invasion of trophoblasts in the placenta into the uterine wall is essential for fetal development, and is thus precisely regulated. Its deregulation has been implicated in preeclampsia, a leading cause for maternal and perinatal mortality and morbidity. Pathogenesis of preeclampsia remains to be defined. Microarray-based gene profiling has been widely used for identifying genes responsible for preeclampsia. In this review, we have summarized the recent data from the microarray studies with preeclamptic placentas. Despite the complex of gene signatures, suggestive of the heterogeneity of preeclampsia, these studies identified a number of differentially expressed genes associated with preeclampsia. Interestingly, most of them have been reported to be tightly involved in tumor progression. We have discussed these interesting genes and analyzed their potential molecular functions in preeclampsia, compared with their roles in malignancy development. Further investigations are warranted to explore the involvement in molecular network of each identified gene, which may provide not only novel strategies for prevention and therapy for preeclampsia but also a better understanding of cancer cells. The trophoblastic cells, with their capacity for proliferation and differentiation, apoptosis and survival, migration, angiogenesis and immune modulation by exploiting similar molecular pathways, make them a compelling model for cancer research.

Embryonic sex induces differential expression of proteins in bovine uterine fluid

The bovine endometrium recognizes early embryos and reacts differently depending on the developmental potential of the embryo. However, it is unknown whether the endometrium can distinguish embryonic sex. Our objective was to analyze sexual dimorphism in the uterus in response to male and female embryos. Differentially expressed (DE) proteins, different levels of hexoses, and other embryotrophic differences were analyzed in uterine fluid (UF). Proteomic analysis of day-8 UF recovered from heifers after the transfer of day-5 male or female embryos identified 23 DE proteins. Regulated proteasome/immunoproteasome protein subunits indicated differences in antigen processing between UF carrying male embryos (male-UF) or female embryos (female-UF). Several enzymes involved in glycolysis/gluconeogenesis and antioxidative/antistress responses were up-regulated in female-UF. Fructose concentration was increased in female-UF versus male-UF, while glucose levels were similar. In vitro cultures with molecules isolated from male-UF were found to improve male embryo development compared to female embryos cultured with molecules isolated from female-UF. We postulated that, in vivo, male embryos induce changes in the endometrium to help ensure their survival. In contrast, female embryos do not appear to induce these changes.

Glycan evolution in response to collaboration, conflict, and constraint

Glycans, oligo- and polysaccharides secreted or attached to proteins and lipids, cover the surfaces of all cells and have a regulatory capacity and structural diversity beyond any other class of biological molecule. Glycans may have evolved these properties because they mediate cellular interactions and often face pressure to evolve new functions rapidly. We approach this idea two ways. First, we discuss evolutionary innovation. Glycan synthesis, regulation, and mode of chemical interaction influence the spectrum of new forms presented to evolution. Second, we describe the evolutionary conflicts that arise when alleles and individuals interact. Glycan regulation and diversity are integral to these biological negotiations. Glycans are tasked with such an amazing diversity of functions that no study of cellular interaction can begin without considering them. We propose that glycans predominate the cell surface because their physical and chemical properties allow the rapid innovation required of molecules on the frontlines of evolutionary conflict.

Siglec-6 is expressed in gestational trophoblastic disease and affects proliferation, apoptosis and invasion

Sialic acid immunoglobulin-like lectin (Siglec)-6 is a transmembrane receptor that binds leptin. Leptin is an obesity-associated peptide hormone overexpressed in gestational trophoblastic disease (GTD). GTD encompasses several placental abnormalities that range from benign to malignant. Among GTD, molar placentas are characterized by excess proliferation, whereas gestational trophoblastic neoplasias (GTN) have characteristically aggressive invasion. We hypothesized that in GTD, Siglec-6 expression would increase with disease severity and that Siglec-6 and leptin would promote proliferation, inhibit apoptosis and/or promote invasion. Siglec-6 expression patterns were evaluated with particular attention to the diagnostic utility of Siglec-6 in GTD (controls: normal placentas (n=32), hydropic abortus placentas (n=7), non-GTD reproductive tract cancers (n=2); GTD: partial moles (PM; n=11), complete moles (n=24), GTN (n=6)). In normal placentas, Siglec-6 expression dramatically decreased after 8 weeks gestation. Complete molar placentas had significantly higher Siglec-6 expression than controls, but expression was not significantly different from PM. In GTN, Siglec-6 expression was low. These data suggest that Siglec-6 may have diagnostic utility for distinguishing complete moles from normal and hydropic abortus placentas. Functional studies in choriocarcinoma-derived BeWO cells demonstrated a complex interplay between Siglec-6 expression and leptin exposure. In cells lacking Siglec-6, leptin treatment promoted invasion, likely through interaction with LepR leptin receptor, without affecting proliferation or apoptosis. Siglec-6 expression promoted proliferation in a leptin-dependent manner, but protected cells from apoptosis and promoted invasion in a leptin-independent manner. We propose that Siglec-6 and leptin play a role in the aberrant properties characteristic of GTD, namely excess proliferation and invasion.

Glycodelin-A stimulates interleukin-6 secretion by human monocytes and macrophages through L-selectin and the extracellular signal-regulated kinase pathway

Macrophages represent the second major type of decidual leukocytes at the fetomaternal interface. Changes in macrophage number and activity are associated with fetal loss and pregnancy complications. Glycodelin-A (GdA) is an abundant glycoprotein in the first-trimester decidua. It is involved in fetomaternal defense and early placental development through its regulatory activities in various immune cells. The N-glycosylation of GdA mediates the binding and therefore the activities of the molecule. In this study, we studied the biological activities of GdA in the functions of human monocytes/macrophages. GdA was purified from amniotic fluid by affinity chromatography. GdA treatment did not affect the viability, cell death, or phagocytic activity of the monocytes/macrophages. GdA, but not recombinant glycodelin without glycosylation, induced IL-6 production as demonstrated by cytokine array, intracellular staining, and ELISA. GdA also induced phosphorylation of ERK in monocytes/macrophages. The involvement of ERKs in IL-6 induction was confirmed using pharmacological inhibitors. Co-immunoprecipitation showed that L-selectin on the monocytes/macrophages was the binding protein of GdA. Treatment with anti-L-selectin antibody reduced GdA binding and GdA-induced IL-6 production. GdA-treated macrophages suppressed IFN-γ expression by co-cultured T-helper cells in an IL-6-dependent manner. These results show that GdA interacts with L-selectin to induce IL-6 production in monocytes/macrophages by activating the ERK signaling pathway. In turn, the increased IL-6 production suppresses IFN-γ expression in T-helper cells, which may play an important role in inducing a Th-2-polarized cytokine environment that flavors the immunotolerance of the fetoplacental unit.

Decidual endovascular trophoblast invasion in women with polycystic ovary syndrome: an experimental case-control study

CONTEXT

Previous experimental and clinical data suggest impaired decidual trophoblast invasion in patients with polycystic ovarian syndrome (PCOS).

OBJECTIVE

The objective of the study was to test the hypothesis that decidual endovascular trophoblast invasion in pregnant patients with PCOS is impaired and to clarify the potential mechanisms involved.

DESIGN

This was an experimental case-control study.

SETTING

The study was conducted at the academic Departments of Obstetrics and Gynecology and the Unit of Pathology (Italy).

PATIENTS

Forty-five pregnant subjects screened from a wide population of women waiting for legal pregnancy termination were included in the final analysis. Specifically, 15 pregnant patients with PCOS were enrolled as cases and another 30 age- and body mass index (BMI)-matched healthy pregnant women without any feature of PCOS were enrolled as the controls.

INTERVENTION

Interventions included the collection of trophoblastic and decidual tissue at the 12th week of gestation.

MAIN OUTCOME MEASURES

Clinical, ultrasonographic, and biochemical data as well as the histological analysis of decidual endovascular trophoblast invasion.

RESULTS

The rate of implantation site vessels with endovascular trophoblast invasion (ratio between total number of implantation site vessels and total number of vessels with endovascular trophoblast invasion) and the extent of endovascular trophoblast invasion (proportion between immunoreactive areas to cytokeratin 7 and to CD34) were significantly lower in patients with PCOS compared with healthy non-PCOS controls. Endovascular trophoblast invasion data were significantly and indirectly related to the markers of insulin resistance and testosterone concentrations in PCOS patients.

CONCLUSIONS

Pregnant patients with PCOS patients have impaired decidual trophoblast invasion. Further studies are needed to evaluate the exact mechanisms through which insulin resistance and hyperandrogenemia exert this effect.

Activation of JNK/c-Jun is required for the proliferation, survival, and angiogenesis induced by EET in pulmonary artery endothelial cells

Pulmonary artery endothelial plexiform lesion is responsible for pulmonary vascular remodeling (PVR), a basic pathological change of pulmonary arterial hypertension (PAH). Recent evidence suggests that epoxyeicosatrienoic acid (EET), which is derived from arachidonic acid by cytochrome p450 (CYP) epoxygenase, has an essential role in PAH. However, until now, most research has focused on pulmonary vasoconstriction; it is unclear whether EET produces mitogenic and angiogenic effects in pulmonary artery endothelial cells (PAEC). Here we found that 500 nM/l 8,9-EET, 11,12-EET, and 14,15-EET markedly augmented JNK and c-Jun activation in PAECs and that the activation of c-Jun was mediated by JNK, but not the ERK or p38 MPAK pathway. Moreover, treatment with 8,9-EET, 11,12-EET, and 14,15-EET promoted cell proliferation and cell-cycle transition from the G0/G1 phase to S phase and stimulated tube formation in vitro. All these effects were reversed after blocking JNK with Sp600125 (a JNK inhibitor) or JNK1/2 siRNA. In addition, the apoptotic process was alleviated by three EET region isomers through the JNK/c-Jun pathway. These observations suggest that 8,9-EET, 11,12-EET, and 14,15-EET stimulate PAEC proliferation and angiogenesis, as well as protect the cells from apoptosis, via the JNK/c-Jun pathway, an important underlying mechanism that may promote PAEC growth and angiogenesis during PAH.