Pregnancy Galectinology: Insights Into a Complex Network of Glycan Binding Proteins

Modulation of galectin-9 mediated responses in monocytes and T-cells by pregnancy-specific glycoprotein 1

Successful pregnancy relies on a coordinated interplay between endocrine, immune, and metabolic processes to sustain fetal growth and development. The orchestration of these processes involves multiple signaling pathways driving cell proliferation, differentiation, angiogenesis, and immune regulation necessary for a healthy pregnancy. Among the molecules supporting placental development and maternal tolerance, the families of pregnancy-specific glycoproteins and galectins are of great interest in reproductive biology. We previously found that PSG1 can bind to galectin-1 (GAL-1). Herein, we characterized the interaction between PSG1 and other members of the galectin family expressed during pregnancy, including galectin-3, -7, -9, and -13 (GAL-3, GAL-7, GAL-9, and GAL-13). We observed that PSG1 binds to GAL-1, -3, and -9, with the highest apparent affinity seen for GAL-9, and that the interaction of PSG1 with GAL-9 is carbohydrate-dependent. We further investigated the ability of PSG1 to regulate GAL-9 responses in human monocytes, a murine macrophage cell line, and T-cells, and determined whether PSG1 binds to both carbohydrate recognition domains of GAL-9. Additionally, we compared the apparent affinity of GAL-9 binding to PSG1 with other known GAL-9 ligands in these cells, Tim-3 and CD44. Lastly, we explored functional conservation between murine and human PSGs by determining that Psg23, a highly expressed member of the murine Psg family, can bind some murine galectins despite differences in amino acid composition and domain structure.

A Narrative Review on the Pathophysiology of Preeclampsia

Preeclampsia (PE) is a multifactorial pregnancy disorder characterized by hypertension and proteinuria, posing significant risks to both maternal and fetal health. Despite extensive research, its complex pathophysiology remains incompletely understood. This narrative review aims to elucidate the intricate mechanisms contributing to PE, focusing on abnormal placentation, maternal systemic response, oxidative stress, inflammation, and genetic and epigenetic factors. This review synthesizes findings from recent studies, clinical trials, and meta-analyses, highlighting key molecular and cellular pathways involved in PE. The review integrates data on oxidative stress biomarkers, angiogenic factors, immune interactions, and mitochondrial dysfunction. PE is initiated by poor placentation due to inadequate trophoblast invasion and improper spiral artery remodeling, leading to placental hypoxia. This triggers the release of anti-angiogenic factors such as soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), causing widespread endothelial dysfunction and systemic inflammation. Oxidative stress, mitochondrial abnormalities, and immune dysregulation further exacerbate the condition. Genetic and epigenetic modifications, including polymorphisms in the Fms-like tyrosine kinase 1 (FLT1) gene and altered microRNA (miRNA) expression, play critical roles. Emerging therapeutic strategies targeting oxidative stress, inflammation, angiogenesis, and specific molecular pathways like the heme oxygenase-1/carbon monoxide (HO-1/CO) and cystathionine gamma-lyase/hydrogen sulfide (CSE/H2S) pathways show promise in mitigating preeclampsia's effects. PE is a complex disorder with multifactorial origins involving abnormal placentation, endothelial dysfunction, systemic inflammation, and oxidative stress. Despite advances in understanding its pathophysiology, effective prevention and treatment strategies remain limited. Continued research is essential to develop targeted therapies that can improve outcomes for both mothers and their babies.

The Role of Helicobacter pylori and Metabolic Syndrome-Related Mast Cell Activation Pathologies and Their Potential Impact on Pregnancy and Neonatal Outcomes

Helicobacter pylori infection, a significant global burden beyond the gastrointestinal tract, has long been implicated in various systemic pathologies. Rising evidence suggests that the bacterium's intricate relationship with the immune system and its potential to induce chronic inflammation impact diverse pathophysiological processes in pregnant women that may in turn affect the incidence of several adverse pregnancy and neonate outcomes. Helicobacter pylori infection, which has been linked to metabolic syndrome and other disorders by provoking pericyte dysfunction, hyperhomocysteinemia, galectin-3, atrial fibrillation, gut dysbiosis, and mast cell activation pathologies, may also contribute to adverse pregnancy and neonatal outcomes. Together with increasing our biological understanding of the individual and collective involvement of Helicobacter pylori infection-related metabolic syndrome and concurrent activation of mast cells in maternal, fetus, and neonatal health outcomes, the present narrative review may foster related research endeavors to offer novel therapeutic approaches and informed clinical practice interventions to mitigate relevant risks of this critical topic among pregnant women and their offspring.

Placental expression quantitative trait loci in an East Asian population

Expression quantitative trait loci (eQTL) analysis measures the contribution of genetic variation in gene expression on complex traits. Although this methodology has been used to examine gene regulation in numerous human tissues, eQTL research in solid tissues is relatively lacking. We conducted eQTL analysis on placentas collected from an East Asian population in an effort to identify gene regulatory mechanisms in this tissue. Placentas (n = 102) were collected at the time of cesarean delivery. mRNA was extracted, sequenced with NGS, and compared with matched maternal and fetal DNA arrays performed using maternal and neonatal cord blood. Linear regression modeling was performed using tensorQTL. Fine-mapping along with epigenomic annotation was used to select putative functional variants. We identified 2,703 coding genes that contained at least one eQTL with statistical significance (false discovery rate <0.05). After fine-mapping, we found 108 previously unreported eQTL variants with posterior inclusion probability >0.1. Of these, 19% were located in genomic regions with evidence from public placental epigenome suggesting that they may be functionally relevant. For example, variant rs28379289 located in the placenta-specific regulatory region changes the binding affinity of transcription factor leading to higher expression of LGALS3, which is known to affect placental function. This study expands the knowledge base of regulatory elements within the human placenta and identifies 108 previously unreported placenta eQTL signals, which are listed in our publicly available GMI eQTL database. Further studies are needed to identify and characterize genetic regulatory mechanisms that affect placental function in normal pregnancy and placenta-related diseases.

Insights into cAMP-dependent molecular mechanisms regulating expression and function of LGALS16 gene in choriocarcinoma JEG-3 cells

The human choriocarcinoma cell line JEG-3 offers a valuable model to study galectin-16 gene (LGALS16) expression and functions in the context of placental cell differentiation and cancer cell biology. Recent evidence indicates that cAMP-mediated signaling pathways might be responsible for the upregulation of LGALS16; however, the underlying mechanisms are unknown. Here, we employed biochemical inhibitors of the cAMP cascade and CRISPR/Cas9 engineered cells to assess regulatory patterns and associations between cAMP-induced trophoblast differentiation and LGALS16 expression in JEG-3 cells. The expression of LGALS16 was significantly upregulated in parallel with human chorionic gonadotropin beta (CGB), a biomarker of syncytiotrophoblast differentiation, in response to 8-Br-cAMP. Inhibition of p38 MAPK and EPAC significantly altered LGALS16 expression during differentiation, while PKA inhibition failed to change LGALS16 and CGB3/5 expression in our cell model. The CRISPR/Cas9 LGALS16 knockout cell pool expressed a significantly lower amount of CGB3/5, a reduced level of CGB protein, and an unaltered cell growth rate in response to 8-Br-cAMP in comparison with wild-type JEG-3 cells. Collectively, these findings suggest that LGALS16 is required for the trophoblast-like differentiation of JEG-3 cells, and its expression is mediated through p38 MAPK and EPAC signaling pathway branches.

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.

Placental galectins: a subfamily of galectins lose the ability to bind β-galactosides with new structural features†

Galectins are a phylogenetically conserved family of soluble β-galactoside binding proteins. There are 16 different of galectins, each with a specific function determined by its distinct distribution and spatial structure. Galectin-13, galectin-14, and galectin-16 are distinct from other galectin members in that they are primarily found in placental tissue. These galectins, also referred to as placental galectins, play critical roles in regulating pregnancy-associated processes, such as placenta formation and maternal immune tolerance to the embedded embryo. The unique structural characteristics and the inability to bind lactose of placental galectins have recently received significant attention. This review primarily examines the novel structural features of placental galectins, which distinguish them from the classic galectins. Furthermore, it explores the correlation between these structural features and the loss of β-galactoside binding ability. In addition, the newly discovered functions of placental galectins in recent years are also summarized in our review. A detailed understanding of the roles of placental galectins may contribute to the discovery of new mechanisms causing numerous pregnancy diseases and enable the development of new diagnostic and therapeutic strategies for the treatment of these diseases, ultimately benefiting the health of mothers and offspring.

Maternal-derived galectin-1 shapes the placenta niche through Sda terminal glycosylation: Implication for preeclampsia

Placental abnormalities cause impaired fetal growth and poor pregnancy outcome (e.g. preeclampsia [PE]) with long-lasting consequences for the mother and offspring. The molecular dialogue between the maternal niche and the developing placenta is critical for the function of this organ. Galectin-1 (gal-1), a highly expressed glycan-binding protein at the maternal-fetal interface, orchestrates the maternal adaptation to pregnancy and placenta development. Down-regulation or deficiency of gal-1 during pregnancy is associated with the development of PE; however, the maternal- and placental-derived gal-1 contributions to the disease onset are largely unknown. We demonstrate that lack of gal-1 imposes a risk for PE development in a niche-specific manner, and this is accompanied by a placental dysfunction highly influenced by the absence of maternal-derived gal-1. Notably, differential placental glycosylation through the Sda-capped N-glycans dominates the invasive trophoblast capacity triggered by maternal-derived gal-1. Our findings show that gal-1 derived from the maternal niche is essential for healthy placenta development and indicate that impairment of the gal-1 signaling pathway within the maternal niche could be a molecular cause for maternal cardiovascular maladaptation during pregnancy.

Expression and Significance of Galectin-1 and Galectin-3 in the Serum and Placental Tissues of Patients with Intrahepatic Cholestasis of Pregnancy

Background

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disease, usually occurring in the third trimester of pregnancy. Its typical clinical manifestations are itching and elevated serum total bile acid levels, which are more harmful to the fetus, and can lead to a variety of adverse pregnancy outcomes. This paper discusses the expressions of galectin -1 and 3 in the serum and placenta of ICP patients and their relationship with the effect of the incidence of ICP.

Methods

Galectin-1 and 3 in serum and placenta were detected in 22 pregnant women with ICP and 20 healthy pregnant women admitted to the obstetrics Department of Northern Jiangsu People's Hospital from May 2021 to February 2022.

Results

Serum levels of galectin-1 and galectin-3 in ICP pregnant women were significantly higher than those in controls, with significant differences (P<0.05). Placental galectin-1 and 3 were higher in normal pregnant women, and there were statistical differences between groups (P<0.05).

Conclusion

In ICP, the maternal serum and placental galectin-1 and 3 levels were significantly increased, both of which may play an important role in the development of ICP, which may be the initiation factor of ICP pathophysiology, a marker of ICP prediction, and a target of ICP prevention strategies.

A unique maternal and placental galectin signature upon SARS-CoV-2 infection suggests galectin-1 as a key alarmin at the maternal-fetal interface

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic imposed a risk of infection and disease in pregnant women and neonates. Successful pregnancy requires a fine-tuned regulation of the maternal immune system to accommodate the growing fetus and to protect the mother from infection. Galectins, a family of β-galactoside-binding proteins, modulate immune and inflammatory processes and have been recognized as critical factors in reproductive orchestration, including maternal immune adaptation in pregnancy. Pregnancy-specific glycoprotein 1 (PSG1) is a recently identified gal-1 ligand at the maternal-fetal interface, which may facilitate a successful pregnancy. Several studies suggest that galectins are involved in the immune response in SARS-CoV-2-infected patients. However, the galectins and PSG1 signature upon SARS-CoV-2 infection and vaccination during pregnancy remain unclear. In the present study, we examined the maternal circulating levels of galectins (gal-1, gal-3, gal-7, and gal-9) and PSG1 in pregnant women infected with SARS-CoV-2 before vaccination or uninfected women who were vaccinated against SARS-CoV-2 and correlated their expression with different pregnancy parameters. SARS-CoV-2 infection or vaccination during pregnancy provoked an increase in maternal gal-1 circulating levels. On the other hand, levels of PSG1 were only augmented upon SARS-CoV-2 infection. A healthy pregnancy is associated with a positive correlation between gal-1 concentrations and gal-3 or gal-9; however, no correlation was observed between these lectins during SARS-CoV-2 infection. Transcriptome analysis of the placenta showed that gal-1, gal-3, and several PSG and glycoenzymes responsible for the synthesis of gal-1-binding glycotopes (such as linkage-specific N-acetyl-glucosaminyltransferases (MGATs)) are upregulated in pregnant women infected with SARS-CoV-2. Collectively, our findings identify a dynamically regulated "galectin-specific signature" that accompanies the SARS-CoV-2 infection and vaccination in pregnancy, and they highlight a potentially significant role for gal-1 as a key pregnancy protective alarmin during virus infection.

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.

A Comparative Review of Pregnancy and Cancer and Their Association with Endoplasmic Reticulum Aminopeptidase 1 and 2

The fundamental basis of pregnancy and cancer is to determine the fate of the survival or the death of humanity. However, the development of fetuses and tumors share many similarities and differences, making them two sides of the same coin. This review presents an overview of the similarities and differences between pregnancy and cancer. In addition, we will also discuss the critical roles that Endoplasmic Reticulum Aminopeptidase (ERAP) 1 and 2 may play in the immune system, cell migration, and angiogenesis, all of which are essential for fetal and tumor development. Even though the comprehensive understanding of ERAP2 lags that of ERAP1 due to the lack of an animal model, recent studies have shown that both enzymes are associated with an increased risk of several diseases, including pregnancy disorder pre-eclampsia (PE), recurrent miscarriages, and cancer. The exact mechanisms in both pregnancy and cancer need to be elucidated. Therefore, a deeper understanding of ERAP's role in diseases can make it a potential therapeutic target for pregnancy complications and cancer and offer greater insight into its impact on the immune system.

Galectin-1 Used in Assisted Reproduction-Embryo Safety and Toxicology Studies

Galectin-1 has been cited as a mediator involved in preventing early embryonic death in mammals and is implicated in maternal-fetal tolerance. Galectin-1 is also a reasonable tool to improve fertility in assisted reproduction procedures. As recommended in the ICH guidelines (S5-R2 and S6-R1) and based on bioethical concerns, we chose bovine embryos (BE) to assess in vitro embryo development as part of a larger reproductive safety and toxicology study in progress. The design considered in vitro embryo development using rHGAL-1 supplementations (in three different concentrations) of the in vitro embryo culture (IVP) media. Based on procedures for the commercial in vitro production of BE using oocytes aspirated from slaughterhouse ovaries, rHGAL-1 supplementation was performed in two experiments: In Experiment 1 on oocyte maturation, involving IVM medium supplementation, and in Experiment 2 on culture step IVC, involving supplementation with an SOF medium. IVP commercial procedures were used, with three IVP replicates per experiment, and the oocytes we distributed into four groups of treatment (one control group and three different dosages of rHGAL-1 to supplement both IVM and SOF media using 2, 20, and 40 µg·mL-1, respectively. A total of 967 (Experiment 1) and 1213 (Experiment 2) oocytes were aspirated and submitted to the IVP procedure. There was no damage to the in vitro bovine embryo growth when considering cleavage percentage (%CLE), blastocyst development (Bl, Bx, Bh, and B) at Days 7 and 8, or an amount of rHGAL-1 supplementation ≤20 µg·mL-1. The immunohistochemistry assay with D8 embryos cultivated using rHGAL-1 supplementation on the culture medium (SOF medium) demonstrated the presence of exogenous GAL-1 distributed in mass cell and trophoblastic cells, and the profile observed was dependent on exogenous supplementation, which was most evident in hatched embryos. The findings confirmed the use of a reasonable amount of rHGAL-1 for in vitro embryonic development and would make the use of rHGAL-1 in assisted reproduction in humans more reliable and safer. Even though it was not the objective of the study, we verified that supplementation with 2 µg·mL-1 significantly improved some of the evaluated parameters of embryonic development (%BlD7, %BD7, %BlD8, %BhD8, and %BD8).

Placental galectins regulate innate and adaptive immune responses in pregnancy

Introduction

Galectins are master regulators of maternal immune responses and placentation in pregnancy. Galectin-13 (gal-13) and galectin-14 (gal-14) are expressed solely by the placenta and contribute to maternal-fetal immune tolerance by inducing the apoptosis of activated T lymphocytes and the polarization of neutrophils toward an immune-regulatory phenotype.Furthermore, their decreased placental expression is associated with pregnancy complications, such as preeclampsia and miscarriage. Yet, our knowledge of the immunoregulatory role of placental galectins is incomplete.

Methods

This study aimed to investigate the effects of recombinant gal-13 and gal-14 on cell viability, apoptosis, and cytokine production of peripheral blood mononuclear cells (PBMCs) and the signaling pathways involved.

Results

Herein, we show that gal-13 and gal-14 bind to the surface of non-activated PBMCs (monocytes, natural killer cells, B cells, and T cells) and increase their viability while decreasing the rate of their apoptosis without promoting cell proliferation. We also demonstrate that gal-13 and gal-14 induce the production of interleukin (IL)-8, IL-10, and interferon-gamma cytokines in a concentration-dependent manner in PBMCs. The parallel activation of Erk1/2, p38, and NF-ĸB signaling evidenced by kinase phosphorylation in PBMCs suggests the involvement of these pathways in the regulation of the galectin-affected immune cell functions.

Discussion

These findings provide further evidence on how placenta-specific galectins assist in the establishment and maintenance of a proper immune environment during a healthy pregnancy.

Glycoconjugates: Synthesis, Functional Studies, and Therapeutic Developments

Glycoconjugates are major constituents of mammalian cells that are formed via covalent conjugation of carbohydrates to other biomolecules like proteins and lipids and often expressed on the cell surfaces. Among the three major classes of glycoconjugates, proteoglycans and glycoproteins contain glycans linked to the protein backbone via amino acid residues such as Asn for N-linked glycans and Ser/Thr for O-linked glycans. In glycolipids, glycans are linked to a lipid component such as glycerol, polyisoprenyl pyrophosphate, fatty acid ester, or sphingolipid. Recently, glycoconjugates have become better structurally defined and biosynthetically understood, especially those associated with human diseases, and are accessible to new drug, diagnostic, and therapeutic developments. This review describes the status and new advances in the biological study and therapeutic applications of natural and synthetic glycoconjugates, including proteoglycans, glycoproteins, and glycolipids. The scope, limitations, and novel methodologies in the synthesis and clinical development of glycoconjugates including vaccines, glyco-remodeled antibodies, glycan-based adjuvants, glycan-specific receptor-mediated drug delivery platforms, etc., and their future prospectus are discussed.

Galectokines: The Promiscuous Relationship between Galectins and Cytokines

Galectins, a family of glycan-binding proteins, are well-known for their role in shaping the immune microenvironment. They can directly affect the activity and survival of different immune cell subtypes. Recent evidence suggests that galectins also indirectly affect the immune response by binding to members of another immunoregulatory protein family, i.e., cytokines. Such galectin-cytokine heterodimers, here referred to as galectokines, add a new layer of complexity to the regulation of immune homeostasis. Here, we summarize the current knowledge with regard to galectokine formation and function. We describe the known and potential mechanisms by which galectokines can help to shape the immune microenvironment. Finally, the outstanding questions and challenges for future research regarding the role of galectokines in immunomodulation are discussed.

Effect of a Single Intrauterine Dose of Human Recombinant Galectin-1 Buffered on Pregnancy Rate in Inseminated Cows

The objective was to evaluate the efficacy of a single dose of exogenous galectin-1 in improving the pregnancy rate in inseminated cows, comparing the pregnancy rate of the two groups (treatment and control Groups) into 107 contemporary groups (YG) established. An ultrasound exam determined the pregnancy rate performed 25 to 35 days after the fixed-time artificial insemination (FTAI) of breeding beef cows (n = 3469). The pregnancy rate of cows that received a single dose of eGAL-1 (200 ± 10 µg), with an intrauterine administration (n = 1901), was compared with the pregnancy rate of cows inseminated using a conventional AI protocol (n = 1568), both comparing into the same YG. YGs were created considering the grouping of cows belonging to the same farm, with the same nutritional score and management, inseminated by the same inseminator and semen batch, and using the same estrus synchronization protocol). The statistical method used calculated the probability of obtaining pregnancy within each group. The administration of a single dose of eGAL-1 can increase the probability of obtaining pregnancy in beef cows by up to 8.68% (p < 0.0001), suggesting that a single dose of eGAL-1 during the FTAI procedure was reasonable in the beef cattle AI routine and can improve the pregnancy rate considerably.

Immunobiology of Gestational Diabetes Mellitus in Post-Medawar Era

Although the concepts related to fetal immune tolerance proposed by Sir Peter Medawar in the 1950s have not withstood the test of time, they revolutionized our current understanding of the immunity at the maternal-fetal interface. An important extension of the original Medawar paradigm is the investigation into the underlying mechanisms for adverse pregnancy outcomes, including recurrent spontaneous abortion, preterm birth, preeclampsia and gestational diabetes mellitus (GDM). Although a common pregnancy complication with systemic symptoms, GDM still lacks understanding of immunological perturbations associated with the pathological processes, particularly at the maternal-fetal interface. GDM has been characterized by low grade systemic inflammation that exacerbates maternal immune responses. In this regard, GDM may also entail mild autoimmune pathology by dysregulating circulating and uterine regulatory T cells (Tregs). The aim of this review article is to focus on maternal-fetal immunological tolerance phenomenon and discuss how local or systemic inflammation has been programmed in GDM. Specifically, this review addresses the following questions: Does the inflammatory or exhausted Treg population affecting the Th17:Treg ratio lead to the propensity of a pro-inflammatory environment? Do glycans and glycan-binding proteins (mainly galectins) contribute to the biology of immune responses in GDM? Our understanding of these important questions is still elementary as there are no well-defined animal models that mimic all the features of GDM or can be used to better understand the mechanistic underpinnings associated with this common pregnancy complication. In this review, we will leverage our preliminary studies and the literature to provide a conceptualized discussion on the immunobiology of GDM.

Medawar's PostEra: Galectins Emerged as Key Players During Fetal-Maternal Glycoimmune Adaptation

Lectin-glycan interactions, in particular those mediated by the galectin family, regulate many processes required for a successful pregnancy. Over the past decades, increasing evidence gathered from in vitro and in vivo experiments indicate that members of the galectin family specifically bind to both intracellular and membrane bound carbohydrate ligands regulating angiogenesis, immune-cell adaptations required to tolerate the fetal semi-allograft and mammalian embryogenesis. Therefore, galectins play important roles in fetal development and placentation contributing to maternal and fetal health. This review discusses the expression and role of galectins during the course of pregnancy, with an emphasis on maternal immune adaptions and galectin-glycan interactions uncovered in the recent years. In addition, we summarize the galectin fingerprints associated with pathological gestation with particular focus on preeclampsia.

Self-Centered Function of Adaptive Immunity in Regulation of Immune Responses and in Tolerance

The search for common mechanisms underlying the pathogenesis of chronic inflammatory conditions has crystalized the concept of continuous dual resetting of the immune repertoire (CDR) as a basic principle of the immune system function. Consequently, outlined was the first dynamic comprehensive picture of the immune system function. The goal of this study is to elaborate on regulation of immune responses and mechanisms of tolerance, particularly focusing on adaptive immunity. It is well established that the T/B cell repertoire is selected and maintained based on interactions with self. However, their activation also requires interaction with a self-specific major histocompatibility complex (MHC) “code,” i.e., the context of MHC molecules. Therefore, not only repertoire selection and maintenance but also the T/B cell activation and function are self-centered. Thus, adaptive effectors may be primarily focused on the state of self and maintenance of integrity of the self, and only to a certain degree on elimination of the foreign. As examples of such function are used immunologically poorly understood MHC-disparate settings typical for transplantation and pregnancy. Transplantation represents an extreme setting of strong systemic compartment-level adaptive/MHC-restricted immune responses. Described are clinically identified conditions for operational tolerance of MHC-disparate tissues/living systems in allotransplantation, which are in line with the CDR-proposed self-centered regulatory role of T/B cells. In contrast, normal pregnancy is coexistence of semiallogeneic or entirely allogeneic mother and fetus, but without alloreactivity akin to transplantation settings. Presented data support the notion that maintenance of pregnancy is a process that relies predominantly on innate/MHC-independent immune mechanisms. By the inception of hemotrophic stage of pregnancy (second and third trimester), both mother and child are individual living systems, with established adaptive immune repertoires. Although mother-fetus interactions at that point become indirect systemic compartment-level communications, their interactions throughout gestation remain within the innate realm of molecular-level adaptations.

Galectins in Early Pregnancy and Pregnancy-Associated Pathologies

Galectins are a family of conserved soluble proteins defined by an affinity for β-galactoside structures present on various glycoconjugates. Over the past few decades, galectins have been recognized as important factors for successful implantation and maintenance of pregnancy. An increasing number of studies have demonstrated their involvement in trophoblast cell function and placental development. In addition, several lines of evidence suggest their important roles in feto-maternal immune tolerance regulation and angiogenesis. Changed or dysregulated galectin expression is also described in pregnancy-related disorders. Although the data regarding galectins' clinical relevance are still at an early stage, evidence suggests that some galectin family members are promising candidates for better understanding pregnancy-related pathologies, as well as predicting biomarkers. In this review, we aim to summarize current knowledge of galectins in early pregnancy as well as in pregnancy-related pathologies.

Expression, Regulation, and Functions of the Galectin-16 Gene in Human Cells and Tissues

Galectins comprise a family of soluble β-galactoside-binding proteins, which regulate a variety of key biological processes including cell growth, differentiation, survival, and death. This paper aims to address the current knowledge on the unique properties, regulation, and expression of the galectin-16 gene (LGALS16) in human cells and tissues. To date, there are limited studies on this galectin, with most focusing on its tissue specificity to the placenta. Here, we report the expression and 8-Br-cAMP-induced upregulation of LGALS16 in two placental cell lines (BeWo and JEG-3) in the context of trophoblastic differentiation. In addition, we provide the results of a bioinformatics search for LGALS16 using datasets available at GEO, Human Protein Atlas, and prediction tools for relevant transcription factors and miRNAs. Our findings indicate that LGALS16 is detected by microarrays in diverse human cells/tissues and alters expression in association with cancer, diabetes, and brain diseases. Molecular mechanisms of the transcriptional and post-transcriptional regulation of LGALS16 are also discussed based on the available bioinformatics resources.

Galectin-1 Confers Endometrial Gene Expression and Protein Related to Maternal-Conceptus Immune Tolerance in Cattle

Conceptus secretory factors include galectins, a family of carbohydrate binding proteins that elicit cell adhesion and immune suppression by interacting with intracellular and extracellular glycans. In rodents, galectin-1 (LGALS1) promotes maternal-fetal immune tolerance in the decidua through expansion of tolerogenic CD11c+ dendritic cells, increased anti-inflammatory IL-10, and activation of FOXP3+ regulatory T cells (Treg). This study characterized galectin expression in early ruminant conceptuses and endometrium. We also tested the effect of recombinant bovine LGALS1 (rbLGALS1) and progesterone (P4) on endometrial expression of genes and protein related to maternal-fetal immune tolerance in cattle. Elongating bovine and ovine conceptuses expressed several galectins, particularly, LGALS1, LGALS3 and LGALS8. Within bovine endometrium, expression of LGALS3, LGALS7 and LGALS9 was greater on Day 16 of pregnancy compared to the estrous cycle. Within ovine endometrium, LGALS7 was greater during pregnancy compared to the estrous cycle and endometrium of pregnant sheep tended to have greater LGALS9 and LGALS15. Expression of endometrial LGALS4 was less during pregnancy in sheep. Treating bovine endometrium with rbLGALS1 increased endometrial expression of CD11c, IL-10 and FOXP3, within 24 h. Specifically, within caruncular endometrium, both rbLGALS1 and P4 increased FOXP3, suggesting that both ligands may promote Treg expansion. Using IHC, FOXP3+ cells with a leukocyte phenotype were localized to the bovine uterine stratum compactum near the uterine surface and increased in response to rbLGALS1. We hypothesize that galectins have important functions during establishment of pregnancy in ruminants and bovine conceptus LGALS1 and luteal P4 confer mechanisms of maternal-conceptus immune tolerance in cattle.

Placental Glycoredox Dysregulation Associated with Disease Progression in an Animal Model of Superimposed Preeclampsia

Pregnancies carried by women with chronic hypertension are at increased risk of superimposed preeclampsia, but the placental pathways involved in disease progression remain poorly understood. In this study, we used the stroke-prone spontaneously hypertensive rat (SHRSP) model to investigate the placental mechanisms promoting superimposed preeclampsia, with focus on cellular stress and its influence on galectin-glycan circuits. Our analysis revealed that SHRSP placentas are characterized by a sustained activation of the cellular stress response, displaying significantly increased levels of markers of lipid peroxidation (i.e., thiobarbituric acid reactive substances (TBARS)) and protein nitration and defective antioxidant enzyme expression as early as gestation day 14 (which marks disease onset). Further, lectin profiling showed that such redox imbalance was associated with marked alterations of the placental glycocode, including a prominent decrease of core 1 O-glycan expression in trophoblasts and increased decidual levels of sialylation in SHRSP placentas. We also observed significant changes in the expression of galectins 1, 3 and 9 with pregnancy progression, highlighting the important role of the galectin signature as dynamic interpreters of placental microenvironmental challenges. Collectively, our findings uncover a new role for the glycoredox balance in the pathogenesis of superimposed preeclampsia representing a promising target for interventions in hypertensive disorders of pregnancy.

Targeted disruption of galectin 3 in mice delays the first wave of spermatogenesis and increases germ cell apoptosis

Galectin 3 is a multifunctional lectin implicated in cellular proliferation, differentiation, adhesion, and apoptosis. This lectin is broadly expressed in testicular somatic cells and germ cells, and is upregulated during testicular development. Since the role of galectin 3 in testicular function remains elusive, we aimed to characterize the role of galectin 3 in testicular physiology. We found that galectin 3 transgenic mice (Lgals3-/-) exhibited significantly decreased testicular weight in adulthood compared to controls. The transgenic mice also exhibited a delay to the first wave of spermatogenesis, a decrease in the number of germ cells at postnatal day 5 (P5) and P15, and defective Sertoli cell maturation. Mechanistically, we found that Insulin-like-3 (a Leydig cell marker) and enzymes involved in steroid biosynthesis were significantly upregulated in adult Lgals3-/- testes. These observations were accompanied by increased serum testosterone levels. To determine the underlying causes of the testicular atrophy, we monitored cellular apoptosis. Indeed, adult Lgals3-/- testicular cells exhibited an elevated apoptosis rate that is likely driven by downregulated Bcl-2 and upregulated Bax and Bak expression, molecules responsible for live/death cell balance. Moreover, the percentage of testicular macrophages within CD45+ cells was decreased in Lgals3-/- mice. These data suggest that galectin 3 regulates spermatogenesis initiation and Sertoli cell maturation in part, by preventing germ cells from undergoing apoptosis and regulating testosterone biosynthesis. Going forward, understanding the role of galectin 3 in testicular physiology will add important insights into the factors governing the development of germ cells and steroidogenesis and delineate novel biomarkers of testicular function.

Galectin-14 Promotes Trophoblast Migration and Invasion by Upregulating the Expression of MMP-9 and N-Cadherin

Galectin-14 is specifically expressed in placental trophoblasts, and its expression is reduced in trophoblasts retrieved from the cervix of women destined to develop early pregnancy loss. However, the roles of galectin-14 in regulating trophoblasts and in the pathogenesis of pregnancy complication have never been investigated. In the current research, we aimed to investigate the roles of galectin-14 in the regulation of trophoblasts. Tissues of the placenta and villi were collected. Primary trophoblasts and human trophoblast cell line HTR-8/SVneo were used. Western blotting and RT-PCR were used to quantify gene expression. The siRNA-mediated galectin-14 knockdown and lentivirus-mediated overexpression were performed to manipulate the gene expression in trophoblasts. Transwell migration and invasion assays were used to evaluate cell migration and invasion capacity. Gelatin zymography was used to determine the gelatinase activity. Galectin-14 was significantly decreased in the villi of early pregnancy loss and the placenta of preeclampsia. Knockdown of galectin-14 in primary trophoblasts inhibited cell migration and invasion, downregulated the expression of matrix metalloproteinase (MMP)-9 and N-cadherin, the activity of MMP-9, and decreased the phosphorylation of Akt. Meanwhile, the overexpression of galectin-14 in HTR-8/SVneo promoted cell migration and invasion, upregulated the expression of MMP-9 and N-cadherin, the activity of MMP-9, and increased the phosphorylation of Akt. Increased Akt phosphorylation promoted cell migration and invasion and upregulated the expression and activity of MMP-9, while decreased Akt phosphorylation inhibited cell migration and invasion and downregulated the expression and activity of MMP-9. Thus, galectin-14 promotes trophoblast migration and invasion by enhancing the expression of MMP-9 and N-cadherin through Akt phosphorylation. The dysregulation of galectin-14 is involved in the pathogenesis of early pregnancy loss and preeclampsia.

Examining Sex Differences in the Human Placental Transcriptome During the First Fetal Androgen Peak

Sex differences in human placenta exist from early pregnancy to term, however, it is unclear whether these differences are driven solely by sex chromosome complement or are subject to differential sex hormonal regulation. Here, we survey the human chorionic villus (CV) transcriptome for sex-linked signatures from 11 to 16 gestational weeks, corresponding to the first window of increasing testis-derived androgen production in male fetuses. Illumina HiSeq RNA sequencing was performed on Lexogen Quantseq 3' libraries derived from CV biopsies (n = 11 females, n = 12 males). Differential expression (DE) was performed to identify sex-linked transcriptional signatures, followed by chromosome mapping, pathway analysis, predicted protein interaction, and post-hoc linear regressions to identify transcripts that trend over time. We observe 322 transcripts DE between male and female CV from 11 to 16 weeks, with 22 transcripts logFC > 1. Contrary to our predictions, the difference between male and female expression of DE autosomal genes was more pronounced at the earlier gestational ages. In females, we found selective upregulation of extracellular matrix components, along with a number of X-linked genes. In males, DE transcripts centered on chromosome 19, with mitochondrial, immune, and pregnancy maintenance-related transcripts upregulated. Among the highest differentially expressed autosomal genes were CCRL2, LGALS13, and LGALS14, which are known to regulate immune cell interactions. Our results provide insight into sex-linked gene expression in late first and early second trimester developing human placenta and lay the groundwork to understand the mechanistic origins of sex differences in prenatal development.

Galectin-1 production is elevated in hypertrophic scar

Upon healing, burn wounds often leave hypertrophic scars (HTSs) marked by excess collagen deposition, dermal and epidermal thickening, hypervascularity, and an increased density of fibroblasts. The Galectins, a family of lectins with a conserved carbohydrate recognition domain, function intracellularly and extracellularly to mediate a multitude of biological processes including inflammatory responses, angiogenesis, cell migration and differentiation, and cell-ECM adhesion. Galectin-1 (Gal-1) has been associated with several fibrotic diseases and can induce keratinocyte and fibroblast proliferation, migration, and differentiation into fibroproliferative myofibroblasts. In this study, Gal-1 expression was assessed in human and porcine HTS. In a microarray, galectins 1, 4, and 12 were upregulated in pig HTS compared to normal skin (fold change = +3.58, +6.11, and +3.03, FDR <0.01). Confirmatory qRT-PCR demonstrated significant upregulation of Galectin-1 (LGALS1) transcription in HTS in both human and porcine tissues (fold change = +7.78 and +7.90, P <.05). In pig HTS, this upregulation was maintained throughout scar development and remodeling. Immunofluorescent staining of Gal-1 in human and porcine HTS showed significantly increased fluorescence (202.5 ± 58.2 vs 35.2 ± 21.0, P <.05 and 276.1 ± 12.7 vs 69.7 ± 25.9, P <.01) compared to normal skin and co-localization with smooth muscle actin-expressing myofibroblasts. A strong positive correlation (R = .948) was observed between LGALS1 and Collagen type 1 alpha 1 mRNA expression. Gal-1 is overexpressed in HTS at the mRNA and protein levels and may have a role in the development of scar phenotypes due to fibroblast over-proliferation, collagen secretion, and dermal thickening. The role of galectins shows promise for future study and may lead to the development of a pharmacotherapy for treatment of HTS.

Human galectin-16 has a pseudo ligand binding site and plays a role in regulating c-Rel-mediated lymphocyte activity

BACKGROUND

The structure of human galectin-16 (Gal-16) has yet to be solved, and its function has remained elusive.

METHODS

X-ray crystallography was used to determine the atomic structures of Gal-16 and two of its mutants. The Gal-16 oligomer state was investigated by gel filtration, its hemagglutination activity was determined along with its ability to bind lactose using ITC. The cellular distribution of EGFP-tagged Gal-16 in various cell lines was also investigated, and the interaction between Gal-16 and c-Rel was assessed by pull-down studies, microscale thermophoresis and immunofluorescence.

RESULTS

Unlike other galectins, Gal-16 lacks the ability to bind the β-galactoside lactose. Lactose binding could be regained by replacing an arginine (Arg55) with asparagine, as shown in the crystal structures of two lactose-loaded Gal-16 mutants (R55N and R55N/H57R). Gal-16 was also shown to be monomeric by gel filtration, as well as in crystal structures. Thus, this galectin could not induce erythrocyte agglutination. EGFP-tagged Gal-16 was found to be localized mostly in the nucleus of various cell types, and can interact with c-Rel, a member of NF-κB family.

CONCLUSIONS

Gal-16 exists as a monomer and its ligand binding is significantly different from that of other prototype galectins, suggesting that it has a novel function(s). The interaction between Gal-16 and c-Rel indicates that Gal-16 may regulate signal transduction pathways via the c-Rel hub in B or T cells at the maternal-fetal interface.

GENERAL SIGNIFICANCE

The present study lays the foundation for further studies into the cellular and physiological functions of Gal-16.

Immune cells in normal pregnancy and gestational trophoblastic diseases

A healthy pregnancy requires the development of maternal-fetal immune tolerance against the semi-allogeneic fetus. The interactions between the trophoblastic cells and the maternal immune cells (p.e., natural killer cells, T cells, macrophages, dendritic cells and B-cells) are important for the development of the maternal-fetal immune tolerance and the placental growth and function. These interactions are mediated by cell to cell contact and secreted molecules such as cytokines, chemokines, angiogenic factors and growth factors. The maternal immune cells are present in normal non-pregnant and pregnant endometrium and there are several lines of evidence based on immunohistochemical and RNA sequencing data that the decidual immune cells and immune-related pathways display alterations in GTD, which may have pathogenetic and clinical significance. The present review focuses on the usefulness of the immunohistochemical analysis which provides multiparametric in situ information regarding the numbers, the immunophenotypes and the immunotopographical distributions of the decidual immune cells in tissue sections from normal pregnancy and GTD. We also discuss the significance of the immunohistochemical information in order to gain insight in the putative mechanisms explaining the alterations of the decidual immune cells in GTD and the potential implications of these alterations in the pathogenesis and the clinical behavior of GTD.

Galectin-mediated immune recognition: Opsonic roles with contrasting outcomes in selected shrimp and bivalve mollusk species

Galectins are a structurally conserved family of ß-galactoside-binding lectins characterized by a unique sequence motif in the carbohydrate recognition domain, and of wide taxonomic distribution, from fungi to mammals. Their biological functions, initially described as key to embryogenesis and early development via recognition of endogenous ("self") carbohydrate moieties, are currently understood as also encompassing tissue repair, cancer metastasis, angiogenesis, adipogenesis, and regulation of immune homeostasis. More recently, however, numerous studies have contributed to establish a new paradigm by revealing that galectins can also bind to exogenous ("non-self") glycans on the surface of potentially pathogenic virus, bacteria, and eukaryotic parasites, and function both as pathogen recognition receptors (PRRs) and effector factors in innate immunity. Our studies on a galectin from the kuruma shrimp Marsupenaeus japonicus (MjGal), revealed that it functions as a typical PRR. Expression of MjGal is upregulated by infectious challenge, and can recognize both Gram (+) and Gram (-) bacteria. MjGal also recognizes carbohydrates on the shrimp hemocyte surface, and can cross-link microbial pathogens to the hemocytes, promoting their phagocytosis and clearance from circulation. Therefore, MjGal contributes to the shrimp's immune defense against infectious challenge both as a PRR and effector factor. Our studies on galectins from the bivalve mollusks, however, have shown that although they can function in immune defense as MjGal, protistan parasites take advantage of the recognition roles of the host galectins, for successful attachment and host infection. We identified in the eastern oyster Crassostrea virginica two galectins (CvGal1 and CvGal2) that not only recognize a large variety of bacterial species, but also the protozoan parasite Perkinsus marinus. Like the shrimp MjGal, both oyster galectins function as opsonins, and promote parasite adhesion and phagocytosis. However, P. marinus survives intrahemocytic oxidative killing and proliferates, eventually causing systemic infection and death of the oyster host. In the softshell clam Mya arenaria we identified a galectin (MaGal1) that displays carbohydrate specificity and recognition properties for sympatric Perkinsus species (P. marinus and P. chesapeaki), that are different from CvGal1 and CvGal2. Our results suggest that although galectins from bivalves can function as PRRs, Perkinsus parasites have co-evolved with their hosts to subvert the galectins' immune functions for host infection by acquisition of carbohydrate-based mimicry.

Altered Glycosylation Contributes to Placental Dysfunction Upon Early Disruption of the NK Cell-DC Dynamics

Immune cells [e. g., dendritic cells (DC) and natural killer (NK) cells] are critical players during the pre-placentation stage for successful mammalian pregnancy. Proper placental and fetal development relies on balanced DC-NK cell interactions regulating immune cell homing, maternal vascular expansion, and trophoblast functions. Previously, we showed that in vivo disruption of the uterine NK cell-DC balance interferes with the decidualization process, with subsequent impact on placental and fetal development leading to fetal growth restriction. Glycans are essential determinants of reproductive health and the glycocode expressed in a particular compartment (e.g., placenta) is highly dependent on the cell type and its developmental and pathological state. Here, we aimed to investigate the maternal and placental glycovariation during the pre- and post-placentation period associated with disruption of the NK cell-DC dynamics during early pregnancy. We observed that depletion of NK cells was associated with significant increases of O- and N-linked glycosylation and sialylation in the decidual vascular zone during the pre-placental period, followed by downregulation of core 1 and poly-LacNAc extended O-glycans and increased expression of branched N-glycans affecting mainly the placental giant cells and spongiotrophoblasts of the junctional zone. On the other hand, expansion of DC induced a milder increase of Tn antigen (truncated form of mucin-type O-glycans) and branched N-glycan expression in the vascular zone, with only modest changes in the glycosylation pattern during the post-placentation period. In both groups, this spatiotemporal variation in the glycosylation pattern of the implantation site was accompanied by corresponding changes in galectin-1 expression. Our results show that pre- and post- placentation implantation sites have a differential glycopattern upon disruption of the NK cell-DC dynamics, suggesting that immune imbalance early in gestation impacts placentation and fetal development by directly influencing the placental glycocode.

Role of galectin-glycan circuits in reproduction: from healthy pregnancy to preterm birth (PTB)

Growing evidence suggests that galectins, an evolutionarily conserved family of glycan-binding proteins, fulfill key roles in pregnancy including blastocyst implantation, maternal-fetal immune tolerance, placental development, and maternal vascular expansion, thereby establishing a healthy environment for the growing fetus. In this review, we comprehensively present the function of galectins in shaping cellular circuits that characterize a healthy pregnancy. We describe the current understanding of galectins in term and preterm labor and discuss how the galectin-glycan circuits contribute to key immunological pathways sustaining maternal tolerance and preventing microbial infections. A deeper understanding of the glycoimmune pathways regulating early events in preterm birth could offer the broader translational potential for the treatment of this devastating syndrome.

Glycan characterization of pregnancy-specific glycoprotein 1 and its identification as a novel Galectin-1 ligand

Pregnancy-specific beta 1 glycoprotein (PSG1) is secreted from trophoblast cells of the human placenta in increasing concentrations as pregnancy progresses, becoming one of the most abundant proteins in maternal serum in the third trimester. PSG1 has seven potential N-linked glycosylation sites across its four domains. We carried out glycomic and glycoproteomic studies to characterize the glycan composition of PSG1 purified from serum of pregnant women and identified the presence of complex N-glycans containing poly LacNAc epitopes with α2,3 sialyation at four sites. Using different techniques, we explored whether PSG1 can bind to galectin-1 (Gal-1) as these two proteins were previously shown to participate in processes required for a successful pregnancy. We confirmed that PSG1 binds to Gal-1 in a carbohydrate-dependent manner with an affinity of the interaction of 0.13 μM. In addition, we determined that out of the three N-glycosylation-carrying domains, only the N and A2 domains of recombinant PSG1 interact with Gal-1. Lastly, we observed that the interaction between PSG1 and Gal-1 protects this lectin from oxidative inactivation and that PSG1 competes the ability of Gal-1 to bind to some but not all of its glycoprotein ligands.

Oncofetal Chondroitin Sulfate: A Putative Therapeutic Target in Adult and Pediatric Solid Tumors

Solid tumors remain a major challenge for targeted therapeutic intervention strategies such as antibody-drug conjugates and immunotherapy. At a minimum, clear and actionable solid tumor targets have to comply with the key biological requirement of being differentially over-expressed in solid tumors and metastasis, in contrast to healthy organs. Oncofetal chondroitin sulfate is a cancer-specific secondary glycosaminoglycan modification to proteoglycans expressed in a variety of solid tumors and metastasis. Normally, this modification is found to be exclusively expressed in the placenta, where it is thought to facilitate normal placental implantation during pregnancy. Informed by this biology, oncofetal chondroitin sulfate is currently under investigation as a broad and specific target in solid tumors. Here, we discuss oncofetal chondroitin sulfate as a potential therapeutic target in childhood solid tumors in the context of current knowhow obtained over the past five years in adult cancers.

Endometrial Cancer Immune Escape Mechanisms: Let Us Learn From the Fetal-Maternal Interface

The immune escape mechanisms at the base of tumor progression in endometrial cancer mimic immune tolerance mechanisms occurring at the maternal-fetal interface. The biological and immunological processes behind the maternal-fetal interface are finely tuned in time and space during embryo implantation and subsequent pregnancy stages; conversely, those behind cancer progression are often aberrant. The environment composition at the maternal-fetal interface parallels the pro-tumor microenvironment identified in many cancers, pointing to the possibility for the use of the maternal-fetal interface as a model to depict immune therapeutic targets in cancer. The framework of cancer environment signatures involved in immune adaptations, precisely timed in cancer progression, could reveal a specific "immune clock" in endometrial cancer, which might guide clinicians in patient risk class assessment, diagnostic workup, management, surgical and therapeutic approach, and surveillance strategies. Here, we review studies approaching this hypothesis, focusing on what is known so far about oncofetal similarities in immunity with the idea to individualize personalized immunotherapy targets, through the downregulation of the immune escape stage or the reactivation of the pro-inflammatory processes suppressed by the tumor.

Galectins in Host-Pathogen Interactions: Structural, Functional and Evolutionary Aspects

Galectins are a family of ß-galactoside-binding lectins characterized by a unique sequence motif in the carbohydrate recognition domain, and evolutionary and structural conservation from fungi to invertebrates and vertebrates, including mammals. Their biological roles, initially understood as limited to recognition of endogenous ("self") carbohydrate ligands in embryogenesis and early development, dramatically expanded in later years by the discovery of their roles in tissue repair, cancer, adipogenesis, and regulation of immune homeostasis. In recent years, however, evidence has also accumulated to support the notion that galectins can bind ("non-self") glycans on the surface of potentially pathogenic microbes, and function as recognition and effector factors in innate immunity. Thus, this evidence has established a new paradigm by which galectins can function not only as pattern recognition receptors but also as effector factors, by binding to the microbial surface and inhibiting adhesion and/or entry into the host cell, directly killing the potential pathogen by disrupting its surface structures, or by promoting phagocytosis, encapsulation, autophagy, and pathogen clearance from circulation. Strikingly, some viruses, bacteria, and protistan parasites take advantage of the aforementioned recognition roles of the vector/host galectins, for successful attachment and invasion. These recent findings suggest that galectin-mediated innate immune recognition and effector mechanisms, which throughout evolution have remained effective for preventing or fighting viral, bacterial, and parasitic infection, have been "subverted" by certain pathogens by unique evolutionary adaptations of their surface glycome to gain host entry, and the acquisition of effective mechanisms to evade the host's immune responses.

Interaction of Pregnancy-Specific Glycoprotein 1 With Integrin Α5β1 Is a Modulator of Extravillous Trophoblast Functions

Human pregnancy-specific glycoproteins (PSGs) serve immunomodulatory and pro-angiogenic functions during pregnancy and are mainly expressed by syncytiotrophoblast cells. While PSG mRNA expression in extravillous trophoblasts (EVTs) was reported, the proteins were not previously detected. By immunohistochemistry and immunoblotting, we show that PSGs are expressed by invasive EVTs and co-localize with integrin 5. In addition, we determined that native and recombinant PSG1, the most highly expressed member of the family, binds to 51 and induces the formation of focal adhesion structures resulting in adhesion of primary EVTs and EVT-like cell lines under 21% oxygen and 1% oxygen conditions. Furthermore, we found that PSG1 can simultaneously bind to heparan sulfate in the extracellular matrix and to 51 on the cell membrane. Wound healing assays and single-cell movement tracking showed that immobilized PSG1 enhances EVT migration. Although PSG1 did not affect EVT invasion in the in vitro assays employed, we found that the serum PSG1 concentration is lower in African-American women diagnosed with early-onset and late-onset preeclampsia, a pregnancy pathology characterized by shallow trophoblast invasion, than in their respective healthy controls only when the fetus was a male; therefore, the reduced expression of this molecule should be considered in the context of preeclampsia as a potential therapy.