Expression of fucosylated glycans in endothelial glycocalyces of placental villi at early and late fetal growth restriction

Features and Comparative Characteristics of Fucosylated Glycans Expression in Endothelial Glycocalyx of Placental Terminal Villi in Patients with Preeclampsia Treated with Different Antihypertensive Regimens

Antihypertensive therapy is an essential part of management of patients with preeclampsia (PE). Methyldopa (Dopegyt®) and nifedipine (Cordaflex®) are basic medications of therapy since they stabilize blood pressure without affecting the fetus. Their effect on the endothelium of placental vessels has not yet been studied. In this study, we analyzed the effect of antihypertensive therapy on the expression of fucosylated glycans in fetal capillaries of placental terminal villi in patients with early-onset PE (EOPE) and late-onset PE (LOPE), and determined correlation between their expression and mother's hemodynamic parameters, fetoplacental system, factors reflecting inflammatory response, and destructive processes in the endothelial glycocalyx (eGC). A total of 76 women were enrolled in the study: the comparison group consisted of 15 women with healthy pregnancy, and the main group comprised 61 women with early-onset and late-onset PE, who received one-component or two-component antihypertensive therapy. Hemodynamic status was assessed by daily blood pressure monitoring, dopplerometry of maternal placental and fetoplacental blood flows, and the levels of IL-18, IL-6, TNFα, galectin-3, endocan-1, syndecan-1, and hyaluronan in the blood of the mother. Expression of fucosylated glycans was assessed by staining placental sections with AAL, UEA-I, LTL lectins, and anti-LeY MAbs. It was found that (i) expression patterns of fucosylated glycans in eGC capillaries of placental terminal villi in EOPE and LOPE are characterized by predominant expression of structures with a type 2 core and have a similar pattern of quantitative changes, which seems to be due to the impact of one-component and two-component antihypertensive therapy on their expression; (ii) correlation patterns indicate interrelated changes in the molecular composition of eGC fucoglycans and indicators reflecting changes in maternal hemodynamics, fetoplacental hemodynamics, and humoral factors associated with eGC damage. The presented study is the first to demonstrate the features of placental eGC in women with PE treated with antihypertensive therapy. This study also considers placental fucoglycans as a functional part of the eGC, which affects hemodynamics in the mother-placenta-fetus system.

The Endothelial Glycocalyx and Neonatal Sepsis

Sepsis carries a substantial risk of morbidity and mortality in newborns, especially preterm-born neonates. Endothelial glycocalyx (eGC) is a carbohydrate-rich layer lining the vascular endothelium, with important vascular barrier function and cell adhesion properties, serving also as a mechano-sensor for blood flow. eGC shedding is recognized as a fundamental pathophysiological process generating microvascular dysfunction, which in turn contributes to multiple organ failure and death in sepsis. Although the disruption of eGC and its consequences have been investigated intensively in the adult population, its composition, development, and potential mechanisms of action are still poorly studied during the neonatal period, and more specifically, in neonatal sepsis. Further knowledge on this topic may provide a better understanding of the molecular mechanisms that guide the sepsis pathology during the neonatal period, and would increase the usefulness of endothelial glycocalyx dysfunction as a diagnostic and prognostic biomarker. We reviewed several components of the eGC that help to deeply understand the mechanisms involved in the eGC disruption during the neonatal period. In addition, we evaluated the potential of eGC components as biomarkers and future targets to develop therapeutic strategies for neonatal sepsis.

Antibodies Against Unusual Forms of Sialylated Glycans

Previous studies have shown that in the blood of healthy donors (1) there are no natural antibodies against sialylated glycoproteins, which contain Neu5Acα (N-acetylneuraminic acid) as the most widespread form of human sialic acid, and (2) there is a moderate level of antibodies capable of binding unnatural oligosaccharides, where Neu5Ac is beta-linked to a typical mammalian glycan core. In the present study, we investigated antibodies against βNeu5Ac in more detail and verified the presence of Kdn (2-keto-3-deoxy- D-glycero-D-galacto-nonulosonic acid) as a possible cause behind their appearance in humans, taking into account the expected cross-reactivity to Kdn glycans, which are found in bacterial glycoconjugates in both the α- and β-forms. We observed the binding of peripheral blood immunoglobulins to sialyllactosamines (where “sialyl” is Kdn or neuraminic acid) in only a very limited number of donors, while the binding to monosaccharide Kdn occurred in all samples, regardless of the configuration of the glycosidic bond of the Kdn moiety. In some individuals, the binding level of some of the immunoglobulins was high. This means that bacterial Kdn glycoconjugates are very unlikely to induce antibodies to βNeu5Ac glycans in humans. To determine the reason for the presence of these antibodies, we focused on noninfectious pathologies, as well as on a normal state in which a significant change in the immune system occurs: namely, pregnancy. As a result, we found that 2/3 of pregnant women have IgM in the blood against Neu5Acβ2-3Galβ1-4GlcNAcβ. Moreover, IgG class antibodies against Neu5Acβ2-3Galβ1-4GlcNAcβ and Neu5Acβ2-6Galβ1-4GlcNAcβ were also detected in eluates from the placenta. Presumably, these antibodies block fetal antigens.

Comparative Characteristics of the Expression of Fucosylated Glycans and Morphometric Parameters of Terminal Placental Villi Depending on the Severity of Preeclampsia

We performed a comparative analysis of the expression of fucosylated glycans and morphometric characteristics of the terminal villi of the placenta, depending on the severity of preeclampsia (PE). Similar patterns of the expression of fucosylated glycans in the syncytiotrophoblast glycocalyx were revealed in the placental tissue of patients with normal pregnancy and with mild and severe PE: predominance of glycans with α1,6-fucose in the core, clustered fucose residues, and LeX glycan over α1,2-fucose-containing glycans. The expression pattern of fucosylated glycans and the composition of the endothelial glycocalyx are normally close to the expression pattern and composition of the syncytiotrophoblast glycocalyx; in case of mild and severe PE, the expression pattern of fucosylated glycans was changed uniformly, and α1,2-fucose-containing glycans significantly prevailed in the endothelial glycocalyx. According to the results of Fisher's LSD test, in patients with severe PE, the total vascular area in the villus prevailed over the indices established during physiological course of pregnancy (p=0.04) and mild PE (p=0.04). Correlation analysis revealed direct and reciprocal relationships between the morphometric characteristics of the terminal villi of the placenta and the expression of fucosylated glycans in the syncytiotrophoblast and endothelium in PE. Our results indicate a changed expression of fucosylated glycans in the glycocalyx of placental barrier structures and the morphometric parameters of villi in PE of different severity, which can affect the function of the placental barrier.

Expression of the Carbohydrate Lewis Antigen, Sialyl Lewis A, Sialyl Lewis X, Lewis X, and Lewis Y in the Placental Villi of Patients With Unexplained Miscarriages

Background

Lewis antigens such as Sialyl Lewis A (sLeA), Sialyl Lewis X (sLeX), Lewis X (LeX), and Lewis Y (LeY) are a class of carbohydrate molecules that are known to mediate adhesion between tumor cells and endothelium by interacting with its selectin ligands. However, their potential role in miscarriage remains enigmatic. This study aims to analyze the expression pattern of sLeA, sLeX, LeX, and LeY in the placental villi tissue of patients with a medical history of unexplained miscarriages.

Methods

Paraffin-embedded slides originating from placental tissue were collected from patients experiencing a miscarriage early in their pregnancy (6–13 weeks). Tissues collected from spontaneous (n = 20) and recurrent (n = 15) miscarriages were analyzed using immunohistochemical and immunofluorescent staining. Specimens obtained from legally terminated normal pregnancies were considered as control group (n = 18). Assessment of villous vessel density was performed in another cohort (n = 10 each group) of gestation ages-paired placenta tissue. Protein expression was evaluated with Immunoreactive Score (IRS). Statistical analysis was performed by using Graphpad Prism 8.

Results

Expression of sLeA, sLeX, LeX, and LeY in the syncytiotrophoblast was significantly upregulated in the control group compared with spontaneous and recurrent miscarriage groups. However, no prominent differences between spontaneous and recurrent miscarriage groups were identified. Potential key modulators ST3GAL6 and NEU1 were found to be significantly downregulated in the recurrent miscarriage group and upregulated in the spontaneous group, respectively. Interestingly, LeX and LeY expression was also detected in the endothelial cells of villous vessels in the control group but no significant expression in miscarriage groups. Furthermore, assessment of villous vessel density using CD31 found significantly diminished vessels in all size groups of villi (small villi <200 µm, P = 0.0371; middle villi between 200 and 400 µm, P = 0.0010 and large villi >400 µm, P = 0.0003). Immunofluorescent double staining also indicated the co-localization of LeX/Y and CD31.

Conclusions

The expression of four mentioned carbohydrate Lewis antigens and their potential modulators, ST3GAL6 and NEU1, in the placenta of patients with miscarriages was significantly different from the normal pregnancy. For the first time, their expression pattern in the placenta was illustrated, which might shed light on a novel understanding of Lewis antigens’ role in the pathogenesis of miscarriages.

Epithelial apical glycosylation changes associated with thin endometrium in women with infertility - a pilot observational study

BACKGROUND

Low endometrial receptivity is one of the major factors affecting successful implantation in assisted reproductive technologies (ART). Infertile patients with thin endometrium have a significantly lower cumulative clinical pregnancy rate than patients with normal endometrium. Molecular pathophysiology of low receptivity of thin endometrium remains understudied. We have investigated composition of glycocalyx of the apical surface of luminal and glandular epithelial cells in thin endometrium of infertile women.

METHODS

Thirty-two patients with tubal-peritoneal infertility undergoing in vitro fertilization (IVF) were included in the study. Endometrial samples were obtained in a natural menstrual cycle. Patients were divided into two groups: patients with normal endometrium (≥8 mm) and with thin endometrium (< 8 mm). Histochemical and immunohistochemical analysis of paraffin-embedded endometrial samples was performed using six biotinylated lectins (UEA-I, MAL-II, SNA, VVL, ECL, Con A) and anti-LeY and MECA-79 monoclonal antibodies (MAbs).

RESULTS

Complex glycans analysis taking into account the adjusted specificity of glycan-binding MAbs revealed 1.3 times less expression of MECA-79 glycans on the apical surface of the luminal epithelial cells of thin endometrium compared to normal endometrium; this deficiency may adversely affect implantation, since MECA-79 glycans are a ligand of L-selectin and mediate intercellular interactions. The glycans containing a type-2 unit Galβ1-4GlcNAcβ (LacNAc) but lacking sulfo-residues at 6-OH of GlcNAcβ, and binding to MECA-79 MAbs were found; they can be considered as potential markers of endometrium receptivity. Expression of the lectins-stained glycans on the apical surfaces of the luminal and glandular epithelial cells did not differ significantly. Correlation between the expression of difucosylated oligosaccharide LeY on the apical surfaces of the luminal and glandular epithelial cells was found in patients with thin endometrium and recurrent implantation failure. A similar relationship was shown for mannose-rich glycans.

CONCLUSIONS

Specific features of key glycans expression in epithelial compartments of thin endometrium may be essential for morphogenesis of the endometrial functional layer and explain its low receptivity.