Glycosylation at the fetomaternal interface in hemomonochorial placentae from five widely separated species of mammal: is there evidence for convergent evolution?

Term alpaca placenta glycosylation profile and its correlation with pregnancy maintenance and fetal survival

Alpaca is a South American camelid, particularly present in Peruvian highlands, where oxygen concentration and atmospheric pressure are very low. Due to this fact, gestational physiology has adapted to preserve the conceptus' and mother's health. In this context, several cellular and molecular features play an essential role during and at the end of gestation. Structural carbohydrates act on maternal-fetal communication, recognize exogenous molecules, and contribute to placental barrier selectivity. Therefore, this study aimed to characterize the structural carbohydrate profiles that are present in the term alpaca placenta, kept in their natural habitat of around 4,000 m height. For this propose, 12 term alpaca placentas were collected, and the material was obtained at the time of birth from camelids raised naturally in the Peruvian highlands, in the Cusco region. All placenta samples were processed for histological analysis. A lectin histochemical investigation was performed using 13 biotinylated lectins, allowing us to determine the location of carbohydrates and their intensity on a semi-quantitative scale. Our results demonstrated that during term gestation, the epitheliochorial alpaca placenta shows a high presence of carbohydrates, particularly glucose, α-linked mannose, N-acetylglucosamine β (GlcNAc), galactose (αGal), and N-acetylgalactosamine α (GalNAc), present in the trophoblast, amnion epithelium, and mesenchyme, as well as the presence of sialic acid residues and low affinity for fucose. In fetal blood capillaries, the presence of bi- and tri-antennary complex structures and α-linked mannose was predominated. In conclusion, we characterized the glycosylation profile in the term alpaca placenta. Based on our data, compared to those reported in the bibliography, we suggest that these carbohydrates could participate in the labor of these animals that survive in Peruvian extreme environments.

Placental glycotype of the caviomorph rodent Lagostomus maximus and its evolution within Eutheria

The main evolutionary milestone in the oviparity-viviparity transition is placentation. The placenta is an organ with great morphological diversity among eutherians. The expression of different glycosidic residues (Gr) in the near-term placenta constitutes its glycotype. In this study, the expression of different Gr was determined by lectin histochemistry in early, midterm, and near-term placentas of the plains viscacha (Lagostomus maximus), a caviomorph rodent with the highest poliovulatory rate and embryonic resorption rate among eutherians. Besides, a matrix with the expression of each Gr in the exchange trophoblast of viscacha and other eutherians was constructed to map and infer phylogenetic and evolutionary relationships. Between early, midterm, and near-term placentas, variations in the pattern expression of Gr were observed. The glycotype of the near-term placenta is composed of a high diversity of Gr. Reconstruction of the ancestral state for each Gr present in the near-term placenta showed a diverse scenario: some sugars were common to the species of Placentalia included in this study. In the analyzed species with synepitheliochorial and epitheliochorial placentas, no differential glycosylation patterns between them were observed. In species with invasive placentas, such as the endotheliochorial placentas of Carnivora, some common Gr were detected among them, while others were species-specific. In species with hemochorial placenta, the same Gr are shared. Particularly, in the viscacha greater differences with species of the Hominidae and even Muridae families were observed. Nevertheless, greater similarities with other caviomorph rodents were detected. Placental glycotype of each species constitutes an excellent tool to achieve phylogenetic and evolutionary inferences among eutherians.

Placental colonization by Fusobacterium nucleatum is mediated by binding of the Fap2 lectin to placentally displayed Gal-GalNAc

While the existence of an indigenous placental microbiota remains controversial, several pathogens are known to be involved in adverse pregnancy outcomes. Fusobacterium nucleatum is an oral bacterium that is one of several bacteria associated with preterm birth. Oral fusobacteria translocate to the placenta hematogenously; however, the mechanisms localizing them to the placenta remain unclear. Here, using peanut agglutinin, we demonstrate that the level of Gal-GalNAc (Galβ1-3GalNAc; Thomsen Friedenreich antigen) found on trophoblasts facing entering maternal blood rises during gestation and is recognized by the fusobacterial Fap2 Gal-GalNAc lectin. F. nucleatum binding to human and mouse placenta correlates with Gal-GalNAc levels and is reduced upon O-glycanase treatment or with soluble Gal-GalNAc. Fap2-inactivated F. nucleatum shows reduced binding to Gal-GalNAc-displaying placental sections. In a mouse model, intravenously injected Fap2-expressing F. nucleatum, but not a Fap2 mutant, reduces mouse fetal survival by 70%.

Medawar and the immunological paradox of pregnancy: in context

In 1953, Peter Medawar defined 'the immunological paradox of pregnancy', whereby the semi-allogeneic foetus can survive for 9 months in its mother, while a semi-allogeneic graft would be rejected. Here, I revisit the immunological paradox of pregnancy, setting it in the context of the time in which it was proposed. I go on to examine the extent to which Medawar's ideas on the subject have stood the test of time and how they have shaped reproductive immunology.

A preliminary study on the glycosylation of the reproductive tract in the Ostrich (Struthio camelus camelus)

Glycosylation of the reproductive tract of an adult female red-necked ostrich (Struthio camelus camelus) carrying a fully formed calcified egg in her uterus when accidently killed by a blow to the head was examined using lectin histochemistry on samples from the infundibulum, magnum, uterus and vagina. Glycans in the luminal epithelium and underlying glands were described after staining with 23 lectins after neuraminidase pre-treatment in some cases. Ciliated and non-ciliated cells were evident at all levels in the luminal epithelium, the latter full of richly glycosylated secretory granules. The ciliated cells also showed glycosylation and, in the magnum, these cells often stained more intensely than the non-ciliated cells. High mannose and complex N-glycans, α1,6-linked fucosyl and sialic acid residues were present throughout the tract and there was a complete absence of GalNAcα1,3(LFucα1,2)Galß1,3/4GlcNAcß1- and rare terminal GalNAcα1- residues. Fucose in α1,2-linkage as H2 antigen and Le^y was also rare in the luminal epithelium and completely absent in glands. Terminal galactose was present in the luminal epithelium apart from in the infundibulum. Gland epithelium showed similar glycosylation to the luminal epithelium except in the magnum where there were significant differences and here the glands were packed full of large secretory granules, unlike the glands in the rest of the tract. Each section of the tract had its own specific pattern of glycosylation which could be related to the stage of egg formation.

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.

The influences of cycle stage and pregnancy upon cell glycosylation in the endometrium of the mare

From Day 6.5-7 post-conception until its loss around Day 22, the equine embryo is enclosed in a mucinous capsule that prevents direct intercellular interaction between the trophectoderm and uterine epithelium. The embryo is, however, bathed in glycoprotein-rich secretions. In this study, lectin histochemistry was used to characterise the distribution and glycan composition of uterine glycoproteins destined for secretion, and to ascertain the local effect of an embryo on glycosylation in the endometrium. Endometrial biopsies were taken from mares in estrus, on Days 5, 8, 12 and 15 of diestrus, and on Days 12 and 15 of pregnancy and processed for lectin histochemistry. During estrus, lumenal epithelial cells were as truncated pyramids and mainly non-ciliated with glycosylated granules in the cytoplasm. Occasional ciliated cells contained few granules. Five days post-ovulation, non-ciliated cells of the lumenal epithelium were taller, and had accumulated many highly glycosylated apical granules. By Days 12 and 15 post-ovulation these cells were more cuboidal and some showed fewer secretory granules. In marked contrast, by Days 12 and 15 of pregnancy, the ciliated cells were distended, with numerous granules but non-ciliated cells had only a few in the apical cytoplasm. Glycosylation changed dramatically in pregnancy in the luminal and superficial gland epithelium, with fewer fucosylated termini, more N-acetyl galactosamine residues, together with an overall reduction in sialic acid and several other sugar structures. Glycosylation in ciliated cells on Days 12 and 15 of pregnancy showed a striking similarity to that of the blastocyst capsule. The data strongly suggests that glycoprotein production by luminal epithelial cells is influenced by the presence of a conceptus. We speculate that, as well as providing nourishment for the developing embryo, epithelial secretory glycoproteins may contribute components to the capsule, which develops only partially in embryos cultured in vitro.

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.

Immune responses in the human female reproductive tract

Mucosal surfaces are key interfaces between the host and its environment, but also constitute ports of entry for numerous pathogens. The gut and lung mucosae act as points of nutrient and gas exchange, respectively, but the physiological purpose of the female reproductive tract (FRT) is to allow implantation and development of the fetus. Our understanding of immune responses in the FRT has traditionally lagged behind our grasp of the situation at other mucosal sites, but recently reproductive immunologists have begun to make rapid progress in this challenging area. Here, we review current knowledge of immune responses in the human FRT and their heterogeneity within and between compartments. In the commensal-rich vagina, the immune system must allow the growth of beneficial microbes, whereas the key challenge in the uterus is allowing the growth of the semi-allogeneic fetus. In both compartments, these objectives must be balanced with the need to eliminate pathogens. Our developing understanding of immune responses in the FRT will help us develop interventions to prevent the spread of sexually transmitted diseases and to improve outcomes of pregnancy for mothers and babies.

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

Galectins are a phylogenetically conserved family of soluble β-galactoside binding proteins, consisting of 15 different types, each with a specific function. Galectins contribute to placentation by regulating trophoblast development, migration, and invasion during early pregnancy. In addition, galectins are critical players regulating maternal immune tolerance to the embedded embryo. Recently, the role of galectins in angiogenesis during decidualization and in placenta formation has gained attention. Altered expression of galectins is associated with abnormal pregnancies and infertility. This review focuses on the role of galectins in pregnancy-associated processes and discusses the relevance of galectin-glycan interactions as potential therapeutic targets in pregnancy disorders.

A lectin histochemical study to detect variation in glycosylation at the feto-maternal interface in three interbreeding equine species

INTRODUCTION

In this study, we compare glycosylation at the fetomaternal interface in 3 equine species: horse, donkey and zebra, all of which can interbreed to produce hybrids, to assess their glycan similarities and differences.

METHODS

Sections cut from 3 specimens of horse (Equus caballus) placenta (50, 200 and 280 days gestation), one donkey (Equus asinus) placenta (65 cm crown-rump length) and 5 specimens of zebra (Equus quagga) placentae (81-239 days gestation) were stained with a panel of 24 biotinylated lectins using an avidin-peroxidase revealing system.

RESULTS

There were only slight quantitative differences in the lectin histochemistry at the feto-maternal interface between all three specimens; zebra placentae expressed more α2,6-linked sialic acid, with α1,2fucosyl residues at the microvillous interface. However, zebra trophoblast showed histological differences from the other two species, with polarised cells, prominent supranuclear Golgi bodies, and fewer intracellular granules.

DISCUSSION

Our findings appear to confirm the hypothesis that closely related, interbreeding species with epitheliochorial placentae express similar glycans at the feto-maternal interface, thereby supporting the existence of a placental glycocode. We also observed intraspecies evolutionary diversion to be associated with a different histological architecture and the absence of significant intracellular granules.

Glycosylation and immunocytochemistry of binucleate cells in pronghorn (Antilocapra americana, Antilocapridae) show features of both Giraffidae and Bovidae

Although the pronghorn (Antilocapra americana) resembles an antelope, its nearest relatives are the giraffe and okapi. In this study we have examined the placentae of 6 pronghorns using lectin- and immunocytochemistry to identify giraffid and bovid features. Binucleate cells (BNC) of the placenta exhibited features intermediate between those of the giraffe and bovine; Dolichos biflorus agglutinin binding - strong in the bovine BNC and absent in the giraffe - was evident in only a subpopulation of BNC while binding to blood vessels, as in the giraffe. Binding of Phytolacca americana agglutinin resembled that of the giraffe and okapi whereas many other glycans were found in all four clades. PAG antigens were similar to bovine and okapi but not giraffe. In summary, although the pronghorn outwardly resembles an antelope, placental BNC show giraffid features. Although each clade has its own individual characteristics, there are far more similarities than differences between them, emphasizing the common ancestry of all four clades.

Morphology, histochemistry and glycosylation of the placenta and associated tissues in the European hedgehog (Erinaceus europaeus)

INTRODUCTION

There are few descriptions of the placenta and associated tissues of the European hedgehog (Erinaceus europaeus) and here we present findings on a near-term pregnant specimen.

METHODS

Tissues were examined grossly and then formalin fixed and wax-embedded for histology and immunocytochemistry (cytokeratin) and resin embedded for lectin histochemistry.

RESULTS

Each of four well-developed and near term hoglets displayed a discoid, haemochorial placenta with typical labyrinth and spongy zones. In addition there was a paraplacenta incorporating Reichert's membrane and a largely detached yolk sac. The trophoblast of the placenta contained diverse populations of granule which expressed most classes of glycan. Intercellular membranes were also glycosylated and this tended to be heavier in the labyrinth zone. Fetal capillary endothelium had glycosylated apical surfaces expressing sialic acid and various other glycans. Glycogen was present in large cells situated between the spongy zone and the endometrium. Trophoblast cells in the placental disc and under Reichert's membrane, as well as yolk sac endoderm and mesothelium, were cytokeratin positive. Reichert's membrane was heavily glycosylated. Yolk sac inner and outer endoderm expressed similar glycans except for N-acetylgalactosamine residues in endodermal acini.

DISCUSSION

New features of near-term hedgehog placenta and associated tissues are presented, including their glycosylation, and novel yolk sac acinar structures are described. The trophoblast of the placental disc showed significant differences from that underlying Reichert's membrane while the glycan composition of the membrane itself showed some similarity to that of rat thereby implying a degree of biochemical conservation of this structure.

Differences of glycocalyx composition in the structural elements of placenta in preeclampsia

INTRODUCTION

Glycans expressed in the fetal-maternal interface were shown to exert immunomodulating effects and to mediate interactions between the cells. The aim of this study was to investigate alterations in the structure of carbohydrate chains of glycocalyx in placental tissue in pregnancies complicated with preeclampsia (PE).

METHODS

A histochemical analysis of placental tissues was performed with a panel of biotinylated lectins. We analyzed placental tissues in women who had severe or moderate PE and compared them to placentas from women with normal pregnancies.

RESULTS

There was decreased content of terminal residues of α(2,6)-linked sialic acid (as stained by SNA lectin) in the carbohydrate chains of glycocalyx of the endothelium of placental terminal villi in patients with moderate preeclampsia. The composition of the glycocalyx of syncytiotrophoblast in patients of this group did not differ from the control group. Amount of the glycans with terminal β-Gal- (ECL) and α-mannosyl residues (ConA) in the syncytiotrophoblast and capillary endothelium of the placenta was significantly higher in the group with severe PE compared to the control group. The increased content of sialoglycans with α(2,6)-linked sialic acids residues were discovered in the syncytium, and the decreased content of α(2,3)-linked sialic acids residues - in the endothelium of terminal villi in preeclampsia.

DISCUSSION

The most prominent alteration of the glycocalyx composition was found in the placentas of women with severe preeclampsia. It is likely that the modified glycome of syncytiotrophoblast and capillary endothelium may play an important role in pathogenesis of preeclampsia.

A simple histochemical method for the identification of cytotrophoblasts in tissue sections

A simple method for the demonstration of placental cytotrophoblast cells is described, utilising the affinity of the lectin from Bandeiraea simplicifolia-II (BSA-II) for intracellular amylase-sensitive glycogen and a protocol using biotinylated BSA-II followed by an avidin-peroxidase revealing system. In early pregnancy, cytotrophoblast cells in chorionic and anchoring villi are deeply stained and with ongoing differentiation the staining gradually decreases in intensity, suggesting that this lectin can be a useful marker for these cells.

Evidence for Differential Glycosylation of Trophoblast Cell Types

Human placental villi are surfaced by the syncytiotrophoblast (STB), with a layer of cytotrophoblasts (CTB) positioned just beneath the STB. STB in normal term pregnancies is exposed to maternal immune cells in the placental intervillous space. Extravillous cytotrophoblasts (EVT) invade the decidua and spiral arteries, where they act in conjunction with natural killer (NK) cells to convert the spiral arteries into flaccid conduits for maternal blood that support a 3-4 fold increase in the rate of maternal blood flow into the placental intervillous space. The functional roles of these distinct trophoblast subtypes during pregnancy suggested that they could be differentially glycosylated. Glycomic analysis of these trophoblasts has revealed the expression of elevated levels of biantennary N-glycans in STB and CTB, with the majority of them bearing a bisecting GlcNAc. N-glycans terminated with polylactosamine extensions were also detected at low levels. A subset of the N-glycans linked to these trophoblasts were sialylated, primarily with terminal NeuAcα2-3Gal sequences. EVT were decorated with the same N-glycans as STB and CTB, except in different proportions. The level of bisecting type N-glycans was reduced, but the level of N-glycans decorated with polylactosamine sequences were substantially elevated compared with the other types of trophoblasts. The level of triantennary and tetraantennary N-glycans was also elevated in EVT. The sialylated N-glycans derived from EVT were completely susceptible to an α2-3 specific neuraminidase (sialidase S). The possibility exists that the N-glycans associated with these different trophoblast subpopulations could act as functional groups. These potential relationships will be considered.

Functional glycosylation in the human and mammalian uterus

Background

Glycosylation is the most common and structurally diverse of all the post-translational modifications of proteins. Lipids and extracellular matrices are also often glycosylated. The mammalian uterus is highly enriched in glycoconjugates that are associated with the apical surfaces of epithelial cells and the secretions released by both epithelial and stromal cells. These glycoconjugates interact primarily with sperm, the implanting embryo, the fetus, and any pathogen that happens to gain entry into the uterus. Secretions of the endometrial glands increase substantially during the luteal phase of the menstrual cycle. These secretions are highly enriched in glycoproteins and mucins that promote specific uterine functions.

Findings

Lectins and antibodies have been employed in the majority of the studies focused on uterine glycosylation have employed to define the expression of carbohydrate sequences. However, while these studies provide insight about potential glycosylation, precise information about glycan structure is lacking. Direct sequencing studies that employ biochemical or mass spectrometric methods are far more definitive, but have rarely been employed with uterine glycoproteins. Both lectin/antibody binding and direct carbohydrate sequencing studies that have been focused on the mammalian uterus are reviewed. The primary functional role of the eutherian uterus is to facilitate fertilization and nurture the developing embryo/fetus. Trophoblasts are the primary cells that mediate the binding of the embryo and placenta to the uterine lining. In mammals that utilize hemochorial placentation, they invade the decidua, the specialized endometrial lining that forms during pregnancy. Trophoblasts have also been analyzed for their lectin/antibody binding as a complement to the analysis of the uterine cells and tissues. They will also be reviewed here.

Conclusions

The functional roles of the glycans linked to uterine and trophoblast glycoconjugates remain enigmatic. Another major question in the human is whether defects in placental or uterine glycosylation play a role in the development the Great Obstetrical Syndromes. More recent findings indicate that changes in glycosylation occur in trophoblasts obtained from patients that develop preeclampsia and preterm birth. The functional significance of these changes remain to be defined. Whether such shifts happen during the development of other types of obstetrical syndromes remains to be determined.

Hemangioblastic foci in human first trimester placenta: Distribution and gestational profile

INTRODUCTION

The human placenta is a site of both hematopoiesis and vasculogenesis. There are reports of hemangioblastic foci (HAF) in the first trimester placenta, but little published information about their spatiotemporal incidence.

METHODS

We have used semi-thin sections and whole mount staining techniques on archival early pregnancy hysterectomy material as well as freshly-collected termination tissue.

RESULTS

We report a description of the distribution of HAF, their gestational profile, and some characteristics of the constituent cells. We show crypt-shaped HAF are present in villi at different levels from 4 to 11 weeks and in the chorionic plate from 4 to 9 weeks. In the villous placenta, the foci often approach closely at one end to the trophoblast basement membrane. Morphologically they show remarkable similarity to those found in the yolk sac at similar stages. In some crypts, all cells are CD34+, but CD34 and nestin progressively segregate into the endothelial lineage. Brachyury is present in less differentiated cells. The erythroid lineage is dominant, as shown by the widespread expression of CD235a/glycophorin and characteristic erythroid morphologies, indicating various degrees of differentiation. However, CD41 is also present in non-endothelial cells. Initially a discontinuous UEA-1/CD31-positive endothelium forms at the periphery of the foci. These cells appear to become integrated into the developing vasculogenic/angiogenic vessel network. We also demonstrate that, independent of HAF, vasculogenesis occurs near the tips of growing villi during the first trimester.

DISCUSSION

We suggest HAF interface with the developing vascular network, producing communication channels that allow erythrocytes to enter the placental-embryonic circulation. We speculate that the erythroid cells act as oxygen reservoirs during the period before flow of maternal blood through the intervillous space of the placenta, allowing a slow feed of oxygen-rich cells to the developing embryo.

The binucleate cell of okapi and giraffe placenta shows distinctive glycosylation compared with other ruminants: a lectin histochemical study

The placenta of ruminants contains characteristic binucleate cells (BNC) with a highly conserved glycan structure which evolved early in Ruminant phylogenesis. Giraffe and Okapi placentae also contain these cells and it is not known whether they have a similar glycan array. We have used lectin histochemistry to examine the glycosylation of these cells in these species and compare them with bovine BNC which have a typical ruminant glycan composition. Two placentae, mid and near term, from Giraffe (Giraffa camelopardalis) and two term placenta of Okapi (Okapia johnstoni) were embedded in resin and stained with a panel of 23 lectins and compared with near-term bovine (Bos taurus) placenta. Significant differences were found in the glycans of Giraffe and Okapi BNC compared with those from the bovine, with little or no expression of terminal αN-acetylgalactosamine bound by Dolichos biflorus and Vicia villosa agglutinins which instead bound to placental blood vessels. Higher levels of N-acetylglucosamine bound by Lycopersicon esculentum and Phytolacca americana agglutinins were also apparent. Some differences between Okapi and Giraffe were evident. Most N-linked glycans were similarly expressed in all three species as were fucosyl residues. Interplacentomal areas in Giraffe and Bovine showed differences from the placentomal cells though no intercotyledonary BNC were apparent in Okapi. In conclusion, Giraffidae BNC developed different glycan biosynthetic pathways following their split from the Bovidae with further differences evolving as Okapi and Giraffe diverged from each other, affecting both inter and placentomal BNC which may have different functions during development.

Statins inhibit insulin-like growth factor action in first trimester placenta by altering insulin-like growth factor 1 receptor glycosylation

The rapid rise in obesity, metabolic syndrome and type 2 diabetes is one of the major healthcare problems of the Western world. Affected individuals are often treated with statins (3-hydroxy-3-methylglutaryl co-enzyme A [HMG CoA] reductase inhibitors) to reduce circulating cholesterol levels and the risk of developing cardiovascular disease; given the evolving demographic profile of these conditions, such drugs are increasingly prescribed to women of reproductive age. We have previously shown that exposure of placental tissue to statins inhibits the action of insulin-like growth factors (IGF)-I and -II which are key regulators of trophoblast proliferation and placental development. N-linked glycans in the IGF receptor, IGF1R, influence its presentation at the cell surface. This study aimed to determine whether statins, which are known to affect N-glycosylation, modulate IGF1R function in placenta. Treatment of first trimester villous tissue explants with statins (pravastatin or cerivastatin) or inhibitors of N-glycosylation (tunicamycin, deoxymannojirimycin or castanospermine) altered receptor distribution in trophoblast and attenuated proliferation induced by IGF-I or IGF-II (Ki67; P < 0.05, n = 5). Decreased binding of Phaseolus vulgaris lectin and phytohaemagglutinin to IGF1R immunoprecipitated from treated explants demonstrated reduced levels of complex N-linked glycans. Co-incubation of tissue explants with statins and farnesyl pyrophosphate (which increases the supply of dolichol intermediates), prevented statin-mediated disruption of IGF1R localization and reversed the negative effect on IGF-mediated trophoblast proliferation. These data suggest that statins attenuate IGF actions in the placenta by inhibiting N-linked glycosylation and subsequent expression of mature IGF1R at the placental cell surface.

Intermediate filament proteins expression and carbohydrate moieties in trophoblast and decidual cells of mature cat placenta

The aim of this study was to characterize cytoskeletal intermediate filament proteins and glycoconjugates of syncytiotrophoblast, cytotrophoblast and decidual cells of feline endotheliochorial placenta. Samples from 12 normal pregnant female cats, after 45 ± 5 days of gestation, were obtained removing the uterine horns by hysterectomy. Sections were processed for routine observation and for immunohistochemistry using anticytokeratin, antivimentin and antidesmin antibodies. In addition, lectin histochemistry was performed using a panel of several biotinylated lectins to characterize glycosides expression profile. Cytotrophoblast and syncytiotrophoblast showed immunoreactivity only with acidic and basic cytokeratins. Decidual cells were only positive to vimentin, consistent with their origin from endometrial fibroblasts. Trophoblast expressed a broad population of glycans, highly exposing terminal N-acetyl glucosamine residues and non-sialylated galactose and N-acetyl galactosamine oligomers. Oligosaccharides bound by Phaseolus vulgaris erythroagglutinin were the only highly branched N-linked residues evidenced in cats, and they were restricted to the syncytium. Unlike results reported on humans, mice and rats on lectin affinity of decidual cells, sialid acids and complex N-linked oligosaccharides were not demonstrated in cats. Glycosylation of proteins determines many of their final properties, thus becoming essential for the embryo-maternal dialogue during implantation and placentation. Changes in glycosylation pattern have been related to pathological pregnancies in other species. Hence, the knowledge about glycosylation profile of the normal cat placenta may lead to a better understanding of both normal and pathological reproductive events.

A new form of rodent placentation in the relict species, Laonastes aenigmamus (Rodentia: Diatomyidae)

INTRODUCTION

The Laotian rock rat is a relict species in a sister group relationship to hystricognath rodents (Hystricognathi). We asked whether there were similarities in placentation that might reflect this relationship or differences that might cast light on the evolution of Hystricognathi.

METHODS

We examined the reproductive tract of nonpregnant (n = 5), early (n = 3) and mid to late gestation (n = 2) females. Selected characters were mapped to a phylogenetic tree to examine their evolution in rodents.

RESULTS

The chorionic placenta was discoid and labyrinthine with a spongy zone but without internal lobes. The interhemal region was hemodichorial with syncytiotrophoblast lining maternal blood spaces and an inner layer of vacuolated cytotrophoblast. There was no subplacenta. The yolk sac was well developed with a villous portion that faced the placental disk but no fibrovascular ring. There was a single fetus that very likely would be precocial at birth.

DISCUSSION

A lobulated labyrinth and the presence of a subplacenta and a fibrovascular ring emerged as synapomorphies for Hystricognathi. Laonastes, Ctenodactylus and stem Hystricognathi all had precocial young, whereas altriciality was the plesiomorphic condition for rodents. A hemomonochorial interhemal region was plesiomorphic for rodents and Hystricognathi, and the hemodichorial condition found in Laonastes, and possibly in Ctenodactylus, was unlike that of any rodent studied to date.

CONCLUSION

Similar to Hystricognathi, Laonastes bears precocial young, but this species lacks placental adaptations such as the subplacenta, suggesting they were evolved subsequent to a change in reproductive strategy in the common ancestor of Laonastes and Hystricognathi.

Distribution of sugar residues in human placentas from pregnancies complicated by hypertensive disorders

The aim of the study was to investigate the content and distribution of sugar residues in placentas from pregnancies complicated by hypertensive disorders. Placentas from women with uncomplicated pregnancies (group 1), pregnancies complicated by gestational hypertension (group 2), pregnancies complicated by pre-eclampsia (group 3), pregnancies complicated by pre-eclampsia with HELLP syndrome (hemolysis, elevated liver enzymes and low platelets) (group 4) were collected. Lectins: ConA, WGA, PNA, SBA, DBA, UEA I, GNA, DSA, MAA, SNA, in combination with chemical and enzymatic treatments, were used. Data showed a decrease and/or lack of α-d-mannose, α-d-glucose and d-galactose-(β1-4)-N-acetyl-d-glucosamine in placentas from pre-eclampsia and pre-eclampsia with HELLP syndrome compared with control and hypertension cases. N-acetyl-d-galactosamine appeared and/or increased in placentas from hypertensive disorders. A different distribution of various types of sialic acid was observed in placentas from hypertensive disorders compared with the controls. In particular, placentas from pre-eclampsia, with and without HELLP syndrome, lacked the acetylated sialic acid side-chain. These findings demonstrate various alterations of the carbohydrate metabolism in the placentas from pregnancies complicated by different types of hypertensive disorders. This indicates correlation with the placental morpho-functional changes characteristic of these complications and with the degree of clinical severity.

Characterisation of Hofbauer cells in first and second trimester placenta: incidence, phenotype, survival in vitro and motility

Macrophages, known as Hofbauer cells, are most abundant in placental villous stroma in the first and second trimesters. Their functions are not well defined. We have used a combination of in situ and in vitro methods to characterise these cells. Lectin histochemistry and immunohistochemistry were used to identify macrophages in situ. The lectin from Maclura pomifera (MPA) was found to mark cells bearing the CD68 antigen with optimal specificity and selectivity. MPA staining was used to show that they increase in number from mid first to mid second trimester, becoming much less abundant at term. The cells are absent from mesenchymal villi, being associated primarily with villous stroma containing the prominent interstitial channels characteristic of immature intermediate villi. A mixed stromal cell isolate was studied in monolayer culture, including the use of time-lapse microscopy. Cells from first or second trimester tissue contained a subpopulation of about 14-17% of cells that exhibited a macrophage-like morphology and expressed CD68 as well as MPA-binding glycans. These cells were short-lived in monoculture, but could persist in vitro in association with a fibroblast layer for several weeks. They could switch rapidly from a macrophage-like to a fibroblastic morphology, were highly motile and associated in clusters that rapidly formed and dissipated over periods of a few hours. These data suggest that Hofbauer cells play a role in the maturation of mesenchymal into immature intermediate-type stroma. They may be important in the excavation of stromal channels. Their prolonged viability in mixed cultures suggests a paracrine relationship with resident fibroblasts. Their location and migratory behaviour predict an ability to move rapidly around the villous stroma, perhaps within the channel system, and to make transient contacts both with other macrophages and stromal cells.

Placentation in the Egyptian slit-faced bat Nycteris thebaica (Chiroptera: Nycteridae)

Bats are a highly successful, widely distributed group, with considerable variation in placental structure. The Egyptian slit-faced bat Nycteris thebaica is a member of one of the few families with previously undescribed placentation. It was found that, although the interhemal type of the Nycteris placenta is endotheliochorial with a single layer of cytotrophoblast, the arborizing pattern of the maternal vessels and especially the extraordinary major placental artery differs from the placenta of the emballonurid bats to which this family is considered to be most closely related. The major placental artery providing maternal blood to the vessels of the placental disk has a highly glycosylated matrix surrounded by two-layered folds of trophoblast, forming an apparently rigid structure of unique morphology. The yolk sac is collapsed, with hypertrophied endodermal and mesothelial cells similar to many other bat species. The paraplacenta is extensive with abundant fetal vessels underlying cytotrophoblast and syncytial trophoblast layers, fronting on an endometrium that largely lacks uterine epithelial cells but has large decidual cells and is poorly vascularized. The placenta of Nycteris lacks a hemophagous region, unlike the emballonurid bats Taphozous and Saccopteryx. Although the latter two species have similar placentas, the placental structure of Nycteris does little to relate it to the other family within the Emballonuroidea. Shared and divergent reproductive characters are discussed in relationship to bat phylogenetic relationships.

Placentation in the Hottentot golden mole, Amblysomus hottentotus (Afrosoricida: Chrysochloridae)

The placentation of the Hottentot golden mole (Amblysomus hottentotus) has been examined using light and electron microscopy and lectin histochemistry of nine specimens at both mid and late gestation. The placentae were lobulated towards the allantoic surface and the lobules contained roughly parallel arrays of labyrinthine structures converging on a central spongy zone. At mid gestation, the arrays were composed of an inner cellular and outer syncytial trophoblast layer, the inner layer enclosing scant connective tissue and fetal capillaries. Maternal blood spaces coursed through the outer trophoblast and were lined by trophoblastic microvilli; the blood spaces were narrow in mid gestation but enlarged near term, while the inner trophoblast layer became thinner and seemed to be syncytial. These features were confirmed by transmission electron microscopy. The microvillous surfaces and dispersed cytoplasmic particles were heavily glycosylated, as shown by lectin histochemistry, and exhibited changes with maturation, particularly a loss in N-acetyl glucosamine oligomers bound by Phytolacca americana lectin on the microvilli lining the maternal blood spaces and outer trophoblast particles. A substantial yolk sac was present both in mid and late gestation stages. It was clearly unattached to the uterus in the later stages. These morphological features are discussed in relation to the phylogenetic position of Amblysomus with respect to other members of Afrosoricida and Afrotheria.

Placental protein 13 (galectin-13) has decreased placental expression but increased shedding and maternal serum concentrations in patients presenting with preterm pre-eclampsia and HELLP syndrome

Placental protein 13 (PP13) is a galectin expressed by the syncytiotrophoblast. Women who subsequently develop preterm pre-eclampsia have low first trimester maternal serum PP13 concentrations. This study revealed that third trimester maternal serum PP13 concentration increased with gestational age in normal pregnancies (p < 0.0001), and it was significantly higher in women presenting with preterm pre-eclampsia (p = 0.02) and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome (p = 0.01) than in preterm controls. Conversely, placental PP13 mRNA (p = 0.03) and protein, as well as cytoplasmic PP13 staining of the syncytiotrophoblast (p < 0.05) was decreased in these pathological pregnancies compared to controls. No differences in placental expression and serum concentrations of PP13 were found at term between patients with pre-eclampsia and control women. In contrast, the immunoreactivity of the syncytiotrophoblast microvillous membrane was stronger in both term and preterm pre-eclampsia and HELLP syndrome than in controls. Moreover, large syncytial cytoplasm protrusions, membrane blebs and shed microparticles strongly stained for PP13 in pre-eclampsia and HELLP syndrome. In conclusion, parallel to its decreased placental expression, an augmented membrane shedding of PP13 contributes to the increased third trimester maternal serum PP13 concentrations in women with preterm pre-eclampsia and HELLP syndrome.

Glycosylation at the fetomaternal interface: does the glycocode play a critical role in implantation?

During pregnancy, the heavily glycosylated surfaces of the implanting blastocyst and maternal uterine epithelium interact in a highly controlled and specific manner. Examination of this interface in species that show interdigitation of embryonic and maternal surfaces (epitheliochorial placentation) shows that each has its own particular pattern of glycosylation or glycotype, and that closely related and/or interbreeding species e.g. horse and donkey or llama and guanaco, have very similar glycotypes. Implantation of interspecies hybrids is facilitated, when the blastocyst has an outer cell layer bearing glycans that are compatible with the maternal host. We refer to this mutual compatibility as a glycocode. The probability that hybrid embryo glycotypes differ from those normally associated with the host species may account for the high pregnancy failure rates seen in interspecies breeding. We suggest the maternal host selects between genotypically distinct embryos, and this selection depends partly on cell surface glycosylation. We infer that the glycocode plays a critical role in implantation, for if the survival of modified genotypes results in fitter offspring with altered placental glycosylation, selection pressure downstream may in turn act to drive adaptations in the maternal surface glycotype to produce a complementary glycocode, thus leading eventually to the creation of new species. We speculate that glycan microheterogeneity plays a specific role in this process.