Epitheliochorial Placenta Research Articles

Evolutionary implications of fetal and maternal microvillous surfaces in epitheliochorial placentae.

According to the "parent-offspring conflict hypothesis" the rapid evolution and diversification of the mammalian placenta is driven by divergent optima of resource allocation between fetus and mother. The fetus has an interest to maximize its resource intake, while the mother has an interest to restrict the transfer of resources, and thus retain resources for subsequent pregnancies. In the epitheliochorial placenta, the contacting fetal and maternal surfaces at the feto-maternal interface are covered with microvilli, which leads to an increase of membrane surfaces available for transport processes. Because membranes are the site of active transport, the conflict hypothesis predicts that the fetal surfaces at the feto-maternal interfaces are larger than the maternal ones. We use transmission electron microscopy and a stereological method to estimate the factors by which the apical fetal and maternal membranes are enlarged by the microvilli. Ten species with an epitheliochorial placenta were studied. Focused ion beam-scanning electron microscopy (FIB-SEM) was used to create three-dimensional models of the interdigitating microvilli of the bovine and porcine placenta. In all species, the fetal surface was larger than the maternal. This was due to a higher number of fetal microvilli and to the presence of membrane folds at the base of the fetal, but not of maternal microvilli. Our results suggest that the ultrastructural morphology of the feto-maternal interface in the epitheliochorial placenta is shaped by conflicting interests between fetus and mother and thus represent a so far neglected arena of the parent-offspring conflict.

IL-1β, IL-2 and IL-4 concentration during porcine gestation

In pigs, given the type of epitheliochorial and non-invasive placenta, the trophoblast is in intimate contact with maternal tissues. The dialogue established between the conceptus and the endometrium involves, among others, the immune system, which minimizes the chances of rejection of the embryo and promotes the establishment of pregnancy. The aim of this work was to determine the concentration of IL-1β, IL-2 and IL-4 in sera and in extracts of maternal and fetal placenta from sows of different gestational periods. Reproductive tracts from 23 crossbreed sows, between 30 and 114 days of gestation (dg), and from 8 non-pregnant sows were used. The concentration of the cytokines was determined by ELISA. IL-1β, IL-2 and IL-4 demonstrated a similar pattern of concentration at the placental interface and serum; they were found elevated in tissues at 30 and 60–70 dg, and significantly decreased at term, period in which the cytokines were significantly increased in serum. These results show that IL-1β, IL-2, and IL-4 are differentially modulated during pregnancy and at term, and suggest an important role of these cytokines in defining the proinflammatory stage of these periods.

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

IntroductionIn 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. MethodsSections 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. ResultsThere 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. DiscussionOur 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.

Pregnancy and spontaneous fetal loss: A pig perspective.

Pigs have a unique, non-invasive epitheliochorial placenta where maternal and fetal layers lay in apposition. Indentation of fetal capillaries into the trophoblasts and maternal capillaries into the uterine epithelium reduce the distance between the fetal and maternal blood, ensuring nutrient transfer for proper conceptus development. Another unique feature of pig pregnancy is conceptus-mediated immune cell enrichment during the early stages of conceptus attachment (around gestation Day 15). This period coincides with the development of vasculature networks at the maternal-fetal interface, which is critical for successful conceptus growth. Specific chemokines, their receptors, and chemokine decoy receptor networks coordinate this immune cell enrichment and the positioning at the maternal-fetal interface. The recruited immune cells, in turn, adopt a specialized phenotype to support key processes of maternal-fetal adaptations, including tolerance to the semi-allogeneic fetus and supporting vascularization. Disturbance in coordinated cross talk between the conceptus and maternal endometrium is an important mechanism associated with spontaneous fetal loss. The exact mechanism of fetal loss is still not yet identified, although research in the last two decades point to various factors including genetics, nutrition, uterine capacity, placental efficiency, and imbalanced immune factors at the maternal-fetal interface. In this review, we summarize some of the recent advances in endometrial immune cell functions and their regulation. We also provide insights into endometrial/placental transcriptome, microRNA biology, and extravesicular transport across the maternal-fetal interface, as well as their potential implications in porcine pregnancy success or failure.

Extracellular matrix proteins in healthy and retained placentas, comparing hemochorial and synepitheliochorial placentas

The placenta expresses structural and biologically active proteins. Their synthesis is mainly regulated by genomic or nongenomic signals and modulated by hormones. These protein profiles are altered during different stages of pregnancy. The biological properties of extracellular matrix (ECM) proteins were defined and described in a number of tissues including placenta. These properties enable them to be the main players in the processes of attachment or invasion into the endometrium during initial placenta formation and its timely separation after delivery and detachment. In this review, we focused on the role of ECM proteins during attachment of the placenta to the uterine wall, its timely separation, and the implications of this process on retained or pathologically attached placenta.Although the amount of published information in this area is relatively scant, some of the key proteins and processes are well defined. We focused on the available data detailing the ECM protein profiles of human (histologically thin; hemochorial) and bovine (histologically thick; epitheliochorial) placentas and compared the shared and unique ECM proteins that are relevant to placental attachment and separation.

High Expression of Endogenous Retroviral Envelope Gene in the Equine Fetal Part of the Placenta.

Endogenous retroviruses (ERVs) are proviral phases of exogenous retroviruses that have co-evolved with vertebrate genomes for millions of years. Previous studies have identified the envelope (env) protein genes of retroviral origin preferentially expressed in the placenta which suggests a role in placentation based on their membrane fusogenic capacity and therefore they have been named syncytins. Until now, all the characterized syncytins have been associated with three invasive placentation types: the endotheliochorial (Carnivora), the synepitheliochorial (Ruminantia), and the hemochorial placentation (human, mouse) where they play a role in the syncytiotrophoblast formation. The purpose of the present study was to evaluate whether EqERV env RNA is expressed in horse tissues as well and investigate if the horse, possessing an epitheliochorial placenta, has “captured” a common retroviral env gene with syncytin-like properties in placental tissues. Interestingly, although in the equine placenta there is no syncytiotrophoblast layer at the maternal-fetal interface, our results showed that EqERV env RNA is highly expressed at that level, as expected for a candidate syncytin-like gene but with reduced abundance in the other somatic tissues (nearly 30-fold lower) thus suggesting a possible role in the placental tissue. Although the horse is one of the few domestic animals with a sequenced genome, few studies have been conducted about the EqERV and their expression in placental tissue has never been investigated.

Equine placenta – A clinician's perspective. Part 1: Normal placenta – Physiology and evaluation

SummaryA complex organ, the equine placenta is responsible for fetal nourishment, protection from external and internal insults, and the production and/or metabolisation of various hormones. The endometrial cups are unique structures of the equine placenta that are responsible for producing an essential hormone for equine pregnancy, equine chorionic gonadotropin. Since mares have epitheliochorial placentae, with 6 layers of tissue separating maternal from fetal circulation, almost the entire surface of the chorioallantois must be attached to the maternal endometrium in order to support a developing fetus adequately. The only avillous areas of the normal chorioallantois are: the cervical star, sites of the endometrial cups, areas facing oviductal papillae, folds overlying major allantoic vessels, and fetal footPADs (placental areas of degeneration). There are characteristic differences between the gravid and the nongravid horn of the chorioallantois. Allantoic vesicles, allantoic pouches, hippomanes, amniotic plaques and yolk sac remnants are normal features of the equine placenta. The clinician should thoroughly examine the entire placenta immediately after its expulsion. The most important aspect of this evaluation is to check for completeness of the chorioallantois, along with identifying any pathological lesions on the fetal membranes or the umbilical cord.

The Expression Pattern of MicroRNAs and the Associated Pathways Involved in the Development of Porcine Placental Folds That Contribute to the Expansion of the Exchange Surface Area.

The development of the microscopically folded structure of the diffuse epitheliochorial placenta in pigs is important because it expands the surface area for maternal-fetal exchange, resulting in an increase in placental efficiency. To better understand the regulatory mechanisms involved in this process, we characterized miRNA expression profiles in porcine placentas during the initiation and establishment of placental fold development. A total of 42 miRNAs were found to be differentially expressed, and their putative target genes were predicted using four target prediction programs. Following a comparative analysis with published gene expression pattern data obtained from porcine placentas in the corresponding stages of placental fold development, only those genes that were negatively correlated with miRNA expression were retained for further function and pathway enrichment analysis. The results showed that the up-regulated miRNAs were associated mainly with extracellular matrix remodeling and tissue morphogenesis, while the down-regulated miRNAs were related to cell proliferation and signal transduction. Furthermore, we provide evidence that miR-130b may facilitate the expression of HPSE, which has been reported to be a regulator of the folding of the pig placenta, by suppressing the expression of PPARG. In addition, we also reveal that the miRNA-target pairs expressed in the pig placenta may trigger the degradation of the stromal matrix and basement membrane (miR-29a-COL1A2, COL3A1, and LAMC1) and regulate trophoblast epithelial cell adherens junctions (the miR-200 family and miR-205-ZEB2-CDH1) and proliferation (miR-17-92 cluster-HBP1 and ULK1). Taken together, these results indicate that miRNAs and related pathways may have potential roles in porcine placental fold development.

Structure and functions of the placenta in common minke (<i>Balaenoptera acutorostrata</i>), Bryde’s (<i>B. brydei</i>) and sei (<i>B. borealis</i>) whales

The structure and functions of placentas were examined in 3 species of rorqual whales, common minke (Balaenoptera acutorostrata), Bryde’s (B. brydei) and sei (B. borealis) whales, with the aim of confirming the structural characteristics of the chorion, including the presence of the areolar part, and clarifying steroidogenic activities and fetomaternal interactions in the placentas of these whales. Placentas were collected from the second phase of the Japanese Whale Research Program under Special Permit in the North Pacific (JARPN II). Histological and ultrastructural examinations revealed that these whale placentas were epitheliochorial placentas with the interdigitation of chorionic villi lined by monolayer uninucleate cells (trophoblast cells) and endometrial crypts as well as folded placentation by fold-like chorionic villi. Moreover, well-developed pouch-like areolae were observed in the placentas, and active absorption was suggested in the chorionic epithelial cells of the areolar part (areolar trophoblast cells). Berlin blue staining showed the presence of ferric ions (Fe3+) in the uterine glandular epithelial cells and within the stroma of chorionic villi in the areolar part. An immunohistochemical examination revealed tartrate-resistant acid phosphatase (TRAP; known as uteroferrin in uteri) in the cytoplasm of glandular cells and areolar trophoblast cells. This result suggested that, in cetaceans, uteroferrin is used to supply iron to the fetus. Furthermore, immunoreactivity for P450scc and P450arom was detected in trophoblast cells, but not in areolar trophoblast cells, suggesting that trophoblast cells synthesize estrogen in whale placentas. Therefore, we herein immunohistochemically revealed the localization of aromatase and uteroferrin in cetacean placentas during pregnancy for the first time.

Osteopontin: a leading candidate adhesion molecule for implantation in pigs and sheep.

Osteopontin (OPN; also known as Secreted Phosphoprotein 1, SPP1) is a secreted extra-cellular matrix (ECM) protein that binds to a variety of cell surface integrins to stimulate cell-cell and cell-ECM adhesion and communication. It is generally accepted that OPN interacts with apically expressed integrin receptors on the uterine luminal epithelium (LE) and conceptus trophectoderm to attach the conceptus to the uterus for implantation. Research conducted with pigs and sheep has significantly advanced understanding of the role(s) of OPN during implantation through exploitation of the prolonged peri-implantation period of pregnancy when elongating conceptuses are free within the uterine lumen requiring extensive paracrine signaling between conceptus and endometrium. This is followed by a protracted and incremental attachment cascade of trophectoderm to uterine LE during implantation, and development of a true epitheliochorial or synepitheliochorial placenta exhibited by pigs and sheep, respectively. In pigs, implanting conceptuses secrete estrogens which induce the synthesis and secretion of OPN in adjacent uterine LE. OPN then binds to αvβ6 integrin receptors on trophectoderm, and the αvβ3 integrin receptors on uterine LE to bridge conceptus attachment to uterine LE for implantation. In sheep, implanting conceptuses secrete interferon tau that prolongs the lifespan of CL. Progesterone released by CL then induces OPN synthesis and secretion from the endometrial GE into the uterine lumen where OPN binds integrins expressed on trophectoderm (αvβ3) and uterine LE (identity of specific integrins unknown) to adhere the conceptus to the uterus for implantation. OPN binding to the αvβ3 integrin receptor on ovine trophectoderm cells induces in vitro focal adhesion assembly, a prerequisite for adhesion and migration of trophectoderm, through activation of: 1) P70S6K via crosstalk between FRAP1/MTOR and MAPK pathways; 2) MTOR, PI3K, MAPK3/MAPK1 (Erk1/2) and MAPK14 (p38) signaling to stimulate trohectoderm cell migration; and 3) focal adhesion assembly and myosin II motor activity to induce migration of trophectoderm cells. Further large in vivo focal adhesions assemble at the uterine-placental interface of both pigs and sheep and identify the involvement of sizable mechanical forces at this interface during discrete periods of trophoblast migration, attachment and placentation in both species.Electronic supplementary materialThe online version of this article (doi:10.1186/2049-1891-5-56) contains supplementary material, which is available to authorized users.

The phenotype and activation status of T and NK cells in porcine colostrum suggest these are central/effector memory cells

In pigs, the epitheliochorial placenta does not allow transfer of maternally derived antibodies or immune cells to the fetus. Thus, piglets are dependent on intake of colostrum for acquisition of passive immunity during the neonatal period. As well as immunoglobulin G (IgG), cellular components of colostrum, mainly lymphocytes, can enter the systemic circulation and secondary lymphoid organs of the neonate. In order to understand the function and immunological role of these cells, a flow cytometric study was undertaken to characterise the cellular profile and phenotype of T cells and NK cells present in porcine colostrum.The results indicated that the greatest numbers of lymphocytes were found on the first day of lactation. The predominant cell types in colostrum were CD8+ single positive T cells (53.6%), followed by CD4+CD8+ double positive T cells (21.1%), CD2+CD8+ γδ T cells (15.0%) and NK cells (13.5%). CD4+ single positive T cells (4.4%) and other γδ T cell subpopulations (1.8% CD2−CD8− and 0.4% CD2+CD8−) were present in colostrum at low levels. Although the profile of the T cell subpopulations during the first 3 days of lactation remained constant, the absolute numbers of T and NK cells decreased significantly in the first few hours of lactation. Expression of CCR7, CD11b, CD25, CD45RA and MHC class II was used to assess the activation status of T and NK cells in colostrum. T cell subpopulations expressed markers consistent with an effector memory phenotype, indicating that these were antigen-experienced cells. The phenotype of colostral T and NK cells suggests a role in mucosal immunity and potentially in transfer of passive immunity from sow to piglet.

VEGF system expression by immunohistochemistry and real-time RT-PCR study on collared peccary placenta

Vascular endothelial growth factor (VEGF) is known to induce endothelial cell proliferation, to promote cell migration, and to inhibit apoptosis, thus playing a central role in angiogenesis and in the regulation of vasculogenesis. The expression of the VEGF–ligand receptor system was studied in the placenta and uterus of the collared peccary in nonpregnant females in the luteal phase and throughout pregnancy (>35, 75, 115, and 135 days). The material was examined by immunohistochemistry and by real-time reverse transcription polymerase chain reaction. Intense positive immunolabeling was observed for VEGF and its receptors in the uterine epithelium, uterine glands, and trophoblast. The endothelial cells and smooth muscle cells in the maternal and fetal vessels, as well as the connective tissue and mesenchyme, had weak immunoreactivity during all periods of pregnancy. The regression analysis of the real-time polymerase chain reaction results demonstrated cubic behavior, showing a specific time-dependent profile during pregnancy, which increased over the last gestational period to VEGF and VEGFR-1. The relative expression of VEGFR-2 decreased in the middle-third of the pregnancy and increased in late pregnancy. In the collared peccary, the expression of the VEGF–ligand receptor system was similar to that in porcine and ruminant placentas, suggesting that an epitheliochorial placenta has the same physiological and interhemal barrier during vascular gestational development. The expression of VEGF among cells not related to the vascular system, such as those of the uterine epithelium, trophoblast, and uterine glands, suggests a distinct regulatory role for these cells in vasculogenesis and also a different role of VEGF pathway.

Colostrogenesis during an induced lactation in dairy cattle.

Colostrum immunoglobulin G (IgG) is of major importance for the newborn calf because epitheliochorial placentae do not provide transport in utero. The formation of colostrum occurs in the later stages of pregnancy. Our objectives were to induce lactation in non-pregnant dairy cows and (i) to determine the changes of IgG in serum and mammary secretions during the induction process and (ii) to establish α-lactalbumin (αLA) and prolactin (Prl) alterations to monitor the changing mammary epithelial tight junction status and development pattern. Estradiol-17β (E2) and progesterone (P4) injections in a 1-7days series were combined with a 3-day injection series (day 21-23) of dexamethasone (DEX). Blood and both front quarter secretion samples were collected daily. Milking started 24days after the start of the experiment. Results show that the mammary secretory IgG1 was increased at >7days after the start of steroid injections and depicted a bimodal pattern reaching a high of 16mg/ml at 21day compared with 3.2mg/ml in the serum. There was a small increase in secretory IgG2 that did not correlate with tight junction status, but never reached the serum concentration. The injections of DEX resulted in constriction of tight junctions. Secretory αLA was immediately increased with steroid injections, dropped precipitously after 7days and then began a steady increase until the start of milking. Changes in serum αLA are related to mammary tight junctions while serum Prl gradually increased from 30 to >60ng/ml after the steroid injections stopped. These results provide insights into the mechanisms and timing of colostrogenesis during an induced lactation protocol.

Expression of Heparanase Is Associated with Breed-Specific Morphological Characters of Placental Folded Bilayer Between Yorkshire and Meishan Pigs1

The pig has a noninvasive epitheliochorial placenta, and trophoblast-endometrial epithelial bilayer development could impact on placental function. This work compared the morphological structures, the cell proliferation status as assessed by Ki67 staining, as well as the location and gene and protein expression of heparanase (HPSE) at the maternal-fetal interface between Yorkshire and Meishan pigs on Days 26, 50, and 95 of gestation. Histomorphometry showed that the widths of placental folds, endometrial stroma, and placental stroma in Meishan pigs were smaller than those in Yorkshire pigs during late gestation, while the complexity and the cell proliferation ability of the folded bilayer were greater in Meishan pigs in this period. The location and expression levels of HPSE mRNA and protein at the maternal-fetal interface were similar between the two breeds during early and midgestation. However, during late gestation, the mRNA and protein levels were higher in Meishan placentae. In addition, the HPSE mRNA was expressed by all the trophoblast cells, and the protein was located both at trophoblast and luminal epithelium cells in Meishan pigs during late gestation, while in Yorkshire pigs, the HPSE mRNA and protein were only identified in trophoblast cells located at the bottom and side of folds. The findings suggest that Meishan pigs may rely more upon the increase in the complexity of the folded bilayer within a reduced placenta to expand the exchange surface area and the HPSE may contribute to the development of the folded bilayer in pigs.

Y.W. Loke, Life's Vital Link: The Astonishing Role of the Placenta

Y.W. Loke, Life's Vital Link: The Astonishing Role of the Placenta

Immunoglobulin Transport during Gestation in Domestic Animals and Humans—A Review

Maternal immunity is the main early defense against infectious agents in newborns. Immunoglobulin G (IgG) is indispensable for immune defense against infectious agents. IgG is transported through either the colostrum or the placenta. Immunoglobulins are antibodies, and the five different classes of these antibodies are IgG, IgA, IgM, IgD and IgE. Through their biological function of binding antigens, antibodies facilitate the removal of antigens from the body. The placenta is a temporary maternal-fetal organ, whose principal function is to allow the controlled exchange of metabolites between mother and embryo/fetus during gestation. The placenta types in different species are classified by the number of membranes separating the maternal and fetal blood circulation. Humans, lagomorphs and rodents have hemochorial placentas, which require a receptor for IgG transfer. In other animals, such as horse and pig (epitheliochorial placenta), ruminants (synepitheliochorial placenta) and carnivores (endotheliochorial placenta), antibodies are transferred via the colostrum and absorbed by passive diffusion. This review covers immunoglobulin transport in several types of placentas.

Pig blastocyst–uterine interactions

The litter-bearing pig is an invaluable model for research in reproductive biology. Spherical pig blastocysts on Day 10 of pregnancy undergo rapid morphological changes to tubular and then filamentous forms by Day 12 and a filamentous conceptus of almost 1m in length by Day 16 of pregnancy. Thus, trophectoderm of each conceptus achieves intimate contact with luminal uterine epithelium (LE) for exchange of nutrients, gases, hormones, growth factors and other key molecules for survival and development. Estrogens secreted between Days 11 and 13 of pregnancy signals pregnancy recognition to ensure that nutrients and prostaglandin F2-alpha (PGF) are secreted into the uterine lumen (exocrine secretion) rather than into the uterine vein (endocrine secretion) which would lead to regression of the corpora lutea (CL) and failure to maintain pregnancy. Pigs have a true epitheliochorial placenta. The fluid filled amnion bouys the embryo so that it develops symmetrically. The allantois fills with allantoic fluid to expand contact of the chorioallantois with uterine LE, and the allanotois supports the vascular system of the placenta. The chorion/trophectoderm in direct contact with uterine LE exchanges gases and nutrients and forms unique structures call areolae that absorb nutrient-rich secretions from uterine glands and transports them directly into fetal blood. The period from Days 20 to 70 of pregnancy is for placental growth in preparation for rapid fetal growth between Days 70 and 114 (term) of gestation. Maturation of the fetal hypothalamic–pituitary–adrenal axis leads to increases in secretion of cortisol from the fetal adrenal glands. Cortisol sets in motion secretion of estrogens, oxytocin, relaxin and prolactin, as well as increases in their receptors, which are required for delivery of piglets and for initiation of lactation and expression of maternal behavior. This review provides details of gestation in the pig with respect to uterine biology, implantation, placentation, fetal development and parturition.

79 UTERINE AND PLACENTAL INTERACTIONS DURING NECROTIC TIP DEVELOPMENT IN THE PIG FROM DAY 22 TO 42 OF GESTATION

Placental development is important for fetal development and nutrient and waste transport. The pig, a litter bearing animal, has an epitheliochorial placenta that forms a noninvasive attachment with the uterine endometrium. Insufficient placental development is one of the primary causes of fetal death and reduced fetal growth after 35 days of gestation. Necrotic tips develop at the distal ends of each allantochorion between Day 22 and 42 of gestation. During this same period, placenta attaches to the uterine endometrium and establish fetal blood supplies and nutrient exchange. The attached placenta is composed of a central highly vascular placental (HVP) region adjacent to the fetus and less vascular placental (LVP) regions on either side to the fetus, the paraplacenta and necrotic tips, which form after 27 days of gestation. The objective of this study was to comprehensively evaluate uterine–placental interactions and necrotic tip development from 22 to 42 days of gestation in the gilt. Gilts (n = 25) were bred by AI at first detection of oestrus (Day 0) and harvested at 22, 27, 32, 37, or 42 days of gestation. Each conceptus was counted and weighed to identify the large, medium, and small fetus in each litter. From these fetuses, HVP and LVP sections of tissue and necrotic tip (no placental attachment) were collected. Intact attached uterus and placenta were collected for histology and preserved in paraformaldehyde. Placentas were then stripped from the endometrium and individually weighed. Hematoxylin and eosin staining of uterine : placental sections was used to identify uterine fold development in the HVP, LVP, and uterine endometrial morphology in the necrotic tip regions. Three folds were measured for depth, width, and area using BQ Nova Prime software (Bioquant Image Analysis, Nashville, TN, USA). Data were analysed using PROC MIXED in SAS (SAS Institute Inc., Cary, NC, USA). Litter size, 12.1 ± 3.4, was similar (P = 0.86) for all days of gestation. Fetal and placental weight increased (P < 0.05) as day of gestation increased. Average fetal weight was similar (P = 0.30) for Day 27 and 32 with a tendency (P = 0.09) to increase by Day 37 before a significant increase at Day 42 (P = 0.002). The placenta increased (P = 0.02) in weight throughout this period of gestation, with the greatest increase in weight between 37 and 42 days of gestation. The LVP zones had no measureable fold formation until Day 32 from most conceptuses, and all LVP zones displayed microfold formation by Day 37. Necrotic tips became apparent after 27 days of gestation. Necrotic tip areas of the uterus had observable modifications from Day 32 to 42 of gestation, developing folds with dramatic changes in endometrial cell size and morphology. This work demonstrated fundamental time points in placental development that correspond to fetal growth and microfold formation. Gestation Day 27 through 32 show limited changes in either fetal growth or increased placental weight; however, significant morphological changes occur throughout the placenta, and even necrotic tips demonstrating the dynamic architecture of the establishing porcine placenta during early gestation.

The fetomaternal interface shows vascular hypoglycosylation in the tammar wallaby Macropus eugenii: Comparison with a range of non-mammalian and eutherian placentae

IntroductionBlood vessel glycosylation at the fetomaternal interface of four near-term specimens of tammar wallaby, Macropus eugenii, has been examined at days 23–26 of the 26.5 day pregnancy and compared with that of other species. MethodsA panel of 23 lectins was used to compare vasculature in tammar with non-mammalian (shark, skink) and eutherian species at early and late gestation (camel, horse and alpaca), and term/near-term (cat, lion, dog, mink and elephant). ResultsStrikingly low levels of all the glycans tested, apart from sialic acids, were found in capillary endothelium of both the trilaminar omphalopleure and underlying surface endometrium of the tammar, though deeper endometrial vessels showed normally high levels of glycosylation. Only maternal vasculature of the mink placenta showed a comparable lack of expression. DiscussionOne reason for a reduced endothelial glycocalyx may be to facilitate diffusion of gases and nutrients as the tammar trophoblast lacks the indentation by overlying vessels that is seen in the other near-term placentae. Early epitheliochorial placentae of other species with equal diffusion distances to the tammar, showed normal vascular glycosylation. However, their pregnancies are much longer. ConclusionThe hypoglycosylation of tammar vessels at the fetomaternal interface may allow continued transfer of nutrients and gaseous exchange during the extremely rapid period of organogenesis which occurs during the short 26.5 day pregnancy of this marsupial. Given the short gestation period of the tammar, we suggest that a thinner endothelial glycocalyx has evolved to facilitate diffusion of gases and nutrients between the maternal and fetal compartments.

Arginine, Leucine, and Glutamine Stimulate Proliferation of Porcine Trophectoderm Cells Through the MTOR-RPS6K-RPS6-EIF4EBP1 Signal Transduction Pathway1

During the peri-implantation and early placentation periods in pigs, conceptuses (embryo and its extra-embryonic membranes) undergo dramatic morphological changes and differentiation that require the exchange of nutrients (histotroph) and gasses across the trophectoderm and a true epitheliochorial placenta. Of these nutrients, arginine (Arg), leucine (Leu), and glutamine (Gln) are essential components of histotroph; however, little is known about changes in their total amounts in the uterine lumen of cyclic and pregnant gilts and their effects on cell signaling cascades. Therefore, we determined quantities of Arg, Leu, and Gln in uterine luminal fluids and found that total recoverable amounts of these amino acids increased in pregnant but not cyclic gilts between Days 12 and 15 after onset of estrus. We hypothesized that Arg, Leu, and Gln have differential effects on hypertrophy, hyperplasia, and differentiated functions of trophectoderm cells that are critical to conceptus development. Primary porcine trophectoderm (pTr) cells treated with either Arg, Leu, or Gln had increased abundance of phosphorylated RPS6K, RPS6, and EIF4EBP1 compared to basal levels, and this effect was maintained for up to 120 min. When pTr cells were treated with Arg, Leu, and Gln, low levels of pRPS6K and pEIF4EBP1 were detected in the cytosol, but the abundance of nuclear pRPS6K increased. Immunofluorescence analyses revealed abundant amounts of pRPS6 protein in the cytoplasm of pTr cells treated with Arg, Leu, and Gln. These amino acids also increased proliferation of pTr cells. Furthermore, when Arg, Leu, and Gln were combined with siRNAs for either MTOR, RPTOR, or RICTOR, effects of those amino acids on proliferation of pTr cells were significantly inhibited. Collectively, these results indicate that Arg, Leu, and Gln act coordinately to stimulate proliferation of pTr cells through activation of the MTOR-RPS6K-RPS6-EIF4EBP1 signal transduction pathway.