Maternal Spiral Arterioles Research Articles

A Pilot Study of Ultrasound Assessment of Umbilical Cord and Placental Vascular Flow for Cord Accident Stillbirth Prevention.

Our objective was to determine the feasibility and interobserver reliability of umbilical cord and placental arteriolar flow assessment in low-risk pregnancies near term. This was a prospective pilot study in low-risk pregnancies at 36 weeks with anterior placentas. We excluded any with an indication for antenatal testing or delivery before 39 weeks. Each participant underwent two ultrasounds by different examiners, which included arterial and venous velocimetry at three cord sites (fetal, free loop, and placental) in addition to maternal and fetal placental arterioles. The interobserver reliability was quantified using the Pearson correlation coefficient with that of standard clinical parameters serving as a benchmark for interpretation. Among 53 participants scanned at 356/7-371/7 weeks, the mean examination duration was 20.5 ± 4.2 minutes. Ascertainment success was high for measures at the free loop, placental cord insertion, and fetal placental arterioles (range 90.6%-99.1%) and was lower at the fetal cord insertion and maternal spiral arterioles (range 47.2%-87.7%). Interobserver reliability estimates for free-loop systolic/diastolic and pulsatility index ranged from 0.38 to 0.44. Interobserver reliability for experimental parameters varied by measurement site, and all were poor at the fetal insertion and in placental arterioles. Parameters had significant variation across cord sites (range 4.3%-21.7%). In our cohort, flow assessments of the free loop, placental insertion, and placental arterioles are feasible, but interrater reliability varies by measurement type and cord site. Future studies are needed to establish feasibility and reliability in nonanterior placentation and to assess clinical relevance.

The Link Between Human Menstruation and Placental Delivery: A Novel Evolutionary Interpretation: Menstruation and fetal placental detachment share common evolved physiological processes dependent on progesterone withdrawal.

A new interpretation of human menstruation is presented, resulting from a cross-disciplinary investigation of evolution, developmental biology, and physiology. A process evolutionarily associated with childbirth expresses itself as menstruation in women for whom frequent and continual failure to conceive has become the default situation. In humans and Old World primates, contractile uterine spiral arterioles evolved as the complement of the highly invasive hemochorionic placenta and is the selected phenotype. Placental progesterone withdrawal during the last stage of birth leads to arrested blood flow through maternal spiral arterioles, allowing detachment of the deciduous placenta with minimal maternal hemorrhage. In nonpregnant females, progesterone withdrawal from a degenerating corpus luteum initiates menstruation and stops blood flow through uterine spiral arterioles. Both events share similar physiological mechanisms and sequences. This explanation may improve our understanding of a recurrent event experienced by half of the human population and for a quarter of their adult reproductive life.

97. Effect of placental growth factor on trophoblast integration into endothelial cell networks in the presence of inflammation

Introduction Invasion of maternal spiral arterioles by trophoblast cells is fundamental to normal placental development. Abnormal spiral arteriole remodelling is often present in pregnancies affected by preeclampsia. Placental growth factor (PlGF) is produced by the placenta and this molecule is decreased during early pregnancy of women with preeclamptic pregnancy as compared to unaffected women. The influence of PlGF on the processes of early placentation is not known. Objectives To observe the effect of supplemental PlGF upon capillary-like uterine endothelial cell networks and a first trimester human trophoblast cell line in the presence or absence of inflammation induced by exogenous tumour necrosis factor-alpha (TNF- α ) . Methods 24-well tissue culture plates were coated with 300 uL of undiluted Matrigel and allowed to gelatinise at 37°C for 30 min. Fluorescent labelled uterine microvascular endothelial cells and HTR8/SVNeo cells were co-cultured (1 X 10 5 per well) for 20 h treated with PlGF (10 ng/mL) and/or TNF- α (0.5 ng/mL). Images were captured by fluorescence microscopy and analysed using ImageJ. Experiments were repeated 8 times, data was analysed using SPSS v24. Results TNF alpha reduced trophoblast cell integration into endothelial networks (Control vs TNF- α p = 0.006) but this was not ameliorated by addition of PlGF (TNF- α vs TNF- α + PlGF p > 0.9). Furthermore, PlGF supplementation itself did not improve cell integration (Control vs PlGF p = 0.2). Discussion PlGF not improve trophoblast cell integration into endothelial cell networks nor reverse the inhibitory effect of TNF- α .

Trophoblast lineage specification, differentiation and their regulation by oxygen tension.

Development of the early embryo takes place under low oxygen tension. Under such conditions, the embryo implants and the trophectoderm, the outer layer of blastocyst, proliferate, forming the cytotrophoblastic shell, the early placenta. The cytotrophoblasts (CTBs) are the so-called epithelial 'stem cells' of the placenta, which, depending on the signals they receive, can differentiate into either extravillous trophoblast (EVT) or syncytiotrophoblast (STB). EVTs anchor the placenta to the uterine wall and remodel maternal spiral arterioles in order to provide ample blood supply to the growing fetus. STBs arise through CTB fusion, secrete hormones necessary for pregnancy maintenance and form a barrier across which nutrient and gas exchange can take place. The bulk of EVT differentiation occurs during the first trimester, before the onset of maternal arterial blood flow into the intervillous space of the placenta, and thus under low oxygen tension. These conditions affect numerous signaling pathways, including those acting through hypoxia-inducible factor, the nutrient sensor mTOR and the endoplasmic reticulum stress-induced unfolded protein response pathway. These pathways are known to be involved in placental development and disease, and specific components have even been identified as directly involved in lineage-specific trophoblast differentiation. Nevertheless, much controversy surrounds the role of hypoxia in trophoblast differentiation, particularly with EVT. This review summarizes previous studies on this topic, with the intent of integrating these results and synthesizing conclusions that resolve some of the controversy, but then also pointing to remaining areas, which require further investigation.

Promoter Hypomethylation of Maspin Inhibits Migration and Invasion of Extravillous Trophoblast Cells during Placentation.

ObjectiveExtravillous trophoblast (EVT) cells invade the endometrium and the maternal spiral arterioles during the first trimester. Mammary Serine Protease Inhibitor (Maspin, SERPINB5) plays a putative role in regulating the invasive activity of cytotrophoblasts. The maspin gene is silenced in various cancers by an epigenetic mechanism that involves aberrant cytosine methylation. We investigated the effect of the methylation status of the maspin promoter on the maspin expression and the aggressiveness of EVT cells.MethodsWestern blotting was used to detect the maspin protein expression in EVT cells upon hypoxia. The proliferative ability, the apoptosis rate and the migration and invasiveness were measured with Cell Counting Kit-8 assay, Flow Cytometry technology and Transwell methods. Subsequently, we treated cells with recombinant maspin protein. The methylation degree of maspin promoter region upon hypoxia/ decitabine was detected by bisulfite sequencing PCR and methylation-specific PCR. Finally, we explored the effects of decitabine on maspin protein expression and the aggressiveness of EVT cells.ResultsHypoxia effectively increased maspin protein expression in EVT cells and significantly inhibited their aggressiveness. The addition of recombinant maspin protein inhibited this aggressiveness. Decitabine reduced the methylation in the maspin promoter region and effectively increased the maspin protein expression, which significantly weakened the migration and invasiveness of EVT cells.DiscussionThe methylation status of the maspin promoter is an important factor that affects the migration and invasion of EVT cells during early pregnancy. A decrease in the methylation status can inhibit the migration and invasion of EVT cells to affect placentation and can result in the ischemia and hypoxia of placenta.

A Comparative Pathophysiological Study of Normal and Growth Retarded Human Placental Tissue

This study compares the pathophysiology of normal and growth retarded human placental tissues. Female patients were recruited from the Antenatal Clinic of Dolu Specialist Hospital, Mafoluku, Oshodi, Lagos, between 2008 and 2012. A total of 48 normal term placentas and 15 placentas of known IUGR cases were used for this study. IUGR cases were confirmed on the basis of ultrasound follow-up and diagnosis. Normal term placentas were collected at the point of delivery by a consultant gynaecologist, the cords were clamped, and membranes were then carefully trimmed after which each placenta was weighed. About 1 cm thickness of both normal and growth retarded placenta tissues was cut, processed for hematoxylin and eosin stain, while tissues for enzyme (ALP) assay were homogenized in cold 0.5 M sucrose solution. Comparative analysis of the data was done using ANOVA;P<0.05was taken as significant. The photomicrographs were observed/studied under light microscope, using the X150 and X600 magnifications. It was revealed therein that placental tissues are homogenous (regionally), compromised of maternal spiral arterioles and deregulated villous vasculogenesis, and that there is a significant difference in the level of alkaline phosphatase enzyme. We therefore concluded that there is a distinct difference between the normal and growth retarded human placenta tissue.

Hypoxia-Induced Changes in the Bioactivity of Cytotrophoblast-Derived Exosomes

Migration of extravillous trophoblasts (EVT) into decidua and myometrium is a critical process in the conversion of maternal spiral arterioles and establishing placenta perfusion. EVT migration is affected by cell-to-cell communication and oxygen tension. While the release of exosomes from placental cells has been identified as a significant pathway in materno-fetal communication, the role of placental-derived exosomes in placentation has yet to be established. The aim of this study was to establish the effect of oxygen tension on the release and bioactivity of cytotrophoblast (CT)-derived exosomes on EVT invasion and proliferation. CT were isolated from first trimester fetal tissue (n = 12) using a trypsin-deoxyribonuclease-dispase/Percoll method. CT were cultured under 8%, 3% or 1% O2 for 48 h. Exosomes from CT-conditioned media were isolated by differential and buoyant density centrifugation. The effect of oxygen tension on exosome release (µg exosomal protein/106cells/48 h) and bioactivity were established. HTR-8/SVneo (EVT) were used as target cells to establish the effect (bioactivity) of exosomes on invasion and proliferation as assessed by real-time, live-cell imaging (Incucyte™). The release and bioactivity of CT-derived exosomes were inversely correlated with oxygen tension (p<0.001). Under low oxygen tensions (i.e. 1% O2), CT-derived exosomes promoted EVT invasion and proliferation. Proteomic analysis of exosomes identified oxygen-dependent changes in protein content. We propose that in response to changes in oxygen tension, CTs modify the bioactivity of exosomes, thereby, regulating EVT phenotype. Exosomal induction of EVT migration may represent a normal process of placentation and/or an adaptive response to placental hypoxia.

LAIR2-expressing extravillous trophoblasts associate with maternal spiral arterioles undergoing physiologic conversion

Leukocyte-associated immunoglobulin-like receptor 2 (LAIR2) was identified on a global gene expression microarray analysis of surplus chorionic villus sampling (CVS) tissues as down-regulated in the first trimester of preeclampsia pregnancies. LAIR2 is the soluble receptor counterpart to LAIR1, an inhibitory receptor found on multiple immune cell subsets. In situ and immunohistochemical studies have previously shown that placental expression of LAIR2 expression is highly restricted, confined to the more distal portions of extravillous trophoblast (EVT) cell columns. This study examines LAIR2 expression in deeper layers of trophoblasts in the placental implantation site, maternal decidua and maternal spiral arterioles. Immunohistochemical staining detected LAIR2 expression on a subset of EVT within the implantation site. This trophoblast included the invasive EVT infiltrating the maternal decidual vessels and the EVT forming the endovascular trophoblastic plugs. More specifically, LAIR2-positive EVT showed a striking predilection for maternal decidual arterioles and the immediately surrounding decidua. Moreover, the appearance of EVT expressing LAIR2 in these areas was contemporaneous with the process of spiral arteriole remodeling. Based on these findings, we suggest that LAIR2-expressing EVT may play an important role in the remodeling of maternal spiral arterioles.

Placental Protein 13 and Decidual Zones of Necrosis: An Immunologic Diversion That May be Linked to Preeclampsia

We evaluated the role of placental protein 13 (PP13; galectin 13) in the process of trophoblast invasion and decidual necrosis. Immunohistochemical analysis for PP13, immune cells, human placental lactogen, cytokeratin, and apoptosis markers was performed on 20 elective pregnancy termination specimens between 6 and 15 weeks of gestation. Placental protein 13 was localized to syncytiotrophoblasts in the chorionic villi and to occasional multinucleated luminal trophoblasts within converted decidual spiral arterioles. Cytotrophoblasts, anchoring trophoblasts, and invasive trophoblasts did not stain for PP13. Extracellular PP13 aggregates were found around decidual veins associated with T-cell-, neutrophil- and macrophage-containing decidual zones of necrosis (ZONEs). We hypothesize that PP13 is secreted into the intervillus space, drains through the decidua basalis veins, and forms perivenous PP13 aggregates which attract and activate maternal immune cells. Thus, syncytiotrophoblast-derived PP13 may create a ZONE that facilitates trophoblast invasion and conversion of the maternal spiral arterioles.

Intrauterine growth restriction, human placental development and trophoblast cell death

Intrauterine growth restriction (IUGR) is a failure to achieve the growth potential of a fetus that is promised by the genetic constitution and environmental influences endogenous to the pregnancy. Optimal placental development and the ability of the placenta to compensate for stimulus-induced injury are central in promotion of normal fetal growth. In this review, we will overview placental development with a focus on how villous structure relates to function. We will also describe the differentiation and turnover of villous trophoblast while highlighting selected features of microscopic placental injury. Histopathological studies of the placenta in IUGR indicate that abnormalities of the maternal spiral arterioles, dysregulated villous vasculogenesis, and abundant fibrin deposition are characteristic of the injuries associated with this condition. We identify selected insults, including oxidative stress and complement activation, and key pathways that regulate apoptosis in villous trophoblast, including increased p53 activity, altered translation of AKT and mTOR proteins, and the stress response of the endoplasmic reticulum. We surmise that trophoblast dysregulation at a subcellular level and loss of functional mass of villous trophoblast via cell death pathways are key contributors to the suboptimal placental performance that yields IUGR. We predict that a better understanding of placental dysfunction in IUGR will lead to targeted therapeutic options for this important clinical condition.

Modulation of Trophoblast Cell Death by Oxygen and EGF

Preeclampsia, a maternal hypertensive disease, is characterized by shallow invasion of the maternal spiral arterioles resulting in hypoxia/reperfusion type insult; however, the molecular mechanism is unknown. The aim of this study was to determine the mechanism of altered oxygen tension or inhibition of phosphatidyl-inositol-3-kinase (PI3K) on trophoblast survival and to investigate the effect of epidermal growth factor (EGF) on maintaining cellular integrity. We have used flow cytometry, immunoblotting, and fluoroimmunocytochemistry to study apoptosis in a characterized, spontaneously transformed first trimester extravillous-like trophoblast cell line that exhibits many characteristics of in vivo trophoblast. Time-dependent exposure of first trimester extravillous-like trophoblast to all oxygen tensions tested promoted dissipation of the mitochondrial membrane potential (psi(m)) and resulted in a significant increase in celldeath by 48 hr as determined by dual staining flow cytometry. Western blot analysis revealed expression ofcleaved caspase-3 and caspase-9 increased with time with hypoxia and hyperoxia promoting the greatest elevation indicating that longer duration of exposure to a change inoxygen tension causes increased apoptosis via a mitochondrial-mediated pathway. Disruption of the anti-apoptotic PI3K pathway by LY294002 (40 microM), its specific inhibitor, caused further significant dissipation of the psi(m) (p< 0.01) and cleavage of caspase-3. EGF was able to maintain the psi(m) and to prevent cleavage of caspase-3 even in the presence of LY294002, indicating that its survival effects were independent of the PI3K pathway. These results suggest that inhibition of the PI3K/Akt pathway can sensitize first-trimester trophoblast-like cells into oxygen-induced cell death and that EGF exerts its anti-apoptotic effect independently of PI3K/Akt.

Endometrial resection and subsequent pregnancy

Endometrial ablation techniques are intended to treat heavy menstrual bleeding effectively. They are therefore designed to do irreparable damage to endometrium and endometrial blood vessels and to reduce haemorrhage by occlusion or narrowing of these vessels. In pregnancy these same vessels would adapt following trophoblastic invasion to become the placental bed. Loss of the arterial muscular media creates a wider lumen and eliminates vascular endocrine constrictor sensitivity. This process, known as physiological adaptation (Brosens et al., 1967) permits an increase in blood ¯ ow with the effect of maintaining viable placental and fetal oxygenation. Although fertility is reduced after endometrial ablation, these methods cause damage to the endometrial blood vessels and women are offered sterilisation or recommended to use effective contraception. It is not difficult to hypothesise that severe damage to the endometrial vessels could cause problems with placentation or affect fetal growth in any subsequent pregnancy. Realistically, fertility control sometimes does not succeed, and Langdana and Mundow (2000) contribute another case report to the literature describing pregnancy following endometrial ablation (Opperman et al., 1998). Effective placentation normally depends on successful trophoblastic invasion, especially of the maternal spiral arterioles. This is coupled with villous angiogenesis, creating a rich vascular bed to sustain placental viability and function. Other less physiological vascular beds are capable of nurturing a healthy placenta to term, for example the mesentery in the relatively rare phenomenon of abdominal pregnancy. Ahmed and Kilby (1997) reviewed the relationship between the vascular adaptations of pregnancy and levels of oxygenation. Placental tissue contains abundant angiogenic growth factors and receptors. Vascular endothelial growth factor is critical for angiogenesis in the placenta and its activity increases in situations of reduced oxygen tension. Placental growth factor is down-regulated by hypoxia. Neither vascular endothelial growth factor nor placental growth factor change in density in severely growth restricted pregnancies, but vascular endothelial growth factor does increase in pre-eclampsia with a reduction in placental growth factor activity, leading to the hypothesis that hypoxia at the placental maternal interface may prevent the second wave of trophoblastic invasion.

HIV AND THE PLACENTA

The placenta provides nutrients and removes wastes from the fetus through various mechanisms of transfer, diffusion, carrier-mediated transport and active transport, and vesicular transfer. 14 In humans the placental barrier is hemochorial (i.e., the placental trophoblast surface is in direct contact with the maternal blood, forming the maternal–fetal interface). The fertilized ovum implants directly into the maternal endometrium within a week of fertilization. Anchoring villi form at the end of the fourth postmenstrual week. Specialized invasive trophoblasts, at the tips of the cytotrophoblast columns of the anchoring villi, invade maternal spiral arterioles of the endometrium and the inner third of the myometrium. This vascular adaptation is noted as early as 16 days after ovulation. 21 Communication between the developing intervillous space surrounding the villi and maternal blood supply is established by day 11 or 12, after ovulation. However, large amounts of maternal blood do not enter into the intervillous space until 8 weeks later. 32 The intervillous space, at term, holds approximately 400 to 500 mL of blood. 14 , 192 The trophoblast is an ectodermal covering of each villus. The villous barrier varies in thickness throughout gestation, initially being composed of syncytiotrophoblast, cytotrophoblast, and connective tissue stroma. Discontinuities begin to form in the syncytiotrophoblast layer at 9 to 12 weeks after menstruation. 145 Cytotrophoblast covers 50% only of the villous circumference in the second trimester and diminishes to 20% at term. 14 The formation of syncytial knots and vasculosyncytial membranes (VSM) beginning at 18 to 20 weeks gestation brings the fetal capillary in very close approximation to the maternal blood. The percentage of villous surface occupied by VSM varies from 0% at 12 weeks to nearly 30% at term. 71 The VSM constitutes the effective metabolic barrier between the fetal and maternal circulations and is composed of syncytiotrophoblast cytoplasm, trophoblast basement membrane, stromal connective tissue, vascular basement membrane, and capillary endothelium (Fig. 1) . The VSM becomes progressively thinner, measuring 1 to 3 μm at term, finally resulting in fusion of the capillary and trophoblast basement membrane. 14 The placental membranes are multilayered, composed of tissues from the inner cell mass (amnion), the trophoblast shell (chorionic mesoderm), with intervening connective tissue from the extraembryonic mesoderm. The chorion of the free membranes (chorion laeve) is intimately attached to the maternal decidua (Fig. 2) . Decidua, the endometrial stromal fibroblast, under progestational influences becomes apparent by the 28th day after menstruation and completely surrounds the implanted blastocyst. With growth of the gestational sac, there is obliteration of the uterine cavity as a feto-maternal tissue junction is established around the whole conceptus at 17 weeks after menstruation. The decidua at the base of the placenta comes into direct contact with the invasive fetal trophoblast of the anchoring villi (Fig. 3) . At this interface there is extensive mingling of fetal and maternal cells. The fetal trophoblast and maternal decidua are partially separated by a layer of fibrinoid. Increased fibrosis and acute or chronic inflammation may be seen with the implantation site particularly within basal villi. 71 Hofbauer cells are phagocytic cells of mesenchymal origin found in the stroma of villi, chorion, and amnion. They are present in the villi from the fourth week after ovulation, prior to the development of a bone marrow. They maintain their ability to undergo mitosis and self-replicate, in contrast to bone marrow-derived macrophages. These cells are relatively constant throughout gestation, comprise about 40% of the stromal cells, 76 and express the leukocyte antigens, CD4, CD45, CD68, and CD1a. 14 , 143

Histochemical evaluation of dipeptidyl peptidase IV in human placentae of pre-eclamptic patients: Enzyme activity in villous trophoblast correlates with gestational proteinuric hypertensive disorders

The placenta provides nutrients and removes wastes from the fetus through various mechanisms of transfer, diffusion, carrier-mediated transport and active transport, and vesicular transfer.14 In humans the placental barrier is hemochorial (i.e., the placental trophoblast surface is in direct contact with the maternal blood, forming the maternal–fetal interface).The fertilized ovum implants directly into the maternal endometrium within a week of fertilization. Anchoring villi form at the end of the fourth postmenstrual week. Specialized invasive trophoblasts, at the tips of the cytotrophoblast columns of the anchoring villi, invade maternal spiral arterioles of the endometrium and the inner third of the myometrium. This vascular adaptation is noted as early as 16 days after ovulation.21 Communication between the developing intervillous space surrounding the villi and maternal blood supply is established by day 11 or 12, after ovulation. However, large amounts of maternal blood do not enter into the intervillous space until 8 weeks later.32 The intervillous space, at term, holds approximately 400 to 500 mL of blood.14, 192The trophoblast is an ectodermal covering of each villus. The villous barrier varies in thickness throughout gestation, initially being composed of syncytiotrophoblast, cytotrophoblast, and connective tissue stroma. Discontinuities begin to form in the syncytiotrophoblast layer at 9 to 12 weeks after menstruation.145 Cytotrophoblast covers 50% only of the villous circumference in the second trimester and diminishes to 20% at term.14 The formation of syncytial knots and vasculosyncytial membranes (VSM) beginning at 18 to 20 weeks gestation brings the fetal capillary in very close approximation to the maternal blood. The percentage of villous surface occupied by VSM varies from 0% at 12 weeks to nearly 30% at term.71 The VSM constitutes the effective metabolic barrier between the fetal and maternal circulations and is composed of syncytiotrophoblast cytoplasm, trophoblast basement membrane, stromal connective tissue, vascular basement membrane, and capillary endothelium (Fig. 1). The VSM becomes progressively thinner, measuring 1 to 3 μm at term, finally resulting in fusion of the capillary and trophoblast basement membrane.14The placental membranes are multilayered, composed of tissues from the inner cell mass (amnion), the trophoblast shell (chorionic mesoderm), with intervening connective tissue from the extraembryonic mesoderm. The chorion of the free membranes (chorion laeve) is intimately attached to the maternal decidua (Fig. 2). Decidua, the endometrial stromal fibroblast, under progestational influences becomes apparent by the 28th day after menstruation and completely surrounds the implanted blastocyst. With growth of the gestational sac, there is obliteration of the uterine cavity as a feto-maternal tissue junction is established around the whole conceptus at 17 weeks after menstruation.The decidua at the base of the placenta comes into direct contact with the invasive fetal trophoblast of the anchoring villi (Fig. 3). At this interface there is extensive mingling of fetal and maternal cells. The fetal trophoblast and maternal decidua are partially separated by a layer of fibrinoid. Increased fibrosis and acute or chronic inflammation may be seen with the implantation site particularly within basal villi.71Hofbauer cells are phagocytic cells of mesenchymal origin found in the stroma of villi, chorion, and amnion. They are present in the villi from the fourth week after ovulation, prior to the development of a bone marrow. They maintain their ability to undergo mitosis and self-replicate, in contrast to bone marrow-derived macrophages. These cells are relatively constant throughout gestation, comprise about 40% of the stromal cells,76 and express the leukocyte antigens, CD4, CD45, CD68, and CD1a.14, 143