Extracellular matrix components of the placental extravillous trophoblast: immunocytochemistry and ultrastructural distribution

Engineering placental trophoblast fusion: A potential role for biomechanics in syncytialization

The process by which placental trophoblasts fuse to form the syncytiotrophoblast around the chorionic villi is not fully understood. Mechanical features of the in vivo and in vitro culture environments have recently emerged as having the potential to influence fusion efficiency, and considering these mechanical cues may ultimately allow predictive control of trophoblast syncytialization. Here, we review recent studies that suggest that biomechanical factors such as shear stress, tissue stiffness, and dimensionally-related stresses affect villous trophoblast fusion efficiency. We then discuss how these stimuli might arise in vivo and how they can be incorporated in cultures to study and enhance villous trophoblast fusion. We believe that this mechanical paradigm will provide novel insight into manipulating the syncytialization process to better engineer improved models, understand disease progression, and ultimately develop novel therapeutic strategies.

Controlling placental spheroid growth and phenotype using engineered synthetic hydrogel matrices

The human placenta is a complex organ comprised of multiple trophoblast subtypes, and inadequate models to study the human placenta in vitro limit the current understanding of human placental behavior and development. Common in vitro placental models rely on two-dimensional culture of cell lines and primary cells, which do not replicate the native tissue microenvironment, or poorly defined three-dimensional hydrogel matrices such as Matrigel™ that provide limited environmental control and suffer from high batch-to-batch variability. Here, we employ a highly defined, synthetic poly(ethylene glycol)-based hydrogel system with tunable degradability and presentation of extracellular matrix-derived adhesive ligands native to the placenta microenvironment to generate placental spheroids. We evaluate the capacity of a hydrogel library to support the viability, function, and phenotypic protein expression of three human trophoblast cell lines modeling varied trophoblast phenotypes and find that degradable synthetic hydrogels support the greatest degree of placental spheroid viability, proliferation, and function relative to standard Matrigel controls. Finally, we show that trophoblast culture conditions modulate cell functional phenotype as measured by proteomics analysis and functional secretion assays. Engineering precise control of placental spheroid development in vitro may provide an important new tool for the study of early placental behavior and development.

Engineered models for placental toxicology: Emerging approaches based on tissue decellularization

Recent increases in prescriptions and illegal drug use as well as exposure to environmental contaminants during pregnancy have highlighted the critical importance of placental toxicology in understanding and identifying risks to both mother and fetus. Although advantageous for basic science, current in vitro models often fail to capture the complexity of placental response, likely due to their inability to recreate and monitor aspects of the microenvironment including physical properties, mechanical forces and stiffness, protein composition, cell-cell interactions, soluble and physicochemical factors, and other exogenous cues. Tissue engineering holds great promise in addressing these challenges and provides an avenue to better understand basic biology, effects of toxic compounds and potential therapeutics. The key to success lies in effectively recreating the microenvironment. One strategy to do this would be to recreate individual components and then combine them. However, this becomes challenging due to variables present according to conditions such as tissue location, age, health status and lifestyle. The extracellular matrix (ECM) is known to influence cellular fate by working as a storage of factors. Decellularized ECM (dECM) is a recent tool that allows usage of the original ECM in a refurbished form, providing a relatively reliable representation of the microenvironment. This review focuses on using dECM in modified forms such as whole organs, scaffold sheets, electrospun nanofibers, hydrogels, 3D printing, and combinations as building blocks to recreate aspects of the microenvironment to address general tissue engineering and toxicology challenges, thus illustrating their potential as tools for future placental toxicology studies.

Human placental proteomics and exon variant studies link AAT/SERPINA1 with spontaneous preterm birth

BACKGROUND

Preterm birth is defined as live birth before 37 completed weeks of pregnancy, and it is a major problem worldwide. The molecular mechanisms that lead to onset of spontaneous preterm birth are incompletely understood. Prediction and evaluation of the risk of preterm birth is challenging as there is a lack of accurate biomarkers. In this study, our aim was to identify placental proteins that associate with spontaneous preterm birth.

METHODS

We analyzed the proteomes from placentas to identify proteins that associate with both gestational age and spontaneous labor. Next, rare and potentially damaging gene variants of the identified protein candidates were sought for from our whole exome sequencing data. Further experiments we performed on placental samples and placenta-associated cells to explore the location and function of the spontaneous preterm labor-associated proteins in placentas.

RESULTS

Exome sequencing data revealed rare damaging variants in SERPINA1 in families with recurrent spontaneous preterm deliveries. Protein and mRNA levels of alpha-1 antitrypsin/SERPINA1 from the maternal side of the placenta were downregulated in spontaneous preterm births. Alpha-1 antitrypsin was expressed by villous trophoblasts in the placenta, and immunoelectron microscopy showed localization in decidual fibrinoid deposits in association with specific extracellular proteins. siRNA knockdown in trophoblast-derived HTR8/SVneo cells revealed that SERPINA1 had a marked effect on regulation of the actin cytoskeleton pathway, Slit-Robo signaling, and extracellular matrix organization.

CONCLUSIONS

Alpha-1 antitrypsin is a protease inhibitor. We propose that loss of the protease inhibition effects of alpha-1 antitrypsin renders structures critical to maintaining pregnancy susceptible to proteases and inflammatory activation. This may lead to spontaneous premature birth.

CD42b Immunostaining as a Marker for Placental Fibrinoid in Normal Pregnancy and Complications

There are two types of fibrinoids within the placenta, fibrin-type and matrix-type. The clinical importance of these fibrinoids is poorly understood. Design: Fibrinoid deposits occurring in normal and complicated pregnancies were studies with H&E stain and CD42b as a marker for platelet aggregates. Results: Fibrin-like fibrinoid was associated with platelet aggregates positive by CD42b immunostaining in the subchorionic and basal plate areas, facing the maternal circulation and intervillous spaces. Matrix-type fibrinoid did not stain with CD42b, and it was found in the intervillous spaces, trophoblastic cysts, intravillous tissue areas, and vascular walls in decidual vasculopathy. Conclusion: Fibrin-type fibrinoid within the intervillous spaces are mostly from maternal circulation and these fibrinoids are likely the result of the laminar flow change at specific anatomic locations, leading to activation of coagulatory cascades. The pathogenesis of matrix-like fibrinoid is unclear. CD42b immunostaining is helpful in differentiation of the types of fibrinoid in difficult cases.

The Involvement of Cell Adhesion Molecules, Tight Junctions, and Gap Junctions in Human Placentation

Placentation is a major determinant of the success of pregnancy. It is regulated by several factors such as cell adhesion molecules, tight junctions, and gap junctions. The cell adhesion molecules are integrins, cadherins, immunoglobulins, nectins, and selectins. The tight junctions are composed of claudins, occludin, and junction adhesion molecule proteins while the gap junctions are composed of connexins of varying molecular weights. During placentation, some of these molecules regulate trophoblast proliferation, trophoblast fusion, trophoblast migration, trophoblast invasion, trophoblast-endothelium adhesion, glandular remodeling, and spiral artery remodeling. There is a dysregulated placental expression of some of these molecules during obstetric complications. We have, hereby, indicated the expression patterns of the subunits of each of these molecules in the various trophoblast subtypes and in the decidua, and have highlighted their involvement in physiological and pathological placentation. The available evidence points to the relevance of these molecules as distinguishing markers of the various trophoblast lineages and as potential therapeutic targets in the management of malplacentation-mediated diseases.

Mechanobiological regulation of placental trophoblast fusion and function through extracellular matrix rigidity

The syncytiotrophoblast is a multinucleated layer that plays a critical role in regulating functions of the human placenta during pregnancy. Maintaining the syncytiotrophoblast layer relies on ongoing fusion of mononuclear cytotrophoblasts throughout pregnancy, and errors in this fusion process are associated with complications such as preeclampsia. While biochemical factors are known to drive fusion, the role of disease-specific extracellular biophysical cues remains undefined. Since substrate mechanics play a crucial role in several diseases, and preeclampsia is associated with placental stiffening, we hypothesize that trophoblast fusion is mechanically regulated by substrate stiffness. We developed stiffness-tunable polyacrylamide substrate formulations that match the linear elasticity of placental tissue in normal and disease conditions, and evaluated trophoblast morphology, fusion, and function on these surfaces. Our results demonstrate that morphology, fusion, and hormone release is mechanically-regulated via myosin-II; optimal on substrates that match healthy placental tissue stiffness; and dysregulated on disease-like and supraphysiologically-stiff substrates. We further demonstrate that stiff regions in heterogeneous substrates provide dominant physical cues that inhibit fusion, suggesting that even focal tissue stiffening limits widespread trophoblast fusion and tissue function. These results confirm that mechanical microenvironmental cues influence fusion in the placenta, provide critical information needed to engineer better in vitro models for placental disease, and may ultimately be used to develop novel mechanically-mediated therapeutic strategies to resolve fusion-related disorders during pregnancy.

Potential of Membranes Surrounding the Fetus as Immunoprotective Cell-Carriers for Allogeneic Transplantations

Background

Membranes surrounding the fetus play a crucial role in providing a physical and immunological barrier between a semiallogeneic fetus and mother during pregnancy. In this study, we tested whether cotransplantation of fetal membranes (FMs) and allogeneic donor cells would improve the retention and function of allografts in mice.

Methods

Intact and enzyme-digested membranes obtained from E18-E19 pregnant mice were subcutaneously cotransplanted with 10F7MN hybridoma cells that are of BALB/cByJ (Balb) origin and secrete anti-human CD235a antibody. Cells were transplanted into C57BL/6J (B6, allogeneic), Balb (syngeneic), and FVB/NJ (third-party) mice. Serum was collected after 1 and 3 weeks of cell transplantation and tested using flow cytometry for the presence of anti-human CD235a antibody. Immunosuppressive functions of membranes were further investigated by analyzing the cytokine profile of supernatants collected from allo-reactive mixed lymphocyte reactions (MLRs) using a multiplex cytokine assay.

Results

B6 mice transplanted with 10F7MN cells along with membranes syngeneic to the host had significantly higher levels of CD235a antibody when compared to B6 mice that received cells without membranes, allogenic membranes, or third-party membranes. Syngeneic membranes significantly inhibited T-cell proliferation in the presence of allogeneic stimuli and suppressed the release of Th1-cytokines such as IFNγ, TNFα, and IL-2 in MLRs. Additionally, increases in the levels of Th2-cytokines were found in MLRs containing membrane-derived cells.

Conclusions

Our study highlights the potential use of syngeneic FMs to act as potent cell-carriers that could improve graft retention as well as graft-specific immunoprotection during allograft transplantation.

First trimester human placenta prevents breast cancer cell attachment to the matrix: The role of extracellular matrix

The extracellular matrix (ECM) affects cancer cell characteristics. Its detachment from the ECM induces cell apoptosis, termed anoikis. Cancer cells can develop anoikis resistance, a necessary step for metastasis, by switching integrins, over-expressing growth factor receptors, and inducing epithelial mesenchymal transition (EMT). The placenta is a non-supportive microenvironment for cancer cells. We showed that breast cancer cells (BCCL) were eliminated from placental implantation sites. During implantation, the placenta manipulates its surrounding matrix, which may induce BCCL elimination. Here, we explored the effect of placenta-induced ECM manipulations on BCCL. During experiments, BCCL (MCF-7/T47D) were cultured on placenta/BCCL-conditioned ECM (Matrigel used for first trimester placenta/BCCL culture and cleared by NH₄ OH). After culturing the cells, we analyzed cancer cell phenotype (death, count, aggregation, MMP) and signaling (microarray analysis and pathway validation). We found that the BCCL did not attach to previous placental implantation sites and instead, similarly to anoikis-resistant cells, migrated away, displayed increased MMP levels/activity, and formed aggregates in distant areas. T47D were less affected than the MCF-7 cells, since MCF-7 also showed modest increases in cell death, EMT, and increased proliferation. Microarray analysis of the MCF-7 highlighted changes in the integrin, estrogen, EGFR, and TGFβ pathways. Indeed, placental ECM reduced ERα, induced Smad3/JNK phosphorylation and increased integrin-α5 expression (RGD-dependent integrin) in the BCCL. Addition of RGD or TGFβR/JNK inhibitors reversed the phenotypic changes. This study helps explain the absence of metastases to the placenta and why advanced cancer is found in pregnancy, and provides possible therapeutic targets for anoikis-resistant cells. © 2016 Wiley Periodicals, Inc.

Collagen type IV at the fetal-maternal interface

Introduction

Extracellular matrix proteins play a crucial role in influencing the invasion of trophoblast cells. However the role of collagens and collagen type IV (col-IV) in particular at the implantation site is not clear.

Methods

Immunohistochemistry was used to determine the distribution of collagen types I, III, IV and VI in endometrium and decidua during the menstrual cycle and the first trimester of pregnancy. Expression of col-IV alpha chains during the reproductive cycle was determined by qPCR and protein localisation by immunohistochemistry. The structure of col-IV in placenta was examined using transmission electron microscopy. Finally, the expression of col-IV alpha chain NC1 domains and collagen receptors was localised by immunohistochemistry.

Results

Col-IV alpha chains were selectively up-regulated during the menstrual cycle and decidualisation. Primary extravillous trophoblast cells express collagen receptors and secrete col-IV in vitro and in vivo, resulting in the increased levels found in decidua basalis compared to decidua parietalis. A novel expression pattern of col-IV in the mesenchyme of placental villi, as a three-dimensional network, was found. NC1 domains of col-IV alpha chains are known to regulate tumour cell migration and the selective expression of these domains in decidua basalis compared to decidua parietalis was determined.

Discussion

Col-IV is expressed as novel forms in the placenta. These findings suggest that col-IV not only represents a structural protein providing tissue integrity but also influences the invasive behaviour of trophoblast cells at the implantation site.

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Our data suggest that progesterone might regulate collagen type IV.

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Primary extravillous trophoblast cells secrete collagen type IV.

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A novel three-dimensional network of collagen type IV in placenta is presented.

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Trophoblast cells express integrin alpha 10, integrin alpha 11 and collagen receptors DDR-1 and DDR-2.

Placental glucose transporter 3 (GLUT3) is up-regulated in human pregnancies complicated by late-onset intrauterine growth restriction

INTRODUCTION

Transport of glucose from maternal blood across the placental trophoblastic tissue barrier is critical to sustain fetal growth. The mechanism by which GLUTs are regulated in trophoblasts in response to ischemic hypoxia encountered with intrauterine growth restriction (IUGR) has not been suitably investigated.

OBJECTIVE

To investigate placental expression of GLUT1, GLUT3 and GLUT4 and possible mechanisms of GLUT regulation in idiopathic IUGR.

METHODS

We analyzed clinical, biochemical and histological data from placentas collected from women affected by idiopathic full-term IUGR (n = 10) and gestational age-matched healthy controls (n = 10).

RESULTS

We found increased GLUT3 protein expression in the trophoblast (cytotrophoblast greater than syncytiotrophoblast) on the maternal aspect of the placenta in IUGR compared to normal placenta, but no differences in GLUT1 or GLUT4 were found. No differential methylation of the GLUT3 promoter between normal and IUGR placentas was observed. Increased GLUT3 expression was associated with an increased nuclear concentration of HIF-1α, suggesting hypoxia may play a role in the up-regulation of GLUT3.

DISCUSSION

Further studies are needed to elucidate whether increased GLUT3 expression in IUGR is a marker for defective villous maturation or an adaptive response of the trophoblast in response to chronic hypoxia.

CONCLUSIONS

Patients with IUGR have increased trophoblast expression of GLUT3, as found under the low-oxygen conditions of the first trimester.

A variety of opportunities for immune interactions during trophoblast development and invasion

During human implantation and placentation, the direct cell to cell contact of fetal and maternal tissues gives room for a variety of immune interactions. Especially, the invasion of a subset of fetal trophoblast cells, called extravillous trophoblast, generate a very close interplay between the two individuals, enabling the attachment of the placenta to the uterine wall and the transformation of maternal spiral arteries to facilitate adequate nutrition of the fetus. During pregnancy, maternal and fetal factors closely interact to maintain pregnancy and smooth the process of delivery. At each and every stage and site, immunological interactions take place, including attachment of the blastocyst, development and invasion of trophoblast, and flow of maternal plasma and blood through the intervillous space of the placenta. Control mechanisms tightly regulate these interactions helping to evade fetal rejection by the mother. In this review, we highlight the morphological sites of development and feto-maternal interaction to help immunological interested scientists and clinicians to develop hypotheses on the feto-maternal immunological network during pregnancy.

An in vitro model for the study of human implantation

PROBLEM

Implantation remains the rate-limiting step for the success of in vitro fertilization. Appropriate models to study the molecular aspects of human implantation are necessary in order to improve fertility.

METHODS

First trimester trophoblast cells are differentiated into blastocyst-like spheroids (BLS) by culturing them in low attachment plates. Immortalized human endometrial stromal cells and epithelial cells (ECC-1) were stably transfected with GFP or tdTomato. Co-culture experiments were monitored using Volocity imaging analysis system.

RESULTS

This method demonstrates attachment and invasion of BLS, formed by trophoblast cells, into stromal cells, but not to uterine epithelial cells.

CONCLUSION

We have developed an in vitro model of uterine implantation. The manipulation of this system allows for dual color monitoring of the cells over time. Additionally, specific compounds can be added to the culture media to test how this may affect implantation and invasion. This model is a helpful tool in understanding the complexity of human implantation.

Differential response of arterial and venous endothelial cells to extracellular matrix is modulated by oxygen

Binding of endothelial cell (EC) integrins to extracellular-matrix (ECM) components is one of the key events to trigger intracellular signaling that will ultimately result in proper vascular development. Even within one tissue, the endothelial phenotype differs between arteries and veins. Here, we tested the hypothesis that anchorage dependent processes, such as proliferation, viability, survival and actin organization of venous (VEC) and arterial EC (AEC) differently depend on ECM proteins. Moreover,because of different oxygen tension in AEC and VEC, we tested oxygen as a co-modulator of ECM effects. Primary human placental VEC and AEC were grown in collagens I and IV, fibronectin, laminin, gelatin and uncoated plates and exposed to 12 and 21% oxygen. Our main findings revealed that VEC are more sensitive than AEC to changes in the ECM composition. Proliferation and survival of VEC, in contrast to AEC, were profoundly increased by the presence of collagen I and fibronectin when compared with gelatin or uncoated plates. These effects were reversed by inhibition of focal adhesion kinase (Fak) and modulated by oxygen. VEC were more susceptible to the oxygen dependent ECM effects than AEC. However, no differential ECM effect on actin organization was observed between the two cell types. These data provide first evidence that AEC and VEC from the same vascular loop respond differently to ECM and oxygen in a Fak-dependent manner.

Relevance of syndecan-1 in the trophoblastic BeWo cell syncytialization

PROBLEM

To investigate the role of syndecan-1 in the differentiation of the BeWo cells into syncytiotrophoblast.

METHOD OF STUDY

BeWo cells were stimulated with forskolin to form syncytia, and the expression of syndecan-1, desmoplakin I+II, human chorionic gonadotrophin (hCG) and angiogenesis-associated factors was analyzed. Syndecan-1 was silenced by siRNA to evaluate its involvement in the forskolin-mediated syncytia formation.

RESULTS

Treatment of the BeWo cells with forskolin led to a significant increase in the syncytia formation. It was associated with an increase in the expression of syndecan-1 with a concomitant decrease in the expression of desmoplakin I+II. Forskolin treatment of the BeWo cells also led to an increase in the secretion of soluble endoglin, whereas no change was observed in the soluble fms-like tyrosine kinase-1. Silencing of the syndecan-1 expression in BeWo cells led to a significant decrease in cell fusion both in the presence and in the absence of forskolin. It was associated with a significant decrease in hCG level in the conditioned medium.

CONCLUSION

Syndecan-1 is up-regulated in BeWo cells during differentiation and its silencing inhibits syncytialization and thus could be a useful biomarker for syncytiotrophoblast formation.

Effect of different concentrations of neogenin on proliferation, apoptosis and related proliferative factors in human trophoblasts

The underlying effect of different concentrations of neogenin on proliferation, apoptosis and the related proliferative factors in human trophoblasts was explored in order to understand the function of neogenin during placentation. TEV-1 cell line was cultured and the expression of netrin-1 was detected by using indirect cellular immunofluorescence. Exponentially growing TEV-1 cells were treated by different concentrations of neogenin (0, 1, 5, 10, 50 ng/mL) for 24 h. Cell viability was measured by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. TEV-1 cell apoptosis was assessed by flow cytometry (FCM). The expression of netrin-1 mRNA and protein in TEV-1 cells was examined by using real-time PCR and Western blot, respectively. It was found that immunoreactivity for netrin-1 was observed in cytoplasm of the trophoblasts. Immediately after treatment with different concentrations of neogenin for 24 h, the netrin-1 expression began to increase. Real-time PCR revealed that the expression level of netrin-1 mRNA was 37.59+/-10.25 times higher than control group when TEV-1 cells were exposed to 50 ng/mL neogenin (P<0.01), and the same tendency was seen by using Western blot. MTT results showed that proliferation of TEV-1 cells was independent of neogenin. Meanwhile, apoptosis was significantly increased to (22.15+/-6.15)% at 50 ng/mL neogenin and (6.55+/-0.25)% without neogenin (P<0.01). It is suggested that neogenin regulates proliferation and apoptosis of TEV-1 cells. And it can enhance the ability of TEV-1 cells to express netrin-1 in a dose-dependent manner. Neogenin may play an important biological role in the normal human pregnancy and contribute to the physiological pregnancy process.

Down syndrome screening: imagining the screening test of the future

Prenatal screening for Down syndrome (DS) is performed by risk calculation based on biochemical and biometric parameters. This way, approximately 75-85% of all DS cases can be detected. A way to improve detection rates is to search for new screening markers. Since the majority of biomarkers used in current DS screening are predominantly produced by the placenta, and the presence of an extra chromosome (as in DS) complicates placental development and function, it is plausible to assume that new potential screening markers may also originate from the placenta. Any alterations in these markers can be attributed to abnormal placental development and function. This article focuses on normal early placental development and function compared with that in DS pregnancies. Using this knowledge, we reason towards candidate biomarkers that may be useful in screening for DS.

A novel three-dimensional in vitro system to study trophoblast-endothelium cell interactions

INTRODUCTION

Pregnancy complications have been linked to improper trophoblast migration and failure of spiral artery transformation. Endothelial cells play an essential role in directing trophoblast migration and transformation, although by an unknown mechanism. We describe a novel in vitro model to evaluate endothelial-trophoblast interaction and signaling in a three-dimensional system.

METHOD OF STUDY

Immortalized human endometrial endothelial cell line and first trimester trophoblast cells were co-cultured. Endothelial transformation into vessel-like structures occurred in Matrigel(TM) OpenLab Image Analysis software was used to monitor labeled trophoblast migration and endothelium transformation. Cytokine/chemokine production was determined using Multiplex.

RESULTS

Trophoblast migrates toward endothelial cells in Matrigel, aligns on top of the endothelium within 4-8 hr and achieves complete replacement of the endothelium by 72-96 hr. Lipopolysaccharide treatment damages the endothelium and disrupts endothelium-trophoblast interaction.

CONCLUSION

We report a novel three-dimensional in vitro and in vivo system of trophoblast-endothelium cell interaction. Significant changes in endothelial cells' phenotype are observed upon differentiation in Matrigel. These changes may be necessary for endothelium to direct trophoblast migration and transformation.

The feto-maternal interface: setting the stage for potential immune interactions

Human implantation and placentation comprise the direct contact of fetal with maternal tissues culminating in the erosion of maternal tissues by fetal cells. A complex interplay of maternal and fetal factors is key to maintain pregnancy until delivery. Immunological interactions can be found at different stages, such as blastocyst attachment, trophoblast invasion into maternal tissues, and flow of maternal blood through the placenta. These interactions need tightly controlled mechanisms to avoid rejection of the conceptus. In this study, these sites of interaction are introduced on a morphological level to help immunologists create their hypotheses on how the immunological interactions may work.

Microscopic chorionic pseudocysts in placental membranes: a histologic lesion of in utero hypoxia

Grossly apparent and microscopically intermediate trophoblast-lined subchorionic, septal, and cell island cysts are relatively common placental findings. To analyze the clinicopathologic correlations of histologically similar but grossly inapparent microscopic chorionic pseudocysts (lakes) arising in the chorion laeve of placental membranes (mccpm), selected placental and clinical parameters of all 172 consecutive placentas with mccpm (study group, sg) and all consecutive 3743 placentas without mccpm (comparative group, cg) from years 1994 through 2005 were statistically compared; mccpm were observed in 4.3% of all placentas and in 14.9% of placentas from preeclamptic mothers from 24- to 42-week pregnancies, their gestational weeks' distribution almost mirroring that of the distribution of preeclampsia, with a peak in the middle of the 3rd trimester. Microscopic chorionic pseudocysts (lakes) arising in the chorion laeve of placental membranes were statistically significantly more common in patients with preeclampsia and maternal diabetes mellitus. In placentas with mccpm, decidual arteriolopathy, homogeneous placental maturation, global hypoxic pattern of placental injury, chorangiosis, placental infarction, laminar necrosis of membranes, stem obliterative endarteritis, erythroblasts of fetal blood, and decidual hemosiderosis were statistically significantly more common, while acute chorioamnionitis, villous fibrosis, and villous edema were less common (P < or = 0.05). There were no statistically significant differences between sg and cg in meconium staining, retroplacental hematoma, perivillous fibrin deposition, intervillous thrombi, chronic villitis, chorangiomas, placenta accreta, amnion nodosum, and marginate/vallate placenta. Highly statistically significant associations of mccpm with preeclampsia and a cluster of placental lesions known to be linked to placental hypoxia indicate that the mccpm form in response to hypoxia, particularly in patients with preeclampsia; mccpm should therefore be regarded and reported as a hypoxia-associated placental lesion.

Expression of syndecans, cell-cell interaction regulating heparan sulfate proteoglycans, within the human endometrium and their regulation throughout the menstrual cycle

OBJECTIVE

To evaluate the expression of syndecan-1, -2, -3, and -4 in different phases of eutopic endometrium of normal cycling women.

DESIGN

Prospective observational study.

SETTING

University-based research center for reproductive medicine.

PATIENT(S)

Twenty-nine healthy ovulatory volunteers.

INTERVENTION(S)

mRNA and protein expression of syndecan-1 to -4 in human endometrium.

MAIN OUTCOME MEASURE(S)

Real-time polymerase chain reaction of syndecan members and further characterization of mRNA expression of syndecan-1 and -4 with multiprobe RNase protection assays of epithelial and stromal cells after purification with antibody-coated magnetic beads. For confirmation of results, protein expression and localization using immunohistochemistry for syndecan-1 and -4 was performed.

RESULT(S)

All syndecans were expressed within human endometrium. Syndecan-1 and -4 proved to be significantly upregulated in whole endometrium during the secretory phase (2.73-fold and 2.85-fold, respectively). Using multiprobe RNase protection assays, a significant upregulation of mRNA was noted in epithelial cells during the secretory phase for both syndecan-1 and -4 (7.46-fold and 2.52-fold, respectively) and confirmed by immunohistochemistry.

CONCLUSION(S)

Cycle-dependent expression of syndecan-1 and -4 suggests that these adhesion proteins are involved in the regulation of the cycling endometrium.

The Uterine Spiral Arteries In Human Pregnancy: Facts and Controversies

Uterine spiral arteries play a vital role in supplying nutrients to the placenta and fetus, and for this purpose they are remodelled into highly dilated vessels by the action of invading trophoblast (physiological change). Knowledge of the mechanisms of these changes is relevant for a better understanding of pre-eclampsia and other pregnancy complications which show incomplete spiral artery remodelling. Controversies still abound concerning different steps in these physiological changes, and several of these disagreements are highlighted in this review, thereby suggesting directions for further research. First, a better definition of the degree of decidua- versus trophoblast-associated remodelling may help to devise a more adequate terminology. Other contestable issues are the vascular plugging and its relation with oxygen, trophoblast invasion from the outside or the inside of the vessels (intravasation versus extravasation), the impact of haemodynamics on endovascular migration, the replacement of arterial components by trophoblast, maternal tissue repair mechanisms and the role of uterine natural killer (NK) cells. Several of these features may be disturbed in complicated pregnancies, including the early decidua-associated vascular remodelling, vascular plugging and haemodynamics. The hyperinflammatory condition of pre-eclampsia may be responsible for vasculopathies such as acute atherosis, although the overall impact of such lesions on placental function is far from clear. Several features of the human placental bed are mirrored by processes in other species with haemochorial placentation, and studying such models may help to illuminate poorly understood aspects of human placentation.

Morphologic alterations in ovine placenta and fetal liver following induced severe placental insufficiency

OBJECTIVES

Umbilical-placental embolization with microspheres has been used as a model of placental insufficiency and intrauterine growth restriction (IUGR). However, the effects of embolization on placental structure and organ morphology of the resulting IUGR fetus are relatively unexplored. In this study using ovine fetuses, we determined the location and distribution of microspheres within the placenta and explored the extent of placental and fetal organ morphologic changes induced by placental embolization. We hypothesized that microspheres administered into the umbilical circulation over 4 days would cause placental damage without significant morphologic alterations in fetal kidney or liver.

METHODS

Eleven pregnant sheep at 118 +/- 1 (SE) days' gestation were studied. In six fetuses, embolization was induced by injections of 15-microm diameter microspheres on 4 successive days into the fetal descending aorta proximal to the umbilical arteries. Five fetuses served as time controls.

RESULTS

In embolized fetuses, microspheres were detected in the placenta embedded in the fetal cytotrophoblastic layer or maternal parenchyma adjacent to villous cytotrophoblasts. Fetal cytotrophoblasts appeared normal except for loss of distinct separation between fetal and maternal cell layers. Microspheres were also detected in the fetal membranes within capillaries. The body weights of embolized fetuses were lower than controls, as were the body weight-normalized liver but not kidney weights. In the liver of the embolized fetuses, the number of hematopoietic cell clusters was markedly reduced, whereas the fetal kidneys appeared normal.

CONCLUSIONS

We conclude that after 4 days of umbilical-placental embolization, microspheres were concentrated at the fetal villi proximal to the apical maternal-fetal interface and in the fetal membranes. There were noticeable morphologic changes in the embolized placentas, with no apparent gross damage to the placenta. The reduction in fetal liver weight and liver extramedullary hematopoietic cell abundance associated with embolization may predispose the fetus to alterations in liver function that could persist after birth.

Galectin fingerprinting in human endometrium and decidua during the menstrual cycle and in early gestation

The emerging functionality of the sugar code via cell surface glycans and endogenous lectins ascribes pertinent roles in cell physiology to the carbohydrate signals of cellular glycoconjugates. To initiate monitoring of endogenous lectins in human endometrium, we focused on a family of growth/adhesion-regulatory lectins, i.e. galectins. Comprehensive fingerprinting was performed on samples throughout the menstrual cycle and in decidua. The endometrium (n = 30) and decidua (n = 7) were collected from patients undergoing hysterectomy for benign reasons and from induced abortions. Measurements by RT-PCR and then by multiprobe RNase protection assay with total endometrial and decidual tissue and with epithelial cells, stromal cells and CD45-positive cell fractions (n = 16), isolated by the use of antibody-coated magnetic beads, revealed a predominant expression of galectins-1 and -3. Protein analysis was performed by immunocytochemistry with monoclonal and polyclonal antibodies (n = 40). Galectin-1 was localized mainly in stromal cells, whereas galectin-3 was predominantly found in epithelial cells. Expression of galectin-1 increased significantly in the late secretory phase endometrium and in the decidual tissue. Expression of galectin-3 increased significantly during the secretory phase of the menstrual cycle. Cycle-dependent expression of galectin-1 in stromal cells and galectin-3 in epithelial cells suggest these lectins to be involved in the regulation of different endometrial cellular functions.

Urokinase receptor is up-regulated in endothelial cells and macrophages associated with fibrinoid deposits in the human placenta

Clearance of fibrin deposits within the human placenta is an ongoing process during normal placental development. Plasminogen is a circulating fibrinolytic protease zymogen activated in situ by plasminogen activators. We have previously reported that the receptor for urokinase plasminogen activator (uPAR) is expressed by cells either covering or enmeshed within the perivillous fibrinoid deposits. Whereas these cells seemed likely to be trophoblasts, a definitive identification was lacking, and this question is central to the understanding of the cellular mechanisms directing fibrinolysis in the placenta. In this study we have performed immunohistochemical co-localization studies and found that the uPAR-positive cells covering fibrinoid deposits are immunoreactive for CD31 and vWF, indicating that they are actually endothelial cells. In addition, we found that perivillous fibrinoid deposits not covered with uPAR-positive endothelial cells were covered with platelets identified by integrin alpha(IIb)beta(3)-immunoreactivity. Also surprisingly, the uPAR-positive cells enmeshed within fibrinoid deposits express a cell specific marker indicating that they are macrophages. Both uPAR-positive cell populations also express uPA immunoreactivity. Taken together, the data suggest that both fibrinoid-covering endothelial cells and fibrinoid-enmeshed macrophages can participate in the clearance process of perivillous fibrinoid deposits formed in the human placenta.

Extracellular pH modulates the secretion of fibronectin isoforms by human trophoblast

Differentiation of human trophoblast from the proliferative to the invasive phenotype takes place in a hypoxic and thus likely an acidic microenvironment. During differentiation, the secretion pattern of fibronectin isoforms changes. Therefore, we analysed the relation between extracellular pH, secretion of fibronectin splice variants and invasiveness. By means of immunohistochemistry and biochemistry, cellular non-oncofetal fibronectins were found in placental stroma and around extravillous trophoblast, whereas oncofetal isoforms only marked the extracellular matrix of extravillous trophoblast. In vitro, mesenchymal cells produced non-oncofetal fibronectins only, whereas choriocarcinoma cell lines, extravillous trophoblast and choriocarcinoma/trophoblast hybrid cells secreted both non-oncofetal and oncofetal isoforms. When the pH of the culture medium was either lowered or increased (between 6.0 and 8.0), the trophoblast hybrids, but not choriocarcinoma and mesenchymal cells, responded with increased secretion of fibronectins and a shift towards oncofetal isoforms. These changes were preserved after pH normalisation. Histochemical determination of local tissue acidity revealed that the site of the lowest detectable tissue pK coincided with the starting point of invasion, the proximal part of trophoblastic cell columns. Therefore, it is concluded that the local pH plays an important role as regulator of differentiation of human trophoblast as reflected by the synthesis of oncofetal fibronectins by the invasive phenotype of extravillous trophoblast.

The placenta in pseudoxanthoma elasticum: clinical, structural and immunochemical study

Pseudoxanthoma elasticum (PXE) is a rare genetic disorder clinically characterized by skin, cardiovascular and eye manifestations, mainly due to calcification and fragmentation of elastic fibres. Although infrequent, complications during pregnancy in women affected by PXE have been reported. The aim of the present study was to compare structural features of placentae at term from 14 control and 15 PXE-affected women, in order to better understand if and how abnormal mineral and/or matrix accumulation might affect placental function in PXE. In all cases, pregnancy, fetus growth and delivery were normal. Both gross and light microscopy examination did not reveal dramatic differences between placentae of PXE patients and controls, with regard to weight, dimensions, infarcts, thrombi, inflammatory lesions or vessels. However, necrotic changes and mineralization appeared statistically more pronounced in PXE. By electron microscopy the most remarkable differences between PXE and control placentae were observed in the localization and morphology of mineral precipitates; a significant higher deposition of mineral precipitates was observed associated with the "matrix"-type fibrinoid and among collagen fibrils, especially on the maternal side. Immunocytochemistry revealed the presence of vitronectin and fibronectin associated with the PXE-specific mineralizations and the absence of mineralization on the small and scarce elastic fibres in either controls or in PXE.

Early Implantation Events in the Baboon (Papio anubis) with Special Reference to the Establishment of Anchoring Villi

The development of the baboon anchoring villus has been studied from day 14 to day 48 of gestation, using light and electron microscopy. At day 14, cords of trophoblast could be seen streaming into the endometrium, invading maternal vessels and forming blood-filled lacunae; by 20 days gestation some of these had differentiated into distinctive anchoring villi, with an outer covering of syncytiotrophoblast and inner cytotrophoblast cells which differed from those of floating villi in that a subpopulation detached from the syncytium to form an interconnecting network of cells within the centre of the villus. Subsequent migration of cytotrophoblast into the endometrium formed the cytotrophoblastic shell while fibrillin-like extracellular matrix biosynthesis within the body of the villus provided a firm mechanical support. At the trophoblast-decidual interface, a zone of necrosis and phagocytosis initially developed, which became less extensive with time, so that by 40 days a stable interface was evident with only residual pockets of necrosis. During this period, there was differentiation of decidual cells which by 28 days developed characteristic pedunculated cell processes, and later became surrounded by a basal lamina. The factors that control detachment of cytotrophoblast from the syncytium and the biosynthesis of the specialized, fibrillar extracellular matrix, features that are not apparent in other placental villi, require further investigation, possibly by carefully controlled in vitro experimentation.

Structure of anchoring villi and the trophoblastic shell in the human, baboon and macaque placenta

Anchoring villi of first trimester placentae of the macaque, baboon and human were examined by light and electron microscopy. The anchoring villi of the baboon and macaque are similar in having more elongated cell columns than those of the human and in having more extracellular matrix between cytotrophoblast cells. These species also have a thicker and more uniform trophoblastic shell. The generative region of cytotrophoblast cells adjacent to the villous mesenchyme is similar in all three species, with the aspect of the core abutting this area being lined by a thickened basal lamina. Similarly, migratory cytotrophoblast cells form extracellular matrix in all three species, but matrix-rich regions of the anchoring villi and shell are more extensive in the non-human primates. The extracellular matrix and especially the material resembling fibrillin may serve to strengthen the villi, particularly the elongated villi of the non-human primate, and also may prevent maternal cells migrating into the trophoblastic shell. The baboon and macaque cytotrophoblast cells that form this matrix tend to be linked by gap and desmosomal junctions and are in contiguous arrays, whereas those in the human that are blocked from reaching normal decidua form abundant extracellular matrix but have no gap junctions. Whether the lack of extensive invasion of the endometrium by baboon and macaque cytotrophoblast cells is related to the increased amount of extracellular matrix, their greater distance from the mesenchymal core, or their intercellular linkages is not known. The investigation of isolated villi from the macaque or baboon, as has been extensively carried out in the human, might help to determine whether the cytotrophoblast cells are intrinsically different or are responding to different environmental cues.

Expression of matrix metalloproteinase-2, -9, and -14, tissue inhibitors of metalloproteinase-1, and matrix proteins in human placenta during the first trimester

Matrix metalloproteinases (MMPs) are implicated in the degradation of extracellular matrix; they play important roles in the invasion of the trophoblast cell into the maternal endometrium during placentation. Previous studies have concentrated on comparison of MMP expression in trophoblast cells between the first and third trimester. But the dynamic expression of MMPs during the first trimester has not been reported. In the present study, the expression of MMP-2, -9, and -14 (membrane-type MMP-1) and the production of tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) by cultured human cytotrophoblast cells from 6 to 11 wk of gestation were investigated. The cells were cultured under serum-free conditions. There was no MMP-9 secretion by the cells at Week 6, but from Week 7 to 11 the MMP-9 secretion increased gradually. Week 11 cells secreted more than 10-fold as much MMP-9 (167.7 +/- 18.8 ng/ml) as Week 7 (14.7 +/- 3.9 ng/ml) cultures. However, MMP-2 production declined from Week 6 to Week 11, and the production at Week 11 (32.3 +/- 8.1 ng/ml) was about one sixth that at Week 6 (205.7 +/- 27.2 ng/ml). The expression of mRNA transcripts for MMP-2 and MMP-9 correlated with enzyme secretion; we did not detect any MMP-9 mRNA signal in 20 microg total RNA extracted from cultured cells at Weeks 6, 7, and 8 of pregnancy, but a signal was apparent in Weeks 9 and 11. MMP-2 mRNA was expressed throughout the 6- to 11-wk period and exhibited a remarkable decline during this period. MMP-14 mRNA transcripts remained relatively stable from 6 to 11 wk. Significantly more TIMP-1 (P < 0.01) was detected in Week 9 (87.5 +/- 15.0 ng/ml) and Week 11 (169.1 +/- 30.2 ng/ml) media compared to Week 6 media (23.5 +/- 4.8 ng/ml), but we did not detect any TIMP-2 in the media of the tested cells. This study demonstrated that first-trimester human cytotrophoblast cells were able to produce abundant laminin, fibronectin, and vitronectin. However, we did not observe detectable secretion of collagen I and collagen IV. These data indicated that human trophoblast-derived MMPs and their inhibitors are intrinsically and developmentally regulated. The same cytotrophoblast cells that produced MMPs could also secrete various substrates for these enzymes.

Microvascular and tumor cell alterations during continuous hyperfractionated irradiation: an electron microscopic investigation on the rat R1H rhabdomyosarcoma

PURPOSE

Conventionally fractionated y-irradiation results in severe damage of tumor capillaries associated with decreasing oxygen partial pressure within the tumor. The present study was undertaken to assess whether vasculo-connective changes are less pronounced after continuous hyperfractionated irradiation, implying better tumor oxygenation and improved radiosensitivity.

MATERIALS AND METHODS

Twenty rats with an isotransplanted R1H rhabdomyosarcoma were irradiated for 12 days with 2 daily fractions of 2.5 Gy (delta t = 6 h). After 0, 15, 30, 45, and 60 Gy, tumor tissue of 4 rats each was analyzed histologically and electron-microscopically.

RESULTS

Untreated rhabdomyosarcomas were composed of spindle-shaped tumor cells with numerous mitoses. There were many apoptotic nuclei and a large central necrosis. Tumor capillaries showed a continuous lining of flattened endothelial cells with broad overlapping cell contacts overlying a delicate continuous basal lamina. During irradiation, mean tumor volume declined from 1.9 cm3 to 1.2 cm3. The number of atypical mitoses and apoptoses increased and numerous giant tumor cells appeared. The proportion occupied by necrotic tumor tissue rose from 30% to 60%. After 15 Gy (3 days), a marked vasodilatation was apparent accompanied by an interstitial edema. Occasionally, endothelial cells were rounded up and showed indented nuclei, with the underlying basal lamina disintegrated. These changes progressed with increasing radiation doses. After 30 Gy (6 days), leukocytes started to adhere to the endothelial wall. Electron-dense fine fibrillar and basal lamina-like deposits appeared in the perivascular space. Endothelial cell edema was only observed after 60 Gy (12 days). Cell contact areas were shortened, however, the endothelial lining was not interrupted. No signs of radiation fibrosis were observed.

CONCLUSION

Continuous hyperfractionated irradiation induces relatively discrete alterations of the vasculo-connective tumor tissue as compared to conventional irradiation. This may be an advantage with respect to tumor blood flow, oxygenation, and thus, radiosensitivity.

Immunohistochemical identification of the receptor for urokinase plasminogen activator associated with fibrin deposition in normal and ectopic human placenta

The receptor for urokinase plasminogen activator (uPAR) is a key molecule in cell surface-directed plasminogen activation. uPAR binds urokinase plasminogen activator (uPA) and thereby focuses plasminogen activation on the cell surface. Plasmin dissolves fibrin deposits and facilitates cell migration during tissue repair processes by degrading the extracellular matrix. During human implantation and placental development, plasmin is considered important for both trophoblast migration/invasion and for fibrin surveillance. This study examined the expression of uPAR in normal and ectopic human placentae by immunohistochemistry. In first and third trimester normal placentae as well as in tubal ectopic placental tissues, a high uPAR expression was seen in the trophoblast associated with deposits of fibrin-type fibrinoid. Extravillous trophoblast of the basal plate, of the cell islands, and of the cell columns was also positive for uPAR in the first trimester whereas at term the expression of the protein was decreased. Moreover, uPAR immunostaining was observed in decidual cells throughout normal gestation and in endometrial tissues of patients with ectopic pregnancies. These findings suggest that uPAR participates in placental development and in trophoblast invasion particularly in the first trimester of pregnancy and that uPAR is involved in repair mechanisms of the trophoblast and fibrin surveillance.

The fibrinoids of the human placenta: origin, composition and functional relevance

Placental fibrinoids are extracellularly deposited materials which are histologically glossy and acid staining, and can be found in every normal and pathological placenta at all stages of pregnancy. The amount of fibrinoid is, in general, independent of pregnancy outcome and fetal wellbeing. According to new findings, the classical histological term "fibrinoid" covers two distinctive extracellular matrices which differ as regards structure, composition and function. Fibrin-type fibrinoid is mostly composed of fibrin together with other molecules derived from blood clotting or degenerative processes. It is mainly a maternal blood-clot product which is used (a) to adapt the intervillous space to optimized flow conditions and (b) to control growth of the villous trees by encasing new villous branches which caused intervillous stasis or turbulence of maternal blood. Moreover, fibrin-type fibrinoid replaces degenerative syncytiotrophoblast at the maternofetal exchange surfaces, thus acting as a kind of substitute barrier. Matrix-type fibrinoid is a secretory product of invasive extravillous trophoblast cells. It shares some similarities with basement membranes, however, it is secreted in an apolar fashion, embedding the secreting cells. Like basement membranes, it contains laminins, collagen IV, and heparan sulfate. In addition, oncofetal fibronectins, vitronectin, and i-glycosylated molecules but no collagens I, III, and VII can be found. Matrix-type fibrinoid is thought to regulate trophoblast invasion by specific interactions with cell surface integrins. As a kind of "glue", it anchors the placenta to the uterine wall and seems to play an important role in materno-fetal immune interactions at this particular site. Both types of fibrinoid are usually co-localized, thus indicating close morphogenetic and functional interrelations.