Fetal Trophoblast Cells Research Articles

Glycodelin-A Suppresses the Invasion of the Human Extravillous Cytotrophoblast.

The development of the placenta involves a series of complex, coordinated interactions between the fetal trophoblast cells and the maternal decidual cells. The invasion of the trophoblasts into the endometrium is crucial to placentation. The key cell in human placentation is the cytotrophoblast. After nidation, the cytotrophoblast differentiates into the villous cytotrophoblasts and the extravillous cytotrophoblasts (EVCTs). The invasive EVCTs appear as migratory cell columns invading through the endometrium. One of the invasive phenotypes of EVCTs is increased production of a set of extracellular matrix-degrading enzymes. Matrix metalloproteinases (MMP)-2 and MMP-9 are the most studied matrix-degrading enzymes in placental invasion and their proteinase activities are balanced by the tissue specific inhibitors of the MMPs (TIMP)-1 and TIMP-2. Glycodelin-A (GdA), a glycoprotein synthesized by the endometrial glands but not the trophoblast, is upregulated during first trimester which coincides with the time of trophoblast invasion. We hypothesize that glycodelin-A is a paracrine regulator generated by the deciduas that fine-tune the invasion process of human trophoblast. Trans-well invasion assay was used to examine the effect of GdA on the invasiveness of the immortalized first trimester extravillous cytotrophoblast (TEV-1) cell line. MMP2/MMP9 and TIMP1/TIMP2 secretions and activities were determined by ELISA and gelatin zymographic analysis respectively. Our results show that GdA significantly reduced the invasiveness and MMP2 secretion while increased the activities of TIMP-1 and TIMP-2 of TEV-1. No significant effect on MMP9 secretion was observed. Taken together, GdA may produce an inhibitory effect on trophoblast invasion by regulating the MMP pathways. Further works are required to characterize the biological role of GdA in trophoblast invasion.

REVIEW ARTICLE: NK Cell Tolerance and the Maternal–Fetal Interface

Natural killer (NK) cells play a fundamental role in the innate immune response through their ability to secrete cytokines and kill target cells without prior sensitization. These effector functions are central to NK cell anti‐viral and anti‐tumor abilities. Due to their cytotoxic nature, it is vital that NK cells have the capacity to recognize normal self‐tissue and thus prevent their destruction. In addition to their role in host defense, NK cells accumulate at the maternal‐fetal interface and are thought to play a critical role during pregnancy. The close proximity of uterine NK (uNK) cells to fetal trophoblast cells of the placenta would seemingly lead to catastrophic consequences, as the trophoblast cells are semi‐allogeneic. A fundamental enigma of pregnancy is that the fetal cells constitute an allograft but, in normal pregnancies, they are in effect not perceived as foreign and are not rejected by the maternal immune system. Although the mechanisms involved in achieving NK cell tolerance are becoming increasingly well‐defined, further clarification is required, given the clinical implications of this work in the areas of infection, transplantation, cancer and pregnancy. Herein, we discuss several mechanisms of NK cell tolerance and speculate as to how they may apply to uNK cells at the maternal–fetal interface.

Trophoblast Immune Receptors in Maternal-Fetal Tolerance

During pregnancy, interactions between maternal immune cells and fetal trophoblast cells of the placenta would seemingly lead to disaster, as the trophoblast cells are semi-allogeneic and should trigger rejection by the maternal immune response. A fundamental immunologic question of pregnancy as posed by Sir Peter Medawar centers on how immunologic disaster is averted. It is becoming clear that many different mechanisms act during gestation to render the maternal immune system tolerant of the fetus. These include, among others, restricted major histocompatibility complex (MHC) protein expression, the presence of immunosuppressive B7 family members, immunomodulatory adhesion molecules, the expression of apoptosis-inducing proteins, and complement regulatory proteins. Understanding of maternal-fetal tolerance has clinically important implications for the fields of reproduction, autoimmunity and transplantation. Herein are discussed mechanisms by which trophoblast cells are protected from maternal immune cell attack. Specifically the role of trophoblast cell surface proteins at the maternal-fetal interface is considered.

Matrix Metalloproteinase (MMP)‐2 and MMP‐9 Activity in the Canine Uterus Before and During Placentation

The aim of the present study was to demonstrate the presence and localization of MMP-2 and -9 by means of RT-PCR and immunohistochemistry (IHC) within the canine uterus from the pre-implantation stage until mid-gestation and to determine MMP-2 and -9 activities by means of zymography. For this purpose, samples of the uterus and salpinx from bitches were obtained after ovariohysterectomy. Pre-implantation stages (5-12 days after mating, n = 11) were determined by verifying embryos after flushing the uterus. Further groups were determined as implantation (15-19 days after mating, n = 9), post-implantation (20-30 days after mating, n = 9) and placental stages (30-45 days after mating, n = 3). A non-pregnant group (17-30 days after mating, n = 4) served as control. MMP-2 and -9 positive cells were detected in all specimens from pregnant and nonpregnant bitches, however, with different distributions. MMP-2 was present in endothelium and smooth muscles of blood vessels and the myometrium of pregnant and nonpregnant bitches, additionally in the surface epithelium of the oviduct. The latter also stained positive for MMP-9. During placentation, MMP-2 was detected mainly in fetal blood vessels and trophoblastic cells. Higher MMP-2 activity was observed in the endometrium and myometrium of all pregnant groups compared with the nonpregnant group (p < 0.05). The pregnant groups did not differ significantly from each other (p > 0.05). MMP-9 was present in blood vessels, smooth muscle cells and epithelia, such as maternal surface epithelial cells, uterine crypts and glands. During placentation, the deep uterine glands and the epithelium of the glandular chambers were immunoreactive to MMP-9. Highest MMP-9 activities were reached in the endometrium of the pre-implantation group (23.2% of total MMP-9) and placental parts (33.3%).

A homodimeric complex of HLA‐G on normal trophoblast cells modulates antigen‐presenting cells via LILRB1

In healthy individuals, the non-classical MHC molecule HLA-G is only expressed on fetal trophoblast cells that invade the decidua during placentation. We show that a significant proportion of HLA-G at the surface of normal human trophoblast cells is present as a disulphide-linked homodimer of the conventional β2m-associated HLA-I complex. HLA-G is a ligand for leukocyte immunoglobulin-like receptors (LILR), which bind much more efficiently to dimeric HLA-G than to conventional HLA-I molecules. We find that a LILRB1-Fc fusion protein preferentially binds the dimeric form of HLA-G on trophoblast cells. We detect LILRB1 expression on decidual myelomonocytic cells; therefore, trophoblast HLA-G may modulate the function of these cells. Co-culture with HLA-G+ cells does not inhibit monocyte-derived dendritic cell up-regulation of HLA-DR and costimulatory molecules on maturation, but did increase production of IL-6 and IL-10. Furthermore, proliferation of allogeneic lymphocytes was inhibited by HLA-G binding to LILRB1/2 on responding antigen-presenting cells (APC). As HLA-G is the only HLA-I molecule that forms β2m-associated dimers with increased avidity for LILRB1, this interaction could represent a placental-specific signal to decidual APC. We suggest that the placenta is modulating maternal immune responses locally in the uterus through HLA-G, a trophoblast-specific, monomorphic signal present in almost every pregnancy.See accompanying commentary: http://dx.doi.org/10.1002/eji.200737515

Validation of primary epitheloid cell cultures isolated from bovine placental caruncles and cotyledons

In order to study feto-maternal interactions in the bovine synepitheliochorial placenta primary cell cultures of both placentomal components throughout pregnancy, namely caruncular epithelial cells and trophoblast cells were developed. The aim of this study was to validate and improve a method to culture caruncular epithelial cells and fetal trophoblast from manually separated placentomes. Prior to seeding the presence of fetal cells in caruncular samples and vice-versa could be demonstrated by the detection of the Y-chromosome via fluorescence in situ hybridization (FISH) provided the fetus was male. Epitheloid shaped cells present in both cultures (cotyledon and caruncle) were characterized on a morphological basis as well as by immunofluorescence and Western blot thereby detecting cytokeratin, zonula occludens-1 and vimentin but not α-smooth muscle actin and desmin. The absence of the Y-chromosome demonstrated the caruncular origin of epitheloid cells. In addition, a population of polygonally shaped cells derived from the cotyledon was propagated and displayed the same cytoskeletal characteristics as described above. The presence of the Y-chromosome confirmed the fetal origin of these cells and the lacking uptake of fluorescence conjugated low density lipoprotein, specific for endothelial cells, identified polygonally shaped cells as fetal trophoblast cells. In conclusion, the cross-contamination of maternal and fetal cells in manually separated placentomes should be considered in future experiments as it may lead to false positive results dependent on the sensitivity of the method applied. This study highlights the importance of an appropriate cell characterization and identification, especially when isolating primary cells.

COMPARATIVE MORPHOLOGICAL FEATURES OF THE PLACENTAL BARRIER AND LOCALIZATION OF ESTROGEN RECEPTORS α IN THE PLACENTA OF COWS AND BUFFALOES

The present study was conducted to identify the morphological characteristics of the placental barrier and localization of estrogen receptors α in the cow and buffalo placentas. Placentomes were collected from 3 pregnant cows and 3 pregnant buffaloes at the 5th and 6th months of gestation respectively. The placentomes were fixed by using 10% neutral buffered formalin for immunohistochimestry and were post fixed in 3% glutaraldehyde for light microscopy. Indirect immunoperoxidase staining methods using monoclonal antibody against bovine ERα as primary antibody was applied. The morphometric data were obtained by using Q500 MC Image processing and analysis program. Histological examination revealed that there is a great similarity in the structure of the placental barrier of cows and buffaloes, whereas typical six slayers of tissue were seen separating the fetal blood from the maternal one. These layers were maternal endothelium, thin layer of maternal connective tissue, maternal uterine epithelial cells, fetal trophoblast cells, fetal connective tissue and fetal endothelium. Nuclear immunoreactivities occurred mainly in the maternal crypt epithelium and maternal connective tissue cells. In about 1000 maternal uterine cryptal cells, 87.6% were positive cells for ERα in the cow placenta and about 67.8% were positive cells in the buffalo placenta. The present study concluded that although there is a great similarity in the structure of the placental barrier and expression of ERα in the placentas of cows and buffaloes interbreeding between the two species is impossible due to the different number of chromosomes set. The placenta of cows seems to be less responsive to estrogen in comparison to that of buffaloes.

Genetic Deletion of Placenta Growth Factor in Mice Alters Uterine NK Cells

Placenta growth factor (PlGF; formerly PGF), a vascular endothelial growth factor gene family member, is expressed in human implantation sites by maternal uterine NK (uNK) and fetal trophoblast cells. Lower than normal concentrations of blood and urinary PlGF have been associated with impending onset of pre-eclampsia, a hypertensive disease of late human gestation characterized by limited intravascular trophoblast invasion. In pregnant rodents, delivery of the PlGF antagonist sFlt-1 or S-endoglin induces pre-eclampsia-like lesions. Mice genetically deleted in PlGF reproduce, but neither their implantation sites nor their uNK cell development are described. We combined real-time PCR of endometrium from nonpregnant and gestation day (gd)6-18 C57BL6/J (B6) mice with immunohistology to analyze PlGF expression in normal mouse pregnancy. To estimate the significance of uNK cell-derived PlGF, PlGF message was quantified in mesometrial decidua from pregnant alymphoid Rag2 null/common gamma chain null mice and in laser capture-microdissected B6 uNK cells. Histopathologic consequences from PlGF deletion were also characterized in the implantation sites from PlGF null mice. In B6, decidual PlGF expression rose between gd8-16. uNK cells were among several types of cells transcribing PlGF in decidualized endometrium. Immature uNK cells, defined by their low numbers of cytoplasmic granules, were the uNK cells displaying the greatest number of transcripts. PlGF deletion promoted the early differentiation high numbers of binucleate uNK cells (gd8) but had no other significant, morphometrically detectable impact on implantation sites. Thus, in mice, PlGF plays an important role in successful uNK cell proliferation and/or differentiation.

1A.1 Animal model of fetal loss in factor V Leiden carriers: pathogenic mechanism and therapeutic targets

Recurrent pregnancy loss (RPL), defined as two or more spontaneous abortions affects approximately 5% of all women of reproductive age. Epidemiological studies suggest that inherited and acquired thrombophilia of the mother, such as that caused by the Leiden polymorphism in blood coagulation factor V, contributes to the pathogenesis of fetal loss, as well as other adverse pregnancy outcomes [1 3]. These studies also demonstrate a high study-to-study variability of association strength, suggesting the existence of as yet uncharacterized risk modifiers. The pathogenesis of thrombophilia-associated fetal loss remains to be established. Evaluation of placental pathologies has not revealed a clear correlation between thrombophilia status of the mother and the presence of villous infarcts, blood clots or fibrin deposits in the placenta [4,5], raising the question whether thrombotic processes are indeed causative in thrombophilia-associated fetal loss or constitute an epiphenomenon. On the other hand, clinical trials suggest that heparin anticoagulation may indeed mitigate pregnancy failure in prothrombotic women [6 9]. In view of the uncertain etiology of thrombophilia-associated pregnancy failure, and the lack of established criteria for a more precise risk stratification enabling identification of truly atrisk pregnancies, the prophylactic anticoagulation of asymptomatic women and the risk-to-benefit balance of anticoagulation therapy during pregnancy are subjects of intense debate [10 12]. Pregnancy failure in carriers of the factor V Leiden (FVL) polymorphism, which renders coagulation factor V refractory to inactivating proteolysis by activated protein C, has not been replicated in experimental animal models. Homozygous status for the FVL polymorphism elicits pronounced thrombophilia in mice, but is not associated with intrauterine fetal loss or impaired fecundity [13]. In contrast, observations in animals lacking the receptor components of the protein C anticoagulant pathway, thrombomodulin (TM) and the endothelial protein C receptor (EPCR), demonstrate that the integrity of this pathway within the placenta is essential for the maintenance of pregnancy [14 16]. TMor EPCR knockout mice die in utero due to a placental malfunction that results from a lack of these receptors on trophoblast cells constituting fetal lining of the placental vascular bed. Placental malfunction is triggered by the initiator of blood coagulation, tissue factor (TF), and at least in the case of TM is not associated with thrombosis, nor prevented by the absence of fibrinogen [15]. These observations led us to propose a “coagulotoxic” mechanism distinct from thrombosis, in which localized, tissue factor-dependent engagement of coagulation factor receptors (i.e. PAR 1, PAR2, and PAR4) expressed by trophoblast cells would cause deleterious effects on placental growth and morphogenesis. Importantly, fetal loss in these animal models occurs in the absence of maternal thrombophilia. The relevance of these knockout models for fetal loss in thrombophilic mothers, and the pathogenesis of fetal loss remain unclear. Here, we experimentally test the role of coagulation receptors PAR1, 2, and 4 in the fetal loss of TM / embryos; and develop a mouse model of pregnancy loss in FVL carriers, in which fetal loss is triggered by the interaction of maternal FVL carrier status and reduced ability of fetal trophoblast cells to sustain the protein C anticoagulant pathway. Interaction of the same risk factors across the blood-endothelial interface of the systemic vasculature does not precipitate thrombosis. Fetal loss in this animal model is caused by defective placental morphogenesis in the absence of placental thrombosis, infarction or perfusion defects, and can be prevented by treatment with low molecular weight heparin, by platelet depletion, or by elimination of the thrombin receptor PAR4 from maternal platelets. Therapeutic intervention studies suggest that the efficacy of low molecular weight heparin in preventing fetal loss does not correlate with its anti-coagulant activity. These findings validate a cause effect relation between FVL carrier status and pregnancy failure, show that fetal

Selectin, Platelet Plays a Critical Role in Granulocyte Access to the Pregnant Mouse Uterus Under Physiological and Pathological Conditions1

Leukocyte recruitment to the pregnant mouse uterus is associated with highly regulated patterns of expression of vascular adhesion receptors. One striking observation is the localized expression of mucosal vascular addressin cell adhesion molecule (MADCAM1) and selectin, platelet (SELP, formerly P-selectin) by maternal vessels in the vascular zone (VZ) during the first half of pregnancy. From midgestation onwards, endothelial cells lining the maternal vessels of the VZ in addition express vascular cell adhesion molecule-1 (VCAM1). The predominant cell population within these vessels is monocyte-like cells. Granulocytes and low numbers of lymphocytes are also present. Murine fetal trophoblast cells are almost devoid of adhesion molecules, including SELP. In contrast, spontaneous abortions of allogeneic pregnancies are characterized by dramatic upregulation of SELP on maternal VZ vessels and on fetal trophoblast cells. Upregulation of SELP is associated with a dramatic influx of highly activated granulocytes, which infiltrate the vessels and tissue of the VZ and the trophoblast. The majority of the activated granulocytes within the trophoblast undergo nuclear fragmentation, which can be detected by TUNEL staining. To demonstrate that SELP is involved in the recruitment of granulocytes to the pregnant uterus, we undertook long-term in vivo inhibition studies using a monoclonal antibody to inhibit the contribution of SELP to leukocyte trafficking to the decidua. In addition, the pregnant uteri of syngeneic Selp(-/-) x Selp(-/-) mice were investigated and compared to the controls. Our results clearly demonstrate the importance of SELP for granulocyte access to the pregnant mouse uterus under physiological and pathological conditions.

Antibodies to Trophoblast Antigens HLA-G, Placenta Growth Factor, and NeuroD2 Do Not Improve Detection of Circulating Trophoblast Cells in Maternal Blood

Objectives: Non-invasive prenatal diagnosis using circulating fetal trophoblast cells has been challenging due to lack of a reproducible trophoblast-specific antibody. We investigated the use of three trophoblast cell-specific antibodies, HLA-G, placenta growth factor, and neuroD2, for the isolation of trophoblast cells from the maternal circulation. Methods: Trophoblast cells were isolated by density centrifugation from maternal blood samples (gestational age 10–20 weeks, n = 9). All women were carrying a male fetus. Following immunocytochemical staining with the trophoblast-specific antibodies, fluorescent in situ hybridization was performed, to verify whether any stained cells were indeed fetal. Results: The HLA-G antibody had a ubiquitous staining pattern, which was not specific for trophoblast cells. Neither the placenta growth factor nor the neuroD2 antibodies were able to identify any trophoblast cells. Following fluorescent in situ hybridization, no male cells were detected on any of the slides. Conclusion: The antibodies used in this study were unable to improve detection of trophoblast cells in the maternal circulation.

Soluble HLA-G promotes Th1-type cytokine production by cytokine-activated uterine and peripheral natural killer cells

Soluble forms of HLA-G (sHLA-G) have been implicated in immune regulation. Fetal trophoblast cells are a prime source of HLA-G. Hence, an interaction between sHLA-G and uterine lymphocytes in the decidual tissues can easily be envisaged. These lymphocytes, when properly activated, are implicated in successful trophoblast invasion, placental maturation and maintenance of pregnancy. However, so far, no data are available on the effect of sHLA-G on the function and phenotype of these cells. Herein, we used a recombinant sHLA-G construct to determine the effect of sHLA-G on uterine lymphocyte cells present in endometrium at the time that it is optimally receptive to trophoblast invasion. In addition, we ascertained the effect of sHLA-G on peripheral lymphocytes. We found that upon co-culture with sHLA-G, proliferation of unfractionated IL-15-stimulated uterine mononuclear cells (UMCs) was inhibited. However, sHLA-G increased both interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha production by these cells. Vascular endothelial growth factor (VEGF) production was reduced. Notably, in contrast to membrane-bound HLA-G, sHLA-G did not affect the natural cytolytic activity of UMCs. Similarly, sHLA-G inhibited proliferation but stimulated pro-inflammatory cytokine production by cytokine-activated, unfractionated peripheral blood mononuclear cells (PBMCs). In addition, we showed that the overall inhibitory effect of sHLA-G on proliferation of the whole cell population could be ascribed to selective inhibition of CD4(+) T cells. In contrast, sHLA-G induced proliferation and IFN-gamma production by both uterine and peripheral natural killer (NK) cells. In conclusion, our data show that the sHLA-G modulates both UMC and PBMC function. sHLA-G, by promoting IFN-gamma production by uterine NK cells, may contribute to vascular remodelling of spiral arteries to allow for successful embryo implantation.

Reduced maternal expression of adrenomedullin disrupts fertility, placentation, and fetal growth in mice

Adrenomedullin (AM) is a multifunctional peptide vasodilator that is essential for life. Plasma AM expression dramatically increases during pregnancy, and alterations in its levels are associated with complications of pregnancy including fetal growth restriction (FGR) and preeclampsia. Using AM+/- female mice with genetically reduced AM expression, we demonstrate that fetal growth and placental development are seriously compromised by this modest decrease in expression. AM+/- female mice had reduced fertility characterized by FGR. The incidence of FGR was also influenced by the genotype of the embryo, since AM-/- embryos were more often affected than either AM+/- or AM+/+ embryos. We demonstrate that fetal trophoblast cells and the maternal uterine wall have coordinated and localized increases in AM gene expression at the time of implantation. Placentas from growth-restricted embryos showed defects in trophoblast cell invasion, similar to defects that underlie human preeclampsia and placenta accreta. Our data provide a genetic in vivo model to implicate both maternal and, to a lesser extent, embryonic levels of AM in the processes of implantation, placentation, and subsequent fetal growth. This study provides the first genetic evidence to our knowledge to suggest that a modest reduction in human AM expression during pregnancy may have an unfavorable impact on reproduction.

Experimental Coxiella burnetii Infection in Pregnant Goats: a Histopathological and Immunohistochemical Study

Pregnant goats were inoculated subcutaneosly with Coxiella burnetii and the course of infection was studied. Abortion in the last third of pregnancy occurred in all infected animals. Tissues from the placenta and other organs were studied before and after abortion by immunohistochemistry and PCR analysis. After infection, mild lesions were observed in several maternal organs, mainly the mammary gland but also the lung and the liver. The trophoblast cells of the choriallantoic membrane were the first target cells of the placenta; there was, however, a substantial delay between initial infection and placental colonization. In the last weeks of pregnancy, just before abortion, massive bacterial multiplication was detected in the placenta. In this stage of infection a necrotic and suppurative placentitis separated the fetal trophoblast cells from maternal syncytial epithelium. Vasculitis was observed in the fetal mesenchyme. A strong maternal T-cell response was detected in the inter-placentomal areas but not in the placentomes, where only neutrophils and smaller numbers of macrophages were associated with the lesions. Neither lesions nor C. burnetii DNA were found in maternal organs in animals maintained until day 120 post-abortion.

Fetomaternal cross talk in the placental vascular bed: control of coagulation by trophoblast cells

AbstractHumans and rodents exhibit a peculiar type of placentation in which zygote-derived trophoblast cells, rather than endothelial cells, line the terminal maternal vascular space. This peculiar aspect of the placental vasculature raises important questions about the relative contribution of fetal and maternal factors in the local control of hemostasis in the placenta and how these might determine the phenotypic expression of thrombophilia-associated complications of pregnancy. Using genomewide expression analysis, we identify a panel of genes that determine the ability of fetal trophoblast cells to regulate hemostasis at the fetomaternal interface. We show that spontaneous differentiation of trophoblast stem cells is associated with the acquisition of an endothelial cell–like thromboregulatory gene expression program. This program is developmentally regulated and conserved between mice and humans. We further show that trophoblast cells sense, via the expression of protease activated receptors, the presence of activated coagulation factors. Engagement of these receptors results in cell-type specific changes in gene expression. Our observations define candidate fetal genes that are potential risk modifiers of maternal thrombophilia-associated pregnancy complications and provide evidence that coagulation activation at the fetomaternal interface can affect trophoblast physiology altering placental function in the absence of frank thrombosis.

Endocervical fetal trophoblast for prenatal genetic diagnosis

For over a decade, methods of first-trimester, noninvasive prenatal genetic diagnosis have been actively pursued by many investigators. Isolation of fetal trophoblast from endocervical specimens remains an attractive approach, given the greater numbers of fetal cells than in maternal blood and the better potential for fetal-cell identification based on markers specific for a single cell type (trophoblasts). Current studies demonstrate feasibility in identification and molecular analysis of fetal trophoblast cells for prenatal genetic testing. Sampling methods involving lavage, cytobrush, or aspiration of cervical specimens, however, have limitations in the recovery of trophoblasts. Clinical applications await further systematic studies to determine safety and accuracy in recovery.

Gene expression of the constant region of the heavy chain of immunoglobulin G (IgG CRHC) is down-regulated in human decidua in association with preeclampsia

An aberrant interaction at the maternal/fetal interface between the genetically distinct fetal trophoblast cells and cells of the maternal decidua has been proposed as an initiating factor in one of the major complications of human pregnancy, preeclampsia. Biochemical and epidemiological studies suggest that the immune system plays an important role in preeclampsia. Thus, the aim of this study was to determine the decidual gene expression status in preeclampsia of one of the key components of the adaptive immune system. Total RNA was extracted from decidua collected from women with normal pregnancies and those complicated by preeclampsia. Reverse Northern analysis was performed on 72 cDNAs from human decidua and differentially expressed genes identified were analysed further using semi-quantitative RT-PCR and Northern blot analysis. Expression of the gene encoding the constant region of the heavy chain of immunoglobulin G (IgG CRHC) was shown to be down-regulated in association with preeclampsia. These data support the hypothesis that immune maladaptation may play an important role in the pathogenesis of preeclampsia.

Activin A and Inhibin A Differentially Regulate Human Uterine Matrix Metalloproteinases: Potential Interactions during Decidualization and Trophoblast Invasion

Embryo implantation and trophoblast invasion are tightly regulated processes, involving sophisticated communication between maternal decidual and fetal trophoblast cells. Decidualization is a prerequisite for successful implantation and is promoted by a number of paracrine agents, including activin A. To understand the downstream mechanisms of activin-promoted decidualization, the effects of activin on matrix metalloproteinases (MMPs) (important mediators of decidualization) were investigated. Activin A stimulated endometrial production of proMMPs-2, -3, -7, -9, and active MMP-2. In contrast, inhibin A was a potent inhibitor of proMMP-2, and antagonized the effect of activin on MMPs. Activin is up-regulated with decidualization, and MMPs-2, -3, and -9 increase in parallel. Furthermore, proMMP-2 production is stimulated when decidualization is accelerated with activin, and suppressed when activin is neutralized, attenuating decidualization. These data support that activin A promotes decidualization through up-regulating MMPs. Previous in vitro evidence proposes further roles for activin and MMPs in promoting trophoblast invasion; therefore, we examined their interrelationships in early human implantation sites. MMPs-7 and -9 were produced by static cytotrophoblast subpopulations, whereas MMP-2 was strikingly up-regulated in invasive extravillous cytotrophoblasts (EVT). Maternal decidua is the primary source of activin, where a role in stimulating MMP-2 in iEVTs can be envisaged. Inhibin was absent from cytotrophoblast populations, except for a dramatic up-regulation in endovascular EVT plugs, coinciding with a down-regulation of MMP-2. This suggests that inhibin may have a role in the cessation of vascular invasion. These data support that activin, via effects on MMPs, is an important factor in the maternal-fetal dialog regulating implantation.

It's the trophoblast!

Comment on Li et al, page [2716][1] The study by Li and colleagues in this issue of Blood demonstrates the critical role that fetal trophoblast cells play in the control of the coagulation reaction in the mother's blood in the placenta, and for preventing fetal loss as a consequence of placental

Reduced Uterine Indoleamine 2,3‐Dioxygenase Versus Increased Th1/Th2 Cytokine Ratios as a Basis for Occult and Clinical Pregnancy Failure in Mice and Humans

Indoleamine 2,3-dioxygenase (IDO) expression in fetal trophoblast and decidual antigen-presenting cells has been proposed to inactivate maternal T cells and thereby prevent rejection of the "fetal allograft" in early pregnancy. Psychic stress has been proposed to cause miscarriages as well as infertility, at the same time in pregnancy when blockade of IDO causes loss, but the suggested mechanism of stress-triggered loss has been an increased ratio of pro-rejection Th1-type cytokines to anti-rejection Th2/3 cytokines. Could stress act by reducing IDO expression? Using DBA/2-mated A/J mice where stress causes early pregnancy failure, we examined the role of stress in reducing IDO versus increasing Th1/Th2 ratio in deciduas. IDO loss was also examined in human decidua associated with pregnancy failure. A post-implantation sonic stress increased the pregnancy failure rate, increased the Th1/Th2 ratio, but did not reduce IDO. IDO was reduced, and Th1/Th2 ratios increased in A/J mice pre-immunized against paternal DBA/2 antigens, and concomitant stress increased these effects. The rate of pregnancy failure was not further increased consistent with recent discoveries of factors that limit the impact of Th1 cytokines at the feto-maternal interface. In deciduas from spontaneous miscarriage patients, IDO(+) cell frequencies were low in only 30% of patients. CD3(+) T-cell numbers and percentage terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end-labelling (TUNEL)(+) apoptotic T cells were increased, but the level of IDO did not correlate with likelihood of apoptosis. Loss of an allogeneic embryo in early pregnancy is more likely to be due to a high Th1/Th2 ratio than loss of putative protection by IDO.