A repertoire of cell cycle regulators whose expression is coordinated with human cytotrophoblast differentiation

Negative energy balance affects perinatal ewe performance, rumen morphology, rumen flora structure, and placental function

This study investigated the effects of negative energy balance (NEB) on perinatal ewes, with a focus on changes in growth performance, serum biochemical parameters, rumen fermentation, ruminal bacteria composition, placental phenotype-related indicators, and expression levels of genes related to placental function. Twenty ewes at 130 days of gestation were randomly allocated to either the positive energy balance (PEB) or NEB groups. In the experiment, ewes in the PEB group were fed the same amount as their intake during the pre-feeding baseline period, while ewes in the NEB group were restricted to 70% of their individual baseline feed intake. The experiment was conducted until 42 days postpartum, and five double-lamb ewes per group were selected for slaughter. The results demonstrated that NEB led to a significant decrease in body weight, carcass weight, and the birth and weaning weights of lambs (P < 0.05). Additionally, NEB caused alterations in serum biochemical parameters, such as increased non-esterified fatty acids and β-hydroxybutyrate levels and decreased cholesterol and albumin levels (P < 0.05). Rumen fermentation and epithelial parameters were also affected, with a reduction in the concentrations of acetic acid, butyric acid, total acid and a decrease in the length of the rumen papilla (P < 0.05). Moreover, NEB induced changes in the structure and composition of ruminal bacteria, with significant differences in α-diversity indices and rumen microbial community composition (P < 0.05). Gene expression in rumen papilla and ewe placenta was also affected, impacting genes associated with glucose and amino acid transport, proliferation, apoptosis, and angiogenesis (P < 0.05). These findings screened the key microbiota in the rumen of ewes following NEB and highlighted the critical genes associated with rumen function. Furthermore, this study revealed the impact of NEB on placental function in ewes, providing a foundation for investigating how nutrition in ewes influences reproductive performance. This research demonstrates how nutrition regulates reproductive performance by considering the combined perspectives of rumen microbiota and placental function.

Placental T-Cadherin Correlates With Trophoblastic Invasion Anomalies: Placenta Percreta and Fetal Growth Restriction

In this study, we compared the placental T-cadherin staining intensity of pregnant women with placenta percreta (PP) and asymmetrical fetal growth restriction (FGR) compared with healthy control pregnancies. Placental T-cadherin levels of the placenta of 86 pregnant women in total, 25 with FGR, 30 with healthy pregnant subjects, and 31 with PP, were examined using monoclonal anti-T-cadherin (CDH13) antibody for immunohistochemical examination. In immunohistochemistry, H -scores were used for each group to compare the expression of T-cadherin in extravillous trophoblast (EVT) cells. T-cadherin H -score of EVTs was highest in the FGR group and the lowest in the PP group. The difference in H -score between the FGR group and the control group was not statistically significant ( P =0.344). The difference between the PP group and the other 2 groups was significant ( P <0.0001). Multivariable linear regression analysis with a stepwise elimination method was performed in order to identify demographic and clinical parameters with significant effects on the T-cadherin H -score of EVTs. The estimation results identified only the disease group as a significant predictor of the H -score of EVTs ( R2 =0.340, P <0.0001). The highest T-cadherin H -score of EVTs was found in the FGR group and the lowest in the PP group. The low T-cadherin H-score values in the PP group suggest that low T-cadherin EVTs may be associated with increased placental invasion. Likewise, despite the statistical insignificance, a higher T-cadherin H -score of EVTs in FGR compared with controls implies a decreased invasiveness of the placenta in FGR.

How trophoblasts fuse: an in-depth look into placental syncytiotrophoblast formation

In humans, cell fusion is restricted to only a few cell types under normal conditions. In the placenta, cell fusion is a critical process for generating syncytiotrophoblast: the giant multinucleated trophoblast lineage containing billions of nuclei within an interconnected cytoplasm that forms the primary interface separating maternal blood from fetal tissue. The unique morphology of syncytiotrophoblast ensures that nutrients and gases can be efficiently transferred between maternal and fetal tissue while simultaneously restricting entry of potentially damaging substances and maternal immune cells through intercellular junctions. To maintain integrity of the syncytiotrophoblast layer, underlying cytotrophoblast progenitor cells terminate their capability for self-renewal, upregulate expression of genes needed for differentiation, and then fuse into the overlying syncytium. These processes are disrupted in a variety of obstetric complications, underscoring the importance of proper syncytiotrophoblast formation for pregnancy health. Herein, an overview of key mechanisms underlying human trophoblast fusion and syncytiotrophoblast development is discussed.

Apelin, APJ, and ELABELA: Role in Placental Function, Pregnancy, and Foetal Development-An Overview

The apelinergic system, which includes the apelin receptor (APJ) as well as its two specific ligands, namely apelin and ELABELA (ELA/APELA/Toddler), have been the subject of many recent studies due to their pleiotropic effects in humans and other animals. Expression of these factors has been investigated in numerous tissues and organs—for example, the lungs, heart, uterus, and ovary. Moreover, a number of studies have been devoted to understanding the role of apelin and the entire apelinergic system in the most important processes in the body, starting from early stages of human life with regulation of placental function and the proper course of pregnancy. Disturbances in the balance of placental processes such as proliferation, apoptosis, angiogenesis, or hormone secretion may lead to specific pregnancy pathologies; therefore, there is a great need to search for substances that would help in their early diagnosis or treatment. A number of studies have indicated that compounds of the apelinergic system could serve this purpose. Hence, in this review, we summarized the most important reports about the role of apelin and the entire apelinergic system in the regulation of placental physiology and pregnancy.

Roles of Two Small Leucine-Rich Proteoglycans Decorin and Biglycan in Pregnancy and Pregnancy-Associated Diseases

Two small leucine-rich proteoglycans (SLRP), decorin and biglycan, play important roles in structural–functional integrity of the placenta and fetal membranes, and their alterations can result in several pregnancy-associated diseases. In this review, we briefly discuss normal placental structure and functions, define and classify SLRPs, and then focus on two SLRPs, decorin (DCN) and biglycan (BGN). We discuss the consequences of deletions/mutations of DCN and BGN. We then summarize DCN and BGN expression in the pregnant uterus, myometrium, decidua, placenta, and fetal membranes. Actions of these SLRPs as ligands are then discussed in the context of multiple binding partners in the extracellular matrix and cell surface (receptors), as well as their alterations in pathological pregnancies, such as preeclampsia, fetal growth restriction, and preterm premature rupture of membranes. Lastly, we raise some unanswered questions as food for thought.

Maternal Exposure to Oxidized Soybean Oil Impairs Placental Development by Modulating Nutrient Transporters in a Rat Model

INTRODUCTION

As an exogenous food contaminant, dietary oxidized lipid impairs growth and development, and triggers chronic diseases in humans or animals. This study explores the effects of soybean oil with different oxidative degree on the placental injury of gestational rats.

METHODS AND RESULTS

Thirty-two female adult rats are randomly assigned to four groups. The control group is fed the purified diet with fresh soybean oil (FSO), and the treatment groups are fed purified diets with lipid content replaced by oxidized soybean oil (OSO) at 200, 400, and 800 mEqO2 kg-1 from conception until delivery. On day 20 of gestation, OSO decreased placental and embryonic weights as the oxidative degree increased linearly and quadratically. The expression of Bax showed a linear increase, and Bcl-2 decreased as the oxidative degree increased. The expression of Fosl1 and Esx1 is linearly and quadratically decreased in OSO-treated groups than FSO group. OSO decreased the level of IL-10 but increased expression of IL-1β in placenta and plasma. OSO remarkably upregulates levels of Fatp1 and Glut1 and decreases expression of Snat2 and Glut3.

CONCLUSION

OSO aggravates placental injury by modulating nutrient transporters and apoptosis-related genes, impedes placental growth and development, and ultimately leads to the decrease of fetal weight.

Decorin expression in tubal ectopic and intrauterine pregnancies

OBJECTIVE

Decorin is a leucine-rich proteoglycan, affects the proliferation, migration, and invasion of extravillous trophoblasts (EVTs). In this study, we aimed to determine the localization of decorin in the implantation site in human tubal ectopic pregnancy, to compare decorin expression levels in ectopic and intrauterine pregnancy, and to investigate the relationship between implantation depth of the tubal wall and expression levels of decorin.

METHODS

15 patients underwent salpingectomy for tubal ectopic pregnancy and 15 underwent curettage for voluntary interruption of pregnancy were included. All blocks were stained with decorin immunohistochemical staining. Trophoblastic cells of tubal Stage I-III and tubal epithelial and stromal cells were analyzed in terms of presence and intensity of decorin staining.

RESULTS

Decorin was expressed in both tubal and intrauterine trophoblasts, stroma, and surface epithelium during the first trimester of pregnancy. Decorin staining intensity was significantly lower in the villous cytotrophoblasts and syncytiotrophoblasts in tubal ectopic pregnancies, compared to intrauterine pregnancies (p = 0.001 for both). Decorin staining intensity also significantly lower in the extravillous cytotrophoblasts and syncytiotrophoblasts in the tubal ectopic pregnancies (p = 0.002 and p = 0.001, respectively). There was no significant difference in the staining intensity of the trophoblasts and surface epithelial between Stage II and Stage III tubal invasion; however, the decorin expression was lower in the stroma in Stage III (p = 0.094).

CONCLUSION

Decorin expression is significantly lower in trophoblastic cells of tubal ectopic pregnancies than the intrauterine pregnancies. Although it remains limited to explain the underlying cellular mechanisms, decorin seems to play a role in the development of tubal pregnancy.

A crossroad between placental and tumor biology: What have we learnt?

Placenta in certain species including the human has evolved as a highly invasive tumor-like organ invading the uterus aned its vasculature to derive oxygen and nutrients for the fetus and exchange waste products. While several excellent reviews have been written comparing hemochorial placentation with tumors, no comprehensive review is available dealing with mechanistic insights into what makes them different, and what tumor biologists can learn from placental biologists, and vice versa. In this review, we analyze the structure-function relationship of the human placenta, emphasizing the functional need of the spatio-temporally orchestrated trophoblast invasiveness for fetal development and growth, and pathological consequences of aberrant invasiveness for fetal and maternal health. We then analyze similarities and differences between the placenta and invasive tumors in terms of hallmarks of cancer, some key molecules regulating their invasive functions, and how placental cancers (choriocarcinomas) or other cancers become refractory or even addicted to these invasion-restraining molecules. We cite in vitro models of human trophoblast and choriocarcinoma cell lines utilized to study mechanisms in normal placental development as well as those responsible for tumor progression. We discuss the pathobiology of hyper-invasive placentas and show thattrophoblastic neoplasias are a unique and heterogeneous class of tumors. We delve into the questions as to why metastasis from other organs rarely occurs at the placental site and whether pregnancy makes the mother more or less vulnerable to cancer-related morbidity/mortality. We attempt to compare trophoblast stem cells and cancer stem cells. Finally, we leave the readers with some thoughts as foods of future investigations.

Molecular and immunological developments in placentas

Cytotrophoblasts differentiate in two directions during early placentation: syncytiotrophoblasts (STBs) and extravillous trophoblasts (EVTs). STBs face maternal immune cells in placentas, and EVTs, which invade the decidua and uterine myometrium, face the cells in the uterus. This situation, in which trophoblasts come into contact with maternal immune cells, is known as the maternal-fetal interface. Despite fetuses and fetus-derived trophoblast cells being of the semi-allogeneic conceptus, fetuses and placentas are not rejected by the maternal immune system because of maternal-fetal tolerance. The acquired tolerance develops during normal placentation, resulting in normal fetal development in humans. In this review, we introduce placental development from the viewpoint of molecular biology. In addition, we discuss how the disruption of placental development could lead to complications in pregnancy, such as hypertensive disorder of pregnancy, fetal growth restriction, or miscarriage.

Maternal PM2.5 exposure and abnormal placental nutrient transport

Epidemiological studies of human and animal experiments indicated that gestational exposure to atmospheric pollutants could be followed by the abnormal placental development. However, the effects of this exposure on the placental transportation for nutrients have not been systematically investigated. In this study, fine particulate matters (PM_2.5) samples were collected in Taiyuan and pregnant rodent models were administered with 3 mg/kg b.w. PM_2.5 by oropharyngeal aspiration every other day starting on embryonic day 0.5 (E0.5). Then the pregnant mice were sacrificed and their placentas were collected at different time points. The results showed that maternal PM_2.5 exposure (MPE) disrupted the expression of proliferating cell nuclear antigen (PCNA) at all time points and inhibited the cell proliferation in placenta. Following that, the capacity for placental nutrient transport was impaired. The changes at E18.5 were observed most significantly, showing the altered mRNA expression of amino acid, long-chain polyunsaturated fatty acid (LCPUFA), glucose and folate transporters. In addition, the glycogen content was elevated at E18.5, and the triglyceride content was increased at E13.5 and E15.5 and decreased at E18.5 in the placenta after MPE. In a word, the adverse effect induced by MPE revealed that MPE led tothe disruption on the nutrient supply to the developing fetus via modulating the abundance of placental nutrient transporters (PNT).

Cytogenomics of six human trophoblastic cell lines

Trophoblastic cell lines are established models used to examine human placenta physiology and disease. We performed concurrent cytogenetic analyses of six established and well-studied trophoblastic cell lines including JAR, BeWo, JEG-3, AC-1M59, HTR8/SVneo, and ACH-3P. All cell lines showed near triploid or tetraploid karyotypes with unique inter- and intra-clonal aberrations, which result possibly from long-term culture or defects in the placenta or its malignant choriocarcinoma origin. Variable aneuploidy in 'standard' cell lines is under-appreciated and may not reflect the in vivo situation. It has the potential to negatively impact our understanding of normal cell function and cause disagreement between studies.

Maternal Obesity Alters Placental Cell Cycle Regulators in the First Trimester of Human Pregnancy: New Insights for BRCA1

In the first trimester of pregnancy, placental development involves a wide range of cellular processes. These include trophoblast proliferation, fusion, and differentiation, which are dependent on tight cell cycle control. The intrauterine environment affects placental development, which also includes the trophoblast cell cycle. In this work, we focus on maternal obesity to assess whether an altered intrauterine milieu modulates expression and protein levels of placental cell cycle regulators in early human pregnancy. For this purpose, we use first trimester placental tissue from lean and obese women (gestational week 5+0-11+6, n = 58). Using a PCR panel, a cell cycle protein array, and STRING database analysis, we identify a network of cell cycle regulators increased by maternal obesity in which breast cancer 1 (BRCA1) is a central player. Immunostaining localizes BRCA1 predominantly to the villous and the extravillous cytotrophoblast. Obesity-driven BRCA1 upregulation is not able to be explained by DNA methylation (EPIC array) or by short-term treatment of chorionic villous explants at 2.5% oxygen with tumor necrosis factor α (TNF-α) (50 mg/mL), leptin (100 mg/mL), interleukin 6 (IL-6) (100 mg/mL), or high glucose (25 nM). Oxygen tension rises during the first trimester, but this change in vitro has no effect on BRCA1 (2.5% and 6.5% O2). We conclude that maternal obesity affects placental cell cycle regulation and speculate this may alter placental development.

Development of the human placenta

The placenta is essential for normal in utero development in mammals. In humans, defective placental formation underpins common pregnancy disorders such as pre-eclampsia and fetal growth restriction. The great variation in placental types across mammals means that animal models have been of limited use in understanding human placental development. However, new tools for studying human placental development, including 3D organoids, stem cell culture systems and single cell RNA sequencing, have brought new insights into this field. Here, we review the morphological, molecular and functional aspects of human placental formation, with a focus on the defining cell of the placenta - the trophoblast.

Function of p21 (Cip1/Waf1/CDKN1A) in Migration and Invasion of Cancer and Trophoblastic Cells

Tumor progression and pregnancy have several features in common. Tumor cells and placental trophoblasts share many signaling pathways involved in migration and invasion. Preeclampsia, associated with impaired differentiation and migration of trophoblastic cells, is an unpredictable and unpreventable disease leading to maternal and perinatal mortality and morbidity. Like in tumor cells, most pathways, in which p21 is involved, are deregulated in trophoblasts of preeclamptic placentas. The aim of the present study was to enlighten p21’s role in tumorigenic choriocarcinoma and trophoblastic cell lines. We show that knockdown of p21 induces defects in chromosome movement during mitosis, though hardly affecting proliferation and cell cycle distribution. Moreover, suppression of p21 compromises the migration and invasion capability of various trophoblastic and cancer cell lines mediated by, at least partially, a reduction of the extracellular signal-regulated kinase 3, identified using transcriptome-wide profiling, real-time PCR, and Western blot. Further analyses show that downregulation of p21 is associated with reduced matrix metalloproteinase 2 and tissue inhibitor of metalloproteinases 2. This work evinces that p21 is involved in chromosome movement during mitosis as well as in the motility and invasion capacity of trophoblastic and cancer cell lines.

HLA-C promotes proliferation and cell cycle progression in trophoblast cells

Objectives: The development of maternal-fetal immune tolerance and adequate trophoblast function are essential for the establishment and maintenance of pregnancy. Human leukocyte antigen (HLA), the major histocompatibility complex (MHC) antigen specific to humans, plays an important role in placentation and is involved in many pregnancy-associated diseases. HLA-C is the only classical MHC I gene expressed at the maternal-fetal interface. To investigate whether HLA-C plays an independent role in regulating the development of trophoblasts, we explored the effect of HLA-C expression on placental development.Methods: The role of HLA-C in the growth and migration of trophoblast JAR and HTR-8/Svneo cell lines was investigated after HLA-C-expressing lentivirus transfection.Results: The MTT assay and colony formation assay showed that HLA-C promoted cell proliferation. Furthermore, cell cycle analysis showed that HLA-C overexpression accelerated the transition of trophoblast cells from the G0/G1 phase to the S phase. However, FACS analysis and migration assay indicated that HLA-C had no significant influence on trophoblast apoptosis and migration.Conclusion: Our study demonstrated for the first time that besides being involved in immune tolerance, HLA-C can directly promote placental growth without interacting with immune cells, which could provide a new insight into studying the functions of HLA-C at the maternal-fetal interface.

Genome amplification and cellular senescence are hallmarks of human placenta development

Genome amplification and cellular senescence are commonly associated with pathological processes. While physiological roles for polyploidization and senescence have been described in mouse development, controversy exists over their significance in humans. Here, we describe tetraploidization and senescence as phenomena of normal human placenta development. During pregnancy, placental extravillous trophoblasts (EVTs) invade the pregnant endometrium, termed decidua, to establish an adapted microenvironment required for the developing embryo. This process is critically dependent on continuous cell proliferation and differentiation, which is thought to follow the classical model of cell cycle arrest prior to terminal differentiation. Strikingly, flow cytometry and DNAseq revealed that EVT formation is accompanied with a genome-wide polyploidization, independent of mitotic cycles. DNA replication in these cells was analysed by a fluorescent cell-cycle indicator reporter system, cell cycle marker expression and EdU incorporation. Upon invasion into the decidua, EVTs widely lose their replicative potential and enter a senescent state characterized by high senescence-associated (SA) β-galactosidase activity, induction of a SA secretory phenotype as well as typical metabolic alterations. Furthermore, we show that the shift from endocycle-dependent genome amplification to growth arrest is disturbed in androgenic complete hydatidiform moles (CHM), a hyperplastic pregnancy disorder associated with increased risk of developing choriocarinoma. Senescence is decreased in CHM-EVTs, accompanied by exacerbated endoreduplication and hyperploidy. We propose induction of cellular senescence as a ploidy-limiting mechanism during normal human placentation and unravel a link between excessive polyploidization and reduced senescence in CHM.

Fine-Tuned and Cell-Cycle-Restricted Expression of Fusogenic Protein Syncytin-2 Maintains Functional Placental Syncytia

Many types of multinucleated cells (syncytia) generated by cell-cell fusion are post-mitotic, but it remains unclear how this state is maintained and why. Here, we utilized the fluorescent ubiquitination-based cell-cycle indicator (Fucci) reporter system to show that human placental trophoblast cells were all in the G0 phase before they fuse. Expression of the fusogenic protein (fusogen) Syncytin-2 was confined to G0 cells. Overexpression of Syncytin-2 in cycling cells overrode the cell-cycle restriction and enabled fusion of cells in the S/G2/M phases but resulted in the unstable syncytia retaining mitotic features. The Syncytin-2-induced syncytia were functionally compromised with respect to pathogen defense and hormone secretion. We found that, during trophoblast fusion, the cell-cycle inhibitor p21 interacted with the GCM1 transcription factor, and this complex bound to the promoter of Syncytin-2 and promoted its transcription. These findings demonstrate that G0-restricted Syncytin-2 expression is a prerequisite for development of functional post-mitotic syncytia.

CDK1 inhibition facilitates formation of syncytiotrophoblasts and expression of human Chorionic Gonadotropin

AIMS

The human placental syncytiotrophoblast (STB) cells play essential roles in embryo implantation and nutrient exchange between the mother and the fetus. STBs are polyploid which are formed by fusion of diploid cytotrophoblast (CTB) cells. Abnormality in STBs formation can result in pregnancy-related disorders. While a number of genes have been associated with CTB fusion the initial events that trigger cell fusion are not well understood. Primary objective of this study was to enhance our understanding about the molecular mechanism of placental cell fusion.

METHODS

FACS and microscopic analysis was used to optimize Forskolin-induced fusion of BeWo cells (surrogate of CTBs) and subsequently, changes in the expression of different cell cycle regulator genes were analyzed through Western blotting and qPCR. Immunohistochemistry was performed on the first trimester placental tissue sections to validate the results in the context of placental tissue. Effect of Cyclin Dependent Kinase 1 (CDK1) inhibitor, RO3306, on BeWo cell fusion was studied by microscopy and FACS, and by monitoring the expression of human Chorionic Gonadotropin (hCG) by Western blotting and qPCR.

RESULTS

The data showed that the placental cell fusion was associated with down regulation of CDK1 and its associated cyclin B, and significant decrease in DNA replication. Moreover, inhibition of CDK1 by an exogenous inhibitor induced placental cell fusion and expression of hCG.

CONCLUSION

Here, we report that the placental cell fusion can be induced by inhibiting CDK1. This study has a high therapeutic significance to manage pregnancy related abnormalities.

Altered downstream target gene expression of the placental Vitamin D receptor in human idiopathic fetal growth restriction

Fetal growth restriction (FGR) affects up to 5% of pregnancies and is associated with significant perinatal complications. Maternal deficiency of vitamin D, a secosteroid hormone, is common in FGR-affected pregnancies. We recently demonstrated that decreased expression of the vitamin D receptor (VDR) in idiopathic FGR placentae could impair trophoblast growth. As strict regulation of cell-cycle genes in trophoblast cells is critical for optimal feto-placental growth, we hypothesised that pathologically decreased placental VDR contributes to aberrant regulation of cell-cycle genes. The study aims were to (i) identify the downstream cell-cycle regulatory genes of VDR in trophoblast cells, and (ii) determine if expression was changed in cases of FGR. Targeted cell-cycle gene cDNA arrays were used to screen for downstream targets of VDR in VDR siRNA-transfected BeWo and HTR-8/SVneo trophoblast-derived cell lines, and in third trimester placentae from FGR and gestation-matched control pregnancies (n = 25 each). The six candidate genes identified were CDKN2A, CDKN2D, HDAC4, HDAC6, TGFB2 and TGFB3. TGFB3 was prioritised for further validation, as its expression is largely unknown in FGR. Significantly reduced mRNA and protein expression of TGFB3 was verified in FGR placentae and the BeWo and HTR-8/SVneo trophoblast cell lines, using real-time PCR and immunoblotting respectively. In summary, decreased placental VDR expression alters the expression of regulatory cell-cycle genes in FGR placentae. Aberrant regulation of cell-cycle genes in the placental trophoblast cells may constitute a mechanistic pathway by which decreased placental VDR reduces feto-placental growth.

Breaking down barriers: the evolution of cell invasion

Cell invasion is a specialized cell behavior that likely co-evolved with the emergence of basement membranes in metazoans as a mechanism to break down the barriers that separate tissues. A variety of conserved and lineage-specific biological processes that occur during development and homeostasis rely on cell invasive behavior. Recent innovations in genome editing and live-cell imaging have shed some light on the programs that mediate acquisition of an invasive phenotype; however, comparative approaches among species are necessary to understand how this cell behavior evolved. Here, we discuss the contexts of cell invasion, highlighting both established and emerging model systems, and underscore gaps in our understanding of the evolution of this key cellular behavior.

Divide or Conquer: Cell Cycle Regulation of Invasive Behavior

Cell invasion through the basement membrane (BM) occurs during normal embryonic development and is a fundamental feature of cancer metastasis. The underlying cellular and genetic machinery required for invasion has been difficult to identify, due to a lack of adequate in vivo models to accurately examine invasion in single cells at subcellular resolution. Recent evidence has documented a functional link between cell cycle arrest and invasive activity. While cancer progression is traditionally thought of as a disease of uncontrolled cell proliferation, cancer cell dissemination, a critical aspect of metastasis, may require a switch from a proliferative to an invasive state. In this work, we review evidence that BM invasion requires cell cycle arrest and discuss the implications of this concept with regard to limiting the lethality associated with cancer metastasis.

Effect of Cadmium on Trophoblast Cell Proliferation and Apoptosis in Different Gestation Periods of Rat Placenta

In this study, we aimed to show how cadmium (Cd) affects the trophoblast proliferation and differentiation in the placenta and the apoptotic activity in different gestational days and, hence, its effects of placental development with immunohistochemical and TUNEL techniques. Experimental model of our study consisted of placental development of control and Cd groups on 15, 17, 19, and 21th days of the gestation. Female rats in Cd groups were subcutaneously administered a single dose of 0.5 mg Cd/kg/day dissolved in sodium chloride as 2 mL/kg Cd chloride until the day they sacrificed. Embryo and placenta of female rats were separately removed on 15, 17, 19, and 21th days of the gestation in which the placental development takes place and placentas were processed for microscopic examinations. In the placentas of the control group, all layers were observed to be formed on the 15th gestational day and thereafter a continuous growth was monitored. In the Cd group also all layers existed from the 15th gestational day. However, they were smaller in size than control groups. Frequency of proliferating cell nuclear antigen (PCNA)-positive cells was decreased and the number of apoptotic cells was increased in all the gestational days related to Cd. In conclusion, Cd administered during the pregnancy was observed to cause abnormal placental development by disrupting the normal structure of the placenta, inhibiting the proliferation of trophoblast and increasing the number of apoptotic trophoblast cells.

CCN1 (CYR61) and CCN3 (NOV) signaling drives human trophoblast cells into senescence and stimulates migration properties

During placental development, continuous invasion of trophoblasts into the maternal compartment depends on the support of proliferating extravillous trophoblasts (EVTs). Unlike tumor cells, EVTs escape from the cell cycle before invasion into the decidua and spiral arteries. This study focused on the regulation properties of glycosylated and non-glycosylated matricellular CCN1 and CCN3, primarily for proliferation control in the benign SGHPL-5 trophoblast cell line, which originates from the first-trimester placenta. Treating SGHPL-5 trophoblast cells with the glycosylated forms of recombinant CCN1 and CCN3 decreased cell proliferation by bringing about G0/G1 cell cycle arrest, which was accompanied by the upregulation of activated Notch-1 and its target gene p21. Interestingly, both CCN proteins increased senescence-associated β-galactosidase activity and the expression of the senescence marker p16. The migration capability of SGHPL-5 cells was mostly enhanced in response to CCN1 and CCN3, by the activation of FAK and Akt kinase but not by the activation of ERK1/2. In summary, both CCN proteins play a key role in regulating trophoblast cell differentiation by inducing senescence and enhancing migration properties. Reduced levels of CCN1 and CCN3, as found in early-onset preeclampsia, could contribute to a shift from invasive to proliferative EVTs and may explain their shallow invasion properties in this disease.

Mechanisms of trophoblast migration, endometrial angiogenesis in preeclampsia: The role of decorin

The objective of the present review is to synthesize the information on the cellular and molecular players responsible for maintaining a homeostatic balance between a naturally invasive human placenta and the maternal uterus in pregnancy; to review the roles of decorin (DCN) as a molecular player in this homeostasis; to list the common maladies associated with a break-down in this homeostasis, resulting from a hypo-invasive or hyper-invasive placenta, and their underlying mechanisms. We show that both the fetal components of the placenta, represented primarily by the extravillous trophoblast, and the maternal component represented primarily by the decidual tissue and the endometrial arterioles, participate actively in this balance. We discuss the process of uterine angiogenesis in the context of uterine arterial changes during normal pregnancy and preeclampsia. We compare and contrast trophoblast growth and invasion with the processes involved in tumorigenesis with special emphasis on the roles of DCN and raise important questions that remain to be addressed. Decorin (DCN) is a small leucine-rich proteoglycan produced by stromal cells, including dermal fibroblasts, chondrocytes, chorionic villus mesenchymal cells and decidual cells of the pregnant endometrium. It contains a 40 kDa protein core having 10 leucine-rich repeats covalently linked with a glycosaminoglycan chain. Biological functions of DCN include: collagen assembly, myogenesis, tissue repair and regulation of cell adhesion and migration by binding to ECM molecules or antagonising multiple tyrosine kinase receptors (TKR) including EGFR, IGF-IR, HGFR and VEGFR-2. DCN restrains angiogenesis by binding to thrombospondin-1, TGFβ, VEGFR-2 and possibly IGF-IR. DCN can halt tumor growth by antagonising oncogenic TKRs and restraining angiogenesis. DCN actions at the fetal-maternal interface include restraint of trophoblast migration, invasion and uterine angiogenesis. We demonstrate that DCN overexpression in the decidua is associated with preeclampsia (PE); this may have a causal role in PE by compromising endovascular differentiation of the trophoblast and uterine angiogenesis, resulting in poor arterial remodeling. Elevated DCN level in the maternal blood is suggested as a potential biomarker in PE.

Human cytomegalovirus infection interferes with the maintenance and differentiation of trophoblast progenitor cells of the human placenta

Human cytomegalovirus (HCMV) is a major cause of birth defects that include severe neurological deficits, hearing and vision loss, and intrauterine growth restriction. Viral infection of the placenta leads to development of avascular villi, edema, and hypoxia associated with symptomatic congenital infection. Studies of primary cytotrophoblasts (CTBs) revealed that HCMV infection impedes terminal stages of differentiation and invasion by various molecular mechanisms. We recently discovered that HCMV arrests earlier stages involving development of human trophoblast progenitor cells (TBPCs), which give rise to the mature cell types of chorionic villi-syncytiotrophoblasts on the surfaces of floating villi and invasive CTBs that remodel the uterine vasculature. Here, we show that viral proteins are present in TBPCs of the chorion in cases of symptomatic congenital infection. In vitro studies revealed that HCMV replicates in continuously self-renewing TBPC lines derived from the chorion and alters expression and subcellular localization of proteins required for cell cycle progression, pluripotency, and early differentiation. In addition, treatment with a human monoclonal antibody to HCMV glycoprotein B rescues differentiation capacity, and thus, TBPCs have potential utility for evaluation of the efficacies of novel antiviral antibodies in protecting and restoring placental development. Our results suggest that HCMV replicates in TBPCs in the chorion in vivo, interfering with the earliest steps in the growth of new villi, contributing to virus transmission and impairing compensatory development. In cases of congenital infection, reduced responsiveness of the placenta to hypoxia limits the transport of substances from maternal blood and contributes to fetal growth restriction.

IMPORTANCE

Human cytomegalovirus (HCMV) is a leading cause of birth defects in the United States. Congenital infection can result in permanent neurological defects, mental retardation, hearing loss, visual impairment, and pregnancy complications, including intrauterine growth restriction, preterm delivery, and stillbirth. Currently, there is neither a vaccine nor any approved treatment for congenital HCMV infection during gestation. The molecular mechanisms underlying structural deficiencies in the placenta that undermine fetal development are poorly understood. Here we report that HCMV replicates in trophoblast progenitor cells (TBPCs)-precursors of the mature placental cells, syncytiotrophoblasts and cytotrophoblasts, in chorionic villi-in clinical cases of congenital infection. Virus replication in TBPCs in vitro dysregulates key proteins required for self-renewal and differentiation and inhibits normal division and development into mature placental cells. Our findings provide insights into the underlying molecular mechanisms by which HCMV replication interferes with placental maturation and transport functions.

Effects of maternal diabetes on trophoblast cells

Diabetes mellitus (DM) is a health condition characterized by hyperglycemia over a prolonged period. There are three main types of DM: DM type 1 (DM1), DM2 and gestational DM (GDM). Maternal diabetes, which includes the occurrence of DM1 and DM2 during pregnancy or GDM, increases the occurrence of gesttional complications and adverse fetal outcomes. The hyperglycemic intrauterine environment affects not only the fetus but also the placental development and function in humans and experimental rodents. The underlying mechanisms are still unclear, but some evidence indicates alterations in trophoblast proliferation, apoptosis and cell cycle control in diabetes. A proper coordination of trophoblast proliferation, differentiation and invasion is required for placental development. Initially, increased expression of proliferative markers in junctional and labyrinth zones of rat placentas and villous cytotrophoblast, syncytiotrophoblast, stromal cells and fetal endothelial cells in human placentas is reported among diabetics. Moreover, reduced apoptotic index and expression of some apoptotic genes are described in placentas of GDM women. In addition, cell cycle regulators including cyclins and cyclin-dependent kinase inhibitors seem to be affected by the hyperglycemic environment. More studies are necessary to check the balance between proliferation, apoptosis and differentiation in trophoblast cells during maternal diabetes.

Determination of PCNA, cyclin D3, p27, p57 and apoptosis rate in normal and dexamethasone-induced intrauterine growth restricted rat placentas

Intrauterine growth restriction (IUGR) is a major clinical problem, which causes perinatal morbidity and mortality. One of the reasons for IUGR is abnormal placentation. In rats, fetal-placental exposure to maternally administered glucocorticoids decreases birth weight and placental weight. Proper placental development depends on the proliferation and differentiation of trophoblasts. Our knowledge about the mitotic regulators that play key roles in synchronizing these events is limited. Also the mechanisms underlying the placental growth inhibitory effects of glucocorticoids have not been elucidated. The aim of this study was to investigate the immunolocalization, mRNA and protein levels of proliferating cell nuclear antigen (PCNA), cyclin D3, p27 and p57 in normal and dexamethasone-induced IUGR Wistar rat placentas by reverse transcriptase polymerase chain reaction (RT-PCR), immunohistochemistry and Western blot. We also compared apoptotic cell numbers at the light microscopic level via terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) and transmission electron microscopy. Glucocorticoid levels were higher in IUGR rats than in control rats after 60 and 120min of injection. We showed reduced gene and protein expressions of PCNA and cyclin D3 and increased expressions of p27 and p57 in IUGR placentas compared to control placentas. Apoptotic cell number was higher in the placentas of the IUGR group. In brief we found that maternal dexamethasone treatment led to a shift from cell proliferation to apoptosis in IUGR placentas. Dexamethasone induced placental and embryonal abnormalities which could be associated with reduced expressions of PCNA and cyclin D3, increased expressions of p27 and p57 and increased rate of apoptosis in IUGR placentas.

Proliferation of trophoblasts and Ki67 expression in preeclampsia

BACKGROUND/AIMS

Preeclampsia is a pregnancy-specific disease with the increased risk of maternal morbidity and mortality. It is characterised by placental vascular dysfunction. Despite the numerous studies on preeclampsia, studies evaluating proliferation of villous trophoblasts in preeclamptic placentas are limited. Ki67 is a proliferation marker that expresses in the nuclei of proliferating cells. In this study, we examined the proliferation of villous trophoblasts in placentas of preeclamptic patients by using Ki67 and compared it with placentas of normal pregnant patients.

MATERIAL AND METHODS

The current study is a prospective one, including 15 placentas from preeclamptic patients and 14 placentas from normal pregnancies as controls. For detection of proliferation in villous trophoblasts, Ki67 was used.

RESULTS

The Ki67 index was 11.48±1.67% in normal patients and 15.53±2.28% in preeclamptic patients. There was a difference in Ki67 index between the two groups (p < 0.001).

CONCLUSION

Our results support the opinion that trophoblasts undergo regeneration hyperplasia as a result of injuries arising on the villous surface in preeclampsia. Proliferation of trophoblasts may contribute the development of preeclampsia.

Notch-dependent RBPJκ inhibits proliferation of human cytotrophoblasts and their differentiation into extravillous trophoblasts

Abnormal development of invasive trophoblasts has been implicated in the pathogenesis of human pregnancy diseases such as pre-eclampsia. However, critical signalling pathways controlling formation and differentiation of these cells have been poorly elucidated. Here, we provide evidence that the canonical Notch pathway, operating through Notch-dependent activation of its key regulatory transcription factor RBPJκ, controls proliferation and differentiation in villous explant cultures and primary trophoblasts of early pregnancy. Immunofluorescence of first trimester placental tissue revealed expression of RBPJκ and its co-activators, the MAML proteins, in nuclei of proliferative cell column trophoblasts (CCT) and differentiated, extravillous trophoblasts (EVTs). However, RBPJκ expression, transcript levels of the Notch target gene HES1 and activity of a Notch/RBPJκ-dependent luciferase reporter decreased during in vitro differentiation of primary cytotrophoblasts on fibronectin. Silencing of RBPJκ using silencing RNAs (siRNAs) increased proliferation of CCTs in floating villous explant cultures analysed by outgrowth and BrdU labelling. Similarly, down-regulation of the transcription factor enhanced BrdU incorporation in isolated primary cultures. However, motility of these cells was not affected. In addition, gene silencing of RBPJκ increased cyclin D1 expression in the two trophoblast model systems as well as markers of the differentiated, EVT, i.e. integrin α1, ADAM12 and T-cell factor 4. In summary, the data suggest that Notch-dependent RBPJκ activity could be required for balanced rates of trophoblast proliferation and differentiation in human placental anchoring villi preventing exaggerated trophoblast overgrowth as well as premature formation of EVTs.

Immunolocalization of cell cycle proteins (p57, p27, cyclin D3, PCNA and Ki67) in intrauterine growth retardation (IUGR) and normal human term placentas

Placental development involves a series of events that depend on the coordinated action of proliferation, differentiation and invasion of trophoblasts. Studies on cell cycle related proteins controlling these events are fairly limited. It is still not fully determined how placental tissue proliferation is affected by intrauterine growth retardation (IUGR). Information on cell cycle related proteins that control these events is limited and how they are affected in IUGR is not fully understood. The aim of this study was to understand the role of cell cycle regulators in IUGR placentas and to determine the spatio-temporal immunolocalization of these cell cycle regulators in human IUGR and normal term placentas. Placental samples were stained immunohistochemically with PCNA, Ki67, cyclin D3, p27 and p57 antibodies and were examined by light microscopy. In all regions of IUGR placentas, PCNA, Ki67 and cyclin D3 staining intensities were statistically significantly decreased compared to normal controls. p27 staining intensity of the IUGR group was statistically significantly increased in villous parts and chorionic plates in comparison with the normal term placentas. Moreover, p57 staining intensity was statistically significantly increased in all parts of the IUGR group compared to controls. The observed placental abnormalities in IUGR placentas may be associated with arrest mechanisms affecting cell proliferation and cell cycle alterations in IUGR.

The role of apoptosis on trophoblast cell invasion in the placental bed of normotensive and preeclamptic pregnancies

BACKGROUND

Placental development depends on careful coordination of trophoblast proliferation and apoptosis; however, the synchrony of its effect on trophoblast invasion is unknown.

OBJECTIVE

To examine the relationship between trophoblast apoptosis and proliferation in placental bed tissue of preeclamptic and normotensive pregnancies.

METHODS

Serial sections from archived placental bed biopsies of 12 normotensive (group 1) and 12 preeclamptic (group 2) were immunolabeled with a rabbit anti-Ki67 antibody, a mouse anti-cytokeratin 18 and its neo-epitope, and a monoclonal cytodeath M30 antibody.

RESULTS

The immunoexpression of Ki67 for all trophoblast cell subpopulations within the myometrium was non-reactive in both study groups. Smooth muscle cells of the microvasculature reflected a moderate degree of proliferation in both groups. Morphometric image analysis of the wall of the spiral artery revealed a mean area of 31,1729 ± 51,180 µm(2) compared to 35,795 ± 8045 µm(2) in groups 1 and 2, respectively. An elevation of intramural trophoblast was evident within the spiral artery of group 1 (13%). Comparative analyses of M30 distribution on corresponding serial sections were 0.06% versus 0% in groups 1 and 2, respectively. The mean field area percentage of interstitial trophoblast invasion was 10.79% versus 2.87% with corresponding areas of apoptosis been 0.8 % versus 1.9 % in groups 1 and 2, respectively.

CONCLUSIONS

This study demonstrates an increased trophoblast apoptosis in placental bed of preeclamptic compared to normotensive pregnancies with concurrent absence of proliferation at term.

Analysis of human invasive cytotrophoblasts using multicolor fluorescence in situ hybridization

Multicolor fluorescence in situ hybridization, or FISH, is a widely used method to assess fixed tissues or isolated cells for numerical and structural chromosome aberrations. Unlike other screening procedures which provide average chromosome numbers for heterogeneous samples, FISH is a sensitive cell-by-cell method to analyze the distribution of abnormal cells in complex tissues. Here, we applied FISH to characterize chromosomal composition of a rare, but very important class of human cells that stabilize the fetal-maternal interface connecting the placenta to the uterine wall during early pregnancy, called invasive cytotrophoblasts (iCTBs). Combining differently-labeled, chromosome-specific DNA probes, we were able to unambiguously determine the number of up to six different autosomes and gonosomes in individual cell nuclei from iCTBs selected on the basis of their invasive behavior. In this manuscript, we describe a method for generation of iCTBs from placental villi, and provide the complete workflow of our FISH experiments including a detailed description of reagents and a trouble-shooting guide. We also include an in-depth discussion of the various types and sources of DNA probes which have evolved considerably in the last two decades. Thus, this communication represents both a complete guide as well as a valuable resource, intended to allow an average laboratory to reproduce the experiments and minimize the amount of specialized, and often costly, equipment.

Homeobox genes and down-stream transcription factor PPARγ in normal and pathological human placental development

The placenta provides critical transport functions between the maternal and fetal circulations during intrauterine development. Formation of this interface is controlled by nuclear transcription factors including homeobox genes. Here we summarize current knowledge regarding the expression and function of homeobox genes in the placenta. We also describe the identification of target transcription factors including PPARγ, biological pathways regulated by homeobox genes and their role in placental development. The role of the nuclear receptor PPARγ, ligands and target genes in human placental development is also discussed. A better understanding of these pathways will improve our knowledge of placental cell biology and has the potential to reveal new molecular targets for the early detection and diagnosis of pregnancy complications including human fetal growth restriction.

Human trophoblast progenitors: where do they reside?

In humans, very little is known about the factors that regulate trophoblast (TB) specification, expansion of the initial TB population, and formation of the cytotrophoblast (CTB) populations that populate the chorionic villi. The absence of human trophoblast progenitor cell (hTPC) lines that can be propagated in vitro has been a limiting factor. Because attempts to derive TB stem cells from the trophectoderm of the human blastocyst have so far failed, investigators use alternative systems as cell culture models including TBs derived from human embryonic stem cells (hESCs), immortalized CTBs, and cell lines established from TB tumors. Additionally, the characteristics of mature TBs have been extensively studied using primary cultures of CTBs and explants of placental chorionic villi. However, none of these models can be used to study TB progenitor self-renewal and differentiation. Furthermore, the propagation of human TB progenitors from villous CTBs (vCTBs) has not been achieved. The downregulation of key markers of cell cycle progression in vCTBs by the end of the first trimester of pregnancy may indicate that these cells are not a source of human TB progenitors later in pregnancy. In contrast, mesenchymal cells of the villi and chorion continue to proliferate until the end of pregnancy. We recently reported isolation of continuously self-renewing hTPCs from chorionic mesenchyme and showed that they differentiated into the mature TB cell types of the villi, evidence that they can function as TB progenitors. This new cell culture model enables a molecular analysis of the seminal steps in human TB differentiation that have yet to be studied in humans. In turn, this information can be used to trace the origins of pregnancy complications that are associated with faulty TB growth and differentiation.

Extravillous trophoblast and decidual natural killer cells: a remodelling partnership

BACKGROUND

During pregnancy, maternal uterine spiral arteries (SAs) are remodelled from minimal-flow, high-resistance vessels into larger diameter vessels with low resistance and high flow. Fetal extravillous trophoblasts (EVT) have important roles in this process. Decidual natural killer cells (dNK cells) are the major maternal immune component of the decidua and accumulate around SAs before trophoblast invasion. A role for dNK cells in vessel remodelling is beginning to be elucidated. This review examines the overlapping and dissimilar mechanisms used by EVT and dNK cells in this process and how this may mirror another example of tissue remodelling, namely cancer development.

METHODS

The published literature was searched using Pubmed focusing on EVT, dNK cells and SA remodelling. Additional papers discussing cancer development are also included.

RESULTS

Similarities exist between actions carried out by dNK cells and EVT. Both interact with vascular cells lining the SA, as well as with each other, to promote transformation of the SA. EVT differentiation has previously been likened to the epithelial-mesenchymal transition in cancer cells, and we discuss how dNK-EVT interactions at the maternal-fetal interface can also be compared with the roles of immune cells in cancer.

CONCLUSIONS

The combined role that dNK cells and EVT play in SA remodelling suggests that these interactions could be described as a partnership. The investigation of pregnancy as a multicellular system involving both fetal and maternal components, as well as comparisons to similar examples of tissue remodelling, will further identify the key mechanisms in SA remodelling that are required for a successful pregnancy.

Immunolocalization of PCNA, Ki67, p27 and p57 in normal and dexamethasone-induced intrauterine growth restriction placental development in rat

Intrauterine growth restriction (IUGR) is a major clinical problem which causes perinatal morbidity and mortality. Although fetuses with IUGR form a heterogeneous group, a major etiological factor is abnormal placentation. Despite the fact that placental development requires the coordinated action of trophoblast proliferation and differentiation, there are few studies on cell cycle regulators, which play the main roles in the coordination of these events. Moreover it is still not determined how mechanisms of coordination of proliferation and differentiation are influenced by dexamethasone-induced IUGR in the placenta. The aim of the study was to investigate the spatial and temporal immunolocalization of proliferating cell nuclear antigen (PCNA), Ki67, p27 and p57 in normal and IUGR placental development in pregnant Wistar rats. The study demonstrated altered expressions of distinct cell cycle proteins and cyclin dependent kinase inhibitors (CKIs) in IUGR placental development compared to control placental development. We found reduced immunostaining of PCNA and Ki67 and increased immunostaining of p27 and p57 in the dexamethasone-induced IUGR placental development compared to control placental development. In conclusion, our data show that the cell populations in the placenta stain for a number of cell cycle related proteins and that these staining patterns change as a function of both gestational age and abnormal placentation.

Caspase-mediated apoptosis of trophoblasts in term human placental villi is restricted to cytotrophoblasts and absent from the multinucleated syncytiotrophoblast

Human placental villi are surfaced by a multinucleated and terminally differentiated epithelium, the syncytiotrophoblast, with a subjacent layer of mononucleated cytotrophoblasts that can divide and fuse to replenish the syncytiotrophoblast. The objectives of this study were i) to develop an approach to definitively identify and distinguish cytotrophoblasts from the syncytiotrophoblast, ii) to unambiguously determine the relative susceptibility of villous cytotrophoblasts and syncytiotrophoblast to constitutive and stress-induced apoptosis mediated by caspases, and iii) to understand the progression of apoptosis in villous trophoblasts. Confocal microscopy with co-staining for E-cadherin and DNA allowed us to clearly distinguish the syncytiotrophoblast from cytotrophoblasts and identified that many cytotrophoblasts are deeply interdigitated into the syncytiotrophoblast. Staining for specific markers of caspase-mediated apoptosis indicate that apoptosis occurs readily in cytotrophoblasts but is remarkably inhibited in the syncytiotrophoblast. To determine if an apoptotic cell or cell fragment was from a cytotrophoblast or syncytiotrophoblast, we found co-staining with E-cadherin along with a marker for apoptosis was essential: in the absence of E-cadherin staining, apoptotic cytotrophoblasts would easily be mistaken as representing localized regions of apoptosis in the syncytiotrophoblast. Regions with perivillous fibrin-containing fibrinoid contain the remnants of trophoblast apoptosis, and we propose this apoptosis occurs only after physical isolation of a region of the syncytium from the main body of the syncytium. We propose models for the progression of apoptosis in villous cytotrophoblasts and for why caspase-mediated apoptosis does not occur within the syncytium of placental villi.

Somatic genomic variations in extra-embryonic tissues

In the mature chorion, one of the membranes that exist during pregnancy between the developing fetus and mother, human placental cells form highly specialized tissues composed of mesenchyme and floating or anchoring villi. Using fluorescence in situ hybridization, we found that human invasive cytotrophoblasts isolated from anchoring villi or the uterine wall had gained individual chromosomes; however, chromosome losses were detected infrequently. With chromosomes gained in what appeared to be a chromosome-specific manner, more than half of the invasive cytotrophoblasts in normal pregnancies were found to be hyperdiploid. Interestingly, the rates of hyperdiploid cells depended not only on gestational age, but were strongly associated with the extraembryonic compartment at the fetal-maternal interface from which they were isolated. Since hyperdiploid cells showed drastically reduced DNA replication as measured by bromodeoxyuridine incorporation, we conclude that aneuploidy is a part of the normal process of placentation potentially limiting the proliferative capabilities of invasive cytotrophoblasts. Thus, under the special circumstances of human reproduction, somatic genomic variations may exert a beneficial, anti-neoplastic effect on the organism.

The role of placental homeobox genes in human fetal growth restriction

Fetal growth restriction (FGR) is an adverse pregnancy outcome associated with significant perinatal and paediatric morbidity and mortality, and an increased risk of chronic disease later in adult life. One of the key causes of adverse pregnancy outcome is fetal growth restriction (FGR). While a number of maternal, fetal, and environmental factors are known causes of FGR, the majority of FGR cases remain idiopathic. These idiopathic FGR pregnancies are frequently associated with placental insufficiency, possibly as a result of placental maldevelopment. Understanding the molecular mechanisms of abnormal placental development in idiopathic FGR is, therefore, of increasing importance. Here, we review our understanding of transcriptional control of normal placental development and abnormal placental development associated with human idiopathic FGR. We also assess the potential for understanding transcriptional control as a means for revealing new molecular targets for the detection, diagnosis, and clinical management of idiopathic FGR.

Pre-eclampsia: fitting together the placental, immune and cardiovascular pieces

The success of pregnancy is a result of countless ongoing interactions between the placenta and the maternal immune and cardiovascular systems. Pre-eclampsia is a serious pregnancy complication that arises from multiple potential aberrations in these systems. The pathophysiology of pre-eclampsia is established in the first trimester of pregnancy, when a range of deficiencies in placentation affect the key process of spiral artery remodelling. As pregnancy progresses to the third trimester, inadequate spiral artery remodelling along with multiple haemodynamic, placental and maternal factors converge to activate the maternal immune and cardiovascular systems, events which may in part result from increased shedding of placental debris. As we understand more about the pathophysiology of pre-eclampsia, it is becoming clear that the development of early- and late-onset pre-eclampsia, as well as intrauterine growth restriction (IUGR), does not necessarily arise from the same underlying pathology.

Placental syncytiotrophoblast constitutes a major barrier to vertical transmission of Listeria monocytogenes

Listeria monocytogenes is an important cause of maternal-fetal infections and serves as a model organism to study these important but poorly understood events. L. monocytogenes can infect non-phagocytic cells by two means: direct invasion and cell-to-cell spread. The relative contribution of each method to placental infection is controversial, as is the anatomical site of invasion. Here, we report for the first time the use of first trimester placental organ cultures to quantitatively analyze L. monocytogenes infection of the human placenta. Contrary to previous reports, we found that the syncytiotrophoblast, which constitutes most of the placental surface and is bathed in maternal blood, was highly resistant to L. monocytogenes infection by either internalin-mediated invasion or cell-to-cell spread. Instead, extravillous cytotrophoblasts-which anchor the placenta in the decidua (uterine lining) and abundantly express E-cadherin-served as the primary portal of entry for L. monocytogenes from both extracellular and intracellular compartments. Subsequent bacterial dissemination to the villous stroma, where fetal capillaries are found, was hampered by further cellular and histological barriers. Our study suggests the placenta has evolved multiple mechanisms to resist pathogen infection, especially from maternal blood. These findings provide a novel explanation why almost all placental pathogens have intracellular life cycles: they may need maternal cells to reach the decidua and infect the placenta.

Is there a relationship between PCNA expression and diabetic placental development during pregnancy?

We aimed to investigate the distribution pattern of proliferating cell nuclear antigen (PCNA) by immunohistochemistry and Western blot in placentas of control and diabetic rats at different stages of pregnancy. It is still not clear how proliferation is coordinated and how this coordination is affected by diabetes in the placenta. Diabetes was induced by streptozocin on the first day of pregnancy. Animals were sacrificed on days 11, 13, 17 and 21 of pregnancy. In control placentas immunolabeling intensity of PCNA was the highest on days 11 and 13 of pregnancy and decreased with progression of pregnancy. In the diabetic groups immunolabeling was less intense on days 11 and 13 of pregnancy compared to controls. However, in parallel with placental weights, PCNA immunopositivity was more intense in diabetic groups than control groups on days 17 and 21 of pregnancy, and the difference was statistically significant on day 17. According to Western blot data, on days 11 and 13 of pregnancy the amount of PCNA was greater in control groups than in the diabetics, whereas it was greater in diabetic groups than the controls on days 17 and 21 of pregnancy. We conclude that PCNA may play a role in abnormal placenta formation resulting from diabetes.

Homeodomain protein HLX is expressed primarily in cytotrophoblast cell types in the early pregnancy human placenta

Homeobox genes are a large family of transcription factors. Of these, the HLX homeobox gene (previously known as HLX1 and HB24) is important for normal placentation. We have previously shown that HLX mRNA expression is significantly reduced in fetal growth-restricted human placentae compared with control placentae. In this study, a rabbit polyclonal antibody to the homeodomain protein HLX was raised and characterised. Western analysis revealed a protein of 50 kDa. HLX protein was detected in cellular nuclei in the cytotrophoblast-derived cell lines HTR8/SVneo, SGHPL-4, JEG-3, JAR and BeWo. Dual labelling with cytokeratin 7 was used to determine the spatial distribution of HLX in the early placenta and fetal membranes, showing both a perinuclear and punctate nuclear distribution for HLX. In the early pregnancy placenta HLX was localised to villous cytotrophoblast, and extravillous cytotrophoblast nuclei in the proximal regions of the cytotrophoblast cell columns, but was not detected at significant levels in the syncytiotrophoblast. In first trimester placental bed biopsies, HLX expression was not localised to the nucleus but instead was found in the cytoplasm. We conclude that HLX is primarily expressed in cytotrophoblast cell types in the human placenta and propose that HLX is involved in cytotrophoblast proliferation and downregulation of cell differentiation.