Trophoblast apoptosis in human placenta at term as detected by expression of a cytokeratin 18 degradation product of caspase

A pancreatic adenocarcinoma mimicking hepatoid carcinoma of uncertain histogenesis: A case report and literature review

In rare cases, metastatic adenocarcinomas of different origin may exhibit the features of hepatoid carcinoma (HC), a rare malignant epithelial tumor, most commonly occurring in the ovaries and stomach, as well as in the pancreas and biliary ducts. A case of a 72-year-old female patient who developed a highly aggressive, poorly differentiated pancreatic ductal adenocarcinoma with peritoneal carcinomatosis, demonstrating hepatoid differentiation upon conventional hematoxylin and eosin staining is reported in the present study. The patient presented with severe abdominal pain, and the radiological investigations performed revealed ovarian and hepatic tumor masses and peritoneal lesions, which were surgically removed. The gross examination of the peritoneum and omentum revealed multiple solid, firm, grey-white nodules, diffusely infiltrating the adipose tissue. The microscopic examination revealed a malignant epithelial proliferation, composed of polygonal cells with abundant eosinophilic cytoplasm and irregular, pleomorphic nuclei. Certain cells presented with intracytoplasmic mucus inclusions, raising suspicion of a HC with an uncertain histogenesis. Immunohistochemical staining was performed, and the tumor cells were found to be positive for cytokeratin (CK)7, CK18 and mucin 5AC, whereas negative staining for CK20, caudal-type homeobox transcription factor 2, α-fetoprotein, paired box gene 8, GATA-binding protein 3 and Wilms tumor 1 were documented. Thus, the diagnosis of metastatic pancreatic adenocarcinoma was established. The main aim of the present study was to provide further knowledge concerning poorly differentiated metastatic adenocarcinoma resembling HC, emphasizing the histopathological and immunohistochemical features of these malignant lesions and raising awareness of the diagnostic difficulties that may arise, as well as the importance of the use immunohistochemistry in differentiating carcinomas of uncertain histogenesis.

Syncytiotrophoblast stress in preeclampsia: the convergence point for multiple pathways

Preeclampsia evolves in 2 stages: a placental problem that generates signals to the mother to cause a range of responses that comprise the second stage (preeclampsia syndrome). The first stage of early-onset preeclampsia is poor placentation, which we here call malplacentation. The spiral arteries are incompletely remodeled, leading to later placental malperfusion, relatively early in the second half of pregnancy. The long duration of the first stage (several months) is unsurprisingly associated with fetal growth restriction. The first stage of late-onset preeclampsia, approximately 80% of total cases, is shorter (several weeks) and part of a process that is common to all pregnancies. Placental function declines as it outgrows uterine capacity, with increasing chorionic villous packing, compression of the intervillous space, and fetal hypoxia, and causes late-onset clinical presentations such as "unexplained" stillbirths, late-onset fetal growth restriction, or preeclampsia. The second stages of early- and late-onset preeclampsia share syncytiotrophoblast stress as the most relevant feature that causes the maternal syndrome. Syncytiotrophoblast stress signals in the maternal circulation are probably the most specific biomarkers for preeclampsia. In addition, soluble fms-like tyrosine kinase-1 (mainly produced by syncytiotrophoblast) is the best-known biomarker and is routinely used in clinical practice in many locations. How the stress signals change over time in normal pregnancies indicates that syncytiotrophoblast stress begins on average at 30 to 32 weeks' gestation and progresses to term. At term, syncytiotrophoblast shows increasing markers of stress, including apoptosis, pyroptosis, autophagy, syncytial knots, and necrosis. We label this phenotype the "twilight placenta" and argue that it accounts for the clinical problems of postmature pregnancies. Senescence as a stress response differs in multinuclear syncytiotrophoblast from that of mononuclear cells. Syncytiotrophoblast irreversibly acquires part of the senescence phenotype (cell cycle arrest) when it is formed by cell fusion. The 2 pathways converge on the common pathologic endpoint, syncytiotrophoblast stress, and contribute to preeclampsia subtypes. We highlight that the well-known heterogeneity of the preeclampsia syndrome arises from different pathways to this common endpoint, influenced by maternal genetics, epigenetics, lifestyle, and environmental factors with different fetal and maternal responses to the ensuing insults. This complexity mandates a reassessment of our approach to predicting and preventing preeclampsia, and we summarize research priorities to maximize what we can learn about these important issues.

Cell dynamics in human villous trophoblast

BACKGROUND

Villous cytotrophoblast (vCTB) is a precursor cell population that supports the development of syncytiotrophoblast (vSTB), the high surface area barrier epithelium of the placental villus, and the primary interface between maternal and fetal tissue. In light of increasing evidence that the placenta can adapt to changing maternal environments or, under stress, can trigger maternal disease, we consider what properties of these cells empower them to exert a controlling influence on pregnancy progression and outcome.

OBJECTIVE AND RATIONALE

How are cytotrophoblast proliferation and differentiation regulated in the human placental villus to allow for the increasing demands of the fetal and environmental challenges and stresses that may arise during pregnancy?

SEARCH METHODS

PubMed was interrogated using relevant keywords and word roots combining trophoblast, villus/villous, syncytio/syncytium, placenta, stem, transcription factor (and the individual genes), signalling, apoptosis, autophagy (and the respective genes) from 1960 to the present. Since removal of trophoblast from its tissue environment is known to fundamentally change cell growth and differentiation kinetics, research that relied exclusively on cell culture has not been the main focus of this review, though it is mentioned where appropriate. Work on non-human placenta is not systematically covered, though mention is made where relevant hypotheses have emerged.

OUTCOMES

The synthesis of data from the literature has led to a new hypothesis for vCTB dynamics. We propose that a reversible transition can occur from a reserve population in G0 to a mitotically active state. Cells from the in-cycle population can then differentiate irreversibly to intermediate cells that leave the cycle and turn on genes that confer the capacity to fuse with the overlying vSTB as well as other functions associated with syncytial barrier and transport function. We speculate that alterations in the rate of entry to the cell cycle, or return of cells in the mitotic fraction to G0, can occur in response to environmental challenge. We also review evidence on the life cycle of trophoblast from the time that fusion occurs, and point to gaps in knowledge of how large quantities of fetal DNA arrive in maternal circulation. We critique historical methodology and make a case for research to re-address questions about trophoblast lifecycle and dynamics in normal pregnancy and the common diseases of pre-eclampsia and fetal growth restriction, where altered trophoblast kinetics have long been postulated.

WIDER IMPLICATIONS

The hypothesis requires experimental testing, moving research away from currently accepted methodology towards a new standard that includes representative cell and tissue sampling, assessment of cell cycle and differentiation parameters, and robust classification of cell subpopulations in villous trophoblast, with due attention to gestational age, maternal and fetal phenotype, disease and outcome.

The effect of Ipomoea carnea on maternal reproductive outcomes and fetal and postnatal development in rats

Ipomoea carnea is a toxic plant found in Brazil and other tropical countries. The plant contains the alkaloids calystegines and swainsonine, which inhibit key cellular enzymes and cause systematic cell death. It is known that swainsonine is excreted in the amniotic fluid of dams exposed to the plant. Thus, the aim of this study was to verify whether the toxic effect of I. carnea on fetuses is due to exclusively the passage of the active principle of the plant through the placenta, or if the placentotoxic effect of swainsonine could collaborate in the adverse effects observed in the fetus. The teratogenic effects of exposure to the toxic principles of I. carnea were evaluated not only using the conventional protocol but also at later stages in the postnatal developmental period. Females were treated, from gestation day (GD) 6 until GD19, with 0.0, 1.0, 3.0 or 7.0 g/kg body weight of I. carnea dry leaves. The plant did not induce changes in reproductive performance or biochemical profile of the dams. Dams that received the highest dose of I. carnea showed cytoplasmic vacuolization in the liver, kidney and placental tissue. I. carnea promoted different lectin binding patterns in different areas of placental tissue. No fetal skeletal or visceral malformations was observed. The postnatal evaluation revealed a lower litter weight and a lower pup body weight one day after birth in the group that received the highest dose of I. carnea. Physical milestones were unaffected by the treatments. Female pups from all experimental groups exhibited a delay in achieving a negative geotaxis response. The results show that the toxic principle of I. carnea produces injury in utero in mothers and fetuses, but these deleterious effects were better demonstrated using postnatal evaluation.

QSOX1 regulates trophoblastic apoptosis in preeclampsia through hydrogen peroxide production

Objective: Oxidative stress plays a significant role in the pathogenesis of preeclampsia (PE), by inducing trophoblast cell death and consequent placental dysfunction. Quiescin sulfhydryl oxidase 1 (QSOX1) is upregulated in many types of cancer cells; it promotes disulfide bond formation as well as hydrogen peroxide (H₂O₂) production. The aims of present study are to investigate the expression pattern of QSOX1 in placentae of pregnancies complicated by PE and the role of QSOX1 in the regulation of trophoblastic function, thus providing in-depth understanding of the putative involvement of QSOX1 in the development of PE. Methods: Human term placenta from normal pregnancies and from pregnancies complicated by PE was collected to measure QSOX1 expression and H₂O₂ levels. Down-regulation of QSOX1 in HTR-8/SVneo cells was achieved by siRNA interference. An in vitro cellular PE model was generated by hypoxic incubation. Protein expression levels were assessed by Western blotting, and H₂O₂ levels were determined in the cell culture medium as well as in the cell lysate. Trophoblast apoptosis was evaluated by TUNEL staining. Results: QSOX1 was overexpressed in the PE placenta. Inhibition of QSOX1 expression in HTR-8/SVneo cells attenuated cell apoptosis and intracellular H₂O₂ levels. Hypoxia-induced QSOX1 expression in HTR-8/SVneo cells and led to apoptosis of HTR-8/SVneo cells, and knock-down of QSOX1 rescued hypoxia-induced trophoblast apoptosis. Conclusions: Hypoxia-induced upregulation of QSOX1 and a consequent elevation in intracellular H₂O₂ increased apoptosis in placentae of pregnancies complicated by PE.

Establishment and characterization of cell lines derived from complete hydatidiform mole

Gestational trophoblastic diseases (GTDs) are a group of diseases characterized by abnormal cellular proliferation of atypical trophoblasts. A hydatidiform mole is an abnormal pregnancy caused by genetic fertilization disorders, and it can be classified as a complete hydatidiform mole (CHM) or a partial hydatidiform mole. The aim of this study was to establish cell lines from CHMs and to characterize the cells for future studies concerning GTD. HMol1-2C, HMol1-3B, HMol1-8 and HMol3-1B were established from primary cultures of CHM explants following the introduction of different combinations of genes including human telomerase reverse transcriptase (hTERT), a mutant form of CDK (CDK4R24C), cyclin D1, p53C234, MYC and HRAS. HMol1-2C, HMol1-3B, and HMol3-1B were confirmed to originate from trophoblasts of androgenic, homozygous CHMs. These three cell lines exhibited low human chorionic gonadotropin secretion, low migration and invasion abilities, and the potential to differentiate into syncytiotrophoblastic cells via forskolin treatment. These results suggest that these cells exhibit characteristics of trophoblastic cells, especially cytotrophoblastic cells. HMol1-8 was found to consist of diploid cells and originated from maternal cells, suggesting that they were derived from decidual cells. In conclusion, we successfully established three cell lines from CHMs by introduction of hTERT and other genes. Analysis revealed that the genetic origin of each cell line was identical with that of the original molar tissue, and the cell lines exhibited characteristics of trophoblastic cells, which are similar to undifferentiated cytotrophoblasts.

Modulation of wolframin expression in human placenta during pregnancy: comparison among physiological and pathological states

The WFS1 gene, encoding a transmembrane glycoprotein of the endoplasmic reticulum called wolframin, is mutated in Wolfram syndrome, an autosomal recessive disorder defined by the association of diabetes mellitus, optic atrophy, and further organ abnormalities. Disruption of the WFS1 gene in mice causes progressive β-cell loss in the pancreas and impaired stimulus-secretion coupling in insulin secretion. However, little is known about the physiological functions of this protein. We investigated the immunohistochemical expression of wolframin in human placenta throughout pregnancy in normal women and diabetic pregnant women. In normal placenta, there was a modulation of wolframin throughout pregnancy with a strong level of expression during the first trimester and a moderate level in the third trimester of gestation. In diabetic women, wolframin expression was strongly reduced in the third trimester of gestation. The pattern of expression of wolframin in normal placenta suggests that this protein may be required to sustain normal rates of cytotrophoblast cell proliferation during the first trimester of gestation. The decrease in wolframin expression in diabetic placenta suggests that this protein may participate in maintaining the physiologic glucose homeostasis in this organ.

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.

In vitro simulation of placental transport: part I. Biological model of the placental barrier

INTRODUCTION

The placental barrier (PB) is the thin biological membrane made of endothelial cells (EC), trophoblast cells (TC) and basal membrane that separates between maternal and fetal blood circulations within the placenta and facilitates feto-maternal transport characteristics, which are not completely understood.

METHODS

An in vitro biological model of the PB model was co-cultured of human TC (HTR8) and human umbilical vein EC (HUVEC) on both sides of a denuded amniotic membrane (AM) using custom designed wells.

RESULTS

Confocal and transmission electron microscopy (TEM) imaging confirmed the morphology expressions of human EC and TC. Further support on the integrity of the new PB model was obtained from the existence of tight junctions and permeability experiments with fluorescence markers of small and large molecules. The monolayer of EC demonstrated the limiting layer for the transport resistance across this complex barrier.

DISCUSSION AND CONCLUSION

This new in vitro viable model mimics the architecture of the human PB and can be used in in vitro simulations of transplacental transport studies.

Apoptosis and Bcl-2 protein expression in human placenta over the course of normal pregnancy

Apoptosis plays a central role in organ development, homeostasis and immune defence in multicellular organisms and is strictly controlled in part by members of Bcl-2 family. The Bcl-2 is a pro-survival molecule identified through its involvement in B-cell lymphomas. The aim of the study was to evaluate the incidence of apoptosis in the human placenta at different stages of pregnancy and to correlate it further with Bcl-2 expression. A total of 96 placental samples from first trimester, mid-trimester and uncomplicated term pregnancies were collected (n = 32 + 32 + 32). M30 cyto death monoclonal antibody was used to identify apoptotic cells. The apoptosis index of first trimester placentae was 2.33 ± 1.70, mid- trimester was 1.77 ± 1.36 and term placenta was 1.15 ± 0.21. Bcl-2 protein was found immunolocalized in the cytoplasm of syncytiotrophoblast. Apoptosis index was significantly reduced in term cases as compared with first trimester (P < 0.002) and mid-trimester placentae (P = 0.01). On the contrary, Bcl-2 expression was significantly higher at term cases than in first trimester (P < 0.0001) and mid-trimester cases (P < 0.001). The present study divulges the importance of apoptosis in permitting normal physiological turnover of villous trophoblast and also exhibits the contribution of bcl-2 in maintaining syncytial integrity throughout normal pregnancy.

Villous trophoblast apoptosis is elevated and restricted to cytotrophoblasts in pregnancies complicated by preeclampsia, IUGR, or preeclampsia with IUGR

Human placental villi are surfaced by an outer multinucleated syncytiotrophoblast and underlying mononucleated cytotrophoblasts. Conflicting data have attributed one, or the other, of these villous trophoblast phenotypes to undergo enhanced apoptosis in complicated pregnancies, compared to term, normotensive pregnancies. We use high-resolution confocal microscopy after co-staining for E-cadherin, as a trophoblast plasma membrane marker, and for the cleavage products of cytokeratin 18 and PARP1, as markers for caspase-mediated apoptosis, to distinguish between apoptotic cytotrophoblasts and apoptosis within the syncytiotrophoblast. We test the hypothesis that increased caspase-mediated apoptosis occurs in villi of placentas derived from pregnancies complicated by preeclampsia, intrauterine growth restriction (IUGR), or both. We find significantly elevated apoptosis in villous cytotrophoblasts from women with preeclampsia and/or IUGR, compared to term, normotensive pregnancies. Apoptosis of cytotrophoblasts in villi from complicated pregnancies appears to progress similarly to what we found previously for apoptotic cytotrophoblasts in villi from in term, normotensive pregnancies. Notably, caspase-mediated apoptosis was not detectable in regions with intact syncytiotrophoblast, suggesting strong repression of apoptosis in this trophoblast phenotype in vivo. We suggest that the elevated apoptosis in cytotrophoblasts in preeclampsia contributes to the placental dysfunction characteristic of this disorder. We also propose that repression of apoptosis in the syncytiotrophoblast is important to prevent apoptosis sweeping throughout the syncytium, which would result in widespread death of this essential interface for maternal-fetal exchange.

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.

Evaluation of the contribution of the placentomal fusion during gestation in cattle

The placenta of mammals is a structure formed by the juxtaposition of the fetal membranes and the maternal tissues. The main function of the placenta is to regulate the physiological interchange between the fetus and the mother as well as to operate as an important endocrine organ during the gestation. The placentomal fusions were characterized throughout gestation of cattle using macroscopic, histological and flow cytometry analyses. Analyzing the cell cycle phases with a flow cytometry, a balance between the G2M phase and apoptosis was observed, suggesting that the placentomal fusions do not interfere in the placentary maturation process, which is a pre-requirement for the fetal-maternal disconnection and the release of fetal membrane.

Dual roles of intermediate filaments in apoptosis

New roles have emerged recently for intermediate filaments (IFs), namely in modulating cell adhesion and growth, and providing resistance to various forms of stress and to apoptosis. In this context, we first summarize findings on the IF association with the cell response to mechanical stress and growth stimulation, in light of growth-related signaling events that are relevant to death-receptor engagement. We then address the molecular mechanisms by which IFs can provide cell resistance to apoptosis initiated by death-receptor stimulation and to necrosis triggered by excessive oxidative stress. In the same way, we examine IF involvement, along with cytolinker participation, in sequential caspase-mediated protein cleavages that are part of the overall cell death execution, particularly those that generate new functional IF protein fragments and uncover neoantigen markers. Finally, we report on the usefulness of these markers as diagnostic tools for disease-related aspects of apoptosis in humans. Clearly, the data accumulated in recent years provide new and significant insights into the multiple functions of IFs, particularly their dual roles in cell response to apoptotic insults.

Formation of Syncytial Knots is Increased by Hyperoxia, Hypoxia and Reactive Oxygen Species

The syncytiotrophoblast contains aggregates of nuclei termed syncytial knots. Increased numbers of syncytial knots have been reported in placentae of pregnancies complicated by pre-eclampsia and fetal growth restriction (FGR). As oxidative stress has been implicated in the pathophysiology of these disorders, we hypothesised that the formation of syncytial knots may be induced by exposure to hypoxia, hyperoxia or reactive oxygen species (ROS). We assessed both the number and morphology of syncytial knots induced by culture in hypoxia, hyperoxia and with ROS. We also investigated whether the presence of syncytial knots in normal tissue was associated with a down-regulation of anti-apoptotic proteins Bcl-2, Mdm2, XIAP and survivin. Using our measurement system we describe an increased number of syncytial knots when tissue is cultured in hypoxia, hyperoxia or in the presence of ROS. The morphology of these syncytial knots was similar to those seen in vitro, although the nuclei from cultured placental explants were morphologically more homogenous, had fewer nuclear pores, and a higher heterochromatin:euchromatin ratio. Despite the apoptotic appearances of nuclei we did not detect a loss of anti-apoptotic proteins in the region of syncytial knots. We conclude that the increased number of syncytial knots in placentae from pregnancies complicated by pre-eclampsia and FGR can be replicated in vitro by ROS or hypoxia, supporting their involvement in the pathogenesis of these conditions.

The effect of docosahexaenoic acid and folic acid supplementation on placental apoptosis and proliferation

The hypothesis was tested that the additional dietary uptake of n-3 fatty acids, in particular of DHA and 5-methyltetrahydrofolate (5-MTHF), during the second half of pregnancy would influence proliferation and apoptosis in the full-term human placenta. The diets of pregnant women from Spain (n 55) were supplemented with modified fish oil and/or 5-MTHF or placebo, and assigned in a random, double-blind manner to one of the four groups. Immunohistochemistry and immunoblotting were used to detect placental proliferation and apoptosis with monoclonal antibodies for key proteins that reflected the extent of both processes: proliferation cell nuclear antigen (PCNA), p53, cytokeratin 18 neoepitope. The PCNA level in the fish oil/5-MTHF-treated group was higher by 66 % (P < 0.05) than that of the placebo group, whereas the levels of p53 and cytokeratin 18 neoepitope were unaffected by treatment. PCNA expression was altered only in the trophoblast compartment (placebo 11.1 (se 0.5) % v. combination 21.5 (se 1.2) %; P < 0.05), whereas the proportion of nuclei stained in endothelial and other stromal cells was similar in the placebo and combined treatment groups. No correlation was found between fish oil or 5-MTHF supplementation and the levels of the proteins. The present data suggest that supplementation with fish oil and/or 5-MTHF had no effect on the parameters reflecting placental proliferation and apoptosis. A defined combination of DHA and 5-MTHF may, however, affect placental proliferation.

Chronic hypoxia in vivo reduces placental oxidative stress

Decreased placental oxygenation and increased oxidative stress are implicated in the development of preeclampsia. Oxidative stress arises from imbalance between pro-versus anti-oxidants and can lead to biological oxidation and apoptosis. Because pregnant women living at high altitude (3100 m, HA) have lowered arterial PO2 and an increased incidence of preeclampsia, we hypothesized that HA placentas would have decreased anti-oxidant enzyme activity, increased oxidative stress (lipid peroxidation, protein oxidation and nitration) and greater trophoblast apoptosis than low-altitude (LA) placentas. We measured enzymatic activities, lipid and protein oxidation and co-factor concentrations by spectrophotometric techniques and ELISA in 12 LA and 18 HA placentas. Immunohistochemistry (IHC) was used to evaluate nitrated proteins and specific markers of apoptosis (activated caspase 3 and M30). Superoxide dismutase activity was marginally lower (p=0.05), while glutathione peroxidase activity (p<0.05), thioredoxin concentrations (p<0.005) and thioredoxin reductase activity p<0.01 were all reduced in HA placentas. Decreased anti-oxidant activity was not associated with increased oxidative stress: lipid peroxide content and protein carbonyl formation were lower at HA (p<0.01). We found greater nitrotyrosine residues in the syncytiotrophoblast at 3100 m (p<0.05), but apoptosis did not differ between altitudes. Our data suggest that hypoxia does not increase placental oxidative stress in vivo. Nitrative stress may be a consequence of hypoxia but does not appear to contribute to increased apoptosis. Lowered placental concentrations of anti-oxidants may contribute to the susceptibility of women living at HA to the development of preeclampsia, but are unlikely to be etiological.

Prenatal Vitamin C Status is Associated with Placental Apoptosis in Normal-term Human Pregnancies

Pregnancy is associated with increased susceptibility to oxidative stress. Deficiencies in antioxidants during pregnancy and placental oxidant-antioxidant imbalance may impair the development of the fetoplacental unit or the eventual offspring. In order to elucidate the association of prenatal status of vitamin C with the oxidative stress and apoptotic activity in normal full-term placentas, we evaluated the content of placental lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) and the trophoblast apoptotic index in normal-term human pregnancies. Tissue samples of placentas obtained from 80 normal-term pregnancies were categorized into 40 cases with a lower level of prenatal vitamin C (< 8.997 microg/ml) and 40 cases with a higher level of prenatal vitamin C (> or =11.734 microg/ml). We evaluated the placental LOX-1 content and the trophoblast apoptotic index with Western blot analysis and immunohistochemistry, and then determined their correlation with the prenatal status of vitamin C. We confirmed that the trophoblast expression for the endothelial scavenger receptor LOX-1 and the apoptotic activity were significantly lower in the group with a higher prenatal level of vitamin C, indicating that placental oxidative stress and the apoptotic index were associated with the maternal status of vitamin C. We therefore postulate that the maternal status of antioxidant vitamins during pregnancy can affect fetal development.

Apoptosis may underlie the pathology of zinc-deficient skin

The trace element zinc is essential for the survival and function of all cells. Zinc deficiency, whether nutritional or genetic, is fatal if left untreated. The effects of zinc deficiency are particularly obvious in the skin, seen as an erythematous rash, scaly plaques, and ulcers. Electron microscopy reveals degenerative changes within keratinocytes. Despite the well-documented association between zinc deficiency and skin pathology, it is not clear which cellular processes are most sensitive to zinc deficiency and could account for the typical pathological features. We used the cultured HaCaT keratinocyte line to obtain insight into the cellular effects of zinc deficiency, as these cells show many characteristics of normal skin keratinocytes. Zinc deficiency was induced by growing cells in the presence of the zinc chelator, TPEN, or by growth in zinc-deficient medium. Growth of cells in zinc-deficient medium resulted in a 44% reduction of intracellular zinc levels and a 75% reduction in the activity of the zinc-dependent enzyme, 5'-nucleotidase, relative to the control cells. Over a period of 7 days of exposure to zinc-deficient conditions, no changes in cell viability and growth, or in the cytoskeletal and cell adhesion systems, were found in HaCaT cells. At 7 days, however, induction of apoptosis was indicated by the presence of DNA fragmentation and expression of active caspase-3 in cells. These results demonstrate that apoptosis is the earliest detectable cellular change induced by zinc deficiency in HaCaT keratinocytes. Our observations account for many of the features of zinc deficiency, including the presence of degenerate nuclei, chromatin aggregates and abnormal organization of keratin, that may represent the later stages of apoptosis. In summary, a major causal role for apoptosis in the pathology of zinc deficiency in the skin is proposed. This role is consistent with the previously unexplained diverse range of degenerative cellular changes seen at the ultrastructural level in zinc-deficient keratinocytes.

Dissociation between increased apoptosis and expression of the tumor necrosis factor-alpha system in term placental villi with preeclampsia

OBJECTIVE

To analyse in situ the placental expression of tumor necrosis factor-alpha (TNF-alpha), its receptors TNFRp55 and TNFRp75, and apoptosis in normotensive and preeclamptic pregnancies.

DESIGN AND METHODS

We simultaneously analyzed the immunostaining of TNF-alpha, its receptors and apoptosis in term placentas of 15 patients with preeclampsia and 15 normotensive pregnant women as controls.

RESULTS

In normotensive villi TNF-alpha and TNFRp75 were expressed more in syncytiotrophoblasts than cytotrophoblasts or stromal cells, and were almost absent in endothelial cells. TNFRp55 was expressed uniformly in all types of placental cells. Apoptosis was more marked in syncytiotrophoblasts than cytotrophoblasts. In preeclamptic trophoblasts apoptosis was exaggerated whereas expression of TNF-alpha and its receptors remained unchanged.

CONCLUSIONS

Placental expression of TNF-alpha and TNFRp75 appear inter-adaptative and follow the same pattern, whereas TNFRp55 and TNF-alpha appear independent. In addition, the exaggerated apoptosis of preeclamptic trophoblasts may be dependent on factors other than the TNF-alpha system alone.

The role of apoptosis in the regulation of trophoblast survival and differentiation during pregnancy

Apoptosis is important for normal placental development, but it may also be involved in the pathophysiology of pregnancy-related diseases. Normal placental development is dependent upon the differentiation and invasion of the trophoblast, the main cellular component of the placenta. Trophoblast apoptosis increases in normal placentas as gestation proceeds, and a greater incidence of trophoblast apoptosis has been observed in pregnancies complicated by preeclampsia or intrauterine growth retardation (IUGR). In response to different stimuli, apoptosis may be initiated extrinsically by the death receptor pathway or intrinsically by the mitochondrial pathway. The central executioners of apoptosis are the caspases, which cleave numerous vital cellular proteins to affect the apoptotic cascade. By inhibiting caspase activation, several endogenous inhibitors, including flice-like inhibitory proteins (FLIPs), inhibitors of apoptosis (IAPs), and antiapoptotic Bcl-2 family members, can prevent further propagation of the death signal. Macrophages present at the maternal-fetal interface may also contribute to trophoblast survival by removing apoptotic cells and producing cytokines and growth factors, which influence the progression of the apoptotic cascade. This review focuses on the role of apoptosis in trophoblast development and differentiation, the molecular mechanisms by which normal trophoblast apoptosis can occur, and how it is regulated to prevent excessive trophoblast apoptosis and possible pregnancy complications.

Caspase-14 expression in the human placenta

Caspase-14 is involved in epidermal differentiation, and previous studies demonstrated abundant expression in the skin. However, the expression of caspase-14 in the human placenta has not been reported. The aims of this study were to determine whether caspase-14 is expressed in the first trimester and term human placenta, and if it is associated with apoptosis in the placenta. Caspase-14 is expressed in the trophoblast cells, and in lower amounts in the mesenchyme. Western blot analysis demonstrated increased expression in the first trimester compared with term placentae. Immunohistochemistry for caspase-14 showed diffuse expression in the trophoblast layer, and not only in occasional cells that are identified by TUNEL staining. Using an explant model in which apoptosis was inhibited with superoxide dismutase (SOD), no significant differences in caspase-14 protein concentrations were seen with differing levels of apoptosis. Caspase-14 is present in the human placenta, primarily in the trophoblast, but its function is not clear, and appears not to be related purely to apoptosis.

Differential effects of inducers of syncytialization and apoptosis on BeWo and JEG-3 choriocarcinoma cells

BACKGROUND

The interactions of trophoblasts with the cytokine network at the fetomaternal interface determine the pathway the cell undertakes, e.g. proliferation, differentiation and apoptosis.

METHODS

We used cultures of fusigenic BeWo and non-fusigenic JEG-3 choriocarcinoma cells to study the effects of inducers of syncytialisation (forskolin) and apoptosis [tumour necrosis factor-alpha (TNFalpha)] on differentiation, viability, proliferation and apoptosis.

RESULTS

E-cadherin immunostaining showed that syncytium formation was confined to BeWo and not JEG-3 cells, while secretion of hCG was promoted by forskolin in both cell types implying a 'dissociation' between morphological and biochemical differentiation. Forskolin also had differential effects on cell viability (MTT reduction test) and proliferation (Ki67 immunostaining with MIB-1 monoclonal antibody), both decreasing in BeWo and increasing in JEG-3 cells. TNFalpha increased apoptosis (cytokeratin neo-epitope immunostaining with M30 monoclonal antibody) in both cell types, an effect which was blocked by epidermal growth factor selectively in JEG-3 cells.

CONCLUSION

Our results suggest that the differential responses of BeWo and JEG-3 cells to inducers of syncytialization and apoptosis might be related to their fusigenic capacity. Caution is needed when extrapolating results obtained by these models to normal trophoblast populations. However, we speculate that these models can help identify key factors involved in trophoblast differentiation at the placental bed.

Programmed cell death (apoptosis) in placentas from normal pregnancy and pregnancy complicated by term (t) and preterm (p) premature rupture of membranes (PROM)

OBJECTIVE

The aim of this study was to determine the apoptotic index using three different apoptotic markers: terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL); M30 cytoDEATH antibody and fluorescein isothiocyanate (FTIC)-labeled annexin-V in the placenta and membranes from normal pregnancy and pregnancy complicated by premature rupture of membranes (PROM).

STUDY DESIGN

Placentas from 16 pregnancies (22-40 weeks' gestation) and 13 pregnancies complicated by pPROM and tPROM were collected at delivery. Maternal and gestational age, mode of delivery, gravidity and parity, fetal birthweight, Apgar scores, presence of histologic chorioamnionitis, interval between membrane rupture and delivery were recorded among PPROM and tPROM cases.

RESULTS

Only M30 cytoDEATH antibody (P=0.02) and TUNEL test (P=0.04) on fetal membranes gave statistically significantly higher levels in cases with premature rupture of membranes. The presence of histologic chorioamnionitis had no significant impact on apoptotic markers in PROM placentas. Preterm deliveries following the rupture of membranes had higher median AI values detected by M30M antibody, compared to those cases delivered without PROM (P=0.03).

CONCLUSION

High apoptotic nuclei counts were found in fetal membranes of pPROM.

Fibrin Enhances Differentiation, but not Apoptosis, and Limits Hypoxic Injury of Cultured Term Human Trophoblasts

We hypothesized that fibrin enhances apoptosis and modulates differentiation of trophoblast in vitro. Cytotrophoblasts isolated from normal term human placentas were cultured < or =72 h in DMEM-10%-FBS on a fibrin matrix in standard or hypoxic conditions. Trophoblasts were cultured on plastic (control), type I collagen (matrix control), or dishes with fibrinogen, fibrin degradation products (FDP), thrombin, plasma fibronectin or cellular fibronectin. Apoptosis was determined by western analysis of the cleavage products of poly-ADP-ribose polymerase and cytokeratin 18 and caspase 3 activity. Cell cycle regulation was quantified by expression of proliferating cell nuclear antigen (PCNA) and p27 protein. Differentiation was determined by media level of hCG and hPL. Compared to the two controls, fibrin matrix had no effect on trophoblast apoptosis or total cell death in standard conditions. Neither fibrin nor collagen altered expression of PCNA or p27. In contrast, fibrin significantly increased the secretion of both hCG and hPL. Fibrin, but not FDP, thrombin or fibronectins, promoted hormonal differentiation. Fibrin limited the impact of a < or =8h of hypoxia on trophoblast hormone release but did not avert the effects of 24h of low oxygen and did not alter apoptosis in hypoxic trophoblast. We conclude that fibrin provides an environment conducive for trophoblast re-epithelialization of the surface of villi, where injury is marked by fibrin deposition.

Inhibition of DLX4 promotes apoptosis in choriocarcinoma cell lines

Homeodomain (HDM) proteins encoded by homeobox (HBX) genes represent a large family of transcriptional factors that control differentiation and development in certain cell types. DLX4 is a member of Distal-less (DLX) family of HBX genes. Recent studies have demonstrated that abnormal expression of DLX4 is present in several types of human tumors, such as breast cancer, leukemia and colon cancer. In the present study, we investigated DLX4 mRNA and protein expression in both normal placental tissues and human choriocarcinoma cell lines. Also, using RNA interference (RNAi) technique, we knocked down the expression of DLX4 and examined apoptosis in JEG-3 cells. Our studies demonstrated that DLX4 RNAi inhibited DLX4 mRNA expression and decreased DLX4 protein mass specifically and effectively, potentially enhancing apoptosis. Moreover, we examined expression of caspase-3 and caspase-8, and found that both caspases were increased after DLX4 knockdown. However, DLX4 RNAi did not influence Bax expression in JEG-3 cells. In conclusion, this study suggests that DLX4 may be involved in the survival of human choriocarcinoma cells, which may be mediated by the inhibition of apoptosis. The detailed mechanism needs further investigation.

Maternal smoking, intrauterine growth restriction, and placental apoptosis

Pregnant women who smoke are at greater risk of delivering a growth-restricted infant than nonsmoking mothers. We wanted to see if apoptosis could be involved in the mechanisms behind smoke-induced growth restriction, and our aim was to compare apoptosis in the placenta of smoking mothers giving birth to growth-restricted infants and nonsmoking mothers with infants of appropriate weight. The project was conducted at the Magee--Womens Hospital and Magee--Womens Research Institute, University of Pittsburgh, PA. Histological sections from 20 placentas were selected from smoking mothers who had given birth to small-for-gestational-age infants (birth weight < or = 2 SD). The controls were gestational-age matched nonsmoking mothers with infants having appropriate-for-gestational-age weight. The TUNEL method was used to demonstrate DNA fragmentation in nuclei, and a monoclonal antibody M30, specific for a neo-epitope on cytokeratin 18, was used to identify apoptotic epithelial cells. The positive nuclei (TUNEL) and positive cells (M30-positive cytoplasm) were counted blindly both in villous tissue and in decidual/basal plate tissue. M30-positive cells in villous tissues were significantly increased in placentas from smoking mothers compared to nonsmoking mothers. When evaluated by the TUNEL method, the difference between the two groups of women was not significant. Our study shows that apoptosis was increased in the placentas of smoking mothers with growth-restricted infants. The difference between the two groups was mainly in the syncytiotrophoblast layer and in connection with perivillous fibrin deposition. Cigarette smoke with reduction in blood flow has previously been shown to increase apoptosis, and it is possible that this could be one of the mechanisms playing a role in the growth restriction.

Apoptosis of extravillous trophoblast cells limits the trophoblast invasion in uterine but not in tubal pregnancy during first trimester

During the first trimester of pregnancy extravillous trophoblast cells (EVT) invade the maternal decidua. Invasion normally is reduced from the second trimester onwards and stops in the inner third of the myometrium. By contrast, in extrauterine tubal pregnancy, trophoblast invasion may even penetrate the tubal wall, which ultimately leads to the rupture of the fallopian tube. Induction of apoptosis of EVT cells, by maternal immune competent cells, may be an important mechanism to limit EVT invasion in uterine pregnancy. Tissue specimens from first and second trimester uterine pregnancy and first trimester tubal pregnancy were analyzed for apoptosis by TUNEL- and M30-staining. By immunohistochemical double labelling, maternal leukocyte subtypes were co-localized to apoptotic cells and in this context, the number of CD56(+)NK cells was analyzed. Our data show that apoptosis is confined to the decidua basalis. Most apoptotic cells are single cytokeratin-positive epithelial cells residing in the stromal compartment. Consequently these cells can only be EVT cells. Maternal leukocytes are not apoptotic. They are located in close contact to apoptotic cells. The number of apoptotic cells in the second trimester (1.8+/-0.7 per cent) is reduced compared to first trimester (5.6+/-0.7 per cent) of uterine pregnancy. In parallel, the number of NK cells declines from first (24.4+/-2.9) to second (12.4+/-1.8) trimester. Furthermore, apoptosis is significantly reduced in ectopic (0.9+/-0.3 per cent) compared to eutopic first trimester pregnancies. Consequently, we suggest that in first trimester uterine pregnancy, induction of EVT cell apoptosis by the maternal immune system is one mechanism to limit EVT invasion. During the second trimester, in parallel to declining numbers of NK cells, the mechanism changes. However, in tubal pregnancy due to differing immunological microenvironments at the ectopic implantation site, apoptosis induction fails, which deleteriously may result in uncontrolled invasion and penetration of the tubal wall.

Pre-eclampsia: associated with increased syncytial apoptosis when the infant is small-for-gestational-age

The present investigation was undertaken to study the association between placental apoptosis and pre-eclampsia, discriminating between pre-eclamptic pregnancies with appropriate-, and small-for-gestational-age (SGA), infants. Twenty pregnancies with pre-eclampsia and SGA (birth weight at or below -2 standard deviations) infants were selected in a retrospective study. Subsequently, corresponding numbers of gestational age-matched pre-eclampsia cases with appropriate-gestational-age (AGA) (birth weight at or above the 50% centile) infants and AGA controls without pre-eclampsia were selected. Formalin-fixed placental tissue was obtained from all groups. Apoptosis was assessed by a monoclonal antibody (M30), detecting a neoepitope of cytokeratin that is generated early in the apoptotic cascade. M30-positive cells were counted in villous and decidual/ basal plate tissue fields, and results were given as numbers of M30-positive cells per field. The study was performed blinded. Increased apoptosis was found in the syncytiotrophoblast layer in pre-eclampsia with SGA infants (0.14 apototic incidents per field of villous tissue, with 0.04-0.23 as the corresponding 25-75% inter quartile range (IQR) (P=0.05)). Syncytial apoptosis in the syncytial layer in the pre-eclampsia group with AGA infants was lower (0.09, IQR 0.03-0.15) and corresponded to the level detected among controls (0.06, IQR 0.03-0.17). Apoptosis in other placental cellular compartments did not differ between groups. The increased syncytial apoptosis found in placentas from pregnancies with SGA infants may either be due to specific mechanisms associated with pre-eclampsia complicated with growth restriction, or may simply reflect the presence of syncytiotrophoblast layer damage, regardless of underlying pathological condition.

Homocysteine induces trophoblast cell death with apoptotic features

Hyperhomocysteinemia has been suggested as a possible risk factor in women suffering from habitual abortions, placental abruption or infarcts, preeclampsia, and/or intrauterine growth retardation. However, little is known about the pathogenic mechanisms underlying the action of homocysteine. The present study investigated the in vitro ability of homocysteine to affect trophoblast gonadotropin secretion and to induce cell death. In primary human trophoblast cells, homocysteine treatment (20 micromol/L) resulted in cellular flattening and enlargement, extension of pseudopodia, and cellular vacuolization. Cellular detachment, apoptosis, and necrosis were favored. With in situ nick end labeling, we investigated DNA degradation, and we used M30 CytoDEATH to selectively stain the cytoplasm of apoptotic cells. Cytochrome c release from mitochondria to the cytosol and DNA cleavage in agarose gel have been investigated. Homocysteine, but not cysteine, induced trophoblast apoptosis and significantly reduced human chorionic gonadotropin secretion. These findings suggest that trophoblast cell death might represent a pathogenic mechanism by which homocysteine may cause pregnancy complications related to placental diseases.