Inverse relationship between apoptosis and Bcl-2 expression in syncytiotrophoblast and fibrin-type fibrinoid in early gestation

In Vitro Model of Human Trophoblast in Early Placentation

The complex process of placental implantation and development affects trophoblast progenitors and uterine cells through the regulation of transcription factors, cytokines, adhesion receptors and their ligands. Differentiation of trophoblast precursors in the trophectoderm of early ontogenesis, caused by the transcription factors, such as CDX2, TEAD4, Eomes and GATA3, leads to the formation of cytotrophoblast and syncytiotrophoblast populations. The molecular mechanisms involved in placental formation inside the human body along with the specification and differentiation of trophoblast cell lines are, mostly due to the lack of suitable cell models, not sufficiently elucidated. This review is an evaluation of current technologies, which are used to study the behavior of human trophoblasts and other placental cells, as well as their ability to represent physiological conditions both in vivo and in vitro. An in vitro 3D model with a characteristic phenotype is of great benefit for the study of placental physiology. At the same time, it provides great support for future modeling of placental disease.

Insights into dovetailing GTD and Cancers

Gestational trophoblastic diseases (GTD) encompass a group of placental tumors which mostly arise due to certain fertilization defects, resulting in the over-proliferation of trophoblasts. The major characteristic of this diseased state is that β-hCG rises up manifold than that is observed during pregnancy. The incidence of GTD when analyzed on a global scale, figures out that there is a greater risk in South-East Asia, the reason of which remains unclear. An insight into any possible correlation of GTD incidence with cancers, other than choriocarcinoma, is being attempted here. Also, we review the recent developments in research on the molecular etiopathology of GTD. This review would render a wider eye towards a new paradigm of thoughts to connect GTD and breast cancer, which has not been into the picture till date.

Anti-tumor activity and immunological modification of ribosome-inactivating protein (RIP) from Momordica charantia by covalent attachment of polyethylene glycol

Ribosome-inactivating proteins (RIPs) are a family of enzymes that depurinate rRNA and inhibit protein biosynthesis. Here we report the purification, apoptosis-inducing activity, and polyethylene glycol (PEG) modification of RIP from the bitter melon seeds. The protein has a homogenous N-terminal sequence of NAsp- Val-Ser-Phe-Arg. Moreover, the RIP displayed strong apoptosis-inducing activity and suppressed cancer cell growth. This might be attributed to the activation of caspases-3. To make it available for in vivo application, the immunogenicity of RIP was reduced by chemical modification with 20 kDa (mPEG)(2)-Lys-NHS. The inhibition activity of both PEGylated and non-PEGylated RIP against cancer cells was much stronger than against normal cells, and the antigenicity of PEGylated RIP was reduced significantly. Our results suggested that the PEGylated RIP might be potentially developed as anti-cancer drug.

Live and let die - regulation of villous trophoblast apoptosis in normal and abnormal pregnancies

Since 1995 the number of publications investigating apoptosis in villous trophoblast has increased exponentially. This scientific interest is in part due to observations that this specialised form of cell death is increased in pregnancy complications such as pre-eclampsia and intra-uterine growth restriction. In addition, apoptosis is described in normal villous trophoblast and elements of the apoptotic machinery are involved in the fusion between cytotrophoblast and the overlying multinucleate syncytiotrophoblast. The increase in descriptions of apoptotic cell death in villous trophoblast has been accompanied by investigations of regulators of apoptosis. It is anticipated that understanding the regulation of apoptosis in villous trophoblast may provide new insights into placental pathologies. This review describes current knowledge regarding the expression and function of these regulators in villous trophoblast, both in normal and complicated pregnancies.

Effects of recombinant MAP30 on cell proliferation and apoptosis of human colorectal carcinoma LoVo cells

MAP30, an attractive protein isolated from bitter melon, has been previously found to have the anti-tumor and anti-HIV activities. In this study, MAP30 was cloned and expressed and the effects of the recombinant protein on cell proliferation and apoptosis of human colorectal carcinoma LoVo cells were investigated. The results showed that the proliferation of LoVo cells were significantly suppressed by MAP30 in time- and dose-dependent manners at the concentration ranging from 0.67 to 4.67 muM. The apoptotic nuclei of LoVo cells induced by MAP30 were obviously observed, and the genomic degradation was detected by single-cell gel electrophoresis (comet assay). Nuclear condensation and boundary aggregation or split, apoptotic bodies were seen by fluorescence and electron microscopy. The proportion of the periodic tumor cells was altered by MAP30. Sub-G1 curves were displayed by a flow cytometry analysis. Results of northern and western blots showed that the transcription and expression of Bax, a member of pro-apoptotic proteins, were gradually up-regulated as treated time increased. On the contrary, the transcription and expression of Bcl-2, an anti-apoptotic member, were down-regulated. These data provided powerful evidences for the first time that recombinant MAP30 can induce the apoptosis of the human colorectal carcinoma LoVo cells.

Epidermal growth factor rescues trophoblast apoptosis induced by reactive oxygen species

Pre-eclampsia and intrauterine growth restriction are associated with increased apoptosis of placental villous trophoblast. This may result from placental hypoperfusion, leading to the generation of reactive oxygen species (ROS). Apoptosis can be induced in villous trophoblast following exposure to oxidative stress. Epidermal growth factor (EGF) reduces trophoblast apoptosis resulting from exposure to hypoxia. We hypothesised that exposure to hydrogen peroxide, a potent generator of ROS, would induce apoptosis in term placental villous explants and that this could be reduced by treatment with EGF. Placental explants were taken from normal term pregnancies and exposed to increasing doses of hydrogen peroxide (0-1,000 microM) or to a combination of increasing doses of hydrogen peroxide and EGF (0-100 ng/ml) for either 6 or 48 h. Apoptosis was assessed by TUNEL, proliferation by Ki-67 immunostaining, necrosis by lactate dehydrogenase activity and trophoblast differentiation by human chorionic gonadotrophin (hCG) secretion in conditioned culture media. Immunoperoxidase staining was performed to identify phosphorylated-AKT (p-AKT) and phosphorylated-PI3 kinase (p-PI3k). Exposure to 1,000 microM hydrogen peroxide for 48 h induced apoptosis in placental explants. The increase in TUNEL positive nuclei predominantly localised to syncytiotrophoblast. The amount of apoptosis was reduced to control levels by treatment with 10 and 100 ng/ml EGF. Proliferation of cytotrophoblasts within villous explants was significantly reduced following exposure to 1,000 microM hydrogen peroxide, this was restored to control levels by simultaneous treatment with 10 or 100 ng/ml EGF. Neither exposure to hydrogen peroxide or EGF altered the amount of necrosis. There was increased immunostaining for pPI3K following treatment with EGF. This study shows that apoptosis may be induced in villous trophoblast following exposure to ROS, and demonstrates the anti-apoptotic effect of EGF in trophoblast, the maintenance of which is essential for normal pregnancy.

Proteomic Analysis of the Extraembryonic Tissue from Cloned Porcine Embryos

Cloned animals developed from somatic cell nuclear transfer (SCNT) embryos are useful resources for agricultural and medical applications. However, the birth rate in the cloned animals is very low, and the cloned animals that have survived show various developmental defects. In this report, we present the morphology and differentially regulated proteins in the extraembryonic tissue from SCNT embryos to understand the molecular nature of the tissue. We examined 26-day-old SCNT porcine embryos at which the sonogram can first detect pregnancy. The extraembryonic tissue from SCNT embryos was abnormally small compared with the control. In the proteomic analysis with the SCNT extraembryonic tissue, 39 proteins were identified as differentially regulated proteins. Among up-regulated proteins, Annexins and Hsp27 were found. They are closely related to the processes of apoptosis. Among down-regulated proteins, Peroxiredoxins and anaerobic glycolytic enzymes were identified. In the Western blot analysis, antioxidant enzymes and the antiapoptotic Bcl-2 protein were down-regulated, and caspases were up-regulated. In the terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) assay with the placenta from SCNT embryos, apoptotic trophoblasts were observed. These results demonstrate that a major reason for the low birth rate of cloned animals is due to abnormal apoptosis in the extraembryonic tissue during early pregnancy.

Changes in apoptosis and Bcl-2 expression in human hyperglycemic, term placental trophoblast

Apoptosis and its associated regulatory mechanisms are physiological events crucial to the maintenance of placental homeostasis; imbalance of these processes, however, such as occurs under various pathological conditions, may compromise placenta function and, consequently, pregnancy success. Increased apoptosis occurs in the placentas of pregnant women with several developmental disabilities, while increased Bcl-2 expression is generally associated with pregnancy-associated tumors. Herein, we tested the hypothesis that apoptosis-associated disturbs might be involved in the placental physiopathology subjected to different maternal hyperglycemic conditions. Thus, in the present study we investigated and compared the incidence of apoptosis using TUNEL reaction and Bcl-2 expression, in term-placentas of normoglycemic, diabetic and daily hyperglycemic patients. Tissue samples were collected from 37 placentas, being 15 from healthy mothers with normally delivered healthy babies, and 22 from mothers with glucose disturbances. From these latter 22 patients, 10 showed maternal daily hyperglycemia and 12 were clinically diabetics. Both Bcl-2 expression and apoptotic DNA fragmentation were established and quantified in the trophoblasts of healthy mothers. Compared to these reference values, a higher apoptosis index and lower Bcl-2 expression were disclosed in the placentas of the diabetic women, while in the daily hyperglycemic group, values were intermediate between the diabetic and normoglycemic patients. The TUNEL/Bcl-2 index ratio in the placentas varied from 0.02 to 0.09 for pregnant normoglycemic and diabetic women, respectively, revealing a predominance of apoptosis in the diabetic group. Our findings suggest that hyperglycemia may be a key factor evoking apoptosis in the placental trophoblast, and therefore, is relevant to diabetic placenta function.

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.

Expression of Bcl-2 and p53 at the fetal-maternal interface of rhesus monkey

To study the apoptosis and its mechanism at the fetal-maternal interface of early gestation, localization of apoptotic cells in the implantation sites of the rhesus monkey on day 17, 19, 28 and 34 of pregnancy were first examine by using the TUNEL technique. The expression of Ki67, a molecular marker of proliferating cells, and two apoptotic proteins, B cell lymphoma/leukaemia-2 (Bcl-2) and P53, were then studied by immunohistochemistry. Apoptotic nuclei were observed mainly in the syncytiotrophoblast. Ki67 was confined almost exclusively to cytotrophoblasts. The localization of Bcl-2 protein follows that of the apoptotic nuclei and its expression level increased as the development of the placenta progressed on. P53 was detected to some extent in cytotrophoblasts and syncytiotrophoblast covering the basal feet of the anchoring villi during the late stage of placentation. Based on these observations, it might be suggested that Bcl-2 could be possible to play an interesting role in limiting degree of nuclear degradation and sustaining cell survival in the multi-nucleated syncytiotrophoblast cells during early pregnancy, and P53 could also be essential in regulating the trophoblastic homeostasis by controlling its proliferation or apoptosis.

Caffeine suppresses the expression of the Bcl-2 mRNA in BeWo cell culture and rat placenta

Chronic caffeine exposure during pregnancy has an effect on fetal growth; however, the adverse effects of caffeine on embryogenesis are not well understood and controversial. We used cDNA microarray technology to determine whether caffeine alters gene expressions in a human cytotrophoblast-like cell line, BeWo. We found that the expression of the B-cell CLL/lymphoma 2 (Bcl-2) gene in BeWo cells was down-regulated by caffeine, suggesting that chronic exposure during the gestational period could exert an influence on embryogenesis. We then focused on the Bcl-2- and Bcl-2-associated X protein gene, Bax, to study the responsive gene expression in BeWo cells as well as placentas of pregnant rats fed a diet supplemented with caffeine (2 mg/100 g body weight) during gestation, and analyzed the gene expressions using LightCycler-based quantitative real-time polymerase chain reaction assays. We found a significantly decreased level of Bcl-2 mRNA expression, which demonstrated the influence of caffeine on placental function.

Expression of proliferation and apoptotic markers in human placenta during pregnancy

Trophoblast has unique properties in relation to its wide range of metabolic, endocrine and angiogenic functions. Trophoblastic cells invade endometrium and adjacent myometrium in a way that is imitated by malignant tumours. The aim of the present study was to analyse the expression of markers of proliferation and apoptosis in trophoblastic cells in normal human placenta during pregnancy. A total of 22 placentas, 12 of which were obtained from curettage and induced legal abortion and 10 placentas obtained from normal deliveries or caesarean sections were included in this study. Proliferation markers were strongly expressed in cytotrophoblast in early stages of gestation. In late term placentas, a distinct decrease in expression of these markers was observed. Syncytiotrophoblast was negative for proliferation markers in all placentas. Positive immunostaining for bcl-2, an anti-apoptotic marker, was observed only in syncytiotrophoblastic cells in first-trimester but also in third-trimester placentas. Cytotrophoblast and stromal mesenchymal cells of chorionic villi were negative for bcl-2. Expression of bcl-2 protein in syncytiotrophoblast may be one of the major factors preventing these structures from early cell death, which is indispensable for the maintenance of physiological pregnancy.

Apoptosis and related proteins in placenta of intrauterine fetal death in prostaglandin f receptor-deficient mice

The present study investigated whether the increase of apoptosis in the placenta is associated with intrauterine fetal death in prostaglandin F receptor-deficient mice. Apoptosis was demonstrated within placental and decidual tissue by the TUNEL method. The majority of apoptosis was found in syncytiotrophoblast tissues. Enhanced TUNEL-positive staining in the syncytiotrophoblast layer was scattered in the placental tissues in clusters of apoptotic cells in the death group. Marked TUNEL-positive cells were identified in decidua of both groups. The rate of apoptosis in the placenta and decidua in the death group was higher than that in the survival group (P < 0.05). Immunohistochemical analysis showed that the level of active caspase-3 protein expression in the placenta in the death group was much higher than that in the survival group. The level of Bcl-2 protein expression in the placenta in the death group was much lower than that in the survival group. Western blot analysis demonstrated that increased expression of the active form of caspase-3 was detected in the placenta and decidua in the death group compared with that in the survival group. In contrast, a decrease in the expression of Bcl-2 was detected in the placenta and decidua in the death group compared with that in the survival group. Enhanced expression of Bax:Bcl-2 ratio was detected in placenta and decidua in the death group compared with that in the survival group. Thus, significantly increased apoptosis in the mouse placenta and decidua might be involved in the pathophysiologic mechanism of intrauterine fetal death.

Maternal diabetes mellitus is associated with altered deposition of fibrin-type fibrinoid at the villous surface in term placentae

Placentae from control and diabetic patients were used to test three null hypothesis: (1) there are no significant group differences in the volumes of villous syncytiotrophoblast compartments or intervillous fibrin-type fibrinoid, (2) perivillous fibrin-type fibrinoid is deposited randomly at the surface of trophoblast, and (3) amounts and deposition patterns of perivillous fibrin-type fibrinoid do not vary between groups. Term placentae were collected from non-diabetic subjects and five groups of diabetic women classified according to duration, severity and insulin dependence. Tissue specimens and sections were obtained by uniform random sampling. Volumes and surface areas of fibrin-type fibrinoid and trophoblast compartments (thin, syncytial knot, syncytial bridge and denuded regions) were estimated stereologically and compared using variance, chi-squared and contingency table analyses. As to null hypothesis (1), no group differences in volumes of trophoblast compartments were found but volumes of intervillous fibrin-type fibrinoid were greater in the non-insulin-dependent diabetic group. As to null hypothesis (2), regardless of group, fibrin-type fibrinoid was deposited preferentially at sites of denudation in every placenta examined. As to null hypothesis (3), villous surface areas occupied by perivillous fibrin-type fibrinoid were greater in type 1 (insulin-dependent) diabetics with complications (diabetic nephropathy or retinopathy). The surfaces of trophoblast occupied by fibrin-type fibrinoid were also notably larger in non-insulin-dependent diabetics and type 1 diabetics with complications. Except for the surface of denudation sites (which also increased in diabetes), there were no differences in the surfaces of trophoblast regions. These results confirm that the haemostatic steady state is perturbed in the diabetic placenta, that perivillous fibrin-type fibrinoid is deposited preferentially at sites of epithelial loss/damage, and that some diabetic groups are affected differentially.

The thrombomodulin-protein C system is essential for the maintenance of pregnancy

Disruption of the mouse gene encoding the blood coagulation inhibitor thrombomodulin (Thbd) leads to embryonic lethality caused by an unknown defect in the placenta. We show that the abortion of thrombomodulin-deficient embryos is caused by tissue factor-initiated activation of the blood coagulation cascade at the feto-maternal interface. Activated coagulation factors induce cell death and growth inhibition of placental trophoblast cells by two distinct mechanisms. The death of giant trophoblast cells is caused by conversion of the thrombin substrate fibrinogen to fibrin and subsequent formation of fibrin degradation products. In contrast, the growth arrest of trophoblast cells is not mediated by fibrin, but is a likely result of engagement of protease-activated receptors (PAR)-2 and PAR-4 by coagulation factors. These findings show a new function for the thrombomodulin-protein C system in controlling the growth and survival of trophoblast cells in the placenta. This function is essential for the maintenance of pregnancy.

Apoptosis and related proteins during parturition in prostaglandin F receptor-deficient mice

This study investigated whether apoptosis and related proteins are involved in parturition by comparative observation of FP-deficient mice without labor and wild type mice with vaginal delivery. We examined the expression of apoptosis, Fas, FasL, active caspase-3 and bcl-2 proteins in the amnion, placenta and decidua. DNA laddering in the amnion, placenta and decidua tissue did not significantly differ between FP-deficient and wild type mice on day 18 of pregnancy. Similar TUNEL staining results were found in all tissues of FP-deficient mice compared with those of wild type mice. A higher intensity of apoptotic cells was found in the decidua basalis. The index of TUNEL-positive cells were not significantly different in the amnion, placenta and decidua of FP-deficient mice compared with that of wild type mice on day 18 of pregnancy. Specific bands for Fas were clearly observed in the amnion, placenta and decidua tissue. FasL specific bands were observed in the placenta and decidua, but a few in amnion tissue. A great number of active caspase-3 specific bands were detected in decidua, while a few such bands were detected in the placenta and few bands in the amniotic tissue. Bands for bcl-2 were detected in the amnion, placenta and decidua tissue. The weakest band was in decidual tissue. Fas, FasL, active caspase-3, and bcl-2 specific bands did not show any significant differences between the two groups. These findings demonstrate that apoptosis, Fas, FasL, caspase-3, and Bcl-2 occur in mouse term placenta that is not involved in parturition.

Apoptosis in the first trimester human placenta: the role in maintaining immune privilege at the maternal-foetal interface and in the trophoblast remodelling

Apoptosis has been proposed as a mechanism for maintaining immune privilege. Expression of Fas ligand (FasL) by the human trophoblast has been recently accepted as a mechanism providing protection against the lytic action of activated decidual immune cells expressing Fas receptor (FasR). Therefore, the purpose of this review was to determine the role of apoptosis in early pregnancy maintenance according to the latest literature. We used Medline literature search. The data suggest that apoptosis may serve as a previously unsuspected mechanism that induces tolerance of the foetal allograft against maternal immune system. Apoptosis of activated maternal immune cells occurs in the human decidua mainly through Fas-FasL or receptor for TNF-related apoptosis-inducing ligand (TRAIL-R)-TNF-related apoptosis-inducing ligand (TRAIL) signalling. This might be a defence mechanism against rejection of the foetal allograft by the maternal immune system. In addition, in this review contribution of programmed cell death to placental cell turnover and remodelling during first trimester of pregnancy is also discussed.

Expression of BCL-2, BAX and BAK in the trophoblast layer of the term human placenta: a unique model of apoptosis within a syncytium

The regulation of apoptosis in the syncytiotrophoblast is of particular interest because this is the only true syncytial epithelium in human cell biology. Nuclei characteristic of apoptotic cells have been localized to this syncytium especially in association with fibrin-containing fibrinoid deposits. The factors responsible for regulating cell death-like features in the trophoblast syncytium are unknown. We tested the hypothesis that fibrin was required for trophoblast apoptosis. TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP end-labelling) staining to detect DNA fragmentation typical of apoptosis was performed in term human placentae revealing labelled nuclei associated with fibrin-type fibrinoid, as well as labelled nuclei in discrete areas of syncytiotrophoblast without fibrin. We also hypothesized that members of the BCL-2 family of apoptosis-associated proteins contribute to the regulation of syncytiotrophoblast apoptosis. To identify members of this protein family that might regulate trophoblast apoptosis, we assessed expression of three important members of the bcl-2 gene family. We used immunohistochemistry with monoclonal antisera against human BCL-2 and polyclonal antisera against human BAX and BAK to study paraffin-embedded sections of human term placentae (n=5) from uncomplicated pregnancies. The anti-apoptotic BCL-2 protein was expressed throughout the syncytium of normal villi with much less staining in cytotrophoblast. Staining was also seen adjacent to fibrin deposits and in syncytium overlying fibrin deposits. Expression of the pro-apoptotic BAX protein was undetectable in the syncytiotrophoblast, was expressed in rare cytotrophoblast and was prominent in connective tissue and perivascular cells within the villous core. Localization of a second pro-apoptotic protein, BAK, revealed immunoreactivity in isolated areas of intact syncytium of normal villi. Additionally, fibrin deposits were associated with intense BAK staining in both syncytiotrophoblast and cytotrophoblast. From these data, we speculate that modulation of BAK expression is one factor regulating apoptosis in human trophoblast.

To be, or not to be, that is the question. Apoptosis in human trophoblast

Apoptosis, the morphology of cell suicide, may result from programmed cell death or may be a response to exogenous stimuli. Apoptosis can be induced in cultured trophoblast and can be identified in the trophoblast of placental villi. The trophoblast regulates maternal-fetal gas, nutrient and waste product exchange; therefore, the presence of apoptosis in this key cellular interface highlights the importance of understanding what controls apoptosis in the placenta. In this review, we describe the signal transduction pathways that trigger apoptosis in other systems, identify key genetic controls for the process and outline the final common pathway which effects execution in cells committed to suicide. Multiplicity, redundancy and cross talk among pathways characterize the surface membrane signals and exogenous stimuli that trigger apoptosis in other cells. As each step in the apoptotic process is discussed, we describe what is known about the step in human placental villi. Recent studies suggest that a further understanding of receptor-mediated signalling pathways, the Bcl-2 regulators and the caspases and substrates involved in placental apoptosis will surely provide insights into both normal placental development and the placental dysfunction associated with some abnormal pregnancies.