Trophoblast apoptosis from pregnancies complicated by fetal growth restriction is associated with enhanced p53 expression

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.

Placental adaptations in growth restriction

The placenta is the primary interface between the fetus and mother and plays an important role in maintaining fetal development and growth by facilitating the transfer of substrates and participating in modulating the maternal immune response to prevent immunological rejection of the conceptus. The major substrates required for fetal growth include oxygen, glucose, amino acids and fatty acids, and their transport processes depend on morphological characteristics of the placenta, such as placental size, morphology, blood flow and vascularity. Other factors including insulin-like growth factors, apoptosis, autophagy and glucocorticoid exposure also affect placental growth and substrate transport capacity. Intrauterine growth restriction (IUGR) is often a consequence of insufficiency, and is associated with a high incidence of perinatal morbidity and mortality, as well as increased risk of cardiovascular and metabolic diseases in later life. Several different experimental methods have been used to induce placental insufficiency and IUGR in animal models and a range of factors that regulate placental growth and substrate transport capacity have been demonstrated. While no model system completely recapitulates human IUGR, these animal models allow us to carefully dissect cellular and molecular mechanisms to improve our understanding and facilitate development of therapeutic interventions.

Vitamin C Induces the Reduction of Oxidative Stress and Paradoxically Stimulates the Apoptotic Gene Expression in Extravillous Trophoblasts Derived From First-Trimester Tissue

AIM

To investigate the effects of vitamin C on the expression of the genes related to apoptosis in extravillous trophoblasts (EVTs) in the first trimester.

METHODS

Extravillous trophoblasts were cultured under 2% O2 followed by 2% O2 or 8% O2 with or without vitamin C. The level of reactive oxygen species (ROS) in the cultured medium was estimated using electron spin resonance spectroscopy. The expression levels of the genes TP53, BCL2, and BAX were quantified using real-time quantitative polymerase chain reaction.

RESULTS

Reactive oxygen species were found to be decreased after adding vitamin C under increasing oxygen concentrations. In addition, the ratio of BAX/BCL2 also increased after adding vitamin C under conditions of 2% O2, while the gene expression level of BCL2 increased after adding vitamin C under increasing oxygen concentrations. In contrast, the gene expression level of TP53 and the ratio of BAX/BCL2 both decreased.

CONCLUSION

We have revealed that vitamin C reduces ROS and may promote the apoptosis of EVTs under conditions of 2% O2 while paradoxically preventing apoptosis under increasing oxygen concentrations.

UNDERSTANDING THE PLACENTAL AETIOLOGY OF FETAL GROWTH RESTRICTION; COULD THIS LEAD TO PERSONALIZED MANAGEMENT STRATEGIES?

Fetal growth restriction (FGR) is defined as the failure of a fetus to attain its full genetic growth potential. It is a leading cause of stillbirth, prematurity, cerebral palsy and perinatal mortality. Small size at birth increases surviving infants’ lifelong risk of adverse health outcomes associated with the metabolic syndrome. The pathophysiology of abnormal fetal growth is extremely complex and incompletely understood, with a plethora of genetic, signalling and metabolic candidates under investigation, many of which may result in abnormal structure and function of the placenta. In contrast to, or maybe because of, the underlying complexities of FGR, the strategies clinicians have for identifying and managing this outcome are conspicuously limited. Current clinical practice is restricted to identifying pregnancies at risk of FGR, and when FGR is detected, using intensive monitoring to guide the timing of delivery to optimise fetal outcomes. Abnormal Doppler indices in the umbilical artery are strongly associated with poor perinatal outcomes and are currently the “gold standard” for clinical surveillance of the growth-restricted fetus.

Hypoxia-inducible regulation of placental BOK expression

Pre-eclampsia, a disorder of pregnancy, is characterized by placental hypoxia and cell death. Hypoxia shifts the intricate balance between death-inducing BOK and survival-promoting MCL1 towards BOK, thereby triggering placental cell death. Here, we show that BOK is a direct target of HIF.

Apoptosis of alcohol-exposed human placental cytotrophoblast cells is downstream of intracellular calcium signaling

BACKGROUND

Apoptosis is induced by ethanol (EtOH) in human placental trophoblast cells, possibly disrupting placentation and contributing to intrauterine growth restriction in fetal alcohol spectrum disorder (FASD). EtOH induces programmed cell death in several embryonic tissues by raising intracellular Ca(2+) . Therefore, the role of Ca(2+) signaling in EtOH-induced apoptosis was examined using human first trimester cytotrophoblast cell lines, examining the hypothesis that apoptosis is dependent on intracellular Ca(2+) signaling.

METHODS

Using HTR-8/SVneo and SW.71 cytotrophoblast cell lines, real-time intracellular Ca(2+) concentration was monitored by fluo-4 epifluorescence microscopy and apoptosis was assessed by flow cytometry of cells fluorescently labeled for DNA fragmentation (TUNEL) and annexin V binding.

RESULTS

Intracellular Ca(2+) concentrations increased synchronously in all cells within 10 seconds of exposure to 50 mM EtOH, but not at lower EtOH concentrations (10 to 25 mM) incapable of inducing apoptosis. Trophoblast cells treated with inhibitors of Ca(2+) signaling (BAPTA-AM, U73122, xestospongin D, BAPTA, SKF-96365) produced no intracellular Ca(2+) transients after exposure to 50 mM EtOH and were protected from cell death induced by EtOH.

CONCLUSIONS

EtOH-induced apoptosis in human cytotrophoblast cells, identified by DNA fragmentation and externalized phosphatidylserine, was dependent upon Ca(2+) signaling. Both intracellular Ca(2+) mobilization and extracellular Ca(2+) influx were required, as well as phosphatidylinositol signaling. Inhibition by SKF-96365 suggests that the capacitative Ca(2+) entry mechanism that utilizes TRPC channels was activated by EtOH. Apoptosis occurs downstream of Ca(2+) signaling in trophoblasts and may contribute to placental insufficiency and poor fetal growth associated with FASD.

A role for the mitochondrial-associated protein p32 in regulation of trophoblast proliferation

p32 is a conserved eukaryotic protein which is primarily expressed in the mitochondria and regulates cell proliferation, migration and metabolism in various tissues. In this study, we sought to examine the expression and function of p32 in the human placenta. p32 was highly expressed in the syncytiotrophoblast, the underlying cytotrophoblast (CTB), the vascular endothelium and by a proportion of cells in the villous stroma in first trimester and term placenta. p32 mRNA and protein expression was significantly higher in the first trimester of pregnancy than at term, and expression in the trophoblast was significantly reduced in placentas from women with fetal growth restriction (FGR). Small interfering RNA (siRNA)-mediated knockdown of p32 in term placental explants significantly reduced the number of Ki67-positive CTB, but did not alter CTB apoptosis or necrosis. p32 knockdown increased lactate production, reduced glucose extraction from culture medium and was associated with reduced MitoTracker dye accumulation in trophoblast mitochondria. p32 knockdown was also associated with a significant reduction in expression of the mitochondrial respiratory complexes I and IV. These data suggest that p32 expression is important for CTB proliferation, via a mechanism involving regulation of normal mitochondrial function. As p32 expression is reduced in FGR placentas, this may contribute to some of the observed placental pathology, such as reduced CTB proliferation and mitochondrial dysfunction.

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.

Preeclampsia is associated with alterations in the p53-pathway in villous trophoblast

BACKGROUND

Preeclampsia (PE) is characterized by exaggerated apoptosis of the villous trophoblast of placental villi. Since p53 is a critical regulator of apoptosis we hypothesized that excessive apoptosis in PE is mediated by abnormal expression of proteins participating in the p53 pathway and that modulation of the p53 pathway alters trophoblast apoptosis in vitro.

METHODS

Fresh placental villous tissue was collected from normal pregnancies and pregnancies complicated by PE; Western blotting and real-time PCR were performed on tissue lysate for protein and mRNA expression of p53 and downstream effector proteins, p21, Bax and caspases 3 and 8. To further assess the ability of p53 to modulate apoptosis within trophoblast, BeWo cells and placental villous tissue were exposed to the p53-activator, Nutlin-3, alone or in combination with the p53-inhibitor, Pifithrin-α (PFT-α). Equally, Mdm2 was knocked-down with siRNA.

RESULTS

Protein expression of p53, p21 and Bax was significantly increased in pregnancies complicated by PE. Conversely, Mdm2 protein levels were significantly depleted in PE; immunohistochemistry showed these changes to be confined to trophoblast. Reduction in the negative feedback of p53 by Mdm2, using siRNA and Nutlin-3, caused an imbalance between p53 and Mdm2 that triggered apoptosis in term villous explants. In the case of Nutlin, this was attenuated by Pifithrin-α.

CONCLUSIONS

These data illustrate the potential for an imbalance in p53 and Mdm2 expression to promote excessive apoptosis in villous trophoblast. The upstream regulation of p53 and Mdm2, with regard to exaggerated apoptosis and autophagy in PE, merits further investigation.

p53 signaling pathway polymorphisms associated to recurrent pregnancy loss

The p53 protein is known for performing essential functions in the maintenance of genomic stability in somatic cells and prevention of tumor formation. Studies of the p53 signaling pathway have suggested associations between some polymorphisms and infertility, post-in vitro fertilization implantation failure and recurrent abortions. The TP53 Pro72Arg polymorphism has been implicated as a risk factor for recurrent pregnancy loss (RPL); however, the association is controversial. In this study, our objective was to evaluate selected polymorphisms in genes of the p53 signalling pathway [TP53 c.215G>C (Pro72Arg), MDM2 c.14+309T>G (SNP309) and LIF c.1414T>G in the region 3' UTR] and determine their effect as risk factors for RPL. In a case-control study, we investigated 120 women with two or more pregnancy losses and 143 fertile control women reporting at least two live births and no history of pregnancy loss. When analyzed separately, the allele and genotype distributions of the polymorphisms in the two groups were not different. However, in a multivariate analysis adjusted for alcohol consumption, smoking, ethnicity, and number of pregnancies, the interaction between the genotypes TP53 Arg/Arg (rs1042522) and MDM2 TT (rs2279744) showed to be associated to RPL, increasing the risk for this condition (OR = 2.58, 95% CI: 1.31-5.07, p = 0.006). In conclusion, our study indicates that the combination of TP53 Arg/Arg (rs1042522) and MDM2 TT (rs2279744) genotypes may be a risk factor for RPL.

Circulating RNA coding genes regulating apoptosis in maternal blood in severe early onset fetal growth restriction and pre-eclampsia

OBJECTIVE

To determine whether the intrinsic apoptosis pathway is differentially expressed in placenta and maternal blood in severe preterm fetal growth restriction (FGR) and pre-eclampsia (PE), and to examine whether circulating RNA in maternal blood may be potential biomarkers.

STUDY DESIGN

Maternal blood samples and placental biopsies were collected from women with preterm: FGR (n=20), PE without FGR (n=8) and controls (n=20). Real-time PCR examined the expression of genes in the intrinsic apoptosis pathway in FGR and PE, stratified according to the severity of placental insufficiency.

RESULT

Severe preterm FGR, with or without PE, was associated with increased expression of BCL2, BCL-XL, BIM, BAD and Survivin in both the placenta and maternal blood (1.6 to 3.3-fold, P<0.05). In preterm PE, but not FGR, there was increased placental expression of BCL-XL and BCL2 (1.6 to 2.5-fold, P<0.05), but only BCL2 was significantly increased in the maternal blood (1.8-fold, P<0.05). Increased expression of genes of the intrinsic apoptosis pathway reflected the severity of FGR as determined by deteriorations in umbilical artery Doppler velocimetry.

CONCLUSION

In severe early onset FGR there was increased expression of genes regulating intrinsic apoptosis in both the placenta and maternal blood. Circulating RNA regulating placenta apoptosis may be used to develop noninvasive novel biomarkers for FGR.

Homeobox gene transforming growth factor β-induced factor-1 (TGIF-1) is a regulator of villous trophoblast differentiation and its expression is increased in human idiopathic fetal growth restriction

Abnormal trophoblast function is associated with human fetal growth restriction (FGR). Targeted disruption of homeobox gene transforming growth β-induced factor (TGIF-1) results in placental dysfunction in the mouse. The role of human TGIF-1 in placental cell function is unknown. The aims of this study were to determine the expression of TGIF-1 in human idiopathic FGR-affected placentae compared with gestation-matched controls (GMC), to elucidate the functional role of TGIF-1 in trophoblasts and to identify its downstream targets. Real-time PCR and immunoblotting revealed that TGIF-1 mRNA and protein expression was significantly increased in FGR-affected placentae compared with GMC (n = 25 in each group P < 0.05). Immunoreactive TGIF-1 was localized to the villous cytotrophoblasts, syncytiotrophoblast, microvascular endothelial cells and in scattered stromal cells in both FGR and GMC. TGIF-1 inactivation in BeWo cells using two independent siRNA resulted in significantly decreased mRNA and protein of trophoblast differentiation markers, human chorionic gonadotrophin (CGB/hCG), syncytin and 3β-hydroxysteroid dehydrogenase/3β-honest significant difference expression. Our data demonstrate that homeobox gene TGIF-1 is a potential up-stream regulator of trophoblast differentiation and the altered TGIF-1 expression may contribute to aberrant villous trophoblast differentiation in FGR.

Identification of autophagic vacuoles and regulators of autophagy in villous trophoblast from normal term pregnancies and in fetal growth restriction

Fetal growth restriction (FGR) is a serious pregnancy complication associated with increased perinatal mortality and morbidity. Although the majority of cases with FGR result from placental dysfunction, the pathophysiology is incompletely understood. Autophagy is a physiological form of cell degradation exacerbated by nutrient and oxygen restriction, which are both thought to play a role in the aetiology of FGR. We hypothesized that autophagy is present in the normal human placenta and is exaggerated in FGR. Autophagy was assessed in electron micrographs from normal and FGR placentas and by Western blotting for LC3B and LAMP-2. The localization of regulators of autophagy was examined by immunohistochemistry. Culture of BeWo cells was used to investigate whether nutrient and/or oxygen deprivation can induce autophagy in trophoblast. Autophagy predominantly localized to the syncytiotrophoblast layer and autophagosomes were more frequent in FGR. The regulators LAMP-2, LC3B, Beclin-1, ATG 5, ATG9 and ATG16L1 were all present in villous trophoblast. LAMP-2 immunostaining was more punctate in FGR. In BeWo cells, culture in reduced oxygen tension and/or serum depleted conditions led to the appearance of autophagosomes which was associated with changes in LAMP-2 configuration. We conclude that autophagy in human term placenta may be involved in the placental dysfunction present in FGR.

A systematic screen reveals MicroRNA clusters that significantly regulate four major signaling pathways

MicroRNAs (miRNAs) are encoded in the genome as individual miRNA genes or as gene clusters transcribed as polycistronic units. About 50% of all miRNAs are estimated to be co-expressed with neighboring miRNAs. Recent studies have begun to illuminate the importance of the clustering of miRNAs from an evolutionary, as well as a functional standpoint. Many miRNA clusters coordinately regulate multiple members of cellular signaling pathways or protein interaction networks. This cooperative method of targeting could produce effects on an overall process that are much more dramatic than the smaller effects often associated with regulation by an individual miRNA. In this study, we screened 366 human miRNA minigenes to determine their effects on the major signaling pathways culminating in AP-1, NF-κB, c-Myc, or p53 transcriptional activity. By stratifying these data into miRNA clusters, this systematic screen provides experimental evidence for the combined effects of clustered miRNAs on these signaling pathways. We also verify p53 as a direct target of miR-200a. This study is the first to provide a panoramic view of miRNA clusters' effects on cellular pathways.

Increased autophagy in placentas of intrauterine growth-restricted pregnancies

Background

Unexplained intrauterine growth restriction (IUGR) may be a consequence of placental insufficiency; however, its etiology is not fully understood. We surmised that defective placentation in IUGR dysregulates cellular bioenergic homeostasis, leading to increased autophagy in the villous trophoblast. The aims of this work were (1) to compare the differences in autophagy, p53 expression, and apoptosis between placentas of women with normal or IUGR pregnancies; (2) to study the effects of hypoxia and the role of p53 in regulating trophoblast autophagy; and (3) to investigate the relationship between autophagy and apoptosis in hypoxic trophoblasts.

Methodology/Principal Findings

Compared with normal pregnant women, women with IUGR had higher placental levels of autophagy-related proteins LC3B-II, beclin-1, and damage-regulated autophagy modulator (DRAM), with increased p53 and caspase-cleaved cytokeratin 18 (M30). Furthermore, cytotrophoblasts cultured under hypoxia (2% oxygen) in the presence or absence of nutlin-3 (a p53 activity stimulator) had higher levels of LC3B-II, DRAM, and M30 proteins and increased Bax mRNA expression compared with controls cultured under standard conditions. In contrast, administration of pifithrin-α (a p53 activity inhibitor) during hypoxia resulted in protein levels that were similar to those of the control groups. Moreover, cytotrophoblasts transfected with LC3B, beclin-1, or DRAM siRNA had higher levels of M30 compared with the controls under hypoxia. However, transfection with Bcl-2 or Bax siRNA did not cause any significant change in the levels of LC3B-II in hypoxic cytotrophoblasts.

Conclusions/Significance

Together, these results suggest that there is a crosstalk between autophagy and apoptosis in IUGR and that p53 plays a pivotal and complex role in regulating trophoblast cell turnover in response to hypoxic stress.

The effects of oxidative stress on female reproduction: a review

Oxidative stress (OS), a state characterized by an imbalance between pro-oxidant molecules including reactive oxygen and nitrogen species, and antioxidant defenses, has been identified to play a key role in the pathogenesis of subfertility in both males and females. The adverse effects of OS on sperm quality and functions have been well documented. In females, on the other hand, the impact of OS on oocytes and reproductive functions remains unclear. This imbalance between pro-oxidants and antioxidants can lead to a number of reproductive diseases such as endometriosis, polycystic ovary syndrome (PCOS), and unexplained infertility. Pregnancy complications such as spontaneous abortion, recurrent pregnancy loss, and preeclampsia, can also develop in response to OS. Studies have shown that extremes of body weight and lifestyle factors such as cigarette smoking, alcohol use, and recreational drug use can promote excess free radical production, which could affect fertility. Exposures to environmental pollutants are of increasing concern, as they too have been found to trigger oxidative states, possibly contributing to female infertility. This article will review the currently available literature on the roles of reactive species and OS in both normal and abnormal reproductive physiological processes. Antioxidant supplementation may be effective in controlling the production of ROS and continues to be explored as a potential strategy to overcome reproductive disorders associated with infertility. However, investigations conducted to date have been through animal or in vitro studies, which have produced largely conflicting results. The impact of OS on assisted reproductive techniques (ART) will be addressed, in addition to the possible benefits of antioxidant supplementation of ART culture media to increase the likelihood for ART success. Future randomized controlled clinical trials on humans are necessary to elucidate the precise mechanisms through which OS affects female reproductive abilities, and will facilitate further explorations of the possible benefits of antioxidants to treat infertility.

Cell free expression of hif1α and p21 in maternal peripheral blood as a marker for preeclampsia and fetal growth restriction

Preeclampsia, a severe unpredictable complication of pregnancy, occurs in 6% of pregnancies, usually in the second or third trimester. The specific etiology of preeclampsia remains unclear, although the pathophysiological hallmark of this condition appears to be an inadequate blood supply to the placenta. As a result of the impaired placental blood flow, intrauterine growth restriction (IUGR) and consequential fetal oxidative stress may occur. Consistent with this view, pregnancies complicated by preeclampsia and IUGR are characterized by up-regulation of key transcriptional regulators of the hypoxic response including, hif1α and as well as p53 and its target genes. Recently, the presence of circulating cell-free fetal RNA has been documented in maternal plasma. We speculated that pregnancies complicated by preeclampsia and IUGR, will be associated with an abnormal expression of p53 and/or hif1α related genes in the maternal plasma. Maternal plasma from 113 singleton pregnancies (72 normal and 41 complicated pregnancies) and 19 twins (9 normal and 10 complicated pregnancies) were collected and cell free RNA was extracted. The expression of 18 genes was measured by one step real-time RT-PCR and was analyzed for prevalence of positive/negative expression levels. Results indicate that, among the genes examined, cell free plasma expressions of p21 and hif1α were more prevalent in pregnancies complicated by hypoxia and/or IUGR (p<0.001). To conclude, we present in this manuscript data to support the association between two possible surrogate markers of hypoxia and common complications of pregnancy. More work is needed in order to implement these findings in clinical practice.

The double life of MULE in preeclamptic and IUGR placentae

The E3 ubiquitin ligase MULE (Mcl-1 Ubiquitin Ligases E3) targets myeloid cell leukemia factor 1 (Mcl-1) and tumor suppressor p53 for proteasomal degradation. Although Mcl-1 and p53 have been implicated in trophoblast cell death in preeclampsia (PE) and intrauterine growth restriction (IUGR), the mechanisms regulating their expression in the human placenta remains elusive. Herein, we investigated MULE's involvement in regulating Mcl-1 and p53 degradation during normal and abnormal (PE, IUGR) placental development. MULE expression peaked at 5–7 weeks of gestation, when oxygen tension is low and inversely correlated with that of Mcl-1 and p53. MULE efficiently bound to Mcl-1 and p53 and regulated their ubiquitination during placental development. Exposure of first trimester villous explants to 3% O₂ resulted in elevated MULE expression compared with 20% O₂. Low-oxygen-induced MULE expression in JEG3 choriocarcinoma cells was abolished by hypoxia-inducible factor (HIF)-1α siRNA. MULE was overexpressed in both PE and IUGR placentae. In PE, MULE preferentially targeted p53 for degradation, allowing accumulation of pro-apoptotic Mcl-1 isoforms. In IUGR, however, MULE targeted pro-survival Mcl-1, allowing p53 to accumulate and exert its apoptotic function. These data demonstrate that oxygen regulates Mcl-1 and p53 stability during placentation via HIF-1-controlled MULE expression. The different preferential targets of MULE in PE and IUGR placentae classify early-onset PE and IUGR as distinct molecular pathologies.

Maternal perception of reduced fetal movements is associated with altered placental structure and function

Background

Maternal perception of reduced fetal movement (RFM) is associated with increased risk of stillbirth and fetal growth restriction (FGR). DFM is thought to represent fetal compensation to conserve energy due to insufficient oxygen and nutrient transfer resulting from placental insufficiency. To date there have been no studies of placental structure in cases of DFM.

Objective

To determine whether maternal perception of reduced fetal movements (RFM) is associated with abnormalities in placental structure and function.

Design

Placentas were collected from women with RFM after 28 weeks gestation if delivery occurred within 1 week. Women with normal movements served as a control group. Placentas were weighed and photographs taken. Microscopic structure was evaluated by immunohistochemical staining and image analysis. System A amino acid transporter activity was measured as a marker of placental function.

Placentas from all pregnancies with RFM (irrespective of outcome) had greater area with signs of infarction (3.5% vs. 0.6%; p<0.01), a higher density of syncytial knots (p<0.001) and greater proliferation index (p<0.01). Villous vascularity (p<0.001), trophoblast area (p<0.01) and system A activity (p<0.01) were decreased in placentas from RFM compared to controls irrespective of outcome of pregnancy.

Conclusions

This study provides evidence of abnormal placental morphology and function in women with RFM and supports the proposition of a causal association between placental insufficiency and RFM. This suggests that women presenting with RFM require further investigation to identify those with placental insufficiency.

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.

Pro-inflammatory cytokine-stimulated first trimester decidual cells enhance macrophage-induced apoptosis of extravillous trophoblasts

OBJECTIVE

As human blastocyst-derived extravillous trophoblasts (EVTs) invade the early decidua, they are positioned to interact with immune cells and resident decidual cells, and remodel spiral arteries into high capacity vessels that increase blood flow to the developing fetal-placental unit. Shallow EVT invasion elicits incomplete vascular transformation and reduces uteroplacental blood flow that presages adverse pregnancy outcomes. Excess macrophages in the decidua induce EVT apoptosis via tumor necrosis factor-alpha (TNF-α) secretion. Our previous observation that pro-inflammatory cytokines enhance neutrophil and macrophage activator granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in first trimester decidual cells is now extended to include: (1) the specific macrophage activator M-CSF; (2) macrophage activation and subsequent enhancement of EVT apoptosis by both GM-CSF and M-CSF.

STUDY DESIGN

Quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay assessed M-CSF expression in first trimester decidual cells incubated with interleukin-1 beta (IL-1β) or TNF-α. Peripheral monocyte-derived macrophages pre-incubated with conditioned media from decidual cell cultures were co-cultured with a first trimester EVT cell line, HTR-8/SVneo cells. Macrophage activation was examined and EVT apoptosis evaluated by DNA fragmentation, caspase activation and cell membrane asymmetry.

RESULTS

IL-1β or TNF-α significantly enhanced M-CSF expression in first trimester decidual cells. The conditioned media from these cultures activates macrophages, which promote caspase 3/7-dependent EVT apoptosis with antibodies against GM-CSF or M-CSF blocking this effect.

CONCLUSIONS

Pro-inflammatory cytokines increases synthesis of M-CSF in first trimester decidual cells. Both GM-CSF and M-CSF activate macrophages, which initiate caspase-dependent EVT apoptosis.

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.

Reduced expression of survivin, the inhibitor of apoptosis protein correlates with severity of preeclampsia

INTRODUCTION

Preeclampsia is a major complication of pregnancy affecting maternal and fetal health. Although the pathogenesis of preeclampsia is unclear, it is believed that trophoblast apoptosis plays an important role in the pathogenesis of preeclampsia during pregnancy. Survivin is a member of the inhibitor of apoptosis protein family that uniquely promotes trophoblast proliferation. In this study we investigated the alteration of survivin levels during pregnancy and compared the survivin protein and mRNA between preeclampsia and normal pregnancy.

METHODS

The mRNA level of survivin in first, second and third trimester placentae was measured by Real-time PCR. The expression of survivin in preeclamptic placentae (including severe and mild preeclampsia) and in age-matched normal placentae was measured by immunohistochemistry. The mRNA levels of survivin in preeclamptic or normal placentae were measured by Real-time PCR.

RESULTS

The mRNA level of survivin was significantly reduced throughout gestation. The mRNA level of survivin in preeclamptic placentae was significantly reduced compared to that in normal placenta. The mRNA level of survivin in severe preeclamptic placentae was further significantly reduced compared to that in mild preeclamptic placentae. In addition, survivin was expressed on syncytiotrophoblasts and cytotrophoblasts and the expression of survivin was significantly decreased in preeclamptic placenta compared to that in normal placenta (p=0.01). Furthermore the expression of survivin in severe preeclamptic placentae was significantly lower than that in mild preeclamptic placentae.

CONCLUSION

Our current data suggests lower placental expression of survivin may be associated with the severity of preeclampsia.

The timing and duration of hypoxia determine gene expression patterns in cultured human trophoblasts

OBJECTIVE

Exposure of cultured trophoblasts to hypoxia is commonly used to interrogate the molecular mechanisms underlying placental hypoxic injury. We examined the effect of levels, durations, and patterns of hypoxia on gene expression patterns in primary human trophoblasts.

STUDY DESIGN

We exposed primary term human trophoblasts to either standard culture conditions (O(2) = 20%) or to static or alternating levels of oxygen (O(2) = 8%, or O(2) = 0%) either early or late in culture, and analyzed the expression of 34 genes that are known to be regulated in placentas from pregnancies complicated by fetal growth restriction (FGR).

RESULTS

Using multidimensional scale analysis, Euclidean distance, and hierarchical clustering, we found that gene expression patterns in cells exposed to O(2) = 8% were similar to patterns observed in O(2) = 20%, but more distant from patterns in O(2) = 0%. Alternating atmospheric oxygen (8% vs. 0%) yielded intermediate results. Changes in oxygen levels over a longer period had a greater effect on gene expression than short-term changes. Gene expression patterns in cultured trophoblasts did not fully capture expression patterns observed in biopsies from FGR placentas vs. control.

CONCLUSIONS

The level, duration, and patterns of hypoxia are critical in determining trophoblast gene expression, and therefore germane for analysis of trophoblast hypoxic injury.

Altered mitochondrial apoptotic pathway in placentas from undernourished rat gestations

Maternal undernutrition (MUN) during pregnancy results in intrauterine growth-restricted (IUGR) fetuses and small placentas. Although reduced fetal nutrient supply has been presumed to be etiologic in IUGR, MUN-induced placental dysfunction may occur prior to detectable fetal growth restriction. Placental growth impairment may result from apoptosis signaled by mitochondria in response to reduced energy substrate. Therefore, we sought to determine the presence of mitochondrial-induced apoptosis under MUN and ad libitum diet (AdLib) pregnancies. Pregnant rats were fed an AdLib or a 50% MUN diet from embryonic day 10 (E10) to E20. At E20, fetuses and placentas from proximal- and mid-horns (extremes of nutrient/oxygen supply) were collected. Right-horn placentas were used to quantify apoptosis. Corresponding left-horn placentas were separated into basal (hormone production) and labyrinth (feto-maternal exchange) zones, and protein expression of the mitochondrial pathway was determined. Our results show that the MUN placentas had significantly increased apoptosis, with lower expression of cytosolic and mitochondrial anti-apoptotic Bcl2 and Bcl-X(L), and significantly higher expression of pro-apoptotic Bax and Bak especially in the labyrinth zone. This was paralleled by higher coimmunostaining with the mitochondrial marker manganese superoxide dismutase (MnSOD), indicating transition of pro-apoptotic factors to the mitochondrial membrane. Also, cytosolic cytochrome c and activated caspases-9 and -3 were significantly higher in all MUN. Conversely, peroxisome proliferator-activator receptor-γ (PPARγ), a member of the nuclear receptor family with anti-apoptotic properties, was significantly downregulated in both zones and horns. Our results suggest that MUN during rat pregnancy enhances mitochondria-dependent apoptosis in the placenta, probably due to the downregulation of PPARγ expression.

Intra-uterine growth restriction is associated with increased apoptosis and altered expression of proteins in the p53 pathway in villous trophoblast

Intrauterine growth restriction (IUGR) affects 3-8% of pregnancies and is associated with altered cell turnover in the villous trophoblast, an essential functional cell type of the human placenta. The intrinsic pathway of apoptosis, particularly p53, is important in regulating placental cell turnover in response to damage. We hypothesised that expression of proteins in the p53 pathway in placental tissue would be altered in IUGR. Expression of constituents of the p53 pathway was assessed using real-time PCR, Western blotting and immunohistochemistry. p53 mRNA and protein expression was increased in IUGR, which localised to the syncytiotrophoblast. Similar changes were noted in p21 and Bax expression. There was no change in the expression of Mdm2, Bak and Bcl-2. The association between altered trophoblast cell turnover in IUGR and increased p53 expression is reminiscent of that following exposure to hypoxia. These observations provide further insight into the potential pathogenesis of IUGR. Further research is required to elicit the role and interactions of p53 and its place in the pathogenesis of IUGR.

Comparative gene expression profiling of placentas from patients with severe pre-eclampsia and unexplained fetal growth restriction

BACKGROUND

It has been well documented that pre-eclampsia and unexplained fetal growth restriction (FGR) have a common etiological background, but little is known about their linkage at the molecular level. The aim of this study was to further investigate the mechanisms underlying pre-eclampsia and unexplained FGR.

METHODS

We analyzed differentially expressed genes in placental tissue from severe pre-eclamptic pregnancies (n = 8) and normotensive pregnancies with or (n = 8) without FGR (n = 8) using a microarray method.

RESULTS

A subset of the FGR samples showed a high correlation coefficient overall in the microarray data from the pre-eclampsia samples. Many genes that are known to be up-regulated in pre-eclampsia are also up-regulated in FGR, including the anti-angiogenic factors, FLT1 and ENG, believed to be associated with the onset of maternal symptoms of pre-eclampsia. A total of 62 genes were found to be differentially expressed in both disorders. However, gene set enrichment analysis for these differentially expressed genes further revealed higher expression of TP53-downstream genes in pre-eclampsia compared with FGR. TP53-downstream apoptosis-related genes, such as BCL6 and BAX, were found to be significantly more up-regulated in pre-eclampsia than in FGR, although the caspases are expressed at equivalent levels.

CONCLUSIONS

Our current data indicate a common pathophysiology for FGR and pre-eclampsia, leading to an up-regulation of placental anti-angiogenic factors. However, our findings also suggest that it may possibly be the excretion of these factors into the maternal circulation through the TP53-mediated early-stage apoptosis of trophoblasts that leads to the maternal symptoms of pre-eclampsia.

Placental dysfunction and fetal programming: the importance of placental size, shape, histopathology, and molecular composition

Normal function of the placenta is pivotal for optimal fetal growth and development. Fetal programming commonly is associated with placental dysfunction that predisposes to obstetric complications and suboptimal fetal outcomes. We consider several clinical phenotypes for placental dysfunction that likely predispose to fetal programming. Some of these reflect abnormal development of the chorioallantoic placenta in size, shape, or histopathology. Others result when exogenous stressors in the maternal environment combine with maladaptation of the placental response to yield small placentas with limited reserve, as typical of early-onset intrauterine growth restriction and preeclampsia. Still others reflect epigenetic changes, including altered expression of imprinted genes, altered enzymatic activity, or altered efficiencies in nutrient transport. Although the human placenta is a transient organ that persists only 9 months, the effects of this organ on the offspring remain for a lifetime.

Apoptosis and proliferation in first trimester trophoblast of further complicated and uncomplicated pregnancies related to maternal serum screening markers

INTRODUCTION

Differences in proliferation and apoptosis in term trophoblast as well as maternal serum markers (MSM) for Down's syndrome in early pregnancy are related to adverse pregnancy outcomes. We investigated proliferation and apoptosis in first trimester chorionic villous sampling (CVS) as well as MSM and related these to pregnancy outcome.

MATERIALS AND METHODS

We selected 51 samples of first trimester chorionic villi of pregnancies later complicated by hypertensive disorders (HD) (n=36) and intra-uterine growth restriction (IUGR) (n=15) with matched controls. Immunohistochemistry (cleaved caspase-3 for apoptosis and MIB-1 for proliferation) was performed. Apoptosis- (AI) and proliferation-index (PI) were determined and proliferation-apoptosis index (PA) was calculated by PI/AI. First trimester serum screening (n=39), samples taken at the time of CVS (n=108) or regular second trimester serum screening samples (n=99) were examined.

RESULTS

The IUGR group compared to the hypertensive disorders group shows an increase of AI (p<0.05) and decrease in PA (p<0.03). Correlation is seen between PAPP-A and PI, AFP and AI and hCG and PA (all p<0.05).

CONCLUSION

Proliferation and apoptosis differ already in first trimester placentas of pregnancies complicated by hypertensive disorders or IUGR. Serum screening markers show correlation with proliferation and apoptosis and a subsequent adverse pregnancy outcome.

Peptidoglycan induces necrosis and regulates cytokine production in murine trophoblast stem cells

PROBLEM

Intrauterine bacterial infection during pregnancy may lead to adverse outcome. The objective of this study was to assess whether peptidoglycan (PGN) derived from Gram-positive bacteria induces trophoblast stem (TS) cell death or alters TS cell cytokine production.

METHOD OF STUDY

Toll-like receptor (TLR) transcript expression was assessed by RT-PCR. Protein expression was determined by confocal microscopy or flow cytometry. 7-Aminoactinomycin D (7-AAD) staining was used to assess TS cell death. Morphological features of cell death were evaluated by transmission electron microscopy. The presence of cleaved caspase-3 and high mobility group box 1 (HMGB1) protein was examined by Western blot. Cytokine levels in cell supernatants were determined using a mouse cytokine 23-plex panel.

RESULTS

Toll-like receptor 2 and TLR4 protein was expressed from the 1-cell stage through the blastocyst stage of murine embryo development. Murine TS cells expressed TLR2 and TLR6 but not TLR1 or TLR4 RNA. Only TLR2 protein was detected at the plasma membrane of TS cells. PGN induced TS cell death by a caspase-3-independent mechanism. The cell death pathway induced by PGN was morphologically consistent with necrosis. Finally, PGN induced HMGB1 release and increased MIP-1β secretion while inhibiting the constitutive release of RANTES.

CONCLUSION

Peptidoglycan-induced TS cell necrosis and the subsequent release of HMGB1 and MIP-1β may regulate an infection-induced inflammatory response at the maternal-fetal interface and thus may play a role in the pathogenesis of infection-associated pregnancy complications.

Toll-like receptors in pregnancy disorders and placental dysfunction

The Toll receptor was originally identified as a regulator of embryogenesis in Drosophila. Toll-like receptors (TLRs) in mammals recognize infectious agents and other danger signals. Activation of TLRs on trophoblast influences immune cell recruitment, cytokine secretion, and decidual responses to invading pathogens during pregnancy. Importantly, biological effects of TLR signal transduction at multiple maternal-fetal interfaces may contribute to several pregnancy pathologies associated with placental dysfunction, including pre-eclampsia, intrauterine growth restriction, and preterm labor. We herein discuss mechanisms by which TLRs regulate the maternal immune response during normal and abnormal gestation, and we highlight recent data that assign a role to TLRs in the pathophysiology of selected pregnancy-associated complications.

Obesity and the placenta: A consideration of nutrient exchange mechanisms in relation to aberrant fetal growth

The obesity epidemic, including childhood obesity, is rapidly gaining strength as one of the most significant challenges to the health of the global community in the 21st Century. The proportion of women who are obese at the beginning of pregnancy is also increasing. These women and their babies are at high risk of pregnancy complications, and of programming for metabolic disease in adult life. In particular, maternal obesity is associated with aberrant fetal growth, encompassing both growth restricted and large for gestational age, or macrosomic fetuses. This article considers the potential effect of obesity and adipose tissue on placental nutrient exchange mechanisms in relation to aberrant fetal growth. The review emphasizes the dearth of work on this topic to date despite its importance to current and future healthcare of the population.

Identifying placental dysfunction in women with reduced fetal movements can be used to predict patients at increased risk of pregnancy complications

Maternal perception of fetal movements has historically been used to indicate fetal wellbeing, and has been used with varying success in recent years to identify those pregnancies at increased risk of stillbirth, and other placental pathologies. We present a hypothesis that links reduced fetal movements (RFM) to fetal growth restriction (FGR) and stillbirth through placental dysfunction, and suggests the possibility that this can allow development of a reliable method to identify those women experiencing RFM who are at increased risk of adverse outcome. Reduced fetal movement is thought to represent fetal compensation in a chronic hypoxic environment due to inadequacies in the placental supply of oxygen and nutrients. Placental analysis in FGR and in stillbirth has revealed a number of structural abnormalities and an imbalance in cell turnover, and in terms of function, FGR is also associated with reduced nutrient transport. Both FGR and stillbirth are linked to changes in maternal levels of placental hormones. However, no such studies have been performed in samples from pregnancies affected by RFM. Currently, there are no formal guidelines to direct the management of such women, although it is recommended they undergo measurement of symphysis-fundal height and cardiotocography, and possibly Doppler ultrasound and biophysical profiling. Novel tests could involve the measurement of placental-derived hormones in maternal serum. To address this hypothesis, macroscopic and microscopic analysis of placental samples from both normal pregnancies and those affected by RFM is needed to detect any changes in structure. Placental function could be evaluated by levels of placental hormones in maternal blood. If placental dysfunction can be linked to RFM, and a robust method of identifying those women with placental insufficiency can be developed; screening patients with RFM could lead to a reduction in perinatal morbidity and mortality.

Hypoxia downregulates p53 but induces apoptosis and enhances expression of BAD in cultures of human syncytiotrophoblasts

Hypoxia is commonly assigned a role in the placental dysfunction characteristic of preeclampsia and intrauterine growth restriction. We previously showed that hypoxia upregulates p53 and enhances apoptosis in primary cultures of human cytotrophoblasts. Here we tested the hypothesis that hypoxia also induces apoptosis in syncytiotrophoblasts by upregulation of p53. Primary cultures of human cytotrophoblasts that had differentiated into syncytiotrophoblasts by 52 h were exposed for ≤24 h to 20% or <1% oxygen in the presence or absence of staurosporine or the p53 modulators nutlin-3, pifithrin-α, and pifithrin-μ. Proteins were detected by Western blot analysis or immunofluorescence. Compared with 20% oxygen, exposure of syncytiotrophoblasts to <1% oxygen upregulated hypoxia-inducible factor (HIF)-1α and rapidly downregulated p53. Activity of p53 in hypoxic syncytiotrophoblasts was reduced by the higher expression of the negative p53 regulator MDMX and by the reduction of phosphorylation of p53 at Ser(392), which reduces p53 activity. Conversely, staurosporine, a kinase inhibitor, and nutlin-3, a drug that enhances p53 expression, both raised p53 levels and increased the rate of apoptosis in syncytiotrophoblasts compared with vehicle controls. Immunofluorescence staining showed p53 immunolocalized to both cytoplasm and nuclei of nutlin-3-exposed syncytiotrophoblasts. The hypoxia-induced apoptosis in syncytiotrophoblasts correlated with enhanced expression of the proapoptotic BAD and a reduced level of antiapoptotic BAD phosphorylated on Ser(112). We surmise that cell death induced by extreme hypoxia in syncytiotrophoblasts follows a non-p53-dependent pathway, unlike that of a nonhypoxic stimulus and unlike hypoxic cytotrophoblasts. We speculate that downregulation of p53 activity in response to hypoxia reduces or eliminates the apoptosis transduced by the p53 pathway in syncytiotrophoblasts, thereby limiting cell death and maintaining the integrity of this critical villous component.

Placental apoptosis in health and disease

Apoptosis, programmed cell death, is an essential feature of normal placental development but is exaggerated in association with placental disease. Placental development relies upon effective implantation and invasion of the maternal decidua by the placental trophoblast. In normal pregnancy, trophoblast apoptosis increases with placental growth and advancing gestation. However, apoptosis is notably exaggerated in the pregnancy complications, hydatidiform mole, pre-eclampsia, and intrauterine growth restriction (IUGR). Placental apoptosis may be initiated by a variety of stimuli, including hypoxia and oxidative stress. In common with other cell-types, trophoblast apoptosis follows the extrinsic or intrinsic pathways culminating in the activation of caspases. In contrast, the formation of apoptotic bodies is less clearly identified, but postulated by some to involve the clustering of apoptotic nuclei and liberation of this material into the maternal circulation. In addition to promoting a favorable maternal immune response, the release of this placental-derived material is thought to provoke the endothelial dysfunction of pre-eclampsia. Widespread apoptosis of the syncytiotrophoblast may also impair trophoblast function leading to the reduction in nutrient transport seen in IUGR. A clearer understanding of placental apoptosis and its regulation may provide new insights into placental pathologies, potentially suggesting therapeutic targets.

Placental MRI in intrauterine fetal growth restriction

OBJECTIVE

Our objectives were to determine if MR imaging of the placenta could demonstrate a specific placental phenotype in small for gestational age fetuses with increasing severity of fetal growth restriction, and if MRI findings at the time of scan could be used to predict fetal or neonatal mortality.

METHOD

We included singleton growth restricted fetuses with increasing severity of fetal growth restriction secondary to placental insufficiency. 20 growth restricted fetuses and 28 normal fetuses were scanned once during pregnancy at varying gestations. MRI scans were performed on a 1.5T system using ssFSE sequences through the uterus. Data was collected on the severity of fetal growth restriction and pregnancy outcome, including clinical neonatal details, perinatal mortality, and birthweight and centile. Placental volume, maximal placental thickness, the placental thickness to volume ratio, the placenta to amniotic fluid signal intensity ratio, and the presence of abnormal signal intensity consistent with placental pathology were noted. In a subset of patients, histopathological diagnosis was compared with the MRI appearance of the placenta.

RESULTS

There was a significant increase in the placental volume affected by pathology in growth restricted fetuses (p < 0.001). The placental appearance was also thickened and globular, with an increase in the placental thickness to volume ratio (p < 0.001). Although placental volume increased with increasing gestation, it remained reduced in the growth restricted fetuses (p = 0.003). There was a significant correlation between the severity of fetal growth restriction and the placental volume affected by pathology, the placental thickness to volume ratio, and the placental volume. ROC analysis showed that fetal or neonatal death was predicted by the percentage of abnormal signal intensity consistent with placental pathology (p = 0.002). The presence of a thickened, globular placenta and a maximal placental thickness to volume ratio above the 95% confidence limit for gestation was significantly associated with an increased incidence of fetal or neonatal mortality (relative risk = 1.615, p = 0.001 and relative risk = 7, p < 0.001).

CONCLUSIONS

The MRI appearance of the placenta provides an indication of the severity and underlying disease process in fetal growth restriction. In units where MRI imaging of the growth restricted fetus occurs, we suggest that the assessment of the placenta should also occur as it may contribute to management decisions in cases at the threshold of viability. It may have a role to play in monitoring disease severity, and the effect of future interventions designed to improve placental function.

Beyond the threshold: an etiological bridge between hypoxia and immunity in preeclampsia

Taking a cue from the recent workshop 'Preeclampsia--a Pressing Problem' sponsored by the National Institutes of Child Health and Human Development, this review article takes a fresh look at hypoxia and a dysfunctional immune system as the key contributors to the etiology of preeclampsia and the mechanisms involved therein. In the context of epidemiological research on the intricate and multifactorial nature of preeclampsia, we focus on hypoxia as an upstream regulator of preeclampsia and its consequences in a model compromised by a deficiency in key pregnancy compatible immune modulators. It has been proposed that placental hypoxia releases cytotoxic factors produced at the maternal-fetal interface into the circulation to manifest the maternal symptoms associated with preeclampsia. However, it is not clear how this mechanism is empowered in pregnant women. Does systemic hypoxia exert preeclampsia-like effects on pregnancy? Are these effects further manifested by intrinsic inflammation in the absence of key immune modulators such as IL-10? Thus, it is of paramount importance that in vivo models be developed wherein the role of systemic hypoxia can be evaluated for preeclampsia-causing events. We present a discussion on whether prolonged exposure to hypoxia can lead to a perpetual cycle of compartmentalized uteroplacental tissue damage, release of anti-angiogenic and vasoconstrictive factors that impair trophoblast invasion and promote systemic vascular resistance resulting in the maternal syndrome.

Ets-2 and p53 mediate cAMP-induced MMP-2 expression, activity and trophoblast invasion

BACKGROUND

We have previously shown that Matrix metalloproteinase (MMP) -2 is a key-enzyme in early trophoblast invasion and that Protein Kinase A (PKA) increases MMP-2 expression and trophoblast invasion. The aim of this study was to examine MMP -2 regulation by PKA in invasive trophoblasts: JAR choriocarcinoma cell-line and 6-8 w first trimester trophoblasts.

METHODS

The effect of Forskolin (PKA) on MMP-2 expression was assessed by Northern Blot and RT-PCR. Possible transcription factors binding to consensus MMP-2 promoter sequences in response to Forskolin, were detected by EMSA binding assay and their expression assessed by western blot analysis. Antisense transfection of relevant transcription factors was performed and the inhibitory effect assessed on MMP-2 expression (RT-PCR), secretion (zymography) and trophoblast invasiveness (transwell migration assay).

RESULTS

We found that Forskolin increased MMP-2 mRNA in JAR cells within 24 hours, and induced binding to p53, Ets, C/EBP and AP-2. Transcription factors Ets-2, phospho- p53, C/EBP epsilon, C/EBP lambda and AP-2 alpha bound to their respective binding sequences in response to Forskolin and the expressions of these transcription factors were all elevated in Forskolin- treated cells. Inhibition of Ets-2 and p53 reduced MMP-2 expression, secretion and invasiveness of Forskolin treated cells.

CONCLUSION

MMP-2 is regulated by PKA through several binding sites and transcription factors including Ets-2, p53, C/EBP, C/EBP lambda and AP-2 alpha. Ets-2 and p53 mediate cAMP- induced trophoblast invasiveness, through regulation of MMP-2.

Novel approaches for mechanistic understanding and predicting preeclampsia

Despite intense investigation, preeclampsia (PE) remains largely enigmatic. Relatively late onset of diagnostic signs and heterogeneous nature of the disease further contribute to poor understanding of its etiology and clinical management. There exist no concrete animal models that can provide mechanistic underpinnings for evaluating targeted therapeutic intervention. Poor cross-sectional findings with potential biochemical markers reported so far have proved counterintuitive and suggest a need for novel approaches to predict the early onset of disease. Because of the co-onset of local placental anomalies and systemic manifestation of symptoms, it is highly likely that serum from PE patients can provide a "blueprint" of causative factors. Proteomic and/or functional analysis of maternal serum are expected to predict the onset of disease ahead of manifestation of clinical symptoms. A serum-based predictive assay should overcome complexities resulting from the heterogeneous etiology of PE. This review attempts to address some of these issues and discuss the signature biochemical serum factors and propose new and better ways to predict PE.

Role of the syncytium in placenta-mediated complications of preeclampsia

The syncytiotrophoblast (SCT) is the outer layer of placenta which is in direct contact with maternal blood. As such it is uniquely positioned to alter maternal hemostasis and endothelial function. The syncytium is known to release anti-angiogenic factors including fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), as well as the anti-fibrinolytic factor plasminogen activator inhibitor-1 (PAI-1). Its release of microparticles has also been suggested to play a role in regulating maternal endothelial and immune cell function. It is of note that syncytial release of the above-mentioned factors increases in preeclampsia, a major cause of maternal mortality and morbidity. In preeclampsia, hypoxia and reperfusion injury in the placenta is associated with activation of the maternal endothelium. In this review, I describe the interaction of syncytial factors with hypoxia, reactive oxygen species, and apoptosis in the pathophysiology of preeclampsia and intrauterine growth restriction. In addition, I detail the potential protective actions of placental ceruloplasmin in preeclampsia, recently described by our group to be a sensitive marker of syncytial hypoxia.

Intrauterine growth restriction, human placental development and trophoblast cell death

Intrauterine growth restriction (IUGR) is a failure to achieve the growth potential of a fetus that is promised by the genetic constitution and environmental influences endogenous to the pregnancy. Optimal placental development and the ability of the placenta to compensate for stimulus-induced injury are central in promotion of normal fetal growth. In this review, we will overview placental development with a focus on how villous structure relates to function. We will also describe the differentiation and turnover of villous trophoblast while highlighting selected features of microscopic placental injury. Histopathological studies of the placenta in IUGR indicate that abnormalities of the maternal spiral arterioles, dysregulated villous vasculogenesis, and abundant fibrin deposition are characteristic of the injuries associated with this condition. We identify selected insults, including oxidative stress and complement activation, and key pathways that regulate apoptosis in villous trophoblast, including increased p53 activity, altered translation of AKT and mTOR proteins, and the stress response of the endoplasmic reticulum. We surmise that trophoblast dysregulation at a subcellular level and loss of functional mass of villous trophoblast via cell death pathways are key contributors to the suboptimal placental performance that yields IUGR. We predict that a better understanding of placental dysfunction in IUGR will lead to targeted therapeutic options for this important clinical condition.