Endovascular trophoblast invasion: implications for the pathogenesis of intrauterine growth retardation and preeclampsia

Kisspeptins and the placenta: regulation of trophoblast invasion

The invasion of extravillous trophoblasts into the uterine wall is of crucial importance for placental and fetal development, and its dysregulation has been implicated in a wide spectrum of abnormal pregnancies. Mechanistically, trophoblast invasion strongly resembles the invasion of tumour cells, but differs from it by tight regulation in time and space. This regulation is accomplished by different factors including cytokines and hormones, which are produced by both fetal as well as maternal tissues i.e., placenta and uterus, respectively. Recently, products of the KiSS-1 gene (kisspeptins) have been identified to not only inhibit metastasis in various tumours, but also to repress trophoblast invasion via binding to the G protein-coupled receptor KiSS-1R. In the placenta, expression levels of kisspeptins and their receptor are highest in the first trimester in humans and at day 12.5 in rats, respectively. This coincides with the time when invasiveness peaks and invasion regulation is of central importance. Human kisspeptins are predominantly produced by the syncytiotrophoblast, whereas KiSS-1R is additionally expressed on the invading extravillous trophoblasts indicating a paracrine regulation of extravillous trophoblast invasion by the syncytiotrophoblast. In the structurally different rat placenta both KiSS-1 and its receptor are predominantly expressed by the invasive trophoblast giant cells, thus establishing an autocrine system in the invasion regulation of this trophoblast subpopulation. Amongst all kisspeptins the highly conserved kisspeptin Kp-10 has strongest invasion inhibiting effects suggesting its major role in regulation of trophoblast invasion.

Thrombin regulates monocyte chemoattractant protein-1 expression in human first trimester and term decidual cells

OBJECTIVE

Excess decidual macrophage infiltration has been linked to preeclampsia and a failure of endovascular trophoblast invasion. Severe preeclampsia with shallow placentation has also been linked to acquired and inherited maternal thrombophilias and recurrent decidual hemorrhage, which generates thrombin from decidual cell-expressed tissue factor. Therefore, the current study evaluated whether thrombin affects monocyte chemoattractant protein-1 (MCP-1) expression in stromal cells that are derived from cycling and gestational endometrium.

STUDY DESIGN

Stromal cells that are isolated from cycling endometrium and first trimester and term decidua were grown to confluence, treated for 7 days with 10(-8) mol/L estradiol (E2) + 10(-7) mol/L medroxyprogesterone acetate (MPA), then switched to a serum-free medium that contained the corresponding steroids +/- thrombin. MCP-1 protein release was measured by enzyme-linked immunosorbent assay and Western blot; MCP-1 messenger RNA levels were assessed by real-time quantitative reverse transcription-polymerase chain reaction.

RESULTS

Secreted MCP-1 levels were not significantly different in stromal or decidual cell cultures that were incubated with E2 or with E2 + MPA. Thrombin increased immunoreactive MCP-1 expression in a dose-response fashion in first trimester and term decidual cells but not in endometrial stromal cells. Thrombin-induced MCP-1 protein output was unaffected by MPA but was abrogated by incubation with the thrombin inhibitor, hirudin. Unexpectedly, thrombin-enhanced MCP-1 protein expression was unaccompanied by corresponding changes in steady state MCP-1 messenger RNA levels, which suggests its effects were posttranslational.

CONCLUSION

MCP-1 protein expression is up regulated by thrombin in decidual cells across gestation, but not in stromal cells from predecidualized cycling endometrium.

Gene expression profiling of the human maternal-fetal interface reveals dramatic changes between midgestation and term

Human placentation entails the remarkable integration of fetal and maternal cells into a single functional unit. In the basal plate region (the maternal-fetal interface) of the placenta, fetal cytotrophoblasts from the placenta invade the uterus and remodel the resident vasculature and avoid maternal immune rejection. Knowing the molecular bases for these unique cell-cell interactions is important for understanding how this specialized region functions during normal pregnancy with implications for tumor biology and transplantation immunology. Therefore, we undertook a global analysis of the gene expression profiles at the maternal-fetal interface. Basal plate biopsy specimens were obtained from 36 placentas (14-40 wk) at the conclusion of normal pregnancies. RNA was isolated, processed, and hybridized to HG-U133A&B Affymetrix GeneChips. Surprisingly, there was little change in gene expression during the 14- to 24-wk interval. In contrast, 418 genes were differentially expressed at term (37-40 wk) as compared with midgestation (14-24 wk). Subsequent analyses using quantitative PCR and immunolocalization approaches validated a portion of these results. Many of the differentially expressed genes are known in other contexts to be involved in differentiation, motility, transcription, immunity, angiogenesis, extracellular matrix dissolution, or lipid metabolism. One sixth were nonannotated or encoded hypothetical proteins. Modeling based on structural homology revealed potential functions for 31 of these proteins. These data provide a reference set for understanding the molecular components of the dialogue taking place between maternal and fetal cells in the basal plate as well as for future comparisons of alterations in this region that occur in obstetric complications.

Angiogenic growth factors in maternal and fetal serum in pregnancies complicated by intrauterine growth restriction

The present study was performed to compare serum concentrations of maternal and fetal angiogenic growth factors in IUGR (intrauterine growth restriction) and normal pregnancy at the time of delivery. VEGF (vascular endothelial growth factor), PlGF (placental growth factor), sFlt-1 (soluble fms-like tyrosine kinase 1), sKDR (soluble kinase domain receptor) and bFGF (basic fibroblast growth factor) were measured by ELISA in serum from a maternal peripheral vein, the umbilical vein and the umbilical arteries in 15 women with pregnancies complicated by IUGR and 16 controls (women with normal pregnancies). In IUGR, sFlt-1 was increased, and PlGF and sKDR were decreased, in both maternal serum and serum from the umbilical vein. Additionally, bFGF was increased in serum from the umbilical vein of women with pregnancies complicated by IUGR. No significant differences in growth factor concentrations between the groups were found in serum from the umbilical artery. In both groups, levels of VEGF were higher and levels of sFlt-1 were lower in serum from the umbilical vein and umbilical artery compared with maternal serum. PlGF levels were found to be lower in serum from the umbilical vein compared with maternal serum in both groups, whereas PlGF levels in serum from the umbilical artery were significantly lower only in the control group. These findings suggest an imbalance of angiogenic and anti-angiogenic factors in IUGR, with formation of an anti-angiogenic state in maternal and, to a lesser extent, umbilical vein blood. The placenta appears to play a central role in the release of sFlt-1 into maternal and umbilical blood. Umbilical artery blood was unaffected in IUGR, indicating that the fetus does not contribute to changes in angiogenic growth factor concentrations.

Screening for pre-eclampsia and fetal growth restriction by uterine artery Doppler and PAPP-A at 11-14 weeks' gestation

OBJECTIVE

To assess the role of maternal demographic characteristics, uterine artery Doppler velocimetry, maternal serum pregnancy-associated plasma protein-A (PAPP-A) and their combination in screening for pre-eclampsia and small-for-gestational age (SGA) fetuses at 11-14 weeks.

METHODS

This was a prospective study of 878 consecutive women presenting for a routine prenatal ultrasound examination at 11-14 weeks. Pulsed wave Doppler was then used to obtain uterine artery flow velocity waveforms and the mean pulsatility index (PI) of the uterine arteries was calculated. Maternal serum samples for PAPP-A were assayed. Along with maternal history, these measurements were compared in their ability to predict adverse outcome, defined as pre-eclampsia and/or SGA and/or placental abruption.

RESULTS

Mean uterine artery PI > or = 95(th) centile and PAPP-A < or = 10(th) centile each predicted 23% of the women that developed pre-eclampsia and 43% of cases of placental abruption. For SGA < or = 5(th) centile, mean uterine artery PI > or = 95(th) centile predicted 23% of cases and PAPP-A < or = 10(th) centile predicted 34%. Independent predictors for subsequent development of pre-eclampsia were increased mean uterine artery PI > or = 95(th) centile (OR, 2.76; 95% CI, 1.11-6.81) and maternal history of pre-eclampsia/hypertension (OR, 50.54; 95% CI, 10.52-242.73). The predicting factors for SGA < or = 5(th) centile were increased mean uterine artery PI > or = 95(th) centile (OR, 2.0; 95% CI, 1.07-3.74) and low PAPP-A (OR, 0.43; 95% CI, 0.20-0.93). Increased uterine artery PI was the only independent factor in the prediction of placental abruption (OR, 8.49; 95% CI, 2.78-25.94). The combination of uterine artery PI and maternal history of pre-eclampsia/hypertension was better than was using uterine artery Doppler alone in predicting pre-eclampsia. Similarly, for the prediction of SGA < or = 5(th) centile, combining uterine artery Doppler and maternal serum PAPP-A was better than was uterine artery Doppler alone. In both cases, the difference approached statistical significance.

CONCLUSIONS

The combination of maternal history with abnormal uterine artery Doppler and low PAPP-A level at 11-14 weeks achieves better results than does either test alone in the prediction of pre-eclampsia and SGA.

Paradoxical Discrepancy Between the Serum Level and the Placental Intensity of PP5/TFPI-2 in Preeclampsia and/or Intrauterine Growth Restriction: Possible Interaction and Correlation with Glypican-3 Hold the Key

There have been controversies whether maternal serum placental protein 5 (PP5)/tissue factor pathway inhibitor (TFPI)-2 is increased in the patients with preeclampsia and/or intrauterine growth restriction (IUGR). Here, we have estimated the serum PP5/TFPI-2 in these patients by a sandwich enzyme-linked immunosorbent assay with a newly developed monoclonal antibody, coupled with placental immunohistochemical studies of their placentae with semiquantitative scoring. Serum PP5/TFPI-2 level was significantly elevated only in the patients with preeclampsia alone (p=0.033), while PP5/TFPI-2 was detected significantly less intensely in the placentae of the same patients (p=0.035) in immunohistochemistry, as compared to Controls. A proteoglycan present on the placental villous surface, glypican-3, showed the same pattern of staining as PP5/TFPI-2, and there was a positive correlation (C.I.=0.506, p=0.004) between the immunohistochemical scores for these. Further experiments using HepG2 cells transfected with PP5/TFPI-2 suggested that glypican-3 could anchor PP5/TFPI-2 on the placental villi. A possibility that a decrease in glypican-3 in the placenta increases the outflow of PP5/TFPI-2, which in turn increases its serum level, was proposed. Preeclampsia and IUGR, often regarded to have the same pathological basis in common, showed distinct distributions of PP5/TFPI-2, which could be a clue to elucidate the pathogenesis of preeclampsia and IUGR.

Altered protease expression by periarterial trophoblast cells in severe early-onset preeclampsia with IUGR

Adaptation of uteroplacental arteries in patients with early-onset preeclampsia combined with IUGR is compromised due to insufficient invasion of extravillous trophoblast cells (EVT) into the spiral artery wall. The underlying molecular mechanisms are widely unknown. We investigated expression and possible mechanisms of regulation of different matrix-metalloproteases (MMPs) by EVT in placental bed biopsies from patients with early onset preeclampsia combined with IUGR and healthy pregnant women. Expression of MMP-3 and MMP-7 by EVT was markedly reduced in preeclamptic patients, especially close to spiral arteries. In contrast to healthy pregnancies these cells strongly expressed the receptor for leukemia inhibitory factor (LIF). LIF is known to suppress MMP-expression and is produced by uterine natural killer (uNK) cells which we found to be present in higher concentrations in the placental bed of preeclamptic patients, and accumulating aside the spiral arteries. We speculate that in preeclampsia a maternal immune cell network accumulating and interfering in the placental bed leads to an altered cytokine environment, resulting in disturbed trophoblast cell function such as impaired MMP expression and reduced invasiveness.

Proteomic analysis of proteins differentially expressed in preeclamptic trophoblasts

AIMS

To identify differential trophoblastic proteins associated with preeclampsia (PE) by proteomic analysis.

METHODS

We isolated and purified placental trophoblasts from normotensive pregnant women and patients with PE by a continuous Percoll gradient. The expression of proteins was determined by sliver staining after two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Proteins of interest were identified using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS).

RESULTS

The overall trophoblastic protein expression patterns in preeclamptic and corresponding normotensive placentas were quite similar except for some areas. Of 34 differentially expressed protein spots (p < 0.05 by paired t-test), seven differential proteins from nine spots were identified by MALDI-TOF-MS. The expression of the following proteins was repressed (p < 0.01): disulfide isomerase ER-60, peroxiredoxin 2, and Delta3,5-Delta2,4-dienoyl-CoA isomerase. Four proteins (protein disulfide isomerase precursor, endoplasmic reticulum resident protein, dihydrolipoyl dehydrogenase and TIM21-like protein) were found to be significantly upregulated in PE (p < 0.01).

CONCLUSION

We identified several proteins with significant altered expression in PE using 2D-PAGE. This method is a powerful technique with which to search for not only quantitative but also qualitative changes in a biological process of interest.

Hypoxia and placental remodelling

In the first trimester of pregnancy fetal trophoblast cells invade the maternal uterine spiral arteries leading to loss of the vascular cells from the vessel wall and remodelling of the extracellular matrix. This is crucial to ensure that sufficient blood can reach the developing fetus. Impaired arterial remodelling is a feature of the major pregnancy pathologies pre-eclampsia and fetal growth restriction. Despite its importance, little is known about the regulation of this process. We have shown, using in vitro culture models and ex vivo explant models, that trophoblast cells play an active role in remodelling spiral arteries, and have implicated apoptotic events in this process. Further we have shown that trophoblast-derived factors such as Fas-ligand, tumor necrosis factor-related apoptosis inducing ligand (TRAIL) are important regulators of this process. The oxygen tension within the uteroplacental environment will vary with gestational age and will depend on the extent of trophoblast invasion and artery remodelling. Fluctuations in oxygen tension may be an important determinant of cellular events both during invasion towards uterine vessels and during the remodelling process. The components of this process known to be regulated by oxygen are reviewed, including lessons that can be learned from pregnancies at high altitude. In addition, data on the effect of varying oxygen tension on trophoblast production of pro-apoptotic factors and susceptibility of vascular smooth muscle cells to induction of apoptosis are described.

Altered gene expression patterns in intrauterine growth restriction: potential role of hypoxia

OBJECTIVE

Placental insufficiency is a primary cause of intrauterine growth restriction (IUGR). In our study, microarray technology was used to identify genes, which may impair placentation resulting in IUGR.

STUDY DESIGN

The RNA was isolated from both IUGR term placentas and normal term placentas. Microarray experiments were used to identify differentially expressed genes between the 2 cohorts. Real-time quantitative reverse transcriptase polymerase chain reaction and immunohistochemistry were used in follow-up experiments.

RESULTS

Microarray experiments identified increased expression of certain genes including leptin, soluble vascular endothelial growth factor receptor, human chorionic gonadotropin, follistatin-like 3, and hypoxia-inducible factor 2alpha in the IUGR. Real-time quantitative polymerase chain reaction confirmed these results.

CONCLUSION

The upregulation of soluble vascular endothelial growth factor receptor and hypoxia-inducible factor 2alpha at this period in pregnancy indicate that placental angiogenesis is altered in IUGR and that hypoxia is a major contributor to maldevelopment of the placental vasculature.

Activated endothelial cells resist displacement by trophoblast in vitro

BACKGROUND

Transformation of the spiral arteries by invading trophoblasts is an essential prerequisite to the development of a healthy fully grown fetus. Reduced transformation of the spiral arteries is a characteristic feature of pregnancies complicated by several diseases of pregnancy including preeclampsia. The aim of this study was to investigate further the hypothesis that spiral artery endothelial cells can contribute to the mechanism of shallow trophoblast invasion.

METHOD

Fluorescently labeled Jar cells were added to monolayers of fluorescently-labeled endothelial cells that had been activated by treatment with TNFalpha, INF gamma or necrotic cell bodies. The ability of the Jars to displace endothelial cells from the monolayers was quantified by measuring the area of Jar cells "islands" formed in the endothelial cell monolayers by confocal microscopy and digital image.

RESULTS

The area of Jar cell islands formed in monolayers of activated endothelial cells was significantly smaller that the area of islands formed in control resting/non-activated endothelial cell monolayers regardless of the activator.

DISCUSSION

This work demonstrates that activated endothelial cells are more resistant to trophoblast displacement than resting endothelial cells and adds weight to the suggestion that endothelial cells could contribute to shallow invasion of the spiral arteries by trophoblasts in diseases such as preeclampsia.

Second trimester amniotic fluid endothelin-1 concentrations and subsequent development of intrauterine growth restriction

OBJECTIVE

The purpose of this prospective study was to record endothelin-1 (ET-1) concentrations in the second trimester amniotic fluid and compare these values in women who developed intrauterine growth restriction (IUGR) later in pregnancy with those with uneventful pregnancies.

METHOD

Amniotic fluid was retrieved by amniocentesis from 125 women in the second trimester of pregnancy. The levels of ET1 were measured by a sensitive and specific radioimmunoassay.

RESULTS

From the 125 women included in the study 12 had pregnancies that later developed IUGR and 88 had uneventful pregnancies. The ET1 concentration was significantly higher (P<0.005) in women who later developed IUGR than in normal pregnancy (106 pg/ml versus 64.7 pg/ml).

CONCLUSION

The amniotic fluid concentration of ET1 is elevated by the second trimester in women who later develop IUGR.

Expressional and epigenetic alterations of placental serine protease inhibitors: SERPINA3 is a potential marker of preeclampsia

Preeclampsia is the major pregnancy-induced hypertensive disorder. It modifies the expression profile of placental genes, including several serine protease inhibitors (SERPINs). The objective of this study was to perform a systematic expression analysis of these genes in normal and pathological placentas and to pinpoint epigenetic alterations inside their promoter regions. Expression of 18 placental SERPINs was analyzed by quantitative RT-PCR on placentas from pregnancies complicated by preeclampsia, intrauterine growth restriction, or both and was compared with normal controls. SERPINA3, A5, A8, B2, B5, and B7 presented significant differences in expression in >or=1 pathological situation. In parallel, the methylation status of the CpG islands located in their promoter regions was studied on a sample of control and preeclamptic placentas. Ten SERPIN promoters were either totally methylated or totally unmethylated, whereas SERPINA3, A5, and A8 presented complex methylation profiles. For SERPINA3, the analysis was extended to 81 samples and performed by pyrosequencing. For the SERPINA3 CpG island, the average methylation level was significantly diminished in preeclampsia and growth restriction. The hypomethylated CpGs were situated at putative binding sites for developmental and stress response (hypoxia and inflammation) factors. Our results provide one of the first observations of a specific epigenetic alteration in human placental diseases and provide new potential markers for an early diagnosis.

Expression of Estrogen Receptor-α, Estrogen Receptor-β and Placental Endothelial and Inducible NO Synthase in Intrauterine Growth-Restricted and Normal Placentas

BACKGROUND

Nitric oxide seems to play important roles in the physiology of placental blood circulation, although their expression in pathological placentas and their role is still unclear. Therefore, the aim of this study was to investigate the expression of estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta) and the endothelial NO synthase (eNOS) and inducible NO synthase (iNOS) in intrauterine growth-restricted (IUGR) placentas, hemolysis, elevated liver enzymes, low platelets (HELLP) placentas and in normal healthy control placentas.

METHODS

Slides of paraffin-embedded placental tissue were obtained after delivery from patients diagnosed with IUGR, HELLP and normal term placentas and analyzed for eNOS and iNOS, as well as ERalpha/beta expression. Intensity of immunohistochemical reaction was analyzed using a semi-quantitative score, and statistical analysis was performed. In addition, Western blot experiments were performed for comparison of staining intensities obtained by immunohistochemistry and Western blot.

RESULTS

Expression of eNOS and iNOS is significantly reduced in trophoblast cells of placentas with HELLP. However, ERbeta expression in HELLP placentas demonstrated a significantly elevated expression intensity compared to normal controls. ERalpha expression was not significantly different in all three pathologies investigated.

CONCLUSIONS

We speculate that the increased ERbeta expression in both syncytiotrophoblast and extravillous trophoblast cells represents accelerated proliferation of placental tissue or can be seen as a compensatory effect in HELLP placentas.

Lack of site-specific production of decidual alpha-2 macroglobulin in human pregnancy

BACKGROUND

Alpha-2 Macroglobulin (A2M) is a protease inhibitor that is present in both human and rat decidual tissue. In mice, decidual A2M prevents excessive trophoblastic invasion; however, its role in human decidual tissue is unknown. It is possible that A2M may also influence trophoblast invasion in human pregnancy, which would be reflected in increased A2M production in decidua basalis. The aim of the current study was to determine and compare A2M production from first trimester human decidua basalis and decidua parietalis.

METHODS

Human decidual tissues were obtained from patients undergoing surgical termination at 9 to 12 gestational weeks. Strips of decidua basalis and decidua parietalis were obtained by uterine curettage under real-time ultrasound guidance. Tissue samples were fixed in 10% formalin or snap-frozen for immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, respectively. Protein and mRNA production between the two sites were compared using the Mann-Whitney U test.

RESULTS

Paired basal and parietal decidua were analyzed by immunohistochemistry (n = 9) and by RT-PCR (n = 10). There was no significant difference in A2M mRNA expression between decidua basalis and decidua parietalis (P = .5). Immunohistochemical staining intensity for A2M protein was significantly higher in basalis than in parietalis (P = .004), but the extent of positively stained cells were not significantly different (P = .051). Strong A2M staining in decidua basalis was mainly localized in the intracellular storage vesicles, which may suggest a role of A2M in this site.

CONCLUSIONS

We conclude that the expression pattern of A2M in human decidua basalis and decidua parietalis is not consistent with an important role of this gene during the observed gestational period. Contrary to its role in rodent implantation, A2M is probably not involved in regulating human implantation and trophoblastic invasion during this gestational window frame.

Doppler sonography of the uterine and the cubital arteries in normal pregnancies, preeclampsia and intrauterine growth restriction: evidence for a systemic vessel involvement

AIMS

The decrease in uterine resistance during normal pregnancy is known to be related to invading trophoblast cells which derive from placental tissue. Uterine and peripheral resistance is elevated in preeclampsia. The aim of the present study was to prospectively examine uterine and peripheral resistance in pregnancies complicated by preeclampsia (PE), fetal intrauterine growth restriction (IUGR) and pregnancy induced hypertension (PIH).

METHODS

Sixty-seven women with normal pregnancies, 17 with PE, 12 with IUGR underwent Doppler sonographic investigation of the uterine and the cubital arteries. The Pulsatility Index (PI) was calculated for each vessel. Statistical analysis was performed and a P-value <0.05 was considered significant.

RESULTS

Patients with preeclampsia and IUGR showed a significant higher resistance at the placental (mean PI 1.267 and 1.063), nonplacental (mean PI 1.631 and 1.124) and cubital artery (mean PI 3,777 and 3.995) compared to the normal pregnancy group (mean PI 0.678; 0.859 and 2.95 respectively). Mean birth weight in the PE group was 1409 g, in the IUGR group 1649 g and 3419 g in the normal pregnancy group.

CONCLUSIONS

Pregnancies with IUGR are associated with elevated peripheral resistance in the maternal arterial system as seen in pregnancies with preeclampsia. Our findings encourage to further investigate the maternal vascular system in high risk pregnancies.

Severe feto-placental abnormalities precede the onset of hypertension and proteinuria in a mouse model of preeclampsia

Preeclampsia is a prevalent and potentially devastating disorder of pregnancy. Characterized by a sudden spike in blood pressure and urinary protein levels, it is associated with significant obstetric complications. BPH/5 is an inbred mouse model of preeclampsia with borderline hypertension before pregnancy. BPH/5 mice develop hypertension, proteinuria, and endothelial dysfunction during late gestation (after E14.5). We hypothesized that BPH/5 mice might exhibit early feto-placental abnormalities before the onset of maternal disease. All placental cell lineages were present in BPH/5 mice. However, the fetal and placental weights were reduced, with abnormalities in all the placental zones observed starting early in gestation (E9.5-E12.5). The fractional area occupied by the junctional zone was significantly reduced at all gestational timepoints. Markedly fewer CDKN1C-stained trophoblasts were seen invading the proximal decidual zone, and this was accompanied by reductions in Cdkn1c gene expression. Trophoblast giant cell morphology and cytokeratin staining were not altered, although the mRNA levels of several giant cell-specific markers were significantly downregulated. The labyrinth layer displayed decreased branching morphogenesis of endothelial cells, with electron microscopy evidence of attenuated trophoblast layers. The maternal decidual arteries showed increased wall-to-lumen ratios with persistence of actin-positive smooth muscle cells. These changes translated into dramatically increased vascular resistance in the uterine arteries, as measured by pulse-wave Doppler. Collectively, these results support the hypothesis that defects at the maternal-fetal interface are primary causal events in preeclampsia, and further suggest the BPH/5 model is important for investigations of the underlying pathogenic mechanisms in preeclampsia.

Differential Expression of the Receptor Tyrosine Kinase EphB4 and Its Ligand Ephrin-B2 During Human Placental Development

Normal placentation involves the development of an utero-placental circulation following the migration of the extravillous cytotrophoblasts into the decidua and invasion of the spiral arteries, which are thereby transformed into large vessels of low resistance. Given the documented role of the receptor tyrosine kinase EphB4 and its ligand ephrin-B2 in the establishment of the embryonal vascular network, we hypothesized that these molecules are also instrumental in the development of the human placenta. Monitoring the expression during placental development revealed that in first trimester and term placentae both molecules are equally expressed at the RNA level. In contrast, the protein levels were significantly reduced during gestation. Immunohistochemistry revealed a distinct localization of the EphB4 and ephrin-B2 proteins. EphB4 was predominantly expressed in the villous syncytial trophoblast layer and in a subset of intravillous capillaries. Prominent expression was also observed in the extravillous cytotrophoblast giant cells. In contrast, ephrin-B2 expression was detected in the villous cytotrophoblast and syncytial trophoblast cell layers, as well as initially in all intravillous capillaries. Strong expression was also observed in extravillous anchoring cytotrophoblast cells. Hypoxia is a major inducer of placental development. In vitro studies employing trophoblast-derived cell lines revealed that predominantly ephrin-B2 expression is induced by hypoxia, however, in an Hif-1alpha independent manner. These experiments suggest that EphB4 and ephrin-B2 are instrumental in the establishment of a functional placental structure and of the utero-placental circulation.

The Uterine Spiral Arteries In Human Pregnancy: Facts and Controversies

Uterine spiral arteries play a vital role in supplying nutrients to the placenta and fetus, and for this purpose they are remodelled into highly dilated vessels by the action of invading trophoblast (physiological change). Knowledge of the mechanisms of these changes is relevant for a better understanding of pre-eclampsia and other pregnancy complications which show incomplete spiral artery remodelling. Controversies still abound concerning different steps in these physiological changes, and several of these disagreements are highlighted in this review, thereby suggesting directions for further research. First, a better definition of the degree of decidua- versus trophoblast-associated remodelling may help to devise a more adequate terminology. Other contestable issues are the vascular plugging and its relation with oxygen, trophoblast invasion from the outside or the inside of the vessels (intravasation versus extravasation), the impact of haemodynamics on endovascular migration, the replacement of arterial components by trophoblast, maternal tissue repair mechanisms and the role of uterine natural killer (NK) cells. Several of these features may be disturbed in complicated pregnancies, including the early decidua-associated vascular remodelling, vascular plugging and haemodynamics. The hyperinflammatory condition of pre-eclampsia may be responsible for vasculopathies such as acute atherosis, although the overall impact of such lesions on placental function is far from clear. Several features of the human placental bed are mirrored by processes in other species with haemochorial placentation, and studying such models may help to illuminate poorly understood aspects of human placentation.

Plasma granulysin concentrations and preeclampsia risk

OBJECTIVE

Epidemiological, clinical and histological data suggest intriguing similarities between preeclampsia and graft-host-rejection. Granulysin, a novel biomarker of overall cellular immunity, is secreted by natural killer cells and cytotoxic T lymphocytes, which are associated with graft-host-rejection. Plasma granulysin was elevated in Japanese preeclamptic women.

DESIGN AND METHODS

50 preeclampsia cases and 50 normotensive controls (USA) were studied. Plasma granulysin at delivery was determined using enzyme immunoassay. Logistic regression procedures were used to estimate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Granulysin were elevated in preeclampsia cases compared with controls (3.01+/-0.18 vs. 2.22+/-0.14 ng/mL, p<0.01). After adjusting for age, body-mass-index and race, women with higher granulysin concentrations (> or =1.89 ng/mL) experienced a 2.9-fold (95%CI 1.1-7.8) increased preeclampsia risk compared with women with lower granulysin (<1.89 ng/mL).

CONCLUSIONS

These data offer further evidence of a predominant Th1 immune status associated with preeclampsia. Prospective studies are needed to determine whether granulysin is elevated early in pregnancy.

Circulating Angiogenic Factors and Placental Abruption

OBJECTIVE

Abnormalities in circulating angiogenic factors have been reported in diseases of abnormal placentation, such as preeclampsia and intrauterine growth restriction. Our objective was to determine whether circulating angiogenic factors are altered in another placental vascular disease, abruptio placentae.

METHODS

In a nested case-control study of nulliparous pregnancies, we examined levels of placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1) in serum collected prospectively from 31 women who later developed placental abruption and from 31 normal control subjects. All serum specimens were collected before the onset of hypertension or abruption and before labor or delivery. Serum angiogenic factors were compared within 3 gestational age windows: early (20 weeks or less), middle (21-32 weeks), and late (33 weeks or more) pregnancy.

RESULTS

During early pregnancy women who developed placental abruption had lower PlGF and higher sFlt-1 concentrations and higher sFlt-1/PlGF ratios than women with normal pregnancies. In mid-pregnancy these differences became greater, reaching statistical significance for PlGF concentration (431 versus 654 pg/mL, P<.01) and the sFlt-1/PlGF ratio (25.3 versus 2.5, P<.01). When the women with placental abruption were subdivided into those who did (n=10) and those who did not (n=21) develop preeclampsia or gestational hypertension, significant alterations in angiogenic factors were noted only in women who later developed hypertension in pregnancy. Among these women, PlGF concentrations were decreased in mid-pregnancy (160 versus 723 pg/mL, P<.001), and the mid-pregnancy sFlt-1/PlGF ratio was increased (70.1 versus 2.3, P=.001).

CONCLUSION

Serum levels of the proangiogenic factor PlGF were decreased, and those of the antiangiogenic ratio sFlt-1/PlGF were increased in nulliparous women who subsequently developed hypertension and placental abruption.

Apoptosis and its role in the trophoblast

During early placentation the trophoblast of the human placenta differentiates to the villous and extravillous types of trophoblast. Villous trophoblast provides the epithelial cover of the placental villous trees in direct contact to maternal blood. Extravillous trophoblast invades maternal uterine tissues thus directly contacting maternal stromal and immune cells. A subset of extravillous trophoblast, endovascular trophoblast initially occludes the lumen of spiral arteries and comes into direct contact with maternal blood. In recent years apoptosis has been described in both types of trophoblast and the importance of this cascade for the normal function of the trophoblast has become obvious. One feature of serious conditions such as preeclampsia or intrauterine growth restriction is changes in apoptosis regulation in villous and/or extravillous trophoblast resulting in altered trophoblast invasion and/or shedding into the maternal circulation. This review summarizes recent findings on trophoblast apoptosis in normal and pathologic pregnancies.

Shared and disparate components of the pathophysiologies of fetal growth restriction and preeclampsia

Intrauterine growth restriction (IUGR) and preeclampsia differ in their association with maternal disease but share a similar placental pathology. Moreover, mothers who have had pregnancies complicated by preeclampsia or IUGR are at elevated later-life cardiovascular risk. Why, then, do some women develop IUGR and others develop preeclampsia? In this clinical opinion, based on a review of the literature, we hypothesize that both women experiencing preeclampsia and IUGR enter pregnancy with some degree of endothelial dysfunction, a lesion that predisposes to shallow placentation. In our opinion, preeclampsia develops when abnormal placentation, through the mediator of elevated circulating cytokines, interacts with maternal metabolic syndrome, comprised of adiposity, insulin resistance/hyperglycemia, hyperlipidemia, and coagulopathy. IUGR develops in the absence of antenatal metabolic syndrome. Among these women, the baby is affected by shallow placentation but the mother does not develop clinically apparent disease. This conceptualization provides a testable framework for future etiologic studies of preeclampsia and IUGR.

Contrast Sonography, Video Densitometry and Intervillous Blood Flow: A Pilot Project

PURPOSE

To examine the feasibility of constructing time-intensity (TI) curves from the intervillous space with an intravascular ultrasound contrast agent and computer assisted video densitometry.

STUDY DESIGN

We sedated nine pregnant baboons, optimized the grey scale and color Doppler images of their placentas, and then fixed the transducers in place. For each injection of contrast, we recorded images on videotape without changing the ultrasound image processing functions. Video images were captured using a Macintosh personal computer equipped with a video-capture board using image analysis software (Image 1.4, W Rasband, NIH). For each injection, we sampled digitized images of a fixed region of interest at regular intervals. After computing the mean video density of each image, we used the sampling frequency to construct TI curves depicting any change over time as the contrast agents washed into and out of the intervillous space.

RESULTS

Three of four agents tested produced changes in the video density of the placenta. TI curves were established using both grey scale and color Doppler signal augmentation. As expected, intra-arterial agents produced rapid accumulation and decay. Intravenous agents produced more protracted effects secondary to bolus dilution and transit through the right heart and pulmonary vascular bed.

CONCLUSION

TI curves may be generated from the intervillous space with the use of a transpulmonary ultrasound contrast agent and video densitometry. If validated by further study, this may allow investigators to apply ultrasound and indicator-dilution theory to intervillous blood flow.

Ultrasound detection of placental insufficiency in women with 'unexplained' abnormal maternal serum screening results

Serious placental insufficiency results in perinatal death or preterm birth from ischemic-thrombotic pathology, a process which has its origins in placental maldevelopment in the first trimester. A proportion of at-risk pregnancies may be identified from abnormalities in first or second trimester serum screening data, uterine artery Doppler waveforms or placental shape and texture at the time of the 18-20-week anatomical examination. In combination, these tests may be capable of recognizing a subset of at-risk pregnancies with 50% positive predictive values. Early recognition before fetal viability affords opportunities to direct women to regional perinatal care centres for enhanced maternal-fetal surveillance, corticosteroids to enhance fetal lung maturation, prophylactic measures to prevent pre-eclampsia and optimal decision making around the time of delivery. The creation of regional screening programs to use screening data with a placental focus is likely to be cost-effective, because existing patterns of care are utilized. More importantly, this strategy can direct women to participate in clinical research programs designed to reduce morbidity and mortality from this common group of conditions.

Hormonal regulation of placental nitric oxide and pathogenesis of pre-eclampsia

The placenta is central to foetal growth and development in mammalian pregnancy. Compromised placental function (as found in pre-eclampsia) often results in life-threatening situations for both mother and foetus. The nitric-oxide (NO) signalling cascade is important for placental function, in particular for the development of the vascular network and for maintaining vascular tone. This pathway seems to be regulated by multiple hormonal signals. Emerging evidence suggests that pathogenic mechanisms that are involved in abnormal placental function target specific molecules, such as hormone receptors, that regulate NO release and have subsequent dramatic consequences. Here, we discuss the current knowledge of NO function in the placenta, its hormonal regulation in normal pregnancy and in the pathophysiology of pre-eclampsia, its potential pathogenic mechanisms and possible use as a therapeutic target.

Human chorionic gonadotropin expression in human trophoblasts from early placenta: comparative study between villous and extravillous trophoblastic cells

Human trophoblast differentiates into two pathways: extravillous cytotrophoblasts (EVCT) that invade the uterus wall and villous cytotrophoblasts (VCT) that fuse to form the syncytiotrophoblast (ST) involved in placental exchanges and endocrine function. It is established that hCG is produced and secreted by the ST into the maternal compartment where it plays a key endocrine role and stimulates ST formation in an autocrine manner. Herein, we investigated hCG expression in early placentas by immunohistochemistry using different antibodies. We then compared hCG secretion by primary cultures of VCT and EVCT isolated from the same first trimester human chorionic villi. In situ hCG was immunodetected in EVCT all along their invasive differentiating pathway except in cells near the stromal core of the proximal column. hCG expression was confirmed in vitro by immunocytochemistry and hCG secretion quantified in cell supernatants. Interestingly, whereas hCG secretion increased during VCT differentiation into ST (from 60 to 350UI/L/microg DNA), EVCT secretion remained constant and at a high level during the same culture period (160UI/L/microg DNA). Our data demonstrated that in addition to the ST, invasive EVCT also expressed and secreted high levels of hCG, suggesting a specific paracrine and/or autocrine role for hCG from EVCT origin.

Suppression of Extravillous Trophoblast Invasion of Uterine Spiral Arteries by Estrogen During Early Baboon Pregnancy

The present study determined whether estrogen plays a role in regulating invasion and remodeling of the uterine spiral arteries by extravillous trophoblasts during early baboon pregnancy. The level of trophoblast invasion of spiral arteries was assessed on day 60 of gestation (term is 184 days) in baboons untreated or treated on days 25-59 with estradiol or aromatizable androstenedione. The administration of estradiol or androstenedione increased (P<0.01) maternal serum estradiol levels approximately 3-fold above normal. The mean+/-SE percentage of spiral arteries/arterioles invaded by extravillous cytotrophoblasts in estradiol-treated baboons for vessels with diameters of 26-50 microm (0.0+/-0.0), 51-100 microm (1.2+/-0.7) and >100 microm (13.2+/-5.5) was 100%, 90%, and 75% lower (P<0.001), respectively, than in untreated baboons (2.4+/-1.2%; 11.0+/-5.5%, and 54.5+/-8.5%, respectively). Similar results were obtained with androstenedione treatment. However, the distribution of uterine spiral arteries grouped by diameter or number of arteries per basal plate area, i.e. microvessel density, were similar in untreated and estrogen-treated baboons. We suggest, therefore, that the low levels of estrogen exhibited during early primate pregnancy are required to permit normal progression of trophoblast vascular invasion and that the surge in estrogen which occurs during the second-third of normal pregnancy has a physiological role in suppressing further arterial trophoblast invasion. Consequently, we propose that the estrogen-dependent restraint of spiral artery invasion/remodeling ensures optimal blood flow dynamics across the uteroplacental vascular bed to promote normal fetal growth and development.

Contractile cells and fibrillin-1 distribution is disturbed in terminal villi of placentae from patients with preeclampsia and systemic lupus erythematosus

Placentae from patients with preeclampsia (PE) and systemic lupus erythematosus (SLE) present many alterations that may impair materno-fetal exchange. We investigated the distribution of contractile cells and fibrillin-1 in terminal villi of term placentae from patients with PE or SLE and compared to control placentae. Stroma in terminal villi exhibited intense labelling for fibrillin-1. The fibrillin-1 villi surface fraction was greater in PE and SLE placentae than in controls (13+/-0.4%, 14+/-0.5%, 10+/-0.4%; p=0.0001). Immunohistochemistry for alpha-smooth muscle (SM) actin showed few contractile cells in control terminal villi stroma, localized around fetal capillaries and showed rare processes in vasculo-syncytial membrane. PE and SLE placentae exhibited an increase in the number of capillaries presenting alpha-SM actin adventitial positive cells. The presence of alpha-SM actin processes interposed in the vasculo-syncytial membrane was greater in SLE villi than in PE and controls. Ultrastructural observations confirmed in SLE and PE terminal villi the presence of these processes in vasculo-syncytial membrane and also showed a thickened trophoblastic basement membrane. The present study demonstrates that an important myofibroelastic system is present in term terminal villi, and that this system is actively remodelled in PE and SLE placentae.

Gene expression profiling of human placentas from preeclamptic and normotensive pregnancies

The aim of this study was to investigate patterns of gene expression in placental samples from patients with preeclampsia (PE), persistent bilateral uterine artery notching (without PE), and normal controls. This study included placental tissue from nine women with PE, seven with uncomplicated pregnancies and five with bilateral uterine artery notching in Doppler velocimetry tracings. Human cDNA microarrays with 6500 transcripts/genes were used and the results verified with real-time PCR and in-situ hybridization. Multidimensional scaling method and random permutation technique demonstrated significant differences among the three groups examined. Within the 6.5K arrays, 6198 elements were unique cDNA clones representing 5952 unique UniGenes and 5695 unique LocusLinks. Multidimensional scaling plots showed 5000 genes that met our quality criteria; among these, 366 genes were significantly different in at least one comparison. Differences in three genes of interest were confirmed with real-time PCR and in-situ hybridization; acid phosphatase 5 was shown to be overexpressed in PE samples and calmodulin 2 and v-rel reticuloendotheliosis viral oncogene homolog A (RELA) were downregulated in PE and uterine artery notch placentas. In conclusion downregulation of RELA and calmodulin 2 might represent an attempt by the placenta to compensate for elevations in intracellular calcium, possibly caused by hypoxia and/or apoptosis, in both pregnancies with uterine artery notching and preeclampsia.

Regulation of monocyte chemoattractant protein-1 expression by tumor necrosis factor-alpha and interleukin-1beta in first trimester human decidual cells: implications for preeclampsia

The current study describes a statistically significant increase in macrophages (CD68-positive cells) in the decidua of preeclamptic patients. To elucidate the regulation of this monocyte infiltration, expression of monocyte chemoattractant protein-1 (MCP-1) was assessed in leukocyte-free first trimester decidual cells. Confluent decidual cells were primed for 7 days in either estradiol or estradiol plus medroxyprogesterone acetate to mimic the decidualizing steroidal milieu of the luteal phase and early pregnancy. The medium was exchanged for a serum-free defined medium containing corresponding steroids +/- tumor necrosis factor (TNF)-alpha or interleukin (IL)-1beta. After 24 hours, enzyme-linked immunosorbent assay measurements indicated that the addition of medroxyprogesterone acetate did not affect MCP-1 output, whereas 10 ng/ml of TNF-alpha or IL-1beta increased output by 83.5-fold +/- 20.6 and 103.1-fold +/- 14.7, respectively (mean +/- SEM, n = 8, P < 0.05). Concentration-response comparisons revealed that even 0.01 ng/ml of TNF-alpha or IL-1beta elevated MCP-1 output by more than 15-fold. Western blotting confirmed the enzyme-linked immunosorbent assay results, and quantitative reverse transcriptase-polymerase chain reaction confirmed corresponding effects on MCP-1 mRNA levels. The current study demonstrates that TNF-alpha and IL-1beta enhance MCP-1 in first trimester decidua. This finding suggests a mechanism by which recruitment of excess macrophages to the decidua impairs endovascular trophoblast invasion, the primary placental defect of preeclampsia.

Placental expression of secreted frizzled related protein-4 in the rat and the impact of glucocorticoid-induced fetal and placental growth restriction

Wnt genes regulate a diverse range of developmental processes, including placental formation. Activation of the WNT pathway results in translocation of beta-catenin (CTNNB1) into the nucleus and the subsequent activation of transcription factors that promote proliferation. The secreted frizzled related proteins (SFRPs) are thought to inhibit WNT signaling by binding to the WNT ligand or its frizzled receptor. In this study, we compared the expression patterns of one of these secreted molecules, SFRP4, in the two morphologically and functionally distinct regions of the rat placenta during the last third of pregnancy. In addition, we assessed whether placental SFRP4 expression is altered in a model of glucocorticoid-induced placental growth restriction. Temporal analyses of the rat placenta by quantitative RT-PCR, in situ hybridization, and immunohistochemistry during the final third of pregnancy demonstrated elevated levels of Sfrp4 mRNA and SFRP4 protein near term, specifically in trophoblast cells of the basal zone. This increase in expression of SFRP4 in basal zone trophoblasts was associated with a reduction in CTNNB1 nuclear translocation, consistent with inhibition of the WNT pathway. Maternal dexamethasone treatment (1 microg/ml of drinking water, Days 13-22), which has previously been shown to reduce placental growth, further increased the expression of Sfrp4 mRNA in both the basal and labyrinth zones of the placenta at Day 22. Collectively, these data demonstrate that increased expression of SFRP4 is associated with reduced growth of placental regions in normal pregnancy and after glucocorticoid-induced growth retardation. These observations, together with associated changes in CTNNB1 localization, support the hypothesis that increased placental expression of SFRP4 inhibits the WNT pathway and thereby influences placental growth via effects on cell fate signaling.

Genetic polymorphisms of vascular endothelial growth factor in severe pre-eclampsia

Several lines of evidence support the hypothesis that vascular endothelial growth factor (VEGF) plays an important role in the pathogenesis of pre-eclampsia (PE). VEGF is a key component in the regulation of vascular remodelling and the survival of cytotrophoblasts in the placenta. In this case-control study, we aimed to test whether VEGF genetic polymorphisms are associated with the risk of severe PE. We enrolled 84 nulliparous pregnant women with severe PE (PE group). Their VEGF G(+405)C and VEGF C(-2578)A genotypes were determined by PCR-restriction fragment length polymorphism (PCR-RFLP) from venous blood samples and were compared with the corresponding VEGF genotypes of 96 nulliparous patients with uncomplicated pregnancies (control group). Carriers of the VEGF(+405)G allele occurred less frequently in PE than in the control group [P = 0.039; adjusted odds ratio (aOR) = 0.28, range: 0.08-0.93]. Hypertension and proteinuria were diagnosed earlier (by 1.6 weeks and 1.9 weeks, respectively) in PE patients with VEGF(-2578)A only after adjustment of this association for risk factors of PE. Our results suggest that carriers of VEGF(+405)G allele have a decreased susceptibility to PE and that the progression of PE may be modified by the presence of VEGF(-2578)A allele. Nevertheless, the clinical significance of these findings remains to be determined.

Microvessel density in the placental bed among preeclampsia patients

CONTEXT AND OBJECTIVE

Morphological changes in the spiral arteries of the placental bed have been studied in patients with preeclampsia, one of the largest causes of maternal and perinatal morbidity and mortality. The reports show that vasospasm and vascular endothelial injury were two major pathological conditions for preeclampsia. The aim of this study was to investigate the microvessel density of spiral arteries in the placental bed, in pregnancies complicated by hypertension and proteinuria, and in normal pregnancies.

DESIGN AND SETTING

This was a cross-sectional survey of immunohistochemical studies on biopsies from the spiral arteries of the placental bed, among women undergoing cesarean sections for clinical and obstetrical reasons at Universidade Federal de São Paulo, São Paulo, Brazil.

METHODS

Placental bed biopsies were obtained during cesarean section after placenta removal, with direct viewing of the central area of placenta insertion. The microvessel density of spiral arteries was measured by immunohistochemical methods in decidual and myometrial segments, using CD34 antibody.

RESULTS

Biopsies containing spiral arteries were obtained from 34 hypertensive pregnant women with proteinuria, and 26 normotensive pregnant women. The microvessel densities in decidual and myometrial segments of the placental bed were compared between the groups. It was observed that, with increasing blood pressure and proteinuria, the microvessel density gradually decreased.

CONCLUSION

The presence of high levels of hypertension and proteinuria may be associated with a progressive decrease in microvessel density in the placental bed.

Correlation of maternal serum high-sensitive C-reactive protein levels with biochemical and clinical parameters in preeclampsia

OBJECTIVE

To investigate the relationship between serum high sensitive C-reactive protein (hsCRP) levels and biochemical and clinical parameters in preeclampsia (PE).

STUDY DESIGN

This cross-sectional study included 20 women with PE and 20 healthy pregnant women. They were recruited in the third trimester of pregnancy at the Firat University, Firat Medical Center, Department of Obstetric and Gynaecology in Elazig province. The standard biochemical and hematological parameters were measured by an advanced auto analyzer. Venous blood samples were collected at admission to the hospital at least 6h before delivery for measurement of hsCRP by a high sensitive immunonephelometric method.

RESULTS

Hemoglobin, serum hsCRP, creatinine, aspartat and alanine transaminase, lactate dehydrogenase, blood urea nitrogen and urine protein excretion were higher, and serum calcium levels were lower in patients with PE compared to control group values. In the preeclampsia group, correlation analysis tests showed a strong positive correlation between serum hsCRP levels and diastolic blood pressures (r=0.9, p=0.05, n=20) and urinary protein excretion (r=0.8, p=0.05, n=20), and a negative correlation between serum hsCRP and weight (r=-0.6, p=0.02, n=20) and length (r=-0.5, p=0.05, n=20) of the newborns. Serum hsCRP levels were also negatively correlated with weights (r=0.5, p=0.02, n=20) and lengths (r=0.5, p=0.05, n=20) of the newborns in the control group.

CONCLUSIONS

Serum hsCRP levels increase in women with PE. Elevated serum levels of hsCRP in preeclamptic women are correlated with clinical and biochemical parameters of PE. Determination of serum hsCRP levels may be used as a marker for the severity of PE.

Divergent trophoblast invasion and apoptosis in placental bed spiral arteries from pregnancies complicated by maternal anemia and early-onset preeclampsia/intrauterine growth restriction

OBJECTIVE

Impaired trophoblast invasion into spiral arteries is associated with early-onset intrauterine growth restriction and preeclampsia. We compared trophoblast invasion into spiral arteries in pregnancies with maternal anemia or early-onset preeclampsia/intrauterine growth restriction and related these findings to trophoblast apoptosis.

STUDY DESIGN

Full-thickness uterine wall samples were obtained from women with early-onset preeclampsia/intrauterine growth restriction (n = 6), normal pregnancies (n = 5), and chronic anemia (n = 8). Trophoblast invasion into the walls of spiral arteries was quantified by morphometric analysis of paraffin sections stained with anticytokeratin 18, antiactin, and anticytokeratin 18 neoepitope (M30) antibodies.

RESULTS

Trophoblast invasion into spiral arteries was increased in anemic pregnancies (mean [SD]: 206 [46] cell profiles/mm2) and severely impaired in preeclamptic/intrauterine growth restriction pregnancies (17 [6]), compared with normal subjects (149 [52]). Spiral artery lumen area was increased in anemia (0.07 [0.03] mm2) versus normal pregnancies (0.09 [0.04] mm2) and reduced in preeclampsia/intrauterine growth restriction (0.04 [0.02] mm2). Trophoblast apoptosis was similar in anemic (4.2% [3.4%]) and normal (5.0% [1.9%]) pregnancies but increased in preeclampsia/intrauterine growth restriction (12% [5.6%]).

CONCLUSION

Trophoblast invasion into the placental bed in early-onset preeclampsia/intrauterine growth restriction is limited by increased apoptosis, resulting in narrower spiral arteries, which is in contrast to findings in anemia.

Placentation in the degu (Octodon degus): analogies with extrasubplacental trophoblast and human extravillous trophoblast

This study examined the placentation in the degu, the origin of the extrasubplacental trophoblast (EST) (extravillous trophoblast in human), and the activity of Na+/K+ ATPase in the placental barrier during different gestational ages, as part of a wider effort to understand the reproductive biology of this species. Fifteen degus at the first stage of gestation, midgestation and at term of pregnancy were studied. At day 27 of gestation, the subplacenta is formed under the wall of the central excavation. Simultaneously, the outermost trophoblast of the ectoplacental cone differentiated into secondary trophoblast giant cells that lie on the outside of the placenta, forming an interface with the maternal cells in the decidua. These giant cells immunostained positive for cytokeratin (CK) and placental lactogen (hPL) until term. During this period, the EST merged from the subplacenta to the decidua and immunostained negative for CK, but at term, immunostained for CK and hPL in the maternal vessels. The vascular mesenchyme of the central excavation invaded the chorioallantoic placenta during this period, forming two fetal lobules of labyrinthine-fine syncytium, the zone of the placental barrier. The activity of Na+/K+ ATPase in the placental barrier was constant during the gestational period. The residual syncytium at the periphery of the placental disc and between the lobules was not invaded by fetal mesenchyme and formed the marginal and interlobular labyrinthine syncytium that immunostained first for CK, and later for hPL, as in the labyrinthine fine syncytium. The presence of intracytoplasmic electron-dense material in the interlobular labyrinthine syncytium suggested a secretory process in these cells that are bathed in maternal blood. Placentas obtained from vaginal births presented a large, single lobe, absence of the subplacenta, and a reduced interlobular labyrinthine syncytium. At day 27, the inverted visceral yolk sac is observed and its columnar epithelium immunostained for CK and hPL. This suggests that the yolk sac is an early secretory organ. The epithelium of the parietal yolk sac covers the placenta. The origin of the EST in the degu placenta and its migration to maternal vessels allows us to present this animal model for the study of pregnancy pathologies related to alterations in the migration of the extravillous trophoblast.

Integrin-linked kinase (ILK) is highly expressed in first trimester human chorionic villi and regulates migration of a human cytotrophoblast-derived cell line

The placenta represents a critically important fetal-maternal interaction. Trophoblast migration and invasion into the uterine wall is a precisely controlled process and aberrations in these processes are implicated in diseases such as preeclampsia. Integrin-linked kinase (ILK) is a multifunctional, cytoplasmic, serine/threonine kinase that has been implicated in regulating processes such as cell proliferation, survival, migration, and invasion; yet the temporal and spatial pattern of expression of ILK in human chorionic villi and its role in early human placental development are completely unknown. We hypothesized that ILK would be expressed in trophoblast subtypes of human chorionic villi during early placental development and that it would regulate trophoblast migration. Immunoblot analysis revealed that ILK protein was highly detectable in placental tissue samples throughout gestation. In floating branches of chorionic villi, from 6 to 15 wk of gestation immunofluorescence analysis of ILK expression in placental tissue sections demonstrated that ILK was highly detectable in the cytoplasm and membranes of villous cytotrophoblast cells and in stromal mesenchyme, whereas it was barely detectable in the syncytiotrophoblast layer. In anchoring branches of villi, ILK was highly localized to plasma membranes of extravillous trophoblast cells. Transient expression of dominant negative E359K-ILK in the villous explant-derived trophoblast cell line HTR8-SVneo dramatically reduced migration into wounds compared to cells expressing wild-type ILK or empty vector. Therefore, our work has demonstrated that ILK is highly expressed in trophoblast subtypes of human chorionic villi during the first trimester of pregnancy and is a likely mediator of trophoblast migration during this period of development.

Stellate transformation of invasive trophoblast: a distinct phenotype of trophoblast that is involved in decidual vascular remodelling and controlled invasion during pregnancy

BACKGROUND

Successful implantation relies on the tightly regulated invasion of extravillous trophoblasts (EVTs). However, little is known about their phenotypic differentiation and relevant motile behaviour. Furthermore, the cell-cell interactions between EVTs and decidual arterioles during physiological transformation are also poorly understood.

METHODS

A total of 128 decidual specimens from early and late gestations containing components of EVTs and spiral arterioles were investigated using immunohistochemistry and periodic acid-Schiff reaction.

RESULTS

Unipolar, tadpole-like EVTs are observed throughout the interstitial area, with a tendency to decrease along the invasive pathway. The stellate differentiation of the EVTs is identified around and inside decidual arterioles or in the third-trimester myometrium. Furthermore, stellate transformation of EVTs precedes its interactions with the decidual arteriole. These specialized stellate trophoblasts invade and infiltrate the tunica media, accompanying lacuna formation inside the vessel wall and perturbation of actin fibre alignment of the tunica media.

CONCLUSION

Stellate transformation of trophoblasts may explain controlled invasion of EVTs and probably plays a key role in initiating cell-cell interaction in decidual vascular remodelling.

Placental Expression of Peroxisome Proliferator-Activated Receptors in Rat Pregnancy and the Effect of Increased Glucocorticoid Exposure1

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Recent gene deletion studies indicate that PPARG and PPARD play critical roles in rodent development, including effects on placental vascularization. In this study we investigated the expression of the PPAR isoforms and their heterodimeric partner, RXRA, in the two functionally and morphologically distinct zones of the rat placenta during normal gestation and after glucocorticoid-induced fetal and placental growth restriction. Real-time reverse transcription-polymerase chain reaction and immunohistochemical analysis demonstrated markedly higher expression of Ppara, Pparg, and Rxra mRNA in labyrinth zone trophoblast as compared with basal zone near term. There was also a marked increase in Pparg (65%, P < 0.05) and Ppara (91%, P < 0.05) mRNA specifically in the labyrinth zone over the final third of pregnancy. In contrast, expression of Ppard mRNA fell (P < 0.001) in both placental zones over the same period. Maternal dexamethasone treatment (1 mug/ml in drinking water; Days 13-22, term = 23 days) reduced placental (44%) and fetal (31%) weights and resulted in a fall in Pparg (37%, P < 0.05) mRNA expression specifically in the labyrinth zone at Day 22. Placental expression of Ppara, Ppard, and Rxra was unaffected by dexamethasone treatment. These data suggest that PPARG:RXRA heterodimers play important roles in labyrinth zone growth late in pregnancy, possibly supporting vascular development. Moreover, glucocorticoid inhibition of placental growth appears to be mediated, in part, via a labyrinth-zone-specific suppression of PPARG.

Maternal-Fetal Interactions in Fetal Cardiac Surgery

BACKGROUND

We examined potential maternal-fetal interactions during fetal cardiopulmonary bypass. these interactions, not previously described, may significantly influence attempts at fetal cardiac surgery.

METHODS

Eight fetal sheep underwent cardiopulmonary bypass (5 singletons, 3 twins; 100-109 days) for 60 minutes using a centrifugal microcircuit (20 mL prime), and the placenta as oxygenator. We measured maternal hemodynamics, arterial blood gases, and changes in blood flow to the gravid uterus using bilateral uterine artery flow probes. Maternal measurements were correlated to fetal hemodynamics, blood gases, and umbilical blood flows. After bypass, fetuses were followed for 60 minutes.

RESULTS

Decreases in uterine blood flow occurred without changes in maternal hemodynamics or arterial blood gases, but were associated with worsening fetal arterial blood gases (pH decreased from 7.2 +/- 0.2 to 7.0 +/- 0.1, partial pressure of carbon dioxide increased 45.6% and partial pressure of oxygen decreased 15.4%). Changes in maternal hemodynamics (decreased systolic blood pressure [17.5%, SD = 11] and decreased diastolic blood pressure [20.3%, SD = 15]) were only noted when uterine blood flows decreased by greater than 38.2% (SD = 26). Correction of maternal hypocalcemia (0.89 g/dL, SD = 0.1) led to improved uterine artery flows (28.3% increase, SD = 30). Finally, fetal sternotomy, cannulation, and cardiopulmonary bypass each decreased uterine artery flows by 27.5% (SD = 18), 31.0% (SD = 26), and 39.7% (SD = 25), respectively. Similar changes were not observed in the nonbypass twin.

CONCLUSIONS

Significant changes in uterine blood flow can occur during fetal cardiopulmonary bypass support without apparent changes in maternal hemodynamics or arterial blood gases. These changes imply a unique transplacental maternal-fetal interaction. Limited data from the twin fetus suggest a localized mechanism involving only the segment of placenta exposed to extracorporeal circulation.

Normal and abnormal transformation of the spiral arteries during pregnancy

This article reviews the anatomy and physiology of the uterine circulation, with emphasis on the remodeling of spiral arteries during normal pregnancy, and the timing and anatomical pathways of trophoblast invasion of the spiral arteries. We review the definitions of the placental bed and basal plate of the placenta, their relevance to the study of the physiologic transformation of the spiral arteries, as well as the methods to obtain and examine placental bed biopsy specimens. We also examine the role of the extravillous trophoblast in normal and abnormal pregnancies, and the criteria used to diagnose failure of physiologic transformation of the spiral arteries. Finally, we comment on the use of uterine artery Doppler velocimetry as a surrogate marker of chronic uteroplacental ischemia.

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

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

Serious foetal growth restriction is associated with reduced proportions of natural killer cells in decidua basalis

Extravillous trophoblasts are major participants in placental development and remodelling of spiral arteries. Trophoblast invasion is regulated by maternal immune cells, and abnormal leucocyte subpopulation composition has been reported in implantation failure. In pre-eclampsia (PE), with or without foetal growth restriction (FGR), superficial trophoblast invasion and insufficient remodelling of spiral arteries are common findings. In the present study, we have compared spiral artery remodelling and leucocyte composition in decidual tissue from 30 cases (PE=8, FGR=5, PE + FGR=17) and 31 controls. Six histological remodelling criteria were established, and each pregnancy obtained a remodelling score. Numbers of natural killer (NK) cells (CD56+), T cells (CD3+) and activated (CD25+ or CD69+) leucocytes were determined and related to total leucocyte (CD45+) numbers in serial sections. Cases demonstrated significantly impaired spiral artery remodelling, inappropriate placental growth and reduced NK cell proportions, as compared to controls (P=0.02, P<0.001 and P=0.01, respectively). Reduced NK cell proportion was primarily found in pregnancies complicated by FGR, with or without PE, and a significant positive correlation was observed between NK cell proportion, trophoblast infiltration and placental growth. Our in vivo observations support the hypothesized association between NK cells, impaired placental development and pathogenesis of PE/FGR.

Vascular biology in implantation and placentation

Pregnancy leads to dramatic changes of the vascular system of the mother and enables the development of a completely new vascular system within the growing embryo including the formation of the placenta as the exchange organ between both circulations. Besides a general adaptation of the maternal blood system, the uterine spiral arteries display the greatest changes. Within placental villi angiogenesis as well as vasculogenesis can be found already a few weeks after implantation. Both systems in parallel will determine the blood flow within the placental villi and the intervillous space. Finally, compromised blood flow on either side of the placental membrane will not only lead to fetal malnutrition, but will also trigger morphological changes of the villous trees. This review tries to cover all the above-mentioned topics and will try to depict the consequences of poor placentation on mother and fetus.

Midtrimester screening for microalbuminuria in healthy pregnant women

To ascertain the effectiveness and feasibility of testing for microalbuminuria and the albumin/creatinine ratio as an early indication of hypertensive disorders of pregnancy, we measured albumin and creatinine excretion in 95 healthy pregnant women between 16 and 20 weeks of pregnancy. Nine women developed hypertensive complications; one of them became pre-eclamptic. There were no statistically significant differences in urine albumin and creatinine concentrations nor in the albumin/creatinine ratio between those women who developed pregnancy-induced hypertension and those who did not. Microalbuminuria testing had a specificity of 0.95 (95% CI: 0.88 - 0.99) and a sensitivity of 0.11 (95% CI: 0.03 - 0.48). The albumin/creatinine ratio had a specificity of 0.98 (95% CI: 0.92 - 1.0) and a sensitivity of 0.22 (95% CI: 0.03 - 0.6). The albumin/creatinine ratio was significantly lower in women who delivered prematurely. We conclude that mid-trimester testing for microalbuminuria and the measurement of the urinary albumin/creatinine ratio are not effective tools for the early recognition of pregnancy-induced hypertension in healthy pregnant women.