GDF15 linked to maternal risk of nausea and vomiting during pregnancy

GDF15, a hormone acting on the brainstem, has been implicated in the nausea and vomiting of pregnancy, including its most severe form, hyperemesis gravidarum (HG), but a full mechanistic understanding is lacking1-4. Here we report that fetal production of GDF15 and maternal sensitivity to it both contribute substantially to the risk of HG. We confirmed that higher GDF15 levels in maternal blood are associated with vomiting in pregnancy and HG. Using mass spectrometry to detect a naturally labelled GDF15 variant, we demonstrate that the vast majority of GDF15 in the maternal plasma is derived from the feto-placental unit. By studying carriers of rare and common genetic variants, we found that low levels of GDF15 in the non-pregnant state increase the risk of developing HG. Conversely, women with β-thalassaemia, a condition in which GDF15 levels are chronically high5, report very low levels of nausea and vomiting of pregnancy. In mice, the acute food intake response to a bolus of GDF15 is influenced bi-directionally by prior levels of circulating GDF15 in a manner suggesting that this system is susceptible to desensitization. Our findings support a putative causal role for fetally derived GDF15 in the nausea and vomiting of human pregnancy, with maternal sensitivity, at least partly determined by prepregnancy exposure to the hormone, being a major influence on its severity. They also suggest mechanism-based approaches to the treatment and prevention of HG.

Birth weight to placenta weight ratio and its relationship to ultrasonic measurements, maternal and neonatal morbidity: A prospective cohort study of nulliparous women

INTRODUCTION

Birth weight to placenta weight (BWPW)-ratio is an indicator of the ability of the placenta to maintain adequate nutrient supply to the fetus. We sought to investigate the relationship between BWPW-ratio with fetal growth, utero-placental Doppler and neonatal and maternal morbidity.

METHODS

We studied a group of 3311 women recruited to a prospective cohort study of nulliparous women (Rosie Hospital, Cambridge, UK) who delivered a live born infant at term and whose placental weight and birth weight were known. Ultrasonic indices and BWPW ratio were converted to gestational age adjusted z scores. Analysis of continuous variables was by multivariable linear regression. BWPW ratio was also categorized (lowest or highest quintile, both referent to quintiles 2 to 4) and associations with adverse outcomes analyzed using multivariable logistic regression.

RESULTS

Lowest quintile of BWPW-ratio was associated (adjusted odds ratio [95% CI], P) with both neonatal morbidity (1.55 [1.12-2.14], 0.007) and maternal diabetes (1.75 [1.18-2.59], 0.005). Highest quintile of BWPW ratio was associated with a reduced risk of maternal obesity (0.71 [0.53 to 0.95], 0.02) and preeclampsia (0.51 [0.31 to 0.84], 0.008), but higher (adjusted z score [95% CI], P) uterine artery Doppler mean pulsatility index (PI) at 20 weeks of gestation (0.09 [0.01-0.18], 0.04) and umbilical artery Doppler PI at 36 weeks of gestation (0.16 [0.07-0.25], <0.001).

CONCLUSION

BWPW-ratio is related to ultrasonic measurements and both neonatal and maternal morbidity. Therefore, this ratio may be an indicative marker of immediate and longer term health risks for an individual.

The relationship between human placental morphometry and ultrasonic measurements of utero-placental blood flow and fetal growth

INTRODUCTION

Ultrasonic fetal biometry and arterial Doppler flow velocimetry are widely used to assess the risk of pregnancy complications. There is an extensive literature on the relationship between pregnancy outcomes and the size and shape of the placenta. However, ultrasonic fetal biometry and arterial Doppler flow velocimetry have not previously been studied in relation to postnatal placental morphometry in detail.

METHODS

We conducted a prospective cohort study of nulliparous women in The Rosie Hospital, Cambridge (UK). We studied a group of 2120 women who had complete data on uterine and umbilical Doppler velocimetry and fetal biometry at 20, 28 and 36 weeks' gestational age, digital images of the placenta available, and delivered a liveborn infant at term. Associations were expressed as the difference in the standard deviation (SD) score of the gestational age adjusted ultrasound measurement (z-score) comparing the lowest and highest decile of the given placental morphometric measurement.

RESULTS

The lowest decile of placental surface area was associated with 0.87 SD higher uterine artery Doppler mean pulsatility index (PI) at 20 weeks (95% CI: 0.68 to 1.07, P < 0.001). The lowest decile of placental weight was associated with 0.73 SD higher umbilical artery Doppler PI at 36 weeks (95% CI: 0.54 to 0.93, P < 0.001). The lowest decile of both placental weight and placental area were associated with reduced growth velocity of the fetal abdominal circumference between 20 and 36 weeks (both P < 0.001).

CONCLUSION

Placental area and weight are associated with uterine and umbilical blood flow, respectively, and both are associated with fetal growth rate.

Energy status and HIF signalling in chorionic villi show no evidence of hypoxic stress during human early placental development

Early human placental and embryonic development occurs in a physiologically low oxygen environment supported by histiotrophic secretions from endometrial glands. In this study, we compare the placental metabolomic profile in the first, second and third trimesters to determine whether the energy demands are adequately met in the first trimester. We investigated whether hypoxia-inducible factors, HIF-1α and/or HIF-2α, might regulate transcription during the first trimester. First and second trimester tissue was collected using a chorionic villus sampling-like (CVS) technique. Part of each villus sample was frozen immediately and the remainder cultured under 2 or 21% O2 ± 1 mM H2O2, and ±the p38 MAPK pathway inhibitor, PD169316. Levels of HIF-1α were assessed by western blotting and VEGFA, PlGF and GLUT3 transcripts were quantified by RT-PCR. Term samples were collected from normal elective Caesarean deliveries. There were no significant differences in concentrations of ADP, NAD(+), lactate, and glucose, and in the ATP/ADP ratio, across gestational age. Neither HIF-1α nor HIF-2α could be detected in time-zero CVS samples. However, culture under any condition (2 or 21% O2 ± 1 mM H2O2) increased HIF-1α and HIF-2α. HIF-1α and HIF-2α were additionally detected in specimens retrieved after curettage. HIF-1α stabilization was accompanied by significant increases in VEGFA and GLUT3 and a decrease in PlGF mRNAs. These effects were suppressed by PD169316. In conclusion, our data suggest that first trimester placental tissues are not energetically compromised, and that HIF-1α is unlikely to play an appreciable role in regulating transcriptional activity under steady-state conditions in vivo. However, the pathway may be activated by stress conditions.

Influence of speed of sample processing on placental energetics and signalling pathways: implications for tissue collection

Introduction

The placenta is metabolically highly active due to extensive endocrine and active transport functions. Hence, placental tissues soon become ischaemic after separation from the maternal blood supply. Ischaemia rapidly depletes intracellular ATP, and leads to activation of stress-response pathways aimed at reducing metabolic demands and conserving energy resources for vital functions. Therefore, this study aimed to elucidate the effects of ischaemia ex vivo as may occur during tissue collection on phosphorylation of placental proteins and kinases involved in growth and cell survival, and on mitochondrial complexes.

Methods

Eight term placentas obtained from normotensive non-laboured elective caesarean sections were kept at room-temperature and sampled at 10, 20, 30 and 45 min after delivery. Samples were analyzed by Western blotting.

Results

Between 10 and 45 min the survival signalling pathway intermediates, P-AKT, P-GSK3α and β, P-4E-BP1 and P-p70S6K were reduced by 30–65%. Stress signalling intermediates, P-eIF2α increased almost 3 fold after 45 min. However, other endoplasmic reticulum stress markers and the Heat Shock Proteins, HSP27, HSP70 and HSP90, did not change. Phosphorylation of AMPK, an energy sensor, was elevated 2 fold after 45 min. Contemporaneously, there was an ∼25% reduction in mitochondrial complex IV subunit I.

Discussion and conclusions

These results suggest that for placental signalling studies, samples should be taken and processed within 10 min of caesarean delivery to minimize the impact of ischaemia on protein phosphorylation.

Regulation of vascular growth and function in the human placenta

During the course of 9 months, the human placenta develops into a highly vascular organ. Vasculogenesis starts during the third week post-conception. Hemangioblastic cell cords differentiatein situfrom mesenchymal cells in the villous cores, most probably under the influence of vascular endothelial growth factor (VEGFA) secreted by the overlying trophoblast. The cords elongate through proliferation and cell recruitment, and connect with the vasculature of the developing fetus. A feto-placental circulation starts around 8 weeks of gestation. Elongation of the capillaries outstrips that of the containing villi, leading to looping of the vessels. The obtrusion of both capillary loops and new sprouts results in the formation of terminal villi. Branching and non-branching angiogenesis therefore play key roles in villous morphogenesis throughout pregnancy. Maternal circulating levels of VEGFA and placental growth factor vary across normal pregnancy, and in complicated pregnancies. Determining the impact of these changes on placental angiogenesis is difficult, as the relationship between levels of factors in the maternal circulation and their effects on fetal vessels within the placenta remains unclear. Furthermore, the trophoblast secretes large quantities of soluble receptors capable of binding both growth factors, influencing their bioavailability. Villous endothelial cells are prone to oxidative stress, which activates the apoptotic cascade. Oxidative stress associated with onset of the maternal circulation, and with incomplete conversion of the spiral arteries in pathological pregnancies, plays an important role in sculpting the villous tree. Suppression of placental angiogenesis results in impoverished development of the placenta, leading ultimately to fetal growth restriction.

Effect of low-dose mifepristone administration on day 2 after ovulation on transcript profiles in implantation-stage endometrium of rhesus monkeys

Progesterone is essential for endometrial receptivity in primates. In studies previously performed using global gene profiling based on microarray technology, attempts have been made to identify changes in gene expression between early luteal-phase and mid-luteal-phase endometria. However, the issue of the putative impact of preimplantation embryo-derived signal in the process of endometrial receptivity was missing in the previous studies. In the present study, an attempt has been made to delineate the transcripts profile in implantation-stage endometrium under combinatorial regulation of progesterone and embryo-derived signal in the rhesus monkey. To this effect, we have compared transcript profiles for 409 known genes between control receptive stage (n=13), and mifepristone-induced desynchronized and non-receptive stage (n=12) monkey endometrial samples collected on days 4 (n=12) and 6 (n=13) after ovulation from mated, potential conception cycles, using cDNA arrays containing sequence-verified clones. Statistical analysis of correlation of estimated transcript abundance between arrays and qRT-PCR for nine selected gene products yielded significant (P<0.05) concordance. Of 409 genes, a total of 40 gene transcripts were seen to be affected, nine gene transcripts in endometrial samples were found to progressively increase between days 4 and 6 following mifepristone treatment, while an additional five genes showed differential expression profile depending on the day after treatment. Additionally, different sets of 12 and 14 gene products showed changes in days 4 and 6 post-ovulation samples respectively. A new cohort of 28 gene products in implantation-stage endometrium was seen to be affected by luteal-phase mifepristone.

Placental endoplasmic reticulum stress and oxidative stress in the pathophysiology of unexplained intrauterine growth restriction and early onset preeclampsia

The pregnancy complications of unexplained intrauterine growth restriction and early onset preeclampsia are thought to share a common aetiology in placental malperfusion secondary to deficient maternal spiral artery conversion. A key question is whether the contrasting clinical manifestations reflect different placental pathologies, or whether they are due to altered maternal responses to a common factor derived from the placenta. Recently, molecular evidence of protein synthesis inhibition secondary to endoplasmic reticulum stress has provided an explanation for the small placental phenotype in both conditions. However, other pathways activated by more severe endoplasmic reticulum stress are only observed in placentas from pregnancies associated with early onset preeclampsia. Here, we review the literature and conclude that there is evidence of greater maternal vascular compromise of the placenta in these cases. We speculate that in cases of normotensive intrauterine growth restriction the placental pathology is centred predominantly around endoplasmic reticulum stress, whereas in cases complicated by preeclampsia oxidative stress is further superimposed. This causes the release of a potent mix of pro-inflammatory cytokines, anti-angiogenic factors and trophoblastic aponecrotic debris into the maternal circulation that causes the peripheral syndrome. Maternal and fetal constitutional factors may modulate how the placenta responds to the maternal vascular insult, and how the mother is affected by the placental factors released. However, the principal conclusion is that the difference between these two conditions lies in the severity of the initiating deficit in spiral arterial conversion, and the relative degrees of endoplasmic reticulum stress and oxidative stress induced in the placenta as a result.

Mifepristone induced progesterone withdrawal reveals novel regulatory pathways in human endometrium

In women, a single dose of the antiprogestin mifepristone (RU486) in the secretory phase rapidly renders the endometrium unreceptive and is followed by endometrial breakdown and menstruation within 72 h. This model provides a system to identify progesterone-regulated genes, which may be involved in endometrial receptivity and the induction of menstruation. We used cDNA microarrays to monitor the response of the endometriuim over 24 h following administration of mifepristone in the mid-secretory phase. We identified 571 transcripts whose expression was significantly altered, representing 131 biochemical pathways. These include new progesterone regulated members of the Wnt, matrix metalloproteinase (MMP), prostaglandin (PG) and chemokine regulatory pathways. Transcripts involved in thyroid hormone metabolism and signalling such as type II iodothyronine deiodinase and thyroid receptors were also found to be highly regulated by progesterone antagonism in the endometrium. Transcripts required for thyroid hormone synthesis such as thyroid peroxidase (TPO) and thyroglobulin (TG) were also expressed, indicating that the endometrium may be a site of thyroxin production. These results add to the existing knowledge of the role of the Wnt, chemokine, MMP and PG pathways in receptivity and early menstrual events. They provide in vivo evidence supporting direct or indirect regulation of many new transcripts by progesterone. We have also identified for the first time the very early transcriptional changes in vivo in response to progesterone withdrawal. This greatly increases our understanding of the pathways leading to menstruation and may provide new approaches to diagnose and treat menstrual disorders.

Immunoneutralization of vascular endothelial growth factor inhibits pregnancy establishment in the rhesus monkey (Macaca mulatta)

Maternal endometrial vascular endothelial growth factor (VEGF) is considered important in blastocyst implantation. However, there is no direct evidence to support this conjecture in the primate. In the present study, we have examined this hypothesis by testing whether immunoneutralization of VEGF during the peri-implantation stage of gestation affects embryo implantation in the rhesus monkey. Adult female animals (n = 36) during mated ovulatory cycles were randomly assigned to one of the experimental groups treated subcutaneously with either isotype-matched mouse immunoglobulin (group 1: control, n = 8) or monoclonal mouse antibody against VEGF-A (anti-VEGF Mab; group 2: 10 mg on day 5 after ovulation, n = 8; group 3: 20 mg on day 5 after ovulation, n = 8; group 4: 10 mg on day 10 after ovulation, n = 4; group 5: 10 mg on days 5 and 10 after ovulation, n = 8). Anti-VEGF Mab-treated animals in groups 2–4 did not show any marked inhibition in pregnancy establishment. On pooled analysis, however, anti-VEGF Mab administration in groups 2–5 (n = 28) resulted in a significant (P < 0.04) decline in the number of viable term pregnancy when compared with control animals. The observed difference was explained by the fact that 10 mg anti-VEGF Mab given to each animal on days 5 and 10 after ovulation in group 5 (n = 8) inhibited pregnancy establishment significantly (P < 0.02) when compared with control group 1. There was no significant change in serum concentrations of estradiol-17β, progesterone, and free VEGF among groups. Furthermore, animals treated with anti-VEGF Mab (n = 8) as in group 5 revealed marked decrease in immunoreactive VEGF, fms-like tyrosine kinase-1, and kinase-insert domain region in trophoblast cells associated with shallow uterine invasion on day 13 of gestation when compared with samples from control group animals (n = 8). Thus, VEGF action is required for successful blastocyst implantation in the rhesus monkey.

Human early placental development: potential roles of the endometrial glands

There is strong evidence that the endometrial glands play a key role in regulating placental development in many domestic species, but their contribution in the human has largely been ignored once implantation is complete. Here we re-evaluate their role during the first trimester. Connections between the glands and the intervillous space have been observed from day 17 post-conception through to the end of the first trimester. In the absence of a maternal arterial supply to the early placenta it is believed that the carbohydrate- and lipid-rich secretions represent an important source of nutrients during the first trimester, and possibly the beginning of the second trimester. The secretions also contain a variety of growth factors that may regulate placental morphogenesis since their receptors are present on villous and extravillous trophoblast, and villous endothelial cells. Other components of the secretions may modulate immune responses and trophoblast invasion at the materno-fetal interface. We speculate that lactogenic hormones secreted by decidual cells and the syncytiotrophoblast may act in concert with human chorionic gonadotropin to stimulate the secretory activity of glandular epithelial cells during the first trimester. There is circumstantial evidence, but as yet no conclusive proof, that deficient glandular activity is associated with pregnancy failure in the human.

Nimesulide, a COX-2 inhibitor, does not reduce lesion size or number in a nude mouse model of endometriosis

BACKGROUND

Women with endometriosis have elevated levels of cyclooxygenase-2 (COX-2) in peritoneal macrophages and endometriotic tissue. Inhibition of COX-2 has been shown to reduce inflammation, angiogenesis and cellular proliferation. It may also downregulate aromatase activity in ectopic endometrial lesions. Ectopic endometrial establishment and growth are therefore likely to be suppressed in the presence of COX-2 inhibitors. We hypothesized that COX-2 inhibition would reduce the size and number of ectopic human endometrial lesions in a nude mouse model of endometriosis.

METHODS

The selective COX-2 inhibitor, nimesulide, was administered to estrogen-supplemented nude mice implanted with human endometrial tissue. Ten days after implantation, the number and size of ectopic endometrial lesions were evaluated and compared with lesions from a control group. Immunohistochemical assessment of vascular development and macrophage and myofibroblast infiltration in control and treated lesions was performed.

RESULTS

There was no difference in the number or size of ectopic endometrial lesions in control and nimesulide-treated nude mice. Nimesulide did not induce a visually identifiable difference in blood vessel development or macrophage or myofibroblast infiltration in nude mouse explants.

CONCLUSION

The hypothesized biological properties of COX-2 inhibition did not influence lesion number or size in the nude mouse model of endometriosis.

Aspects of human fetoplacental vasculogenesis and angiogenesis. I. Molecular regulation

Patterns of fetoplacental angiogenesis vary during gestation and in association with certain pregnancy pathologies. In a set of three linked reviews, we provide a survey of current knowledge about the molecular regulation, cellular players, qualitative and quantitative morphological features of the vascularization of human placental villi. Here, an account is given of the role played by hypoxia-inducible factor in mediating the effects of oxygen on production of growth factor ligands and receptors which regulate angiogenesis and vessel maturation. However, it should be noted that, for the human placenta early in gestation, the normal (i.e. physiological) partial pressure of O(2)is low but this does not mean that the tissue is hypoxic. Thus, the mechanisms of regulating angiogenic growth factor production may differ at this time in comparison to those found later in gestation or in other tissues or organs. The vasculature in the placenta is plastic and changes markedly as gestation progresses. This is controlled by the complex interplay between physical factors and chemical factors including oxygen, growth factors and growth inhibitors. The companion reviews describe morphological features of normal and pathological development of the human placenta in the context of the factors discussed here.

Aspects of human fetoplacental vasculogenesis and angiogenesis. II. Changes during normal pregnancy

In this second review, we describe the main morphological events which accompany the development of the fetoplacental vascular system throughout normal human pregnancy and summarize findings on the expression of angiogenic growth factors and their receptors. Fetoplacental vasculogenesis starts at day 21 after conception by formation of haemangioblastic cords. In the following phase of branching angiogenesis (day 32 to week 25 post conception), haemangioblastic cords develop into a richly branched villous capillary bed with low fetoplacental blood flow impedance. This period is characterized by high placental levels of VEGF but moderate PlGF expression. In week 15, large centrally located villi show regression of peripheral capillary nets. In parallel, some remaining central capillaries acquire a tunica media and transform into arteries and veins. Beginning at about week 25 in the newly formed peripheral villi, angiogenesis switches from branching to non-branching and this period is accompanied by a steep drop in VEGF and a slower decline in PlGF expression. As a consequence of this switch, long poorly branched capillary loops are formed in the periphery of the fetoplacental vascular trees. These increase fetoplacental impedance but blood flow still increases due to rising fetal blood pressure. The possible interactions between (a). the biphasic development of intraplacental oxygen tensions, (b). changes in VEGF and PlGF levels and (c). developing vascular geometry are discussed. Special attention is given to the obvious discrepancy between sudden elevation of intervillous oxygen tensions which is not coincident with the appearance of angiogenic growth factor peaks and the switch from branching to non-branching angiogenesis. Finally, we deal with methods of quantifying aspects of angiogenesis in the villous vascular system and summarize the main findings during uncomplicated human pregnancy.

Aspects of human fetoplacental vasculogenesis and angiogenesis. III. Changes in complicated pregnancies

Patterns of fetoplacental angiogenesis vary not only during the course of a normal pregnancy but also in certain pregnancy pathologies. Here, we review some of the molecular and morphological events which occur in complicated pregnancies. The pregnancy complications are chosen in an attempt to represent the possible different origins (preplacental, uteroplacental, postplacental) of fetal hypoxia. Molecular events focus on reported changes in hypoxia-inducible factors, angiopoietins and the vascular endothelial, basic fibroblast and placenta growth factors and their receptors. Morphological changes focus on patterns of angiogenesis (branching and non-branching) and a consistent set of morphometric descriptors (covering measures of total capillary growth, villous capillarization and capillary size and shape in transverse section). Apart from some uncertainties due to lack of information, or failure to resolve fully the effects of intrauterine growth restriction and pre-eclampsia, alterations in the angiogenic growth factors and morphologies of capillaries and villi in different complicated pregnancies seem to conform reasonably well to those predicted by the fetal hypoxia paradigm. However, it is clear that future studies on the effects of different origins of fetal hypoxia should exercise more care in the choice and interpretation of relevant descriptors and take more account of the parallel effects of possible confounders. In addition, rather than comparing uncomplicated and complicated pregnancies only at term, more information about molecular and morphological events that occur throughout gestation would be extremely valuable. This includes further studies on changes in growth factor receptors, the less-well-documented angiogenic factors (e.g. angiogenin, angiostatin, endostatin) and the associations between endothelial cells and pericytes. A more integrated approach involving also parallel analysis of the effects of erythropoietin and other potential vasoactive factors on the behaviour and morphology of fetal vessels would be beneficial.

The effect of RU486 on the gene expression profile in an endometrial explant model

Administration of RU486 in vivo during the receptive phase rapidly renders the endometrium non-receptive to the implanting embryo. In order to identify key pathways responsible for endometrial receptivity we have used cDNA arrays to monitor gene expression changes in short-term endometrial explants in response to RU486. Endometrial biopsies from five normal fertile women at mid-secretory phase were cultured in the presence of estradiol and progesterone with or without RU486 for 12 h. cDNA arrays were produced containing approximately 1000 sequence-verified clones which included genes known to be important in angiogenesis, apoptosis, cell signalling, extracellular matrix remodelling and cell cycle regulation. cDNA probes from the paired endometrial samples were hybridized to the arrays and hybridization signals were quantified. A total of 12 genes displayed significant changes in expression; six were up-regulated and six down-regulated following RU486 treatment. For five of these genes this is the first report suggesting that they are regulated by steroids in the endometrium. JAK1 and JNK1 were two of the genes shown by the arrays to be down-regulated in RU486-treated endometrial explants. This was confirmed by real time RT-PCR. JAK1 immunoreactivity was localized to both glandular epithelium and the stroma of normal endometrium and staining was much stronger in the luteal phase of the cycle. These results show that components of two important signalling pathways in endometrium-the JAK/STAT pathway, and the JNK pathway-are altered by RU486. Genes whose expression is controlled by these pathways are likely to be involved in the mechanism by which steroids render the endometrium receptive to the implanting embryo.

Intralobular differences in antioxidant enzyme expression and activity reflect the pattern of maternal arterial bloodflow within the human placenta

The aim was to determine whether the activities and mRNA concentrations of antioxidant enzymes in human placental tissues reflect the prevailing oxygen tension or developmental maturity of the villi. Advantage was taken of contrasting gradients within lobules of the mature placenta. The central region is well-oxygenated compared to the periphery, owing to the direction of maternal blood flow. However, central villi are morphologically and enzymatically immature compared to peripheral villi. Activity of catalase (t=8.72, P< 0.001) and glutathione peroxidase (t=2.17,P< 0.05) was higher in central than peripheral villi, but no difference was detected for total superoxide dismutase (t=1.08, P> 0.05). The degree of change in catalase activity across the lobule correlated closely with the radius (r=-0.70, P< 0.01). The mRNA concentration was higher in the centre for catalase (t=2.81, P< 0.05) and for glutathione peroxidase (t=3.33, P< 0.05), but no differences were found for copper/zinc or manganese superoxide dismutase. In separate experiments, first trimester villi cultured under 10 per cent oxygen contained higher concentrations of catalase mRNA than controls maintained under 2.5 per cent oxygen. We conclude that the activities of catalase and glutathione peroxidase reflect gradients established by the pattern of maternal intralobular bloodflow, and that oxygen tension is one regulatory factor in vitro.

Vascular endothelial growth factor-D is an independent prognostic factor in epithelial ovarian carcinoma

We assessed the presence of vascular endothelial growth factor (VEGF)-C, VEGF-D and their receptor VEGFR-3 by immunohistochemistry in 59 epithelial ovarian carcinomas, 11 borderline tumours and 20 benign cystadenomas. VEGF-C and VEGF-D were generally expressed in tumour cells and also in endothelia adjacent to tumour nests which showed a strong staining for them. VEGFR-3 was expressed in lymphatic and vascular endothelial cells adjacent to tumour nests. Immunoreactivity was significantly more frequent as lesions progressed from a benign tumour to advanced carcinoma. A strong correlation was found between VEGF-C and VEGF-D detected in carcinoma and VEGFR-3 detected in neighbouring endothelial cells. Increased expression of VEGF-C, VEGF-D and VEGFR-3 was significantly associated with lymph node metastasis and peritoneal metastasis outside the pelvis. There was a significant correlation between the high levels of VEGF-C and VEGF-D proteins, and poor survival. The presence of VEGF-D was an independent prognostic indicator by multivariate analysis. We conclude that VEGF-C, VEGF-D and VEGFR-3 play an important role in lymphatic spread and intraperitoneal tumour development in ovarian carcinoma. Since VEGF-D was found to be an independent predictor of poor outcome, its measurement, together with other prognostic markers may improve prospective identification of patients with a poor prognosis.

Expression of CD105 (endoglin) in arteriolar endothelial cells of human endometrium throughout the menstrual cycle

The cellular mechanisms underlying normal and pathological endometrial bleeding are not well understood, although abnormalities in the structure of endometrial blood vessels may lead to menstrual disorders. Endothelial cells in different organs are heterogeneous and differ in structure, function, antigen composition, metabolic properties and responses to growth factors. Immunostaining was performed with anti-CD105, CD31, CD34 and von Willebrand factor (vWF), and lectin binding with Ulex europaeus agglutinin 1 (UEA 1), Bandeieraea simplicifolia agglutinin 1 (BS 1), Dolichos biflorus agglutinin (DBA) and Peanut agglutinin (PNA) to characterize endothelial cells in human endometrium throughout the menstrual cycle. Serial sections fixed with formalin were stained with primary antibodies and lectins after antigen retrieval. Positive staining for CD31, CD105 and vWF was confined to the vascular endothelium. Endothelial expression of CD31 was observed in all types of vessel, including single cells, and strong staining was found during the early proliferative and mid-secretory phases. Anti-vWF stained arterioles and veins, but there was little positive staining of capillaries. In contrast, staining for CD105 was confined to the arterioles. Although anti-CD34 strongly stained endothelial cells of small vessels and capillaries, staining was also observed on some non-endothelial stromal cells. Strong positive staining for UEA 1 was observed in endothelial cells of all types of vessel throughout the menstrual cycle. Binding of PNA, DBA and BS 1 was confined to the apical region of glandular epithelial cells. This study demonstrates that the differential binding of anti-CD31, CD34, CD105, vWF and UEA 1 distinguishes between endometrial populations of endothelial cells.

Placental vessel adaptation during gestation and to high altitude: changes in diameter and perivascular cell coverage

The objective of this study was to determine how human placental vascular structures change during gestation and whether this would be altered by external factors such as reduced ambient oxygen. To achieve this, several experiments were carried out: Vessel profile diameter was measured and the presence of perivascular cells (pericytes or smooth muscle cells) noted. This was carried out in normal human first trimester and term placentae, and in term placentae obtained from high altitude and an ethnically matched lowland population. In addition, to characterize endothelial cells in human placenta a panel of endothelial markers anti-CD 105, CD31, CD34, Von Willebrand factor (vWF), Ulex europaeus agglutinin 1 (UEA I), Peanut agglutinin (PNA), Dolichos biflorus agglutinin (DBA) and Bandeieraea simplicifolia agglutinin 1 (BS 1) was used. The proportion of vessels associated with perivascular cells rises during gestation from 37 per cent in the first trimester to 63 per cent at term (P<0.0001) and vessels with perivascular cells have a larger median diameter at term. In placentae obtained at high altitude, the vessels are dilated and are less frequently associated with perivascular cells. The absence of perivascular cells may allow remodelling of capillaries and this is likely to be physiological important in the first trimester but also under physiological or pathological stress.

Is estradiol cardioprotection a nitric oxide-mediated effect?

BACKGROUND

Estradiol exerts a number of biological effects that support extensive observational data suggesting a protective role for estrogen in cardiovascular disease prevention. These include effects on lipid and carbohydrate metabolism, coagulation/fibrinolysis as well as a possible effect on vascular reactivity. It has been proposed that this might be mediated by vascular endothelial nitric oxide (NO) production. Accordingly, we designed complementary in-vivo and in-vitro studies to investigate this hypothesis further.

METHODS

Firstly, in a group of 10 healthy post-menopausal women, bilateral venous occlusion plethysmography was used to examine forearm vasoconstrictor responses to intrabrachial N(G)-monomethyl-l-arginine (l-NMMA; a substrate inhibitor of nitric oxide synthase) both before and after 4 weeks of treatment with transdermal 17beta-estradiol (E(2)) (80 microg/day). Secondly, we examined the direct effects of acute (24 h) and chronic (7 days) treatment with E(2) (10 pmol/l and 10 nmol/l) on endothelial nitric oxide synthase (eNOS) gene expression in cultured human aortic endothelial cells.

RESULTS

No significant differences were observed between the vasoconstrictor responses to l-NMMA (2, 4, 8 micromol/min) before and after E(2) treatment. Comparison of E(2)-treated endothelial cells with control cells showed no significant increase in eNOS mRNA expression following either acute or chronic estradiol treatment.

CONCLUSIONS

The present studies do not provide evidence for an eNOS-mediated cardioprotective response to estrogen and therefore suggest that additional mechanisms other than the endothelial NO system may have an important role in the cardiovascular effects of estrogen.

Distribution of vascular endothelial growth factor (VEGF) and its binding sites at the maternal-fetal interface during gestation in pigs

Pigs show epitheliochorial placentation, in which the maternal uterine epithelium and the fetal trophectoderm become closely apposed. There is no invasion of trophoblast into the maternal tissue, and nutrient and waste exchange take place across two epithelial layers beneath which a complex network of capillaries forms. Later in gestation, the epithelial cells become indented by blood vessels, which greatly reduces the distance for diffusion between the two circulatory systems. Vascular endothelial growth factor is a secreted homodimeric angiogenic growth factor that is involved in physiological and pathological angiogenesis. Its receptors are generally restricted to endothelial cells. Ligand binding, in situ hybridization and immunohistochemistry were carried out in pig placenta throughout gestation to investigate the possible role of vascular endothelial growth factor and its receptors in non-invasive placentation. In situ hybridization and immunohistochemistry revealed that mRNA and immunoreactivity for vascular endothelial growth factor were localized in both maternal and fetal epithelial cells at the maternal-fetal interface and over the maternal glands, although the signal was generally weaker in the maternal glands. Ligand binding was used to localize for vascular endothelial growth factor receptors; no binding was observed over the maternal glands, but very strong binding was localized to the endometrial blood vessels. At the interface between maternal and fetal tissue, a similar pattern was observed whereby the numerous small capillaries at the bases of the two apposed epithelia bound vascular endothelial growth factor specifically. It is concluded that vascular endothelial growth factor produced by the maternal and fetal epithelial layers promotes the growth of capillaries locally, which would facilitate the development of two vascular networks for the efficient transfer of nutrients and waste products.

Distribution of vascular endothelial growth factor (VEGF) and its binding sites at the maternal-fetal interface during gestation in pigs

Pigs show epitheliochorial placentation, in which the maternal uterine epithelium and the fetal trophectoderm become closely apposed. There is no invasion of trophoblast into the maternal tissue, and nutrient and waste exchange take place across two epithelial layers beneath which a complex network of capillaries forms. Later in gestation, the epithelial cells become indented by blood vessels, which greatly reduces the distance for diffusion between the two circulatory systems. Vascular endothelial growth factor is a secreted homodimeric angiogenic growth factor that is involved in physiological and pathological angiogenesis. Its receptors are generally restricted to endothelial cells. Ligand binding, in situ hybridization and immunohistochemistry were carried out in pig placenta throughout gestation to investigate the possible role of vascular endothelial growth factor and its receptors in non-invasive placentation. In situ hybridization and immunohistochemistry revealed that mRNA and immunoreactivity for vascular endothelial growth factor were localized in both maternal and fetal epithelial cells at the maternal-fetal interface and over the maternal glands, although the signal was generally weaker in the maternal glands. Ligand binding was used to localize for vascular endothelial growth factor receptors; no binding was observed over the maternal glands, but very strong binding was localized to the endometrial blood vessels. At the interface between maternal and fetal tissue, a similar pattern was observed whereby the numerous small capillaries at the bases of the two apposed epithelia bound vascular endothelial growth factor specifically. It is concluded that vascular endothelial growth factor produced by the maternal and fetal epithelial layers promotes the growth of capillaries locally, which would facilitate the development of two vascular networks for the efficient transfer of nutrients and waste products.

The regulation and localization of angiopoietin-1, -2, and their receptor Tie2 in normal and pathologic human placentae

BACKGROUND

Angiopoietin-1 (Ang-1) and its antagonist angiopoietin-2 (Ang-2) act on the endothelial cell Tie-2 receptor to regulate vascular integrity and remodeling. The local balance of these factors and the level of other angiogenic factors determine whether blood vessels grow, are maintained or regress. Profound angiogenesis and vascular remodeling occur in the placenta and this is altered in preeclampsia, a major cause of maternal and fetal morbidity and mortality.

MATERIALS AND METHODS

The mRNAs encoding Ang-1, Ang-2, and Tie-2 were detected and localized in human placentae throughout gestation. The mechanism of regulation angiopoietin mRNAs level was determined by explant culture in ambient and reduced oxygen, and in the presence of actinomycin D.

RESULTS

In situ hybridization showed that Ang-2 mRNA was abundant in the syncytiotrophoblast in the first trimester of human pregnancy. Ang-1 mRNA could not be detected by in situ hybridization, but was by reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blotting. Placental vascular structure is altered in preeclampsia and intrauterine growth restriction, conditions where feto-placental oxygenation is perturbed. In villous explant cultures, a reduction in oxygen tension significantly raised the levels of Ang-2 mRNA, and this was dependent on transcription. However, similar experiments showed that the stability of the Ang-1 message was greatly reduced under these conditions. Thus, hypoxia has opposite effects on Ang-1 and Ang-2 mRNA levels. Placentae obtained from women with preeclampsia had reduced levels of Ang-2 mRNA compared to gestationally matched controls. There was no difference in the levels of Ang-1 mRNAs.

CONCLUSIONS

These data show that the relative levels of Ang-1 and Ang-2 mRNA are regulated by local oxygen tension by different mechanisms and that this may be important during normal human placentation.

Synergism between vascular endothelial growth factor and placental growth factor contributes to angiogenesis and plasma extravasation in pathological conditions

Vascular endothelial growth factor (VEGF) stimulates angiogenesis by activating VEGF receptor-2 (VEGFR-2). The role of its homolog, placental growth factor (PlGF), remains unknown. Both VEGF and PlGF bind to VEGF receptor-1 (VEGFR-1), but it is unknown whether VEGFR-1, which exists as a soluble or a membrane-bound type, is an inert decoy or a signaling receptor for PlGF during angiogenesis. Here, we report that embryonic angiogenesis in mice was not affected by deficiency of PlGF (Pgf-/-). VEGF-B, another ligand of VEGFR-1, did not rescue development in Pgf-/- mice. However, loss of PlGF impaired angiogenesis, plasma extravasation and collateral growth during ischemia, inflammation, wound healing and cancer. Transplantation of wild-type bone marrow rescued the impaired angiogenesis and collateral growth in Pgf-/- mice, indicating that PlGF might have contributed to vessel growth in the adult by mobilizing bone-marrow-derived cells. The synergism between PlGF and VEGF was specific, as PlGF deficiency impaired the response to VEGF, but not to bFGF or histamine. VEGFR-1 was activated by PlGF, given that anti-VEGFR-1 antibodies and a Src-kinase inhibitor blocked the endothelial response to PlGF or VEGF/PlGF. By upregulating PlGF and the signaling subtype of VEGFR-1, endothelial cells amplify their responsiveness to VEGF during the 'angiogenic switch' in many pathological disorders.

Angiogenic growth factor messenger ribonucleic acids in uterine natural killer cells

Angiogenesis is essential for endometrial growth and repair, and disruption of this process may lead to common disorders of women, including menorrhagia and endometriosis. In pregnancy, failure of the endometrial spiral arterioles to undergo remodeling leads to preeclampsia. Here we report that in addition to vascular endothelial growth factor A (VEGF-A), human endometrium expresses messenger ribonucleic acids (mRNAs) encoding VEGF-C, placenta growth factor (PlGF), the angiopoietins, angiopoietin 1 (Ang1) and Ang2, and the receptors VEGFR-3 (Flt-4), Tie 1, and Tie 2. Levels of VEGF-C, PlGF, and Tie 2 changed during the menstrual cycle. Intense hybridization for VEGF-C and PlGF mRNAs was found in uterine nature killer cells in secretory phase endometrium and for Ang2 mRNA in the same cells in the late secretory phase. Interleukin-2 (IL-2) and IL-15 up-regulated VEGF-C, but not PlGF or Ang2, mRNA levels in isolated NK cells. Conditioned medium from decidual NK cells did not induce human umbilical vein endothelial cell apoptosis. These results indicate that human endometrium expresses a wide range of angiogenic growth factors and that uterine nature killer cells may play an important role in the abnormal endometrial angiogenesis that underlies a range of disorders affecting women.

Placental vascular morphogenesis

Appropriate growth and development of the placenta is essential for fetal growth and wellbeing, and indeed may be an important factor in determining adult health. As the fetus grows its demands increase and the capacity of the placenta to facilitate transfer between the fetal and maternal circulations increases as gestation progresses. The principal units for diffusional exchange of oxygen are the terminal villi, and these develop in the third trimester. It is thought that capillary growth within the villi drives the growth of these structures which are characterized by a high proportion of their volume being occupied by fetal capillaries and extreme thinning of the trophoblast and endothelial cell layers. In the first trimester the PO2 in the intervillous space is low and rises sharply at the start of the second. Endothelial growth is influenced by a variety of soluble factors, and several of these are regulated by oxygen, for example, vascular endothelial growth factor (VEGF), angiopoietin 2, and soluble flt (a VEGF antagonist). Thus, fetal demand may regulate villous growth and differentiation by altering local PO2 which, in turn, modulates growth factors (or their antagonists) to regulate endothelial growth and vessel re-modelling.

Expression of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) in conceptus and endometrium during implantation in the rhesus monkey

The aim of this study was to analyse the expression of transcripts and proteins for vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) in different compartments of the early conceptus at primary implantation sites during lacunar (n = 6), early villous (n = 9) and villous placenta (n = 6) stages of gestation in the rhesus monkey. During the lacunar stage, VEGF expression was observed in the cytotrophoblast cells lining the extraembryonic cavity, but these cells did not express PlGF. With further development, cytotrophoblast cells lining villi, forming columns, and constituting anchoring villi, expressed both VEGF and PlGF during early villous and villous placenta stages. In addition, chorion, amnion and villous stromal cells expressed both VEGF and PlGF proteins and mRNA. During the lacunar stage, all epithelial cells in maternal endometrium generally expressed VEGF, while PlGF expression was observed in the plaque epithelium only. As gestation advanced, the expression of VEGF and PlGF from plaque cells decreased, and in surface and glandular epithelium the expression of VEGF increased, while the expression of PlGF remained unaltered. Decidual stromal cells expressed VEGF and PlGF only at low levels during the lacunar stage, while the expression of both increased during the early villous and the villous placenta stages of implantation. It appears from the present study that the expression of VEGF and PlGF are regulated in a temporal and spatial manner during early stages of implantation and that their concerted actions in placental and maternal compartments play a critical role in the evolving pregnancy in the rhesus monkey.

Changes in tumorigenesis- and angiogenesis-related gene transcript abundance profiles in ovarian cancer detected by tailored high density cDNA arrays

BACKGROUND

Complementary DNA array analysis of gene expression has a potential application for clinical diagnosis of disease processes. However, accessibility, affordability, reproducibility of results, and management of the data generated remain issues of concern. Use of cDNA arrays tailored for studies of specific pathways, tissues, or disease states may render a cost- and time-effective method to define potential hallmark genotype alterations.

MATERIALS AND METHODS

We produced a 332-membered human cDNA array on nylon membranes tailored for studies of angiogenesis and tumorigenesis in reproductive disease. We tested the system for reproducibility using a novel statistical approach for analysis of array data and employed the arrays to investigate gene expression alterations in ovarian cancer.

RESULTS

Intra-assay analysis and removal of agreement outliers was shown to be a critical step prior to interpretation of cDNA array data. The system revealed highly reproducible results, with intermembrane coefficient of reproducibility of +/- 0.98. Comparison of placental and ovarian sample data confirmed expected differences in angiogenic profiles and tissue-specific markers, such as human placental lactogen (hPL). Analysis of expression profiles of five normal ovary and four poorly differentiated serous papillary ovarian adenocarcinoma samples revealed an overall increase in angiogenesis-related markers, including vascular endothelial growth factor (VEGF) and angiopoietin-1 in the diseased tissue. These were accompanied by increases in immune response mediators (e.g. HLA-DR, Ron), apoptotic and neoplastic markers (e.g. BAD protein, b-myb), and novel potential markers of ovarian cancer, such as cofilin, moesin, and neuron-restrictive silencer factor (REST) protein.

CONCLUSIONS

In-house production of tailored cDNA arrays, coupled to comprehensive analysis of resulting hybridization profiles, provides an accessible, reliable, and highly effective method of applying array technology to study disease processes. In the ovary, abundance of specific tumor markers, increased macrophage recruitment mediators, a late-stage angiogenesis profile, and the presence of chemoresistance-related markers distinguished normal and advanced ovarian cancer tissue samples. Detection of such parallel changes in pathway- and tissue-specific markers may prove a hallmark ready for application in reproductive disease diagnostic and therapeutic developments.

The effect of progestins on vascular endothelial growth factor, oestrogen receptor and progesterone receptor immunoreactivity and endothelial cell density in human endometrium

One common side-effect of contraceptive use is that it often leads to disrupted endometrial bleeding patterns. This may be due to changes in endothelial density and vessel integrity. To investigate whether the level of endometrial immunoreactive vascular endothelial growth factor (VEGF), oestrogen receptor or progesterone receptor (PR) have any role in this, women were treated with either Mircette, a monophasic oral contraceptive, or Implanon, a long-acting gestagen, and immunohistochemistry performed. In addition a small number of endometria were studied from women treated with levonorgestrel released from an intrauterine coil. During the untreated normal cycle, there was a significant increase in glandular VEGF immunoreactivity and a significant decrease in PR immunoreactivity in the midand late secretory phases compared to the proliferative phase. There was a significant positive correlation between stromal VEGF immunoreactivity and endothelial cell density. This correlation was also apparent during treatment with Implanon, but not with Mircette. Disrupted bleeding patterns were associated with Implanon and to a lesser extent with Mircette. Both contraceptives significantly reduced glandular VEGF immunoreactivity but the intrauterine treatment with levonorgestrel resulted in strong glandular epithelial staining and intense staining of decidualized stromal cells. Implanon significantly increased glandular PR staining, but Mircette significantly reduced stromal PR staining when compared to secretory phase before-treatment biopsies. There were no changes in endothelial cell density or glandular or stromal ER during the normal cycle, or with use of either contraceptive. There was no association of the parameters measured with bleeding patterns or histological category.

Angiogenic growth factor expression in placenta

New blood vessel growth is generally a rare event in the healthy adult. However, a notable exception to this is the female reproductive tract where cyclic angiogenesis occurs. Striking new vessel growth and remodeling also occurs during placentation; thus angiogenesis is essential for reproductive success. Vascular endothelial growth factor is a potent stimulator of this process and its production and action is tightly regulated. Indeed the placenta is a rich source of a soluble variant of the flt-1 receptor which seems to protect the placenta from the effects of excess vascular endothelial growth factor. The balance between new vessel growth (in the placental villi for example) and endothelial cell loss in the spiral arteries within the decidua is a delicate one. This is influenced by the local production of promotors and inhibitors of endothelial cell activation. Perturbation of this may lead to maternal pathology during pregnancy.

Vascular endothelial growth factor expression in human endometrium is regulated by hypoxia

Endometrial growth and repair after menstruation are associated with profound angiogenesis. Abnormalities in these processes result in excessive or unpredictable bleeding patterns and are common in many women. It is therefore important to understand which factors regulate normal endometrial angiogenesis. Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen that plays an important role in normal and pathological angiogenesis. In this study we show that expression of VEGF is regulated by hypoxia in human endometrium. Culture in vitro for 24 h under hypoxic conditions resulted in a 2- to 6-fold increase in VEGF secretion by both stromal and epithelial cells isolated from human endometrium. Quantitative RT-PCR was used to measure VEGF messenger ribonucleic acid (mRNA) levels in these cells. After hypoxia, VEGF mRNA levels increased 1.8-fold in stromal cells and 3.4-fold in glandular epithelial cells. The mRNA for each VEGF splice variant increased to an equal extent. The increase in VEGF secretion by stromal and epithelial cells in response to hypoxia was not altered by treatment at the same time with estradiol or progesterone. In situ hybridization of human endometrium during menstruation, when steroid levels are low but the tissue is subject to ischemia, showed strong hybridization to VEGF mRNA in both stromal and glandular cells. These results show that local factors, such as hypoxia, can regulate VEGF expression in the endometrium. This may play an important part in normal endometrial repair after menstruation. The secretion of VEGF by endometrial cells under hypoxic conditions may also be important in the pathogenesis of endometriosis, because it would be predicted to assist revascularization of desquamated endometrial explants when they attach at ectopic sites.

The effect of etonogestrel on VEGF, oestrogen and progesterone receptor immunoreactivity and endothelial cell number in human endometrium

Contraceptive use often leads to disrupted endometrial bleeding patterns in women. In this study, two different contraceptive regimes (Mircette, a monophasic oral contraceptive and Implanon, a long-acting gestagen) were used and their effects on the immunoreactivity of vascular endothelial growth factor (VEGF), oestrogen receptor (ER), progesterone receptor (PR) and endothelial cell number were determined. During the untreated normal cycle, there was a significant increase (P = 0.005) in glandular VEGF immunoreactivity and a significant decrease (P < 0.05) in PR immunoreactivity in the mid- and late secretory phases compared with the proliferative phase. There was a significant positive correlation (gamma = 0.38, P = 0.046) between stromal VEGF immunoreactivity and endothelial cell number. This correlation was also apparent during treatment with Implanon, but not with Mircette. Disrupted bleeding patterns were associated with Implanon and, to a lesser extent, with Mircette. Both contraceptives significantly reduced glandular VEGF immunoreactivity. Implanon significantly increased (P = 0.016) glandular PR staining, but Mircette significantly reduced (P = 0.027) stromal PR staining when compared with secretory before-treatment biopsies. There were no changes in endothelial cell number or glandular or stromal ER during the normal cycle, or with use of either contraceptive. There was no association between the parameters measured with bleeding patterns and histological category.

Alternative splicing of vascular endothelial growth factor (VEGF)-R1 (FLT-1) pre-mRNA is important for the regulation of VEGF activity

Angiogenesis is essential for normal mammalian development and is controlled by the local balance of pro- and antiangiogenic factors. Here we describe a novel mouse cDNA sequence encoding sFLT-1 that is a potent antagonist to vascular endothelial growth factor (VEGF) and show for the first time its in vivo production. In situ hybridization and Northern blot analysis with probes specific for sFLT-1 or FLT-1 showed that the relative abundance of their mRNAs changed markedly in spongiotrophoblast cells in the placenta as gestation progressed. On day 11 of pregnancy, sFLT-1 mRNA was undetectable but FLT-1 readily apparent, and by day 17 sFLT-1 mRNA was abundant but FLT-1 barely detectable. sFLT-1 was identified in conditioned medium of cultured placenta from day 17 pregnant mice and likely to be present in the circulation, as there is a substantial increase of VEGF-binding activity in the serum from day 13 of pregnancy, which coincides with the abundant sFLT-1 expression in placenta. Expression of sFLT-1 was also observed in adult lung, kidney, liver, and uterus. These data suggest a novel mechanism of regulation of angiogenesis by alternative splicing of FLT-1 pre-mRNA. Treatment of pregnant mice with exogenous VEGF from day 9 to 17 of pregnancy, which alters the ratio of VEGF to sFLT-1, resulted in an increase in the number of resorption sites and fibrin deposition in the placenta of ongoing pregnancies. These findings have important implications for understanding placental function and may be relevant in a range of disease states.

Localization of leukemia inhibitory factor and its receptor in human placenta throughout pregnancy

Mice in which the gene that encodes the receptor (R) for leukemia inhibitory factor (LIF) has been deleted show abnormal growth and development of the placenta. This indicates that LIF plays an important role in placental development. The expression of LIF-R and LIF was examined in human trophoblast and decidua using in situ hybridization and immunocytochemistry. LIF-R mRNA and immunoreactivity was localized in villous and extravillous trophoblast throughout pregnancy, and in endothelial cells of the fetal villi. Strong expression of mRNA encoding LIF was detected in decidual leukocytes, which are abundant at the implantation site. Extravillous trophoblast, which invades the maternal decidua, therefore expresses LIF-R as it moves past decidual leukocytes, which express LIF mRNA. The effect of LIF on cultured human trophoblast was examined in vitro. Recombinant human LIF had no effect on [3H]thymidine incorporation by purified extravillous trophoblast, nor on expression of integrins alpha1, alpha5, or beta1 by isolated trophoblast. These results identify fetal endothelial cells and all cells of the trophoblast lineage as targets for the action of LIF in human placenta. Although its effects on trophoblast are not yet clear, LIF appears to mediate interactions between maternal decidual leukocytes and invading trophoblast. LIF may also play a critical role in controlling angiogenesis in the placental villi, since human fetal endothelial cells express LIF-R, and mice lacking a functional LIF receptor gene show altered vascular development in the placenta.

A vascular endothelial growth factor antagonist is produced by the human placenta and released into the maternal circulation

Vascular endothelial growth factor (VEGF) is a potent secreted factor that promotes angiogenesis and maintains the integrity of the endothelium. Levels of VEGF are increased in many tumors and are elevated in women with pre-eclampsia, a serious disease of pregnancy. Here we show by in situ hybridization that the trophoblast contains the mRNA encoding a soluble version of the VEGF receptor known as Flt-1 (sFlt-1: initially described by Kendall and Thomas, PNAS 90:10705-10709). Binding assays and Western blotting of villus-conditioned media confirmed the production of sFlt-1. Serum from pregnant women was found to contain a VEGF-binding protein that was not present in serum from men or nonpregnant women. As determined by heparin affinity, column fractionation, and cross-linking, this protein was identical to sFlt-1. Taken together, these results show that the placenta secretes sFlt-1, which would be expected to be a VEGF antagonist. This is the first report of production of the sFlt-1 receptor in vivo, and it reveals a new mechanism for naturally regulating this potent angiogenic agent. The presence of such an antagonist suggests that regulation of VEGF action is essential to successful pregnancy. This has important implications for the activity of VEGF locally and systemically in other conditions.

Comparison of expression patterns for placenta growth factor, vascular endothelial growth factor (VEGF), VEGF-B and VEGF-C in the human placenta throughout gestation

Angiogenesis and vascular transformation are important processes in the normal development of the placenta. Vascular endothelial growth factor (VEGF) is a potent angiogenic growth factor and is thought to be important for placental development. Recently several new members of this family have been described. In this study we used in situ hybridisation to localise which cells in the placenta expressed mRNA for VEGF, placenta growth factor (PlGF), VEGF-B and VEGF-C. We were unable to find any message for either VEGF-B or VEGF-C in the placenta, suggesting that only low levels are produced which this method was unable to detect. The mRNA encoding VEGF was found to be produced by cells within the villous mesenchyme, decidual macrophages and decidual glands but, in contrast to our previous findings, not by trophoblast. The mRNA encoding PlGF was produced in large amounts by villous cytotrophoblast, syncytiotrophoblast and extravillous trophoblast. The mRNAs encoding VEGF and PlGF were thus not co-localised and it appears that there is unlikely to be any significant production of VEGF/PlGF heterodimer in the placenta.

Hepatocyte growth factor levels during normal and intra-uterine growth-restricted pregnancies

Hepatocyte growth factor (HGF), also known as scatter factor, binds the c-met receptor. It has been shown to be involved in mesenchyme-epithelial interactions. HGF is produced by the villous mesenchyme of the placenta throughout pregnancy and its receptor located on the villous cytotrophoblast cells. In this study the levels of HGF were measured in consecutive samples of plasma taken from pregnant women. Normal pregnancies were compared with intrauterine growth restricted (IUGR) pregnancies (below the third centile). In both groups, the levels of HGF were found to increase significantly as pregnancy progressed and then fall post partum. There was a considerable amount of variation found between individual women but no significant difference (P=0.65) between the normal and IUGR pregnancies.

Expression and localization of the Th2-type cytokine interleukin-13 and its receptor in the placenta during human pregnancy

PROBLEM

To investigate the expression of the Th2-type cytokine interleukin (IL)-13 and its receptor in human placenta during gestation.

METHOD OF STUDY

Expression of IL-13 and its receptor was analyzed by reverse transcriptase (RT)-polymerase chain reaction (PCR), in situ hybridization and immunohistochemistry using human placental samples.

RESULTS

IL-13 mRNA was detected by RT-PCR in placental extracts from all stages of gestation. In situ hybridization revealed IL-13 mRNA in first trimester cytotrophoblast and syncytiotrophoblast. Few positive cells were found within decidual sections from the same pregnancy. Immunohistochemistry revealed a similar pattern to in situ hybridization. This was largely absent in second- and third-trimester placentae. IL-13 receptor alpha chain (IL-13R alpha) was detected by immunofluorescence on the surface of leukocytes in first-trimester villous core and decidua.

CONCLUSIONS

The expression of IL-13 is spatially and temporally regulated in the placenta, and associated with the close proximity of a receptor-bearing target leukocyte population.

The role of leukemia inhibitory factor and interleukin-6 in human reproduction

There is now strong evidence that many of the actions of steroids in controlling reproduction are mediated by locally acting factors such as growth factors and cytokines. These have been shown to act both in an autocrine and paracrine manner to regulate preimplantation embryo development and migration which is necessary for placental development. The creation of mouse strains lacking genes for receptors or growth factors has proved important in defining which of these are essential in reproduction in this species and those that play a lesser role. Using this approach, a lack of leukemia inhibitory factor (LIF) in the murine endometrium has been shown to result in failed implantation. Evidence from infertile women supports the notion that abnormal expression of LIF, or the related cytokine interleukin-6 (IL-6) in the endometrium may underlie some forms of human infertility. This offers the opportunity for therapeutic intervention, if levels of these cytokines can be altered in a specific and controlled way. The recently described method of delivery of genes to the uterine epithelium provides a powerful new approach by which this could be achieved. The ability to regulate the function of specific genes in the endometrium by direct gene transfer raises the prospect of novel opportunities for therapeutic intervention.

Expression and localization of the vascular endothelial growth factor family in ovarian epithelial tumors

Vascular endothelial growth factor (VEGF) is an angiogenic factor secreted by various tumors, including epithelial tumors of the ovary, and is involved in tumor progression and maintenance. The significance and function of other members of the VEGF family in the ovary has not yet been elucidated. In the present study, we have defined the expression of mRNA encoding VEGF-B, VEGF-C, and placenta growth factor (PIGF), compared with that of VEGF mRNA, in normal ovary and a range of ovarian epithelial tumors. Analysis by reverse transcription-PCR indicated that mRNA encoding VEGF (isoforms 121 and 165), VEGF-B (isoforms 167 and 186), and VEGF-C, but not PIGF, were present in all ovarian tissues examined. By in situ hybridization, neither VEGF-C nor PIGF transcripts were detected in any of the samples. The expression pattern of VEGF-B mRNA was generally similar to that of VEGF mRNA, in that transcripts were readily detected in the epithelial cells of all histologic types of ovarian carcinoma, but could not be detected in normal or benign tumor epithelium. Specific differences in the expression of the two genes were noted in areas of tumor necrosis, in which the expression of VEGF mRNA, but not VEGF-B mRNA, was further enhanced, and in a sample in which VEGF-B mRNA was strongly expressed in tumor-associated macrophages that did not hybridize with the riboprobe to VEGF mRNA. These results imply that a second member of the VEGF family, VEGF-B, may play a significant role in the angiogenesis, progression, and maintenance of ovarian carcinomas.

Cyclooxygenase-1 and -2 in human placenta and placental bed after normal and pre-eclamptic pregnancies

In pre-eclampsia, the ratio of prostacyclin:thromboxane production rate is decreased favouring the vasoconstrictive thromboxane. One of the rate-limiting steps in prostaglandin synthesis is cyclooxygenase (COX) activity. Therefore, we investigated the expression of COX-1 and COX-2 in human placenta and placental bed. Tissue specimens from the 29th to 40th week of pregnancy were obtained from Caesarean sections after uncomplicated and pre-eclamptic pregnancies before the onset of labour. COX-1 and COX-2 were localized immunohistochemically with the identification of positive cells by double immunofluorescence staining. The protein and mRNA levels were analysed by immunoblotting and quantitative reverse transcriptase-polymerase chain reaction. Expression of both COX-1 and COX-2 could be observed in placenta and placental bed. COX-1-like immunoreactivity was observed in most cell types with strongest staining in macrophages. Only macrophages, endothelium, vascular leiomyocytes and fibroblasts stained positively for COX-2. In placenta, COX-1 and -2 expression was unchanged after pre-eclampsia. In placental bed, protein and mRNA levels of COX-1 were increased in the pre-eclamptic group (P < 0.05), whereas COX-2 expression did not differ significantly from normal pregnancies. An increased expression of COX-1 could be involved in the pathophysiology of pre-eclamptic changes within the placental bed. A therapy with drugs inhibiting COX-1 might be beneficial in this condition.

Decreased levels of the potent regulator of monocyte/macrophage activation, interleukin-13, in the peritoneal fluid of patients with endometriosis

Endometriosis is characterized by an increase in the number, activation and secretory activity of peritoneal fluid macrophages. Factors regulating the activation of these cells may be important in the pathophysiology of this disease. In this study we measured by enzyme-linked immunosorbent assay the concentrations of the macrophage inhibitory factor interleukin (IL)-13 in the peritoneal fluid of women with and without endometriosis. It was found that women with endometriosis had significantly lower amounts of IL-13 (95 +/- 9.8 pg/ml) in peritoneal fluid, compared with women without endometriosis (115 +/- 30 pg/ml) (P < 0.01). No cycle-specific variation was evident for either group. Another macrophage inhibitory interleukin (IL-10) was also measured, but no differences between women with (16.1 +/- 13.2 pg/ml) or without (10.3 +/- 5.6 pg/ml) endometriosis were seen. The immunolocalization of IL-13 was assessed in eutopic and ectopic endometrium and in isolated peritoneal fluid cells. Glandular epithelial cells and stromal cells in both eutopic and ectopic endometrium were immunopositive for IL-13. No cycle-specific differences in the immunolocalization of IL-13 were seen. In conclusion, the reduced amounts of IL-13 in the peritoneal fluid of women with endometriosis may lead to a lack of suppression of macrophage activation, thereby contributing to the overall pathogenesis of this disease.

Isolation of macrophages (Hofbauer cells) from human term placenta and their prostaglandin E2 and thromboxane production

Placental macrophages (Hofbauer cells) are located close to trophoblast cells and fetal capillaries, which makes them ideal candidates for involvement in regulatory processes within the villous core. Their production of various cytokines and prostaglandin (PG) synthesizing enzymes has previously been shown immunohistochemically. Hofbauer cells were isolated from human placenta after term deliveries by Ficoll and Percoll gradient centrifugation. Remaining trophoblast cells were removed with anti-epidermal growth factor (EGF)-receptor-coated Dynabeads followed by differential adherence. The identity of isolated cells was investigated by immunohistochemistry with anti-CD68, which showed that >90% cells were positive. After a 36 h recovery period in either 20% O2 or 5% O2, fresh medium was applied and PGE2 and thromboxane (TXA2) production analysed by enzyme immunoassay at 4, 8, and 24 h. PGE2 and TXA2 were both produced by placental macrophages with PGE2 synthesis being predominant. Concentrations of both could be stimulated by lipopolysaccharide with maximum effect after 24 h. Culture in low oxygen caused decreased PGE2 concentrations, whereas TXA2 production remained unchanged. In conclusion, the presented isolation protocol allows further study of Hofbauer cell function. This study also presents novel findings regarding the prostaglandin production of term Hofbauer cells under normal and hypoxic conditions.

Distribution of the A and B forms of the progesterone receptor messenger ribonucleic acid and protein in uterine leiomyomata and adjacent myometrium

The two forms of the progesterone receptor, PR-A and PR-B, are independently regulated at the transcriptional level, and show distinct responses to progesterone antagonists. We were interested in possible differences in the PR-A to PR-B ratio between uterine myometrium and leiomyomata (fibroid), that might influence the response of fibroids to progesterone agonists and antagonists, and thus have consequences for the treatment of this condition. Fibroid and adjacent normal myometrium were obtained from 11 women undergoing hysterectomy. Immunohistochemistry using a monoclonal antibody which recognizes both PR-A and PR-B showed exclusively nuclear staining, and this was stronger in the leiomyomata than in adjacent myometrium. An antibody specific for PR-B gave fainter staining of both tissues. Western blotting confirmed a higher concentration of PR in leiomyomata than myometrium in eight out of 11 cases. In all cases both forms were present, with a consistent dominance of PR-A over PR-B. However an RNase protection assay showed that there was no difference between the concentrations of mRNA encoding PR-A and PR-B, or between the mRNA concentrations in leiomyomata and normal myometrium. We conclude that the observed differences between the levels of immunoreactive PR in leiomyomata and myometrium may result from post-translational control, and support the use of progesterone antagonists in the treatment of leiomyomata.

Immunolocalization of the apoptosis regulating proteins Bcl-2 and Bax in human endometrium and isolated peritoneal fluid macrophages in endometriosis

Endometriosis, a debilitating disease associated with infertility, is characterized by the prolonged presence of ectopic endometrial tissue and the involvement of activated peritoneal fluid macrophages. Apoptosis, which occurs in both endometrium and peritoneal fluid macrophages, is controlled in part by members of the Bcl-2/Bax family of proteins. Here, through immunohistochemical staining, we investigated the Bcl-2/Bax status in endometrium and peritoneal fluid macrophages in endometriosis. Bcl-2/Bax immunoreactivity was found predominantly in the glandular epithelial cells, mainly during the proliferative phase of the menstrual cycle for Bcl-2 but throughout the entire menstrual cycle for Bax. Ectopic endometrium contained a population of Bcl-2 positive. Bax negative tissue macrophages. Fluorescence-activated cell sorting of isolated peritoneal fluid macrophages showed that women with endometriosis had a significantly higher proportion of Bcl-2 positive macrophages than the non-endometriotic group. The proportion of Bax positive peritoneal fluid macrophages was significantly elevated in women without endometriosis. The increased proportion of Bcl-2 positive macrophages found in women with endometriosis may predispose these cells to resist apoptosis. The continued survival of these active cells could have important consequences for the survival and proliferation of the ectopic endometrial tissue.