The effects of angiogenic growth factors on extravillous trophoblast invasion and motility

Pathomechanisms of Prenatally Programmed Adult Diseases

Based on epidemiological observations Barker et al. put forward the hypothesis/concept that an adverse intrauterine environment (involving an insufficient nutrient supply, chronic hypoxia, stress, and toxic substances) is an important risk factor for the development of chronic diseases later in life. The fetus responds to the unfavorable environment with adaptive reactions, which ensure survival in the short run, but at the expense of initiating pathological processes leading to adult diseases. In this review, the major mechanisms (including telomere dysfunction, epigenetic modifications, and cardiovascular-renal-endocrine-metabolic reactions) will be outlined, with a particular emphasis on the role of oxidative stress in the fetal origin of adult diseases.

Evolutionary divergence of embryo implantation in primates

Implantation of the conceptus into the uterus is absolutely essential for successful embryo development. In humans, our understanding of this process has remained rudimentary owing to the inaccessibility of early implantation stages. Non-human primates recapitulate many aspects of human embryo development and provide crucial insights into trophoblast development, uterine receptivity and embryo invasion. Moreover, primate species exhibit a variety of implantation strategies and differ in embryo invasion depths. This review examines conservation and divergence of the key processes required for embryo implantation in different primates and in comparison with the canonical rodent model. We discuss trophectoderm compartmentalization, endometrial remodelling and embryo adhesion and invasion. Finally, we propose that studying the mechanism controlling invasion depth between different primate species may provide new insights and treatment strategies for placentation disorders in humans. This article is part of the theme issue 'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom'.

Cortisol Dose-Dependently Impairs Migration and Tube-like Formation in a Trophoblast Cell Line and Modulates Inflammatory and Angiogenic Genes

Several stimuli can change maternal hormone levels during pregnancy. These changes may affect trophoblastic cells and modulate the development of the embryo and the placental tissue itself. Changes in cortisol levels are associated with impaired trophoblast implantation and function, in addition to other pregnancy complications. This study aims to analyze the effects of low and high doses of cortisol on an extravillous trophoblast cell line, and the effects of various exposures to this hormone. SGHPL-4 cells were treated with cortisol at five doses (0-1000 nM) and two exposures (continuous: 24 h/day; and intermittent: 2 h/day). In intermittent treatment, cortisol acted mainly as an anti-inflammatory hormone, repressing gene expression of kinin B1 receptors, interleukin-6, and interleukin-1β. Continuous treatment modulated inflammatory and angiogenic pathways, significantly repressing angiogenic factors and their receptors. Cortisol affected cell migration and tube-like structures formation. In conclusion, both continuous and intermittent exposure to cortisol repressed the expression of inflammatory genes, while only continuous exposure repressed the expression of angiogenic genes, suggesting that a sustained increase in the levels of this hormone is more harmful than a high short-term increase. Cortisol also impaired tube-like structures formation, and kinin receptors may be involved in this response.

Decreased expression of annexin A2 and loss of its association with vascular endothelial growth factor leads to the deficient trophoblastic invasion in preeclampsia

OBJECTIVES

Preeclampsia (PE) remains the major cause for maternal and foetal mortality and morbidity. Invasion of endovascular trophoblast and remodelling of spiral artery are crucial actions of normal placental development. Non-fulfilment of these processes plays a leading role in the development of preeclampsia. Vascular endothelial growth factor (VEGF) is produced by extravillous trophoblastic tissue and decidual cell population is a well-known angiogenic growth which plays a fundamental role in placental pathogenesis of PE. Annexin A2 (ANXA2) is a profibrinolytic protein receptor required for plasminolysis, which is an important step in the formation of new blood vessel along with VEGF. Role of ANXA2 is poorly studied in context with human reproductive disease like preeclampsia. The purpose of the present study is to examine the expression and association of VEGF and ANXA2 in the term placentas of pregnancies with and without PE.

METHODS

The study group comprised of placental tissues procured from gestations with PE (n=30) and without (n=20) PE. The expression of VEGF and ANXA2 in the placental villous tissue was evaluated quantitatively by means of IHC, western blotting and reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

Our IHC, western blotting and RT-PCR analysis illustrated the significant decrease in the expression of VEGF and ANXA2 in PE group compared with the normotensive control group (p<0.005). We observed statistically significant positive correlation among the expression of ANXA2 and VEGF in placentas of normotensive control group (p<0.0001).

CONCLUSIONS

The diminished expression of VEGF and ANXA2 in placenta may be associated with the defective angiogenesis and which may possibly play a vital role in PE pathogenesis.

miR-219a suppresses human trophoblast cell invasion and proliferation by targeting vascular endothelial growth factor receptor 2 (VEGFR2)

OBJECTIVE

Vascular endothelial growth factor (VEGF) plays a critical role in regulating trophoblast cell invasion and proliferation, involved in a variety of pregnancy complications, such as spontaneous abortion and pre-eclampsia. Numerous studies have revealed that microRNAs (miRNAs) are participated in a series of molecular processes that regulate cell function, such as cell invasion, proliferation, and apoptosis. Vascular endothelial growth factor receptor 2 (VEGFR2), a receptor of VEGF, has been shown to be involved in trophoblast function. However, the relation between miRNA and VEGFR2 and their role in trophoblast function remain to be elucidated.

METHODS

The effect of miR-219a on the trophoblast function has been explored using luciferase reporter, transwell, qRT-PCR, western blot, bromodeoxyuridine (BrdU), ELISA, immunofluorescent staining, and tube formation assays.

RESULTS

In the current study, we observed that through targeted inhibition of VEGFR2 expression by miR-219a, the function of VEGFR2 as well as the downstream PI3K/AKT/NF-κB signaling pathway were suppressed, leading to suppression of trophoblastic proliferation and invasion. Moreover, upregulation of VEGFR2 restored the miR-219a-inhibited cell proliferation, invasion, and tube formation.

CONCLUSIONS

These results revealed that miR-219a played crucial roles in negatively regulating trophoblastic proliferation and invasion by suppression of the PI3K/AKT/NF-κB signaling pathway by targeting VEGFR2, therefore serving as a potential treatment method for the complications of pregnancy caused by trophoblastic dysregulation.

Preeclampsia: Linking Placental Ischemia with Maternal Endothelial and Vascular Dysfunction

Preeclampsia (PE), a hypertensive disorder, occurs in 3% to 8% of pregnancies in the United States and affects over 200,000 women and newborns per year. The United States has seen a 25% increase in the incidence of PE, largely owing to increases in risk factors, including obesity and cardiovascular disease. Although the etiology of PE is not clear, it is believed that impaired spiral artery remodeling of the placenta reduces perfusion, leading to placental ischemia. Subsequently, the ischemic placenta releases antiangiogenic and pro-inflammatory factors, such as cytokines, reactive oxygen species, and the angiotensin II type 1 receptor autoantibody (AT1-AA), among others, into the maternal circulation. These factors cause widespread endothelial activation, upregulation of the endothelin system, and vasoconstriction. In turn, these changes affect the function of multiple organ systems including the kidneys, brain, liver, and heart. Despite extensive research into the pathophysiology of PE, the only treatment option remains early delivery of the baby and importantly, the placenta. While premature delivery is effective in ameliorating immediate risk to the mother, mounting evidence suggests that PE increases risk of cardiovascular disease later in life for both mother and baby. Notably, these women are at increased risk of hypertension, heart disease, and stroke, while offspring are at risk of obesity, hypertension, and neurological disease, among other complications, later in life. This article aims to discuss the current understanding of the diagnosis and pathophysiology of PE, as well as associated organ damage, maternal and fetal outcomes, and potential therapeutic avenues. © 2021 American Physiological Society. Compr Physiol 11:1315-1349, 2021.

Effect of Placental Growth Factor on Trophoblast-Endothelial Cell Interactions In Vitro

Placental growth factor (PlGF) is an important angiogenic factor which has an emerging role in the clinical management of suspected preeclampsia. The role of PlGF in normal placental development is not completely understood and it is uncertain whether PlGF influences trophoblast and endothelial cell interactions central to uterine spiral artery remodelling, especially in variable oxygen conditions. A two-cell model of endovascular invasion was used. Tissue culture plates were coated with Matrigel™, on which fluorescent-labelled uterine microvascular endothelial cells (1 × 10⁵/well) and HTR8/SVNeo cells were co-cultured (1 × 10⁵/well) for 20 h. Co-cultures were treated with recombinant human PlGF (rhPlGF) (10 or 100 ng/mL) and incubated at either 21% O₂ or 2% O₂. Images were captured by fluorescence microscopy and analysed using ImageJ (n = 7). Data was analysed using SPSSv24. Treatment with rhPlGF did not improve integration in co-cultures irrespective of oxygen conditions but increased proliferation in 2% O₂ of both trophoblast and endothelial cells. Expression of angiogenic factors VEGF, sFLT-1, PlGF and CXCL12 in both co-cultures and in isolated trophoblast cells was not altered by rhPlGF treatment. Expression of TLR-3 mRNA in co-cultures was increased by rhPlGF 100 ng/mL at 21% O₂ (p = 0.03). PlGF contributes to trophoblast and endothelial cell proliferation in the setting of physiological hypoxia but does not influence trophoblast and endothelial cell interactions in an in vitro model of spiral artery remodelling. Upregulation of TLR-3 expression in co-cultures may indicate a role for PlGF in the placental inflammatory response.

MicroRNAs in Uteroplacental Vascular Dysfunction

Pregnancy complications of preeclampsia and intrauterine growth restriction (IUGR) are major causes of maternal and perinatal/neonatal morbidity and mortality. Although their etiologies remain elusive, it is generally accepted that they are secondary to placental insufficiency conferred by both failure in spiral artery remodeling and uteroplacental vascular malfunction. MicroRNAs (miRNAs) are small no-coding RNA molecules that regulate gene expression at the post-transcriptional level. Increasing evidence suggests that miRNAs participate in virtually all biological processes and are involved in numerous human diseases. Differentially expressed miRNAs in the placenta are typical features of both preeclampsia and IUGR. Dysregulated miRNAs target genes of various signaling pathways in uteroplacental tissues, contributing to the development of both complications. In this review, we provide an overview of how aberrant miRNA expression in preeclampsia and IUGR impacts the expression of genes involved in trophoblast invasion and uteroplacental vascular adaptation.

A Rapid Method for Label-Free Enrichment of Rare Trophoblast Cells from Cervical Samples

Extravillous trophoblasts (EVTs) have the potential to provide the entire fetal genome for prenatal testing. Previous studies have demonstrated the presence of EVTs in the cervical canal and the ability to retrieve a small quantity of these cells by cervical sampling. However, these small quantities of trophoblasts are far outnumbered by the population of cervical cells in the sample, making isolation of the trophoblasts challenging. We have developed a method to enrich trophoblast cells from a cervical sample using differential settling of the cells in polystyrene wells. We tested the addition of small quantities of JEG-3 trophoblast cell line cells into clinical samples from standard Pap tests taken at 5 to 20 weeks of gestation to determine the optimal work flow. We observed that a 4 min incubation in the capture wells led to a maximum in JEG-3 cell settling on the surface (71 ± 10% of the initial amount added) with the removal of 91 ± 3% of the cervical cell population, leading to a 700% enrichment in JEG-3 cells. We hypothesized that settling of mucus in the cervical sample affects the separation. Finally, we performed a proof-of-concept study using our work flow and CyteFinder cell picking to verify enrichment and pick individual JEG-3 and trophoblast cells free of cervical cells. Ultimately, this work provides a rapid, facile, and cost-effective method for enriching native trophoblasts from cervical samples for use in subsequent non-invasive prenatal testing using methods including single cell picking.

Vascular endothelial growth factor C participates in regulation of maspin in extravillous trophoblast cell migration and invasion

Mammary serine protease inhibitor (maspin ; also known as serpin family B member 5 (SERPINB5)) plays a vital role in regulating the biological functions of extravillous trophoblast (EVT) cells, but the mechanism remains unclear. Vascular endothelial growth factor (VEGF ) C is a signature angiogenic molecule expressed and secreted by first-trimester trophoblasts, and bioinformatics analyses has revealed upregulation of VEGFC in pre-eclampsia. The aim of this study was to explore whether maspin regulates EVT cells by regulating the expression of VEGFC . Reverse transcription-polymerase chain reaction and western blotting were used to investigate the effects of hypoxia on the expression of VEGFC in EVT cells. Cells were treated with recombinant (r) maspin and decitabine (to selectively inhibit DNA methyltransferases and then upregulate maspin gene expression), and the effects on VEGFC expression evaluated. In addition, the effects of rVEGFC on the biological functions of EVT cells invitro were evaluated using cell migration and invasion assays. Hypoxia increased the expression of VEGFC in EVT cells. rMaspin upregulated the expression of VEGFC in normoxic EVT cells, and downregulated the expression of VEGFC in hypoxic EVT cells at 24h. Decitabine increased VEGFC expression in normoxic EVT cells, but had no significant effect on VEGFC expression in hypoxic EVT cells. rVEGFC promoted the migration and invasion of normoxic EVT cells and inhibited the invasion of hypoxic EVT cells. These results suggest that VEGFC is involved in the regulation of maspin in EVT cell migration and invasion. However, other molecular mechanisms may be involved and require further investigation.

The interaction effect of angiogenesis and endothelial dysfunction-related gene variants increases the susceptibility of recurrent pregnancy loss

PURPOSE

The role of genetic polymorphisms in the pathogenesis of recurrent pregnancy loss (RPL) has been studied intensively. Complex diseases, including miscarriage, are believed to have a polygenic basis, and gene-gene interactions can play a significant role in the etiology of the disease. This study was conducted to investigate the association of gene-gene interactions with angiogenesis, endothelial dysfunction-related gene polymorphisms, and RPL.

METHODS

A case-control study was conducted with 253 unrelated RPL patients with 2 or more spontaneous pregnancy losses and 339 healthy women with no history of pregnancy complications. Genotyping of single-nucleotide polymorphisms (SNPs) was performed using real-time polymerase chain reaction (real-time PCR), restriction fragment length polymorphism (RFLP), or allele-specific polymerase chain reaction methods.

RESULTS

The genotypes 677TT of the MTHFR gene, 936TT, 936CT, and 634CC, 634GC of the VEGF gene, and allele 894T of the NOS3 gene were associated with a predisposition to RPL in the Russian population. A significant role of additive and epistatic effects in the gene-gene interactions of the SNPs of SERPINE-1, ACE, NOS3, MTHFR, and VEGF genes in RPL was demonstrated.

CONCLUSIONS

The results showed that gene-gene interactions are important for RPL susceptibility. Additionally, analysis of the genotype combinations of several allelic variants provides more information on RPL risk than analysis of independent polymorphic markers.

The association of second trimester biomarkers in amniotic fluid and fetal outcome

Objective: To identify the level of amniotic fluid lactate (AFL), placental growth factor (PLGF), and vascular endothelial growth factor (VEGF) at second trimester amniocentesis, and to compare levels in normal pregnancies with pregnancies ending in a miscarriage, an intrauterine growth restricted fetus (IUGR) or decreased fetal movements. Study design: A prospective cohort study. Amniotic fluid was consecutively collected at amniocentesis in 106 pregnancies. Fetal wellbeing at delivery was evaluated from medical files and compared with the levels of AFL, VEGF, and PLGF at the time of amniocentesis. Results: The median level of AFL was 6.9 mmol/l, VEGF 0.088 pg/ml, and PLGF 0.208 pg/ml. The median levels of AFL in pregnancies ended in miscarriage were significantly higher (10.7 mmol/l) compared to those with a live new-born (6.9 mmol/L, p = .02). The levels of VEGF (p = .2) and PLGF (p = .7) were not affected. In pregnancies with an IUGR, the median level of AFL was higher compared to those with normal fetal growth (p = .003). No differences VEGF (p = .5), but significant lower PLGF were found in IUGR pregnancies (p = .03). Conclusions: Pregnancies ending in a miscarriage or with IUGR had significantly higher median values of AFL but lower values of PLGF in the amniotic fluid at the time of second trimester amniocentesis compared to normal pregnancies.

The association of maternal thyroid function with placental hemodynamics

STUDY QUESTION

What is the clinical association of maternal thyroid function with placental hemodynamic function?

SUMMARY ANSWER

A higher free thyroxine (FT4) concentration in early pregnancy is associated with higher placental vascular resistance.

WHAT IS KNOWN ALREADY

Suboptimal placental function is associated with preeclampsia (which, in turn, further deteriorates placental hemodynamics and impairs the fetal blood supply), fetal growth restriction and premature delivery. Studies have suggested that thyroid hormone (TH) has a role in placental development through effects on trophoblast proliferation and invasion.

STUDY DESIGN, SIZE, DURATION

This study was embedded in The Generation R cohort, a population-based prospective study from early fetal life onwards in Rotterdam, the Netherlands. In total, 7069 mothers with expected delivery date between April 2002 and January 2006 were enrolled during early pregnancy.

PARTICIPANTS/MATERIALS, SETTING, METHOD

Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) concentrations were measured during early pregnancy (median 13.4 weeks, 95% range 9.7-17.6 weeks). Placental function was assessed by Doppler ultrasound via measurement of arterial vascular resistance, i.e. umbilical artery pulsatility index (PI) and uterine artery resistance index (RI) (both measured twice, between 18-25th and after 25th gestational weeks) and the presence of uterine artery notching (once after the 25th gestational week) in 5184 pregnant women.

MAIN RESULTS AND THE ROLE OF CHANCE

FT4 was positively linearly associated with umbilical artery PI in the second and third trimesters as well as with uterine artery RI in the second trimester and the risk of uterine artery notching in the third trimester (P < 0.05 for all). The association of thyroid function with preeclampsia and birth weight was partially mediated through changes in placental function, with the percentages of mediated effects being 10.4% and 12.5%, respectively.

LIMITATIONS, REASONS FOR CAUTION

A potential limitation is the availability of only a single time point for TH measurements and different numbers of missing placental ultrasound measurements for the adverse outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

A higher FT4 concentration in early pregnancy is associated with higher vascular resistance in the second and third trimesters in both the maternal and fetal placental compartment. These effects on placental function might explain the association of FT4 with adverse pregnancy outcomes, including preeclampsia and fetal growth restriction.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a fellowship from ERAWEB, a project funded by the European Commission (to M.B.) and by clinical fellowship from The Netherlands Organization for Health Research and Development (ZonMw), Project 90700412 (to R.P.P.). The authors have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Leptin, leptin receptors and hypoxia-induced factor-1α expression in the placental bed of patients with and without preeclampsia during pregnancy

The mechanism underlying the pathogenesis of preeclampsia (PE) has been previously investigated but remains to be elucidated. Among numerous biomarkers that are associated with the pathogenesis of PE, leptin is most frequently investigated. Although studies concerning the association between PE and the expression of leptin in the serum and placenta have been conducted, the results are conflicting and inconsistent. Furthermore, the expression of leptin and its receptors in the placental bed and their association with PE, to the best of our knowledge, has not been previously reported. Therefore, to determine the association between the expression of leptin and its receptor, and pathogenesis and onset period of PE, placental bed tissues were obtained from cesarean section deliveries. The mRNA and protein expression levels of leptin and its receptor were investigated in normal pregnancies (n=18), pregnancies complicated with early‑onset PE (n=9) and late‑onset PE (n=9) by reverse transcription‑quantitative polymerase chain reaction and western blotting, respectively. The results demonstrated that the mRNA and protein expression of leptin in the placental bed was significantly increased in the PE groups compared with normal controls and was associated with the onset period of PE. Furthermore, as evidenced by immunostaining, leptin was upregulated in endothelial cells of the placental bed in the PE groups, with a particularly strong upregulation in activated endothelial cells from patients with early‑onset PE. The results of the present study indicate that altered expression of leptin in the placental bed may contribute to the pathogenesis of PE.

Decreased PGF may contribute to trophoblast dysfunction in fetal growth restriction

Fetal growth restriction (FGR) threatens perinatal health and is correlated with increased incidence of fetal original adult diseases. Most cases of FGR were idiopathic, which were supposed to be associated with placental abnormality. Decreased circulating placental growth factor (PGF) was recognized as an indication of placental deficiency in FGR. In this study, the epigenetic regulation of PGF in FGR placentas and the involvement of PGF in modulation of trophoblast activity were investigated. The expression level of PGF in placental tissues was determined by RT-qPCR, immunohistochemistry and ELISA. DNA methylation profile of PGF gene was analyzed by bisulfite sequencing. Trophoblastic cell lines were treated with ZM-306416, an inhibitor of PGF receptor FLT1, to observe the effect of PGF/FLT1 signaling on cell proliferation and migration. We demonstrated that PGF was downregulated in placentas from FGR pregnancies compared with normal controls. The villous expression of PGF was positively correlated with placental and fetal weight. The CpG island inside PGF promoter was hypomethylated without obvious difference in both normal and FGR placentas. However, the higher DNA methylation at another CpG island downstream exon 7 of PGF was demonstrated in FGR placentas. Additionally, we found FLT1 was expressed in trophoblast cells. Inhibition of PGF/FLT1 signaling by a selective inhibitor impaired trophoblast proliferation and migration. In conclusion, our data suggested that the PGF expression was dysregulated, and disrupted PGF/FLT1 signaling in trophoblast might contribute to placenta dysfunction in FGR. Thus, our results support the significant role of PGF in the pathogenesis of FGR.

Inflammatory biomarkers and spontaneous preterm birth among obese women

OBJECTIVE

To identify associations between second-trimester serum inflammatory biomarkers and preterm birth among obese women.

METHODS

In this nested case-control study, we compared 65 serum inflammatory biomarkers in obese women whose pregnancies resulted in early spontaneous preterm birth (<32 weeks gestation, n = 34) to obese women whose pregnancies resulted in term birth (n = 34). These women were selected from a larger population-based California cohort. Random forest and classification and regression tree techniques were employed to identify biomarkers of importance, and adjusted odds ratios (aORs) and 95% confidence intervals (CI) were estimated using logistic regression.

RESULTS

Random forest and classification and regression tree techniques found that soluble vascular endothelial growth factor receptor-3 (sVEGFR3), soluble interleukin-2 receptor alpha-chain (sIL-2RA) and soluble tumor necrosis factor receptor-1 (sTNFR1) were related to preterm birth. Using multivariable logistic regression to compare preterm cases and term controls, decreased serum levels of sVEGFR3 and increased serum levels of sIL-2RA and sTNFR1 were associated with increased risk of preterm birth among obese women, aOR = 3.2 (95% CI: 1.0-9.9), aOR = 2.8 (95% CI: 0.9-9.0), and aOR = 4.1 (95% CI: 1.2-14.1), respectively.

CONCLUSIONS

In this pilot study, we identified three serum biomarkers indicative of inflammation to be associated with spontaneous preterm birth among obese women: sVEGFR3, sIL-2RA and sTNFR1.

STAT3 and ERK Signaling Pathways Are Implicated in the Invasion Activity by Oncostatin M through Induction of Matrix Metalloproteinases 2 and 9

PURPOSE

Our previous studies have shown that oncostatin M (OSM) promotes trophoblast invasion activity through increased enzyme activity of matrix metalloproteinase (MMP)-2 and -9. We further investigated OSM-induced intracellular signaling mechanisms associated with these events in the immortalized human trophoblast cell line HTR8/SVneo.

MATERIALS AND METHODS

We investigated the effects of OSM on RNA and protein expression of MMP-2 and -9 in the first-trimester extravillous trophoblast cell line (HTR8/SVneo) via Western blot. The selective signal transducer and activator of transcription (STAT)3 inhibitor, stattic, STAT3 siRNA, and extracellular signal-regulated kinase (ERK) siRNA were used to investigate STAT3 and ERK activation by OSM. The effects of STAT3 and ERK inhibitors on OSM-induced enzymatic activities of MMP-2 and -9 and invasion activity were further determined via Western blot and gelatin zymography.

RESULTS

OSM-induced MMP-2 and -9 protein expression was significantly suppressed by STAT3 inhibition with stattic and STAT3 siRNA silencing, whereas the ERK1/2 inhibitor (U0126) and ERK silencing significantly suppressed OSM-induced MMP-2 protein expression. OSM-induced MMP-2 and MMP-9 enzymatic activities were significantly decreased by stattic pretreatment. The increased invasion activity induced by OSM was significantly suppressed by STAT3 and ERK1/2 inhibition, though to a greater extent by STAT3 inhibition.

CONCLUSION

Both STAT3 and ERK signaling pathways are involved in OSM-induced invasion activity of HTR8/SVneo cells. Activation of STAT3 appears to be critical for the OSM-mediated increase in invasiveness of HTR8/SVneo cells.

Molecular Cross-Talk at the Feto-Maternal Interface

Molecular cross-talk at the feto-maternal interface occurs between many different cell types, including uterine leukocytes, extravillous trophoblast cells, and uterine spiral arteries, is essential for the establishment and maintenance of pregnancy. This review concentrates on human pregnancy and examines three main areas in which cross-talk occurs; immune tolerance, regulation of extravillous trophoblast invasion, and remodeling of the uterine spiral arteries.

Triiodothyronine regulates angiogenic growth factor and cytokine secretion by isolated human decidual cells in a cell-type specific and gestational age-dependent manner

STUDY QUESTION

Does triiodothyronine (T3) regulate the secretion of angiogenic growth factors and cytokines by human decidual cells isolated from early pregnancy?

SUMMARY ANSWER

T3 modulates the secretion of specific angiogenic growth factors and cytokines, with different regulatory patterns observed amongst various isolated subpopulations of human decidual cells and with a distinct change between the first and second trimesters of pregnancy.

WHAT IS KNOWN ALREADY

Maternal thyroid dysfunction during early pregnancy is associated with complications of malplacentation including miscarriage and pre-eclampsia. T3 regulates the proliferation and apoptosis of fetal-derived trophoblasts, as well as promotes the invasive capability of extravillous trophoblasts (EVT). We hypothesize that T3 may also have a direct impact on human maternal-derived decidual cells, which are known to exert paracrine regulation upon trophoblast behaviour and vascular development at the uteroplacental interface.

STUDY DESIGN, SIZE, DURATION

This laboratory-based study used human decidua from first (8–11 weeks; n = 18) and second (12–16 weeks; n = 12) trimester surgical terminations of apparently uncomplicated pregnancies.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Primary cultures of total decidual cells, and immunomagnetic bead-isolated populations of stromal-enriched (CD10+) and stromal-depleted (CD10−) cells, uterine natural killer cells (uNK cells; CD56+) and macrophages (CD14+) were assessed for thyroid hormone receptors and transporters by immunocytochemistry. Each cell population was treated with T3 (0, 1, 10, 100 nM) and assessments were made of cell viability (MTT assay) and angiogenic growth factor and cytokine secretion (immunomediated assay). The effect of decidual cell-conditioned media on EVT invasion through Matrigel^® was evaluated.

MAIN RESULTS AND THE ROLE OF CHANCE

Immunocytochemistry showed the expression of thyroid hormone transporters (MCT8, MCT10) and receptors (TRα1, TRβ1) required for thyroid hormone-responsiveness in uNK cells and macrophages from the first trimester. The viability of total decidual cells and the different cell isolates were unaffected by T3 so changes in cell numbers could not account for any observed effects. In the first trimester, T3 decreased VEGF-A secretion by total decidual cells (P < 0.05) and increased angiopoietin-2 secretion by stromal-depleted cells (P < 0.05) but in the second trimester total decidual cells showed only increased angiogenin secretion (P < 0.05). In the first trimester, T3 reduced IL-10 secretion by total decidual cells (P < 0.05), and reduced granulocyte macrophage colony stimulating factor (P < 0.01), IL-8 (P < 0.05), IL-10 (P < 0.01), IL-1β (P < 0.05) and monocyte chemotactic protein -1 (P < 0.001) secretion by macrophages, but increased tumour necrosis factor-α secretion by stromal-depleted cells (P < 0.05) and increased IL-6 by uNK cells (P < 0.05). In contrast, in the second trimester T3 increased IL-10 secretion by total decidual cells (P < 0.01) but did not affect cytokine secretion by uNK cells and macrophages. Conditioned media from first trimester T3-treated total decidual cells and macrophages did not alter EVT invasion compared with untreated controls. Thus, treatment of decidual cells with T3 resulted in changes in both angiogenic growth factor and cytokine secretion in a cell type-specific and gestational age-dependent manner, with first trimester decidual macrophages being the most responsive to T3 treatment, but these changes in decidual cell secretome did not affect EVT invasion in vitro.

LIMITATIONS, REASONS FOR CAUTION

Our results are based on in vitro findings and we cannot be certain if a similar response occurs in human pregnancy in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

Optimal maternal thyroid hormone concentrations could play a critical role in maintaining a balanced inflammatory response in early pregnancy to prevent fetal immune rejection and promote normal placental development through the regulation of the secretion of critical cytokines and angiogenic growth factors by human decidual cells. Our data suggest that there is an ontogenically determined regulatory ‘switch’ in T3 responsiveness between the first and second trimesters, and support the notion that the timely and early correction of maternal thyroid dysfunction is critical in influencing pregnancy outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

This study is funded by Wellbeing of Women (RG/1082/09 to S.Y.C., M.D.K., J.A.F., L.S.L., G.E.L.) and Action Medical Research – Henry Smith Charity (SP4335 to M.D.K., S.Y.C., L.S.L., J.A.F.). The authors have no conflicts of interest to disclose.

Stimulatory Effect of Vascular Endothelial Growth Factor on Proliferation and Migration of Porcine Trophectoderm Cells and Their Regulation by the Phosphatidylinositol-3-Kinase-AKT and Mitogen-Activated Protein Kinase Cell Signaling Pathways

Vascular endothelial growth factor (VEGF), a potent stimulator for angiogenesis, is likely to regulate implantation by stimulating endometrial angiogenesis and vascular permeability. In addition to known angiogenetic effects, VEGF has been suggested to participate in development of the early embryo as a mediator of fetal-maternal dialogue. Current studies have determined VEGF in terms of its role in endometrial vascular events, but VEGF-induced effects on the peri-implantation conceptus (embryo and extraembryonic membranes) remains unknown. In the present study, endometrial VEGF, VEGF receptor-1 (VEGFR-1), and VEGF receptor-2 (VEGFR-2) mRNAs increased significantly during the peri-implantation period of pregnancy as compared to the estrous cycle. Expression of VEGF, VEGFR-1, and VEGFR-2 mRNAs was abundant in endometrial luminal and glandular epithelia, endothelial blood vessels, and scattered cells in the stroma and conceptus trophectoderm. In addition, porcine trophectoderm (pTr) cells treated with VEGF exhibited increased abundance of phosphorylated (p)-AKT1, p-ERK1/2, p-p70RSK, p-RPS6, and p-4EBP1 in a time-dependent manner. The addition of U0126, an inhibitor of ERK1/2, inhibited VEGF-induced ERK1/2 phosphorylation, but AKT1 phosphorylation was not affected. The addition of LY294002, a PI3K inhibitor, decreased VEGF-induced phosphorylation of ERK1/2 and AKT1. Furthermore, VEGF significantly stimulated proliferation and migration of pTr cells, but these effects were blocked by SB203580, U0126, rapamycin, and LY294002, which inhibit p38 MAPK, ERK1/2, mTOR, and PI3K, respectively. These results suggest that VEGF is critical to successful growth and development of pTr during early pregnancy and that VEGF-induced stimulatory effect is coordinately regulated by multiple cell signaling pathways, including PI3K-AKT1 and MAPK signaling pathways.

Trophoblast invasion and blood vessel remodeling are altered in a rat model of lifelong maternal obesity

Maternal obesity is associated with an increased risk of a number of pregnancy complications, including fetal demise, which may be linked to impaired placental development as a result of altered trophoblast invasion and vessel remodeling. Therefore, we examined these parameters in pregnant rats fed a control (normal weight) or high fat (HF) diet (obese) at 2 critical times of rat placental development. Early trophoblast invasion was increased by approximately 2-fold in HF-fed dams with a concomitant increase in the expression of matrix metalloproteinase 9 protein, a mediator of tissue remodeling and invasion. Furthermore, we observed significantly higher levels of smooth muscle actin surrounding the placental spiral arteries of HF-fed dams, suggesting impaired spiral artery remodeling. Taken together, the results of this study suggest that altered placental development is an important contributor to the poor pregnancy outcomes and increased fetal demise in our model of lifelong maternal obesity.

Gene expression in pre-term, pre-labour and parturient canine placenta

Matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), vascular endothelial growth factor (VEGF)-A, VEGF-A receptor (Flt-1) and KiSS-1 receptor (KiSS-1R) all play a role in trophoblast invasion in a number of mammalian species. However, mRNA expression of factors regulating trophoblast invasion has not been studied in dogs. Abnormal expression of these factors at the end of canine gestation may contribute to placental retention and/or subinvolution of placental sites. Therefore, we sought to determine the relative mRNA expression of these factors in canine chorioallantois tissue at 61 ± 1 day past the LH surge (pre-term; n = 4), following elective c-section at 64 ± 1 day past the LH surge prior to first-stage labour (pre-labour; n = 4) and following natural delivery (parturient; n = 3). Total RNA was isolated, real-time RT-PCR was performed, and relative expression was calculated using the relative quantitation (2-ΔΔCT) method. MMP-9 mRNA expression was significantly higher in pre-term samples compared to pre-labour and parturient samples. The results showed no significant difference between MMP-2, TIMP-2, VEGF-A and Flt-1 mRNA expression among the three groups. KiSS-1R mRNA was not expressed in any tissues studied. Gene expression of MMP-9 may be related to the onset of labour, whereas MMP-2, VEGF-A, Flt-1, TIMP-2 and KiSS-1R mRNA do not appear to play a role at the end of gestation in the dog.

Extravillous trophoblast and decidual natural killer cells: a remodelling partnership

BACKGROUND

During pregnancy, maternal uterine spiral arteries (SAs) are remodelled from minimal-flow, high-resistance vessels into larger diameter vessels with low resistance and high flow. Fetal extravillous trophoblasts (EVT) have important roles in this process. Decidual natural killer cells (dNK cells) are the major maternal immune component of the decidua and accumulate around SAs before trophoblast invasion. A role for dNK cells in vessel remodelling is beginning to be elucidated. This review examines the overlapping and dissimilar mechanisms used by EVT and dNK cells in this process and how this may mirror another example of tissue remodelling, namely cancer development.

METHODS

The published literature was searched using Pubmed focusing on EVT, dNK cells and SA remodelling. Additional papers discussing cancer development are also included.

RESULTS

Similarities exist between actions carried out by dNK cells and EVT. Both interact with vascular cells lining the SA, as well as with each other, to promote transformation of the SA. EVT differentiation has previously been likened to the epithelial-mesenchymal transition in cancer cells, and we discuss how dNK-EVT interactions at the maternal-fetal interface can also be compared with the roles of immune cells in cancer.

CONCLUSIONS

The combined role that dNK cells and EVT play in SA remodelling suggests that these interactions could be described as a partnership. The investigation of pregnancy as a multicellular system involving both fetal and maternal components, as well as comparisons to similar examples of tissue remodelling, will further identify the key mechanisms in SA remodelling that are required for a successful pregnancy.

Decreased expressions of vascular endothelial growth factor and visfatin in the placental bed of pregnancies complicated by preeclampsia

AIM

The aim of the present study was to examine the expression of vascular endothelial growth factor (VEGF) and visfatin in the third trimester placental bed of pregnancies with and without preeclampsia (PE).

MATERIAL AND METHODS

The study group consisted of placental bed biopsy tissues obtained from pregnancies with (n = 20) and without (n = 20) PE. The normotensive controls without PE were matched for gestational age at delivery with patients with PE. The expression of VEGF and visfatin in the placental bed tissues were evaluated using reverse transcriptase-polymerase chain reaction (RT-PCR), real-time polymerase chain reaction (PCR), immunohistochemistry and Western blot.

RESULTS

There was no statistical difference between the PE group and the normotensive control group in age and body mass index (BMI). The expression of VEGF and visfatin was significantly decreased in the PE group compared with the normotensive control group (P < 0.05).

CONCLUSION

This study showed decreased expressions of VEGF and visfatin in the third trimester placental bed of pregnancies with PE compared with the normotensive controls. This result suggests that decreased expression of these angiogenic factors in placental bed may be associated with the pathogenesis of PE.

Angiogenic growth factors in the diagnosis and prediction of pre-eclampsia

The pathogenesis of pre-eclampsia is still not completely known; however, in the recent decade, there have been tremendous research efforts leading to impressive results highlighting the role of a disturbed angiogenic balance as one of the key features of the disease. Numerous studies have shown the key role of the placenta in the pathogenesis of pre-eclampsia. A shift in the sFlt-1 (soluble Fms-like tyrosine kinase-1)/PlGF (placental growth factor) ratio is associated with the disease. Although pre-eclampsia seems to be a clearly defined disease, clinical presentation, and particularly the dynamics of the clinical course, can vary enormously. The only available tools to diagnose pre-eclampsia are blood pressure measurement and urine protein sampling. However, these tools have a low sensitivity and specificity regarding the prediction of the course of the disease or maternal and perinatal outcomes. The only cure for the disease is delivery, although a timely diagnosis helps in decreasing maternal and fetal morbidity and mortality. The sFlt1/PlGF ratio is able to give additional valuable information on the status and progression of the disease and is apt to be implemented in the diagnostic algorithm of pre-eclampsia. In the present review, we aim to provide an overview of the vast literature on angiogenesis and anti-angiogenesis factors in pre-eclampsia that have been published over the last decade. We introduce work from basic research groups who have focused on the pathophysiological basis of the disease. Furthermore, we review studies with a clinical focus in which the sFlt-1/PlGF ratio has been analysed along with other candidates for routine clinical assessment of pre-eclampsia.

Accreta complicating complete placenta previa is characterized by reduced systemic levels of vascular endothelial growth factor and by epithelial-to-mesenchymal transition of the invasive trophoblast

OBJECTIVE

We sought to characterize serum angiogenic factor profile of women with complete placenta previa and determine if invasive trophoblast differentiation characteristic of accreta, increta, or percreta shares features of epithelial-to-mesenchymal transition.

STUDY DESIGN

We analyzed gestational age-matched serum samples from 90 pregnant women with either complete placenta previa (n = 45) or uncomplicated pregnancies (n = 45). Vascular endothelial growth factor (VEGF), placental growth factor, and soluble form of fms-like-tyrosine-kinase-1 were immunoassayed. VEGF and phosphotyrosine immunoreactivity was surveyed in histological specimens relative to expression of vimentin and cytokeratin-7.

RESULTS

Women with previa and invasive placentation (accreta, n = 5; increta, n = 6; percreta, n = 2) had lower systemic VEGF (invasive previa: median 0.8 [0.02-3.4] vs control 6.5 [2.7-10.5] pg/mL, P = .02). VEGF and phosphotyrosine immunostaining predominated in the invasive extravillous trophoblasts that coexpressed vimentin and cytokeratin-7, an epithelial-to-mesenchymal transition feature and tumorlike cell phenotype.

CONCLUSION

Lower systemic free VEGF and a switch of the interstitial extravillous trophoblasts to a metastable cell phenotype characterize placenta previa with excessive myometrial invasion.

Plasma soluble vascular endothelial growth factor receptor-1 concentration is elevated prior to the clinical diagnosis of pre-eclampsia

OBJECTIVE

Accumulating evidence suggests that the balance between vascular endothelial growth factor (VEGF), placental growth factor (PIGF), and their receptors is important for effective vasculogenesis, angiogenesis, and placental development. Recently, the soluble form of VEGFR-1 (sVEGFR-1), an antagonist to VEGF and PIGF, has been implicated in the pathophysiology of pre-eclampsia. Plasma sVEGFR-1 concentration is elevated in pre-eclampsia at the time of clinical diagnosis and correlates with the severity of the disease. The purpose of this study was to determine whether the concentrations of sVEGFR-1 in plasma of pre-eclamptic patients change prior to the clinical manifestations of the disease.

METHODS

A longitudinal case-control study was conducted in normal pregnant women (n = 44) and patients with pre-eclampsia (n = 44). Blood sampling was performed at six intervals: (1) 7-16 weeks; (2) 16-24 weeks; (3) 24-28 weeks; (4)28-32 weeks; (5) 32-36 weeks; and (6) more than 37 weeks of gestation. To examine the relationship between plasmasVEGFR-1 concentration and interval to clinical diagnosis of pre-eclampsia, plasma samples of pre-eclamptic patients at different gestational ages were stratified according to the interval from blood sampling to clinical development of the disease into five groups: (1) at clinical manifestation; (2) 2-5 weeks; (3) 6-10 weeks; (4) 11-16 weeks; and (5) 17-25 weeks before clinical manifestations. Plasma concentrations of sVEGFR-1 were determined by enzyme-linked immunoassay. Parametric statistics and repeated measure procedures were used for the analysis.

RESULTS

The mean plasma sVEGFR-1 concentration in pre-eclamptic patients before the clinical manifestation of the disease was significantly higher than in normal pregnant women at 24-28, 28-32, and 32-37 weeks of gestation (p = 0.02,p < 0.001, and p < 0.001, respectively). In contrast, no significant differences in the mean plasma sVEGFR-1 concentration between patients with pre-eclampsia and normal pregnant women were observed both at 7-16 weeks and 16-24 weeks of gestation (p= 0.1 and p= 0.9). Similarly, the mean plasma sVEGFR-1 concentration was significantly higher in pre-eclamptic patients than in normal pregnant women at clinical manifestation, at 2-5 weeks (mean 3.8 weeks), and at 6-10 weeks (mean 8.2 weeks) prior to the development of clinical pre-eclampsia (p < 0.001, p < 0.001, and p = 0.002,respectively). Among patients with early-onset pre-eclampsia (defined as gestational age of 34 weeks or less), the mean plasma sVEGFR-1 concentration was significantly higher in pre-eclampsia (before clinical diagnosis) than in normal pregnant women at 24-28 (mean 26.4) weeks of gestation (p = 0.008). In contrast, among patients with the late-onset disease(defined as gestational age of more than 34 weeks), plasma sVEGFR-1 concentration in pre-clinical pre-eclampsia was significantly higher than in normal pregnant women at 28-32 (mean 30.2) weeks of gestation (p < 0.001).

CONCLUSIONS

Plasma sVEGFR-1 concentration is elevated in pre-eclampsia prior to the clinical diagnosis of the disease. This elevation began 6-10 weeks prior to the clinical manifestations, and the increase was more pronounced at 2-5 weeks before the diagnosis, as well as at clinical presentation. Furthermore, in early-onset pre-eclampsia, plasma concentration ofsVEGFR-1 is elevated earlier than the late-onset disease.

Trophoblast invasion

Trophoblast invasion can be seen as a tightly regulated battle between the competing interests of the survival of the fetus and those of the mother. Successful pregnancy is dependent on the trophoblast invading the mother, attaching the pregnancy to the uterus and securing an adequate supply of oxygen and nutrient to the fetus. For successful invasion to occur, extravillous trophoblast has to perform a range of functions; transformation of the maternal spiral arteries, tolerate hypoxia, proliferate and die by apoptosis (programmed cell death), differentiate, adhere to and digest the extracellular matrix, move and interact with the maternal immune system. Each of these functions has multiple overlapping control systems so that trophoblast invasion is a finely controlled balance of competing mechanisms.

Effect of impaired glucose tolerance during pregnancy on the expression of VEGF receptors in human placenta

The aim of the present study was to determine the expression of vascular endothelial growth factor (VEGF) receptors VEGFR-1, VEGFR-2 and VEGFR-3 in placentas from pregnancies complicated by altered glycaemia. Placentas from women with physiological pregnancies (Group 1), pregnancies complicated by minor degree of glucose intolerance (MDGI, Group 2) and by gestational diabetes mellitus (GDM) treated with insulin (Group 3) were collected. Immunohistochemistry, RT-PCR and western blot were employed to evaluate receptor expression. In the three study groups, VEGFR-1 immunoreactivity was detected in all the placental components. VEGFR-2 immunoreactivity was observed in the vessels of all the placentas from Groups 1 and 2, but only in some placentas of Group 3. VEGFR-3 reactivity was observed in all the components of Group 1; in Groups 2 and 3 reactivity was observed in some portions of the trophoblast or the whole trophoblast, and in the stroma. VEGFR-1 and VEGFR-2 mRNA levels in Groups 2 and 3 were significantly higher compared with Group 1, whereas those of VEGFR-3 were significantly lower. Receptor protein levels were significantly lower in Groups 2 and 3 compared with Group 1. These findings demonstrated dysregulation of expression of the three placental receptors, both in GDM and in MDGI.

Localization of angiogenic growth factors and their receptors in the human placental bed throughout normal human pregnancy

During early human pregnancy invasion of uterine spiral arteries by extravillous trophoblast cells contributes to their remodelling characterised by loss of musculo-elastic media and replacement by fibrinoid containing trophoblast. Despite its importance for successful pregnancy, the mechanisms underlying 'transformation' of spiral arteries are not well understood. The aim of this study was to localize expression of members of the angiopoietin (Ang) family (Ang-1, Ang-2 and their receptor Tie-2) and the vascular endothelial growth factor (VEGF) family (VEGF-A, VEGF-C, VEGF-D and their receptors VEGF-R1, VEGF-R2 and VEGF-R3) in the placental bed throughout normal human pregnancy. Placental bed biopsies were obtained from women undergoing elective termination of pregnancy at 8-10, 12-14 and 16-20 weeks' gestation and elective caesarean section at term (n=6 each group). Paraffin-embedded sections were immunostained for Ang-1, Ang-2, Tie-2, VEGF-A, VEGF-C, VEGF-D, VEGF-R1, VEGF-R2 and VEGF-R3 using an avidin biotin peroxidase technique. Reactivity of endovascular, interstitial, intramural and multinucleate extravillous trophoblast populations in the placental bed was analysed semi-quantitatively. There was an increase in the level of immunostaining of intramural EVT for Tie-2 and VEGF-C with increasing gestational age. In addition, there was a reduction in Ang-1 and Ang-2 expression by multinucleate interstitial EVT and of VEGF-R1 and VEGF-R2 by endovascular EVT with increasing gestational age. At the earlier gestational ages studied, immunostaining for Ang-1, Ang-2, Tie-2, VEGF-C, VEGF-R1 and VEGF-R2 on intramural EVT was reduced compared to both mononuclear interstitial and endovascular EVT. These findings suggest that the Ang and VEGF families may play a role in the process of spiral artery remodelling in normal pregnancy.

CXCL10/IP-10: a missing link between inflammation and anti-angiogenesis in preeclampsia?

OBJECTIVE

Interferon (IFN)-gamma inducible protein, CXCL10/IP-10, is a member of the CXC chemokine family with pro-inflammatory and anti-angiogenic properties. This chemokine has been proposed to be a key link between inflammation and angiogenesis. The aim of this study was to determine whether preeclampsia and delivery of a small for gestational age (SGA) neonate are associated with changes in maternal serum concentration of CXCL10/IP-10.

STUDY DESIGN

This cross-sectional study included patients in the following groups: (1) non-pregnant women (N = 49); (2) women with normal pregnancies (N = 89); (3) patients with preeclampsia (N = 100); and (4) patients who delivered an SGA neonate (N = 78). SGA was defined as birth weight below the 10th percentile. Maternal serum concentrations of CXCL10/IP-10 were measured by sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) Patients with normal pregnancies had a significantly higher median serum concentration of CXCL10/IP-10 than non-pregnant women (median 116.1 pg/mL, range 40.7-1314.3 vs. median 90.3 pg/mL, range 49.2-214.7, respectively; p = 0.002); (2) no significant correlation was found between maternal serum concentration of CXCL10/IP-10 and gestational age (between 19 and 38 weeks); (3) there were no differences in median serum CXCL10/IP-10 concentrations between patients who delivered an SGA neonate and those with normal pregnancies (median 122.4 pg/mL, range 37.3-693.5 vs. median 116.1 pg/mL, range 40.7-1314.3, respectively; p > 0.05); (4) patients with preeclampsia had a higher median serum concentration of CXCL10/IP-10 than normal pregnant women (median 156.4 pg/mL, range 47.4-645.9 vs. median 116.1 pg/mL, range 40.7-1314.3, respectively; p < 0.05); (5) patients with preeclampsia had a higher median concentration of CXCL10/IP-10 than those who delivered an SGA neonate (median 156.4 pg/mL, range 47.4-645.9 vs. median 122.4 pg/mL, range 37.3-693.5, respectively; p < 0.05).

CONCLUSIONS

Patients with preeclampsia have significantly higher serum concentrations of CXCL10/IP-10 than both normal pregnant women and mothers who have SGA neonates. These results are likely to reflect an anti-angiogenic state as well as an enhanced systemic inflammatory response in patients with preeclampsia. Alternatively, since preeclampsia and SGA share several mechanisms of disease, it is possible that a higher concentration of this chemokine may contribute to the clinical presentation of preeclampsia in patients with a similar intrauterine insult.

The immunohistochemical evaluation of VEGF in placenta biopsies of pregnancies complicated by preeclampsia

OBJECTIVE

The study was designed to determine the protein levels of vascular endothelial growth factor (VEGF) in the placenta biopsies of patients with preeclampsia and compare with normal controls.

DESIGN

Prospective cohort study.

METHODS

The placental biopsies were obtained from ten patients with preeclampsia and ten patients of control group at the time of delivery. Avidin-biotin-peroxidase immunohistochemistry was then performed to identify levels of VEGF protein within the tissue and a semi-quantitative method was devised to score the amount of staining present in the sample. Two histopathologists who were blinded to the groups were asked to score each sample for the intensity of staining and the number of cells stained in a randomly selected per high-power fields of each sample. The resulting "H-score" was computed as a product of intensity and percent of cells stained.

RESULTS

The VEGF expression was significantly higher in placenta biopsies of preeclamptic patients compared to that of controls (271.2 +/- 22.65 vs. 201.9 +/- 12.33, P = 0.000).

CONCLUSION

Immunostaining of VEGF is significantly higher in placenta biopsies of patients with preeclampsia.

Homeobox gene HLX1 is a regulator of colony stimulating factor-1 dependent trophoblast cell proliferation

The cytokine colony stimulating factor-1 (CSF-1) is a key regulator of the proliferation, differentiation and activation of mononuclear phagocytes. CSF-1 also plays an important role in reproduction. CSF-1 is produced in the placenta and activates signal transduction pathways that significantly increase the proliferation of placental trophoblast cells in culture. The target genes activated by CSF-1 mediated signal transduction in the nucleus are not well understood. Here, we use placental trophoblast cells to investigate potential downstream effector genes of CSF-1. HLX1 is a homeobox gene that controls proliferation in embryonic cell types and haematopoietic cell lineages. We have shown HLX1 is expressed in placental trophoblast cells but its functional role in the placenta is unknown. Following CSF-1 stimulation, HLX1 mRNA expression was significantly increased in SGHPL-4 and HTR-8/SVNeo cultured trophoblast cells (p<0.001, n=3). siRNA-mediated reduction of HLX1 mRNA levels with four independent oligonucleotides (siRNAs) resulted in significantly decreased cell proliferation in both cell lines (p<0.001, n=4). When HLX1 mRNA levels were reduced in the presence of CSF-1 stimulation, proliferation remained significantly decreased (p<0.001, n=4) in both the cell lines. We have shown for the first time that a homeobox gene, HLX1, is a downstream effector gene of CSF-1, that HLX1 regulates placental cell proliferation and that CSF-1 acts, at least in part, through HLX1 to control cell proliferation.

Expression of vascular endothelial growth factor receptor types 1, 2 and 3 in placenta from pregnancies complicated by hypertensive disorders

The aim of the present study was to determine the expression of vascular endothelial growth factor (VEGF) family receptors (VEGFR) in placentas from pregnancies complicated by hypertensive disorders of different clinical severity. Placental tissue from women with gestational hypertension, pre-eclampsia, pre-eclampsia with haemolysis, elevated liver enzymes and low platelets (HELLP syndrome) and normotensive women, as a control group, was examined. Immunohistochemical techniques, reverse transcription–polymerase chain reaction and western blot were used to evaluate receptor expression. In cases with gestational hypertension, as well as in control cases, VEGFR-1 and VEGFR-3 immunoreactivity was detected in all placental components, whereas in placentas from the pre-eclampsia and pre-eclampsia with HELLP syndrome groups, VEGFR-1 and VEGFR-3 immunoreactivity was detected only in some portions of trophoblast and/or some vessels and/or clusters of stromal cells. In the control group, VEGFR-2 immunoreactivity was observed only in the vessels, whereas the hypertensive groups showed VEGF-2 immunoreactivity also in trophoblast and stromal cells. The mRNA levels of the three receptors in the group with gestational hypertension were higher with respect to those in the control group. Placentas from pregnancies with pre-eclampsia showed lowest mRNA expression levels, whereas placentas from women with pre-eclampsia plus HELLP syndrome showed higher mRNA expression levels with respect to the three other groups. Receptor protein levels were lower in pathological cases compared with levles in the control group. These findings demonstrate a dysregulation of placental expression of VEGF family receptors related to the degree of clinical severity of the hypertensive disorder.

Interferon-gamma inhibits extravillous trophoblast cell invasion by a mechanism that involves both changes in apoptosis and protease levels

BACKGROUND

Extravillous trophoblast cell (EVT) invasion of decidua and inner third of the myometrium is critical for a successful pregnancy. Many decidual factors are likely to play a role in regulating this process, including uterine natural killer (uNK) cell-derived cytokines.

HYPOTHESES

1) uNK cells are a major source of IFN gamma (IFN-gamma) and 2) IFN-gamma inhibits EVT invasion via an increase in EVT apoptosis and/or a decrease in active protease levels.

METHODS

Total decidual and uNK cells from 8-10 wk and 12-14 wk gestational age were cultured. IFN-gamma mRNA (real-time RT-polymerase chain reaction) and protein levels (FastQuant multicytokine analysis) were determined. EVT invasion in the presence of IFN-gamma or anti-IFN-gamma-neutralizing antibodies was assessed. Trophoblast apoptosis and proliferation was assessed in explants by immunohistochemistry for M30 and Ki67. Substrate zymography was performed to determine levels of secreted MMP2, MMP9, and uPA.

RESULTS

mRNA and protein for IFN-gamma was detected in both total decidual and uNK cell fractions. Trophoblast invasion was inhibited by IFN-gamma. The level of M30-positive EVT was increased in the presence of IFN-gamma whereas levels of secreted MMP2 were decreased.

CONCLUSIONS

uNK cells are a source of IFN-gamma within early human pregnancy decidua. Mechanisms of IFN-gamma inhibition of EVT invasion include both increased EVT apoptosis and reduced levels of active proteases.

Dimethylarginine dimethylaminohydrolase (DDAH) regulates trophoblast invasion and motility through effects on nitric oxide

BACKGROUND

Invasion of trophoblast into the uterine environment is crucial for establishing a successful pregnancy. Physiological production of nitric oxide (NO) by extravillous trophoblasts results in significant pro-invasive effects. NO synthesis is competitively inhibited by methylated arginine analogues such as asymmetric dimethylarginine (ADMA) but not the enantiomer symmetric dimethylarginine (SDMA). Within cells, the concentration of ADMA is regulated by the activity of the enzyme dimethylarginine dimethylaminohydrolase (DDAH). The aim of this study was to examine DDAH expression and function in trophoblasts.

METHODS AND RESULTS

DDAH-1 and DDAH-2 messenger RNA and protein were demonstrated in first trimester placental tissue, primary extravillous trophoblasts and extravillous trophoblast-derived cell lines. DDAH activity was demonstrated in both cells and tissue. Overexpression of DDAH-1 in trophoblasts led to a number of significant changes, including an 8-fold increase in enzymatic activity, a 59% decrease in production of ADMA (but not SDMA), a 1.9-fold increase in NO and a 1.6-fold increase in cyclic guanosine monophosphate (cGMP) production. Functional assays showed that increased DDAH activity led to significantly increased cell motility and invasion in response to hepatocyte growth factor (HGF).

CONCLUSIONS

DDAH may play an important role in the regulation of extravillous trophoblast function via its effects on ADMA and NO production.

Effect of low oxygen concentrations on trophoblast-like cell line invasion

The applicability of trophoblast-like cell lines to the study of trophoblast function has been widely debated. The present study investigated the effect of oxygen on the invasiveness, apoptosis, proliferation and secreted proteases of four different trophoblast cell lines; HTR-8/SVneo, SGHPL-4, JEG3 and JAR. All experiments were performed at 20% and 3% oxygen for 24, 48 and 72h. Immunostaining for integrins alpha1, alpha6 and beta3, cytokeratin 7 and HLA-G was used to determine the phenotype of the different cell lines. Invasion was assessed using the Matrigel invasion assay. Immunostaining for M30 and Ki67 determined levels of apoptosis and proliferation, respectively. Gelatin and casein/plasminogen zymography were performed on conditioned media to determine levels of secreted matrix metalloproteinase (MMP) 2 and MMP9 and urokinase plasminogen activator (uPA), respectively. None of the cell lines immunostained for all markers normally expressed by extravillous trophoblast cells. Invasiveness of HTR-8/SVneo and JEG3 cells cultured in 3% oxygen was increased after 24h but was inhibited by 72h in culture. Invasion of SGHPL-4 cells was inhibited after culture in 3% oxygen for 24h. Invasion by JAR cells was not affected by changes in oxygen concentration. The different cell lines also displayed different responses to culture period in 3% oxygen with respect to apoptosis, proliferation and secreted proteases. Care should be taken before results obtained using cell lines as a model for EVT are extrapolated to extravillous trophoblast cell behaviour in vivo.

Low Oxygen Concentrations Inhibit Trophoblast Cell Invasion from Early Gestation Placental Explants via Alterations in Levels of the Urokinase Plasminogen Activator System1

Extravillous trophoblast cell (EVT) invasion in early pregnancy occurs in a relatively low-oxygen environment. The role of oxygen in regulation of EVT invasion remains controversial. We hypothesized that 1) culture in 3% oxygen inhibits EVT invasion compared with culture at 8% or 20% oxygen and 2) inhibition of invasion is due to alterations in levels of components of the urokinase plasminogen activator (PLAU, uPA) system rather than through increased apoptosis and/or decreased proliferation. Placental samples (8-10, 12-14, and 16-20 wk gestation) were obtained from women undergoing elective surgical termination of pregnancy or after cesarean section delivery (term) at the Royal Victoria Infirmary, Newcastle upon Tyne, U.K. EVT invasion from placental explants cultured at 3%, 8%, or 20% oxygen was assessed using Matrigel invasion assays. Invasion was assessed on Day 6, explants were harvested for analysis of apoptosis and proliferation, and medium was stored for analysis of PLAU system components by ELISA and casein zymography. Culture at 3% oxygen inhibited EVT invasion. PLAU receptor and plasminogen activator inhibitor-2 protein levels were increased and PLAU activity decreased in these cultures. There was no difference in the proliferation in explants cultured at the three different oxygen concentrations. Apoptosis, assessed by M30 immunostaining, was increased in EVT at both 3% and 8% oxygen. The reduction in the invasive capacity of EVT cultured at 3% oxygen appears to be mediated both by a general inhibition of the PLAU system and a decrease in the number of cells available to invade.

Evidence supporting that the excess of the sVEGFR-1 concentration in maternal plasma in preeclampsia has a uterine origin

BACKGROUND

Preeclampsia has been considered an anti-angiogenic state. Two factors have been implicated in the genesis of this state: soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) and placental growth factor (PlGF). Indeed, the concentrations of PlGF, an angiogenic factor, are lower in preeclampsia than in normal pregnancy, while the opposite is the case for the anti-angiogenic factor, sVEGFR-1. The source of the excess sVEGFR-1 has not yet been determined. Since the placenta could be a source of sVEGFR-1, we conducted a study to determine whether there is a gradient in the plasma concentration of sVEGFR-1 and PlGF between the uterine vein and the antecubital vein in both patients with preeclampsia and normal pregnant women.

METHODS

A cross-sectional study was performed to determine the plasma concentrations of sVEGFR-1 and PlGF in the uterine and antecubital vein of patients with preeclampsia (n = 9) and normal pregnant women at term (n = 9). Plasma samples were collected from antecubital and uterine veins at the time of cesarean section. The concentrations of sVEGFR-1 and PlGF were determined using specific enzyme-linked immunoassays. The differences of plasma concentrations of sVEGFR-1 and PlGF between uterine and antecubital veins in both groups were compared by paired t-tests.

RESULTS

Patients with preeclampsia had a significantly higher mean plasma concentration of sVEGFR-1 in the uterine vein than in the antecubital vein (uterine vein: mean 13,675 +/- 5,684 pg/ml vs. antecubital vein: mean 10,234 +/- 4,700 pg/ml; paired t-tests, p = 0.04). In contrast, among normal pregnant women at term, there was no significant difference in plasma concentrations of sVEGFR-1 between the uterine and antecubital veins (uterine vein: mean 1,918 +/- 665 pg/ml vs. antecubital vein: mean 1,750 +/- 475 pg/ml; paired t-tests, p = 0.1). The mean plasma concentration of sVEGFR-1, either in the antecubital or uterine vein, was significantly higher in preeclampsia than in normal pregnancy (unpaired t-tests; both p < 0.001). There was no significant difference in the mean plasma concentration of PlGF between the uterine and the antecubital veins in both the preeclamptic (uterine vein, mean +/- SD: 129 +/- 106 pg/ml vs. antecubital vein, mean +/- SD: 82 +/- 43 pg/ml; paired t-tests, p = 0.2) and normal pregnancy groups (uterine vein, mean +/- SD: 331 +/- 254 pg/ml vs. antecubital vein, mean +/- SD: 319 +/- 259 pg/ml; paired t-tests, p = 0.4). The mean plasma concentration of PlGF, either in the uterine or antecubital vein, was lower in preeclampsia than in normal pregnancy (unpaired t-tests; p = 0.008 and 0.02 respectively).

CONCLUSIONS

Plasma concentration of sVEGFR-1 was higher in the uterine vein than in the antecubital vein in women with preeclampsia. This provides evidence supporting the concept that the uterus is a potential source of the excess circulating sVEGFR-1 concentration in preeclamptic women.

VEGF, bFGF and their receptors at the fetal-maternal interface of the rhesus monkey

Placental development involves trophoblast outgrowth and a coordinated angiogenesis in the implantation site. In this study, expression of angiogenic factors, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), VEGF receptors, kinase insert domain-containing region (KDR), and bFGF receptor Flg was characterized at the maternal-embryonic boundary of the rhesus monkey on Day 17, 19, 28 and 34 of pregnancy. Immunohistochemistry and in situ hybridization showed that VEGF mRNA and protein were both strongly expressed in the cytotrophoblast, the blood vessels and certain immunocytes. These sites were also immunopositive for KDR. In addition to the vascular endothelial cells and the vascular smooth muscle cells, the protein and mRNA for bFGF were also detected in cyto/syncytiotrophoblast bilayer, whereas the staining for Flg protein was mainly localized in the cytotrophoblast cells. The staining degree of VEGF and bFGF in the villi gradually decreased with the development of placenta. Strong expression of bFGF, Flg and KDR was also detected in the decidual cells. These data suggest that VEGF and bFGF may be involved in angiogenesis, cytotrophoblast proliferation and migration during early stage of placentation in the rhesus monkey.

Effects of Low-Molecular-Weight and Unfractionated Heparin on Trophoblast Function

OBJECTIVE

Unfractionated and low-molecular-weight heparin and low-dose aspirin are used for the prevention of pregnancy loss in pregnant women with thrombophilia. We investigated the effect of these drugs on in vitro models of human extravillous trophoblast motility and differentiation.

METHODS

Chorion from term placentas was digested and extravillous trophoblast isolated. Extravillous trophoblast formed giant multinuclear cells that were counted after 24, 36, and 48 hours of culture. This model was then used to investigate the effect of unfractionated, low-molecular-weight heparin and aspirin on in vitro extravillous trophoblast differentiation at both therapeutic and supratherapeutic doses. In addition, the effect of unfractionated and low-molecular-weight heparin on hepatocyte growth factor-stimulated SGHPL-4 cell (extravillous trophoblast cell line) motility was determined by time-lapse microscopy.

RESULTS

At therapeutic doses unfractionated heparin promoted extravillous trophoblast differentiation. However, low-molecular-weight heparin inhibited giant multinuclear cells formation. At supratherapeutic doses, both low-molecular-weight and unfractionated heparin promoted extravillous trophoblast differentiation. Low-dose aspirin had minimal effects on the extravillous trophoblast differentiation. Both unfractionated and low-molecular-weight heparin inhibited hepatocyte growth factor-stimulated extravillous trophoblast motility at supratherapeutic doses. At a therapeutic dose of 0.25 IU/mL, only unfractionated heparin inhibited hepatocyte growth factor-stimulated motility, whereas low-molecular-weight heparin had no effect.

CONCLUSION

Our data suggest that unfractionated and low-molecular-weight heparin have differing effects on trophoblast differentiation and motility at therapeutic doses. This finding may be one of many factors that contribute to the clinical scenario.

VEGF expression in the placenta from pregnancies complicated by hypertensive disorders

OBJECTIVE

To determine the expression of VEGF in the placental tissue from pregnancies complicated by hypertension disorders of different clinical severity.

DESIGN

Prospective cohort study.

SETTING

Polyclinic of Careggi, University of Florence, Italy.

SAMPLE

Placentas from women with gestational hypertension (n= 20), pre-eclampsia (n= 20) and pre-eclampsia with HELLP syndrome (n= 20) and from normotensive women (n= 20), as control group (gestational age comprised between 35 and 38 weeks).

METHODS

An immunohistochemical technique and a quantitative analysis to measure mRNA levels (RT-PCR) were employed.

MAIN OUTCOME MEASURES

Intensity of immunoreactivity and mRNA levels in the placental components. Differences between the data.

RESULTS

VEGF immunoreactivity was observable in all the placental components in the gestational hypertension cases as in the control ones. In the cases with pre-eclampsia and pre-eclampsia with HELLP syndrome, some placental components were not immunoreactive. However, the VEGF positive components of all the pathological groups showed a higher intensity of reactivity with respect to that of the control group. The levels of VEGF mRNA were higher in the gestational hypertension cases and lower in the cases of pre-eclampsia with HELLP syndrome with respect to the control ones; in the cases of pre-eclampsia, the levels were the same as the control ones.

CONCLUSION

The different expression of VEGF in the placenta of the pathological cases is probably related to haemodynamic changes that take place in these disorders, in order to attempt restoration of a normal uteroplacental flow.

Interaction of cocultured decidual endothelial cells and cytotrophoblasts in preeclampsia

Disturbed cell-cell communication between trophoblasts and the maternal endothelium may be responsible for the deficient endovascular invasion seen in preeclampsia. In vitro studies have been hampered by lack of suitable models to directly examine interactions between these cell types. Using a bilayer coculture model, we examined the effect of decidual endothelial cells on matrix metalloproteinase secretion and the migration of cytotrophoblasts from preeclamptic pregnancies. Cells were incubated on semipermeable membranes in 20% or 2% O(2) with or without the tumor promoter phorbol 12-myristate 13-acetate, which activates matrix metalloproteinase-2 and -9 in endothelial cells. Cytotrophoblasts from preeclamptic pregnancies secreted significantly less matrix metalloproteinase-2 and -9 than their normal counterparts. Although decidual endothelial cells downregulated cytotrophoblast migration in normal pregnancy, this was not observed in cocultures with cytotrophoblasts from preeclamptic pregnancies. In addition, cytotrophoblasts from preeclamptic pregnancies altered phorbol myristate acetate-induced activation of endothelial matrix metalloproteinases. Hypoxia increased cytotrophoblast migration when cells were incubated alone but not in coculture with decidual endothelial cells due to increased adhesion between the two cell types. These results suggest dysfunctional interactive regulation of migration and matrix metalloproteinase secretion in preeclampsia that could result in abnormal endovascular trophoblast invasion of the maternal vasculature.