Endovascular Trophoblast Invasion Research Articles

Three-Dimensional Histological Characterization of the Placental Vasculature Using Light Sheet Microscopy

The placenta is the first embryonic organ, representing the connection between the embryo and the mother, and is therefore necessary for the embryo’s growth and survival. To meet the ever-growing need for nutrient and gas exchange, the maternal spiral arteries undergo extensive remodeling, thus increasing the uteroplacental blood flow by 16-fold. However, the insufficient remodeling of the spiral arteries can lead to severe pregnancy-associated disorders, including but not limited to pre-eclampsia. Insufficient endovascular trophoblast invasion plays a key role in the manifestation of pre-eclampsia; however, the underlying processes are complex and still unknown. Classical histopathology is based on two-dimensional section microscopy, which lacks a volumetric representation of the vascular remodeling process. To further characterize the uteroplacental vascularization, a detailed, non-destructive, and subcellular visualization is beneficial. In this study, we use light sheet microscopy for optical sectioning, thus establishing a method to obtain a three-dimensional visualization of the vascular system in the placenta. By introducing a volumetric visualization method of the placenta, we could establish a powerful tool to deeply investigate the heterogeneity of the spiral arteries during the remodeling process, evaluate the state-of-the-art treatment options, effects on vascularization, and, ultimately, reveal new insights into the underlying pathology of pre-eclampsia.

Macrophage migration inhibitory factor modulates cytokine expression in the trophoblast cell line HTR-8/SVneo.

Extravillous trophoblasts are specific placental cells that invade the uterine stroma and spiral arteries modifying and adjusting them to pregnancy. Many pregnancy pathologies are associated with impairment of this process, including preeclampsia and intrauterine growth restriction, among others. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that is abundant at the fetomaternal interface. Previous results from our group showed that MIF participates in trophoblast invasion and modulates the expression of molecules known to mediate stromal and endovascular trophoblast invasion. In this study we investigated the possibility that MIF could act as a regulator of cytokines known to modulate trophoblast invasion using the normal extravillous trophoblast-derived cell line HTR-8/SVneo. Expression of trophoblast MIF was attenuated by MIF mRNA-specific small interfering RNAs. Cytokine expression was assessed at the mRNA and protein levels using real-time quantitative polymerase chain reaction and flow cytometry respectively. Knockdown of MIF led to a significant decrease in mRNA for IL-1β (IL1B) and IL-8 (CXCL8) and interleukin (IL)-8 protein. The addition of recombinant human MIF to cell culture medium increased IL-6 after 24h treatment and IL-6 and IL-8 after 72h treatment. Cell viability was not affected by MIF silencing or rhMIF treatment. The results of this study imply that at least some of the effects of MIF on trophoblast invasion could be mediated through autocrine or paracrine modulation of trophoblast cytokine production.

Failure of Decidualization and Maternal Immune Tolerance Underlies Uterovascular Resistance in Intra Uterine Growth Restriction.

Failure of uterine vascular transformation is associated with pregnancy complications including Intra Uterine Growth Restriction (IUGR). The decidua and its immune cell populations play a key role in the earliest stages of this process. Here we investigate the hypothesis that abnormal decidualization and failure of maternal immune tolerance in the second trimester may underlie the uteroplacental pathology of IUGR. Placental bed biopsies were obtained from women undergoing elective caesarian delivery of a healthy term pregnancy, an IUGR pregnancy or a pregnancy complicated by both IUGR and preeclampsia. Decidual tissues were also collected from second trimester terminations from women with either normal or high uterine artery Doppler pulsatile index (PI). Immunohistochemical image analysis and flow cytometry were used to quantify vascular remodeling, decidual leukocytes and decidual status in cases vs. controls. Biopsies from pregnancies complicated by severe IUGR with a high uterine artery pulsatile index (PI) displayed a lack of: myometrial vascular transformation, interstitial, and endovascular extravillous trophoblast (EVT) invasion, and a lower number of maternal leukocytes. Apoptotic mural EVT were observed in association with mature dendritic cells and T cells in the IUGR samples. Second trimester pregnancies with high uterine artery PI displayed a higher incidence of small for gestational age fetuses; a skewed decidual immunology with higher numbers of; CD8 T cells, mature CD83 dendritic cells and lymphatic vessels that were packed with decidual leukocytes. The decidual stromal cells (DSCs) failed to differentiate into the large secretory DSC in these cases, remaining small and cuboidal and expressing lower levels of the nuclear progesterone receptor isoform B, and DSC markers Insulin Growth Factor Binding protein-1 (IGFBP-1) and CD10 as compared to controls. This study shows that defective progesterone mediated decidualization and a hostile maternal immune response against the invading endovascular EVT contribute to the failure of uterovascular remodeling in IUGR pregnancies.

Low-Density Lipoprotein Receptor-Related Protein 6 Is Essential for Trophoblast Survival and Invasion.

Remodeling of maternal spiral artery after the implantation of embryo relies on tightly regulated trophoblast functions and is pivotal to ensure the success of pregnancy. Low-density lipoprotein receptor-related protein 6 (LRP6) is implicated in angiogenesis and several vascular diseases, but its function in trophoblast regulation is still not fully understood. We aimed to investigate the involvement of LRP6 in trophoblast functions during maternal spiral artery remodeling. HTR-8/SVneo cells, a trophoblast cell line, were employed to examine the impact of LRP6 knockdown on proliferation, apoptosis, and migration, as well as invasion and tube formation. Expression of matrix metalloproteinases (MMPs), angiogenic factors placental growth factor (PlGF), and vascular endothelial growth factor (VEGF), as well as activation of canonical Wnt/β-catenin signaling pathway, which was involved in artery remodeling process, was also analyzed. Lipoprotein receptor-related protein 6 knockdown suppressed proliferation, migration, invasion, and tube formation, as well as induced apoptosis in HTR-8/SVneo cells. In addition, LRP6 knockdown also significantly decreased expression of MMPs, PlGF, and VEGF and activation of Wnt/β-catenin signaling pathway. Lipoprotein receptor-related protein 6 might positively regulate the remodeling of the maternal artery through both endovascular formation and trophoblast invasion.

Impaired Wnt5a signaling in extravillous trophoblasts: Relevance to poor placentation in early gestation and subsequent preeclampsia.

Defective decidual endovascular trophoblast invasion and subsequent impaired spiral artery remodeling is highly associated with the pathogenesis of preeclampsia (PE). Since there are scant and conflicting data regarding the function of Wnt5a signaling in extravillous trophoblasts (EVT), the aim of this study was to investigate whethere impaired Wnt5a signaling affects the invasive and tube forming capabilities of EVT. Expression levels of Wnt ligands were compared between first trimester chorionic villi of women who later developed PE and women with unaffected pregnancies using publicly available microarray data (GSE12767). Wnt5a expression was examined in placentas using quantitative RT-PCR, Western blot analysis and immunohistochemistry. The function of Wnt5a signaling in EVT was investigated in an immortalized first trimester EVT cell line, HTR-8/SVneo, using small-interfering RNAs, recombinant human Wnt5a (rhWnt5a), and inhibitors of JNK or PKC. Microarray data analysis of the first trimester placentas showed that, among Wnt ligands, Wnt5a expression was significantly lower in women who later developed PE. The mRNA and protein expression levels of Wnt5a were significantly decreased in PE placentas compared with normal term placentas. Wnt5a knockdown significantly suppressed invasion and tube formation of HTR-8/SVneo cells, while the addition of rhWnt5a augmented the cell migration, invasion, and tube formation. Repression of Wnt5a/PKC signaling in HTR-8/SVneo cells inhibited cell invasion, but did not alter cell tube formation. In contrast, inhibition of Wnt5a/JNK signaling attenuated rhWnt5a-induced invasion and tube formation capabilities. These findings suggest that impaired Wnt5a signaling is associated with poor placentation and subsequent PE.

The impact of uterine immaturity on obstetrical syndromes during adolescence

Pregnant nulliparous adolescents are at increased risk, inversely proportional to their age, of major obstetric syndromes, including preeclampsia, fetal growth restriction, and preterm birth. Emerging evidence indicates that biological immaturity of the uterus accounts for the increased incidence of obstetrical disorders in very young mothers, possibly compounded by sociodemographic factors associated with teenage pregnancy. The endometrium in most newborns is intrinsically resistant to progesterone signaling, and the rate of transition to a fully responsive tissue likely determines pregnancy outcome during adolescence. In addition to ontogenetic progesterone resistance, other factors appear important for the transition of the immature uterus to a functional organ, including estrogen-dependent growth and tissue-specific conditioning of uterine natural killer cells, which plays a critical role in vascular adaptation during pregnancy. The perivascular space around the spiral arteries is rich in endometrial mesenchymal stem-like cells, and dynamic changes in this niche are essential to accommodate endovascular trophoblast invasion and deep placentation. Here we evaluate the intrinsic (uterine-specific) mechanisms that predispose adolescent mothers to the great obstetrical syndromes and discuss the convergence of extrinsic risk factors that may be amenable to intervention.

The role of the placenta in the initiation of spiral artery remodelling in an early pregnant chimpanzee uterus

IntroductionIn this study we evaluated the full extent of placental bed changes (centre to periphery) in a pregnant chimpanzee uterus, kept at the Museum for Central Africa in Tervuren, Belgium. According to placental size the specimen was equivalent to an 8 weeks pregnant human uterus. MethodsHistological sections from central to peripheral tissue blocks of the placental bed were stained to reveal the presence of trophoblast, endothelium, vascular smooth muscle and elastic laminae. As an indicator for early arterial remodelling, we evaluated endothelial nuclear rounding and subendothelial vascular changes within the maternal vasculature in decidua and adjacent inner myometrium. ResultsWhile interstitially invading trophoblasts were present, endovascular trophoblast invasion seemed about to start into one spiral artery outlet at the centre of the placental bed, confirming our previous impression of a later onset of endovascular trophoblast invasion as compared to the human. An early sign of spiral artery remodelling was rounding of the endothelial nuclei. This phenomenon was not related to the local presence of interstitial trophoblast. DiscussionEndothelial nuclear rounding turned out to be a feature of the placental bed as a whole, being significantly less prominent in the adjacent non-placental bed part of the uterus, indicating an effect of the presence of the placenta. The different time-course of early spiral artery remodelling in the chimpanzee as compared to the human may have had a significant impact upon our evolution.

Notch signalling in placental development and gestational diseases

Activation of Notch signalling upon cell-cell contact of neighbouring cells controls a plethora of cellular processes such as stem cell maintenance, cell lineage determination, cell proliferation, and survival. Accumulating evidence suggests that the pathway also critically regulates these events during placental development and differentiation. Herein, we summarize our present knowledge about Notch signalling in murine and human placentation and discuss its potential role in the pathophysiology of gestational disorders. Studies in mice suggest that Notch controls trophectoderm formation, decidualization, placental branching morphogenesis and endovascular trophoblast invasion. In humans, the particular signalling cascade promotes formation of the extravillous trophoblast lineage and regulates trophoblast proliferation, survival and differentiation. Expression patterns as well as functional analyses indicate distinct roles of Notch receptors in different trophoblast subtypes. Altered effects of Notch signalling have been detected in choriocarcinoma cells, consistent with its role in cancer development and progression. Moreover, deregulation of Notch signalling components were observed in pregnancy disorders such as preeclampsia and fetal growth restriction. In summary, Notch plays fundamental roles in different developmental processes of the placenta. Abnormal signalling through this pathway could contribute to the pathogenesis of gestational diseases with aberrant placentation and trophoblast function.

Spatiotemporal expression profile of proteases and immunological, angiogenic, hormonal and apoptotic mediators in rat placenta before and during intrauterine trophoblast migration.

The gene and/or protein expression of proteases and immunological, angiogenic, hormonal and apoptotic mediators was evaluated in rat placenta before and during intrauterine trophoblast migration. The depth of interstitial and endovascular intrauterine trophoblast invasion and the immunohistochemical expression of vascular endothelial growth factor (VEGF), fetal liver kinase 1 (Flk1), interferon (IFN)-γ, migration inhibitory factor (MIF), and inducible nitric oxide synthase (iNOS; also known as nitric oxide synthase (NOS) 2) were evaluated. In addition, the expression of the Vegf, Flk1, placental growth factor (Pigf), soluble fms-like tyrosine kinase 1 (sFlt1), placental lactogen 1 (Pl1), proliferin-related protein (rPlf), placental leptin (Lep), Toll-like receptor 2 (Tlr2), Toll-like receptor 4 (Tlr4), Infg, Mif, tumour necrosis factor-α (Tnf), interleukin-10 (Il10), Nos2, caspase 3 (Casp3), Bax, Bcl2, matrix metalloproteinase 2 (Mmp2) and matrix metalloproteinase 9 (Mmp9) genes was determined by real-time reverse transcription-polymerase chain reaction. At 10 days gestation, gene expression of Tlr2, Tlr4, Tnf, Infg, Il10, Casp3, Pigf, sFlt1 and Lep (P<0.05) were higher than at 14 and/or 19 days of gestation. The beginning of intrauterine trophoblast invasion, i.e., at 14 days of gestation, coincided with higher gene and/or protein expression of MMP9, VEGF, Flk1, NOS2, MIF, BAX and rPlf compared to days 10 and 19 (P<0.05). In contrast, gene expression of Mmp2 and Pl1 was higher at the end of trophoblast invasion compared to 10 and 14 days of gestation (P<0.05). In conclusion, before intrauterine trophoblast migration, expression of TLRs and immunological and pro-apoptotic mediators is higher, whereas the beginning of trophoblast migration is characterised by higher expression of the pro-angiogenic factors NOS2 and MMP9. In contrast, MMP2 and PL1 expression is higher at the end of intrauterine trophoblast migration.

Cyclic fluctuation of bleeding time and clotting time in various phases of menstrual cycle

Background: The physiologic mechanisms whereby the human endometrium maintains hemostasis during endovascular trophoblast invasion, yet permits menstrual hemorrhage, are unknown. Aims and Objective: To find out whether hemostatic responses alter during various phases of normal menstruation. Materials and Methods: In this study height, weight, body mass index, pulse, and blood pressure were measured in 60 female volunteers having normal, regular menstrual cycle. Bleeding and clotting time were measured during three phases of single menstrual cycle: menstrual, follicular, and luteal. One-way analysis of variance test with Bonferroni correction was used to find out statistical significance. Results: This study shows mean bleeding time at follicular phase was significantly (P 0.05). Conclusion: Our observations indicate that primary and secondary hemostatic mechanism activities are at their high in the follicular phase than in the luteal and menstrual phases.

Maternal thyroid dysfunction affects placental profile of inflammatory mediators and the intrauterine trophoblast migration kinetics

The objective of the present study was to evaluate the gene and immunohistochemical expression of inflammatory mediators involved in the immune activity and the intrauterine trophoblast migration of the placentas in hypothyroid and L-thyroxine (L-T4)-treated rats. A total of 144 adult female rats were divided equally into hypothyroid, l-T4-treated, and euthyroid (control) groups. Hypothyroidism was induced by daily administration of propylthiouracil. Rats were killed at 0, 10, 14, 15, 16, 17, 18, and 19 days of gestation. We evaluated the depth of interstitial and endovascular intrauterine trophoblast invasion and the immunohistochemical expression of interferon γ (INFy), migration inhibitory factor (MIF), and inducible nitric oxide synthase (NOS2 (iNOS)). The gene expression of Toll-like receptor 2 (Tlr2) and Tlr4, Infy, Mif, tumor necrosis factor (Tnf (Tnfα)), Il10, Nos2, matrix metalloproteinase 2 (Mmp2) and Mmp9, and placental leptin was also measured in placental disks by real-time RT-PCR. The data were analyzed using an Student-Newman-Keuls (SNK) test. Hypothyroidism reduced the endovascular and interstitial trophoblast migration, and the expression of TLR4, INFy, MIF, interleukin 10 (IL10), NOS2, MMP2 and MMP9, and placental leptin, while increased the expression of TLR2 (P<0.05). T4-treated rats not only increased the expression of IL10 and NOS2 but also reduced the expression of TNF and MIF at 10 days of gestation (P<0.05). However, at 19 days of gestation, expression of INFy and MIF was increased in T4-treated group (P<0.05). Excess of T4 also increased the gene expression of Mmp2 at 10 days of gestation (P<0.05), but reduced the endovascular trophoblast migration at 18 days of gestation (P<0.05). Hypothyroidism and excess of T4 differentially affect the immune profile and the intrauterine trophoblast migration of the placenta, and these effects are dependent on the gestational period.

Macroscopic and microscopic findings of the placenta in women with polycystic ovary syndrome

Do patients with polycystic ovary syndrome (PCOS) have macroscopic and/or microscopic placental alterations? The placental structure in patients with PCOS, even in those with uncomplicated pregnancy, is altered. The spectrum of pregnancy complications seems to have a common denominator: a defective trophoblast invasion and placentation. In women with PCOS, alterations in endovascular trophoblast invasion related to insulin resistance and hyperandrogenism have been observed. For this prospective case-control study, 30 pregnant patients with PCOS (cases) and 60 healthy pregnant women without PCOS features (controls) were enrolled and studied until delivery. Clinical, biochemical, ultrasonographic and obstetric data were recorded. The baseline clinical and biochemical data for screening for PCOS and for inclusion/exclusion were obtained before the seventh week of gestation. At delivery, placentas were collected and detailed macroscopic and microscopic analyses were performed. Cases and controls were matched for age and BMI (all <30 kg/m(2)). The matching procedure was one-to-two. Only subjects with spontaneous conception and uncomplicated pregnancies were included in the final analysis. Placental weight (P = 0.04), thickness (P = 0.02), density (P = 0.02) and volume (P = 0.01) were significantly inferior in women with, compared with those without PCOS. The placentas from patients with PCOS more frequently had an irregular shape (P = 0.03) and a higher cord coiling index (P = 0.02). Differences between cases and controls also concerned the extent of villous (P = 0.04) and intervillous (P = 0.01) spaces, the extent of fibrosis (P = 0.03), endovascular trophoblast (depth, extension and morphometry) (P < 0.05) and mitotic activity (P = 0.01). The percentage of patients with lesions [22/30 (73.3%) versus 25/60 (41.7%), respectively; P = 0.01] and the mean number of placental lesions (3.5 ± 2.1 versus 1.4 ± 1.1, respectively; P = 0.02) were higher in the PCOS than the control group. The odds ratio for placental alterations, adjusted for weight gain, was 2.8 (95% confidence interval 1.3-9.9). The main limitation of the study was the selection of a specific PCOS sample, which is probably not representative of the PCOS phenotype as a whole. In fact, we excluded patients with PCOS who were obese and who achieved a pregnancy following the use of ovulation inductors or assisted reproduction techniques. The present study is the first to demonstrate that the morphology and microscopic structure of placenta in patients with PCOS with an uncomplicated pregnancy are altered. Further studies are needed to assess a correlation of these changes with the increased risk of obstetric complications observed in some pregnancies of women with PCOS. The authors declare no conflict of interest and no financial support for the research. N/A.

Trophoblast invasion and oxygenation of the placenta: measurements versus presumptions

Invasion of extravillous trophoblast into maternal tissues has a profound effect on the oxygenation of the placenta and hence the fetus. The main route of trophoblast invasion is interstitial invasion into the tissues of the decidua and myometrium. From this main route side branches reach the spiral arteries (endovascular trophoblast) as well as the uterine glands (endoglandular trophoblast) to open both structures toward the intervillous space. This enables histiotrophic nutrition in the first trimester and hemotrophic nutrition in the second and third trimesters of pregnancy. Failure of endovascular trophoblast invasion has profound effects on the oxygenation of the placenta. Interestingly, this does not lead to hypoxia as has long been presumed. Rather, all measurements available today point to increased oxygen levels within the placenta in patients with a failure of spiral artery transformation. This should lead to a rethink regarding pathological conditions such as intrauterine growth restriction and preeclampsia.

The role of FOXO1 in the decidual transformation of the endometrium and early pregnancy

Successful pregnancy requires coordination of embryo development, decidualization of endometrium, and placenta formation. Decidualization denotes the transformation of endometrial stromal cells into specialized secretory cells, a process further characterized with influx of specialized immune cells into stroma, predominantly uterine natural killer cells and macrophages, and vascular remodeling. This differentiation process depends on the convergence of the cyclic adenosine monophosphate and progesterone signaling pathways. The decidual process is indispensable for the formation of a functional feto-maternal interface as it controls tissue homeostasis during endovascular trophoblast invasion and bestows tissue resistance to environmental stress signals, including protection against oxidative cell death. FOXO proteins have emerged as key mediators of cell fate because of their ability to regulate either pro-apoptotic genes or genes involved in differentiation, cell cycle arrest, oxidative defenses, and DNA repair. In the endometrium, FOXO1 is of particular importance as a critical regulator of progesterone-dependent differentiation, menstrual shedding, and protection of the feto-maternal against oxidative damage during pregnancy.

Decidual Endovascular Trophoblast Invasion in Women with Polycystic Ovary Syndrome: An Experimental Case-Control Study

Previous experimental and clinical data suggest impaired decidual trophoblast invasion in patients with polycystic ovarian syndrome (PCOS). The objective of the study was to test the hypothesis that decidual endovascular trophoblast invasion in pregnant patients with PCOS is impaired and to clarify the potential mechanisms involved. This was an experimental case-control study. The study was conducted at the academic Departments of Obstetrics and Gynecology and the Unit of Pathology (Italy). Forty-five pregnant subjects screened from a wide population of women waiting for legal pregnancy termination were included in the final analysis. Specifically, 15 pregnant patients with PCOS were enrolled as cases and another 30 age- and body mass index (BMI)-matched healthy pregnant women without any feature of PCOS were enrolled as the controls. Interventions included the collection of trophoblastic and decidual tissue at the 12th week of gestation. Clinical, ultrasonographic, and biochemical data as well as the histological analysis of decidual endovascular trophoblast invasion. The rate of implantation site vessels with endovascular trophoblast invasion (ratio between total number of implantation site vessels and total number of vessels with endovascular trophoblast invasion) and the extent of endovascular trophoblast invasion (proportion between immunoreactive areas to cytokeratin 7 and to CD34) were significantly lower in patients with PCOS compared with healthy non-PCOS controls. Endovascular trophoblast invasion data were significantly and indirectly related to the markers of insulin resistance and testosterone concentrations in PCOS patients. Pregnant patients with PCOS patients have impaired decidual trophoblast invasion. Further studies are needed to evaluate the exact mechanisms through which insulin resistance and hyperandrogenemia exert this effect.

Obstetric Antiphospholipid Syndrome: An Update on Pathophysiology and Management

Antiphospholipid antibodies (aPLs) are acquired antibodies directed against negatively charged phospholipids, a group of inner and outer cell membrane antigens found in mammals. Obstetric antiphospholipid antibody syndrome (APS) is diagnosed in the presence of certain clinical features in conjunction with positive laboratory findings. Although obstetric APS was originally reported in association with slow progressive thrombosis and infarction in the placenta, it is most often associated with a poor obstetric outcome. In fact, obstetric APS is one of the most commonly identified causes of recurrent pregnancy loss (RPL). Thus obstetric APS is distinguished from APS in other organ systems where the most common manifestation is thrombosis. Several pathophysiological mechanisms of action of aPLs have been described. The most common histopathological finding in early pregnancy loss has been defective endovascular decidual trophoblastic invasion. Treatment with heparin and aspirin is emerging as the therapy of choice, with ∼75% of treated women with RPL and aPLs having a successful delivery compared with <50% without treatment. This review highlights the diagnostic challenges of obstetric APS, the obstetric complications associated with APS, proposed pathophysiological mechanisms of APS during pregnancy, and the management of women during and after pregnancy.

Placental Insufficiency and Fetal Growth Restriction

Fetal growth restriction is defined as a pathologic decrease in the rate of fetal growth. The most frequent etiology for late onset fetal growth restriction is uteroplacental dysfunction which is due to inadequate supply of nutrients and oxygen to support normal aerobic growth of the fetus. However, for symmetrical IUGR, fetal chromosomal anomalies, structural anomalies and fetal infections should be carefully excluded. Consequent to the uteroplacental vascular maladaptation of endovascular trophoblastic invasion, there is increased vascular resistance and decreased blood flow to the placenta in the choriodecidual compartment. This under perfusion of the placenta causes villous damage; that is, total tertiary villous capillary bed is reduced leading to increased placental resistance. These changes can be diagnosed by Doppler and characteristic changes are seen in the uterine, umbilical, middle cerebral arteries and ductus venosus vessels. In severe cases, delivery of the fetus with optimum intrapartum surveillance, or caesarean section, is essential.

Deep trophoblast invasion and spiral artery remodelling in the placental bed of the chimpanzee

Deep trophoblast invasion is usually considered to be a unique feature of human placentation as compared to other primates. Because of the occasional occurrence of preeclampsia in great apes, which in the human is associated with impaired deep invasion, this uniqueness may be questioned. The availability of two well-documented pregnant chimpanzee uteri in the Hubrecht Collection (Museum für Naturkunde, Berlin) allowed us to evaluate the extent of trophoblast invasion in this species. By adjusting currently used protocols, we obtained successful immunohistochemical staining for cytokeratin and α-actin, as well as Ulex europaeus agglutinin 1 (UEA1) lectin staining, in this archival material. In both specimens interstitial trophoblast invasion had occurred in both decidua and myometrium. Because of a lack of published data on fetal growth for this species, fetal sizes (7 cm and 13 cm) could not be strictly related to gestational ages and thus be compared with the time-course of human trophoblast invasion. However, since the earlier specimen did not show any endovascular trophoblast invasion in spiral arteries – in contrast to pregnant human uteri with equivalent fetal sizes – endovascular migration seems to begin at a different gestational age in the chimpanzee. In the later specimen endovascular trophoblast was associated with spiral artery remodelling in the inner myometrium, and this invasion was extended to include a radial artery, which at that stage still showed relatively intact vascular smooth muscle and elastic lamina. We conclude that invasion depth and spiral artery remodelling are basically similar in chimpanzees and humans, although the seemingly different time of onset may have implications for uteroplacental oxygen supply and fetal development.

The Implication of Aberrant GM-CSF Expression in Decidual Cells in the Pathogenesis of Preeclampsia

Preeclampsia is characterized by an exaggerated systemic inflammatory state as well as shallow placentation. In the decidual implantation site, preeclampsia is accompanied by an excessive number of both macrophages and dendritic cells as well as their recruiting chemokines, which have been implicated in the impairment of endovascular trophoblast invasion. Granulocyte-macrophage colony-stimulating factor is known to regulate the differentiation of both macrophages and dendritic cells, prompting both in vivo and in vitro evaluation of granulocyte-macrophage colony-stimulating factor expression in human decidua as well as in a mouse model of preeclampsia. This study revealed increased granulocyte-macrophage colony-stimulating factor expression levels in preeclamptic decidua. Moreover, both tumor necrosis factor-α and interleukin-1 β, cytokines that are implicated in the genesis of preeclampsia, markedly up-regulated granulocyte-macrophage colony-stimulating factor production in cultured first-trimester human decidual cells. The conditioned media of these cultures promoted the differentiation of both macrophages and dendritic cells from a monocyte precursor. Evaluation of a murine model of preeclampsia revealed that the decidua of affected animals displayed higher levels of immunoreactive granulocyte-macrophage colony-stimulating factor as well as increased numbers of both macrophages and dendritic cells when compared to control animals. Because granulocyte-macrophage colony-stimulating factor is a potent inducer of differentiation and activation of both macrophages and dendritic cells, these findings suggest that this factor plays a crucial role in the pathogenesis of preeclampsia.

M11.4 Risk factors for preeclampsia in obese nulliparous women

Hypertensive disorders constitute the most common medical complications of pregnancy. In normal pregnancy, impressive physiological changes take place in the maternal cardiovascular system. Morphological changes are the result of invasion of migratory trophoblast cells into the walls of the spiral arteries. After destruction of elastic, muscular and neural tissue in the media, the trophoblast cells get incorporated into the vessel wall and the endothelial lining of the spiral arteries is restored. The physiological changes create a low-resistance, low-pressure, high-flow system with the absence of maternal vasomotor control. Biochemical adaptations in maternal vasculature include changes in the prostaglandin system, the renin–angiotensin–aldosteron system and the kallikrein–kinin system.In preeclampsia, physiological changes in the spiral arteries are confined to the decidual portion of the arteries. Myometrial segments remain anatomically intact and fail to dilate. In addition, the adrenergic nerve supply is left intact. The cause of this impaired endovascular trophoblast invasion is not yet elucidated. But in combination with the imbalance between vasodilator and vasoconstrictor eicosanoids, it gives rise to reduced perfusion of the intervillous space. In the absence of an adequate production of antiaggregatory prostacyclin (PGI2), nitric oxide, or both, surface-mediated platelet activation is supposed to occur on the surface of the spiral arteries. Because platelets are the principal source of circulating serotonin, the increased platelet aggregation in preeclampsia causes an increase in serotonin levels. Interaction of serotonin with serotonin1- or serotonin2-receptors depends on the state of the endovascular trophoblast or endothelium in the spiral arteries and has opposite effects with regard to vasodilating and vasoconstrictive influences.