Human cytotrophoblasts promote endothelial survival and vascular remodeling through secretion of Ang2, PlGF, and VEGF-C

Trophoblast-derived factors drive human mesenchymal stem cell differentiation along an endothelial lineage: A model of early placental vasculogenesis

Mechanisms controlling the process and patterning of blood vessel development in the placenta remain largely unknown. The close physical proximity of early blood vessels observed in the placenta and the cytotrophoblast, as well as the reported production of vasculogenic growth factors by the latter, suggests that signalling between these two niches may be important. Here, we have developed an in vitro model to address the hypothesis that the cytotrophoblast, by the secretion of soluble factors, drives differentiation of resident sub-trophoblastic mesenchymal stem cells (MSCs) along a vascular lineage, thereby establishing feto-placental circulation. BM-MSCs (a readily available model for placental stem cells) were treated with conditioned medium containing the secretome from human BeWo trophoblast cells, or endothelial growth medium (EGM2) supplemented with exogenous growth factors (VEGF, IGF1 and EGF) for 10-12 days. Trophoblast-conditioned media, found to contain detectable concentrations of cytokines including VEGF, uPAR, TIMP-1, TIMP-2, IL6 and placental growth factor, induced the expression of the endothelial genes CD31, von Willibrand factor (vWF), FLT-1, VEGFR2 and VE-Cadherin. Upregulation of vWF protein was also detected following growth in trophoblast-conditioned media, using immunocytochemistry. Wound healing (migration assay) and Matrigel-tube formation assays confirmed that the BM-MSCs cultured in trophoblast-conditioned media exhibited functional measures of endothelial cells in addition to expressing relevant markers. Identification of key trophoblast-secreted factors and their promotion of endothelial differentiation in BM-MSCs helps advance our theories regarding the close relationship of the mesenchymal stem cell-cytotrophoblast niche in coordinating the complex angiogenic events that occur in the placenta. The in vitro model presented here provides an accessible and reproducible tool for further investigations into placental development.

Placental Vascular Anastamoses and Associated Pathologies in Dichorionic Twin Gestations

Placental vascular anastomoses are traditionally thought to exist exclusively in monochorionic pregnancies. However, they have been reported in dichorionic twin pregnancies as well. In turn, twin to twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS) have also been noted to impact some of these gestations. Through discussion of one such case at our institution along with a review of the available literature, we review the proposed pathophysiology of placental vascular anastamoses in dichorionic twin gestations, and aim to raise awareness of the possibility of associated pathologies in dichorionic gestations. This is an emerging area of literature that will require future study to guide prenatal surveillance and mitigate morbidity.

CREB1 Is Involved in miR-134-5p-Mediated Endometrial Stromal Cell Proliferation, Apoptosis, and Autophagy

The successful establishment of endometrial receptivity is a key factor in ensuring the fertility of ewes and their economic benefits. Hu sheep have attracted attention due to their high fecundity and year-round estrus. In this study, we found that in the luteal phase, the uterine gland density, uterine coefficient, and number of uterine caruncles of high-fertility Hu sheep were higher than those of low-fertility Hu sheep. Thousands of differentially expressed genes were identified in the endometrium of Hu sheep with different fertility potential using RNA sequencing (RNA-Seq). Several genes involved in endometrial receptivity were screened using bioinformatics analysis. The qRT-PCR analysis further revealed the differential expression of cAMP reactive element binding protein-1 (CREB1) in the Hu sheep endometrium during the estrous cycle. Functionally, our results suggested that CREB1 significantly affected the expression level of endometrial receptivity marker genes, promoted cell proliferation by facilitating the transition from the G1 phase to the S phase, and inhibited cell apoptosis and autophagy. Moreover, we observed a negative linear correlation between miR-134-5p and CREB1 in the endometrium. In addition, CREB1 overexpression prevented the negative effect of miR-134-5p on endometrial stromal cell (ESC) growth. Taken together, these data indicated that CREB1 was regulated by miR-134-5p and may promote the establishment of uterine receptivity by regulating the function of ESCs. Moreover, this study provides new theoretical references for identifying candidate genes associated with fertility.

Cytochrome P450 26A1 regulates the clusters and killing activity of NK cells during the peri-implantation period

Cytochrome P450 26A1 (CYP26A1) plays a vital role in early pregnancy in mice. Our previous studies have found that CYP26A1 affects embryo implantation by modulating natural killer (NK) cells, and that there is a novel population of CYP26A1⁺ NK cells in the uteri of pregnant mice. The aim of this study was to investigate the effects of CYP26A1 on the subsets and killing activity of NK cells. Through single-cell RNA sequencing (scRNA-seq), we identified four NK cell subsets in the uterus, namely, conventional NK (cNK), tissue-resident NK (trNK) 1 and 2, and proliferating trNK (trNKp). The two most variable subpopulations after uterine knockdown of CYP26A1 were trNKp and trNK2 cells. CYP26A1 knockdown significantly downregulated the expression of the NK cell function-related genes Cd44, Cd160, Vegfc, and Slamf6 in trNK2 cells, and Klra17 and Ogn in trNKp cells. Both RNA-seq and cytotoxicity assays confirmed that CYP26A1⁺ NK cells had low cytotoxicity. These results indicate that CYP26A1 may affect the immune microenvironment at the maternal-foetal interface by regulating the activity of NK cells.

Effect of swimming exercise, insulin-associated or not, on inflammatory cytokines, apoptosis, and collagen in diabetic rat placentas

Physical exercise is an important therapeutic agent for women with diabetes during gestation. However, its histophysiological consequences for the placenta remain unclear. In this study, we evaluated the expression of VEGF-A, IL1ß, TNFα, and type I collagen in the placentas of diabetic rats subjected to a swimming program. Thirty rats were divided into the following groups: CG, pregnant nondiabetic rats; CEG, nondiabetic pregnant rats subjected to swimming; DG, pregnant diabetic rats; DEG, pregnant diabetic rats subjected to swimming; DIG, pregnant diabetic rats treated with insulin; DIEG, pregnant diabetic rats treated with insulin and subjected to swimming. Diabetes was induced using streptozotocin [50 mg/kg intraperitoneally (i.p.)], and insulin was administered at a dose of 5 U/day i.p. (2 U at 10 am and 3 U at 7 pm) in the DIG group; in the DIEG group, insulin was administered at a dose of only 2 U/day at 7 pm. The rats were sacrificed on the 20th day of gestation. There was an increase in the expression of IL-1β, TNF-α, VEGF-A, and type I collagen and a higher apoptotic index in the placentas of the DG and DEG groups, but there was a reduction in glycemia in the latter group. In the DIG and DIEG groups, the levels remained similar to those of the control; however, in these groups the reduction was more significant for all analyzed parameters. Therefore, in rats induced to diabetes during pregnancy, swimming, although reducing glycemic levels, did not prevent immunohistochemical changes in the placenta, suggesting the need for a multidisciplinary protocol associated with traditional pharmacological treatment.

Recent advances in ocular drug delivery systems and targeting VEGF receptors for management of ocular angiogenesis: A comprehensive review

Background

Angiogenic ocular diseases address the main source of vision impairment or irreversible vision loss. The angiogenesis process depends on the balance between the pro-angiogenic and anti-angiogenic factors. An imbalance between these factors leads to pathological conditions in the body. The vascular endothelial growth factor is the main cause of pathological conditions in the ocular region. Intravitreal injections of anti-angiogenic drugs are selective, safe, specific and revolutionized treatment for ocular angiogenesis. But intravitreal injections are invasive techniques with other severe complications. The area of targeting vascular endothelial growth factor receptors progresses with novel approaches and therapeutically based hope for best clinical outcomes for patients through the developments in anti-angiogenic therapy.

Main text

The present review article gathers prior knowledge about the vascular endothelial growth factor and associated receptors with other angiogenic and anti-angiogenic factors involved in ocular angiogenesis. A focus on the brief mechanism of vascular endothelial growth factor inhibitors in the treatment of ocular angiogenesis is elaborated. The review also covers various recent novel approaches available for ocular drug delivery by comprising a substantial amount of research works. Besides this, we have also discussed in detail the adoption of nanotechnology-based drug delivery systems in ocular angiogenesis by comprising literature having recent advancements. The clinical applications of nanotechnology in terms of ocular drug delivery, risk analysis and future perspectives relating to the treatment approaches for ocular angiogenesis have also been presented.

Conclusion

The novel ocular drug delivery systems involving nanotechnologies are of great importance in the ophthalmological sector to overcome traditional treatments with many drawbacks. This article gives a detailed insight into the various approaches that are currently available to be a road map for future research in the field of ocular angiogenesis disease management.

Organophosphate Flame Retardants, Highly Fluorinated Chemicals, and Biomarkers of Placental Development and Disease During Mid-Gestation

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) and organophosphate flame retardants (OPFRs) are chemicals that may contribute to placenta-mediated complications and adverse maternal-fetal health risks. Few studies have investigated these chemicals in relation to biomarkers of effect during pregnancy. We measured 12 PFASs and four urinary OPFR metabolites in 132 healthy pregnant women during mid-gestation and examined a subset with biomarkers of placental development and disease (n = 62). Molecular biomarkers included integrin alpha-1 (ITGA1), vascular endothelial-cadherin (CDH5), and matrix metalloproteinase-1 (MMP1). Morphological endpoints included potential indicators of placental stress and the extent of cytotrophoblast (CTB)-mediated uterine artery remodeling. Serum PFASs and urinary OPFR metabolites were detected in ∼50%-100% of samples. The most prevalent PFASs were perfluorononanoic acid (PFNA), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonic acid (PFOS), with geometric mean (GM) levels of ∼1.3-2.8 (95% confidence limits from 1.2-3.1) ng/ml compared to ≤0.5 ng/ml for other PFASs. Diphenyl phosphate (DPhP) and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) were the most prevalent OPFR metabolites, with GMs of 2.9 (95% CI: 2.5-3.4) and 3.6 (95% CI: 2.2-3.1) ng/ml, respectively, compared to <1 ng/ml for bis(2-chloroethyl) phosphate (BCEP) and bis(1-chloro-2-propyl) phosphate (BCIPP). We found inverse associations of PFASs or OPFRs with ITGA1 or CDH5 immunoreactivity and positive associations with indicators of placental stress in multiple basal plate regions, indicating these chemicals may contribute to abnormal placentation and future health risks. Associations with blood pressure and lipid concentrations warrant further examination. This is the first study of these chemicals with placental biomarkers measured directly in human tissues and suggests specific biomarkers are sensitive indicators of exposure during a vulnerable developmental period.

Conditioned medium from primary cytotrophoblasts, primary placenta-derived mesenchymal stem cells, or sub-cultured placental tissue promoted HUVEC angiogenesis in vitro

Background

As a large capillary network, the human placenta plays an important role throughout pregnancy. Placental vascular development is complex and delicate and involves many types of placental cells, such as trophoblasts, and mesenchymal stem cells. There has been no systematic, comparative study on the roles of these two groups of placental cells and the whole placental tissue in the placental angiogenesis. In this study, primary cytotrophoblasts (CTBs) from early pregnancy and primary human placenta-derived mesenchymal stem cells (hPDMSCs) from different stages of pregnancy were selected as the cell research objects, and full-term placental tissue was selected as the tissue research object to detect the effects of their conditioned medium (CM) on human umbilical vein endothelial cell (HUVEC) angiogenesis.

Methods

We successfully isolated primary hPDMSCs and CTBs, collected CM from these placental cells and sub-cultured placental tissue, and then evaluated the effects of the CM on a series of angiogenic processes in HUVECs in vitro. Furthermore, we measured the levels of angiogenic factors in the CM of placental cells or tissue by an angiogenesis antibody array.

Results

The results showed that not only placental cells but also sub-cultured placental tissue, to some extent, promoted HUVEC angiogenesis in vitro by promoting proliferation, adhesion, migration, invasion, and tube formation. We also found that primary placental cells in early pregnancy, whether CTBs or hPDMSCs, played more significant roles than those in full-term pregnancy. Placental cell-derived CM collected at 24 h or 48 h had the best effect, and sub-cultured placental tissue-derived CM collected at 7 days had the best effect among all the different time points. The semiquantitative angiogenesis antibody array showed that 18 of the 43 angiogenic factors had obvious spots in placental cell-derived CM or sub-cultured placental tissue-derived CM, and the levels of 5 factors (including CXCL-5, GRO, IL-6, IL-8, and MCP-1) were the highest in sub-cultured placental tissue-derived CM.

Conclusions

CM obtained from placental cells (primary CTBs or hPDMSCs) or sub-cultured placental tissue contained proangiogenic factors and promoted HUVEC angiogenesis in vitro. Therefore, our research is helpful to better understand placental angiogenesis regulation and provides theoretical support for the clinical application of placental components, especially sub-cultured placental tissue-derived CM, in vascular tissue engineering and clinical treatments.

[Comparative morphofunctional analysis of the state of fetoplacental complex in diabetes mellitus (literature review)]

This article reviews the literature on placental morphofunctional changes in placenta of patients with type 1 and type 2 diabetes mellitus and gestational diabetes mellitus. The detailed analysis of features of pathogenesis of various abnormalities of the fetoplacental complex depending on the type of diabetes, its influence on the formation of the placental vascular bed. The analysis of mechanisms of development of placenta formation disorders, pathologies of placental vascular bed, the role of hyperglycemia and hyperinsulinemia in villous maturation, placental weight gain, perinatal outcomes. The discussed anomalies have a significant impact on the fetoplacental complex, acting as epigenetic factors, forming the environment for the fetus, which may later affect the health of the unborn child. They lead to adverse perinatal outcomes, including high infant morbidity and mortality. Literature search was performed in Russian (eLibrary, CyberLeninka.ru) and international (PubMed, Cochrane Library) databases in Russian and English languages. The free access to the full text of the articles was in priority. The selection of sources was prioritized for the period from 2016 to 2020. However, due to the lack of knowledge of the chosen topic, the selection of sources was dated from 2001.

Lymphatic mimicry in maternal endothelial cells promotes placental spiral artery remodeling

Molecular heterogeneity of endothelial cells underlies their highly specialized functions during changing physiological conditions within diverse vascular beds. For example, placental spiral arteries (SAs) undergo remarkable remodeling to meet the ever-growing demands of the fetus - a process which is deficient in preeclampsia. The extent to which maternal endothelial cells coordinate with immune cells and pregnancy hormones to promote SA remodeling remains largely unknown. Here we found that remodeled SAs expressed the lymphatic markers PROX1, LYVE1, and VEGFR3, mimicking lymphatic identity. Uterine natural killer (uNK) cells, which are required for SA remodeling and secrete VEGFC, were both sufficient and necessary for VEGFR3 activation in vitro and in mice lacking uNK cells, respectively. Using Flt4Chy/+ mice with kinase inactive VEGFR3 and Vegfcfl/fl Vav1-Cre mice, we demonstrated that SA remodeling required VEGFR3 signaling, and that disrupted maternal VEGFR3 signaling contributed to late-gestation fetal growth restriction. Collectively, we identified a novel instance of lymphatic mimicry by which maternal endothelial cells promote SA remodeling, furthering our understanding of the vascular heterogeneity employed for the mitigation of pregnancy complications such as fetal growth restriction and preeclampsia.

Association of polybrominated diphenyl ether (PBDE) levels with biomarkers of placental development and disease during mid-gestation

BACKGROUND

Polybrominated diphenyl ether (PBDE) exposures have been associated with adverse pregnancy outcomes. A hypothesized mechanism is via alterations in placental development and function. However, we lack biomarkers that can be used as early indicators of maternal/fetal response to PBDE exposures and/or perturbations in placental development or function.

METHODS

To evaluate the relationship between PBDE levels and placental biomarkers during mid-gestation of human pregnancy (n = 62), we immunolocalized three molecules that play key roles in cytotrophoblast (CTB) differentiation and interstitial/endovascular uterine invasion-integrin alpha-1 (ITGA1), vascular endothelial-cadherin (CDH5), and metalloproteinase-1 (MMP1)-and assessed three morphological parameters as potential indicators of pathological alterations using H&E-stained tissues-leukocyte infiltration, fibrinoid deposition, and CTB endovascular invasion. We evaluated associations between placental PBDE levels and of biomarkers of placental development and disease using censored Kendall's tau correlation and linear regression methods.

RESULTS

PBDEs were detected in all placental samples. We observed substantial variation in antigen expression and morphological endpoints across placental regions. We observed an association between PBDE concentrations and immunoreactivity of endovascular CTB staining with anti-ITGA1 (inverse) or interstitial CTBs staining with anti-CDH5 (positive).

CONCLUSIONS

We found several molecular markers that may be sensitive placental indicators of PBDE exposure. Further, this indicates that placental biomarkers of development and disease could be useful barometers of exposure to PBDEs, a paradigm that could be extended to other environmental chemicals and placental stage-specific antigens.

Histopathological study with immunohistochemical expression of vascular endothelial growth factor in placentas of hyperglycemic and diabetic women

AIMS AND OBJECTIVES

Spectrum of hyperglycemia in pregnancy includes gestational diabetes mellitus (GDM), mild hyperglycemia, and overt diabetes. Many authors have worked on morphological changes of the placenta in diabetes, but few studies have correlated histopathological changes with vascular endothelial growth factor (VEGF) immunoexpression. The aim of this study was to detect different histopathological changes in various groups of diabetic placentas and to correlate with VEGF immunoexpression.

MATERIALS AND METHODS

Pregnant women were screened for diabetes. They were subsequently divided into normoglycemic (12 cases), GDM (33 cases), mild hyperglycemic (13 cases), and overt diabetes (18 cases). Placentas collected were subjected to histopathological examination. VEGF expressions were studied by immunohistochemistry.

RESULTS

Overt diabetic placenta displayed villous immaturity (44.4%), villous edema (38.9%), chorangiosis (61.1%), fibrinoid substance deposition (38.9%), and Hofbauer cell hyperplasia in 44.4% cases. GDM placentas displayed villous immaturity (45.5%), villous edema (45.5%), chorangiosis (42.4%), and fibrinoid substance deposition in 75.6% cases. Mild hyperglycemic placentas displayed villous immaturity (38.5%), chorangiosis (61.5%), and fibrinoid substance deposition in 61.5% cases. VEGF immunoexpression in GDM placentas was absent in all placental components except syncytiotrophoblast. VEGF expression in overt diabetic placentas was increased in syncytiotrophoblast and capillary endothelium compared to normoglycemic placentas. Mild hyperglycemic placentas expressed similar VEGF expression in all components when compared to normoglycemic controls. However, it displayed weak expression in vessel endothelium.

CONCLUSION

Histopathological changes in diabetic placentas might be a consequence of altered or abnormal VEGF expression in diabetic placentas. Pathogenesis and VEGF expression in GDM placentas are significantly different from overt diabetic placentas.

The role of hepatic sinusoidal obstruction in the pathogenesis of the hepatic involvement in HELLP syndrome: Exploring the literature

AIM

This study aims to determine, based on existing data, whether the mechanism resulting in liver dysfunction in HELLP syndrome resembles that in Sinusoidal Obstruction Syndrome (SOS).

BACKGROUND

HELLP syndrome is a serious pregnancy disorder with high maternal and perinatal morbidity and mortality rates. Because of poor insight in its pathophysiology, particularly that of the liver involvement, clinical management is limited to symptomatic treatment, often followed by termination of pregnancy. SOS is a rare, potentially life-threatening complication of radio and/ or chemotherapy in the preparation of hematopoietic cell transplantation. The etiology of liver dysfunction in SOS is - unlike that in HELLP syndrome - better-understood and seems to be initiated by direct toxic damage and demise of endothelial cells, causing hepatic sinusoidal obstruction and ischemia.

METHODS

We searched Pubmed, Embase and Cochrane for reports on the etiology of HELLP and SOS. This yielded 73 articles, with 14 additional reports from the references listed in these articles.

RESULTS

The dysfunctional placenta in women developing HELLP initiates a cascade of events that eventually results in liver dysfunction. The placenta releases, besides anti-angiogenetic factors, also necrotic debris and cell-free DNA, a mixture that not only induces systemic endothelial dysfunction as in preeclampsia, but also a systemic inflammatory response. The latter aggravates the endothelio-toxic effects in the systemic cardiovascular bed, amplifying the already increased pro-thrombotic conditions. Particularly in microcirculations with extremely low shear forces, such as in the hepatic sinusoids, this will facilitate microthrombi formation and fibrin deposition eventually resulting in obstruction of the sinusoids similar as in SOS. The latter causes ischemic damage and progressive demise of hepatocytes.

CONCLUSION

The available information supports the concept that the liver damage in HELLP and SOS results from sinusoidal ischemia, presumably resulting from partially overlapping pathophysiological mechanisms.

Presence of trophoblast in the uterine lumen affects VEGF-C expression in porcine endometrium

Early pregnancy is associated with morphological and functional changes within the uterus, accompanied by angiogenesis, increased vascular permeability and activation of immune tolerance. Intensive angiogenesis leads to accelerated vascular leakage and accumulation of interstitial fluid in endometrium. To protect the trophoblast from the harmful effect of extracellular fluid, process known as lymphangiogenesis is crucial. These studies are focused on VEGF-C, factor responsible of lymphatic vessels creating, and its receptors: Flk1 (VEGFR2) and Flt4 (VEGFR3) during the time of implantation as well as the effect of trophoblast signals (IFNG and E2) on VEGF-C production. Endometrial samples were collected from mature gilts from days 8, 10, 12, 14 of estrous cycle and pregnancy. Real-Time PCR analysis revealed increased mRNA expression of VEGF-C on days 10, 12, 14 of pregnancy compared to corresponding days of estrous cycle. The highest VEGF-C mRNA expression was observed on 14 day of pregnancy (p < 0.05). Increased mRNA expression of Flk1 and Flt4 was noticed on day 14 of pregnancy in comparison to day 10. Enhanced Flk1 mRNA expression during 14 day of pregnancy was observed compared to corresponding day of estrous cycle (p < 0.05). No significant difference on the protein level was revealed. VEGF-C and its receptors were localized mainly in luminal and glandular epithelial cells, but their presence were confirmed also in endothelial cells of blood and lymphatic vessels and 14 d trophoblasts. In vitro studies revealed positive effect of IFNG on VEGF-C mRNA expression in stromal cells and protein content in medium after stromal cells culture (p < 0.05). Our studies demonstrated the presence of VEGF-C system in porcine endometrium and indicated its possible important role during the time of implantation.

In vitro placenta barrier model using primary human trophoblasts, underlying connective tissue and vascular endothelium

Fetal development may be compromised by adverse events at the placental interface between mother and fetus. However, it is still unclear how the communication between mother and fetus occurs through the placenta. In vitro - models of the human placental barrier, which could help our understanding and which recreate three-dimensional (3D) structures with biological functionalities and vasculatures, have not been reported yet. Here we present a 3D-vascularized human primary placental barrier model which can be constructed in 1 day. We illustrate the similarity of our model to first trimester human placenta, both in its structure and in its ability to respond to altered oxygen and to secrete factors that cause damage cells across the barrier including embryonic cortical neurons. We use this model to highlight the possibility that both the trophoblast and the endothelium within the placenta might play a role in the fetomaternal dialogue.

Congenital Viral Infection: Traversing the Uterine-Placental Interface

Why certain viruses cross the physical barrier of the human placenta but others do not is incompletely understood. Over the past 20 years, we have gained deeper knowledge of intrauterine infection and routes of viral transmission. This review focuses on human viruses that replicate in the placenta, infect the fetus, and cause birth defects, including rubella virus, varicella-zoster virus, parvovirus B19, human cytomegalovirus (CMV), Zika virus (ZIKV), and hepatitis E virus type 1. Detailed discussions include ( a) the architecture of the uterine-placental interface, ( b) studies of placental explants ex vivo that provide insights into the infection and spread of CMV and ZIKV to the fetal compartment and how these viruses undermine early development, and ( c) novel treatments and vaccines that limit viral replication and have the potential to reduce dissemination, vertical transmission and the occurrence of congenital disease.

Physiological Role of Vascular Endothelial Growth Factors as Homeostatic Regulators

The vascular endothelial growth factor (VEGF) family of proteins are key regulators of physiological systems. Originally linked with endothelial function, they have since become understood to be principal regulators of multiple tissues, both through their actions on vascular cells, but also through direct actions on other tissue types, including epithelial cells, neurons, and the immune system. The complexity of the five members of the gene family in terms of their different splice isoforms, differential translation, and specific localizations have enabled tissues to use these potent signaling molecules to control how they function to maintain their environment. This homeostatic function of VEGFs has been less intensely studied than their involvement in disease processes, development, and reproduction, but they still play a substantial and significant role in healthy control of blood volume and pressure, interstitial volume and drainage, renal and lung function, immunity, and signal processing in the peripheral and central nervous system. The widespread expression of VEGFs in healthy adult tissues, and the disturbances seen when VEGF signaling is inhibited support this view of the proteins as endogenous regulators of normal physiological function. This review summarizes the evidence and recent breakthroughs in understanding of the physiology that is regulated by VEGF, with emphasis on the role they play in maintaining homeostasis. © 2017 American Physiological Society. Compr Physiol 8:955-979, 2018.

Antitumor activity of a novel anti-vascular endothelial growth factor receptor-1 monoclonal antibody that does not interfere with ligand binding

Vascular endothelial growth factor receptor-1 (VEGFR-1) is a tyrosine kinase transmembrane receptor that has also a soluble isoform containing most of the extracellular ligand binding domain (sVEGFR-1). VEGF-A binds to both VEGFR-2 and VEGFR-1, whereas placenta growth factor (PlGF) interacts exclusively with VEGFR-1. In this study we generated an anti-VEGFR-1 mAb (D16F7) by immunizing BALB/C mice with a peptide that we had previously reported to inhibit angiogenesis and endothelial cell migration induced by PlGF. D16F7 did not affect binding of VEGF-A or PlGF to VEGFR-1, thus allowing sVEGFR-1 to act as decoy receptor for these growth factors, but it hampered receptor homodimerization and activation. D16F7 inhibited both the chemotactic response of human endothelial, myelomonocytic and melanoma cells to VEGFR-1 ligands and vasculogenic mimicry by tumor cells. Moreover, D16F7 exerted in vivo antiangiogenic effects in a matrigel plug assay. Importantly, D16F7 inhibited tumor growth and was well tolerated by B6D2F1 mice injected with syngeneic B16F10 melanoma cells. The antitumor effect was associated with melanoma cell apoptosis, vascular abnormalities and decrease of both monocyte/macrophage infiltration and myeloid progenitor mobilization. For all the above, D16F7 may be exploited in the therapy of metastatic melanoma and other tumors or pathological conditions involving VEGFR-1 activation.

Placenta growth factor and neuropilin-1 collaborate in promoting melanoma aggressiveness

The placenta growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family, which shares with VEGF-A the tyrosine kinase receptor VEGFR-1 and the co-receptor neuropilin-1 (NRP-1). In melanoma models, PlGF enhances tumour growth and neovessel formation, whereas NRP-1 promotes the metastatic process. Increased secretion of PlGF and expression of NRP-1 have also been involved in intrinsic or acquired resistance to anti‑angiogenic therapies. In this study we investigated whether PlGF and NRP-1 cooperate in promoting melanoma aggressiveness independently of VEGFR-1. For this purpose, the melanoma cell clones M14-N, expressing NRP-1 and lacking VEGFR-1, and M14-C, devoid of both receptors, were used. M14-N cells are characterized by an invasive phenotype and vasculogenic mimicry, whereas M14-C cells possess a negligible invasive capacity. The results indicated that M14-N cells secrete higher levels of PlGF than M14-C cells and that PlGF is involved in the invasion of the extracellular matrix (ECM) and vasculogenic mimicry of M14-N cells. In fact, neutralizing antibodies against PlGF reverted ECM invasion in response to PlGF and markedly reduced the formation of tubule-like structures. Moreover, M14-N cells migrated in response to PlGF and chemotaxis was specifically abrogated by anti-NRP-1 antibodies, demonstrating that PlGF directly activates NRP-1 in the absence of VEGFR-1. We also compared the levels of PlGF in the plasma of patients affected by metastatic melanoma with those of healthy donors and evaluated whether PlGF levels could be affected by a bevacizumab-containing chemotherapy regimen. Melanoma patients showed a 20-fold increase in plasma PlGF and the bevacizumab-containing regimen induced a reduction of VEGF-A and in a further increase of PlGF. In conclusion, our studies suggest that the activation of NRP-1 by PlGF directly contributes to melanoma aggressiveness and represents a potential compensatory pro-angiogenic mechanism that may contribute to the resistance to therapies targeting VEGF-A.

Placenta: the forgotten organ

The placenta sits at the interface between the maternal and fetal vascular beds where it mediates nutrient and waste exchange to enable in utero existence. Placental cells (trophoblasts) accomplish this via invading and remodeling the uterine vasculature. Amazingly, despite being of fetal origin, trophoblasts do not trigger a significant maternal immune response. Additionally, they maintain a highly reliable hemostasis in this extremely vascular interface. Decades of research into how the placenta differentiates itself from embryonic tissues to accomplish these and other feats have revealed a previously unappreciated level of complexity with respect to the placenta's cellular composition. Additionally, novel insights with respect to roles played by the placenta in guiding fetal development and metabolism have sparked a renewed interest in understanding the interrelationship between fetal and placental well-being. Here, we present an overview of emerging research in placental biology that highlights these themes and the importance of the placenta to fetal and adult health.

Human placenta-derived multipotent mesenchymal stromal cells involved in placental angiogenesis via the PDGF-BB and STAT3 pathways

We studied the smooth muscle cell differentiation capability of human placental multipotent mesenchymal stromal cells (hPMSCs) and identified how endothelial cells recruit hPMSCs participating in vessel formation. hPMSCs from term placentas were induced to differentiate into smooth muscle cells under induction conditions and different matrix substrates. We assessed endothelial cells from umbilical veins for platelet-derived growth factor (PDGF)-BB expression and to induce hPMSC PDGFR-beta and STAT3 activation. Endothelial cells were co-cultured with hPMSCs for in vitro angiogenesis. Cell differentiation ability was then further assessed by mouse placenta transplantation assay. hPMSCs can differentiate into smooth muscle cells; collagen type I and IV or laminin support this differentiation. Endothelial cells expressed significant levels of PDGF-BB and activated STAT3 transcriptional activity in hPMSCs. Endothelial cell-conditioned medium induced hPMSC migration, which was inhibited by STAT3 small interfering RNA transfection or by pretreatement with PDGFR-beta-blocking antibody but not by PDGFR-alpha-blocking antibody or isotype immunoglobulin G (IgG; P < 0.001). hPMSCs can incorporate into endothelial cells with tube formation and promote endothelial cells, forming capillary-like networks than endothelial cells alone (tube lengths: 12 024.1 ± 960.1 vs. 9404.2 ± 584.7 pixels; P < 0.001). Capillary-like networks were significantly reduced by hPMSCs pretreated with PDGFR-beta-blocking antibody but not by PDGFR-alpha-blocking antibody or isotype IgG (P < 0.001). Transplantation of hPMSCs into mouse placentas revealed incorporation of the hPMSCs into vessel walls, which expressed alpha-smooth muscle actin, calponin, and smooth muscle myosin (heavy chain) in vivo. In conclusion, endothelial cell-hPMSC interactions occur during vessel development of placenta. Placental endothelial cell-derived PDGF-BB recruits hPMSCs involved in vascular development via PDGFR-beta/STAT3 activation.

First Trimester Pregnancy Loss and the Expression of Alternatively Spliced NKp30 Isoforms in Maternal Blood and Placental Tissue

Capsule: We observed that first trimester pregnancy loss is associated with an altered expression profile of the three isoforms of the NK receptor NKp30 expressed by NKs in PBMC and placental tissue. In this study, we aimed to investigate whether first trimester pregnancy loss is associated with differences in expression of NKp30 splice variants (isoforms) in maternal peripheral blood or placental tissue. We conducted a prospective case-control study; a total of 33 women undergoing dilation and curettage due to first trimester pregnancy loss were further subdivided into groups with sporadic or recurrent pregnancy loss. The control group comprises women undergoing elective termination of pregnancy. The qPCR approach was employed to assess the relative expression of NKp30 isoforms as well as the total expression of NKp30 and NKp46 receptors between the selected groups. Results show that in both PBMC and placental tissue, NKp46 and NKp30 expressions were mildly elevated in the pregnancy loss groups compared with the elective group. In particular, NKp46 elevation was significant. Moreover, expression analysis of NKp30 isoforms manifested a different profile between PBMC and the placenta. NKp30-a and NKp30-b isoforms in the placental tissue, but not in PBMC, showed a significant increase in the pregnancy loss groups compared with the elective group. Placental expression of NKp30 activating isoforms-a and -b in the pregnancy loss groups was negatively correlated with PLGF expression. By contrast, placental expression of these isoforms in the elective group was positively correlated with TNFα, IL-10, and VEGF-A expression. The altered expression of NKp30 activating isoforms in placental tissue from patients with pregnancy loss compared to the elective group and the different correlations with cytokine expression point to the involvement of NKp30-mediated function in pregnancy loss.

Androgen receptor and histone lysine demethylases in ovine placenta

Sex steroid hormones regulate developmental programming in many tissues, including programming gene expression during prenatal development. While estradiol is known to regulate placentation, little is known about the role of testosterone and androgen signaling in placental development despite the fact that testosterone rises in maternal circulation during pregnancy and in placenta-induced pregnancy disorders. We investigated the role of testosterone in placental gene expression, and focused on androgen receptor (AR). Prenatal androgenization decreased global DNA methylation in gestational day 90 placentomes, and increased placental expression of AR as well as genes involved in epigenetic regulation, angiogenesis, and growth. As AR complexes with histone lysine demethylases (KDMs) to regulate AR target genes in human cancers, we also investigated if the same mechanism is present in the ovine placenta. AR co-immunoprecipitated with KDM1A and KDM4D in sheep placentomes, and AR-KDM1A complexes were recruited to a half-site for androgen response element (ARE) in the promoter region of VEGFA. Androgenized ewes also had increased cotyledonary VEGFA. Finally, in human first trimester placental samples KDM1A and KDM4D immunolocalized to the syncytiotrophoblast, with nuclear KDM1A and KDM4D immunostaining also present in the villous stroma. In conclusion, placental androgen signaling, possibly through AR-KDM complex recruitment to AREs, regulates placental VEGFA expression. AR and KDMs are also present in first trimester human placenta. Androgens appear to be an important regulator of trophoblast differentiation and placental development, and aberrant androgen signaling may contribute to the development of placental disorders.

Insights into the paracrine effects of uterine natural killer cells

Uterine natural killer (uNK) cells are recruited into the uterus during establishment of the implantation and placentation of the embryo, and are hypothesized to regulate uterine spiral artery remodeling and angiogenesis during the initial stages of pregnancy. Failures in uNK cell activation are linked to diseases associated with pregnancy. However, the manner in which these cells interact with the endometrium remain unknown. Therefore, this study investigated the paracrine effects of uNK cells on the gene expression profile of an endometrial epithelial and stromal cell co‑culture system in vitro, using a microarray analysis. Results from reverse transcription‑quantitative polymerase chain reaction and enzyme‑linked immunosorbent assay experiments showed that soluble factors from uNK cells significantly alter endometrial gene expression. In conclusion, this study suggests that paracrine effects of uNK cells guide uNK cell proliferation, trophoblast migration, endometrial decidualization and angiogenesis, and maintain non‑cytotoxicity of uNK cells.

The maternal brain: an organ with peripartal plasticity

The time of pregnancy, birth, and lactation, is characterized by numerous specific alterations in several systems of the maternal body. Peripartum-associated changes in physiology and behavior, as well as their underlying molecular mechanisms, have been the focus of research since decades, but are still far from being entirely understood. Also, there is growing evidence that pregnancy and lactation are associated with a variety of alterations in neural plasticity, including adult neurogenesis, functional and structural synaptic plasticity, and dendritic remodeling in different brain regions. All of the mentioned changes are not only believed to be a prerequisite for the proper fetal and neonatal development, but moreover to be crucial for the physiological and mental health of the mother. The underlying mechanisms apparently need to be under tight control, since in cases of dysregulation, a certain percentage of women develop disorders like preeclampsia or postpartum mood and anxiety disorders during the course of pregnancy and lactation. This review describes common peripartum adaptations in physiology and behavior. Moreover, it concentrates on different forms of peripartum-associated plasticity including changes in neurogenesis and their possible underlying molecular mechanisms. Finally, consequences of malfunction in those systems are discussed.

Interaction between human placental microvascular endothelial cells and a model of human trophoblasts: effects on growth cycle and angiogenic profile

Abstract Intrauterine growth restriction (IUGR) is a leading cause of perinatal complications, and is commonly associated with reduced placental vasculature. Recent studies demonstrated over-expression of IGF-1 in IUGR animal models maintains placental vasculature. However, the cellular environment of the placental chorionic villous is unknown. The close proximity of trophoblasts and microvascular endothelial cells in vivo alludes to autocrine/paracrine regulation following Ad-HuIGF-1 treatment. We investigated the co-culturing of BeWo Choriocarcinoma and Human Placental Microvascular Endothelial Cells (HPMVECs) on the endothelial angiogenic profile and the effect Ad-HuIGF-1 treatment of one cell has on the other. HPMVECs were isolated from human term placentas and cultured in EGM-2 at 37°C with 5% CO2. BeWo cells were maintained in Ham's F12 nutrient mix with 10% FBS and 1% pen/strep. Co-cultured HPMVECS+BeWo cells were incubated in serum-free control media, Ad-HuIGF-1, or Ad-LacZ at MOI 0 and MOI 100:1 for 48 h. Non-treated cells and mono-cultured cells were compared to co-cultured cells. Angiogenic gene expression and proliferative and apoptotic protein expression were analysed by RT-qPCR and immunocytochemistry, respectively. Statistical analyses was performed using student's t-test with P < 0.05 considered significant. Direct Ad-HuIGF-1 treatment increased HPMVEC proliferation (n = 4) and reduced apoptosis (n = 3). Co-culturing HPMVECs+BeWo cells significantly altered RNA expression of the angiogenic profile compared to mono-cultured HPMVECs (n = 8). Direct Ad-HuIGF-1 treatment significantly increased Ang-1 (n = 4) in BeWo cells. Ad-HuIGF-1 treatment of HPMVECs did not alter the RNA expression of angiogenic factors. Trophoblastic factors may play a key role in placental vascular development and IGF-1 may have an important role in HPMVEC growth.

Development of the hemochorial maternal vascular spaces in the placenta through endothelial and vasculogenic mimicry

The maternal vasculature within the placenta in primates and rodents is unique because it is lined by fetal cells of the trophoblast lineage and not by maternal endothelial cells. In addition to trophoblast cells that invade the uterine spiral arteries that bring blood into the placenta, other trophoblast subtypes sit at different levels of the vascular space. In mice, at least five distinct subtypes of trophoblast cells have been identified which engage maternal endothelial cells on the arterial and venous frontiers of the placenta, but which also form the channel-like spaces within it through a process analogous to formation of blood vessels (vasculogenic mimicry). These cells are all large, post-mitotic trophoblast giant cells. In addition to assuming endothelial cell-like characteristics (endothelial mimicry), they produce dozens of different hormones that are thought to regulate local and systemic maternal adaptations to pregnancy. Recent work has identified distinct molecular pathways in mice that regulate the morphogenesis of trophoblast cells on the arterial and venous sides of the vascular circuit that may be analogous to specification of arterial and venous endothelial cells.

Reversal of gene dysregulation in cultured cytotrophoblasts reveals possible causes of preeclampsia

During human pregnancy, a subset of placental cytotrophoblasts (CTBs) differentiates into cells that aggressively invade the uterus and its vasculature, anchoring the progeny and rerouting maternal blood to the placenta. In preeclampsia (PE), CTB invasion is limited, reducing placental perfusion and/or creating intermittent flow. This syndrome, affecting 4%-8% of pregnancies, entails maternal vascular alterations (e.g., high blood pressure, proteinuria, and edema) and, in some patients, fetal growth restriction. The only cure is removal of the faulty placenta, i.e., delivery. Previously, we showed that defective CTB differentiation contributes to the placental component of PE, but the causes were unknown. Here, we cultured CTBs isolated from PE and control placentas for 48 hours, enabling differentiation and invasion. In various severe forms of PE, transcriptomics revealed common aberrations in CTB gene expression immediately after isolation, including upregulation of SEMA3B, which resolved in culture. The addition of SEMA3B to normal CTBs inhibited invasion and recreated aspects of the PE phenotype. Additionally, SEMA3B downregulated VEGF signaling through the PI3K/AKT and GSK3 pathways, effects that were observed in PE CTBs. We propose that, in severe PE, the in vivo environment dysregulates CTB gene expression; the autocrine actions of the upregulated molecules (including SEMA3B) impair CTB differentiation, invasion and signaling; and patient-specific factors determine the signs.

Angiopoietin-1 and angiopoietin-2 as serum biomarkers for ectopic pregnancy and missed abortion: a case-control study

BACKGROUND

A case-control study to evaluate whether a single serum measurement of angiopoietin-1 (ANG-1) and angiopoietin-2 (ANG-2) at 6-8 weeks gestation can differentiate failed pregnancies, whether ectopic pregnancies (EP) or missed abortions (MA), from healthy intrauterine pregnancies (IUP).

INTERVENTION(S)

Serum and tissue mRNA determination of ANG-1 and ANG-2 levels by ELISA and RTPCR, from 60 (30 EP and 30 MA) patients with failed early pregnancy and 33 IUPs.

RESULTS

ANG-1 and ANG-2 concentrations and their ratio are lower in EP (median, 689 and 302 pg/ml, respectively) and MA cases (median, 810 and 402 pg/ml, respectively) compared to IUP (median, 963 and 1477 pg/ml, respectively) (p<0.05, for all). Unlike ANG-2, serum ANG-1 discriminates an EP from a MA (p=0.011). Trophoblastic ANG-1 mRNA expression levels are lower in EP compared to MA and IUP (p<0.05), while ANG-2 mRNA is higher in EP and MA than in IUP (p<0.05).

CONCLUSIONS

A single measurement of serum ANG-1 and ANG-2 at 6-8 weeks of gestation designate the outcome of a pregnancy, as their levels are significantly decreased in failed than normal pregnancies. Serum ANG-1 showed potential to discriminate MA from EP.

Essential roles of EphB receptors and EphrinB ligands in endothelial cell function and angiogenesis

Eph receptor tyrosine kinases and their Ephrin ligands represent an important signaling system with widespread roles in cell physiology and disease. Receptors and ligands in this family are anchored to the cell surface; thus Eph/Ephrin interactions mainly occur at sites of cell-to-cell contact. EphB4 and EphrinB2 are the Eph/Ephrin molecules that play essential roles in vascular development and postnatal angiogenesis. Analysis of expression patterns and function has linked EphB4/EphrinB2 to endothelial cell growth, survival, migration, assembly, and angiogenesis. Signaling from these molecules is complex, with the potential for being bidirectional, emanating both from the Eph receptors (forward signaling) and from the Ephrin ligands (reverse signaling). In this review, we describe recent advances on the roles of EphB/EphrinB protein family in endothelial cell function and outline potential approaches to inhibit pathological angiogenesis based on this understanding.

Cytomegalovirus impairs cytotrophoblast-induced lymphangiogenesis and vascular remodeling in an in vivo human placentation model

We investigated human cytomegalovirus pathogenesis by comparing infection with the low-passage, endotheliotropic strain VR1814 and the attenuated laboratory strain AD169 in human placental villi as explants in vitro and xenografts transplanted into kidney capsules of SCID mice (ie, mice with severe combined immunodeficiency). In this in vivo human placentation model, human cytotrophoblasts invade the renal parenchyma, remodel resident arteries, and induce a robust lymphangiogenic response. VR1814 replicated in villous and cell column cytotrophoblasts and reduced formation of anchoring villi in vitro. In xenografts, infected cytotrophoblasts had a severely diminished capacity to invade and remodel resident arteries. Infiltrating lymphatic endothelial cells proliferated, aggregated, and failed to form lymphatic vessels. In contrast, AD169 grew poorly in cytotrophoblasts in explants, and anchoring villi formed normally in vitro. Likewise, viral replication was impaired in xenografts, and cytotrophoblasts retained invasive capacity, but some partially remodeled blood vessels incorporated lymphatic endothelial cells and were permeable to blood. The expression of both vascular endothelial growth factor (VEGF)-C and basic fibroblast growth factor increased in VR1814-infected explants, whereas VEGF-A and soluble VEGF receptor-3 increased in those infected with AD169. Our results suggest that viral replication and paracrine factors could undermine vascular remodeling and cytotrophoblast-induced lymphangiogenesis, contributing to bleeding, hypoxia, and edema in pregnancies complicated by congenital human cytomegalovirus infection.

Impaired decidual natural killer cell regulation of vascular remodelling in early human pregnancies with high uterine artery resistance

During human pregnancy, natural killer (NK) cells accumulate in the maternal decidua, but their specific roles remain to be determined. Decidual NK (dNK) cells are present during trophoblast invasion and uterine spiral artery remodelling. These events are crucial for successful placentation and the provision of an adequate blood supply to the developing fetus. Remodelling of spiral arteries is impaired in the dangerous pregnancy complication pre-eclampsia. We studied dNK cells isolated from pregnancies at 9–14 weeks' gestation, screened by uterine artery Doppler ultrasound to determine resistance indices which relate to the extent of spiral artery remodelling. dNK cells were able to promote the invasive behaviour of fetal trophoblast cells, partly through HGF. Cells isolated from pregnancies with higher resistance indices were less able to do this and secreted fewer pro-invasive factors. dNK cells from pregnancies with normal resistance indices could induce apoptotic changes in vascular smooth muscle and endothelial cells in vitro, events of importance in vessel remodelling, partly through Fas signalling. dNK cells isolated from high resistance index pregnancies failed to induce vascular apoptosis and secreted fewer pro-apoptotic factors. We have modelled the cellular interactions at the maternal-fetal interface and provide the first demonstration of a functional role for dNK cells in influencing vascular cells. A potential mechanism contributing to impaired vessel remodelling in pregnancies with a higher uterine artery resistance is presented. These findings may be informative in determining the cellular interactions contributing to the pathology of pregnancy disorders where remodelling is impaired, such as pre-eclampsia.

Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Prematurely elevating estradiol in early baboon pregnancy suppresses uterine artery remodeling and expression of extravillous placental vascular endothelial growth factor and α1β1 and α5β1 integrins

We previously showed that advancing the increase in estradiol levels from the second to the first third of baboon pregnancy suppressed placental extravillous trophoblast (EVT) invasion and remodeling of the uterine spiral arteries. Cell culture studies show that vascular endothelial cell growth factor (VEGF) plays a central role in regulating EVT migration and remodeling of the uterine spiral arteries by increasing the expression/action of certain integrins that control extracellular matrix remodeling. To test the hypothesis that the estradiol-induced reduction in vessel remodeling in baboons is associated with an alteration in VEGF and integrin expression, extravillous placental VEGF and integrin expression was determined on d 60 of gestation (term is 184 d) in baboons in which uterine artery transformation was suppressed by maternal estradiol administration on d 25-59. EVT uterine spiral artery invasion was 5-fold lower (P < 0.01), and VEGF protein expression, quantified by in situ proximity ligation assay, was 50% lower (P < 0.05) in the placenta anchoring villi of estradiol-treated than in untreated baboons. α1β1 and α5β1 mRNA levels in cells isolated by laser capture microdissection from the anchoring villi and cytotrophoblastic shell of estradiol-treated baboons were over 2-fold (P < 0.01) and 40% (P < 0.05) lower, respectively, than in untreated animals. In contrast, placental extravillous αvβ3 mRNA expression was unaltered by estradiol treatment. In summary, extravillous placental expression of VEGF and α1β1 and α5β1 integrins was decreased in a cell- and integrin-specific manner in baboons in which EVT invasion and remodeling of the uterine spiral arteries were suppressed by prematurely elevating estradiol levels in early pregnancy. We propose that estrogen normally controls the extent to which the uterine arteries are transformed by placental EVT in primate pregnancy by regulating expression of VEGF and particular integrin extracellular remodeling molecules that mediate this process.

The vascular endothelial growth factor family in adverse pregnancy outcomes

BACKGROUND

Pre-eclampsia, small-for-gestational-age infants, preterm birth and recurrent miscarriage complicate a significant number of pregnancies. The vascular endothelial growth factor (VEGF) family of angiogenic growth factors is implicated in the pathophysiology of these complications. We aimed to elucidate the role of these angiogenic factors in placentation and to evaluate the predictive value of their protein concentrations and genetic variations in pregnancy complications.

METHODS

We performed a systematic search of PubMed, and retrieved original articles. The search included a combination of terms such as VEGF-A, placental growth factor (PlGF), kinase insert domain receptor, fms-like-tyrosine-kinase receptor 1, soluble fms-like-tyrosine-kinase receptor 1, pre-eclampsia, small-for-gestational-age infants, preterm birth, recurrent miscarriage, placenta, prediction and polymorphisms.

RESULTS

This review summarizes the current knowledge of the roles of the VEGF family in early placentation and of the abnormalities in maternal plasma and placental expression of angiogenic proteins in adverse pregnancy outcomes compared with normal pregnancy. PlGF and sFLT-1 in combination with other clinical and biochemical markers in late first or second trimester appear to predict early-onset pre-eclampsia with a high sensitivity and specificity. However, VEGF family proteins do not have sufficient power to accurately predict late-onset pre-eclampsia, small-for-gestational age pregnancies or preterm birth. Functional polymorphisms in these angiogenic genes are implicated in pregnancy complications, but their contribution appears to be minor.

CONCLUSIONS

Although the VEGF family has important roles in normal and complicated pregnancy, the current predictive value of the VEGF family as biomarkers appears to be limited to early-onset pre-eclampsia.

Epigenetics and microRNAs in preeclampsia

Strong evidence suggests a potential link among epigenetics, microRNAs (miRNAs), and pregnancy complications. Much research still needs to be carried out to determine whether epigenetic factors are predictive in the pathogenesis of preeclampsia (PE), a life-threatening disease during pregnancy. Recently, the importance of maternal epigenetic features, including DNA methylation, histone modifications, epigenetically regulated miRNA, and the effect of imprinted or non-imprinted genes on trophoblast growth, invasion, as well as fetal development and hypertension in pregnancy, has been demonstrated in a series of articles. This article discusses the current evidence of this complicated network of miRNA and epigenetic factors as potential mechanisms that may underlie the theories of disease for PE. Translating these basic epigenetic findings to clinical practice could potentially serve as prognostic biomarkers for diagnosis in its early stages and could help in the development of prophylactic strategies.

Decidual NK cell-derived conditioned medium (dNK-CM) mediates VEGF-C secretion in extravillous cytotrophoblasts

PROBLEM

The regulatory mechanisms involved in VEGF-C secretion by trophoblasts during placentation are poorly understood. We investigated whether or not decidual natural killer cell conditioned medium (dNK-CM) stimulated VEGF-C secretion in the extravillous cytotrophoblast (EVT) cell line HTR8/SVneo.

METHOD OF STUDY

The effects of dNK-CM and recombinant IFN-γ on VEGF-C induction by HTR8/SVneo were studied in the absence or presence of IFN-γ or its receptor blocking antibodies, p38 inhibitor (SB202190), JAK inhibitor (JAK inhibitor-1, JI-1), and on STAT1 knockdown HTR8/SVneo. VEGF-C was quantified by ELISA. FACS was used to investigate the phosphorylations of Tyr701 or Ser727 of STAT1 on stimulated HTR8/SVneo.

RESULTS

dNK-CM facilitated VEGF-C secretion by HTR8/SVneo. IFN-γ and IFN-γR1 or IFN-γR2 blocking antibodies reduced both dNK-CM- and IFN-γ-induced VEGF-C secretion. Phosphorylations on Tyr701 or Ser727 of STAT1 were elevated upon stimulation. Secretion of VEGF-C was reduced by treatment with SB202190, JI-1, or STAT1 knockdown by siRNA.

CONCLUSION

VEGF-C production by trophoblasts is regulated by soluble factors secreted by dNK through p38 and JAK-STAT1 pathways.

Differential expression and regulation of angiopoietin-2 in mouse uterus during preimplantation period

Angiogenesis is crucial to successful implantation and decidualization, however, as an important angiogenic growth factor, the effect of Ang-2 in the process of implantation and decidualization is still unknown. This study is to investigate the differential expression of Ang-2 in mouse uterus during early pregnancy and its regulation by steroid hormones using in situ hybridization and RT-PCR. There is no detectable Ang-2 mRNA signal on days 1-5 of pregnancy by in situ hybridization. On days 6-8, Ang-2 mRNA is mainly expressed in the primary decidua of mesometrial side, and the expression gradually increases. By RT-PCR, a significantly higher level of Ang-2 expression is observed on day 8 of pregnancy, although Ang-2 expression can be found through days 1-8. Similarly, Ang-2 is highly expressed in decidualized cells under artificial decidualization. In the ovariectomized mouse uterus, Ang-2 expression gradually increases after estrogen injection and with peak levels at 12 hr, while progesterone injection can cause a decline in uterine Ang-2 mRNA level, which reaches a nadir at 12 hr. These results suggest that Ang-2 may play a key role in the process of mouse decidualization. Estrogen can induce the expression of Ang-2 while progesterone can inhibit its expression in the ovariectomized mouse uterus.

A role for Notch signaling in trophoblast endovascular invasion and in the pathogenesis of pre-eclampsia

Placental trophoblasts (TBs) invade and remodel uterine vessels with an arterial bias. This process, which involves vascular mimicry, re-routes maternal blood to the placenta, but fails in pre-eclampsia. We investigated Notch family members in both contexts, as they play important roles in arterial differentiation/function. Immunoanalyses of tissue sections showed step-wise modulation of Notch receptors/ligands during human TB invasion. Inhibition of Notch signaling reduced invasion of cultured human TBs and expression of the arterial marker EFNB2. In mouse placentas, Notch activity was highest in endovascular TBs. Conditional deletion of Notch2, the only receptor upregulated during mouse TB invasion, reduced arterial invasion, the size of maternal blood canals by 30-40% and placental perfusion by 23%. By E11.5, there was litter-wide lethality in proportion to the number of mutant offspring. In pre-eclampsia, expression of the Notch ligand JAG1 was absent in perivascular and endovascular TBs. We conclude that Notch signaling is crucial for TB vascular invasion.

Mechanism of maternal vascular remodeling during human pregnancy

Remodeling of maternal spiral arteries by invasion of extravillous trophoblast (EVT) is crucial for an adequate blood supply to the fetus. EVT cells that migrate through the decidual tissue destroy the arterial muscular lining from the outside (interstitial invasion), and those that migrate along the arterial lumen displace the endothelium from the inside (endovascular invasion). Numerous factors including cytokines/growth factors, chemokines, cell adhesion molecules, extracellular matrix-degrading enzymes, and environmental oxygen have been proposed to stimulate or inhibit the differentiation/invasion of EVT. Nevertheless, it is still difficult to depict overall pictures of the mechanism controlling perivascular and endovascular invasion. Potential factors that direct interstitial trophoblast towards maternal spiral artery are relatively high oxygen tension in the spiral artery, maternal platelets, vascular smooth muscle cells, and Eph/ephrin system. On the other hand, very little is understood about endovascular invasion except for the involvement of endothelial apoptosis in this process. Only small numbers of molecules such as polysialylated neural cell adhesion molecules and CCR1 have been suggested as specific markers for the endovascular trophoblast. Therefore, an initial step to approach the mechanisms for endovascular invasion could be more detailed molecular characterization of the endovascular trophoblast.

A whole-genome association study for pig reproductive traits

A whole-genome association study was performed for reproductive traits in commercial sows using the PorcineSNP60 BeadChip and Bayesian statistical methods. The traits included total number born (TNB), number born alive (NBA), number of stillborn (SB), number of mummified foetuses at birth (MUM) and gestation length (GL) in each of the first three parities. We report the associations of informative QTL and the genes within the QTL for each reproductive trait in different parities. These results provide evidence of gene effects having temporal impacts on reproductive traits in different parities. Many QTL identified in this study are new for pig reproductive traits. Around 48% of total genes located in the identified QTL regions were predicted to be involved in placental functions. The genomic regions containing genes important for foetal developmental (e.g. MEF2C) and uterine functions (e.g. PLSCR4) were associated with TNB and NBA in the first two parities. Similarly, QTL in other foetal developmental (e.g. HNRNPD and AHR) and placental (e.g. RELL1 and CD96) genes were associated with SB and MUM in different parities. The QTL with genes related to utero-placental blood flow (e.g. VEGFA) and hematopoiesis (e.g. MAFB) were associated with GL differences among sows in this population. Pathway analyses using genes within QTL identified some modest underlying biological pathways, which are interesting candidates (e.g. the nucleotide metabolism pathway for SB) for pig reproductive traits in different parities. Further validation studies on large populations are warranted to improve our understanding of the complex genetic architecture for pig reproductive traits.

The Impact of Preeclampsia on Gene Expression at the Maternal-Fetal Interface

Preeclampsia (PE) impacts 8 million mother-infant pairs worldwide each year. This human pregnancy-specific disease characterized by hypertension and proteinuria accounts for significant maternal and neonatal morbidity and mortality. The current theory of the pathogenesis of PE as reviewed by Drs. Christopher Redman and Ian Sargent is thought to occur as a 2-stage process with poor placentation in the first half of pregnancy resulting in the maternal response in the second half of pregnancy. Our studies have focused on understanding the placental contribution to this serious disease by examining the gene expression profile of the deciduas basalis or basal plate, the region of the placenta involved in the "poor placentation". In this review we present summaries of our microarray datasets both of normal placentation and those gene expression changes resulting in the context of PE. Additionally, we have taken this opportunity to combine the data sets to provide a more comprehensive view of this region of the placenta. As defects in the basal plate are, in part, at the root of the disease process, we believe that understanding the pathobiology that occurs in this region will increase our ability to alter the development and/or course of PE.

Decidualisation and angiogenesis

The timing of decidualisation and vascular processes during the implantation period is of paramount importance for the development of a receptive endometrium suitable for implantation. The endometrium transforms during the secretory phase into a well-vascularised receptive tissue characterised by increased vascular permeability, oedema, proliferation and differentiation of stromal cells into decidual cells, invasion of leucocytes, vascular remodelling and angiogenesis. Decidualisation continues in the presence of conception and an influx of immune cells, trophoblasts and vascular adaptation will occur. Vascular changes include spiral artery remodelling, angiogenesis and the induction of angiogenic factors. Disturbances in uterine blood supply are associated with first-trimester miscarriages and third-trimester perinatal morbidity and mortality caused by pre-eclampsia and foetal growth restriction. This article assesses decidual vascular changes during human implantation, and evaluates the involvement of angiogenesis in the pathogenesis of miscarriages, pre-eclampsia and intrauterine growth restriction.

Antibody treatment promotes compensation for human cytomegalovirus-induced pathogenesis and a hypoxia-like condition in placentas with congenital infection

Human cytomegalovirus (HCMV) is the major viral cause of birth defects worldwide. Affected infants can have temporary symptoms that resolve soon after birth, such as growth restriction, and permanent disabilities, including neurological impairment. Passive immunization of pregnant women with primary HCMV infection is a promising treatment to prevent congenital disease. To understand the effects of sustained viral replication on the placenta and passive transfer of protective antibodies, we performed immunohistological analysis of placental specimens from women with untreated congenital infection, HCMV-specific hyperimmune globulin treatment, and uninfected controls. In untreated infection, viral replication proteins were found in trophoblasts and endothelial cells of chorionic villi and uterine arteries. Associated damage included extensive fibrinoid deposits, fibrosis, avascular villi, and edema, which could impair placental functions. Vascular endothelial growth factor and its receptor fms-like tyrosine kinase 1 (Flt1) were up-regulated, and amniotic fluid contained elevated levels of soluble Flt1 (sFlt1), an antiangiogenic protein, relative to placental growth factor. With hyperimmune globulin treatment, placentas appeared uninfected, vascular endothelial growth factor and Flt1 expression was reduced, and sFlt1 levels in amniotic fluid were lower. An increase in the number of chorionic villi and blood vessels over that in controls suggested compensatory development for a hypoxia-like condition. Taken together the results indicate that antibody treatment can suppress HCMV replication and prevent placental dysfunction, thus improving fetal outcome.

Human pregnancy specific beta-1-glycoprotein 1 (PSG1) has a potential role in placental vascular morphogenesis

Previous studies suggest that human pregnancy specific beta-1-glycoproteins (PSGs) play immunomodulatory roles during pregnancy; however, other possible functions of PSGs have yet to be explored. We have observed that PSGs induce transforming growth factor beta 1 (TGFB1), which among its other diverse functions inhibits T-cell function and has proangiogenic properties. The present study investigates a potential role for PSG1, the most abundant PSG in maternal serum, as a possible inducer of proangiogenic growth factors known to play an important role in establishment of the vasculature at the maternal-fetal interface. To this end, we measured TGFB1, vascular endothelial growth factors (VEGFs) A and C, and placental growth factor (PGF) protein levels in several cell types after PSG1 treatment. In addition, tube formation and wound healing assays were performed to investigate a possible direct interaction between PSG1 and endothelial cells. PSG1 induced up-regulation of both TGFB1 and VEGFA in human monocytes, macrophages, and two human extravillous trophoblast cell lines. We did not observe induction of VEGFC or PGF by PSG1 in any of the cells tested. PSG1 treatment resulted in endothelial tube formation in the presence and absence of VEGFA. Site-directed mutagenesis was performed to map the essential regions within the N-domain of PSG1 required for functional activity. We found that the aspartic acid at position 95, previously believed to be required for binding of PSGs to cells, is not required for PSG1 activity but that the amino acids implicated in the formation of a salt bridge within the N-domain are essential for PSG1 function.

Dysregulation of angiopoietins is associated with placental malaria and low birth weight

Background

Placental malaria (PM) is associated with adverse pregnancy outcomes including low birth weight (LBW). However, the precise mechanisms by which PM induces LBW are poorly defined. Based on the essential role of angiopoietin (ANG)-1 and -2 in normal placental vascular development, we hypothesized that PM may result in the dysregulation of angiopoietins and thereby contribute to LBW outcomes.

Methods and Findings

In a mouse model of PM, we show that Plasmodium berghei ANKA infection of pregnant mice resulted in dysregulated angiopoietin levels and fetal growth restriction. PM lead to decreased ANG-1, increased ANG-2, and an elevated ratio of ANG-2/ANG-1 in the placenta and the serum. These observations were extended to malaria-exposed pregnant women: In a study of primigravid women prospectively followed over the course of pregnancy, Plasmodium falciparum infection was associated with a decrease in maternal plasma ANG-1 levels (P = 0.031) and an increase in the ANG-2:ANG-1 ratio (P = 0.048). ANG-1 levels recovered with successful treatment of peripheral parasitemia (P = 0.010). In a cross-sectional study of primigravidae at delivery, angiopoietin dysregulation was associated with PM (P = 0.002) and LBW (P = 0.041). Women with PM who delivered LBW infants had increased ANG-2:ANG-1 ratios (P = 0.002) compared to uninfected women delivering normal birth weight infants.

Conclusions

These data support the hypothesis that dysregulation of angiopoietins is associated with PM and LBW outcomes, and suggest that ANG-1 and ANG-2 levels may be clinically informative biomarkers to identify P. falciparum-infected mothers at risk of LBW deliveries.