Human fetal placental endothelial cells have a mature arterial and a juvenile venous phenotype with adipogenic and osteogenic differentiation potential

Liver X receptor activation mitigates oxysterol-induced dysfunction in fetoplacental endothelial cells

Maintaining the homeostasis of the placental vasculature is of paramount importance for ensuring normal fetal growth and development. Any disruption in this balance can lead to perinatal morbidity. Several studies have uncovered an association between high levels of oxidized cholesterol (oxysterols), and complications during pregnancy, including gestational diabetes mellitus (GDM) and preeclampsia (PE). These complications often coincide with disturbances in placental vascular function. Here, we investigate the role of two oxysterols (7-ketocholesterol, 7β-hydroxycholesterol) in (dys)function of primary fetoplacental endothelial cells (fpEC). Our findings reveal that oxysterols exert a disruptive influence on fpEC function by elevating the production of reactive oxygen species (ROS) and interfering with mitochondrial transmembrane potential, leading to its depolarization. Moreover, oxysterol-treated fpEC exhibited alterations in intracellular calcium (Ca2+) levels, resulting in the reorganization of cell junctions and a corresponding increase in membrane stiffness and vascular permeability. Additionally, we observed an enhanced adhesion of THP-1 monocytes to fpEC following oxysterol treatment. We explored the influence of activating the Liver X Receptor (LXR) with the synthetic agonist T0901317 (TO) on oxysterol-induced endothelial dysfunction in fpEC. Our results demonstrate that LXR activation effectively reversed oxysterol-induced ROS generation, monocyte adhesion, and cell junction permeability in fpEC. Although the effects on mitochondrial depolarization and calcium mobilization did not reach statistical significance, a strong trend towards stabilization of calcium mobilization was evident in LXR-activated cells. Taken together, our results suggest that high levels of systemic oxysterols link to placental vascular dysfunction and LXR agonists may alleviate their impact on fetoplacental vasculature.

Fat infiltration in skeletal muscle: Influential triggers and regulatory mechanism

Fat infiltration in skeletal muscle (also known as myosteatosis) is now recognized as a distinct disease from sarcopenia and is directly related to declining muscle capacity. Hence, understanding the origins and regulatory mechanisms of fat infiltration is vital for maintaining skeletal muscle development and improving human health. In this article, we summarized the triggering factors such as aging, metabolic diseases and metabolic syndromes, nonmetabolic diseases, and muscle injury that all induce fat infiltration in skeletal muscle. We discussed recent advances on the cellular origins of fat infiltration and found several cell types including myogenic cells and non-myogenic cells that contribute to myosteatosis. Furthermore, we reviewed the molecular regulatory mechanism, detection methods, and intervention strategies of fat infiltration in skeletal muscle. Based on the current findings, our review will provide new insight into regulating function and lipid metabolism of skeletal muscle and treating muscle-related diseases.

MicroRNA-29 differentially mediates preeclampsia-dysregulated cellular responses to cytokines in female and male fetal endothelial cells

Preeclampsia (PE) differentially impairs female and male fetal endothelial cell function, which is associated with an increased risk of adult-onset cardiovascular disorders in children born to mothers with PE. However, the underlying mechanisms are poorly defined. We hypothesize that dysregulation of microRNA-29a-3p and 29c-3p (miR-29a/c-3p) in PE disturbs gene expression and cellular responses to cytokines in fetal endothelial cells in a fetal sex-dependent manner. RT-qPCR analysis of miR-29a/c-3p was performed on female and male unpassaged (P0) human umbilical vein endothelial cells (HUVECs) from normotensive (NT) pregnancies and PE. Bioinformatic analysis of an RNA-seq dataset was performed to identify PE-dysregulated miR-29a/c-3p target genes in female and male P0-HUVECs. Gain- and loss-of-function assays were conducted to determine the effects of miR-29a/c-3p on endothelial monolayer integrity and proliferation in response to transforming growth factor-β1 (TGFβ1) and tumour necrosis factor-α (TNFα) in NT and PE HUVECs at passage 1. We observed that PE downregulated miR-29a/c-3p in male and female P0-HUVECs. PE dysregulated significantly more miR-29a/c-3p target genes in female vs. male P0-HUVECs. Many of these PE-differentially dysregulated miR-29a/c-3p target genes are associated with critical cardiovascular diseases and endothelial function. We further demonstrated that miR-29a/c-3p knockdown specifically recovered the PE-abolished TGFβ1-induced strengthening of endothelial monolayer integrity in female HUVECs, while miR-29a/c-3p overexpression specifically enhanced the TNFα-promoted cell proliferation in male PE HUVECs. In conclusion, PE downregulates miR-29a/c-3p expression and differentially dysregulates miR-29a/c-3p target genes associated with cardiovascular diseases and endothelial function in female and male fetal endothelial cells, possibly contributing to the fetal sex-specific endothelial dysfunction observed in PE. KEY POINTS: Preeclampsia differentially impairs female and male fetal endothelial cell function in responses to cytokines. Pro-inflammatory cytokines are elevated in maternal circulation during pregnancy in preeclampsia. MicroRNAs are critical regulators of endothelial cell function during pregnancy. We have previously reported that preeclampsia downregulated microRNA-29a-3p and 29c-3p (miR-29a/c-3p) in primary fetal endothelial cells. However, it is unknown if PE differentially dysregulates the expression of miR-29a/c-3p in female and male fetal endothelial cells. We show that preeclampsia downregulates miR-29a/c-3p in male and female HUVECs and preeclampsia dysregulates cardiovascular disease- and endothelial function-associated miR-29a/c-3p target genes in HUVECs in a fetal sex-specific manner. MiR-29a/c-3p differentially mediate cell responses to cytokines in female and male fetal endothelial cells from preeclampsia. We have revealed fetal sex-specific dysregulation of miR-29a/c-3p target genes in fetal endothelial cells from preeclampsia. This differential dysregulation may contribute to fetal sex-specific endothelial dysfunction in offspring born to preeclamptic mothers.

The Impact of Hydroxychloroquine on Primary Feto-Placental Endothelial Cells from Healthy and Early-Onset Preeclamptic Placentas

Hydroxychloroquine (HCQ), an anti-malarial drug, is suggested as a promising candidate for the treatment of pregnancy-related disorders associated with endothelial activation, among which there is preeclampsia (PE). Arterial feto-placental endothelial cells (fpECAs) were isolated from control (CTR) and early-onset preeclamptic (EO-PE) placentas. The aim of this study was to test potential protective effects of HCQ in an in vitro model of endothelial activation as well as in cells isolated from EO-PE placentas. To mimic PE conditions, CTR fpECAs were exposed to a pro-inflammatory environment consisting of tumor necrosis factor α (TNF-α), interleukin (IL)-6 and IL-1β (furtherly referred as MIX) with or without varying concentrations of HCQ (1 µg/mL and 10 µg/mL). Their effect on wound healing and endothelial barrier integrity was analyzed. Variations in the expression of IL-8 and leukocyte adhesion molecules (LAM) on both mRNA and protein levels were determined between CTR and PE fpECAs in the presence or absence of HCQ. MIX decreased wound healing and stability of the endothelial barrier, but HCQ did not affect it. Significant differences between CTR and EO-PE fpECAs were observed in IL-8 mRNA, protein secretion, and vascular cell adhesion protein 1 (VCAM-1) mRNA expression levels. After challenging CTR fpECAs with MIX, upregulation of both mRNA and protein levels was observed in all molecules. Combined treatment of HCQ and MIX slightly lowered VCAM-1 total protein amount. In CTR fpECAs, treatment with low concentrations of HCQ alone (1 µg/mL) reduced basal levels of IL-8 and VCAM-1 mRNA and secretion of IL-8, while in EO-PE fpECAs, a higher (10µg/mL) HCQ concentration slightly reduced the gene expression of IL-8. Conclusion: These results provide additional support for the safety of HCQ, as it did not adversely affect endothelial functionality in control fpECAs at the tested concentration. Furthermore, the observed limited effects on IL-8 secretion in EO-PE fpECAs warrant further investigation, highlighting the need for clinical trials to assess the potential therapeutic effects of HCQ in preeclampsia. Conducting clinical trials would offer a more comprehensive understanding of HCQ's efficacy and safety, allowing us to explore its potential benefits and limitations in a real-world clinical setting.

Single-nucleus and bulk RNA sequencing reveal cellular and transcriptional mechanisms underlying lipid dynamics in high marbled pork

Pork is the most consumed meat in the world, and its quality is associated with human health. Intramuscular fat (IMF) deposition (also called marbling) is a key factor positively correlated with various quality traits and lipo-nutritional values of meat. However, the cell dynamics and transcriptional programs underlying lipid deposition in highly marbled meat are still unclear. Here, we used Laiwu pigs with high (HLW) or low (LLW) IMF contents to explore the cellular and transcriptional mechanisms underlying lipid deposition in highly-marbled pork by single-nucleus RNA sequencing (snRNA-seq) and bulk RNA sequencing. The HLW group had higher IMF contents but less drip loss than the LLW group. Lipidomics results revelled the changes of overall lipid classes composition (e.g., glycerolipids including triglycerides, diglycerides, and monoglycerides; sphingolipids including ceramides and monohexose ceramide significantly increased) between HLW and LLW groups. SnRNA-seq revealed nine distinct cell clusters, and the HLW group had a higher percentage of adipocytes (1.40% vs. 0.17%) than the LLW group. We identified 3 subpopulations of adipocytes, including PDE4D⁺/PDE7B⁺ (in HLW and LLW), DGAT2⁺/SCD⁺ (mostly in HLW) and FABP5⁺/SIAH1⁺ cells (mostly in HLW). Moreover, we showed that fibro/adipogenic progenitors could differentiate into IMF cells and contribute to 43.35% of adipocytes in mice. In addition, RNA-seq revealed different genes involved in lipid metabolism and fatty acid elongation. Our study provides new insights into the cellular and molecular signatures of marbling formation; such knowledge may facilitate the development of new strategies to increase IMF deposition and the lipo-nutritional quality of high marbled pork.

CD39 abrogates platelet-derived factors induced IL-1β expression in the human placenta

Tissue insults in response to inflammation, hypoxia and ischemia are accompanied by the release of ATP into the extracellular space. There, ATP modulates several pathological processes, including chemotaxis, inflammasome induction and platelet activation. ATP hydrolysis is significantly enhanced in human pregnancy, suggesting that increased conversion of extracellular ATP is an important anti-inflammatory process in preventing exaggerated inflammation, platelet activation and hemostasis in gestation. Extracellular ATP is converted into AMP, and subsequently into adenosine by the two major nucleotide-metabolizing enzymes CD39 and CD73. Here, we aimed to elucidate developmental changes of placental CD39 and CD73 over gestation, compared their expression in placental tissue from patients with preeclampsia and healthy controls, and analyzed their regulation in response to platelet-derived factors and different oxygen conditions in placental explants as well as the trophoblast cell line BeWo. Linear regression analysis showed a significant increase in placental CD39 expression, while at the same time CD73 levels declined at term of pregnancy. Neither maternal smoking during first trimester, fetal sex, maternal age, nor maternal BMI revealed any effects on placental CD39 and CD73 expression. Immunohistochemistry detected both, CD39 and CD73, predominantly in the syncytiotrophoblast layer. Placental CD39 and CD73 expression were significantly increased in pregnancies complicated with preeclampsia, when compared to controls. Cultivation of placental explants under different oxygen conditions had no effect on the ectonucleotidases, whereas presence of platelet releasate from pregnant women led to deregulated CD39 expression. Overexpression of recombinant human CD39 in BeWo cells decreased extracellular ATP levels after culture in presence of platelet-derived factors. Moreover, platelet-derived factors-induced upregulation of the pro-inflammatory cytokine, interleukin-1β, was abolished by CD39 overexpression. Our study shows that placental CD39 is upregulated in preeclampsia, suggesting an increasing demand for extracellular ATP hydrolysis at the utero-placental interface. Increased placental CD39 in response to platelet-derived factors may lead to enhanced conversion of extracellular ATP levels, which in turn could represent an important anti-coagulant defense mechanism of the placenta.

Liver X Receptor Activation Attenuates Oxysterol-Induced Inflammatory Responses in Fetoplacental Endothelial Cells

Oxysterols are oxidized cholesterol derivatives whose systemic levels are found elevated in pregnancy disorders such as gestational diabetes mellitus (GDM). Oxysterols act through various cellular receptors and serve as a key metabolic signal, coordinating inflammation. GDM is a condition of low-grade chronic inflammation accompanied by altered inflammatory profiles in the mother, placenta and fetus. Higher levels of two oxysterols, namely 7-ketocholesterol (7-ketoC) and 7β-hydroxycholesterol (7β-OHC), were observed in fetoplacental endothelial cells (fpEC) and cord blood of GDM offspring. In this study, we tested the effects of 7-ketoC and 7β-OHC on inflammation and investigated the underlying mechanisms involved. Primary fpEC in culture treated with 7-ketoC or 7β-OHC, induced the activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NFκB) signaling, which resulted in the expression of pro-inflammatory cytokines (IL-6, IL-8) and intercellular cell adhesion molecule-1 (ICAM-1). Liver-X receptor (LXR) activation is known to repress inflammation. Treatment with LXR synthetic agonist T0901317 dampened oxysterol-induced inflammatory responses. Probucol, an inhibitor of LXR target gene ATP-binding cassette transporter A-1 (ABCA-1), antagonized the protective effects of T0901317, suggesting a potential involvement of ABCA-1 in LXR-mediated repression of inflammatory signaling in fpEC. TLR-4 inhibitor Tak-242 attenuated pro-inflammatory signaling induced by oxysterols downstream of the TLR-4 inflammatory signaling cascade. Taken together, our findings suggest that 7-ketoC and 7β-OHC contribute to placental inflammation through the activation of TLR-4. Pharmacologic activation of LXR in fpEC decelerates its shift to a pro-inflammatory phenotype in the presence of oxysterols.

MicroRNA-29 Differentially Mediates Preeclampsia-Dysregulated Cellular Responses to Cytokines in Female and Male Fetal Endothelial Cells

Introduction

Preeclampsia (PE) differentially impairs female and male fetal endothelial cell function which is associated with the increased risks of adult-onset cardiovascular disorders in children born to mothers with PE. However, the underlying mechanisms are poorly defined. We hypothesize that dysregulation of microRNA-29a-3p and 29c-3p (miR-29a/c-3p) in PE disturbs gene expression and cellular responses to cytokines in fetal endothelial cells in a fetal sex-dependent manner.

Methods

RT-qPCR analysis of miR-29a/c-3p was performed on female and male unpassaged (P0) human umbilical vein endothelial cells (HUVECs) from normotensive (NT) and PE pregnancies. Bioinformatic analysis of an RNAseq dataset was performed to identify PE-dysregulated miR-29a/c-3p target genes in female and male P0-HUVECs. Gain- and loss-of-function assays were conducted to determine the effects of miR-29a/c-3p on endothelial monolayer integrity and proliferation in response to TGFβ1 and TNFα in NT and PE HUVECs at passage 1.

Results

PE downregulated miR-29a/c-3p in male, but not female P0-HUVECs. PE dysregulated significantly more miR-29a/c-3p target genes in female vs. male P0-HUVECs. Many of these PE-differentially dysregulated miR-29a/c-3p target genes are associated with critical cardiovascular diseases and endothelial functions. We further demonstrated that miR-29a/c-3p knockdown specifically recovered the PE-abolished TGFβ1-induced strengthening of endothelial monolayer integrity in female HUVECs, while miR-29a/c-3p overexpression specifically enhanced the TNFα-promoted cell proliferation in male PE HUVECs.

Conclusions

PE differentially dysregulates miR-29a/c-3p and their target genes associated with cardiovascular diseases- and endothelial function in female and male fetal endothelial cells, possibly contributing to the fetal sex-specific endothelial dysfunction observed in PE.

mPRα and PR co-operate in progesterone inhibition of endothelial cell focal adhesion

Progesterone causes vascular smooth muscle cell relaxation through membrane progesterone receptors (mPRs), which are members of the progestin and adipoQ receptor (PAQR) family, and nuclear PRs (nPRs). However, beneficial vascular effects of progesterone in preventing pre-atherosclerosis and the involvement of mPRs and nPRs remain unclear. The results show short- to long-term treatments with 100 nM progesterone (P4) and specific agonists for mPRs, OD 02-0, and nPRs, R5020, inhibited pre-atherosclerotic events in human umbilical vein endothelial cells (HUVECs), decreasing focal adhesion (FA) by monocytes, FA signaling, HUVEC migration and invasion, and vinculin expression. Progesterone and OD 02-0, but not R5020, inhibited phosphorylation of Src and focal adhesion kinase, critical kinases of FA signaling, within 20 min and migration and invasion of HUVECs and monocyte adhesion after 3 h. These inhibitory P4 and 02-0 effects were attenuated with MAP kinase and Pi3k inhibitors, indicating involvement of these kinases in this mPR-mediated action. However, after 16 h, OD 02-0 was no longer effective in inhibiting FA signaling, while both progesterone and R5020 decreased the activity of the two kinases. Knockdown of receptor expression with siRNA confirmed that mPRα mediates short-term and nPR long-term inhibitory effects of progesterone on FA signaling. Thus, progesterone inhibition of FA signaling and pre-atherosclerosis is coordinated through mPRα and nPRs.

Placental ion channels: potential target of chemical exposure

The placenta is an important organ for the exchange of substances between the fetus and the mother, hormone secretion, and fetoplacental immunological defense. Placenta has an organ-specific distribution of ion channels and trophoblasts, and placental vessels express a large number of ion channels. Several placental housekeeping activities and pregnancy complications are at least partly controlled by ion channels, which are playing an important role in regulating hormone secretion, trophoblastic homeostasis, ion transport, and vasomotor activity. The function of several placental ion channels (Na, Ca, and Cl ion channels, cation channel, nicotinic acetylcholine receptors, and aquaporin-1) is known to be influenced by chemical exposure, i.e., their responses to different chemicals have been tested and confirmed in experimental models. Here, we review the possibility that placental ion channels are targets of toxicological concern in terms of placental function, fetal growth, and development.

The Distinct Role of the HDL Receptor SR-BI in Cholesterol Homeostasis of Human Placental Arterial and Venous Endothelial Cells

As opposed to adults, high-density lipoprotein (HDL) is the main cholesterol carrying lipoprotein in fetal circulation. The major HDL receptor, scavenger receptor class B type I (SR-BI), contributes to local cholesterol homeostasis. Arterial endothelial cells (ECA) from human placenta are enriched with cholesterol compared to venous endothelial cells (ECV). Moreover, umbilical venous and arterial plasma cholesterol levels differ markedly. We tested the hypothesis that the uptake of HDL-cholesteryl esters differs between ECA and ECV because of the differential expression of SR-BI. We aimed to identify the key regulators underlying these differences and the functional consequences. Immunohistochemistry was used for visualization of SR-BI in situ. ECA and ECV were isolated from the chorionic plate of human placenta and used for RT-qPCR, Western Blot, and HDL uptake assays with ³H- and ¹²⁵I-labeled HDL. DNA was extracted for the methylation profiling of the SR-BI promoter. SR-BI regulation was studied by exposing ECA and ECV to differential oxygen concentrations or shear stress. Our results show elevated SR-BI expression and protein abundance in ECA compared to ECV in situ and in vitro. Immunohistochemistry demonstrated that SR-BI is mainly expressed on the apical side of placental endothelial cells in situ, allowing interaction with mature HDL circulating in the fetal blood. This was functionally linked to a higher increase of selective cholesterol ester uptake from fetal HDL in ECA than in ECV, and resulted in increased cholesterol availability in ECA. SR-BI expression on ECV tended to decrease with shear stress, which, together with heterogeneous immunostaining, suggests that SR-BI expression is locally regulated in the placental vasculature. In addition, hypomethylation of several CpG sites within the SR-BI promoter region might contribute to differential expression of SR-BI between chorionic arteries and veins. Therefore, SR-BI contributes to a local cholesterol homeostasis in ECA and ECV of the human feto-placental vasculature.

Transient Hyperglycemia and Hypoxia Induce Memory Effects in AngiomiR Expression Profiles of Feto-Placental Endothelial Cells

Gestational diabetes (GDM) and preeclampsia (PE) are associated with fetal hyperglycemia, fetal hypoxia, or both. These adverse conditions may compromise fetal and placental endothelial cells. In fact, GDM and PE affect feto-placental endothelial function and also program endothelial function and cardiovascular disease risk of the offspring in the long-term. MicroRNAs are short, non-coding RNAs that regulate protein translation and fine tune biological processes. A group of microRNAs termed angiomiRs is particularly involved in the regulation of endothelial function. We hypothesized that transient hyperglycemia and hypoxia may alter angiomiR expression in feto-placental endothelial cells (fpEC). Thus, we isolated primary fpEC after normal, uncomplicated pregnancy, and induced hyperglycemia (25 mM) and hypoxia (6.5%) for 72 h, followed by reversal to normal conditions for another 72 h. Current vs. transient effects on angiomiR profiles were analyzed by RT-qPCR and subjected to miRNA pathway analyses using DIANA miRPath, MIENTURNET and miRPathDB. Both current and transient hypoxia affected angiomiR profile stronger than current and transient hyperglycemia. Both stimuli altered more angiomiRs transiently, i.e., followed by 72 h culture at control conditions. Pathway analysis revealed that hypoxia significantly altered the pathway ‘Proteoglycans in cancer’. Transient hypoxia specifically affected miRNAs related to ‘adherens junction’. Our data reveal that hyperglycemia and hypoxia induce memory effects on angiomiR expression in fpEC. Such memory effects may contribute to long-term adaption and maladaption to hyperglycemia and hypoxia.

Human Milk Oligosaccharides in Cord Blood Are Altered in Gestational Diabetes and Stimulate Feto-Placental Angiogenesis In Vitro

(1) Background: Human milk oligosaccharides (HMOs) are present in maternal serum during pregnancy and their composition is altered in gestational diabetes (GDM). HMOs are also in fetal cord blood and in contact with the feto-placental endothelium, potentially affecting its functions, such as angiogenesis. We hypothesized that cord blood HMOs are changed in GDM and contribute to increased feto-placental angiogenesis, hallmark of GDM. (2) Methods: Using HPLC, we quantified HMOs in cord blood of women with normal glucose tolerance (NGT, n = 25) or GDM (n = 26). We investigated in vitro angiogenesis using primary feto-placental endothelial cells (fpECs) from term placentas after healthy pregnancy (n = 10), in presence or absence of HMOs (100 µg/mL) isolated from human milk, 3′-sialyllactose (3′SL, 30 µg/mL) and lactose (glycan control) and determined network formation (Matrigel assay), proliferation (MTT assays), actin organization (F-actin staining), tube formation (fibrin tube formation assay) and sprouting (spheroid sprouting assay). (3) Results: 3′SL was higher in GDM cord blood. HMOs increased network formation, HMOs and 3’SL increased proliferation and F-actin staining. In fibrin assays, HMOs and 3’SL increased total tube length by 24% and 25% (p < 0.05), in spheroid assays, by 32% (p < 0.05) and 21% (p = 0.056), respectively. Lactose had no effect. (4) Conclusions: Our study suggests a novel role of HMOs in feto-placental angiogenesis and indicates a contribution of HMO composition to altered feto-placental vascularization in GDM.

SUCNR1 Is Expressed in Human Placenta and Mediates Angiogenesis: Significance in Gestational Diabetes

Placental hypervascularization has been reported in pregnancy-related pathologies such as gestational diabetes mellitus (GDM). Nevertheless, the underlying causes behind this abnormality are not well understood. In this study, we addressed the expression of SUCNR1 (cognate succinate receptor) in human placental endothelial cells and hypothesized that the succinate-SUCNR1 axis might play a role in the placental hypervascularization reported in GDM. We measured significantly higher succinate levels in placental tissue lysates from women with GDM relative to matched controls. In parallel, SUCNR1 protein expression was upregulated in GDM tissue lysates as well as in isolated diabetic fetoplacental arterial endothelial cells (FpECAds). A positive correlation of SUCNR1 and vascular endothelial growth factor (VEGF) protein levels in tissue lysates indicated a potential link between the succinate-SUCNR1 axis and placental angiogenesis. In our in vitro experiments, succinate prompted hallmarks of angiogenesis in human umbilical vein endothelial cells (HUVECs) such as proliferation, migration and spheroid sprouting. These results were further validated in fetoplacental arterial endothelial cells (FpECAs), where succinate induced endothelial tube formation. VEGF gene expression was increased in response to succinate in both HUVECs and FpECAs. Yet, knockdown of SUCNR1 in HUVECs led to suppression of VEGF gene expression and abrogated the migratory ability and wound healing in response to succinate. In conclusion, our data underline SUCNR1 as a promising metabolic target in human placenta and as a potential driver of enhanced placental angiogenesis in GDM.

Differential Serotonin Uptake Mechanisms at the Human Maternal-Fetal Interface

Serotonin (5-HT) plays an extensive role during pregnancy in regulating both the placental physiology and embryonic/fetal development. The uptake of 5-HT into cells is central to the control of local concentrations of 5-HT near its molecular targets. Here, we investigated the mechanisms of 5-HT uptake into human primary placental cells and cord blood platelets, all isolated immediately after birth. Trophoblasts and cord blood platelets showed 5-HT uptake with similar Michaelis constant (Km) values (~0.6 μM), typical of the high-affinity serotonin transporter (SERT). The uptake of 5-HT into trophoblasts was efficiently inhibited by various SERT-targeting drugs. In contrast, the uptake of 5-HT into feto-placental endothelial cells was not inhibited by a SERT blocker and showed a Km value (~782 μM) in the low-affinity range. Consistent with this, SERT mRNAs were abundant in term trophoblasts but sparse in feto-placental endothelial cells, whereas the opposite was found for the low-affinity plasma membrane monoamine transporter (PMAT) mRNAs. Organic cation transporter (OCT) 1, 2, and 3 mRNAs were absent or sparse in both cell types. In summary, the results demonstrate, for the first time, the presence of functional 5-HT uptake systems in feto-placental endothelial cells and fetal platelets, cells that are in direct contact with fetal blood plasma. The data also highlight the sensitivity to various psychotropic drugs of 5-HT transport into trophoblasts facing the maternal blood. The multiple, high-, and low-affinity systems present for the cellular uptake of 5-HT underscore the importance of 5-HT homeostasis at the maternal-fetal interface.

Flow-through isolation of human first trimester umbilical cord endothelial cells

Human umbilical vein and artery endothelial cells (HUVEC; HUAEC), placental endothelial cells (fpAEC), and endothelial colony-forming cells (ECFC) from cord blood are a widely used model for researching placental vascular development, fetal and placental endothelial function, and the effect of adverse conditions in pregnancy thereon. However, placental vascular development and angiogenesis start in the first weeks of gestation, and adverse conditions in pregnancy may also affect endothelial function before term, suggesting that endothelial cells from early pregnancy may respond differently. Thus, we established a novel, gentle flow-through method to isolate pure human umbilical endothelial cells from first trimester (FTUEC). FTUEC were characterized and their phenotype was compared to the umbilical endothelium in situ as well as to other fetal endothelial cell models from term of gestation, i.e. HUVEC, fpAEC, ECFC. FTUEC possess a CD34-positive, juvenile endothelial phenotype, and can be expanded and passaged. We regard FTUEC as a valuable tool to study developmental processes as well as the effect of adverse insults in pregnancy in vitro.

Perinatal Derivatives: Where Do We Stand? A Roadmap of the Human Placenta and Consensus for Tissue and Cell Nomenclature

Progress in the understanding of the biology of perinatal tissues has contributed to the breakthrough revelation of the therapeutic effects of perinatal derivatives (PnD), namely birth-associated tissues, cells, and secreted factors. The significant knowledge acquired in the past two decades, along with the increasing interest in perinatal derivatives, fuels an urgent need for the precise identification of PnD and the establishment of updated consensus criteria policies for their characterization. The aim of this review is not to go into detail on preclinical or clinical trials, but rather we address specific issues that are relevant for the definition/characterization of perinatal cells, starting from an understanding of the development of the human placenta, its structure, and the different cell populations that can be isolated from the different perinatal tissues. We describe where the cells are located within the placenta and their cell morphology and phenotype. We also propose nomenclature for the cell populations and derivatives discussed herein. This review is a joint effort from the COST SPRINT Action (CA17116), which broadly aims at approaching consensus for different aspects of PnD research, such as providing inputs for future standards for the processing and in vitro characterization and clinical application of PnD.

Microphysiological systems of the placental barrier

Methods to evaluate maternal-fetal transport across the placental barrier have generally involved clinical observations after-the-fact, ex vivo perfused placenta studies, or in vitro Transwell assays. Given the ethical and technical limitations in these approaches, and the drive to understand fetal development through the lens of transport-induced injury, such as with the examples of thalidomide and Zika Virus, efforts to develop novel approaches to study these phenomena have expanded in recent years. Notably, within the past 10 years, placental barrier models have been developed using hydrogel, bioreactor, organ-on-a-chip, and bioprinting approaches. In this review, we discuss the biology of the placental barrier and endeavors to recapitulate this barrier in vitro using these approaches. We also provide analysis of current limitations to drug discovery in this context, and end with a future outlook.

The unique applicability of the human placenta to the Adverse Outcome Pathway (AOP) concept: the placenta provides fundamental insights into human organ functions at multiple levels of biological organization

Despite the short lifespan of the human placenta, the proper formation and function of the organ is of crucial importance for fetal development. Placental dysfunction increases the risk of complications for mother and child during pregnancy and childbirth and beyond as it predisposes to fetal programming. The placenta is an upstream organ of the fetus. It performs the functions of fetal lungs, liver, intestines, kidneys and glands as long as these organs are not fully functional. Furthermore, it is the only human organ that is non-invasively available either after elective abortion or after birth. This is a crucial point given that the conceptual framework of Adverse Outcome Pathway (AOP) requires data on organ function. In vitro and ex vivo placental studies, combined with epidemiological and clinical data on pregnant women, newborns, and infants can uniquely cover all levels of information needed to develop new AOPs and complement existing AOPs related to reproductive toxicity and beyond. To stimulate further research in this area and to support researchers in future studies dealing with the development of AOPs related to the placenta, this review first gives a brief description of placental structure, placental development and relevant pregnancy diseases. The state of knowledge about the available placental models, their particularities and limitations are briefly discussed. Finally, the use of placental research for the development of AOPs is presented with an illustrative example.

Sexual dimorphism of miRNA signatures in feto-placental endothelial cells is associated with altered barrier function and actin organization

Endothelial function and the risk for endothelial dysfunction differ between males and females. Besides the action of estrogen, sex chromosome gene expression and programming effects also provoke this sexual dimorphism. MicroRNAs (miRNAs) have emerged as regulators of endothelial cell function and dysfunction. We here hypothesized distinct miRNA expression patterns in male versus female human endothelial cells that contribute to the functional differences. We used our well-established model of fetal endothelial cells isolated from placenta (fpEC) and analyzed sexual dimorphic miRNA expression and potentially affected biological functions. Next-generation miRNA sequencing of fpEC isolated after pregnancies with male and female neonates identified sex-dependent miRNA expression patterns. Potential biological pathways regulated by the altered set of miRNAs were determined using mirPath and mirSystem softwares, and suggested differences in barrier function and actin organization. The identified pathways were further investigated by monolayer impedance measurements (ECIS) and analysis of F-actin organization (Phalloidin). Nine miRNAs were differentially expressed in fpEC of male versus female neonates. Functional pathways most significantly regulated by these miRNAs included 'Adherens junction', 'ECM receptor interaction' and 'Focal adhesion'. These pathways control monolayer barrier function and may be paralleled by altered cytoskeletal organization. In fact, monolayer impedance was higher in fpEC of male progeny, and F-actin staining revealed more pronounced peripheral stress fibers in male versus female fpEC. Our data highlight that endothelial cell function differs between males and females already in utero, and that altered miRNAs are associated with sex dependent differences in barrier function and actin organization.

Interplay of drug transporters P-glycoprotein (MDR1), MRP1, OATP1A2 and OATP1B3 in passage of maraviroc across human placenta

Special attention is required when pharmacological treatment is indicated for a pregnant woman. P-glycoprotein (MDR1) is a well-known transporter localized in the maternal blood-facing apical membrane of placental syncytiotrophoblast and is considered to play an important role in protecting the developing fetus. Maraviroc, a MDR1 substrate that is registered for treatment of HIV infection, shows a low toxicity profile, suggesting favorable tolerability also if administered to pregnant women. Nevertheless, there is only poor understanding to date regarding the extent to which it permeates across the placental barrier and what are the transport mechanisms involved. Endeavoring to clarify the passage of maraviroc across placenta, we used in this study the method of closed-circuit perfusion of maraviroc across human placental cotyledon. The data obtained confirmed slight involvement of MDR1, but they also suggest possible interaction with other transport system(s) working in the opposite direction from that of MDR1. Complementary in vitro studies, including cellular experiments on choriocarcinoma BeWo cells as well as transporter-overexpressing MDCKII and A431 cell lines and accumulation in placental fresh villous fragments, revealed maraviroc transport by MRP1, OATP1A2, and OATP1B3 transporters. Based on mRNA expression data in the placental tissue, isolated trophoblasts, and fetal endothelial cells, especially MRP1 and OATP1A2 seem to play a crucial role in cooperatively driving maraviroc into placental tissue. By the example of maraviroc, we show here the important interplay of transporters in placental drug handling and its possibility to overcome the MDR1-mediated efflux.

Role of ROS/RNS in Preeclampsia: Are Connexins the Missing Piece?

Preeclampsia is a pregnancy complication that appears after 20 weeks of gestation and is characterized by hypertension and proteinuria, affecting both mother and offspring. The cellular and molecular mechanisms that cause the development of preeclampsia are poorly understood. An important feature of preeclampsia is an increase in oxygen and nitrogen derived free radicals (reactive oxygen species/reactive nitrogen species (ROS/RNS), which seem to be central players setting the development and progression of preeclampsia. Cell-to-cell communication may be disrupted as well. Connexins (Cxs), a family of transmembrane proteins that form hemichannels and gap junction channels (GJCs), are essential in paracrine and autocrine cell communication, allowing the movement of signaling molecules between cells as well as between the cytoplasm and the extracellular media. GJCs and hemichannels are fundamental for communication between endothelial and smooth muscle cells and, therefore, in the control of vascular contraction and relaxation. In systemic vasculature, the activity of GJCs and hemichannels is modulated by ROS and RNS. Cxs participate in the development of the placenta and are expressed in placental vasculature. However, it is unknown whether Cxs are modulated by ROS/RNS in the placenta, or whether this potential modulation contributes to the pathogenesis of preeclampsia. Our review addresses the possible role of Cxs in preeclampsia, and the plausible modulation of Cxs-formed channels by ROS and RNS. We suggest these factors may contribute to the development of preeclampsia.

Role of oxygen in fetoplacental endothelial responses: hypoxia, physiological normoxia, or hyperoxia?

During pregnancy, placental vascular growth, which is essential for supporting the rapidly growing fetus, is associated with marked elevations in blood flow. These vascular changes take place under chronic physiological low O₂ (less than 2-8% O₂ in human; chronic physiological normoxia, CPN) throughout pregnancy. O₂ level below CPN pertinent to the placenta results in placental hypoxia. Such hypoxia can cause severe endothelial dysfunction, which is associated with adverse pregnancy outcomes (e.g., preeclampsia) and high risk of adult-onset cardiovascular diseases in children born to these pregnancy complications. However, our current knowledge about the mechanisms underlying fetoplacental endothelial function is derived primarily from cell models established under atmospheric O₂ (~21% O₂ at sea level, hyperoxia). Recent evidence has shown that fetoplacental endothelial cells cultured under CPN have distinct gene expression profiles and cellular responses compared with cells cultured under chronic hyperoxia. These data indicate the critical roles of CPN in programming fetal endothelial function and prompt us to re-examine the mechanisms governing fetoplacental endothelial function under CPN. Better understanding these mechanisms will facilitate us to develop preventive and therapeutic strategies for endothelial dysfunction-associated diseases (e.g., preeclampsia). This review will provide a brief summary on the impacts of CPN on endothelial function and its underlying mechanisms with a focus on fetoplacental endothelial cells.

Sphingolipid Signature of Human Feto-Placental Vasculature in Preeclampsia

Bioactive sphingolipids are emerging as key regulators of vascular function and homeostasis. While most of the clinical studies have been devoted to profile circulating sphingolipids in maternal plasma, little is known about the role of the sphingolipid at the feto-placental vasculature, which is in direct contact with the offspring circulation. Our study aims to compare the sphingolipid profile of normal with preeclamptic (PE) placental chorionic arteries and isolated endothelial cells, with the goal of unveiling potential underlying pathomechanisms in the vasculature. Dihydrosphingosine and sphingomyelin (SM) concentrations (C16:0-, C18:0-, and C24:0- sphingomyelin) were significantly increased in chorionic arteries of preeclamptic placentas, whereas total ceramide, although showing a downward trend, were not statistically different. Moreover, RNA and immunofluorescence analysis showed impaired sphingosine-1-phosphate (S1P) synthesis and signaling in PE vessels. Our data reveal that the exposure to a deranged maternal intrauterine environment during PE alters the sphingolipid signature and gene expression on the fetal side of the placental vasculature. This pathological remodeling consists in increased serine palmitoyltransferase (SPT) activity and SM accrual in PE chorionic arteries, with concomitance impairment endothelial S1P signaling in the endothelium of these vessels. The increase of endothelial S1P phosphatase, lyase and S1PR2, and blunted S1PR1 expression support the onset of the pathological phenotype in chorionic arteries.

Maternal Overweight Downregulates MME (Neprilysin) in Feto-Placental Endothelial Cells and in Cord Blood

Maternal overweight in pregnancy alters the metabolic environment and generates chronic low-grade inflammation. This affects fetal development and programs the offspring’s health for developing cardiovascular and metabolic disease later in life. MME (membrane-metalloendopeptidase, neprilysin) cleaves various peptides regulating vascular tone. Endothelial cells express membrane-bound and soluble MME. In adults, the metabolic environment of overweight and obesity upregulates endothelial and circulating MME. We here hypothesized that maternal overweight increases MME in the feto-placental endothelium. We used primary feto-placental endothelial cells (fpEC) isolated from placentas after normal vs. overweight pregnancies and determined MME mRNA, protein, and release. Additionally, soluble cord blood MME was analyzed. The effect of oxygen and tumor necrosis factor α (TNFα) on MME protein in fpEC was investigated in vitro. Maternal overweight reduced MME mRNA (−39.9%, p < 0.05), protein (−42.5%, p = 0.02), and MME release from fpEC (−64.7%, p = 0.02). Both cellular and released MME protein negatively correlated with maternal pre-pregnancy BMI. Similarly, cord blood MME was negatively associated with pre-pregnancy BMI (r = −0.42, p = 0.02). However, hypoxia and TNFα, potential negative regulators of MME expression, did not affect MME protein. Reduction of MME protein in fpEC and in cord blood may alter the balance of vasoactive peptides. Our study highlights the fetal susceptibility to maternal metabolism and inflammatory state.

Neonatal HDL Counteracts Placental Vascular Inflammation via S1P-S1PR1 Axis

Placental inflammation and dysfunction during pregnancy are associated with short- and long-term adverse outcomes for the offspring. However, the mechanisms of vascular protection at the feto-placental interface are still poorly investigated. The high-density lipoprotein (HDL) associated sphingosine-1-phosphate (S1P) has been described as a powerful anti-inflammatory complex. This study aimed to elucidate the role of cord blood-derived HDL (nHDL) in feto-placental endothelial dysfunction. Here, we report that the exposure of primary fetal placental arterial endothelial cell (fPAEC) to healthy nHDL-S1P attenuated the ability of TNFα to activate NF-κB signaling and increase the expression of pro-inflammatory markers. Moreover, the angiotensin II (AngII)-induced reactive oxygen species (ROS) production was blunted in the presence of nHDL, whereas it was preserved when the cells were preincubated with S1P receptor antagonists, suggesting that S1P accounts for the vascular protective function of nHDL at the feto-placental unit. These results highlight the importance of HDL and S1P metabolism and signaling in pregnancy pathophysiology.

Vascular endothelial growth factor C/A 2578 gene polymorphism and umbilical artery Doppler in preeclamptic women

INTRODUCTION

Preeclampsia is strongly associated with placental hypoperfusion. Genetic factors have an impact on the pathogenesis of preeclampsia. The aim is to assess the association of Vascular Endothelial Growth Factor (C2578A) gene polymorphism with the occurrence and severity of preeclampsia and the umbilical artery Doppler changes among preeclamptic women.

MATERIALS AND METHODS

This case-control study was conducted in clinical and Chemical pathology and Obstetrics departments in Beni- Suef University, Egypt. Two hundred and ninety pregnant women above 20 weeks gestational age until delivery were divided into 2 main groups. The patient group included 145 preeclamptic women who were further sub grouped according to the severity of preeclampsia into 82 severe and 63 mild cases. Control group included 145 normotensive pregnant women. Our primary outcome was detection of VEGF C 2578 A gene mutations by a polymerase chain reaction. A secondary outcome was Doppler changes in the pulsatility index of the umbilical artery compared with VEGF genotypes.

RESULTS

Our study showed that VEGF C 2578 A genotype and alleles frequencies were not related to the occurrence of preeclampsia (p-value 0.513 and 0.549, respectively), odds ratio (95%CI) 1.154 (0.724-1.848). Mild preeclamptic cases showed no significance comparing VEGF genotypes studied and pulsatility index of the umbilical artery. However, severe cases showed p-value < 0.0001.

CONCLUSION

We concluded that VEGF 2578C/A polymorphism had no association with the occurrence of preeclampsia in studied groups, whereas there was a significant relationship among severe cases between CA and CC genotypes and pulsatility index of the umbilical artery.

Outgrowth, proliferation, viability, angiogenesis and phenotype of primary human endothelial cells in different purchasable endothelial culture media: feed wisely

Function and dysfunction of endothelial cells are regulated by a multitude of factors. Endothelial cell research often requires in vitro cell culture experiments. Hence, various culture media specifically designed to promote endothelial cell growth are available. These strikingly differ in their composition: complex media contain endothelial cell growth supplement (ECGS), an extract produced of bovine brain with undefined amounts of biologically active compounds, whilst defined media contain selected growth factors in defined concentrations. We here compared the effect of seven purchasable endothelial cell culture media on colony outgrowth, proliferation, viability, in vitro angiogenesis and phenotype of mature primary human endothelial cells using feto-placental endothelial cells isolated from chorionic arteries (fpEC). The effect of media on colony outgrowth was additionally tested on umbilical cord blood-derived endothelial progenitor cells (ECFCs). Outgrowth, purity, proliferation and viability differed between media. Outgrowth of fpEC and ECFCs was best in a defined medium containing EGF, FGF2 and VEGF. By contrast, established fpEC isolations proliferated best in complex media containing ECGS, heparin and ascorbic acid. Also viability of cells was higher in complex media. In vitro angiogenesis was most intense in a defined medium containing the highest number of individual growth factors. FACS analysis of surface markers for endothelial cell subtypes revealed that endothelial phenotype of fpEC was unaffected by media composition. Our data demonstrate the fundamental effect of endothelial cell culture media on primary cell isolation success and behaviour. Whether the composition of supplements is suitable also for individual experiments needs to be tested specifically.

Expression of the neonatal Fc-receptor in placental-fetal endothelium and in cells of the placental immune system

INTRODUCTION

Starting from the second trimester of pregnancy, passive immunity is provided to the human fetus by transplacental transfer of maternal IgG. IgG transfer depends on the neonatal Fc receptor, FcRn. While FcRn localization in the placental syncytiotrophoblast (STB) has been demonstrated unequivocally, FcRn expression in placental-fetal endothelial cells (pFECs), which are part of the materno-fetal barrier, is still unclear. Therefore, this study aimed to elucidate the spatio-specific expression pattern of FcRn in placental tissue.

METHODS

FcRn expression was investigated by western blotting in term placentas and in isolated human placental arterial and venous endothelial cells (HPAEC, HPVEC) using a validated affinity-purified polyclonal anti-peptide antibody against the cytoplasmic tail of FcRn α-chain. In situ localization of FcRn and IgG was studied by immunofluorescence microscopy on tissue sections of healthy term placentas.

RESULTS

FcRn expression was demonstrated in placental vasculature particularly, in HPAEC, and HPVEC. FcRn was localized in cytokeratin 7⁺ STB and in CD31⁺ pFECs in terminal as well as stem villi in situ. Additionally, CD68⁺ placental macrophages exhibited FcRn expression in situ. Endogenous IgG partially co-localized with FcRn in STB, pFECs, and in placental macrophages.

DISCUSSION

Placental FcRn expression in endothelial cells and macrophages is analogous to the expression pattern in other organs. FcRn expression in pFECs suggests an involvement of FcRn in IgG transcytosis and/or participation in recycling/salvaging of maternal IgG present in the fetal circulation. FcRn expression in placental macrophages may account for recycling of monomeric IgG and/or processing and presentation of immune complexes.

First trimester placental endothelial cells from pregnancies with abnormal uterine artery Doppler are more sensitive to apoptotic stimuli

Failure of the placental capillary network to develop normally is associated with early onset fetal growth restriction (FGR) and pre-eclampsia (PE). Although the symptoms are observed at term, the problem begins in the first trimester. However, investigations at this clinically relevant time are hindered by difficulties in identifying earlystage pregnancies that are at risk of developing FGR/PE. Using uterine artery Doppler ultrasound in the first trimester as a proxy measure of poor placentation, we have identified pregnancies at increased risk of developing early onset FGR/PE. Placental endothelial cells (PEC) isolated from pregnancies at increased risk of developing FGR/PE grew more slowly and their basal rate of apoptosis was significantly higher than that seen in the normal group. The pro-apoptotic stimulus, TNFα, induced apoptosis in cells from both groups but this was significantly greater in the high risk group. TNF receptor expression was unaffected. Inhibition of nitric oxide (NO) production significantly increased the sensitivity of cells from the normal pregnancies to TNFα but not in the high risk group establishing a functional role for NO in this system. In conclusion, first trimester PEC from pregnancies at increased risk of developing early onset FGR/PE were inherently more sensitive to apoptotic stimuli and this was functionally linked to the synthesis of NO. This may contribute to the poor placental vascular development seen in on going pregnancies.

Amnion-derived mesenchymal stem cells improve viability of endothelial cells exposed to shear stress in ePTFE grafts

PURPOSE:

Blood vessel reconstruction is an increasing need of patients suffering from cardiovascular diseases. For the development of microvascular prostheses, efficient endothelialization is mandatory to prevent graft occlusion. Here, we assessed the impact of amnion-derived mesenchymal stem/stromal cells (hAMSC), known for their important angiogenic potential, on the integrity and stability of endothelial cells exposed to shear stress in vascular grafts.

METHODS:

Human placental endothelial cells (hPEC) were cultured at the inner surface of an expanded polytetrafluoroethylene (ePTFE) graft positioned within a bioreactor and exposed to a minimal shear stress of 0.015 dyne/cm² or a physiological shear stress of 0.92 dyne/cm². hAMSC attached to the outer graft surface were able to interact with human placental endothelial cells by paracrine factors.

RESULTS:

Microscopical analysis and evaluation of glucose/lactate metabolism evidenced successful cell seeding of the graft: hPEC formed a stable monolayer, hAMSC showed a continuous growth during 72 h incubation. hAMSC improved the viability of hPEC exposed to 0.015 dyne/cm² as shown by a decreased lactate dehydrogenase release of 13% after 72 h compared to hPEC single culture. The viability-enhancing effect of hAMSC on hPEC was further improved by 13% under physiological shear stress. Angiogenesis array analysis revealed that hPEC exposed to physiological shear stress and hAMSC co-culture reduced the secretion of angiogenin, GRO, MCP-1, and TIMP-2.

CONCLUSION:

hAMSC exerted best survival-enhancing effects on hPEC under exposure to physiological shear stress and modulated endothelial function by paracrine factors. Our data support further studies on the development of grafts functionalized with hAMSC-derived secretomes to enable fast clinical application.

Gestational diabetes alters microRNA signatures in human feto-placental endothelial cells depending on fetal sex

MicroRNAs (miRNAs), small non-coding RNAs, have emerged as important, epigenetic regulators of endothelial function. Metabolic disturbances such as diabetes alter miRNA expression. In adults, the miRNA transcriptome as well as endothelial function differ between the sexes. Here, we hypothesized that metabolic disturbances associated with gestational diabetes (GDM) alter miRNA signatures in feto-placental endothelial cells (fpEC), dependent on fetal sex. We isolated human primary fpEC after normal and GDM-complicated pregnancies with male and female neonates and screened for differential miRNA expression using next-generation miRNA sequencing. To test for miRNAs commonly regulated in fpEC of female and male progeny, data were stratified for fetal sex and maternal body mass index (BMI). Analyses were also performed separately for female and male fpEC, again accounting for maternal BMI as covariate. Potential biological pathways regulated by the altered set of miRNAs were determined using mirPath software. Maternal GDM altered 26 miRNA signatures when male and female fpEC were analyzed together. Separate analysis of male versus female fpEC revealed 22 GDM affected miRNAs in the females and only 4 in the males, without overlap. Biological functions potentially modulated by the affected miRNAs related to ‘Protein Processing in Endoplasmic Reticulum’ and ‘Proteoglycans in Cancer’. Maternal GDM alters miRNA signatures in fpEC, and biological functions affected by these miRNAs relate to well-known adverse functional consequences of diabetes on endothelium. GDM effects were highly dependent on fetal sex with miRNA signatures in female fpEC being more susceptible to metabolic derangements of GDM than miRNAs in male fpEC.

Human fetoplacental arterial and venous endothelial cells are differentially programmed by gestational diabetes mellitus, resulting in cell-specific barrier function changes

AIMS/HYPOTHESIS

An adverse intrauterine environment can result in permanent changes in the physiology of the offspring and predispose to diseases in adulthood. One such exposure, gestational diabetes mellitus (GDM), has been linked to development of metabolic disorders and cardiovascular disease in offspring. Epigenetic variation, including DNA methylation, is recognised as a leading mechanism underpinning fetal programming and we hypothesised that this plays a key role in fetoplacental endothelial dysfunction following exposure to GDM. Thus, we conducted a pilot epigenetic study to analyse concordant DNA methylation and gene expression changes in GDM-exposed fetoplacental endothelial cells.

METHODS

Genome-wide methylation analysis of primary fetoplacental arterial endothelial cells (AEC) and venous endothelial cells (VEC) from healthy pregnancies and GDM-complicated pregnancies in parallel with transcriptome analysis identified methylation and expression changes. Most-affected pathways and functions were identified by Ingenuity Pathway Analysis and validated using functional assays.

RESULTS

Transcriptome and methylation analyses identified variation in gene expression linked to GDM-associated DNA methylation in 408 genes in AEC and 159 genes in VEC, implying a direct functional link. Pathway analysis found that genes altered by exposure to GDM clustered to functions associated with 'cell morphology' and 'cellular movement' in healthy AEC and VEC. Further functional analysis demonstrated that GDM-exposed cells had altered actin organisation and barrier function.

CONCLUSIONS/INTERPRETATION

Our data indicate that exposure to GDM programs atypical morphology and barrier function in fetoplacental endothelial cells by DNA methylation and gene expression change. The effects differ between AEC and VEC, indicating a stringent cell-specific sensitivity to adverse exposures associated with developmental programming in utero.

DATA AVAILABILITY

DNA methylation and gene expression datasets generated and analysed during the current study are available at the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) database ( http://www.ncbi.nlm.nih.gov/geo ) under accession numbers GSE106099 and GSE103552, respectively.

Cell free hemoglobin in the fetoplacental circulation: a novel cause of fetal growth restriction?

Cell free hemoglobin impairs vascular function and blood flow in adult cardiovascular disease. In this study, we investigated the hypothesis that free fetal hemoglobin (fHbF) compromises vascular integrity and function in the fetoplacental circulation, contributing to the increased vascular resistance associated with fetal growth restriction (FGR). Women with normal and FGR pregnancies were recruited and their placentas collected freshly postpartum. FGR fetal capillaries showed evidence of erythrocyte vascular packing and extravasation. Fetal cord blood fHbF levels were higher in FGR than in normal pregnancies ( P < 0.05) and the elevation of fHbF in relation to heme oxygenase-1 suggests a failure of expected catabolic compensation, which occurs in adults. During ex vivo placental perfusion, pathophysiological fHbF concentrations significantly increased fetal-side microcirculatory resistance ( P < 0.05). fHbF sequestered NO in acute and chronic exposure models ( P < 0.001), and fHbF-primed placental endothelial cells developed a proinflammatory phenotype, demonstrated by activation of NF-κB pathway, generation of IL-1α and TNF-α (both P < 0.05), uncontrolled angiogenesis, and disruption of endothelial cell flow alignment. Elevated fHbF contributes to increased fetoplacental vascular resistance and impaired endothelial protection. This unrecognized mechanism for fetal compromise offers a novel insight into FGR as well as a potential explanation for associated poor fetal outcomes such as fetal demise and stillbirth.-Brook, A., Hoaksey, A., Gurung, R., Yoong, E. E. C., Sneyd, R., Baynes, G. C., Bischof, H., Jones, S., Higgins, L. E., Jones, C., Greenwood, S. L., Jones, R. L., Gram, M., Lang, I., Desoye, G., Myers, J., Schneider, H., Hansson, S. R., Crocker, I. P., Brownbill, P. Cell free hemoglobin in the fetoplacental circulation: a novel cause of fetal growth restriction?

Physiology and Pathophysiology of Steroid Biosynthesis, Transport and Metabolism in the Human Placenta

The steroid hormones progestagens, estrogens, androgens, and glucocorticoids as well as their precursor cholesterol are required for successful establishment and maintenance of pregnancy and proper development of the fetus. The human placenta forms at the interface of maternal and fetal circulation. It participates in biosynthesis and metabolism of steroids as well as their regulated exchange between maternal and fetal compartment. This review outlines the mechanisms of human placental handling of steroid compounds. Cholesterol is transported from mother to offspring involving lipoprotein receptors such as low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SRB1) as well as ATP-binding cassette (ABC)-transporters, ABCA1 and ABCG1. Additionally, cholesterol is also a precursor for placental progesterone and estrogen synthesis. Hormone synthesis is predominantly performed by members of the cytochrome P-450 (CYP) enzyme family including CYP11A1 or CYP19A1 and hydroxysteroid dehydrogenases (HSDs) such as 3β-HSD and 17β-HSD. Placental estrogen synthesis requires delivery of sulfate-conjugated precursor molecules from fetal and maternal serum. Placental uptake of these precursors is mediated by members of the solute carrier (SLC) family including sodium-dependent organic anion transporter (SOAT), organic anion transporter 4 (OAT4), and organic anion transporting polypeptide 2B1 (OATP2B1). Maternal-fetal glucocorticoid transport has to be tightly regulated in order to ensure healthy fetal growth and development. For that purpose, the placenta expresses the enzymes 11β-HSD 1 and 2 as well as the transporter ABCB1. This article also summarizes the impact of diverse compounds and diseases on the expression level and activity of the involved transporters, receptors, and metabolizing enzymes and concludes that the regulatory mechanisms changing the physiological to a pathophysiological state are barely explored. The structure and the cellular composition of the human placental barrier are introduced. While steroid production, metabolism and transport in the placental syncytiotrophoblast have been explored for decades, few information is available for the role of placental-fetal endothelial cells in these processes. With regard to placental structure and function, significant differences exist between species. To further decipher physiologic pathways and their pathologic alterations in placental steroid handling, proper model systems are mandatory.

Human Urine-Derived Stem Cell Differentiation to Endothelial Cells with Barrier Function and Nitric Oxide Production

Endothelial cells (ECs) play a key role in revascularization within regenerating tissue. Stem cells are often used as an alternative cell source when ECs are not available. Several cell types have been used to give rise to ECs, such as umbilical cord vessels, or differentiated from somatic stem cells, embryonic, or induced pluripotent stem cells. However, the latter carry the potential risk of chronic immune rejection and oncogenesis. Autologous endothelial precursors are an ideal resource, but currently require an invasive procedure to obtain them from the patient's own blood vessels or bone marrow. Thus, the goal of this study was to determine whether urine-derived stem cells (USCs) could differentiate into functional ECs in vitro. Urine-derived cells were then differentiated into cells of the endothelial lineage using endothelial differentiation medium for 14 days. Changes in morphology and ultrastructure, and functional endothelial marker expression were assessed in the induced USCs in vitro. Grafts of the differentiated USCs were then subcutaneously injected into nude mice. Induced USCs expressed significantly higher levels of specific markers of ECs (CD31, vWF, eNOS) in vitro and in vivo, compared to nondifferentiated USCs. In addition, the differentiated USC formed intricate tubular networks and presented similar tight junctions, and migration and invasion ability, as well as ability to produce nitric oxide (NO) compared to controls. Using USCs as autologous EC sources for vessel, tissue engineering strategies can yield a sufficient number of cells via a noninvasive, simple, and low-cost method suitable for rapid clinical translation. Stem Cells Translational Medicine 2018 Stem Cells Translational Medicine 2018;7:686-698.

Gestational diabetes mellitus modulates cholesterol homeostasis in human fetoplacental endothelium

Gestational diabetes mellitus (GDM) is associated with excessive oxidative stress which may affect placental vascular function. Cholesterol homeostasis is crucial for maintaining fetoplacental endothelial function. We aimed to investigate whether and how GDM affects cholesterol metabolism in human fetoplacental endothelial cells (HPEC). HPEC were isolated from fetal term placental arterial vessels of GDM or control subjects. Cellular reactive oxygen species (ROS) were detected by H₂DCFDA fluorescent dye. Oxysterols were quantified by gas chromatography-mass spectrometry analysis. Genes and proteins involved in cholesterol homeostasis were detected by real-time PCR and immunoblotting, respectively. Cholesterol efflux was determined from [³H]-cholesterol labeled HPEC and [¹⁴C]-acetate was used as cholesterol precursor to measure cholesterol biosynthesis and esterification. We detected enhanced formation of ROS and of specific, ROS-derived oxysterols in HPEC isolated from GDM versus control pregnancies. ROS-generated oxysterols were simultaneously elevated in cord blood of GDM neonates. Liver-X receptor activation in control HPEC by synthetic agonist TO901319, 7-ketocholesterol, or 7β-hydroxycholesterol upregulated ATP-binding cassette transporters (ABC)A1 and ABCG1 expression, accompanied by increased cellular cholesterol efflux. Upregulation of ABCA1 and ABCG1 and increased cholesterol release to apoA-I and HDL₃ (78 ± 17%, 40 ± 9%, respectively) were also observed in GDM versus control HPEC. The LXR antagonist GGPP reversed ABCA1 and ABCG1 upregulation and reduced the increased cholesterol efflux in GDM HPEC. Similar total cellular cholesterol levels were detected in control and GDM HPEC, while GDM enhanced cholesterol biosynthesis along with upregulated 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and sterol O-acyltransferase 1 (SOAT1) mRNA and protein levels. Our results suggest that in GDM cellular cholesterol homeostasis in the fetoplacental endothelium is modulated via LXR activation and helps to maintain its proper functionality.

Comparative study of regenerative effects of mesenchymal stem cells derived from placental amnion, chorion and umbilical cord on dermal wounds

OBJECTIVE

Mesenchymal stem/stromal cells derived from human term placentas (PMSCs) are novel therapeutic agents and more topical than ever. Here we evaluated the effects of three types of PMSCs on wound healing in an in vivo mouse model: Amnion-derived MSCs (AMSCs), blood vessel-derived MSCs (BV-MSCs) from the chorionic plate and Wharton's jelly-derived MSCs (WJ-MSCs) from the umbilical cord.

METHODS

We topically applied PMSCs onto skin wounds in mice using the dermal substitute Matriderm^® as carrier and evaluated wound healing parameters. In addition, we investigated the effects of all PMSC types under co-application with placental endothelial cells (PLECs). After 8 days, we compared the percent of wound closure and the angiogenic potential between all groups.

RESULTS

AMSCs, BV-MSCs and WJ-MSCs significantly induced a faster healing and a higher number of blood vessels in the wound when compared to controls (Matriderm^®-alone). PLECs did not further improve the advantageous effects of PMSC-treatment. Quantitative data and 3D analysis by high resolution episcopic microscopy confirmed a lower density of vessels in Matriderm^®/PMSCs/PLECs co-application compared to Matriderm^®/PMSCs treatment.

CONCLUSION

Results indicate that all three PMSC types exert similar beneficial effects on wound closure and neovascularization in our mouse model.

PRACTICE

Using Matriderm^® as carrier for PMSCs propagates rapid cell migration towards the wound area that allows a fast and clinically practicable method for stem cell application.

IMPLICATIONS

These promising effects warrant further investigation in clinical trials.

Endothelial indoleamine 2,3-dioxygenase-1 regulates the placental vascular tone and is deficient in intrauterine growth restriction and pre-eclampsia

Indoleamine 2,3-dioxygenase-1 (IDO1) mediates the degradation of L-tryptophan (L-Trp) and is constitutively expressed in the chorionic vascular endothelium of the human placenta with highest levels in the microvasculature. Given that endothelial expression of IDO1 has been shown to regulate vascular tone and blood pressure in mice under the condition of systemic inflammation, we asked whether IDO1 is also involved in the regulation of placental blood flow and if yes, whether this function is potentially impaired in intrauterine growth restriction (IUGR) and pre-eclampsia (PE). In the large arteries of the chorionic plate L-Trp induced relaxation only after upregulation of IDO1 using interferon gamma and tumor necrosis factor alpha. However, ex vivo placental perfusion of pre-constricted cotyledonic vasculature with L-Trp decreases the vessel back pressure without prior IDO1 induction. Further to this finding, IDO1 protein expression and activity is reduced in IUGR and PE when compared to gestational age–matched control tissue. These data suggest that L-Trp catabolism plays a role in the regulation of placental vascular tone, a finding which is potentially linked to placental and fetal growth. In this context our data suggest that IDO1 deficiency is related to the pathogenesis of IUGR and PE.

Fatty acid transporter expression and regulation is impaired in placental macrovascular endothelial cells in obese women

OBJECTIVE

Fetal fatty acid (FA) delivery is ultimately controlled by placental transport. Focus has been the maternal-placental interface, but regulation at the feto-placental interface is unknown.

METHODS

Placental macrovascular endothelial cells (EC) (n = 4/group) and trophoblasts (TB) (n = 5/group) were isolated from lean (pregravid BMI <25 kg/m²) and obese (body mass index (BMI) > 30) women. Fatty acid transporters FAT/CD36, FABPpm, FATP4, FABP 3, 4 and 5, PLIN2 and PPARα, δ, γ expression, was measured in EC and TB. Transporter response to 24 h palmitate (PA) was assessed.

RESULTS

mRNA expression of FABP3, 4, 5 and PPARγ was 2- to 3-fold reduced in EC of obese versus lean women (p < .03), but not in TB. Protein level of FABPpm was 20% lower in obese (p < .05). Palmitate (PA) up-regulated CD36, FABP3, FABP4, and PLIN2 gene expression by 3- to 4-fold in lean but not obese EC (p < .05), while PA increased FABP4 and PLIN2 in lean and obese TB, and FABP5 in lean (p < .05) EC. PA exposure up-regulated peroxisome proliferator activated receptors (PPARs) 2-fold in lean and obese EC (p < .05), but not in TB.

CONCLUSIONS

In obese women, FA transporter expression is lower in placental EC, but not TB, and less sensitive to saturated FA, compared to lean women. FA transport may be regulated at the feto-placental interface.

Maternal Gestational Diabetes Mellitus increases placental and foetal lipoprotein-associated Phospholipase A2 which might exert protective functions against oxidative stress

Increased Lipoprotein associated phospholipase A2 (LpPLA2) has been associated with inflammatory pathologies, including Type 2 Diabetes. Studies on LpPLA2 and Gestational Diabetes Mellitus (GDM) are rare, and have focused mostly on maternal outcome. In the present study, we investigated whether LpPLA2 activity on foetal lipoproteins is altered by maternal GDM and/or obesity (a major risk factor for GDM), thereby contributing to changes in lipoprotein functionality. We identified HDL as the major carrier of LpPLA2 activity in the foetus, which is in contrast to adults. We observed marked expression of LpPLA2 in placental macrophages (Hofbauer cells; HBCs) and found that LpPLA2 activity in these cells was increased by insulin, leptin, and pro-inflammatory cytokines. These regulators were also increased in plasma of children born from GDM pregnancies. Our results suggest that insulin, leptin, and pro-inflammatory cytokines are positive regulators of LpPLA2 activity in the foeto-placental unit. Of particular interest, functional assays using a specific LpPLA2 inhibitor suggest that high-density lipoprotein (HDL)-associated LpPLA2 exerts anti-oxidative, athero-protective functions on placental endothelium and foetus. Our results therefore raise the possibility that foetal HDL-associated LpPLA2 might act as an anti-inflammatory enzyme improving vascular barrier function.

Human Placental Hofbauer Cells Maintain an Anti-inflammatory M2 Phenotype despite the Presence of Gestational Diabetes Mellitus

Background

Hofbauer cells (HBCs) are macrophages of the feto-placental unit. Despite the general view that these cells have an anti-inflammatory M2 phenotype, recent studies have claimed that pregnancy pathologies—e.g., gestational diabetes mellitus (GDM)—cause a switch from an M2 to an M1 pro-inflammatory phenotype in HBCs. The pilot-study presented here challenges this claim, showing that HBCs maintain anti-inflammatory properties in spite of the hyperglycemic, low-grade inflammatory environment of GDM.

Methods

HBCs were isolated from placentae of healthy women (N = 5) and women with GDM (N = 6) diagnosed in the second trimester. FACS was used to measure surface markers associated with either M1 or M2 phenotype on the cells. In addition, placental tissue sections were subjected to immune histochemical imaging to assess the phenotype within the tissue context. Supernatant from control and GDM HBCs was collected at defined time points and used in a multiplex ELISA-on-beads approach to assess secretion of cytokines, chemokines, and growth factors. The effect of HBC cell culture supernatant on placental endothelial activation was investigated.

Results

FACS and immune staining showed that, indeed, M2 markers, such as CD206 and CD209, are increased in HBCs isolated from GDM placentae. Also, the M1 marker CD86 was increased, but only by trend. Secretion of numerous cytokines, chemokines and growth factors was not changed; pro-inflammatory interleukin (IL)-1β and IL-6 release form GDM HBC was increased but not significant. Exposure to GDM HBC supernatant did not induce cell adhesion molecules (VCAM-1, selectins, vascular endothelial-cadherin) in placental endothelial cells compared to supernatant from control HBCs, an induction of intracellular adhesion molecule 1 was observed however.

Conclusion

Our study—although performed in a small set of patients—shows that placental macrophages maintain their anti-inflammatory, tissue remodeling M2 phenotype even in pregnancies affected by gestational diabetes. This consistent phenotype might be important for propagation of maternal tolerance toward the fetus and for protection of the fetus from a low-grade inflammatory environment.

GDM alters paracrine regulation of feto-placental angiogenesis via the trophoblast

Feto-placental angiogenesis and vascular development are tightly regulated by pro- and anti-angiogenic factors. Villous trophoblast may be a major source of these factors. It forms the classical placental barrier between mother and fetus, and is thus exposed to maternal influences as well. Metabolic and hormonal derangements in gestational diabetes mellitus (GDM) affect feto-placental angiogenesis and vascular growth. Here we hypothesized that GDM alters the trophoblast secretome, which will modulate the paracrine regulation of feto-placental angiogenesis. Primary term trophoblasts were isolated from normal (n=6) and GDM (n=6) pregnancies. Trophoblast conditioned medium (CM) was used to investigate paracrine effects of normal and GDM-exposed trophoblasts on feto-placental endothelial cells (fpECs; n=7), using functional assays for 2D network formation, wound healing, chemotaxis, and proliferation. Gene expression of 23 pro- and anti-angiogenic factors was analyzed. Four trophoblast-derived paracrine regulators of angiogenesis were specifically measured in CM. CM from GDM trophoblasts increased 2D network formation of fpEC by 2.4-fold (P<0.001), whereas wound healing was attenuated by 1.8-fold (P=0.02) and chemo-attraction to the CM was reduced by 33±9% (P=0.02). The effect of CM on proliferation was unchanged between normal and GDM trophoblasts. Expression analysis of pro- and anti-angiogenic molecules in normal and GDM trophoblasts revealed significant differences in ANGPT2, HGF, KISS1 and PLGF expression. Analysis of secreted proteins demonstrated reduced pigment epithelium derived factor and tumor necrosis factor-α secretion by GDM trophoblasts. GDM alters the balance of trophoblast derived, angiogenesis modulating paracrine factors. This may contribute to GDM-associated changes in placental angiogenesis and vascular structure.

Causal relationship between obesity-related traits and TLR4-driven responses at the maternal-fetal interface

AIMS/HYPOTHESIS

Obesity triggers complex inflammatory networks within the innate immune system. During pregnancy, the placenta amplifies the low-grade inflammation through activation of Toll-like receptor 4 (TLR4) signalling pathways. The purpose of this study was to investigate the impact of obesity on placental TLR4 expression and inflammatory signals. The secondary aim was to analyse the placental cell type responsible for TLR4 activation.

METHODS

Thirty-nine women recruited at term-scheduled Caesarean section were grouped according to their pre-gravid BMI (<25 kg/m(2) and >30 kg/m(2)). Placenta, venous maternal and cord blood were obtained at delivery for analysis. Data were analysed with linear regression and Spearman's rank correlation coefficient analysis.

RESULTS

TLR4, IL6 and IL8 expression was increased three- to ninefold (p < 0.001) in the placenta of obese vs lean women. There was a positive correlation between placental TLR4 and maternal systemic and placental IL6 and IL8 concentrations. Placental TLR4 expression was correlated with maternal pre-gravid BMI, insulin resistance index, plasma insulin and C-reactive protein (r = 0.57, 0.31, 0.35, 0.53, respectively; p < 0.001) but not with plasma glucose, maternal age, gestational age and gestational weight gain (r < 0.2; p > 0.1). TLR4 was located in both trophoblast and macrovascular endothelial cells lining fetal vasculature. Lipopolysaccharide-induced TLR4 activation was more robust in trophoblasts than in endothelial vascular cells (100-fold vs tenfold; p < 0.001).

CONCLUSIONS/INTERPRETATION

Trophoblastic TLR4 is strongly implicated in the propagation of placental inflammation. Placental inflammation is related to maternal metabolic conditions such as pre-gravid BMI, whilst gestational weight gain or gestational age are not. These results implicate the pre-gravid condition as a significant contributor to metabolic inflammation in late pregnancy.

Extravillous trophoblasts invade more than uterine arteries: evidence for the invasion of uterine veins

During the first trimester of pregnancy, extravillous trophoblasts (EVTs) invade into the decidual interstitium to the first third of the myometrium, thereby anchoring the placenta to the uterus. They also follow the endovascular and endoglandular route of invasion; plug, line and remodel spiral arteries, thus being responsible for the establishment of hemotrophic nutrition with the beginning of the second trimester and invade and open uterine glands toward the intervillous space for a histiotrophic nutrition during the first trimester. The aim of this study was to provide proof that uterine veins are invaded by EVTs similar to uterine arteries and glands in first trimester of pregnancy. Therefore, serial sections from in situ first trimester placenta were immuno-single- and immuno-double-stained to distinguish in a first step between arteries and veins and secondly between invaded and non-invaded vessels. Subsequently, invasion of EVTs into uterine vessels was quantified. Our data show that uterine veins are significantly more invaded by EVTs than uterine arteries (29.2 ± 15.7 %) during early pregnancy. Counted vessel cross sections revealed significantly higher EVT invasion into veins (59.5 ± 7.9 %) compared to arteries (29.2 ± 15.7 %). In the lumen of veins, single EVTs were repeatedly found, beside detached glandular epithelial cells or syncytial fragments. This study allows the expansion of our hitherto postulated concept of EVT invasion during first trimester of pregnancy. We suggest that invasion of EVTs into uterine veins is responsible the draining of waste and blood plasma from the intervillous space during the first trimester of pregnancy.

An international network (PlaNet) to evaluate a human placental testing platform for chemicals safety testing in pregnancy

The human placenta is a critical life-support system that nourishes and protects a rapidly growing fetus; a unique organ, species specific in structure and function. We consider the pressing challenge of providing additional advice on the safety of prescription medicines and environmental exposures in pregnancy and how ex vivo and in vitro human placental models might be advanced to reproducible human placental test systems (HPTSs), refining a weight of evidence to the guidance given around compound risk assessment during pregnancy. The placental pharmacokinetics of xenobiotic transfer, dysregulated placental function in pregnancy-related pathologies and influx/efflux transporter polymorphisms are a few caveats that could be addressed by HPTSs, not the specific focus of current mammalian reproductive toxicology systems. An international consortium, "PlaNet", will bridge academia, industry and regulators to consider screen ability and standardisation issues surrounding these models, with proven reproducibility for introduction into industrial and clinical practice.

Post-transcriptional down regulation of ICAM-1 in feto-placental endothelium in GDM

Maternal gestational diabetes (GDM) is associated with hyperglycaemia and hyperinsulinemia in the fetal circulation which consequently may induce endothelial dysfunction in the feto-placental vasculature. In fact, feto-placental vasculature reveals various morphological changes in response to GDM. The cell adhesion molecules (CAMs) ICAM-1, VCAM-1 and E-selectin promote attachment and trans-endothelial migration of leukocytes, and are up regulated in inflammation and endothelial dysfunction. Thus, we hypothesized that the GDM environment upregulates ICAM-1, VCAM-1 and E-selectin in the feto-placental endothelium. We isolated primary feto-placental endothelial cells (fpEC) after normal (n=18) and GDM pregnancy (n=11) and analyzed mRNA (RT-qPCR) and protein expression (Immunoblot) of ICAM-1, VCAM-1 and E-selectin. While other CAMs were unchanged on mRNA and protein levels, ICAM-1 protein was decreased by GDM. Further analysis revealed also a decrease in the release of soluble ICAM-1 (sICAM-1), whose levels correlated negatively with maternal BMI. We conclude that this reduction of ICAM-1 protein species is the result of post-translational regulation, since ICAM-1 mRNA expression was unchanged. In fact, miRNAs targeting ICAM-1 were upregulated in GDM fpEC. Immunohistochemistry showed weaker ICAM-1 staining in the placental endothelium after GDM pregnancies, and demonstrated ICAM-1 binding partners CD11a and CD18 expressed on leukocytes in fetal circulation and on placental tissue macrophages. This study identified reduction of ICAM-1 protein in fpEC in GDM pregnancy, which was regulated post-transcriptionally. Low ICAM-1 protein production may represent a protective, placenta-specific mechanism to avoid leukocyte transmigration into the placenta in response to GDM.

Role of the fetoplacental endothelium in fetal growth restriction with abnormal umbilical artery Doppler velocimetry

Growth-restricted fetuses with absent or reversed end-diastolic velocities in the umbilical artery are at substantially increased risk for adverse perinatal and long-term outcome, even in comparison to growth-restricted fetuses with preserved end-diastolic velocities. Translational studies show that this Doppler velocimetry correlates with fetoplacental blood flow, with absent or reversed end-diastolic velocities signifying abnormally elevated resistance within the placental vasculature. The fetoplacental vasculature is unique in that it is not subject to autonomic regulation, unlike other vascular beds. Instead, humoral mediators, many of which are synthesized by local endothelial cells, regulate placental vascular resistance. Existing data demonstrate that in growth-restricted pregnancies complicated by absent or reversed umbilical artery end-diastolic velocities, an imbalance in production of these vasoactive substances occurs, favoring vasoconstriction. Morphologically, placentas from these pregnancies also demonstrate impaired angiogenesis, whereby vessels within the terminal villi are sparsely branched, abnormally thin, and elongated. This structural deviation from normal placental angiogenesis restricts blood flow and further contributes to elevated fetoplacental vascular resistance. Although considerable work has been done in the field of fetoplacental vascular development and function, much remains unknown about the mechanisms underlying impaired development and function of the human fetoplacental vasculature, especially in the context of severe fetal growth restriction with absent or reversed umbilical artery end-diastolic velocities. Fetoplacental endothelial cells are key regulators of angiogenesis and vasomotor tone. A thorough understanding of their role in placental vascular biology carries the significant potential of discovering clinically relevant and innovative approaches to prevention and treatment of fetal growth restriction with compromised umbilical artery end-diastolic velocities.

Placental mesenchymal stromal cells derived from blood vessels or avascular tissues: what is the better choice to support endothelial cell function?

Mesenchymal stromal cells (MSCs) are promising tools for therapeutic revascularization of ischemic tissues and for support of vessel formation in engineered tissue constructs. Recently, we could show that avascular-derived MSCs from placental amnion release soluble factors that exhibit survival-enhancing effects on endothelial cells (ECs). We hypothesize that MSCs derived from placental blood vessels might have even more potent angiogenic effects. Therefore, we isolated and characterized MSCs from placental chorionic blood vessels (bv-MSCs) and tested their angiogenic potential in comparison to amnion-derived avascular MSCs (av-MSCs). bv-MSCs express a very similar surface marker profile compared with av-MSCs and could be differentiated toward the adipogenic and osteogenic lineages. bv-MSCs exert immunosuppressive properties on peripheral blood mononuclear cells, suggesting that they are suitable for cell transplantation settings. Conditioned medium (Cdm) from av-MSCs and bv-MSCs significantly enhanced EC viability, whereas only Cdm from bv-MSCs significantly increased EC migration and network formation (Matrigel assay). Angiogenesis array analysis of av- and bv-MSC-Cdm revealed a similar secretion pattern of angiogenic factors, including angiogenin, interleukins-6 and -8, and tissue inhibitors of matrix metalloproteinase-1 and 2. Enzyme-linked immunosorbent assay analysis showed that, in contrast to av-MSCs, bv-MSCs secreted vascular endothelial growth factor. In direct coculture with bv-MSCs, ECs showed a significantly increased formation of vessel-like structures compared with av-MSCs. With regard to therapeutic treatment, bv-MSCs and particularly their Cdm might be valuable to stimulate angiogenesis especially in ischemic tissues. av-MSCs and their Cdm could be beneficial in conditions when it is required to promote the survival and stabilization of blood vessels without the risk of unmeant angiogenesis.

Dysregulated flow-mediated vasodilatation in the human placenta in fetal growth restriction

Increased vascular resistance and reduced fetoplacental blood flow are putative aetiologies in the pathogenesis of fetal growth restriction (FGR); however, the regulating sites and mechanisms remain unclear. We hypothesised that placental vessels dictate fetoplacental resistance and in FGR exhibit endothelial dysfunction and reduced flow-mediated vasodilatation (FMVD). Resistance was measured in normal pregnancies (n = 10) and FGR (n = 10) both in vivo by umbilical artery Doppler velocimetry and ex vivo by dual placental perfusion. Ex vivo FMVD is the reduction in fetal-side inflow hydrostatic pressure (FIHP) following increased flow rate. Results demonstrated a significant correlation between vascular resistance measured in vivo and ex vivo in normal pregnancy, but not in FGR. In perfused FGR placentas, vascular resistance was significantly elevated compared to normal placentas (58 ± 7.7 mmHg and 36.8 ± 4.5 mmHg, respectively; 8 ml min⁻¹; means ± SEM; P < 0.0001) and FMVD was severely reduced (3.9 ± 1.3% and 9.1 ± 1.2%, respectively). In normal pregnancies only, the highest level of ex vivo FMVD was associated with the lowest in vivo resistance. Inhibition of NO synthesis during perfusion (100 μm l-NNA) moderately elevated FIHP in the normal group, but substantially in the FGR group. Human placenta artery endothelial cells from FGR groups exhibited increased shear stress-induced NO generation, iNOS expression and eNOS expression compared with normal groups. In conclusion, fetoplacental resistance is determined by placental vessels, and is increased in FGR. The latter also exhibit reduced FMVD, but with a partial compensatory increased NO generation capacity. The data support our hypothesis, which highlights the importance of FMVD regulation in normal and dysfunctional placentation.