Transcriptional and functional adaptations of human endothelial cells to physiological chronic low oxygen

Venous valve hypoxia as a possible mechanism of deep vein thrombosis: a scoping review

INTRODUCTION

The pathogenesis of deep vein thrombosis (DVT) has been explained by an interplay between a changed blood composition, vein wall alteration, and blood flow abnormalities. A comprehensive investigation of these components of DVT pathogenesis has substantially promoted our understanding of thrombogenesis in the venous system. Meanwhile, the process of DVT initiation remains obscure. This systematic review aims to collect, analyze, and synthesize the published evidence to propose hypoxia as a possible trigger of DVT.

EVIDENCE ACQUISITION

An exhaustive literature search was conducted across multiple electronic databased including PubMed, EMBASE, Scopus, and Web of Science to identify studies pertinent to the research hypothesis. The search was aimed at exploring the connection between hypoxia, reoxygenation, and the initiation of deep vein thrombosis (DVT). The following key words were used: "deep vein thrombosis," "venous thrombosis," "venous thromboembolism," "hypoxia," "reoxygenation," "venous valve," and "venous endothelium." Reviews, case reports, editorials, and letters were excluded.

EVIDENCE SYNTHESIS

Based on the systematic search outcome, 156 original papers relevant to the issue were selected for detailed review. These studies encompassed a range of experimental and observational clinical research, focusing on various aspects of DVT, including the anatomical, physiological, and cellular bases of the disease. A number of studies suggested limitations in the traditional understanding of Virchow's triad as an acceptable explanation for DVT initiation. Emerging evidence points to more complex interactions and additional factors that may be critical in the early stages of thrombogenesis. The role of venous valves has been recognized but remains underappreciated, with several studies indicating that these sites may act as primary loci for thrombus formation. A collection of studies describes the effects of hypoxia on venous endothelial cells at the cellular and molecular levels. Hypoxia influences several pathways that regulate endothelial cell permeability, inflammatory response, and procoagulation activity, underpinning the endothelial dysfunction noted in DVT.

CONCLUSIONS

Hypoxia of the venous valve may serve as an independent hypothesis to outline the DVT triggering process. Further research projects in this field may discover new molecular pathways responsible for the disease and suggest new therapeutic targets.

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.

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.

Hyperoxia Reprogrammes Microvascular Endothelial Cell Response to Hypoxia in an Organ-Specific Manner

Organ function relies on microvascular networks to maintain homeostatic equilibrium, which varies widely in different organs and during different physiological challenges. The endothelium role in this critical process can only be evaluated in physiologically relevant contexts. Comparing the responses to oxygen flux in primary murine microvascular EC (MVEC) obtained from brain and lung tissue reveals that supra-physiological oxygen tensions can compromise MVEC viability. Brain MVEC lose mitochondrial activity and undergo significant alterations in electron transport chain (ETC) composition when cultured under standard, non-physiological atmospheric oxygen levels. While glycolytic capacity of both lung and brain MVEC are unchanged by environmental oxygen, the ability to trigger a metabolic shift when oxygen levels drop is greatly compromised following exposure to hyperoxia. This is particularly striking in MVEC from the brain. This work demonstrates that the unique metabolism and function of organ-specific MVEC (1) can be reprogrammed by external oxygen, (2) that this reprogramming can compromise MVEC survival and, importantly, (3) that ex vivo modelling of endothelial function is significantly affected by culture conditions. It further demonstrates that physiological, metabolic and functional studies performed in non-physiological environments do not represent cell function in situ, and this has serious implications in the interpretation of cell-based pre-clinical models.

Specific arterio-venous transcriptomic and ncRNA-RNA interactions in human umbilical endothelial cells: A meta-analysis

Whether arterial-venous differences of primary endothelial cells commonly used for vascular research are preserved in vitro remains under debate. To address this issue, a meta-analysis of Affymetrix transcriptomic data sets from human umbilical artery (HUAECs) and vein (HUVEC) endothelial cells was performed. The meta-analysis showed 2,742 transcripts differentially expressed (false discovery rate <0.05), of which 78% were downregulated in HUVECs. Comparisons with RNA-seq data sets showed high levels of agreement and correlation (p < 0.0001), identifying 84 arterial-venous identity markers. Functional analysis revealed enrichment of key vascular processes in HUAECs/HUVECs, including nitric oxide- (NO) and hypoxia-related genes, as well as differences in miRNA- and ncRNA-mRNA interaction profiles. A proof of concept of these findings in primary cells exposed to hypoxia in vitro and in vivo confirmed the arterial-venous differences in NO-related genes and miRNAs. Altogether, these data defined a cross-platform arterial-venous transcript profile for cultured HUAEC-HUVEC and support a preserved identity involving key vascular pathways post-transcriptionally regulated in vitro.

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Transcriptional differences among HUAEC and HUVEC are preserved in culture

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These differences occur even after correcting for experimental conditions

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The heterogenous regulation affects NO- and hypoxia-related genes

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Cell-specific ncRNA/mRNA interactions are found

Roles of aryl hydrocarbon receptor in endothelial angiogenic responses†

Aryl hydrocarbon receptor (AhR) is a transcription factor, which can be activated by a plethora of structure-diverse ligands. Historically, AhR is known for its involvements in regulation of metabolism of xenobiotics. However, normal physiological roles of AhR have been defined in other essential biological processes, including vascular growth and function, reproduction, and immunoresponses. In contrast, aberrant expression and activation of the AhR signaling pathway occur in a variety of human diseases, many of which (e.g., preeclampsia, atherosclerosis, and hypertension) could be associated with endothelial dysfunction. Indeed, emerging evidence has shown that either exogenous or endogenous AhR ligands can induce endothelial dysfunction in either an AhR-dependent or AhR-independent manner, possibly reliant on the blood vessel origin (artery and vein) of endothelial cells. Given that the AhR signaling pathway has broad impacts on endothelial and cardiovascular function, AhR ligands, AhR, and their downstream genes could be considered novel therapeutic targets for those endothelial-related diseases. This review will discuss the current knowledge of AhR's mediation on endothelial function and potential mechanisms underlying these actions with a focus on placental endothelial cells.

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.

Apolipoprotein E4 Expression Causes Gain of Toxic Function in Isogenic Human Induced Pluripotent Stem Cell-Derived Endothelial Cells

OBJECTIVE

The ApoE (apolipoprotein) allele epsilon 4 is a major genetic risk factor for Alzheimer disease, cardiovascular disorders, and stroke, indicating that it significantly impacts cerebral and vascular systems. However, very little is known about how APOE genotype affects brain endothelial cells, which form a network of tight junctions to regulate communication between the brain and circulating blood factors. Approach and Results: Here, we present a novel model of endothelial dysfunction using isogenic human induced pluripotent stem cell-derived cells harboring different alleles of the APOE gene, specifically ApoE 3/3, 3/4, and 4/4. We show for the first time that ApoE4 expression by endothelial cells is sufficient to cause a toxic gain of cellular dysfunction. Using RNAseq, we found significant effects of ApoE4 on signaling pathways involved in blood coagulation and barrier function. These changes were associated with altered cell function, including increased binding of platelets to ECs with the 3/4 or 4/4 genotype. ApoE4-positive cells exhibited a proinflammatory state and prothrombotic state, evidenced by higher secretion of Aβ (amyloid-β) 40 and 42, increased release of cytokines, and overexpression of the platelet-binding protein VWF (vonWillebrand factor). Immunohistochemistry of human brain Alzheimer disease brains also showed increased VWF expression with the ApoE4/4 genotype. Finally, pharmacological inhibition of inflammation in ECs by celastrol rescued overexpression of VWF in cells expressing ApoE4.

CONCLUSIONS

These cells provide novel insight into ApoE4-mediated endothelial dysfunction and provide a new platform to test potential therapies for vascular disorders.

Sexual Dimorphisms of Preeclampsia-Dysregulated Transcriptomic Profiles and Cell Function in Fetal Endothelial Cells

Preeclampsia impairs fetoplacental vascular function and increases risks of adult-onset cardiovascular disorders in children born to preeclamptic mothers, implicating that preeclampsia programs fetal vasculature in utero. However, the underlying mechanisms remain elusive. We hypothesize that preeclampsia alters fetal endothelial gene expression and disturbs cytokines- and growth factors-induced endothelial responses. RNA sequencing analysis was performed on unpassaged human umbilical vein endothelial cells (HUVECs) from normotensive and preeclamptic pregnancies. Functional assays for endothelial monolayer integrity, proliferation, and migration were conducted on passage 1 HUVECs from normotensive and preeclamptic pregnancies. Compared with normotensive cells, 926 and 172 genes were dysregulated in unpassaged female and male HUVECs from preeclamptic pregnancies, respectively. Many of these preeclampsia-dysregulated genes are associated with cardiovascular diseases (eg, heart failure) and endothelial function (eg, cell migration, calcium signaling, and endothelial nitric oxide synthase signaling). TNF (tumor necrosis factor)-α-, TGF (transforming growth factor)-β1-, FGF (fibroblast growth factor)-2-, and VEGFA (vascular endothelial growth factor A)-regulated gene networks were differentially disrupted in unpassaged female and male HUVECs from preeclamptic pregnancies. Moreover, preeclampsia decreased endothelial monolayer integrity in responses to TNF-α in both female and male HUVECs. Preeclampsia decreased TGF-β1-strengthened monolayer integrity in female HUVECs, whereas it enhanced FGF-2-strengthened monolayer integrity in male HUVECs. Preeclampsia promoted TNF-α-, TGF-β1-, and VEGFA-induced cell proliferation in female, but not in male HUVECs. Preeclampsia inhibited TNF-α-induced cell migration in female HUVECs, but had an opposite effect on male HUVECs. In conclusion, preeclampsia differentially dysregulates cardiovascular diseases- and endothelial function-associated genes/pathways in female and male fetal endothelial cells in association with the sexual dimorphisms of preeclampsia-dysregulated fetal endothelial function.

GIPC proteins negatively modulate Plexind1 signaling during vascular development

Semaphorins (SEMAs) and their Plexin (PLXN) receptors are central regulators of metazoan cellular communication. SEMA-PLXND1 signaling plays important roles in cardiovascular, nervous, and immune system development, and cancer biology. However, little is known about the molecular mechanisms that modulate SEMA-PLXND1 signaling. As PLXND1 associates with GIPC family endocytic adaptors, we evaluated the requirement for the molecular determinants of their association and PLXND1's vascular role. Zebrafish that endogenously express a Plxnd1 receptor with a predicted impairment in GIPC binding exhibit low penetrance angiogenesis deficits and antiangiogenic drug hypersensitivity. Moreover, gipc mutant fish show angiogenic impairments that are ameliorated by reducing Plxnd1 signaling. Finally, GIPC depletion potentiates SEMA-PLXND1 signaling in cultured endothelial cells. These findings expand the vascular roles of GIPCs beyond those of the Vascular Endothelial Growth Factor (VEGF)-dependent, proangiogenic GIPC1-Neuropilin 1 complex, recasting GIPCs as negative modulators of antiangiogenic PLXND1 signaling and suggest that PLXND1 trafficking shapes vascular development.

Defining Physiological Normoxia for Improved Translation of Cell Physiology to Animal Models and Humans

The extensive oxygen gradient between the air we breathe (Po₂ ~21 kPa) and its ultimate distribution within mitochondria (as low as ~0.5-1 kPa) is testament to the efforts expended in limiting its inherent toxicity. It has long been recognized that cell culture undertaken under room air conditions falls short of replicating this protection in vitro. Despite this, difficulty in accurately determining the appropriate O₂ levels in which to culture cells, coupled with a lack of the technology to replicate and maintain a physiological O₂ environment in vitro, has hindered addressing this issue thus far. In this review, we aim to address the current understanding of tissue Po₂ distribution in vivo and summarize the attempts made to replicate these conditions in vitro. The state-of-the-art techniques employed to accurately determine O₂ levels, as well as the issues associated with reproducing physiological O₂ levels in vitro, are also critically reviewed. We aim to provide the framework for researchers to undertake cell culture under O₂ levels relevant to specific tissues and organs. We envisage that this review will facilitate a paradigm shift, enabling translation of findings under physiological conditions in vitro to disease pathology and the design of novel therapeutics.

G Protein α Subunit 14 Mediates Fibroblast Growth Factor 2-Induced Cellular Responses in Human Endothelial Cells

During pregnancy, a tremendous increase in fetoplacental angiogenesis is associated with elevated blood flow. Aberrant fetoplacental vascular function may lead to pregnancy complications including pre-eclampsia. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are crucial regulators of fetoplacental endothelial function. G protein α subunit 14 (GNA14), a member of Gαq/11 subfamily is involved in mediating hypertensive diseases and tumor vascularization. However, little is known about roles of GNA14 in mediating the FGF2- and VEGFA-induced fetoplacental endothelial function. Using human umbilical vein endothelial cells (HUVECs) cultured under physiological chronic low oxygen (3% O₂ ) as a cell model, we show that transfecting cells with adenovirus carrying GNA14 complementary DNA (cDNA; Ad-GNA14) increases (p < 0.05) protein expression of GNA14. GNA14 overexpression blocks (p < 0.05) FGF2-stimulated endothelial migration, whereas it enhances (p < 0.05) endothelial monolayer integrity (maximum increase of ~35% over the control at 24 hr) in response to FGF2. In contrast, GNA14 overexpression does not significantly alter VEGFA-stimulated cell migration, VEGFA-weakened cell monolayer integrity, and intracellular Ca⁺⁺ mobilization in response to adenosine triphosphate (ATP), FGF2, and VEGFA. GNA14 overexpression does not alter either FGF2- or VEGFA-induced phosphorylation of ERK1/2. However, GNA14 overexpression time-dependently elevates (p < 0.05) phosphorylation of phospholipase C-β3 (PLCβ3) at S1105 in response to FGF2, but not VEGFA. These data suggest that GNA14 distinctively mediates fetoplacental endothelial cell migration and permeability in response to FGF2 and VEGFA, possibly in part by altering activation of PLCβ3 under physiological chronic low oxygen.

GNA11 differentially mediates fibroblast growth factor 2- and vascular endothelial growth factor A-induced cellular responses in human fetoplacental endothelial cells

KEY POINTS

Fetoplacental vascular growth is critical to fetal growth. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are two major regulators of fetoplacental vascular growth. G protein α subunit 11 (GNA11) transmits signals from many external stimuli to the cellular interior and may mediate endothelial function. It is not known whether GNA11 mediates FGF2- and VEGFA-induced endothelial cell responses under physiological chronic low O2 . In the present study, we show that knockdown of GNA11 significantly decreases FGF2- and VEGFA-induced fetoplacental endothelial cell migration but not proliferation and permeability. Such decreases in endothelial migration are associated with increased phosphorylation of phospholipase C-β3. The results of the present study suggest differential roles of GNA11 with respect to mediating FGF2- and VEGFA-induced fetoplacental endothelial function.

ABSTRACT

During pregnancy, fetoplacental angiogenesis is dramatically increased in association with rapidly elevated blood flow. Any disruption of fetoplacental angiogenesis may lead to pregnancy complications such as intrauterine growth restriction. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are crucial regulators of fetoplacental angiogenesis. G protein α subunits q (GNAq) and 11 (GNA11) are two members of the Gαq/11 subfamily involved in mediating vascular growth and basal blood pressure. However, little is known about the roles of GNA11 alone with respect to mediating the FGF2- and VEGFA-induced fetoplacental endothelial function. Using a cell model of human umbilical cord vein endothelial cells cultured under physiological chronic low O2 (3% O2 ), we showed that GNA11 small interfering RNA (siRNA) dramatically inhibited (P < 0.05) FGF2- and VEGFA-stimulated fetoplacental endothelial migration (by ∼36% and ∼50%, respectively) but not proliferation and permeability. GNA11 siRNA also elevated (P < 0.05) FGF2- and VEGFA-induced phosphorylation of phospholipase C-β3 (PLCβ3) at S537 in a time-dependent fashion but not mitogen-activated protein kinase 3/1 (ERK1/2) and v-akt murine thymoma viral oncogene homologue 1 (AKT1). These data suggest that GNA11 mediates FGF2- and VEGFA-stimulated fetoplacental endothelial cell migration partially via altering the activation of PLCβ3.

Effect of cell-phone radiofrequency on angiogenesis and cell invasion in human head and neck cancer cells

BACKGROUND

Today, the cell phone is the most widespread technology globally. However, the outcome of cell-phone radiofrequency on head and neck cancer progression has not yet been explored.

METHODS

The chorioallantoic membrane (CAM) and human head and neck cancer cell lines, FaDu and SCC25, were used to explore the outcome of cell-phone radiofrequency on angiogenesis, cell invasion, and colony formation of head and neck cancer cells, respectively. Western blot analysis was used to investigate the impact of the cell phone on the regulation of E-cadherin and Erk1/Erk2 genes.

RESULTS

Our data revealed that cell-phone radiofrequency promotes angiogenesis of the CAM. In addition, the cell phone enhances cell invasion and colony formation of human head and neck cancer cells; this is accompanied by a downregulation of E-cadherin expression. More significantly, we found that the cell phone can activate Erk1/Erk2 in our experimental models.

CONCLUSION

Our investigation reveals that cell-phone radiofrequency could enhance head and neck cancer by stimulating angiogenesis and cell invasion via Erk1/Erk2 activation.

ITE Suppresses Angiogenic Responses in Human Artery and Vein Endothelial Cells: Differential Roles of AhR

Aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor is involved in regulation of many essential biological processes including vascular development and angiogenesis. 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) is an AhR ligand, which regulates immune responses and cancer cell growth. However, the roles of the ITE/AhR pathway in mediating placental angiogenesis remains elusive. Here, we determined if ITE affected placental angiogenic responses via AhR in human umbilical vein (HUVECs) and artery endothelial (HUAECs) cells in vitro. We observed that ITE dose- and time-dependently inhibited proliferation and viability of HUAECs and HUVECs, whereas it inhibited migration of HUAECs, but not HUVECs. While AhR siRNA significantly suppressed AhR protein expression in HUVECs and HUAECs, it attenuated the ITE-inhibited angiogenic responses of HUAECs, but not HUVECs. Collectively, ITE suppressed angiogenic responses of HUAECs and HUVECs, dependent and independent of AhR, respectively. These data suggest that ITE may regulate placental angiogenesis.

Preeclampsia Downregulates MicroRNAs in Fetal Endothelial Cells: Roles of miR-29a/c-3p in Endothelial Function

CONTEXT

Preeclampsia is a leading cause of fetal and maternal morbidity and mortality during pregnancy. Although the etiology of preeclampsia is unknown, preeclampsia offspring have increased risks of developing cardiovascular disorders in adulthood, implicating that preeclampsia programs fetal vasculature in utero.

OBJECTIVE

We hypothesize that preeclampsia alters expression profiles of endothelial microRNAs (miRNAs) in fetal endothelial cells and disturbs the vascular endothelial growth factor A (VEGFA)- and fibroblast growth factor 2 (FGF2)-induced endothelial function.

DESIGN AND SETTING

Unpassaged (P0) human umbilical vein endothelial cells (HUVECs) were isolated immediately after cesarean-section delivery from normotensive (NT) and preeclamptic (PE) pregnancies. Differentially expressed miRNAs between P0-HUVECs from NT and PE pregnancies were identified using a miRNA polymerase chain reaction (PCR) array and confirmed using reverse transcription quantitative PCR. To determine the function of these differentially expressed miRNAs, miRNAs of interest were knocked down in NT-HUVECs following by cell functional assays.

RESULTS

Sixteen miRNAs, including miR-29a/c-3p, were downregulated in P0-HUVECs from the PE group compared with the NT group. Bioinformatics analysis predicted the PI3K-v-akt murine thymoma viral oncogene homolog 1 (AKT) signaling pathway was dysregulated in P0-HUVECs from the PE group, which was associated with the miR-29a/c-3p downregulation. We further demonstrated that miR-29a/c-3p knockdown inhibited the VEGFA- and FGF2-induced endothelial migration as well as FGF2-induced AKT1 phosphorylation in HUVECs. However, miR-29a/c-3p knockdown did not alter the extracellular signal-regulated kinase 1/2 phosphorylation, cell proliferation, and endothelial monolayer integrity in response to VEGFA and FGF2 in HUVECs.

CONCLUSIONS

Preeclampsia-downregulated miR-29a/c-3p may impair fetal endothelial function by disturbing the FGF2-activated PI3K-AKT signaling pathway, hence inhibiting endothelial cell migration.

Elevated NF-κB signaling in Asherman syndrome patients and animal models

Asherman syndrome (intrauterine adhesion) is often associated with menstrual abnormalities, infertility and recurrent miscarriage in female. Currently the molecular mechanism regulating the pathogenesis of Asherman syndrome is not known. Here we revealed that the inflammatory factor NF-κB expression is significantly elevated in the endometrial samples of Asherman syndrome patients. To further study the molecular mechanisms, we established an Asherman syndrome rat model and confirmed the important role of NF-κB in the pathogenesis of Asherman syndrome. In addition, our rat model provided direct evidence that intrauterine adhesion results in impaired pregnancy, supporting the clinical association between intrauterine adhesion and mis-regulated pregnancy. Our result identified NF-κB as a novel pathogenesis factor of Asherman syndrome and provided new insights for the prevention and treatment of intrauterine adhesions in Asherman syndrome patients.

Serum Osteoprotegerin Is a Potential Biomarker of Insulin Resistance in Chinese Postmenopausal Women with Prediabetes and Type 2 Diabetes

The aim of this study is to investigate the circulating OPG levels in postmenopausal women with diabetes and prediabetes and explore the relationships between serum OPG and insulin resistance. A total of 271 unrelated Chinese postmenopausal women were recruited in this study. The subjects were divided into type 2 diabetes mellitus (T2DM) group (n = 93), impaired glucose regulation (IGR) (n = 90), and normal glucose regulation group (NGR) (n = 88), according to different glucose regulation categories. Serum OPG levels were measured by enzyme-linked immunosorbent assay. The serum OPG concentration in NGR group, 151.00 ± 45.72 pg/mL, was significantly lower than that in IGR group (169.28 ± 64.91 pg/mL) (p = 0.031) and T2DM group (183.20 ± 56.53 pg/mL) (p < 0.01), respectively. In multiple linear regression analysis, HOMA-IR, age, 2hPG, AST, ALP, and eGFR were found to be independent predictors of OPG. Increased serum OPG levels (OR = 1.009, p = 0.006) may be a risk factor for insulin resistance. The present study suggests that OPG might be implicated in the pathogenesis of diabetes and is a potential biomarker of insulin resistance in subjects with diabetes and prediabetes.

Role of Mir-155 in Controlling HIF-1α Level and Promoting Endothelial Cell Maturation

Stem-cell-based therapy for cardiovascular disease, especially ischemic heart disease (IHD), is a promising approach to facilitating neovascularization through the migration of stem cells to the ischemic site and their subsequent differentiation into endothelial cells (ECs). Hypoxia is a chief feature of IHD and the stem cell niche. However, whether hypoxia promotes stem cell differentiation into ECs or causes them to retain their stemness is controversial. Here, the differentiation of pluripotent stem cells (iPSCs) into endothelial cells (ECs) was induced under hypoxia. Though the angiogenic capability and angiogenesis-related autocrine/paracrine factors of the ECs were improved under hypoxia, the level of hypoxia inducible factor 1α (HIF-1α) was nonetheless found to be restricted along with the EC differentiation. The down-regulation of HIF-1α was found to have been caused by VEGF-induced microRNA-155 (miR-155). Moreover, miR-155 was also found to enhance the angiogenic capability of induced ECs by targeting E2F2 transcription factor. Hence, miR-155 not only contributes to controlling HIF-1α expression under hypoxia but also promotes angiogenesis, which is a key feature of mature ECs. Revealing the real role of hypoxia and clarifying the function of miR-155 in EC differentiation may facilitate improvement of angiogenic gene- and stem-cell-based therapies for ischemic heart disease.

Bach1 differentially regulates distinct Nrf2-dependent genes in human venous and coronary artery endothelial cells adapted to physiological oxygen levels

The effects of physiological oxygen tension on Nuclear Factor-E2-Related Factor 2 (Nrf2)-regulated redox signaling remain poorly understood. We report the first study of Nrf2-regulated signaling in human primary endothelial cells (EC) adapted long-term to physiological O2 (5%). Adaptation of EC to 5% O2 had minimal effects on cell ultrastructure, viability, basal redox status or HIF1-α expression. Affymetrix array profiling and subsequent qPCR/protein validation revealed that induction of select Nrf2 target genes, HO-1 and NQO1, was significantly attenuated in cells adapted to 5% O2, despite nuclear accumulation and DNA binding of Nrf2. Diminished HO-1 induction under 5% O2 was stimulus independent and reversible upon re-adaptation to air or silencing of the Nrf2 repressor Bach1, notably elevated under 5% O2. Induction of GSH-related genes xCT and GCLM were oxygen and Bach1-insensitive during long-term culture under 5% O2, providing the first evidence that genes related to GSH synthesis mediate protection afforded by Nrf2-Keap1 defense pathway in cells adapted to physiological O2 levels encountered in vivo.

2,3,7,8-Tetrachlorodibenzo-p-dioxin differentially suppresses angiogenic responses in human placental vein and artery endothelial cells

Placental angiogenesis is dramatically increased during pregnancy in association with the elevated placental blood flows to support the rapidly growing fetus. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental toxicant and a ligand of aryl hydrocarbon receptor (AhR). Herein, we investigated the effects of TCDD on proliferation, migration, and viability of fetoplacental endothelial cells in response to a complete growth medium which contained serum and growth supplement using human umbilical cord vein (HUVECs) and artery (HUAECs) cells as models. We found that TCDD dose- and time-dependently inhibited (p < 0.05) proliferation of HUVECs and HUAECs. Treatment with TCDD at 10 nM for 6 days inhibited (p < 0.05) migration (by ∼ 30%) of HUAECs, but not HUVECs. TCDD at 10nM also decreased (p < 0.05) viability of HUVECs and HUAECs. Interestingly, specific AhR siRNA blocked (p < 0.05) the TCDD-inhibited cellular responses in HUAECs, but not HUVECs. Nonetheless, TCDD at 10nM neither affected the cell cycle progression, nor did it induce cell apoptosis in HUVECs and HUAECs. In addition, TCDD at 10 nM also did not alter activation of ERK1/2 and AKT1 in HUVECs and HUAECs. Collectively, TCDD suppresses proliferation and/or migration (two key steps of angiogenesis) of HUVECs and HUAECs independent and dependent of AhR, respectively. These data suggest that TCDD inhibited growth of HUVECs and HUAECs via decreasing cell viability. Thus, TCDD may inhibit fetoplacental angiogenesis, leading to negative pregnancy outcomes.

Preeclampsia does not alter vascular growth and expression of CD31 and vascular endothelial cadherin in human placentas

Preeclampsia is characterized by maternal endothelial dysfunction (e.g., increased maternal vascular permeability caused by the disassembly of endothelial junction proteins). However, it is unclear if preeclampsia is associated with impaired vascular growth and expression of endothelial junction proteins in human placentas. Herein, we examined vascular growth in placentas from women with normal term (NT) and preeclamptic (PE) pregnancies using two endothelial junction proteins as endothelial markers: CD31 and vascular endothelial-cadherin (VE-Cad). We also compared protein and mRNA expression of CD31 and VE-Cad between NT and PE placentas, and determined the alternatively spliced expression of CD31 using PCR. We found that CD31 and VE-Cad were immunolocalized predominantly in villous endothelial cells. However, capillary number density (total capillary number per unit villous area) and capillary area density (total capillary lumen area per unit villous area) as well as CD31 and VE-Cad protein and mRNA levels were similar between NT and PE placentas. PCR in combination with sequence analysis revealed a single, full-length CD31, suggesting that there are no alternatively spliced isoform of CD31 expressed in placentas. These data indicate that preeclampsia does not significantly affect vascular growth or the expression of endothelial junction proteins in human placentas.

Distinct roles of HIF1A in endothelial adaptations to physiological and ambient oxygen

Fetoplacental endothelial cells reside under physiological normoxic conditions (∼2-8% O2) in vivo. Under such conditions, cells are believed to sense O2 changes primarily via hypoxia inducible factor 1 α (HIF1A). However, little is known regarding the role of HIF1A in fetoplacental endothelial function under physiological normoxia. We recently reported that physiological chronic normoxia (PCN; 20-25 day, 3% O2) enhanced FGF2- and VEGFA-stimulated proliferation and migration of human umbilical vein endothelial cells (HUVECs) via the MEK/ERK1/2 and PI3K/AKT1 pathways compared to standard cell culture normoxia (SCN; ambient O2: ∼21% O2). Here, we investigated the action of HIF1A in regulating these cellular responses in HUVECs. HIF1A adenovirus infection in SCN-cells increased HIF1A protein expression, enhanced FGF2- and VEGFA-stimulated cell proliferation by 2.4 and 2.0-fold respectively, and promoted VEGFA-stimulated cell migration by 1.4-fold. HIF1A adenovirus infection in SCN-cells did not affect either basal or FGF2- and VEGFA-induced ERK1/2 activation, but it decreased basal AKT1 phosphorylation. Interestingly, HIF1A knockdown in PCN-cells via specific HIF1A siRNA transfection did not alter FGF2- and VEGFA-stimulated cell proliferation and migration, or ERK1/2 activation; however, it inhibited FGF2-induced AKT1 activation by ∼50%. These data indicate that HIF1A differentially regulates cell proliferation and migration, and ERK1/2 and AKT1 activation in PCN- and SCN-HUVECs. These data also suggest that HIF1A critically regulates cell proliferation and migration in SCN-, but not in PCN-HUVECs.

Expression of G-protein subunit α-14 is increased in human placentas from preeclamptic pregnancies

G-proteins mediate cellular function upon interaction with G-protein coupled receptors. Of the 16 mammalian G-protein α subunits identified, G-protein subunit α-11 (GNA11) and -14 (GNA14) have been implicated in modulating hypertension and endothelial function. However, little is known about their expression and roles in human placentas. Here, we examined GNA11 and GNA14 protein expression in first trimester (FT), normal term (NT), and severe preeclamptic (sPE) human placentas as well as in NT human umbilical cords. We found that GNA11 and GNA14 were immunolocalized primarily in trophoblasts, villous stromal cells, and endothelial cells in placentas as well as in endothelial and/or smooth muscle cells of the umbilical cord artery and vein. Western blotting revealed that the GNA14, but not GNA11, protein levels were increased (2.5-2.9 fold; p<0.01) in sPE vs. NT placentas. GNA11 protein was detected only in NT, but not FT, placentas, whereas GNA14 protein levels were increased (7.7-10.6 fold; p<0.01) in NT vs. FT placentas. Thus, GNA11 and GNA14 may mediate the function of several cell types in placentas. Moreover, the high expression of GNA14 in sPE placentas may also imply its importance in sPE pregnancies as in the other hypertension-related disorders.

Enhanced cellular responses and distinct gene profiles in human fetoplacental artery endothelial cells under chronic low oxygen

Fetoplacental endothelial cells are exposed to oxygen levels ranging from 2% to 8% in vivo. However, little is known regarding endothelial function within this range of oxygen because most laboratories use ambient air (21% O2) as a standard culture condition (SCN). We asked whether human umbilical artery endothelial cells (HUAECs) that were steadily exposed to the physiological chronic normoxia (PCN, 3% O2) for ∼20-25 days differed in their proliferative and migratory responses to FGF2 and VEGFA as well as in their global gene expression compared with those in the SCN. We observed that PCN enhanced FGF2- and VEGFA-stimulated cell proliferation and migration. In oxygen reversal experiments (i.e., when PCN cells were exposed to SCN for 24 h and vice versa), we found that preexposure to 21% O2 decreased the migratory ability, but not the proliferative ability, of the PCN-HUAECs in response to FGF2 and VEGFA. These PCN-enhanced cellular responses were associated with increased protein levels of HIF1A and NOS3, but not FGFR1, VEGFR1, and VEGFR2. Microarray analysis demonstrated that PCN up-regulated 74 genes and down-regulated 86, 14 of which were directly regulated by hypoxia-inducible factors as evaluated using in silico analysis. Gene function analysis further indicated that the PCN-regulated genes were highly related to cell proliferation and migration, consistent with the results from our functional assays. Given that PCN significantly alters cellular responses to FGF2 and VEGFA as well as transcription in HUAECs, it is likely that we may need to reexamine the current cellular and molecular mechanisms controlling fetoplacental endothelial functions, which were largely derived from endothelial models established under ambient O2.