The use of human pluripotent stem cells for in vitro disease modelling and clinical applications requires protocols that convert these cells into relevant adult cell types. Here, we report the rapid ...and efficient differentiation of human pluripotent stem cells into vascular endothelial and smooth muscle cells. We found that GSK3 inhibition and BMP4 treatment rapidly committed pluripotent cells to a mesodermal fate and subsequent exposure to VEGF-A or PDGF-BB resulted in the differentiation of either endothelial or vascular smooth muscle cells, respectively. Both protocols produced mature cells with efficiencies exceeding 80% within six days. On purification to 99% via surface markers, endothelial cells maintained their identity, as assessed by marker gene expression, and showed relevant in vitro and in vivo functionality. Global transcriptional and metabolomic analyses confirmed that the cells closely resembled their in vivo counterparts. Our results suggest that these cells could be used to faithfully model human disease.
Highly malignant tumors, such as glioblastomas, are characterized by hypoxia, endothelial cell (EC) hyperplasia, and hypercoagulation. However, how these phenomena of the tumor microenvironment may ...be linked at the molecular level during tumor development remains ill-defined. Here, we provide evidence that hypoxia up-regulates protease-activated receptor 2 (PAR-2), i.e., a G-protein–coupled receptor of coagulation-dependent signaling, in ECs. Hypoxic induction of PAR-2 was found to elicit an angiogenic EC phenotype and to specifically up-regulate heparin-binding EGF-like growth factor (HB-EGF). Inhibition of HB-EGF by antibody neutralization or heparin treatment efficiently counteracted PAR-2–mediated activation of hypoxic ECs. We show that PAR-2–dependent HB-EGF induction was associated with increased phosphorylation of ERK1/2, and inhibition of ERK1/2 phosphorylation attenuated PAR-2–dependent HB-EGF induction as well as EC activation. Tissue factor (TF), i.e., the major initiator of coagulation-dependent PAR signaling, was substantially induced by hypoxia in several types of cancer cells, including glioblastoma; however, TF was undetectable in ECs even at prolonged hypoxia, which precludes cell-autonomous PAR-2 activation through TF. Interestingly, hypoxic cancer cells were shown to release substantial amounts of TF that was mainly associated with secreted microvesicles with exosome-like characteristics. Vesicles derived from glioblastoma cells were found to trigger TF/VIIa–dependent activation of hypoxic ECs in a paracrine manner. We provide evidence of a hypoxia-induced signaling axis that links coagulation activation in cancer cells to PAR-2–mediated activation of ECs. The identified pathway may constitute an interesting target for the development of additional strategies to treat aggressive brain tumors.
Gamma aminobutyric acid (GABA), a neurotransmitter of the central nervous system, is found in the systemic circulation of humans at a concentration between 0.5 and 3 μmol/L. However, the potential ...source of circulating GABA and its significance on the vascular system remains unknown. We hypothesized that endothelial cells (ECs) may synthesize and release GABA to modulate some functions in the EC and after its release into the circulation.
To assess whether GABA is synthesized and released by the EC and its potential functions.
Utilizing the human umbilical vein ECs and aortic ECs, we demonstrated for the first time that ECs synthesize and release GABA from 1-(14)Cglutamate. Localization of GABA and the presence of the GABA-synthesizing enzyme, glutamic acid decarboxylase in EC were confirmed by immunostaining and immunoblot analysis, respectively. The presence of GABA was further confirmed by immunohistochemistry in the EC lining the human coronary vessel. EC-derived GABA regulated the key mechanisms of ATP synthesis, fatty acid, and pyruvate oxidation in EC. GABA protected EC by inhibiting the reactive oxygen species generation and prevented monocyte adhesion by attenuating vascular cell adhesion molecule -1 and monocyte chemoattractant protein-1 expressions. GABA had no relaxing effect on rat aortic rings. GABA exhibited a dose-dependent fall in blood pressure. However, the fall in BP was abolished after pretreatment with pentolinium.
Our findings indicate novel potential functions of endothelium-derived GABA.
Histone H3 lysine‐9 di‐methylation (H3K9me2) and lysine‐27 tri‐methylation (H3K27me3) are linked to repression of gene expression, but the functions of repressive histone methylation dynamics during ...inflammatory responses remain enigmatic. Here, we report that lysine demethylases 7A (KDM7A) and 6A (UTX) play crucial roles in tumor necrosis factor (TNF)‐α signaling in endothelial cells (ECs), where they are regulated by a novel TNF‐α‐responsive microRNA, miR‐3679‐5p. TNF‐α rapidly induces co‐occupancy of KDM7A and UTX at nuclear factor kappa‐B (NF‐κB)‐associated elements in human ECs. KDM7A and UTX demethylate H3K9me2 and H3K27me3, respectively, and are both required for activation of NF‐κB‐dependent inflammatory genes. Chromosome conformation capture‐based methods furthermore uncover increased interactions between TNF‐α‐induced super enhancers at NF‐κB‐relevant loci, coinciding with KDM7A and UTX recruitments. Simultaneous pharmacological inhibition of KDM7A and UTX significantly reduces leukocyte adhesion in mice, establishing the biological and potential translational relevance of this mechanism. Collectively, these findings suggest that rapid erasure of repressive histone marks by KDM7A and UTX is essential for NF‐κB‐dependent regulation of genes that control inflammatory responses of ECs.
Synopsis
Comprehensive analysis of epigenetic responses during early inflammation in endothelial cells reveals that lysine demethylase 7A and 6A act cooperatively to rapidly erase repressive histone marks, which is required for activation of the pro‐inflammatory TNF‐α/NF‐κB‐signaling pathway.
Lysine demethylase 7A (KDM7A) and 6A (UTX) cooperatively control NF‐κB‐dependent transcription in mammalian vascular endothelial cells.
Demethylation of repressive histone marks by KDM7A and UTX is critical for early inflammatory responses.
KDM7A and UTX are associated with TNF‐α‐induced chromatin looping of super enhancers.
Pharmacological inhibition of KDM7A and UTX reduces leucocyte adhesive interactions with endothelial cells in mice.
Comprehensive analysis of epigenetic responses suggests that rapid erasure of repressive histone marks by KDM7A and UTX is essential for NF‐κB‐dependent inflammatory gene regulation.
The blood–retina barrier and blood–brain barrier (BRB/BBB) are selective and semipermeable and are critical for supporting and protecting central nervous system (CNS)-resident cells. Endothelial ...cells (ECs) within the BRB/BBB are tightly coupled, express high levels of Claudin-5 (CLDN5), a junctional protein that stabilizes ECs, and are important for proper neuronal function. To identify novel CLDN5 regulators (and ultimately EC stabilizers), we generated a CLDN5-P2A-GFP stable cell line from human pluripotent stem cells (hPSCs), directed their differentiation to ECs (CLDN5-GFP hPSC-ECs), and performed flow cytometry-based chemogenomic library screening to measure GFP expression as a surrogate reporter of barrier integrity. Using this approach, we identified 62 unique compounds that activated CLDN5-GFP. Among them were TGF-β pathway inhibitors, including RepSox. When applied to hPSC-ECs, primary brain ECs, and retinal ECs, RepSox strongly elevated barrier resistance (transendothelial electrical resistance), reduced paracellular permeability (fluorescein isothiocyanate-dextran), and prevented vascular endothelial growth factor A (VEGFA)-induced barrier breakdown in vitro. RepSox also altered vascular patterning in themouse retina during developmentwhen delivered exogenously. To determine the mechanism of action of RepSox, we performed kinome-, transcriptome-, and proteome-profiling and discovered that RepSox inhibited TGF-β, VEGFA, and inflammatory gene networks. In addition, RepSox not only activated vascular-stabilizing and barrier-establishing Notch and Wnt pathways, but also induced expression of important tight junctions and transporters. Taken together, our data suggest that inhibitingmultiple pathways by selected individual small molecules, such as RepSox, may be an effective strategy for the development of better BRB/BBB models and novel EC barrier-inducing therapeutics.
We hypothesized that in glioblastoma recurring after radiotherapy, a condition whereby the brain endothelium undergoes radiation-induced senescence, tumor cells with endothelial phenotype may be ...relevant for tumor neovascularization. Matched glioblastoma samples obtained at primary surgery and at surgery for tumor recurrence after radiotherapy, all expressing epidermal growth factor receptor variant III (EGFRvIII), were assessed by a technique that combines fluorescent in situ hybridization (FISH) for the EGFR/CEP7 chromosomal probe with immunostaining for endothelial cells (CD31) and activated pericytes (α Smooth Muscle Actin). Five EGFRvIII-expressing paired primary/recurrent glioblastoma samples, in which the tumor cells showed EGFR/CEP7 amplification, were then assessed by CD31 and α Smooth Muscle Actin immunofluorescence. In glomeruloid bodies, the ratio between CD31+ cells with amplified EGFR/CEP7 signal and the total CD31+ cells was 0.23 ± 0.09 (mean ± sem) and 0.63 ± 0.07 in primary tumors and in recurrent ones, respectively (p < 0.002, Student-t test). In capillaries, the ratio of CD31+ cells with amplified EGFR/CEP7 over the total CD31+ cells lining the capillary lumen was 0.21 ± 0.06 (mean ± sem) and 0.42 ± 0.07 at primary surgery and at recurrence, respectively (p < 0.005, Student-t test). Expression of α Smooth Muscle Actin by cells with EGFR/CEP7 amplification was not observed. Then, in glioblastoma recurring after radiotherapy, where the brain endothelium suffers from radiation-induced cell senescence, tumor-derived endothelium plays a role in neo-vascularization.
The vertebrate vasculature displays high organotypic specialization, with the structure and function of blood vessels catering to the specific needs of each tissue. A unique feature of the central ...nervous system (CNS) vasculature is the blood-brain barrier (BBB). The BBB regulates substance influx and efflux to maintain a homeostatic environment for proper brain function. Here, we review the development and cell biology of the BBB, focusing on the cellular and molecular regulation of barrier formation and the maintenance of the BBB through adulthood. We summarize unique features of CNS endothelial cells and highlight recent progress in and general principles of barrier regulation. Finally, we illustrate why a mechanistic understanding of the development and maintenance of the BBB could provide novel therapeutic opportunities for CNS drug delivery.
Endothelial dysfunction inflicted by inflammation is found in a host of cardiovascular pathologies. One hallmark event in this process is the aggregation and adhesion of leukocyte to the vessel wall ...mediated by the upregulation of adhesion molecules (CAM) in endothelial cells at the transcriptional level. The epigenetic modulator(s) of CAM transactivation and its underlying pathophysiological relevance remain poorly defined.
Our goal was to determine the involvement of Brahma related gene 1 (Brg1) and Brahma (Brm) in CAM transactivation and its relevance in the pathogenesis of atherosclerosis.
In the present study, we report that proinflammatory stimuli augmented the expression of Brg1 and Brm in vitro in cultured endothelial cells and in vivo in arteries isolated from rodents. Overexpression of Brg1 and Brm promoted while knockdown of Brg1 and Brm abrogated transactivation of adhesion molecules and leukocyte adhesion induced by inflammatory signals. Brg1 and Brm interacted with and were recruited to the CAM promoters by nuclear factor κB/p65. Conversely, depletion of Brg1 and Brm disrupted the kinetics of p65 binding on CAM promoters and crippled CAM activation. Silencing of Brg1 and Brm also altered key epigenetic changes associated with CAM transactivation. Of intrigue, 17β-estradiol antagonized both the expression and activity of Brg1/Brm. Most importantly, endothelial-targeted elimination of Brg1/Brm conferred atheroprotective effects to Apoe(-/-) mice on a Western diet.
Our data suggest that Brg1 and Brm integrate various proinflammatory cues into CAM transactivation and endothelial malfunction and, as such, may serve as potential therapeutic targets in treating inflammation-related cardiovascular diseases.
Vascular endothelial (VE)-protein tyrosine phosphatase (PTP) associates with VE-cadherin, thereby supporting its adhesive activity and endothelial junction integrity. VE-PTP also associates with ...Tie-2, dampening the tyrosine kinase activity of this receptor that can support stabilization of endothelial junctions. Here, we have analyzed how interference with VE-PTP affects the stability of endothelial junctions in vivo. Blocking VE-PTP by antibodies, a specific pharmacological inhibitor (AKB-9778), and gene ablation counteracted vascular leak induction by inflammatory mediators. In addition, leukocyte transmigration through the endothelial barrier was attenuated. Interference with Tie-2 expression in vivo reversed junction-stabilizing effects of AKB-9778 into junction-destabilizing effects. Furthermore, lack of Tie-2 was sufficient to weaken the vessel barrier. Mechanistically, inhibition of VE-PTP stabilized endothelial junctions via Tie-2, which triggered activation of Rap1, which then caused the dissolution of radial stress fibers via Rac1 and suppression of nonmuscle myosin II. Remarkably, VE-cadherin gene ablation did not abolish the junction-stabilizing effect of the VE-PTP inhibitor. Collectively, we conclude that inhibition of VE-PTP stabilizes challenged endothelial junctions in vivo via Tie-2 by a VE-cadherin-independent mechanism. In the absence of Tie-2, however, VE-PTP inhibition destabilizes endothelial barrier integrity in agreement with the VE-cadherin-supportive effect of VE-PTP.
The occurrence of new blood vessel formation in the lungs of asthmatic patients suggests a critical role for airway endothelial cells (ECs) in the disease. IL-33 (Interleukin-33)-a cytokine ...abundantly expressed in human lung ECs-recently emerged as a key factor in the development of allergic diseases, including asthma. In the present study, we evaluated whether mouse and human ECs exposed to the common
allergen produce IL-33 and characterized the activated signaling pathways. Approach and Results: Mouse primary lung ECs were exposed in vitro to
extract or rmIL-33 (recombinant murine IL-33). Both
and rmIL-33 induced
transcription without increasing the IL-33 production and upregulated the expression of its receptor, as well as genes involved in angiogenesis and the regulation of immune responses. In particular,
and rmIL-33 upregulated
transcript level, yet without promoting apoptosis. Inhibition of caspases involved in the Fas signaling pathway, increased IL-33 protein level in ECs, suggesting that Fas may decrease IL-33 level through caspase-8-dependent mechanisms. Our data also showed that the NF-κB (nuclear factor-κB), PI3K/Akt, and Wnt/β-catenin pathways regulate
transcription in both mouse and human primary ECs.
Herein, we described a new mechanism involved in the control of IL-33 production in lung ECs exposed to allergens.
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