A requirement for Krüppel Like Factor-4 in the maintenance of endothelial cell quiescence.

Endothelial cells (ECs) are quiescent and critical for maintaining homeostatic functions of the mature vascular system, while disruption of quiescence is at the heart of endothelial to mesenchymal transition (EndMT) and tumor angiogenesis. Here, we addressed the hypothesis that KLF4 maintains the EC quiescence. In ECs, KLF4 bound to KLF2, and the KLF4-transctivation domain (TAD) interacted directly with KLF2.

TIRAP in the Mechanism of Inflammation.

The Toll-interleukin-1 Receptor (TIR) domain-containing adaptor protein (TIRAP) represents a key intracellular signalling molecule regulating diverse immune responses. Its capacity to function as an adaptor molecule has been widely investigated in relation to Toll-like Receptor (TLR)-mediated innate immune signalling. Since the discovery of TIRAP in 2001, initial studies were mainly focused on its role as an adaptor protein that couples Myeloid differentiation factor 88 (MyD88) with TLRs, to activate MyD88-dependent TLRs signalling.

Low-Level Nanog Expression in the Regulation of Quiescent Endothelium.

Objective: Nanog is expressed in adult endothelial cells (ECs) at a low-level, however, its functional significance is not known. The goal of our study was to elucidate the role of Nanog in adult ECs using a genetically engineered mouse model system. Approach and Results: Biochemical analyses showed that Nanog is expressed in both adult human and mouse tissues.

Tumor-derived exosomes in the regulation of macrophage polarization.

Background: This review focuses on exosomes derived from various cancer cells. The review discusses the possibility of differentiating macrophages in alternatively activated anti-inflammatory pro-tumorigenic M2 macrophage phenotypes and classically activated pro-inflammatory, anti-tumorigenic M1 macrophage phenotypes in the tumor microenvironment (TME). The review is divided into two main parts, as follows: (1) role of exosomes in alternatively activating M2-like macrophages-breast cancer-derived exosomes, hepatocellular carcinoma (HCC) cell-derived exosomes, lung cancer-derived exosomes, prostate cancer-derived exosomes, Oral squamous cell carcinoma (OSCC)-derived exosomes, epithelial ovarian cancer (EOC)-derived exosomes, Glioblastoma (GBM) cell-derived exosomes, and colorectal cancer-derived exosomes, (2) role of exosomes in classically activating M1-like macrophages, oral squamous cell carcinoma-derived exosomes, breast cancer-derived exosomes, Pancreatic-cancer derived modified exosomes, and colorectal cancer-derived exosomes, and (3) exosomes and antibody-dependent cellular cytotoxicity (ADCC).

Exosomes in the Regulation of Vascular Endothelial Cell Regeneration.

Exosomes have been described as nanoscale membranous extracellular vesicles that emerge from a variety of cells and tissues and are enriched with biologically active genomic and non-genomic biomolecules capable of transducing cell to cell communication. Exosome release, and exosome mediated signaling and cross-talks have been reported in several pathophysiological states. Therefore, exosomes have the potential to become suitable for the diagnosis, prognosis and treatment of specific diseases, including endothelial cell (EC) dysfunction and regeneration.

LDL induces cholesterol loading and inhibits endothelial proliferation and angiogenesis in Matrigels: correlation with impaired angiogenesis during wound healing.

Hypercholesterolemia is a major risk factor for adverse cardiovascular outcomes, but its effect on angiogenesis and wound healing is not well understood. In this study, using a combination of mass spectrometry and laurdan two-photon imaging, we show that elevated levels of low-density lipoprotein (LDL), like those seen in hypercholesterolemic patients, lead to an increase in both free cholesterol and cholesterol esters, as well as increase in lipid order of endothelial cell membranes. Notably, these effects are distinct and opposite to the lack of cholesterol loading and the disruption of lipid order observed in our earlier studies in response to oxidized LDL (oxLDL).

Sphingosine-1-Phosphate Receptor 1 Activity Promotes Tumor Growth by Amplifying VEGF-VEGFR2 Angiogenic Signaling.

The vascular endothelial growth factor-A (VEGF-A)-VEGFR2 pathway drives tumor vascularization by activating proangiogenic signaling in endothelial cells (ECs). Here, we show that EC-sphingosine-1-phosphate receptor 1 (S1PR1) amplifies VEGFR2-mediated angiogenic signaling to enhance tumor growth. We show that cancer cells induce S1PR1 activity in ECs, and thereby, conditional deletion of S1PR1 in ECs (EC-S1pr1 mice) impairs tumor vascularization and growth.

oxLDL induces endothelial cell proliferation via Rho/ROCK/Akt/p27 signaling: opposite effects of oxLDL and cholesterol loading.

Oxidized modifications of LDL (oxLDL) play a key role in the development of endothelial dysfunction and atherosclerosis. However, the underlying mechanisms of oxLDL-mediated cellular behavior are not completely understood. Here, we compared the effects of two major types of oxLDL, copper-oxidized LDL (Cu-oxLDL) and lipoxygenase-oxidized LDL (LPO-oxLDL), on proliferation of human aortic endothelial cells (HAECs).

Chromatin-modifying agents convert fibroblasts to OCT4+ and VEGFR-2+ capillary tube-forming cells.

Rationale: The human epigenome is plastic. The goal of this study was to address if fibroblast cells can be epigenetically modified to promote neovessel formation.

Methods And Results: Here, we used highly abundant human adult dermal fibroblast cells (hADFCs) that were treated with the chromatin-modifying agents 5-aza-2'-deoxycytidine and trichostatin A, and subsequently subjected to differentiation by activating Wnt signaling.

Endothelial lipid phosphate phosphatase-3 deficiency that disrupts the endothelial barrier function is a modifier of cardiovascular development.

Aims: Lipid phosphate phosphatase-3 (LPP3) is expressed at high levels in endothelial cells (ECs). Although LPP3 is known to hydrolyse the phosphate group from lysolipids such as spingosine-1-phosphate and its structural homologues, the function of Lpp3 in ECs is not completely understood. In this study, we investigated how tyrosine-protein kinase receptor (TEK or Tie2) promoter-dependent deletion of Lpp3 alters EC activities.

Oxidized LDL signals through Rho-GTPase to induce endothelial cell stiffening and promote capillary formation.

Endothelial biomechanics is emerging as a key factor in endothelial function. Here, we address the mechanisms of endothelial stiffening induced by oxidized LDL (oxLDL) and investigate the role of oxLDL in lumen formation. We show that oxLDL-induced endothelial stiffening is mediated by CD36-dependent activation of RhoA and its downstream target, Rho kinase (ROCK), via inhibition of myosin light-chain phosphatase (MLCP) and myosin light-chain (MLC)2 phosphorylation.

Histone Demethylases KDM4A and KDM4C Regulate Differentiation of Embryonic Stem Cells to Endothelial Cells.

Understanding epigenetic mechanisms regulating embryonic stem cell (ESC) differentiation to endothelial cells may lead to increased efficiency of generation of vessel wall endothelial cells needed for vascular engineering. Here we demonstrated that the histone demethylases KDM4A and KDM4C played an indispensable but independent role in mediating the expression of fetal liver kinase (Flk)1 and VE-cadherin, respectively, and thereby the transition of mouse ESCs (mESCs) to endothelial cells. KDM4A was shown to bind to histones associated with the Flk1 promoter and KDM4C to bind to histones associated with the VE-cadherin promoter.

Integrin α6β1 Expressed in ESCs Instructs the Differentiation to Endothelial Cells.

Adhesion of embryonic stem cells (ESCs) to the extracellular matrix may influence differentiation potential and cell fate decisions. Here, we investigated the inductive role of binding of integrin α6β1 expressed in mouse (m)ESCs to laminin-1 (LN1) in mediating the differentiation of ESCs to endothelial cells (ECs). We observed that α6β1 binding to LN1 was required for differentiation to ECs.

Induced Pluripotent Stem (iPS) Cell Culture Methods and Induction of Differentiation into Endothelial Cells.

The study of stem cell behavior and differentiation in a developmental context is complex, time-consuming, and expensive, and for this reason, cell culture remains a method of choice for developmental and regenerative biology and mechanistic studies. Similar to ES cells, iPS cells have the ability to differentiate into endothelial cells (ECs), and the route for differentiation appears to mimic the developmental process that occurs during the formation of an embryo. Traditional EC induction methods from embryonic stem (ES) cells rely mostly on the formation of embryoid body (EB), which employs feeder or feeder-free conditions in the presence or absence of supporting cells.

KIF13B regulates angiogenesis through Golgi to plasma membrane trafficking of VEGFR2.

Although the trafficking of newly synthesized VEGFR2 to the plasma membrane is a key determinant of angiogenesis, the molecular mechanisms of Golgi to plasma membrane trafficking are unknown. Here, we have identified a key role of the kinesin family plus-end molecular motor KIF13B in delivering VEGFR2 cargo from the Golgi to the endothelial cell surface. KIF13B is shown to interact directly with VEGFR2 on microtubules.

Role of c-Met/phosphatidylinositol 3-kinase (PI3k)/Akt signaling in hepatocyte growth factor (HGF)-mediated lamellipodia formation, reactive oxygen species (ROS) generation, and motility of lung endothelial cells.

Hepatocyte growth factor (HGF) mediated signaling promotes cell proliferation and migration in a variety of cell types and plays a key role in tumorigenesis. As cell migration is important to angiogenesis, we characterized HGF-mediated effects on the formation of lamellipodia, a pre-requisite for migration using human lung microvascular endothelial cells (HLMVECs). HGF, in a dose-dependent manner, induced c-Met phosphorylation (Tyr-1234/1235, Tyr-1349, Ser-985, Tyr-1003, and Tyr-1313), activation of PI3k (phospho-Yp85) and Akt (phospho-Thr-308 and phospho-Ser-473) and potentiated lamellipodia formation and HLMVEC migration.

Low-dose 6-bromoindirubin-3'-oxime induces partial dedifferentiation of endothelial cells to promote increased neovascularization.

Endothelial cell (EC) dedifferentiation in relation to neovascularization is a poorly understood process. In this report, we addressed the role of Wnt signaling in the mechanisms of neovascularization in adult tissues. Here, we show that a low-dose of 6-bromoindirubin-3'-oxime (BIO), a competitive inhibitor of glycogen synthase kinase-3β, induced the stabilization of β-catenin and its subsequent direct interaction with the transcription factor NANOG in the nucleus of ECs.

Flk1+ and VE-cadherin+ endothelial cells derived from iPSCs recapitulates vascular development during differentiation and display similar angiogenic potential as ESC-derived cells.

Rationale: Induced pluripotent stem (iPS) cells have emerged as a source of potentially unlimited supply of autologous endothelial cells (ECs) for vascularization. However, the regenerative function of these cells relative to adult ECs and ECs derived from embryonic stem (ES) cells is unknown. The objective was to define the differentiation characteristics and vascularization potential of Fetal liver kinase (Flk)1(+) and Vascular Endothelial (VE)-cadherin(+) ECs derived identically from mouse (m)ES and miPS cells.

Endothelial invasive response in a co-culture model with physically-induced osteodifferentiation.

Manipulation of stem cells using physicochemical stimuli has emerged as an important tool in regenerative medicine. While 2D substrates with tunable elasticity have been studied for control of stem cell differentiation, we recently developed a stratified co-culture model of angiogenesis of human mesenchymal stem cells (hMSCs) that differentiate on a tunable polydimethylsiloxane (PDMS) substrate, thereby creating a physiologic context for elasticity-induced differentiation. Endothelial cells (EC) were cultured on top of the hMSC construct on a collagen gel to monitor network formation.

Focal adhesion kinase regulation of neovascularization.

In this review, we discuss the role of focal adhesion kinase (FAK), an intracellular tyrosine kinase, in endothelial cells in relation to neovascularization. Genetic and in vitro studies have identified critical factors, receptor systems, and their intracellular signaling components that regulate the neovasculogenic phenotypes of endothelial cells. Among these factors, FAK appears to regulate several aspects of endothelial cellular behavior, including migration, survival, cytoskeletal organization, as well as cell proliferation.

Lipid phosphate phosphatase-3 regulates tumor growth via β-catenin and CYCLIN-D1 signaling.

Background: The acquisition of proliferative and invasive phenotypes is considered a hallmark of neoplastic transformation; however, the underlying mechanisms are less well known. Lipid phosphate phosphatase-3 (LPP3) not only catalyzes the dephosphorylation of the bioactive lipid sphingosine-1-phosphate (S1P) to generate sphingosine but also may regulate embryonic development and angiogenesis via the Wnt pathway. The goal of this study was to determine the role of LPP3 in tumor cells.

NANOG induction of fetal liver kinase-1 (FLK1) transcription regulates endothelial cell proliferation and angiogenesis.

NANOG is a master transcription factor associated with the maintenance of stem cell pluripotency. Here, we demonstrate that transcription factor NANOG is expressed in cultured endothelial cells (ECs) and in a subset of tumor cell lines. Importantly, we provide evidence that WNT3A stimulation of ECs induces the transcription of NANOG which mediates the expression of vascular endothelial growth factor receptor-2, also known as fetal liver kinase-1 (FLK1).