Functional properties of human vascular endothelial cadherin (7B4/cadherin-5), an endothelium-specific cadherin

Angiogenesis: Biological Mechanisms and In Vitro Models

The translation of biomedical devices and drug research is an expensive and long process with a low probability of receiving FDA approval. Developing physiologically relevant in vitro models with human cells offers a solution to not only improving the odds of FDA approval but also to expand our ability to study complex in vivo systems in a simpler fashion. Animal models remain the standard for pre-clinical testing; however, the data from animal models is an unreliable extrapolation when anticipating a human response in clinical trials, thus contributing to the low rates of translation. In this review, we focus on in vitro vascular or angiogenic models because of the incremental role that the vascular system plays in the translation of biomedical research. The first section of this review discusses the most common angiogenic cytokines that are used in vitro to initiate angiogenesis, followed by angiogenic inhibitors where both initiators and inhibitors work to maintain vascular homeostasis. Next, we evaluate previously published in vitro models, where we evaluate capturing the physical environment for biomimetic in vitro modeling. These topics provide a foundation of parameters that must be considered to improve and achieve vascular biomimicry. Finally, we summarize these topics to suggest a path forward with the goal of engineering human in vitro models that emulate the in vivo environment and provide a platform for biomedical device and drug screening that produces data to support clinical translation.

Novel Role of Endothelial CD45 in Regulating Endothelial-to-Mesenchymal Transition in Atherosclerosis

Background

Protein-tyrosine-phosphatase CD45 is exclusively expressed in all nucleated cells of the hematopoietic system but is rarely expressed in endothelial cells. Interestingly, our recent study indicated that activation of the endogenous CD45 promoter in human endothelial colony forming cells (ECFCs) induced expression of multiple EndoMT marker genes. However, the detailed molecular mechanisms underlying CD45 that drive EndoMT and the therapeutic potential of manipulation of CD45 expression in atherosclerosis are entirely unknown.

Method

We generated a tamoxifen-inducible EC-specific CD45 deficient mouse strain (EC-iCD45KO) in an ApoE-deficient (ApoE-/-) background and fed with a Western diet (C57BL/6) for atherosclerosis and molecular analyses. We isolated and enriched mouse aortic endothelial cells with CD31 beads to perform single-cell RNA sequencing. Biomedical, cellular, and molecular approaches were utilized to investigate the role of endothelial CD45-specific deletion in the prevention of EndoMT in ApoE-/- model of atherosclerosis.

Results

Single-cell RNA sequencing revealed that loss of endothelial CD45 inhibits EndoMT marker expression and transforming growth factor-β signaling in atherosclerotic mice. which is associated with the reductions of lesions in the ApoE-/- mouse model. Mechanistically, the loss of endothelial cell CD45 results in increased KLF2 expression, which inhibits transforming growth factor-β signaling and EndoMT. Consistently, endothelial CD45 deficient mice showed reduced lesion development, plaque macrophages, and expression of cell adhesion molecules when compared to ApoE-/- controls.

Conclusions

These findings demonstrate that the loss of endothelial CD45 protects against EndoMT-driven atherosclerosis, promoting KLF2 expression while inhibiting TGFβ signaling and EndoMT markers. Thus, targeting endothelial CD45 may be a novel therapeutic strategy for EndoMT and atherosclerosis.

Molecular Mechanisms Regulating Vascular Endothelial Permeability

Vascular endothelial cells form a monolayer in the vascular lumen and act as a selective barrier to control the permeability between blood and tissues. To maintain homeostasis, the endothelial barrier function must be strictly integrated. During acute inflammation, vascular permeability temporarily increases, allowing intravascular fluid, cells, and other components to permeate tissues. Moreover, it has been suggested that the dysregulation of endothelial cell permeability may cause several diseases, including edema, cancer, and atherosclerosis. Here, we reviewed the molecular mechanisms by which endothelial cells regulate the barrier function and physiological permeability.

Beyond VEGF: Angiopoietin-Tie Signaling Pathway in Diabetic Retinopathy

Complications from diabetic retinopathy such as diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) constitute leading causes of preventable vision loss in working-age patients. Since vascular endothelial growth factor (VEGF) plays a major role in the pathogenesis of these complications, VEGF inhibitors have been the cornerstone of their treatment. Anti-VEGF monotherapy is an effective but burdensome treatment for DME. However, due to the intensive and burdensome treatment, most patients in routine clinical practice are undertreated, and therefore, their outcomes are compromised. Even in adequately treated patients, persistent DME is reported anywhere from 30% to 60% depending on the drug used. PDR is currently treated by anti-VEGF, panretinal photocoagulation (PRP) or a combination of both. Similarly, a number of eyes, despite these treatments, continue to progress to tractional retinal detachment and vitreous hemorrhage. Clearly there are other molecular pathways other than VEGF involved in the pathogenesis of DME and PDR. One of these pathways is the angiopoietin-Tie signaling pathway. Angiopoietin 1 (Ang1) plays a major role in maintaining vascular quiescence and stability. It acts as a molecular brake against vascular destabilization and inflammation that is usually promoted by angiopoietin 2 (Ang2). Several pathological conditions including chronic hyperglycemia lead to Ang2 upregulation. Recent regulatory approval of the bi-specific antibody, faricimab, may improve long term outcomes in DME. It targets both the Ang/Tie and VEGF pathways. The YOSEMITE and RHINE were multicenter, double-masked, randomized non-inferiority phase 3 clinical trials that compared faricimab to aflibercept in eyes with center-involved DME. At 12 months of follow-up, faricimab demonstrated non-inferior vision gains, improved anatomic outcomes and a potential for extended dosing when compared to aflibercept. The 2-year results of the YOSEMITE and RHINE trials demonstrated that the anatomic and functional results obtained at the 1 year follow-up were maintained. Short term outcomes of previously treated and treatment-naive eyes with DME that were treated with faricimab during routine clinical practice suggest a beneficial effect of faricimab over other agents. Targeting of Ang2 has been reported by several other means including VE-PTP inhibitors, integrin binding peptide and surrobodies.

Single-Cell RNA-Seq Reveals Coronary Heterogeneity and Identifies CD133+TRPV4high Endothelial Subpopulation in Regulating Flow-Induced Vascular Tone in Mice

BACKGROUND

Single-cell RNA-Seq analysis can determine the heterogeneity of cells between different tissues at a single-cell level. Coronary artery endothelial cells (ECs) are important to coronary blood flow. However, little is known about the heterogeneity of coronary artery ECs, and cellular identity responses to flow. Identifying endothelial subpopulations will contribute to the precise localization of vascular endothelial subpopulations, thus enabling the precision of vascular injury treatment.

METHODS

Here, we performed a single-cell RNA sequencing of 31 962 cells and functional assays of 3 branches of the coronary arteries (right coronary artery/circumflex left coronary artery/anterior descending left coronary artery) in wild-type mice.

RESULTS

We found a compendium of 7 distinct cell types in mouse coronary arteries, mainly ECs, granulocytes, cardiac myocytes, smooth muscle cells, lymphocytes, myeloid cells, and fibroblast cells, and showed spatial heterogeneity between arterial branches. Furthermore, we revealed a subpopulation of coronary artery ECs, CD133+TRPV4high ECs. TRPV4 (transient receptor potential vanilloid 4) in CD133+TRPV4high ECs is important for regulating vasodilation and coronary blood flow.

CONCLUSIONS

Our study elucidates the nature and range of coronary arterial cell diversity and highlights the importance of coronary CD133+TRPV4high ECs in regulating coronary vascular tone.

Opto-RhoGEFs, an optimized optogenetic toolbox to reversibly control Rho GTPase activity on a global to subcellular scale, enabling precise control over vascular endothelial barrier strength

The inner layer of blood vessels consists of endothelial cells, which form the physical barrier between blood and tissue. This vascular barrier is tightly regulated and is defined by cell-cell contacts through adherens and tight junctions. To investigate the signaling that regulates vascular barrier strength, we focused on Rho GTPases, regulators of the actin cytoskeleton and known to control junction integrity. To manipulate Rho GTPase signaling in a temporal and spatial manner we applied optogenetics. Guanine-nucleotide exchange factor (GEF) domains from ITSN1, TIAM1, and p63RhoGEF, activating Cdc42, Rac, and Rho, respectively, were integrated into the optogenetic recruitment tool improved light-induced dimer (iLID). This tool allows for Rho GTPase activation at the subcellular level in a reversible and non-invasive manner by recruiting a GEF to a specific area at the plasma membrane, The membrane tag of iLID was optimized and a HaloTag was applied to gain more flexibility for multiplex imaging. The resulting optogenetically recruitable RhoGEFs (Opto-RhoGEFs) were tested in an endothelial cell monolayer and demonstrated precise temporal control of vascular barrier strength by a cell-cell overlap-dependent, VE-cadherin-independent, mechanism. Furthermore, Opto-RhoGEFs enabled precise optogenetic control in endothelial cells over morphological features such as cell size, cell roundness, local extension, and cell contraction. In conclusion, we have optimized and applied the optogenetic iLID GEF recruitment tool, that is Opto-RhoGEFs, to study the role of Rho GTPases in the vascular barrier of the endothelium and found that membrane protrusions at the junction region can rapidly increase barrier integrity independent of VE-cadherin.

Dialogue between VE-Cadherin and Sphingosine 1 Phosphate Receptor1 (S1PR1) for Protecting Endothelial Functions

The endothelial cells (EC) of established blood vessels in adults remain extraordinarily quiescent in the sense that they are not actively proliferating, but they fulfill the necessary role to control the permeability of their monolayer that lines the interior of blood vessels. The cell-cell junctions between ECs in the endothelium comprise tight junctions and adherens homotypic junctions, which are ubiquitous along the vascular tree. Adherens junctions are adhesive intercellular contacts that are crucial for the organization of the EC monolayer and its maintenance and regulation of normal microvascular function. The molecular components and underlying signaling pathways that control the association of adherens junctions have been described in the last few years. In contrast, the role that dysfunction of these adherens junctions has in contributing to human vascular disease remains an important open issue. Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid mediator found at high concentrations in blood which has important roles in the control of the vascular permeability, cell recruitment, and clotting that follow inflammatory processes. This role of S1P is achieved through a signaling pathway mediated through a family of G protein-coupled receptors designated as S1PR1. This review highlights novel evidence for a direct linkage between S1PR1 signaling and the mediation of EC cohesive properties that are controlled by VE-cadherin.

A refined protocol for the isolation and monoculture of primary mouse renal peritubular endothelial cells

During an episode of acute kidney injury (AKI), a sudden and rapid decline in renal function is often accompanied by a persistent reduction in mitochondrial function, microvasculature dysfunction/rarefaction, and tubular epithelial injury/necrosis. Additionally, patients who have experienced an AKI are at an elevated risk of developing other progressive renal, cardiovascular, and cardiorenal related diseases. While restoration of the microvasculature is imperative for oxygen and nutrient delivery/transport during proper renal repair processes, the mechanism(s) by which neovascularization and/or inhibition of microvascular dysfunction improves renal recovery remain understudied. Interestingly, pharmacological stimulation of mitochondrial biogenesis (MB) post-AKI has been shown to restore mitochondrial and renal function in mice. Thus, targeting MB pathways in microvasculature endothelial cell (MV-EC) may provide a novel strategy to improve renal vascular function and repair processes post-AKI. However, limitations to studying such mechanisms include a lack of commercially available primary renal peritubular MV-ECs, the variability in both purity and outgrowth of primary renal MV-EC in monoculture, the tendency of primary renal MV-ECs to undergo phenotypic loss in primary monoculture, and a limited quantity of published protocols to obtain primary renal peritubular MV-ECs. Thus, we focused on refining the isolation and phenotypic retention of mouse renal peritubular endothelial cells (MRPEC) for future physiological and pharmacological based studies. Here, we present a refined isolation method that augments the purity, outgrowth, and phenotypic retention of primary MRPEC monocultures by utilizing a collagenase type I enzymatic digestion, CD326+ (EPCAM) magnetic microbead epithelial cell depletion, and two CD146+ (MCAM) magnetic microbead purification cycles to achieve a monoculture MRPEC purity of ≅ 91-99% by all markers evaluated.

Human dermal microvascular endothelial cell morphological response to fluid shear stress

As the cells that line the vasculature, endothelial cells are continually exposed to fluid shear stress by blood flow. Recent studies suggest that the morphological response of endothelial cells to fluid shear stress depends on the endothelial cell type. Thus, the present study characterizes the morphological response of human dermal microvascular endothelial cells (HMEC-1) and nuclei to steady, laminar, and unidirectional fluid shear stress. Cultured HMEC-1 monolayers were exposed to shear stress of 0.3 dyn/cm², 16 dyn/cm², or 32 dyn/cm² for 72 h with hourly live-cell imaging capturing both the nuclear and cellular morphology. Despite changes in elongation and alignment occurring with increasing fluid shear stress, there was a lack of elongation and alignment over time under each fluid shear stress condition. Conversely, changes in cellular and nuclear area exhibited dependence on both time and fluid shear stress magnitude. The trends in cellular morphology differed at shear stress levels above and below 16 dyn/cm², whereas the nuclear orientation was independent of fluid shear stress magnitude. These findings show the complex morphological response of HMEC-1 to fluid shear stress.

The rs7404339 AA Genotype in CDH5 Contributes to Increased Risks of Kawasaki Disease and Coronary Artery Lesions in a Southern Chinese Child Population

Background

Kawasaki disease (KD) is an acute, self-limited febrile illness of unknown cause. And it predominantly affects children <5 years and the main complication is coronary artery lesion (CAL). Studies demonstrated that vascular endothelial cells (VECs) played a very important role in the CAL of KD. VE-cad encoded by CDH5 may exert a relevant role in endothelial cell biology through controlling the cohesion of the intercellular junctions. The pathogenesis of KD remains unclear and genetic factors may increase susceptibility of KD. However, the relationship between CDH5 polymorphisms and KD susceptibility has not been reported before. The present study is aimed at investigating whether the rs7404339 polymorphism in CDH5 is associated with KD susceptibility and CAL in a southern Chinese child population.

Methods and Results

We recruited 1,335 patients with KD and 1,669 healthy children. Each participant had supplied 2 mL of fresh blood in the clinical biologic bank at our hospital for other studies. Multiplex PCR is used to assess the genotypes of rs7404339 polymorphism in CDH5. According to the results, we found significant correlated relationship between rs7404339 polymorphism in CDH5 and KD susceptibility [AA vs. GG: adjusted odds ratio (OR) = 1.43, 95% confidence interval (CI) = 1.00-2.05; p = 0.0493; recessive model: adjusted OR = 1.44, 95% CI = 1.01-2.06, P = 0.0431]. In further stratified analysis, we found that children younger than 60 months (adjusted OR = 1.46, 95% CI = 1.01-2.10; p = 0.0424) and male (adjusted OR = 1.70, 95% CI = 1.09-2.65; p = 0.0203) with the rs7404339 AA genotype in CDH5 had a higher risk of KD than carriers of the GA/GG genotype. Furthermore, stratification analysis revealed that patients with the rs7404339 AA genotype exhibited the significantly higher onset risk for CAL than carriers of the GA/GG genotype (adjusted age and gender odds ratio = 1.56, 95% CI = 1.01-2.41; P = 0.0433).

Conclusion

Our results showed that rs7404339 AA genotype in CDH5 is significant associated with KD susceptibility. And children younger than 60 months and male with the rs7404339 AA genotype had a higher risk of KD than carriers with the GA/GG genotype. Furthermore, patients with the rs7404339 AA genotype exhibited a significantly higher risk of CAL complication than carriers of the GA/GG genotype.

Endothelial barrier dysfunction induced by anthracene and its nitrated or oxygenated derivatives at environmentally relevant levels

Polycyclic aromatic hydrocarbons (PAHs) are epidemiologically associated with cardiovascular diseases characterized by early key events involving in the disruption of endothelial barrier function. Whether PAHs can induce adverse cardiovascular outcome by directly destabilizing endothelial barrier function remains elusive. Herein, we investigated the effect of anthracene (ANT), 9-nitroanthracene (9-NANT), and 9,10-anthraquinone (9,10-AQ) on vascular endothelial barrier functions in human umbilical vein endothelial cells (HUVECs). The integrity of endothelial barrier in HUVECs was disturbed with a 1.15-1.42 fold increase in fluorescein leakage, and 21.8%-58.3% downregulated transendothelial electrical resistance. ANT, 9-NANT and 9,10-AQ promoted paracellular gap formation as revealed by transmission electron microscope. The disrupted cell junctions after 24 h exposure to ANT, 9-NANT and 9,10-AQ at 0.01 μM were indicated by the downregulated mRNA expression of vascular endothelial cadherin (VE-cadherin), zona occludens-1 (ZO-1) and occludin by 33.2%-71.4%, 19.1%-21.0%, and 31.9% respectively, and the downregulated protein expression of ZO-1 and occludin, and by the internalization of VE-cadherin. We demonstrated that ANT and its derivatives at environmentally relevant concentrations induced endothelial barrier dysfunction via the disruption of cell junctions, providing essential in vitro evidence on the association with their adverse cardiovascular outcomes.

Renal cell markers: lighthouses for managing renal diseases

Kidneys, one of the vital organs in our body, are responsible for maintaining whole body homeostasis. The complexity of renal function (e.g., filtration, reabsorption, fluid and electrolyte regulation, and urine production) demands diversity not only at the level of cell types but also in their overall distribution and structural framework within the kidney. To gain an in depth molecular-level understanding of the renal system, it is imperative to discern the components of kidney and the types of cells residing in each of the subregions. Recent developments in labeling, tracing, and imaging techniques have enabled us to mark, monitor, and identify these cells in vivo with high efficiency in a minimally invasive manner. In this review, we summarize different cell types, specific markers that are uniquely associated with those cell types, and their distribution in the kidney, which altogether make kidneys so special and different. Cellular sorting based on the presence of certain proteins on the cell surface allowed for the assignment of multiple markers for each cell type. However, different studies using different techniques have found contradictions in cell type-specific markers. Thus, the term "cell marker" might be imprecise and suboptimal, leading to uncertainty when interpreting the data. Therefore, we strongly believe that there is an unmet need to define the best cell markers for a cell type. Although the compendium of renal-selective marker proteins presented in this review is a resource that may be useful to researchers, we acknowledge that the list may not be necessarily exhaustive.

PECAM-1 supports leukocyte diapedesis by tension-dependent dephosphorylation of VE-cadherin

Leukocyte extravasation is an essential step during the immune response and requires the destabilization of endothelial junctions. We have shown previously that this process depends in vivo on the dephosphorylation of VE-cadherin-Y731. Here, we reveal the underlying mechanism. Leukocyte-induced stimulation of PECAM-1 triggers dissociation of the phosphatase SHP2 which then directly targets VE-cadherin-Y731. The binding site of PECAM-1 for SHP2 is needed for VE-cadherin dephosphorylation and subsequent endocytosis. Importantly, the contribution of PECAM-1 to leukocyte diapedesis in vitro and in vivo was strictly dependent on the presence of Y731 of VE-cadherin. In addition to SHP2, dephosphorylation of Y731 required Ca2+ -signaling, non-muscle myosin II activation, and endothelial cell tension. Since we found that β-catenin/plakoglobin mask VE-cadherin-Y731 and leukocyte docking to endothelial cells exert force on the VE-cadherin-catenin complex, we propose that leukocytes destabilize junctions by PECAM-1-SHP2-triggered dephosphorylation of VE-cadherin-Y731 which becomes accessible by actomyosin-mediated mechanical force exerted on the VE-cadherin-catenin complex.

Gastric cancer-secreted exosomal X26nt increases angiogenesis and vascular permeability by targeting VE-cadherin

Angiogenesis is closely associated with tumorigenesis, invasion, and metastasis by providing oxygen and nutrients. Recently, increasing evidence indicates that cancer-derived exosomes which contain proteins, coding, and noncoding RNAs (ncRNAs) were shown to have proangiogenic function in cancer. A 26-nt-long ncRNA (X26nt) is generated in the process of inositol-requiring enzyme 1 alpha (IRE1α)-induced unspliced XBP1 splicing. However, the role of X26nt in the angiogenesis of gastric cancer (GC) remains largely unknown. In the present study, we found that X26nt was significantly elevated in GC and GC exosomes. Then, we verified that X26nt could be delivered into human umbilical vein endothelial cells (HUVECs) via GC cell exosomes and promote the proliferation, migration, and tube formation of HUVECs. We revealed that exosomal X26nt decreased vascular endothelial cadherin (VE-cadherin) by directly combining the 3'UTR of VE-cadherin mRNA in HUVECs, thereby increasing vascular permeability. We further demonstrated that X26nt accelerates the tumor growth and angiogenesis in a mouse subcutaneous tumor model. Our findings investigate a unique intercellular communication mediated by cancer-derived exosomes and reveal a novel mechanism of exosomal X26nt in the regulation of tumor vasculature.

Vascular Endothelial Protein Tyrosine Phosphatase Regulates Endothelial Function

Vascular endothelial protein tyrosine phosphatase (VE-PTP) is a receptor-type PTP (RPTP), predominantly expressed in vascular endothelial cells. It regulates embryonic and tumor angiogenesis and controls vascular permeability and homeostasis in inflammation. Major substrates are the tyrosine kinase receptor Tie-2 and the adhesion molecule VE-cadherin. This review describes how VE-PTP controls vascular functions by its various substrates and the therapeutic potential of VE-PTP in various pathophysiological settings.

Epigenetic regulation of TLR2-mediated periapical inflammation

AIM

To determine the methylation pattern of TLR2 gene promoter and its association with the transcriptional regulation of periapical inflammatory and angiogenic responses in symptomatic and asymptomatic forms of apical periodontitis.

METHODOLOGY

In this cross-sectional study, apical lesions were obtained from volunteers with asymptomatic apical periodontitis (AAP) (n = 17) and symptomatic apical periodontitis (SAP) (n = 17) scheduled for tooth extraction, and both total RNA and DNA were extracted. DNA was bisulfite-treated, a region of CpG island within the TLR2 gene was amplified by qPCR and the products were sequenced. Additionally, the mRNA expression of TLR2, TLR4, IL-6, IL-12, TNFalpha, IL-23, IL-10, TGFbeta, VEGFA and CDH5 was analysed by qPCR. The data were analysed with chi-square tests, Mann-Whitney or unpaired t-tests, and Spearman´s correlation; variable adjustments were performed using multiple linear regression (P < 0.05).

RESULTS

TLR2 depicted a hypomethylated DNA profile at the CpG island in SAP when compared with AAP, along with upregulated expression of TLR2, with pro-inflammatory cytokines IL-6 and IL-23, and the angiogenesis marker CDH5 (P < 0.05). TLR2 methylation percentage negatively correlated with mRNA levels of IL-23 and CDH5 in apical periodontitis. Lower methylation frequencies of single CpG dinucleotides -8 and -10 localized in close proximity to nuclear factor κB (NFκB) binding within the TLR2 promoter were identified in SAP versus AAP (P < 0.05). Finally, unmethylated -10 and -8 single sites demonstrated up-regulation of IL-23, IL-10 and CDH5 transcripts compared to their methylated counterparts (P < 0.05).

CONCLUSIONS

TLR2 gene promoter hypomethylation was linked to transcriptional activity of pro-inflammatory cytokines and angiogenic markers in exacerbated periapical inflammation. Moreover, unmethylated single sites in close proximity to NFκB binding were involved in active transcription of IL-23, IL-10 and CDH5.

Aortic heterogeneity across segments and under high fat/salt/glucose conditions at the single-cell level

The aorta, with ascending, arch, thoracic and abdominal segments, responds to the heartbeat, senses metabolites and distributes blood to all parts of the body. However, the heterogeneity across aortic segments and how metabolic pathologies change it are not known. Here, a total of 216 612 individual cells from the ascending aorta, aortic arch, and thoracic and abdominal segments of mouse aortas under normal conditions or with high blood glucose levels, high dietary salt, or high fat intake were profiled using single-cell RNA sequencing. We generated a compendium of 10 distinct cell types, mainly endothelial (EC), smooth muscle (SMC), stromal and immune cells. The distributions of the different cells and their intercommunication were influenced by the hemodynamic microenvironment across anatomical segments, and the spatial heterogeneity of ECs and SMCs may contribute to differential vascular dilation and constriction that were measured by wire myography. Importantly, the composition of aortic cells, their gene expression profiles and their regulatory intercellular networks broadly changed in response to high fat/salt/glucose conditions. Notably, the abdominal aorta showed the most dramatic changes in cellular composition, particularly involving ECs, fibroblasts and myeloid cells with cardiovascular risk factor-related regulons and gene expression networks. Our study elucidates the nature and range of aortic cell diversity, with implications for the treatment of metabolic pathologies.

Amniotic Membrane Enhance the Effect of Vascular Endothelial Growth Factor on the Angiogenic Marker Expression of Stem Cells from Human Exfoliated Deciduous Teeth

Previously, it was reported that human amniotic membrane (AM) induced stem cells from human deciduous exfoliated teeth (SHED) endothelial-like-cell differentiation. This interesting effect of AM matrix on SHED demands further elucidation. Objective of this in vitro work was to study the effect of 24-h VEGF induced on SHED endothelial differentiation when seeded on acellular stromal side (SS) of AM matrix. Stemness of SHED was identified by flow cytometry. Cell attachment and morphological changes towards the matrix was observed by scanning electron microscopy. Protein expression of endothelial marker was examined by Western blot. The expression of stem cells and endothelial-specific gene markers of VEGF-induced SHED cultured on human AM was inspected via reverse transcriptase-polymerase chain reaction. Results showed SHED at both passages retain stemness property. Ang-1 protein was expressed in SHED. Cells treated with VEGF and cultured on AM transformed attached well to AM. VEGF-induced SHED expressed both stem cell and endothelial-specific markers throughout the treatments and timeline. Interestingly, prolonged VEGF treatment increased the expression of Cox-2 and VE-Cadherin genes in all treated groups when compared to SHED. It was concluded that the VEGF-induced SHED showed better expression of endothelial-specific markers when cultured on SS of AM, with prolonged VEGF treatment.

Circulating Biomarkers of Cell Adhesion Predict Clinical Outcome in Patients with Chronic Heart Failure

Cardiovascular inflammation and vascular endothelial dysfunction are involved in chronic heart failure (CHF), and cellular adhesion molecules are considered to play a key role in these mechanisms. We evaluated temporal patterns of 12 blood biomarkers of cell adhesion in patients with CHF. In 263 ambulant patients, serial, tri-monthly blood samples were collected during a median follow-up of 2.2 (1.4-2.5) years. The primary endpoint (PE) was a composite of cardiovascular mortality, HF hospitalization, heart transplantation and implantation of a left ventricular assist device and was reached in 70 patients. We selected the baseline blood samples in all patients, the two samples closest to a PE, or, for event-free patients, the last sample available. In these 567 samples, associations between biomarkers and PE were investigated by joint modelling. The median age was 68 (59-76) years, with 72% men and 74% New York Heart Association class I-II. Repeatedly measured levels of Complement component C1q receptor (C1qR), Cadherin 5 (CDH5), Chitinase-3-like protein 1 (CHI3L1), Ephrin type-B receptor 4 (EPHB4), Intercellular adhesion molecule-2 (ICAM-2) and Junctional adhesion molecule A (JAM-A) were independently associated with the PE. Their rates of change also predicted clinical outcome. Level of CHI3L1 was numerically the strongest predictor with a hazard ratio (HR) (95% confidence interval) of 2.27 (1.66-3.16) per SD difference in level, followed by JAM-A (2.10, 1.42-3.23) and C1qR (1.90, 1.36-2.72), adjusted for clinical characteristics. In conclusion, temporal patterns of C1qR, CDH5, CHI3L1, EPHB4, ICAM2 and JAM-A are strongly and independently associated with clinical outcome in CHF patients.

Integrin-dependent regulation of the endothelial barrier

The endothelium physically separates blood from surrounding tissue and yet allows for the regulated passage of nutrients, waste, and leukocytes into and out of the circulation. Trans-endothelium flux occurs across endothelial cells (transcellular) and between endothelial cells (paracellular). Paracellular endothelial barrier function depends on the regulation of cell-cell junctions. Interestingly, a functional relationship between cell-cell junctions and cell-matrix adhesions has long been appreciated but the molecular mechanisms underpinning this relationship are not fully understood. Here we review the evidence that supports the notion that cell-matrix interactions contribute to the regulation of cell-cell junctions, focusing primarily on the important adherens junction protein VE-cadherin. In particular, we will discuss recent insights gained into how integrin signaling impacts VE-cadherin stability in adherens junctions and endothelial barrier function.

Ionizing radiation increases the endothelial permeability and the transendothelial migration of tumor cells through ADAM10-activation and subsequent degradation of VE-cadherin

BACKGROUND

We analyzed the changes in permeability of endothelial cell layers after photon irradiation, with a focus on the metalloproteases ADAM10 and ADAM17, and on VE-cadherin, components crucial for the integrity of endothelial intercellular junctions, and their roles in the transmigration of cancer cells through endothelial cell monolayers.

METHODS

Primary HUVEC were irradiated with 2 or 4 Gy photons at a dose rate of 5 Gy/min. The permeability of an irradiated endothelial monolayer for macromolecules and tumor cells was analyzed in the presence or absence of the ADAM10/17 inhibitors GI254023X and GW280264X. Expression of ADAM10, ADAM17 and VE-Cadherin in endothelial cells was quantified by immunoblotting and qRT. VE-Cadherin was additionally analyzed by immunofluorescence microscopy and ELISA.

RESULTS

Ionizing radiation increased the permeability of endothelial monolayers and the transendothelial migration of tumor cells. This was effectively blocked by a selective inhibition (GI254023X) of ADAM10. Irradiation increased both, the expression and activity of ADAM10, which led to increased degradation of VE-cadherin, but also led to higher rates of VE-cadherin internalization. Increased degradation of VE-cadherin was also observed when endothelial monolayers were exposed to tumor-cell conditioned medium, similar to when exposed to recombinant VEGF.

CONCLUSIONS

Our results suggest a mechanism of irradiation-induced increased permeability and transendothelial migration of tumor cells based on the activation of ADAM10 and the subsequent change of endothelial permeability through the degradation and internalization of VE-cadherin.

Cadherin Signaling in Cancer: Its Functions and Role as a Therapeutic Target

Cadherin family includes lists of transmembrane glycoproteins which mediate calcium-dependent cell-cell adhesion. Cadherin-mediated adhesion regulates cell growth and differentiation throughout life. Through the establishment of the cadherin-catenin complex, cadherins provide normal cell-cell adhesion and maintain homeostatic tissue architecture. In the process of cell recognition and adhesion, cadherins act as vital participators. As results, the disruption of cadherin signaling has significant implications on tumor formation and progression. Altered cadherin expression plays a vital role in tumorigenesis, tumor progression, angiogenesis, and tumor immune response. Based on ongoing research into the role of cadherin signaling in malignant tumors, cadherins are now being considered as potential targets for cancer therapies. This review will demonstrate the mechanisms of cadherin involvement in tumor progression, and consider the clinical significance of cadherins as therapeutic targets.

The interstitium in cardiac repair: role of the immune-stromal cell interplay

Cardiac regeneration, that is, restoration of the original structure and function in a damaged heart, differs from tissue repair, in which collagen deposition and scar formation often lead to functional impairment. In both scenarios, the early-onset inflammatory response is essential to clear damaged cardiac cells and initiate organ repair, but the quality and extent of the immune response vary. Immune cells embedded in the damaged heart tissue sense and modulate inflammation through a dynamic interplay with stromal cells in the cardiac interstitium, which either leads to recapitulation of cardiac morphology by rebuilding functional scaffolds to support muscle regrowth in regenerative organisms or fails to resolve the inflammatory response and produces fibrotic scar tissue in adult mammals. Current investigation into the mechanistic basis of homeostasis and restoration of cardiac function has increasingly shifted focus away from stem cell-mediated cardiac repair towards a dynamic interplay of cells composing the less-studied interstitial compartment of the heart, offering unexpected insights into the immunoregulatory functions of cardiac interstitial components and the complex network of cell interactions that must be considered for clinical intervention in heart diseases.

Targeted-nanoliposomal combretastatin A4 (CA-4) as an efficient antivascular candidate in the metastatic cancer treatment

A number of antiangiogenic drugs have been approved by the Food and Drug Administration which are used in cancer therapy, and variety of other agents in several stages of clinical development or in preclinical assessment. Among these, combretastatin A4 (CA-4) is an under-researched inhibitor of angiogenesis that shows potential activity in the treatment of advanced tumors with migration capacity. However, its clinical application has been limited due to poor water solubility, low bioavailability, rapid metabolism, and systemic elimination. During the last decade, numerous investigations have been done to overcome these problems by using different CA-4 delivery systems or developing produgs of CA-4 or its structural analogs. Nevertheless, these strategies could not be efficient out of the undesired side effects on normal tissues. Nanoliposomal CA-4 not only benefits from the advantage of using liposomal drugs as opposed to free drugs but also can accumulate in the tumor site via specific targeting ligands, which leads to efficient targeting and enhancement of bioavailability. To the best of our knowledge, we consider an important attempt to understand different factors that might influence the CA-4 loading and release pattern of liposomes and the consequent results in tumor therapy. In this review, we shed light on various studied liposomal CA-4 formulations showing application thereof in cancer treatment.

Single-Cell Transcriptional Profiling Reveals Cellular Diversity and Intercommunication in the Mouse Heart

Characterization of the cardiac cellulome, the network of cells that form the heart, is essential for understanding cardiac development and normal organ function and for formulating precise therapeutic strategies to combat heart disease. Recent studies have reshaped our understanding of cardiac cellular composition and highlighted important functional roles for non-myocyte cell types. In this study, we characterized single-cell transcriptional profiles of the murine non-myocyte cardiac cellular landscape using single-cell RNA sequencing (scRNA-seq). Detailed molecular analyses revealed the diversity of the cardiac cellulome and facilitated the development of techniques to isolate understudied cardiac cell populations, such as mural cells and glia. Our analyses also revealed extensive networks of intercellular communication and suggested prevalent sexual dimorphism in gene expression in the heart. This study offers insights into the structure and function of the mammalian cardiac cellulome and provides an important resource that will stimulate studies in cardiac cell biology.

The Role of Epithelial and Vascular-Endothelial Cadherin in the Differentiation and Maintance of Tissue Integrity

The present review has focused on the cell adhesion molecules from the cadherin superfamily, in particular on E- and VE-cadherin. In general, cadherins are a large group of cell adhesion molecules located at intercellular junctions called adherent junctions. They play an important role in embryogenesis and morphogenesis in animals and humans due to their adhesive and cell-signalling functions. Disturbances of the expression or function of cadherins and their associated proteins called catenins are crucial for the initiation and development of many pathological states. E-cadherin is an epithelium-specific cadherin that is required for the development and maintenance of the normal function of all epithelial cells in tissues. The loss or down-regulation of E-cadherin is a key event in the process of tumour invasion and metastasis. The assessment of E-cadherin immunoreactivity may be a useful prognostic marker in some cancers, complementary to the established prognostic factors. VE-cadherin is an endothelium-specific cadherin, which plays a relevant role in vascular homeostasis. It has been demonstrated that VE-cadherin is required for normal vasculogenesis, angiogenesis, and for the maintenance of vascular integrity. Disruption of VE-cadherin-catenin complexes by some inflammatory agents such as thrombin, by inflammatory cells, or shear stress is accompanied by an increase in vascular permeabilityin vivoandin vitro.

VE-PTP stabilizes VE-cadherin junctions and the endothelial barrier via a phosphatase-independent mechanism

Juettner et al. describe a novel phosphatase-activity–independent mechanism by which the phosphatase VE-PTP restricts endothelial permeability. VE-PTP functions as a scaffold that binds and inhibits the RhoGEF GEF-H1, limiting RhoA-dependent tension across VE-cadherin junctions and decreasing VE-cadherin internalization to stabilize adherens junctions and reduce endothelial permeability.

Vascular endothelial (VE) protein tyrosine phosphatase (PTP) is an endothelial-specific phosphatase that stabilizes VE-cadherin junctions. Although studies have focused on the role of VE-PTP in dephosphorylating VE-cadherin in the activated endothelium, little is known of VE-PTP’s role in the quiescent endothelial monolayer. Here, we used the photoconvertible fluorescent protein VE-cadherin-Dendra2 to monitor VE-cadherin dynamics at adherens junctions (AJs) in confluent endothelial monolayers. We discovered that VE-PTP stabilizes VE-cadherin junctions by reducing the rate of VE-cadherin internalization independently of its phosphatase activity. VE-PTP serves as an adaptor protein that through binding and inhibiting the RhoGEF GEF-H1 modulates RhoA activity and tension across VE-cadherin junctions. Overexpression of the VE-PTP cytosolic domain mutant interacting with GEF-H1 in VE-PTP–depleted endothelial cells reduced GEF-H1 activity and restored VE-cadherin dynamics at AJs. Thus, VE-PTP stabilizes VE-cadherin junctions and restricts endothelial permeability by inhibiting GEF-H1, thereby limiting RhoA signaling at AJs and reducing the VE-cadherin internalization rate.

Vascular endothelial cadherin shedding is more severe in sepsis patients with severe acute kidney injury

BACKGROUND

Vascular endothelial cadherin (VE-cadherin) is a membrane protein that is the major component of adherens junctions between endothelial cells. It is crucial for regulating vascular integrity, endothelial permeability, and angiogenesis. During inflammatory processes, VE-cadherin is shed into circulation (sVE-cadherin). Plasma sVE-cadherin is elevated in sepsis, malignancy, autoimmune diseases, and coronary atherosclerosis. However, the relationship between specific organ failures, especially severe acute kidney injury (AKI) defined by requirement for renal replacement therapy (AKI-RRT), and plasma sVE-cadherin levels in severe sepsis has not been well studied.

METHODS

The present study is a prospective study of critically ill adults with sepsis and acute respiratory failure (age ≥ 18 years) enrolled in the Validating Acute Lung Injury markers for Diagnosis (VALID) study. Plasma sVE-cadherin was measured at study enrollment. Primary analysis focused on the association between sVE-cadherin levels and the development of AKI, AKI-RRT, other organ dysfunction as defined by Brussels organ failure scores, pulmonary versus non-pulmonary sepsis, acute respiratory distress syndrome (ARDS), and in-hospital mortality.

RESULTS

Of 228 severe sepsis patients included, 80 (35%) developed AKI-RRT. Plasma sVE-cadherin levels at enrollment were significantly higher in patients with AKI-RRT compared with patients without AKI-RRT (p = 0.003). Plasma sVE-cadherin levels by quartile were significantly higher in severe sepsis patients with acute kidney injury stage 3 (p = 0.044) as defined by Kidney Disease Improving Global Outcomes (KDIGO) criteria. Patients with greater than 2 organ failures had higher plasma sVE-cadherin levels than patients with 2 or fewer organ failures (p < 0.001). In a multivariable analysis, plasma sVE-cadherin was independently associated with AKI-RRT (odds ratio 6.44 per log increase in plasma sVE-cadherin, 95% CI 1.126-36.847, p = 0.036). Plasma sVE-cadherin levels were significantly higher in patients with non-pulmonary sepsis compared to pulmonary sepsis (p < 0.001).

CONCLUSION

Shedding of sVE-cadherin is associated with severe acute kidney injury and with more severe organ dysfunction in patients with sepsis, suggesting that breakdown of endothelial adherens junctions may contribute to the pathogenesis of organ dysfunction in sepsis. Further studies of sVE-cadherin as a biomarker of disease severity in clinical sepsis are needed to better elucidate the role of VE-cadherin shedding in sepsis-induced severe organ dysfunction.

Deubiquitinase function of A20 maintains and repairs endothelial barrier after lung vascular injury

Vascular endothelial cadherin (VE-cad) expression at endothelial adherens junctions (AJs) regulates vascular homeostasis. Here we show that endothelial A20 is required for VE-cad expression at AJs to maintain and repair the injured endothelial barrier. In endothelial cell (EC)-restricted Tnfaip3 (A20) knockout (A20^∆EC ) mice, LPS challenge caused uncontrolled lung vascular leak and persistent sequestration of polymorphonuclear neutrophil (PMNs). Importantly, A20^∆EC mice exhibited drastically reduced VE-cad expression in lungs compared with wild-type counterparts. Endothelial expression of wild-type A20 but not the deubiquitinase-inactive A20 mutant (A20^C103A) prevented VE-cad ubiquitination, restored VE-cad expression, and suppressed lung vascular leak in A20^∆EC mice. Interestingly, IRAK-M-mediated nuclear factor-κB (NF-κB) signaling downstream of TLR4 was required for A20 expression in ECs. interleukin-1 receptor-associated kinase M (IRAK-M) knockdown suppressed basal and LPS-induced A20 expression in ECs. Further, in vivo silencing of IRAK-M in mouse lung vascular ECs through the CRISPR-Cas9 system prevented expression of A20 and VE-cad while augmenting lung vascular leak. These results suggest that targeting of endothelial A20 is a potential therapeutic strategy to restore endothelial barrier integrity in the setting of acute lung injury.

Cadherins and Integrins in Renal Cell Carcinoma an Immunohistochemical Study

Aims and Background

The aim of this study was to determine the expression of cadherins and integrins in renal cell carcinoma (RCC) and their relationship with tumor morphology and TNM status.

Methods

Cadherin and integrin expression was investigated using an indirect immunoperoxidase technique, applying antibodies to E-, N-, P- and VE-cadherin and to α1, α2, α3, α4, α5, α6 and αv integrin subunits. Correlation of semiquantitatively scored adhesion molecule levels with histopathological parameters (cytology, growth pattern, nuclear grade) and TNM status was performed for 24 RCCs (17 clear cell, 3 granular, 3 spindle cell and 1 chromophobe cell type according to the WHO classification).

Results

E-cadherin and N-cadherin were present in most cases (88% and 67%, respectively) and were usually coex-pressed. T3 RCCs displayed higher E-cadherin and N-cadherin levels than T1/T2 tumors regardless of tumor grade, suggesting that impairment of their function might exist without actual loss from tumor cells. P-cadherin was found focally in two RCCs only, while VE-cadherin was present on stromal vessel endothelium in five tumors, showing no differences with regard to cell type, growth pattern, tumor grade or TNM status. All integrins were present in the studied RCCs (ranging from 12% for α5 to 79% for α3), including those that are normally absent from adult kidney tissue (α4 and α5). Tumors of higher grade showed increased αv and decreased α6 levels, while RCCs with metastases less often showed diffuse α3 presence and never expressed α5 integrin.

Conclusions

Our results suggest that the level of expression of N-cadherin and some integrins (most notably α3, α6, and α5) is associated with the capacity of RCC for local and distant spread, regardless of tumor grade.

The expression of VE-cadherin in breast cancer cells modulates cell dynamics as a function of tumor differentiation and promotes tumor-endothelial cell interactions

The cadherin switch has profound consequences on cancer invasion and metastasis. The endothelial-specific vascular endothelial cadherin (VE-cadherin) has been demonstrated in diverse cancer types including breast cancer and is supposed to modulate tumor progression and metastasis, but underlying mechanisms need to be better understood. First, we evaluated VE-cadherin expression by tissue microarray in 392 cases of breast cancer tumors and found a diverse expression and distribution of VE-cadherin. Experimental expression of fluorescence-tagged VE-cadherin (VE-EGFP) in undifferentiated, fibroblastoid and E-cadherin-negative MDA-231 (MDA-VE-EGFP) as well as in differentiated E-cadherin-positive MCF-7 human breast cancer cell lines (MCF-VE-EGFP), respectively, displayed differentiation-dependent functional differences. VE-EGFP expression reversed the fibroblastoid MDA-231 cells to an epithelial-like phenotype accompanied by increased β-catenin expression, actin and vimentin remodeling, increased cell spreading and barrier function and a reduced migration ability due to formation of VE-cadherin-mediated cell junctions. The effects were largely absent in both MDA-VE-EGFP and in control MCF-EGFP cell lines. However, MCF-7 cells displayed a VE-cadherin-independent planar cell polarity and directed cell migration that both developed in MDA-231 only after VE-EGFP expression. Furthermore, VE-cadherin expression had no effect on tumor cell proliferation in monocultures while co-culturing with endothelial cells enhanced tumor cell proliferation due to integration of the tumor cells into monolayer where they form VE-cadherin-mediated cell contacts with the endothelium. We propose an interactive VE-cadherin-based crosstalk that might activate proliferation-promoting signals. Together, our study shows a VE-cadherin-mediated cell dynamics and an endothelial-dependent proliferation in a differentiation-dependent manner.

MiR-4505 aggravates lipopolysaccharide-induced vascular endothelial injury by targeting heat shock protein A12B

Heat shock protein family A member 12B (HSPA12B) is a heat shock protein primarily expressed in endothelial cells. Our previous study showed that it was protective against endothelial injury induced by lipopolysaccharide (LPS). The present study was performed to investigate whether micro (mi)RNA was involved in HSPA12B expression in endothelial cells challenged by LPS. We first screened the miRNA candidates potentially related to HSPA12B by bioinformatics analysis. Then the mimics of the miRNA candidates were transfected into human umbilical vein endothelial cells (HUVECs) to investigate the miRNAs that negatively regulated HSPA12B expression. The miRNA expression was also determined in LPS‑stimulated HUVECs. Dual luciferase activity assay was performed to confirm the relationship between the candidate miRNA and HSPA12B. Role of nuclear factor (NF)‑κB in the miRNA expression was investigated by using its inhibitor. Finally, the role of the miRNA on LPS induced injury was investigated. Eleven miRNAs were screened by bioinformatics analysis and 4 of them could inhibit HSPA12B expression at both mRNA and protein levels. Among the 4 miRNA candidates, only miR‑4505 was highly expressed in HUVECs stimulated by LPS. Luciferase analysis showed that miR‑4505 directly interacted with the 3'untranslated region of HSPA12B. LPS‑induced upregulation of miR‑4505 was blocked by NF‑κB inhibitor. Transfection with miR‑4505 mimics reduced the transendothelial electrical resistance and vascular endothelial‑cadherin expression. The scratch test demonstrated that miR‑4505 inhibited endothelial migration capacity. In conclusion, miR‑4505 downregulates the expression of HSPA12B and aggravates the LPS‑induced vascular endothelial cell injury.

Pyk2 phosphorylation of VE-PTP downstream of STIM1-induced Ca2+ entry regulates disassembly of adherens junctions

Vascular endothelial protein tyrosine phosphatase (VE-PTP) stabilizes endothelial adherens junctions (AJs) through constitutive dephosphorylation of VE-cadherin. Here we investigated the role of stromal interaction molecule 1 (STIM1) activation of store-operated Ca²⁺ entry (SOCE) in regulating AJ assembly. We observed that SOCE induced by STIM1 activated Pyk2 in human lung microvascular endothelial cells (ECs) and induced tyrosine phosphorylation of VE-PTP at Y1981. Pyk2-induced tyrosine phosphorylation of VE-PTP promoted Src binding to VE-PTP, Src activation, and subsequent VE-cadherin phosphorylation and thereby increased the endothelial permeability response. The increase in permeability was secondary to disassembly of AJs. Pyk2-mediated responses were blocked in EC-restricted Stim1 knockout mice, indicating the requirement for STIM1 in initiating the signaling cascade. A peptide derived from the Pyk2 phosphorylation site on VE-PTP abolished the STIM1/SOCE-activated permeability response. Thus Pyk2 activation secondary to STIM1-induced SOCE causes tyrosine phosphorylation of VE-PTP, and VE-PTP, in turn, binds to and activates Src, thereby phosphorylating VE-cadherin to increase endothelial permeability through disassembly of AJs. Our results thus identify a novel signaling mechanism by which STIM1-induced Ca²⁺ signaling activates Pyk2 to inhibit the interaction of VE-PTP and VE-cadherin and hence increase endothelial permeability. Therefore, targeting the Pyk2 activation pathway may be a potentially important anti-inflammatory strategy.

Hypoxia-selective inhibition of angiogenesis development by NAMI-A analogues

The antimetastatic ruthenium(III) complex (H₂Im)[trans-RuCl₄(HIm)(DMSO)] (NAMI-A) as well as its two analogues (H₂Ind)[trans-RuCl₄(HInd)(DMSO)] (Ru-Ind) and (HIsq)[trans-RuCl₄(Isq)(DMSO)] (Ru-Isq) (HIm–imidazole, HInd–indazole, Isq–isoquinoline, DMSO–dimethyl sulfoxide) were tested for their effect on endothelial cell functions in vitro on human skin microvascular endothelial cells (HSkMEC) and human endothelial progenitor cells (HPEC-CB.2) under normoxic (21 % O₂) and hypoxic (1 % O₂) conditions. All studied complexes showed very low cytotoxicity profiles towards both mature microvascular and precursor endothelial cells (ECs), independently of oxygen concentration. Among tested compounds Ru-Ind exhibited the highest cytotoxicity. The antiangiogenic activity of ruthenium complexes was evaluated for their influence on pseudo-vessels formation by microvascular endothelial cells (HSkMEC) because of their involvement in melanoma progression. Our studies indicated that Ru-Ind and Ru-Isq exhibited hypoxia- and dose-dependent-inhibition of angiogenesis on Matrigel™. Significant hypoxia-selective downregulation of pseudo-vessels formation by Ru-Isq correlates with efficient inhibition of cell motility. Interestingly, in the applied concentration doses migration of endothelial cells was also inhibited by NAMI-A, but the pseudo-vessels formation on Matrigel™ was unaffected. Angiogenesis-related genes expression profile for both mature and precursor ECs indicated that inhibition of angiogenesis, mainly due to Ru-Isq, as compared to NAMI-A and Ru-Ind correlated with downregulation of CD31 and CD144 expression and upregulation of NOTCH4 expression in mature ECs, which is essential for endothelial cell motility and stalk cells organization control. The hypoxia-selective antiangiogenic activity of Ru-Ind and Ru-Isq, NAMI-A analogues makes them potent antimetastatic therapeutics for their selective action in hypoxia which controls tumor pathologic angiogenesis.

Dipeptidyl Peptidase-4 Inhibitor Increases Vascular Leakage in Retina through VE-cadherin Phosphorylation

The inhibitors of CD26 (dipeptidyl peptidase-4; DPP4) have been widely prescribed to control glucose level in diabetic patients. DPP4-inhibitors, however, accumulate stromal cell-derived factor-1α (SDF-1α), a well-known inducer of vascular leakage and angiogenesis both of which are fundamental pathophysiology of diabetic retinopathy. The aim of this study was to investigate the effects of DPP4-inhibitors on vascular permeability and diabetic retinopathy. DPP4-inhibitor (diprotin A or sitagliptin) increased the phosphorylation of Src and vascular endothelial-cadherin (VE-cadherin) in human endothelial cells and disrupted endothelial cell-to-cell junctions, which were attenuated by CXCR4 (receptor of SDF-1α)-blocker or Src-inhibitor. Disruption of endothelial cell-to-cell junctions in the immuno-fluorescence images correlated with the actual leakage of the endothelial monolayer in the transwell endothelial permeability assay. In the Miles assay, vascular leakage was observed in the ears into which SDF-1α was injected, and this effect was aggravated by DPP4-inhibitor. In the model of retinopathy of prematurity, DPP4-inhibitor increased not only retinal vascularity but also leakage. Additionally, in the murine diabetic retinopathy model, DPP4-inhibitor increased the phosphorylation of Src and VE-cadherin and aggravated vascular leakage in the retinas. Collectively, DPP4-inhibitor induced vascular leakage by augmenting the SDF-1α/CXCR4/Src/VE-cadherin signaling pathway. These data highlight safety issues associated with the use of DPP4-inhibitors.

Review of the Effects of Anti-Angiogenic Compounds on the Epiphyseal Growth Plate

The formation of new blood vessels from a pre-existing vascular bed, termed “angiogenesis,” is of critical importance for the growth and development of the animal since it is required for the growth of the skeleton during endochondral ossification, development and cycling of the corpus luteum and uterus, and for the repair of tissues during wound healing. “Vasculogenesis,” the de novo formation of blood vessels is also important for the proper function and development of the vascular system in the embryo. New blood vessel formation is a prominent feature and permissive factor in the relentless progression of many human diseases, one of the most important examples of which is neoplasia. It is for this reason that angiogenesis is considered to be one of the hallmarks of cancer. The development of new classes of drugs that inhibit the growth and proper functioning of new blood vessels in vivo is likely to provide significant therapeutic benefit in the treatment of cancer, as well as other conditions where angiogenesis is a strong driver to the disease process. During the preclinical safety testing of these drugs, it is becoming increasingly clear that their in vivo efficacy is reflected in the profile of “expected toxicity” (resulting from pharmacology) observed in laboratory animals, so much so, that this profile of “desired” toxicity may act as a signature for their anti-angiogenic effect. In this article we review the major mechanisms controlling angiogenesis and its role during endochondral ossification. We also review the effects of perturbation of endochondral ossification through four mechanisms—inhibition of vascular endothelial growth factor (VEGF), pp60 c-Src kinase and matrix metalloproteinases as well as disruption of the blood supply with vascular targeting agents. Inhibition through each of these mechanisms appears to have broadly similar effects on the epiphyseal growth plate characterised by thickening due to the retention of hypertrophic chondrocytes resulting from the inhibition of angiogenesis. In contrast, in the metaphysis there are differing effects reflecting the specific role of these targets at this site.

Disrupted Endothelial Cell Layer and Exposed Extracellular Matrix Proteins Promote Capture of Late Outgrowth Endothelial Progenitor Cells

Late outgrowth endothelial progenitor cells (LO-EPC) possess a high proliferative potential, differentiate into vascular endothelial cells (EC), and form networks, suggesting they play a role in vascular repair. However, due to their scarcity in the circulation there is a requirement for ex vivo expansion before they could provide a practical cell therapy and it is currently unclear if they would home and engraft to an injury site. Using an in vitro flow system we studied LO-EPC under simulated injury conditions including EC activation, ischaemia, disrupted EC integrity, and exposed basement membrane. Perfused LO-EPC adhered to discontinuous EC paracellularly at junctional regions between adjacent cells under shear stress 0.7 dyn/cm(2). The interaction was not adhesion molecule-dependent and not enhanced by EC activation. LO-EPC expressed high levels of the VE-Cadherin which may explain these findings. Ischaemia reperfusion injury decreased the interaction with LO-EPC due to cell retraction. LO-EPC interacted with exposed extracellular matrix (ECM) proteins, fibronectin and vitronectin. The interaction was mediated by integrins α5β3, αvβ1, and αvβ3. This study has demonstrated that an injured local environment presents sufficient adhesive signals to capture flow perfused LO-EPC in vitro and that LO-EPC have properties consistent with their potential role in vascular repair.

Interfering with VE-PTP stabilizes endothelial junctions in vivo via Tie-2 in the absence of VE-cadherin

Inhibition of VE-PTP counters vascular leakage in inflammation via TIE-2, even in the absence of VE-cadherin.

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 Ins and Outs of Small GTPase Rac1 in the Vasculature

The Rho family of small GTPases forms a 20-member family within the Ras superfamily of GTP-dependent enzymes that are activated by a variety of extracellular signals. The most well known Rho family members are RhoA (Ras homolog gene family, member A), Cdc42 (cell division control protein 42), and Rac1 (Ras-related C3 botulinum toxin substrate 1), which affect intracellular signaling pathways that regulate a plethora of critical cellular functions, such as oxidative stress, cellular contacts, migration, and proliferation. In this review, we describe the current knowledge on the role of GTPase Rac1 in the vasculature. Whereas most recent reviews focus on the role of vascular Rac1 in endothelial cells, in the present review we also highlight the functional involvement of Rac1 in other vascular cells types, namely, smooth muscle cells present in the media and fibroblasts located in the adventitia of the vessel wall. Collectively, this overview shows that Rac1 activity is involved in various functions within one cell type at distinct locations within the cell, and that there are overlapping but also cell type-specific functions in the vasculature. Chronically enhanced Rac1 activity seems to contribute to vascular pathology; however, Rac1 is essential to vascular homeostasis, which makes Rac1 inhibition as a therapeutic option a delicate balancing act.

IL-33 and IL-4 impair barrier functions of human vascular endothelium via different mechanisms

The vascular endothelium forms a barrier that controls flow of solutes and proteins and the entry of leukocytes into tissue. Injured tissue releases IL-33, which then alarms the immune system and attracts Th2 cells, thus increasing local concentration of IL-4. The aim of the study was to assess the influence of IL-33 and IL-4 on barrier functions of the human endothelium, expression of tight and adherent junction proteins, apoptosis and adhesive molecule surface expression in human endothelium in order to describe the mechanism of this effect. IL-33 and IL-4 decreased endothelial integrity and increased permeability. When added together, both cytokines lowered the endothelial integrity twice as much as used alone. This effect was accompanied by the down-regulation of occludin and VE-cadherin mRNA expression. Additionally, IL-4, but not IL-33, induced cell apoptosis. Both IL-33 and IL-4 showed the additive potency to down-regulate VE-cadherin mRNA expression. IL-33, unlike IL-4, increased the surface expression of ICAM-1, but not PECAM-1 in endothelial cells. Our results indicate that IL-33 may reversibly destabilize the endothelial barrier, thus accelerating the supply with immunomodulators and assisting leukocytes to reach wounded tissue. However, extended and less-controlled down-regulation of endothelial barrier, which may be a consequence of IL-33-initiated, but in fact IL-4-induced apoptosis of endothelial cells, may be deleterious and may eventually lead to the aggravation of inflammatory processes and the prolongation of tissue dysfunction.

Nitric Oxide Increases Arterial Endotheial Permeability through Mediating VE-Cadherin Expression during Arteriogenesis

Macrophage invasion is an important event during arteriogenesis, but the underlying mechanism is still only partially understood. The present study tested the hypothesis that nitric oxide (NO) and VE-cadherin, two key mediators for vascular permeability, contribute to this event in a rat ischemic hindlimb model. In addition, the effect of NO on expression of VE-caherin and endothelial permeability was also studied in cultured HUVECs. We found that: 1) in normal arteriolar vessels (NAV), eNOS was moderately expressed in endothelial cells (EC) and iNOS was rarely detected. In contrast, in collateral vessels (CVs) induced by simple femoral artery ligation, both eNOS and iNOS were significantly upregulated (P<0.05). Induced iNOS was found mainly in smooth muscle cells, but also in other vascular cells and macrophages; 2) in NAV VE-cadherin was strongly expressed in EC. In CVs, VE-cadherin was significantly downregulated, with a discontinuous and punctate pattern. Administration of nitric oxide donor DETA NONOate (NONOate) further reduced the amounts of Ve-cadherin in CVs, whereas NO synthase inhibitor L-NAME inhibited downregulation of VE-cadherin in CVs; 3) in normal rats Evans blue extravasation (EBE) was low in the musculus gracilis, FITC-dextron leakage was not detected in the vascular wall and few macrophages were observed in perivascular space. In contrast, EBE was significantly increased in femoral artery ligation rats, FITC-dextron leakage and increased amounts of macrophages were detected in CVs, which were further enhanced by administration of NONOate, but inhibited by L-NAME supplement; 4) in vitro experiments confirmed that an increase in NO production reduced VE-cadherin expression, correlated with increases in the permeability of HUVECs. In conclusion, our data for the first time reveal the expression profile of VE-cadherin and alterations of vascular permeability in CVs, suggesting that NO-mediated VE-cadherin pathway may be one important mechanism responsible, at least in part, for macrophage invasion during arteriogenesis.

Soluble plasma VE-cadherin concentrations are elevated in patients with STEC infection and haemolytic uraemic syndrome: a case-control study

OBJECTIVES

To investigate whether the adherens junction protein vascular endothelial cadherin (VE-cadherin) is released during Shiga toxin 2 producing Escherichia coli (STEC) infection with haemolytic uraemic syndrome (HUS) and thus could be used to assist diagnosis.

DESIGN

Using data from the large 2011 STEC outbreak in northern Europe, we determined VE-cadherin plasma concentrations in 356 patients distributed over three patient cohorts: patients with STEC infection accompanied by HUS (STEC-HUS), STEC patients without HUS (STEC) and control patients with diarrhoea but without STEC infection. We then looked for associations between VE-cadherin concentrations and disease severity defined by changes in lactate dehydrogenase, haemoglobin, creatinine, platelet count, haptoglobin and neurological symptoms.

SETTING

This study was conducted at the University Medical Center Hamburg-Eppendorf, Germany.

PARTICIPANTS

79 STEC-HUS patients, 77 STEC patients and 200 control patients were enrolled in the study.

RESULTS

We analysed 864 specimens (207 STEC, 449 STEC-HUS and 208 controls) in total. At admission, VE-cadherin concentration tended to be lower in STEC-HUS patients compared to other patients. However, HUS patients later showed an increase in VE-cadherin concentrations with prolonged elevation beyond remission. This pattern clearly differs from that observed in non-HUS patients.

CONCLUSIONS

VE-cadherin concentrations are elevated in STEC-HUS patients and might be a biomarker reflecting endothelial damage in patients with HUS.

p18, a novel adaptor protein, regulates pulmonary endothelial barrier function via enhanced endocytic recycling of VE-cadherin

Vascular permeability is a hallmark of several disease states including acute lung injury (ALI). Endocytosis of VE-cadherin, away from the interendothelial junction (IEJ), causes acute endothelial barrier permeability. A novel protein, p18, anchors to the endosome membrane and plays a role in late endosomal signaling via MAPK and mammalian target of rapamycin. However, the fate of the VE-cadherin-positive endosome has yet to be elucidated. We sought to elucidate a role for p18 in VE-cadherin trafficking and thus endothelial barrier function, in settings of ALI. Endothelial cell (EC) resistance, whole-cell ELISA, and filtration coefficient were studied in mice or lung ECs overexpressing wild-type or nonendosomal-binding mutant p18, using green fluorescent protein as a control. We demonstrate a protective role for the endocytic protein p18 in endothelial barrier function in settings of ALI in vitro and in vivo, through enhanced recycling of VE-cadherin-positive early endosomes to the IEJ. In settings of LPS-induced ALI, we show that Src tethered to the endosome tyrosine phosphorylates p18 concomitantly with VE-cadherin internalization and pulmonary edema formation. We conclude that p18 regulates pulmonary endothelial barrier function in vitro and in vivo, by enhancing recycling of VE-cadherin-positive endosomes to the IEJ.

VE-cadherin-independent cancer cell incorporation into the vascular endothelium precedes transmigration

Metastasis is accountable for 90% of cancer deaths. During metastasis, tumor cells break away from the primary tumor, enter the blood and the lymph vessels, and use them as highways to travel to distant sites in the body to form secondary tumors. Cancer cell migration through the endothelium and into the basement membrane represents a critical step in the metastatic cascade, yet it is not well understood. This process is well characterized for immune cells that routinely transmigrate through the endothelium to sites of infection, inflammation, or injury. Previous studies with leukocytes have demonstrated that this step depends heavily on the activation status of the endothelium and subendothelial substrate stiffness. Here, we used a previously established in vitro model of the endothelium and live cell imaging, in order to observe cancer cell transmigration and compare this process to leukocytes. Interestingly, cancer cell transmigration includes an additional step, which we term ‘incorporation’, into the endothelial cell (EC) monolayer. During this phase, cancer cells physically displace ECs, leading to the dislocation of EC VE-cadherin away from EC junctions bordering cancer cells, and spread into the monolayer. In some cases, ECs completely detach from the matrix. Furthermore, cancer cell incorporation occurs independently of the activation status and the subendothelial substrate stiffness for breast cancer and melanoma cells, a notable difference from the process by which leukocytes transmigrate. Meanwhile, pancreatic cancer cell incorporation was dependent on the activation status of the endothelium and changed on very stiff subendothelial substrates. Collectively, our results provide mechanistic insights into tumor cell extravasation and demonstrate that incorporation is one of the earliest steps.

Sox18 preserves the pulmonary endothelial barrier under conditions of increased shear stress

Shear stress secondary to increased pulmonary blood flow (PBF) is elevated in some children born with congenital cardiac abnormalities. However, the majority of these patients do not develop pulmonary edema, despite high levels of permeability inducing factors. Previous studies have suggested that laminar fluid shear stress can enhance pulmonary vascular barrier integrity. However, little is known about the mechanisms by which this occurs. Using microarray analysis, we have previously shown that Sox18, a transcription factor involved in blood vessel development and endothelial barrier integrity, is up-regulated in an ovine model of congenital heart disease with increased PBF (shunt). By subjecting ovine pulmonary arterial endothelial cells (PAEC) to laminar flow (20 dyn/cm(2) ), we identified an increase in trans-endothelial resistance (TER) across the PAEC monolayer that correlated with an increase in Sox18 expression. Further, the TER was also enhanced when Sox18 was over-expressed and attenuated when Sox18 expression was reduced, suggesting that Sox18 maintains the endothelial barrier integrity in response to shear stress. Further, we found that shear stress up-regulates the cellular tight junction protein, Claudin-5, in a Sox18 dependent manner, and Claudin-5 depletion abolished the Sox18 mediated increase in TER in response to shear stress. Finally, utilizing peripheral lung tissue of 4 week old shunt lambs with increased PBF, we found that both Sox18 and Claudin-5 mRNA and protein levels were elevated. In conclusion, these novel findings suggest that increased laminar flow protects endothelial barrier function via Sox18 dependent up-regulation of Claudin-5 expression.