Phenotypic and functional differences between human saphenous vein (HSVEC) and umbilical vein (HUVEC) endothelial cells

Maternal administration of APAP induces angiogenesis disorders in mouse placenta via SOCS3/JAK1/STAT3 pathway

Acetaminophen (APAP, also known as paracetamol) is a commonly used antipyretic and analgesic that is considered safe to use during pregnancy. However, a growing body of research indicates that gestational administration of APAP increased the risk of neurodevelopmental, reproductive and genitourinary disorders in offspring, alongside impairments in placental development. Notably, over-dosed APAP exhibits direct toxicity to endothelial cells, but there is very limited research investigating the impact of APAP on placental angiogenesis, a gap we aim to address in this study. Pregnant mice were gavaged with APAP (15, 50 and 150 mg/kg/d) from embryonic day 11.5 (E11.5) to E13.5. Administration of 150 mg/kg/d APAP leads to low birth weight (LBW) of the offspring and disordered vascular structures within the labyrinthine (Lab) layer of the placenta. This disruption is accompanied by a significant increase in Suppressor of Cytokine Signaling 3 (SOCS3) level, a negative regulator of the Janus kinase signal transducer 1 and activator of the transcription 3 (JAK1/STAT3) signaling. Meanwhile, Human umbilical vein endothelial Cells (HUVECs) with the treatment of 3 mM APAP exhibited reduced cell viability, whereas 1 mM APAP significantly affected the proliferation, migration, invasion and angiogenic capacities of HUVECs. Further, SOCS3 was up-regulated in HUVECs, accompanied by inhibition of JAK1/STAT3 pathways. Knocking-down SOCS3 in HUVECs restored the nuclear translocation of STAT3 and efficiently promoted cellular capacity of tube formation. Overall, short-term maternal administration of overdosed APAP impairs angiogenic capacities of fetal endothelial cells via SOCS3/JAK1/STAT3 pathway in the mouse placenta. This study reveals that overdose of APAP during pregnancy may adversely affect placental angiogenesis, emphasizing the importance of adhering to the safe principles of smallest effective dose for the shortest required durations.

(R,S)-Equol 7-β-D-glucuronide, but not other circulating isoflavone metabolites, modulates migration and tubulogenesis in human aortic endothelial cells targeting the VEGF pathway

Current knowledge indicates that the consumption of isoflavone-rich foodstuffs can have a beneficial impact on cardiovascular health. To what extent these isoflavones act as the main actors of that benefit is less clear. Genistein (GEN), daidzein (DAZ), and the DAZ-derived microbial metabolite equol (Eq) exhibit antiangiogenic effects in vitro, but their low bloodstream concentrations make it difficult to rationalize the in vivo effects. Their derived phase-II metabolites (glucuronides and sulfates) are major metabolites found in plasma, but their role as antiangiogenic molecules remains unexplored. We aimed here to first assess the anti-angiogenic activities of the main circulating isoflavone metabolites (glucuronides and sulfates) and compare them with their corresponding free forms at physiological concentrations (0.1-10 μM). The effects of the conjugated vs. free forms on tubulogenesis, cell migration, and VEGF-induced signalling were investigated in primary human aortic endothelial cells (HAECs). While (R,S)-equol 7-β-D-glucuronide (Eq 7-glur) exerted dose-dependent inhibition of tubulogenesis and endothelial migration comparable to that exerted by the free forms (GEN, DAZ, and Eq), the rest of the phase-II conjugates exhibited no significant effects. The underlying molecular mechanisms were independent of the bFGF but related to the modulation of the VEGF pathway. Besides, the observed dissimilar cellular metabolism (conjugation/deconjugation) places the phase-II metabolites as precursors of the free forms; however, the question of whether this metabolism impacts their biological activity requires additional studies. These new insights suggest that isoflavones and their circulating metabolites, including Eq 7-glur, may be involved in cardiovascular health (e.g., targeting angiogenesis).

SEMA3G regulates BMP9 inhibition of VEGF-mediated migration and network formation in pulmonary endothelial cells

AIMS

Bone morphogenetic protein-9 (BMP9) is critical for bone morphogenetic protein receptor type-2 (BMPR2) signalling in pulmonary vascular endothelial cells. Furthermore, human genetics studies support the central role of disrupted BMPR2 mediated BMP9 signalling in vascular endothelial cells in the initiation of pulmonary arterial hypertension (PAH). In addition, loss-of-function mutations in BMP9 have been identified in PAH patients. BMP9 is considered to play an important role in vascular homeostasis and quiescence.

METHODS AND RESULTS

We identified a novel BMP9 target as the class-3 semaphorin, SEMA3G. Although originally identified as playing a role in neuronal development, class-3 semaphorins may have important roles in endothelial function. Here we show that BMP9 transcriptional regulation of SEMA3G occurs via ALK1 and the canonical Smad pathway, requiring both Smad1 and Smad5. Knockdown studies demonstrated redundancy between type-2 receptors in that BMPR2 and ACTR2A were compensatory. Increased SEMA3G expression by BMP9 was found to be regulated by the transcription factor, SOX17. Moreover, we observed that SEMA3G regulates VEGF signalling by inhibiting VEGFR2 phosphorylation and that VEGF, in contrast to BMP9, negatively regulated SEMA3G transcription. Functional endothelial cell assays of VEGF-mediated migration and network formation revealed that BMP9 inhibition of VEGF was abrogated by SEMA3G knockdown. Conversely, treatment with recombinant SEMA3G partially mimicked the inhibitory action of BMP9 in these assays.

CONCLUSIONS

This study provides further evidence for the anti-angiogenic role of BMP9 in microvascular endothelial cells and these functions are mediated at least in part via SOX17 and SEMA3G induction.

Isolation and Characterization of Porcine Endocardial Endothelial Cells

The heart contains diverse endothelial cell types. We sought to characterize the endocardial endothelial cells (EECs), which line the chambers of the heart. EECs are relatively understudied, yet their dysregulation can lead to various cardiac pathologies. Due to the lack of commercial availability of these cells, we reported our protocol for isolating EECs from porcine hearts and for establishing an EEC population through cell sorting. In addition, we compared the EEC phenotype and fundamental behaviors to a well-studied endothelial cell line, human umbilical vein endothelial cells (HUVECs). The EECs stained positively for classic phenotypic markers such as CD31, von Willebrand Factor, and vascular endothelial (VE) cadherin. The EECs proliferated more quickly than HUVECs at 48 h (1310 ± 251 cells vs. 597 ± 130 cells, p = 0.0361) and at 96 h (2873 ± 257 cells vs. 1714 ± 342 cells, p = 0.0002). Yet EECs migrated more slowly than HUVECs to cover a scratch wound at 4 h (5% ± 1% wound closure vs. 25% ± 3% wound closure, p < 0.0001), 8 h (15% ± 4% wound closure vs. 51% ± 12% wound closure, p < 0.0001), and 24 h (70% ± 11% wound closure vs. 90% ± 3% wound closure, p < 0.0001). Finally, the EECs maintained their endothelial phenotype by positive expression of CD31 through more than a dozen passages (three populations of EECs showing 97% ± 1% CD31+ cells in over 14 passages). In contrast, the HUVECs showed significantly reduced CD31 expression over high passages (80% ± 11% CD31+ cells over 14 passages). These important phenotypic differences between EECs and HUVECs highlight the need for researchers to utilize the most relevant cell types when studying or modeling diseases of interest.

PLCL/PCL Dressings with Platelet Lysate and Growth Factors Embedded in Fibrin for Chronic Wound Regeneration

Introduction

The formation of diabetic ulcers (DU) is a common complication for diabetic patients resulting in serious chronic wounds. There is therefore, an urgent need for complex treatment of this problem. This study examines a bioactive wound dressing of a biodegradable electrospun nanofibrous blend of poly(L-lactide-co-ε-caprolactone) and poly(ε-caprolactone) (PLCL/PCL) covered by a thin fibrin layer for sustained delivery of bioactive molecules.

Methods

Electrospun PLCL/PCL nanofibers were coated with fibrin-based coating prepared by a controlled technique and enriched with human platelet lysate (hPL), fibroblast growth factor 2 (FGF), and vascular endothelial growth factor (VEGF). The coating was characterized by scanning electron microscopy and fluorescent microscopy. Protein content and its release rate and the effect on human saphenous vein endothelial cells (HSVEC) were evaluated.

Results

The highest protein amount is achieved by the coating of PLCL/PCL with a fibrin mesh containing 20% v/v hPL (NF20). The fibrin coating serves as an excellent scaffold to accumulate bioactive molecules from hPL such as PDGF-BB, fibronectin (Fn), and α-2 antiplasmin. The NF20 coating shows both fast and a sustained release of the attached bioactive molecules (Fn, VEGF, FGF). The dressing significantly increases the viability of human saphenous vein endothelial cells (HSVECs) cultivated on a collagen-based wound model. The exogenous addition of FGF and VEGF during the coating procedure further increases the HSVECs viability. In addition, the presence of α-2 antiplasmin significantly stabilizes the fibrin mesh and prevents its cleavage by plasmin.

Discussion

The NF20 coating supplemented with FGF and VEGF provides a promising wound dressing for the complex treatment of DU. The incorporation of various bioactive molecules from hPL and growth factors has great potential to support the healing processes by providing appropriate stimuli in the chronic wound.

Endothelial senescence in vascular diseases: current understanding and future opportunities in senotherapeutics

Senescence compromises the essential role that the endothelium plays in maintaining vascular homeostasis, so promoting endothelial dysfunction and the development of age-related vascular diseases. Their biological and clinical significance calls for strategies for identifying and therapeutically targeting senescent endothelial cells. While senescence and endothelial dysfunction have been studied extensively, distinguishing what is distinctly endothelial senescence remains a barrier to overcome for an effective approach to addressing it. Here, we review the mechanisms underlying endothelial senescence and the evidence for its clinical importance. Furthermore, we discuss the current state and the limitations in the approaches for the detection and therapeutic intervention of target cells, suggesting potential directions for future research.

Physiologically relevant curcuminoids inhibit angiogenesis via VEGFR2 in human aortic endothelial cells

Angiogenesis is a complex process encompassing endothelial cell proliferation, migration, and tube formation. While numerous studies describe that curcumin exerts antitumor properties (e.g., targeting angiogenesis), information regarding other dietary curcuminoids such as demethoxycurcumin (DMC) and bisdemethoxycurcumin (BisDMC) is scant. In this study, we evaluated the antiangiogenic activities of these three curcuminoids at physiological concentrations (0.1-5 μM) on endothelial cell migration and tubulogenesis and the underlying associated mechanisms on human aortic endothelial cells (HAECs). Results showed that the individual compounds and a representative mixture inhibited the tubulogenic and migration capacity of endothelial cells dose-dependently, while sparing cell viability. Notably, DMC and BisDMC at 0.1 and 1 μM showed higher capacity than curcumin inhibiting tubulogenesis. These compounds also reduced phosphorylation of the VEGFR2 and the downstream ERK and Akt pathways in VEGF₁₆₅-stimulated cells. In silico analysis showed that curcuminoids could bind the VEGFR2 antagonizing the VEGF-mediated angiogenesis. These findings suggest that physiologically concentrations of curcuminoids might counteract pro-angiogenic stimuli relevant to tumorigenic processes.

Immunomodulation by endothelial cells - partnering up with the immune system?

Blood vessel endothelial cells (ECs) have long been known to modulate inflammation by regulating immune cell trafficking, activation status and function. However, whether the heterogeneous EC populations in various tissues and organs differ in their immunomodulatory capacity has received insufficient attention, certainly with regard to considering them for alternative immunotherapy. Recent single-cell studies have identified specific EC subtypes that express gene signatures indicative of phagocytosis or scavenging, antigen presentation and immune cell recruitment. Here we discuss emerging evidence suggesting a tissue-specific and vessel type-specific immunomodulatory role for distinct subtypes of ECs, here collectively referred to as 'immunomodulatory ECs' (IMECs). We propose that IMECs have more important functions in immunity than previously recognized, and suggest that these might be considered as targets for new immunotherapeutic approaches.

Bioprinted microvasculature: progressing from structure to function

Three-dimensional (3D) bioprinting seeks to unlock the rapid generation of complex tissue constructs, but long-standing challenges with efficientin vitromicrovascularization must be solved before this can become a reality. Microvasculature is particularly challenging to biofabricate due to the presence of a hollow lumen, a hierarchically branched network topology, and a complex signaling milieu. All of these characteristics are required for proper microvascular-and, thus, tissue-function. While several techniques have been developed to address distinct portions of this microvascularization challenge, no single approach is capable of simultaneously recreating all three microvascular characteristics. In this review, we present a three-part framework that proposes integration of existing techniques to generate mature microvascular constructs. First, extrusion-based 3D bioprinting creates a mesoscale foundation of hollow, endothelialized channels. Second, biochemical and biophysical cues induce endothelial sprouting to create a capillary-mimetic network. Third, the construct is conditioned to enhance network maturity. Across all three of these stages, we highlight the potential for extrusion-based bioprinting to become a central technique for engineering hierarchical microvasculature. We envision that the successful biofabrication of functionally engineered microvasculature will address a critical need in tissue engineering, and propel further advances in regenerative medicine andex vivohuman tissue modeling.

Tumors resurrect an embryonic vascular program to escape immunity

[Figure: see text].

Total parasite biomass but not peripheral parasitaemia is associated with endothelial and haematological perturbations in Plasmodium vivax patients

Plasmodium vivax is the major cause of human malaria in the Americas. How P. vivax infection can lead to poor clinical outcomes, despite low peripheral parasitaemia, remains a matter of intense debate. Estimation of total P. vivax biomass based on circulating markers indicates existence of a predominant parasite population outside of circulation. In this study, we investigate associations between both peripheral and total parasite biomass and host response in vivax malaria. We analysed parasite and host signatures in a cohort of uncomplicated vivax malaria patients from Manaus, Brazil, combining clinical and parasite parameters, multiplexed analysis of host responses, and ex vivo assays. Patterns of clinical features, parasite burden, and host signatures measured in plasma across the patient cohort were highly heterogenous. Further data deconvolution revealed two patient clusters, here termed Vivax^low and Vivax^high. These patient subgroups were defined based on differences in total parasite biomass but not peripheral parasitaemia. Overall Vivax^low patients clustered with healthy donors and Vivax^high patients showed more profound alterations in haematological parameters, endothelial cell (EC) activation, and glycocalyx breakdown and levels of cytokines regulating different haematopoiesis pathways compared to Vivax^low. Vivax^high patients presented more severe thrombocytopenia and lymphopenia, along with enrichment of neutrophils in the peripheral blood and increased neutrophil-to-lymphocyte ratio (NLCR). When patients' signatures were combined, high association of total parasite biomass with a subset of markers of EC activation, thrombocytopenia, and lymphopenia severity was observed. Finally, machine learning models defined a combination of host parameters measured in the circulation that could predict the extent of parasite infection outside of circulation. Altogether, our data show that total parasite biomass is a better predictor of perturbations in host homeostasis in P. vivax patients than peripheral parasitaemia. This supports the emerging paradigm of a P. vivax tissue reservoir, particularly in the haematopoietic niche of bone marrow and spleen.

Comparative Evaluation on Impacts of Fibronectin, Heparin-Chitosan, and Albumin Coating of Bacterial Nanocellulose Small-Diameter Vascular Grafts on Endothelialization In Vitro

In this study, we contrast the impacts of surface coating bacterial nanocellulose small-diameter vascular grafts (BNC-SDVGs) with human albumin, fibronectin, or heparin–chitosan upon endothelialization with human saphenous vein endothelial cells (VEC) or endothelial progenitor cells (EPC) in vitro. In one scenario, coated grafts were cut into 2D circular patches for static colonization of a defined inner surface area; in another scenario, they were mounted on a customized bioreactor and subsequently perfused for cell seeding. We evaluated the colonization by emerging metabolic activity and the preservation of endothelial functionality by water soluble tetrazolium salts (WST-1), acetylated low-density lipoprotein (AcLDL) uptake assays, and immune fluorescence staining. Uncoated BNC scaffolds served as controls. The fibronectin coating significantly promoted adhesion and growth of VECs and EPCs, while albumin only promoted adhesion of VECs, but here, the cells were functionally impaired as indicated by missing AcLDL uptake. The heparin–chitosan coating led to significantly improved adhesion of EPCs, but not VECs. In summary, both fibronectin and heparin–chitosan coatings could beneficially impact the endothelialization of BNC-SDVGs and might therefore represent promising approaches to help improve the longevity and reduce the thrombogenicity of BNC-SDVGs in the future.

Induced Pluripotent Stem Cell-Derived Endothelial Networks Accelerate Vascularization But Not Bone Regeneration

Vascularization is critical for engineering mineralized tissues. It has been previously shown that biomaterials containing preformed endothelial networks anastomose to host vasculature following implantation. However, the networks alone may not increase regeneration. In addition, a clinically applicable source of cells for vascularization is needed. In this study, vascular networks were generated from endothelial cells (ECs) derived from human induced pluripotent stem cells (iPSCs). Network formation by iPSC-ECs within fibrin gels was investigated in a mesenchymal stem cells (MSCs) coculture spheroid model. Statistical design of experiments technique was evaluated for its predicting capability during the optimization of experimental parameters. The prevascularized units were combined with hydroxyapatite nanoparticles to develop a vascularized composite hydrogel that was implanted in a rodent critical-sized cranial defect model. Immunohistological staining for human-specific CD31 at week 1 indicated the presence and maintenance of the implanted vessels. At 8 weeks, the prevascularized systems resulted in higher vessel density over MSC-only scaffolds. The implanted vessels appeared to establish flow with host vasculature. While there was a slight increase in bone volume in the prevascularized bone construct compared to MSC-only bone constructs, there was not a profound increase in bone regeneration. These results show that scaffolds with network structures can be generated from ECs derived from iPSC and that the networks survive and inosculate with the host postimplantation in a bone model. Impact statement Vascularization is critical for engineering bone. Prevascularized scaffolds have been shown to improve postimplantation vascularization. Herein, vascularized networks were generated from induced pluripotent cells derived from endothelial cells. These vascularized units were combined with a fibrin/hydroxyapatite scaffold to develop a prevascularized construct for bone regeneration. Implantation of these scaffolds in a small animal cranial defect model resulted in network inosculation and increased vascularization, but exhibited only a limited effect on bone formation. This study provides insight into the challenges of generating vascularized bone.

Vascular Metabolism as Driver of Atherosclerosis: Linking Endothelial Metabolism to Inflammation

The endothelium is a crucial regulator of vascular homeostasis by controlling barrier integrity as well acting as an important signal transducer, thereby illustrating that endothelial cells are not inert cells. In the context of atherosclerosis, this barrier function is impaired and endothelial cells become activated, resulting in the upregulation of adhesion molecules, secretion of cytokines and chemokines and internalization of integrins. Finally, this leads to increased vessel permeability, thereby facilitating leukocyte extravasation as well as fostering a pro-inflammatory environment. Additionally, activated endothelial cells can form migrating tip cells and proliferative stalk cells, resulting in the formation of new blood vessels. Emerging evidence has accumulated indicating that cellular metabolism is crucial in fueling these pro-atherosclerotic processes, including neovascularization and inflammation, thereby contributing to plaque progression and altering plaque stability. Therefore, further research is necessary to unravel the complex mechanisms underlying endothelial cell metabolic changes, and exploit this knowledge for finding and developing potential future therapeutic strategies. In this review we discuss the metabolic alterations endothelial cells undergo in the context of inflammation and atherosclerosis and how this relates to changes in endothelial functioning. Finally, we will describe several metabolic targets that are currently being used for therapeutic interventions.

ICOSL in host defense at epithelial barriers: lessons from ICOSLG deficiency

Autosomal recessive mutations in Inducible T Cell Costimulator Ligand (ICOSLG) result in a combined immunodeficiency syndrome of humans, saliently marked by recurrent respiratory tract infections and significant disease with DNA-based viruses at epithelial barriers, including human papillomavirus (HPV). These features are also seen in persons with loss of function of the complementary gene, ICOS. The infection phenotypes associated with these natural experiments disclose a critical role of the corresponding proteins, ICOSL and ICOS, in human immunity at mucocutaneous barriers. Here, we review the syndromes of ICOSL and ICOS deficiency and explore the mechanisms by which the ICOSL:ICOS axis mediates epithelial host defenses.

Advanced in vitro Research Models to Study the Role of Endothelial Cells in Solid Organ Transplantation

The endothelium plays a key role in acute and chronic rejection of solid organ transplants. During both processes the endothelium is damaged often with major consequences for organ function. Also, endothelial cells (EC) have antigen-presenting properties and can in this manner initiate and enhance alloreactive immune responses. For decades, knowledge about these roles of EC have been obtained by studying both in vitro and in vivo models. These experimental models poorly imitate the immune response in patients and might explain why the discovery and development of agents that control EC responses is hampered. In recent years, various innovative human 3D in vitro models mimicking in vivo organ structure and function have been developed. These models will extend the knowledge about the diverse roles of EC in allograft rejection and will hopefully lead to discoveries of new targets that are involved in the interactions between the donor organ EC and the recipient's immune system. Moreover, these models can be used to gain a better insight in the mode of action of the currently prescribed immunosuppression and will enhance the development of novel therapeutics aiming to reduce allograft rejection and prolong graft survival.

The suppressive effect on CD4 T cell alloresponse against endothelial HLA-DR via PD-L1 induced by anti-A/B ligation

While donor-specific human leukocyte antigen (HLA) antibodies are a frequent cause for chronic antibody-mediated rejection in organ transplantation, this is not the case for antibodies targeting blood group antigens, as ABO-incompatible (ABO-I) organ transplantation has been associated with a favorable graft outcome. Here, we explored the role of CD4 T cell-mediated alloresponses against endothelial HLA-D-related (DR) in the presence of anti-HLA class I or anti-A/B antibodies. CD4 T cells, notably CD45RA-memory CD4 T cells, undergo extensive proliferation in response to endothelial HLA-DR. The CD4 T cell proliferative response was enhanced in the presence of anti-HLA class I, but attenuated in the presence of anti-A/B antibodies. Microarray analysis and molecular profiling demonstrated that the expression of CD274 programmed cell death ligand 1 (PD-L1) increased in response to anti-A/B ligation-mediated extracellular signal-regulated kinase (ERK) inactivation in endothelial cells that were detected even in the presence of interferon-γ stimulation. Anti-PD-1 antibody enhanced CD4 T cell proliferation, and blocked the suppressive effect of the anti-A/B antibodies. Educated CD25⁺ CD127^- regulatory T cells (edu.T_regs ) were more effective at preventing CD4 T cell alloresponses to endothelial cells compared with naive T_reg ; anti-A/B antibodies were not involved in the T_reg -mediated events. Finally, amplified expression of transcript encoding PD-L1 was observed in biopsy samples from ABO-I renal transplants when compared with those from ABO-identical/compatible transplants. Taken together, our findings identified a possible factor that might prevent graft rejection and thus contribute to a favorable outcome in ABO-I renal transplantation.

MicroRNA-200a Inhibits Inflammation and Atherosclerotic Lesion Formation by Disrupting EZH2-Mediated Methylation of STAT3

Endothelial inflammation and dysfunction are critical to the process of atherosclerosis. Emerging evidence demonstrates that upregulation of miR-200a reduces VCAM-1 expression and prevents monocytic cell adhesion onto the aortic endothelium. However, limited information is available about the role of microRNA-200a (miR-200a) in facilitating atherosclerotic lesion formation. We investigated the anti-inflammatory and anti-atherosclerotic actions of miR-200a. Human umbilical vein endothelial cells (HUVECs) were cultured in the presence of oxidized low-density lipoprotein (ox-LDL), and their viability and apoptosis were evaluated using CCK-8 assays and flow cytometric analysis. The enhancer of zeste homolog 2 (EZH2) promoter activity was evaluated in the presence of miR-200a by dual luciferase reporter gene assay. EZH2-mediated methylation of signal transducer and activator of transcription 3 (STAT3) was validated by ChIP and IP assays. ApoE-/- mice were given a 12-week high-fat diet and developed as in vivo atherosclerotic models. miR-200a was downregulated but EZH2 and HMGB1 were upregulated in ox-LDL-treated HUVECs and the aorta tissues of atherosclerotic mouse models. Elevated miR-200a was shown to protect HUVECs against ox-LDL-induced apoptosis and inflammation. EZH2 was verified as a target of miR-200a. The protective effects of miR-200a were abrogated upon an elevation of EZH2. EZH2 methylated STAT3 and enhanced STAT3 activity by increased tyrosine phosphorylation of STAT3, thereby increasing apoptosis and release of pro-inflammatory cytokines in ox-LDL-treated HUVECs. An anti-atherosclerotic role of miR-200a was also demonstrated in atherosclerotic mouse models. Our study demonstrates that miR-200a has anti-inflammatory and anti-atherosclerotic activities dependent on the EZH2/STAT3 signaling cascade.

Human lung microvascular endothelial cells as potential alternatives to human umbilical vein endothelial cells in bio-3D-printed trachea-like structures

BACKGROUND

We have been trying to produce scaffold-free structures for airway regeneration using a bio-3D-printer with spheroids, to avoid scaffold-associated risks such as infection. Previous studies have shown that human umbilical vein endothelial cells (HUVECs) play an important role in such structures, but HUVECs cannot be isolated from adult humans. The aim of this study was to identify alternatives to HUVECs for use in scaffold-free structures.

METHODS

Three types of structure were compared, made of chondrocytes and mesenchymal stem cells with HUVECs, human lung microvascular endothelial cells (HMVEC-Ls), and induced pluripotent stem cell (iPSC)-derived endothelial cells.

RESULTS

No significant difference in tensile strength was observed between the three groups. Histologically, some small capillary-like tube formations comprising CD31-positive cells were observed in all groups. The number and diameters of such formations were significantly lower in the iPSC-derived endothelial cell group than in other groups. Glycosaminoglycan content was significantly lower in the iPSC-derived endothelial cell group than in the HUVEC group, while no significant difference was observed between the HUVEC and HMVEC-L groups.

CONCLUSIONS

HMVEC-Ls can replace HUVECs as a cell source for scaffold-free trachea-like structures. However, some limitations were associated with iPSC-derived endothelial cells.

Methylglyoxal down-regulates the expression of cell cycle associated genes and activates the p53 pathway in human umbilical vein endothelial cells

Although methylglyoxal (MGO) has emerged as key mediator of diabetic microvascular complications, the influence of MGO on the vascular transcriptome has not thoroughly been assessed. Since diabetes is associated with low grade inflammation causing sustained nuclear factor-kappa B (NF-κB) activation, the current study addressed 1) to what extent MGO changes the transcriptome of human umbilical vein endothelial cells (HUVECs) exposed to an inflammatory milieu, 2) what are the dominant pathways by which these changes occur and 3) to what extent is this affected by carnosine, a putative scavenger of MGO. Microarray analysis revealed that exposure of HUVECs to high MGO concentrations significantly changes gene expression, characterized by prominent down-regulation of cell cycle associated genes and up-regulation of heme oxygenase-1 (HO-1). KEGG-based pathway analysis identified six significantly enriched pathways of which the p53 pathway was the most affected. No significant enrichment of inflammatory pathways was found, yet, MGO did inhibit VCAM-1 expression in Western blot analysis. Carnosine significantly counteracted MGO-mediated changes in a subset of differentially expressed genes. Collectively, our results suggest that MGO initiates distinct transcriptional changes in cell cycle/apoptosis genes, which may explain MGO toxicity at high concentrations. MGO did not augment TNF-α induced inflammation.

RSPO3 impairs barrier function of human vascular endothelial monolayers and synergizes with pro-inflammatory IL-1

BACKGROUND

Endothelial barrier dysfunction characterized by hyperpermeability of the vascular endothelium is a key factor in the pathogenesis of chronic inflammatory diseases and affects clinical outcomes. In states of chronic inflammation, mediators secreted by activated immune cells or vascular endothelium may affect the barrier function and permeability of the vascular endothelium. The matricellular R-spondin family member RSPO3 is produced by inflammatory-activated human monocytes and vascular endothelial cells, but its effects in the regulation of vascular endothelial barrier function remains elusive.

METHODS

The present study investigates the effects of RSPO3 on the barrier function of adult human primary macro- and micro- vascular endothelial monolayers. Tight monolayers of primary endothelial cells from human coronary and pulmonary arteries, and cardiac, brain, and dermal microvascular beds were treated with RSPO3 either alone or in combination with pro-inflammatory mediator IL-1β. Endothelial barrier function was assessed non-invasively in real-time using Electric Cell-substrate Impedance Sensing.

RESULTS

RSPO3 treatment critically affected barrier function by enhancing the permeability of all vascular endothelial monolayers investigated. To confer hyperpermeable phenotype in vascular endothelial monolayers, RSPO3 induced inter-endothelial gap formation by disrupting the β-catenin and VE-cadherin alignment at adherens junctions. RSPO3 synergistically enhanced the barrier impairing properties of the pro-inflammatory mediator IL-1β.

CONCLUSION

Here, we show that the matricellular protein RSPO3 is a mediator of endothelial hyperpermeability that can act in synergy with the inflammatory mediator IL-1β. This finding stimulates further studies to delineate the endothelial barrier impairing properties of RSPO3 and its synergistic interaction with IL-1β in chronic inflammatory diseases.

Anti-endothelial cell antibody rich sera from rheumatic heart disease patients induces proinflammatory phenotype and methylation alteration in endothelial cells

Rheumatic heart disease (RHD) is a major cause of cardiovascular morbidity and mortality in developing nations like India. RHD commonly affects the mitral valve which is lined by a single layer of endothelial cells (ECs). The role of ECs in mitral valve damage during RHD is not well elucidated. In here, anti-endothelial cell antibody from RHD patients has been used to stimulate the ECs (HUVECs and HMVECs). ECs proinflammatory phenotype with increased expression of TNFα, IL-6, IL-8, IFNγ, IL-1β, ICAM1, VCAM1, E-selectin, laminin B, and vimentin was documented in both ECs. The promoter hypomethylation of various key inflammatory cytokines (TNFα, IL-6, and IL-8), integrin (ICAM1) associated with leukocyte transendothelial migration, and extracellular matrix genes (vimentin, and laminin) were also observed. Further, the in-vitro data was in accordance with ex-vivo observations which correlated significantly with the etiological factors such as smoking, socioeconomic status, and housing. Thus, the study sheds light on the role of ECs in RHD which is a step forward in the elucidation of disease pathogenesis.

Investigation of quercetin and hyperoside as senolytics in adult human endothelial cells

Quercetin has been reported to act as a senolytic by selectively removing senescent endothelial cells, and thus it would seem quercetin could revolutionize the field of gerontology. However, given quercetin's narrow therapeutic index reported in work done with human umbilical vein endothelial cells (HUVECs), we hypothesized that quercetin is not innocuous for non-senescent adult human vascular endothelial cells at concentrations that have been reported to be safe for proliferating HUVECs. Furthermore, we investigated quercetin 3-D-galactoside (Q3G; hyperoside), an inactive quercetin derivative that needs to be cleaved by beta-galactosidase overexpressed in senescent cells to release quercetin, as a potential safer senolytic. We compared the effectiveness of quercetin and Q3G in primary human coronary artery endothelial cells (HCAEC), which are adult microvascular cells. We found that quercetin caused cell death in non-senescent endothelial cells at a concentration that has been reported to selectively remove senescent cells, and that Q3G was not cytotoxic to either young or senescent cells. Thus, in primary adult human endothelial cells, quercetin and Q3G are not senolytics. Earlier work reporting positive results was done with HUVECs, and given their origin and the disparate findings from the current study, these may not be the best cells for evaluating potential senolytics in clinically relevant endothelial cells.

Antigen Presentation by Vascular Cells

Antigen presentation by cells of the vessel wall may initiate rapid and localized memory immune responses in peripheral tissues. Peptide antigens displayed on major histocompatibility complex (MHC) molecules on the surface of endothelial cells (ECs) can be recognized by T cell receptors on circulating effector memory T cells (T_EM), triggering both transendothelial migration and activation. The array of co-stimulatory receptors, adhesion molecules, and cytokines expressed by ECs serves to modulate T cell activation responses. While the effects of these interactions vary among species, vascular beds, and vascular segments within the same tissue, they are capable of triggering allograft rejection without direct involvement of professional antigen-presenting cells and may play a similar role in host defense against infections and in autoimmunity. Once across the endothelium, extravasating T_EM then contact mural cells of the vessel wall, including pericytes or vascular smooth muscle cells, which may also present antigens and provide signals that further regulate T cell responses. Collectively, these interactions provide an unexplored opportunity in which targeting of vascular cells can be used to modulate immune responses. In organ transplantation, targeting ECs with siRNA to reduce expression of MHC molecules may additionally mitigate perioperative injuries by preformed alloantibodies, further reducing the risk of graft rejection. Similarly, genetic manipulation of vascular cells to minimize antigen-dependent responses can be used to increase perfusion of tissue engineered organs without triggering rejection.

Vitamin D suppresses oxidative stress-induced microparticle release by human umbilical vein endothelial cells

Endothelial microparticle (MP) release was increased in numerous cardiovascular diseases including preeclampsia. Oxidative stress is a potent inducer of endothelial dysfunction. In this study, we aimed to investigate if vitamin D could protect endothelial cells (ECs) from MP release induced by oxidative stress. Endothelial cell (from human umbilical vein) oxidative stress was induced by cultivation of cells under lowered oxygen condition (2%O2) for 48 h and cells cultured under standard condition (21%O2) served as control. 1,25(OH)2D3 was used as bioactive vitamin D. Using annexin-V as a marker of released MP assessed by flow cytometry and cytochrome c reduction assay to measure EC superoxide generation, we found that MP release and superoxide generation were significantly increased when cells were cultured under 2%O2, which could be significantly inhibited by 1,25(OH)2D3. To study the potential mechanisms of 1,25(OH)2D3 protective effects on ECs, EC expression of endothelial nitric oxide synthase (eNOS), p-eNOSSer1177, p-eNOSThr495, caveolin-1, extracellular signal-regulated kinase (ERK), p-ERK, Akt, p-AktSer473, Rho-associated coiled-coil protein kinase 1 (ROCK1), and vitamin D receptor were determined. Microparticle expression of eNOS and caveolin-1 were also determined. We found that under lowered oxygen condition, 1,25(OH)2D3 could upregulate EC eNOS, p-eNOSSer1177, and p-AktSer473 expression, but inhibit cleaved ROCK1 expression. The upregulatory and inhibitory effects induced by 1,25(OH)2D3 were dose dependent. Strikingly, we also found that oxidative stress-induced decrease in ratio of eNOS and caveolin-1 expression in MP could be attenuated when 1,25(OH)2D3 was present in culture. These results suggest that upregulation of eNOSSer1177 and AktSer473 phosphorylation and inhibition of ROCK1 cleavage in EC and modulation of eNOS and caveolin-1 expression in MP could be plausible mechanisms of vitamin D protective effects on ECs.

Vitamin D suppresses oxidative stress-induced microparticle release by human umbilical vein endothelial cells

Endothelial microparticle (MP) release was increased in numerous cardiovascular diseases including preeclampsia. Oxidative stress is a potent inducer of endothelial dysfunction. In this study, we aimed to investigate if vitamin D could protect endothelial cells (ECs) from MP release induced by oxidative stress. Endothelial cell (from human umbilical vein) oxidative stress was induced by cultivation of cells under lowered oxygen condition (2%O2) for 48 h and cells cultured under standard condition (21%O2) served as control. 1,25(OH)2D3 was used as bioactive vitamin D. Using annexin-V as a marker of released MP assessed by flow cytometry and cytochrome c reduction assay to measure EC superoxide generation, we found that MP release and superoxide generation were significantly increased when cells were cultured under 2%O2, which could be significantly inhibited by 1,25(OH)2D3. To study the potential mechanisms of 1,25(OH)2D3 protective effects on ECs, EC expression of endothelial nitric oxide synthase (eNOS), p-eNOSSer1177, p-eNOSThr495, caveolin-1, extracellular signal-regulated kinase (ERK), p-ERK, Akt, p-AktSer473, Rho-associated coiled-coil protein kinase 1 (ROCK1), and vitamin D receptor were determined. Microparticle expression of eNOS and caveolin-1 were also determined. We found that under lowered oxygen condition, 1,25(OH)2D3 could upregulate EC eNOS, p-eNOSSer1177, and p-AktSer473 expression, but inhibit cleaved ROCK1 expression. The upregulatory and inhibitory effects induced by 1,25(OH)2D3 were dose dependent. Strikingly, we also found that oxidative stress-induced decrease in ratio of eNOS and caveolin-1 expression in MP could be attenuated when 1,25(OH)2D3 was present in culture. These results suggest that upregulation of eNOSSer1177 and AktSer473 phosphorylation and inhibition of ROCK1 cleavage in EC and modulation of eNOS and caveolin-1 expression in MP could be plausible mechanisms of vitamin D protective effects on ECs.

Effect of Calcium-Infiltrated Hydroxyapatite Scaffolds on the Hematopoietic Fate of Human Umbilical Vein Endothelial Cells

Foamed hydroxyapatite offers a three-dimensional scaffold for the development of bone constructs, mimicking perfectly the in vivo bone structure. In vivo, calcium release at the surface is assumed to provide a locally increased gradient supporting the maintenance of the hematopoietic stem cells niche. We fabricated hydroxyapatite scaffolds with high surface calcium concentration by infiltration, and used human umbilical vein endothelial cells (HUVECs) as a model to study the effects on hematopoietic lineage direction. HUVECs are umbilical vein-derived and thus possess progenitor characteristics, with a prospective potential to give rise to hematopoietic lineages. HUVECs were cultured for long term on three-dimensional porous hydroxyapatite scaffolds, which were either infiltrated biphasic foams or untreated. Controls were cultured in two-dimensional dishes. The release of calcium into culture medium was determined, and cells were analyzed for typical hematopoietic and endothelial gene expressions, surface markers by flow cytometry, and hematopoietic potential using colony-forming unit assays. Our results indicate that the biphasic foams promoted a hematopoietic lineage direction of HUVECs, suggesting an improved in vivo-like scaffold for hematopoietic bone tissue engineering.

Upregulation of miR-126-3p promotes human saphenous vein endothelial cell proliferation in vitro and prevents vein graft neointimal formation ex vivo and in vivo

Poor long-term patency of vein grafts remains an obstacle in coronary artery bypass grafting (CABG) surgery using an autologous saphenous vein graft. Recent studies have revealed that miR-126-3p promotes vascular integrity and angiogenesis. We aimed to identify the role of miR-126-3p in the setting of vein graft disease and investigate the value of miR-126-3p agomir as a future gene therapy in vein graft failure. Expression analysis of circulating miR-126-3p in plasma from CABG patients established the basic clues that miR-126-3p participates in CABG. The in vitro results indicated that elevated miR-126-3p expression significantly improved proliferation and migration in human saphenous vein endothelial cells (HSVECs) by targeting sprouty-related protein-1 (SPRED-1) and phosphatidylinositol-3-kinase regulatory subunit 2 (PIK3R2), but not in human saphenous vein smooth muscle cells (HSVSMCs). Moreover, the therapeutic potential of miR-126-3p agomir was demonstrated in cultured human saphenous vein (HSV) ex vivo. Finally, local delivery of miR-126-3p agomir was confirmed to enhance reendothelialization and attenuate neointimal formation in a rat vein arterialization model. In conclusion, we provide evidence that upregulation of miR-126-3p by agomir possesses potential clinical value in the prevention and treatment of autologous vein graft restenosis in CABG.

IL-4 Causes Hyperpermeability of Vascular Endothelial Cells through Wnt5A Signaling

Microvascular leakage due to endothelial barrier dysfunction is a prominent feature of T helper 2 (Th2) cytokine mediated allergic inflammation. Interleukin-4 (IL-4) is a potent Th2 cytokine, known to impair the barrier function of endothelial cells. However, the effectors mediating IL-4 induced cytoskeleton remodeling and consequent endothelial barrier dysfunction remain poorly defined. Here we have used whole genome transcriptome profiling and gene ontology analyses to identify the genes and processes regulated by IL-4 signaling in human coronary artery endothelial cells (HCAEC). The study revealed Wnt5A as an effector that can mediate actin cytoskeleton remodeling in IL-4 activated HCAEC through the regulation of LIM kinase (LIMK) and Cofilin (CFL). Following IL-4 treatment, LIMK and CFL were phosphorylated, thereby indicating the possibility of actin stress fiber formation. Imaging of actin showed the formation of stress fibers in IL-4 treated live HCAEC. Stress fiber formation was notably decreased in the presence of Wnt inhibitory factor 1 (WIF1). Non-invasive impedance measurements demonstrated that IL-4 increased the permeability and impaired the barrier function of HCAEC monolayers. Silencing Wnt5A significantly reduced permeability and improved the barrier function of HCAEC monolayers upon IL-4 treatment. Our study identifies Wnt5A as a novel marker of IL-4 activated vascular endothelium and demonstrates a critical role for Wnt5A in mediating IL-4 induced endothelial barrier dysfunction. Wnt5A could be a potential therapeutic target for reducing microvascular leakage and edema formation in Th2 driven inflammatory diseases.

Hesperetin and its sulfate and glucuronide metabolites inhibit TNF-α induced human aortic endothelial cell migration and decrease plasminogen activator inhibitor-1 (PAI-1) levels

Hesperetin and its derived metabolites, at physiologically relevant concentrations, significantly attenuated TNF-α-induced cell migration.

Autologous cell sources in therapeutic vasculogenesis: In vitro and in vivo comparison of endothelial colony-forming cells from peripheral blood and endothelial cells isolated from adipose tissue

BACKGROUND AIMS

Autologous endothelial cells are promising alternative angiogenic cell sources in trials of therapeutic vasculogenesis, in the treatment of vascular diseases and in the field of tissue engineering. A population of endothelial cells (ECs) with long-term proliferative capability, endothelial colony-forming cells (ECFCs), can be isolated from human peripheral blood. ECFCs are considered an endothelial precursor population. They can be expanded in cell factories in sufficient numbers for clinical applications, but because the number of isolated primary ECs is low, the culture period required may be long. Another EC population that is easily available in the autologous setting and may be expanded in vitro through several population doublings are ECs from adipose tissue (AT-ECs).

METHODS

Through extensive comparisons using whole-genome microarray analysis, morphology, phenotype and functional assays, we wanted to evaluate the potential of these EC populations for use in clinical neovascularization.

RESULTS

Global gene expression profiling of ECFCs, AT-ECs and the classical EC population, human umbilical vein ECs, showed that the EC populations clustered as unique populations, but very close to each other. By cell surface phenotype and vasculogenic potential in vitro and in vivo, we also found the ECFCs to be extremely similar to AT-ECs.

CONCLUSIONS

These properties, together with easy access in the autologous setting, suggest that both AT-ECs and ECFCs may be useful in trials of therapeutic neovascularization. However, AT-ECs may be a more practical alternative for obtaining large quantities of autologous ECs.

Aberrant phenotype in human endothelial cells of diabetic origin: implications for saphenous vein graft failure?

Type 2 diabetes (T2DM) confers increased risk of endothelial dysfunction, coronary heart disease, and vulnerability to vein graft failure after bypass grafting, despite glycaemic control. This study explored the concept that endothelial cells (EC) cultured from T2DM and nondiabetic (ND) patients are phenotypically and functionally distinct. Cultured human saphenous vein- (SV-) EC were compared between T2DM and ND patients in parallel. Proliferation, migration, and in vitro angiogenesis assays were performed; western blotting was used to quantify phosphorylation of Akt, ERK, and eNOS. The ability of diabetic stimuli (hyperglycaemia, TNF-α, and palmitate) to modulate angiogenic potential of ND-EC was also explored. T2DM-EC displayed reduced migration (~30%) and angiogenesis (~40%) compared with ND-EC and a modest, nonsignificant trend to reduced proliferation. Significant inhibition of Akt and eNOS, but not ERK phosphorylation, was observed in T2DM cells. Hyperglycaemia did not modify ND-EC function, but TNF-α and palmitate significantly reduced angiogenic capacity (by 27% and 43%, resp.), effects mimicked by Akt inhibition. Aberrancies of EC function may help to explain the increased risk of SV graft failure in T2DM patients. This study highlights the importance of other potentially contributing factors in addition to hyperglycaemia that may inflict injury and long-term dysfunction to the homeostatic capacity of the endothelium.

Arecoline is cytotoxic for human endothelial cells

BACKGROUND

Oral submucous fibrosis is a pre-malignant fibrotic condition caused by areca nut use and involves reduced mucosal vascularity. Arecoline is the principal areca nut alkaloid and is cytotoxic for epithelium and fibroblasts. Endothelial cell cycle arrest is reported on exposure to arecoline, as is cytotoxicity for endothelial-lung carcinoma hybrid cells. We here describe cytotoxicity for primary human endothelial cultures from seven separate donors.

MATERIALS AND METHODS

Human umbilical vein endothelial cells were exposed to increasing concentrations of arecoline and examined by: phase-contrast microscopy, haemocytometer counts, transmission electron microscopy, lactate dehydrogenase release and the methyl-thiazol-tetrazolium assay.

RESULTS

Vacuolation and detachment of endothelium were observed at and above arecoline concentrations of 333 μg/ml or more. Ultrastructural features of cellular stress were seen after 24-h treatment with 111 μg/ml arecoline and included reduced ribosomal studding of endoplasmic reticulum, increased autophagolysosomal structures, increased vacuolation and reduced mitochondrial cristae with slight swelling. Similar changes were seen at 4 h with arecoline at 333 μg/ml or above, but with more severe mitochondrial changes including increased electron density of mitochondrial matrix and greater cristal swelling, while by 24 h, these cells were frankly necrotic. Haemocytometer counts were paralleled by both lactate dehydrogenase release and the methyl-thiazol-tetrazolium assays.

CONCLUSIONS

Arecoline is cytotoxic via necrosis for endothelium, while biochemical assays indicate no appreciable cellular leakage before death and detachment, as well as no clear effect on mitochondrial function in viable cells. Arecoline toxicity may thus contribute to reduced vascularity in oral submucous fibrosis.

Inhibition of oxidative stress and lipid peroxidation by anthocyanins from defatted Canarium odontophyllum pericarp and peel using in vitro bioassays

Canarium odontophyllum, also known as CO, is a highly nutritious fruit. Defatted parts of CO fruit are potent sources of nutraceutical. This study aimed to determine oxidative stress and lipid peroxidation effects of defatted CO pericarp and peel extracts using in vitro bioassays. Cell cytotoxic effect of the CO pericarp and peel extracts were also evaluated using HUVEC and Chang liver cell lines. The crude extracts of defatted CO peel and pericarp showed cytoprotective effects in t-BHP and 40% methanol-induced cell death. The crude extracts also showed no toxic effect to Chang liver cell line. Using CD36 ELISA, NAD⁺ and LDL inhibition assays, inhibition of oxidative stress were found higher in the crude extract of defatted CO peel compared to the pericarp extract. Hemoglobin and LDL oxidation assays revealed both crude extracts had significantly reduced lipid peroxidation as compared to control. TBARS values among defatted CO pericarp, peel, and cyanidin-3-glucoside showed no significant differences for hemoglobin and LDL oxidation assays. The protective effects of defatted CO parts, especially its peel is related to the presence of high anthocyanin that potentially offers as a pharmaceutical ingredient for cardioprotection.

Rapid activation of nuclear factor κB by 17β-estradiol and selective estrogen receptor modulators: pathways mediating cellular protection

17β-Estradiol (E2) treatment activates a set of protective response that has been found to protect cells from injury and more importantly to significantly abate the injuries associated with trauma-hemorrhage in vivo. Rapid NF-κB activation has been found to be an important signaling step in E2-mediated protection in cell culture, in vivo ischemia, and trauma-hemorrhage. In the current study, we investigated the signaling cascades linking E2 signaling with NF-κB activation and the protective response and compared them with the effects of two selective estrogen receptor modulators (SERMs), raloxifene and tamoxifen. Two candidate pathways, mitogen-activated protein kinases and phosphatidylinositol-3-kinase (PI3K) were studied. Selective inhibitors were used to identify each pathway's contribution to NF-κB activation. Treatment of human coronary artery endothelial cells with E2 activated PI3K/Akt, p38, and JNK, all of which activated ERK1/2 followed by NF-κB activation. The combined activation of Akt, p38, and JNK was essential to activate NF-κB. The two SERMs activated PI3K and p38, which then phosphorylated ERK1/2 and activated NF-κB independent of the JNK pathway. Nuclear factor κB activation by these compounds protected cells from hypoxia/reoxygenation injury. However, E2, unlike either SERM, led to modest increases in apoptosis through the JNK pathway. Selective estrogen receptor modulator treatment led to increased expression of the protective proteins, Mn superoxide dismutase, and endothelial nitric oxide synthase, which was not seen with E2. These results provide new insight into the pathways activating NF-κB by E2 and SERMs and demonstrate that SERMs may have greater protective benefits than E2 in adult endothelial cells and potentially in vivo, as well.

Estrogen and the cardiovascular system

Estrogen is a potent steroid with pleiotropic effects, which have yet to be fully elucidated. Estrogen has both nuclear and non-nuclear effects. The rapid response to estrogen, which involves a membrane associated estrogen receptor(ER) and is protective, involves signaling through PI3K, Akt, and ERK 1/2. The nuclear response is much slower, as the ER-estrogen complex moves to the nucleus, where it functions as a transcription factor, both activating and repressing gene expression. Several different ERs regulate the specificity of response to estrogen, and appear to have specific effects in cardiac remodeling and the response to injury. However, much remains to be understood about the selectivity of these receptors and their specific effects on gene expression. Basic studies have demonstrated that estrogen treatment prevents apoptosis and necrosis of cardiac and endothelial cells. Estrogen also attenuates pathologic cardiac hypertrophy. Estrogen may have great benefit in aging as an anti-inflammatory agent. However, clinical investigations of estrogen have had mixed results, and not shown the clear-cut benefit of more basic investigations. This can be explained in part by differences in study design: in basic studies estrogen treatment was used immediately or shortly after ovariectomy, while in some key clinical trials, estrogen was given years after menopause. Further basic research into the underlying molecular mechanisms of estrogen's actions is essential to provide a better comprehension of the many properties of this powerful hormone.

Lymph node-derived lymphatic endothelial cells express functional costimulatory molecules and impair dendritic cell-induced allogenic T-cell proliferation

Lymphatic endothelial cells (LECs) interact with different immune cells, including T cells within lymph nodes (LNs). However, direct interactions of LECs with immune cells have yet to be investigated. In vitro studies were performed to characterize primary cultures of human LECs derived from LNs in their capacity of interacting with T cells. The results show that LECs express HLA molecules and functional costimulatory molecules needed for T-cell activation. A direct binding of LECs and T cells was detected in cell cultures connected with a clustering of costimulatory molecules on the contact phase. LECs were also able to take up and process antigens. However, major histocompatibility complex class II(+) LECs fail to induce allogeneic T-cell proliferation. Interestingly, supernatants of IFN-γ activated LECs impair proliferation of T cells cocultured with allogeneic dendritic cells, suggesting an inhibitory role of LECs. Indoleamine 2,3 dioxygenase was identified as one inhibitory molecule, which may be responsible for the impaired CD4(+) T-cell proliferation. Our observations suggest a regulatory function for activated LECs on CD4(+) T cells, which may play a role in vivo in the maintenance of the critical balance between tolerance and recall responses.

Participation of blood vessel cells in human adaptive immune responses

Circulating T cells contact blood vessels either when they extravasate across the walls of microvessels into inflamed tissues or when they enter into the walls of larger vessels in inflammatory diseases such as atherosclerosis. The blood vessel wall is largely composed of three cell types: endothelial cells lining the entire vascular tree; pericytes supporting the endothelium of microvessels; and smooth muscle cells forming the bulk of large vessel walls. Each of these cell types interacts with and alters the behavior of infiltrating T cells in different ways, making these cells active participants in the processes of immune-mediated inflammation. In this review, we compare and contrast what is known about the nature of these interactions in humans.

Racial differences in tumor necrosis factor-α-induced endothelial microparticles and interleukin-6 production

African Americans (AA) tend to have heightened systemic inflammation and endothelial dysfunction. Endothelial microparticles (EMP) are released from activated/apoptotic endothelial cells (EC) when stimulated by inflammation. The purpose of our study was to assess EMP responses to inflammatory cytokine (TNF-α) and antioxidant (superoxide dismutase, SOD) conditions in human umbilical vein ECs (HUVECs) obtained from AA and Caucasians. EMPs were measured under four conditions: control (basal), TNF-α, SOD, and TNF-α + SOD. Culture supernatant was collected for EMP analysis by flow cytometry and IL-6 assay by ELISA. IL-6 protein expression was assessed by Western blot. AA HUVECs had greater EMP levels under the TNF-α condition compared to the Caucasian HUVECs (6.8 ± 1.1 vs 4.7% ± 0.4%, P = 0.04). The EMP level increased by 89% from basal levels in the AA HUVECs under the TNF-α condition (P = 0.01) compared to an 8% increase in the Caucasian HUVECs (P = 0.70). Compared to the EMP level under the TNF-α condition, the EMP level in the AA HUVECs was lower under the SOD only condition (2.9% ± 0.3%, P = 0.005) and under the TNF-α + SOD condition (2.1% ± 0.4%, P = 0.001). Basal IL-6 concentrations were 56.1 ± 8.8 pg/mL/μg in the AA and 30.9 ± 14.9 pg/mL/μg in the Caucasian HUVECs (P = 0.17), while basal IL-6 protein expression was significantly greater (P < 0.05) in the AA HUVECs. These preliminary observational results suggest that AA HUVECs may be more susceptible to the injurious effects of the proinflammatory cytokine, TNF-α.

Impact of normothermic perfusion and protein supplementation on human endothelial cell function during organ preservation

BACKGROUND

Hypothermia-induced changes in endothelial cell (EC) morphology and function after organ storage may influence the initial outcome and development of transplant-associated coronary artery disease.

METHODS

Human saphenous vein ECs were incubated with saline (NaCl), University of Wisconsin (UW), and histidine-tryptophan-ketoglutarate (HTK) solution, with and without protein additives, at 4 degrees C and 37 degrees C. After 6 hours, ECs were recultivated for 24 and 48 hours with culture medium (reperfusion). Mitochondrial activity, adenosine triphosphate concentration, cell count, and inflammatory responses were analyzed.

RESULTS

Cold preservation did not affect the mitochondrial activity of ECs and allowed a complete regeneration of the metabolic turnover after reperfusion. However, under normothermic conditions the metabolism of the cells was influenced by time and type of preservation solution. While both the mitochondrial activity and cell count did not change after treatment with NaCl and culture medium, the metabolic turnover of cells treated with HTK and UW solution significantly increased (twofold) and decreased (twofold, p < 0.05), respectively, after reperfusion. The endothelial reactivity remained unchanged after treatment with NaCl and HTK. The addition of serum proteins significantly improved mitochondrial activity of cells treated with warm NaCl and HTK (p < 0.05). The UW-treated cells burned out through a significant up-regulation of the ATP concentration resulting in a complete metabolic regression after reperfusion and induction of apoptosis.

CONCLUSIONS

Normothermic preservation in UW prevented regeneration of ECs, while treatment with HKT solution did not irreversibly affect mitochondrial activity of ECs and allowed complete regeneration of metabolism and function. Serum proteins improved the preservation effect of HTK and NaCl.