Differential mitogenic responses of human macrovascular and microvascular endothelial cells to cytokines underline their phenotypic heterogeneity

Piezo1 channels are mechanosensors in human fetoplacental endothelial cells

STUDY QUESTION

Does the shear stress sensing ion channel subunit Piezo1 have an important mechanotransduction role in human fetoplacental endothelium?

SUMMARY ANSWER

Piezo1 is present and functionally active in human fetoplacental endothelial cells, and disruption of Piezo1 prevents the normal response to shear stress.

WHAT IS KNOWN ALREADY

Shear stress is an important stimulus for maturation and function of placental vasculature but the molecular mechanisms by which the force is detected and transduced are unclear. Piezo1 channels are Ca²⁺-permeable non-selective cationic channels which are critical for shear stress sensing and maturation of murine embryonic vasculature.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

We investigated the relevance of Piezo1 to placental vasculature by studying human fetoplacental endothelial cells (FpECs) from healthy pregnancies. Endothelial cells were isolated from placental cotyledons and cultured, for the study of tube formation and cell alignment to shear stress. In addition, human placental arterial endothelial cells were isolated and studied immediately by patch-clamp electrophysiology.

MAIN RESULTS AND THE ROLE OF CHANCE

The synthetic Piezo1 channel agonist Yoda1 caused strong elevation of the intracellular Ca²⁺ concentration with a 50% effect occurring at about 5.4 μM. Knockdown of Piezo1 by RNA interference suppressed the Yoda1 response, consistent with it being mediated by Piezo1 channels. Alignment of cells to the direction of shear stress was also suppressed by Piezo1 knockdown without loss of cell viability. Patch-clamp recordings from freshly isolated endothelium showed shear stress-activated single channels which were characteristic of Piezo1.

LIMITATIONS, REASONS FOR CAUTION

The in vitro nature of fetoplacental endothelial cell isolation and subsequent culture may affect FpEC characteristics and PIEZO1 expression. In addition to Piezo1, alternative shear stress sensing mechanisms have been suggested in other systems and might also contribute in the placenta.

WIDER IMPLICATIONS OF THE FINDINGS

These data suggest that Piezo1 is an important molecular determinant of blood flow sensitivity in the placenta. Establishing and manipulating the molecular mechanisms regulating shear stress sensing could lead to novel therapeutic strategies to improve blood flow in the placenta.

LARGE-SCALE DATA

Not applicable.

STUDY FUNDING/COMPETING INTEREST(S)

LCM was funded by a Clinical Research Training Fellowship from the Medical Research Council and by the Royal College of Obstetricians and Gynaecologists, and has received support from a Wellcome Trust Institutional Strategic Support Fund. JS was supported by the Wellcome Trust and a BHF Intermediate Research Fellowship. HJG, CW, AJH and PJW were supported by PhD Studentships from BHF, BBSRC and the Leeds Teaching Hospitals Charitable Foundation respectively. All authors declare no conflict of interest.

Lymphatic endothelial cells promote productive and latent HIV infection in resting CD4+ T cells

Background

An HIV cure has not yet been achieved because latent viral reservoirs persist, particularly in resting CD4+ T lymphocytes. In vitro, it is difficult to infect resting CD4+ T cells with HIV-1, but infections readily occur in vivo. Endothelial cells (EC) line the lymphatic vessels in the lymphoid tissues and regularly interact with resting CD4+ T cells in vivo. Others and we have shown that EC promoted productive and latent HIV infection of resting CD4+ T cells. However, the EC used in previous studies were from human umbilical cords (HUVEC), which are macrovascular; whereas EC residing in the lymphoid tissues are microvascular.

Methods

In this study, we investigated the effects of microvascular EC stimulation of resting CD4+ T cells in establishing viral infection and latency. Human resting and activated CD4+ T cells were cultured alone or with endothelial cells and infected with a pseudotyped virus. Infection levels, indicated by green fluorescent protein expression, were measured with flow cytometry and data was analyzed using Flowing Software and Excel.

Results

We confirmed that EC from lymphatic tissue (LEC) were able to promote HIV infection and latency formation in resting CD4+ T cells while keeping them in resting phenotype, and that IL-6 was involved in LEC stimulation of CD4+ T cells. However, there are some differences between stimulation by LEC and HUVEC. Unlike HUVEC stimulation, we demonstrated that LEC stimulation of resting memory T cells does not depend on major histocompatibility complex class II (MHC II) interactions with T cell receptors (TCR) and that CD2-CD58 interactions were not involved in LEC stimulation of resting T cells. LEC also secreted lower levels of IL-6 than HUVEC. We also found that LEC stimulation increases HIV infection rates in activated CD4+ T cells.

Conclusions

While differences in T cell stimulation between lymphatic EC and HUVEC were observed, we confirmed that similar to macrovascular EC stimulation, microvascular EC stimulation promotes direct HIV infection and latency formation in resting CD4+ T cells without T cell activation. LEC stimulation also increased infection rates in activated CD4+ T cells. Additionally, the present study established a physiologically more relevant model of EC interactions with resting CD4+ T cells and further highlighted the importance of investigating the roles of EC in HIV infection and latency in both resting and activated CD4+ T cells.

Diversity in human placental microvascular endothelial cells and macrovascular endothelial cells

Angiogenesis is fundamental to normal placental development, and aberrant angiogenesis contributes substantially to placental pathologies. Placental angiogenesis is a pivotal process that plays a key mechanistic role in the elaboration of the placental villous tree, which is mainly taken by human placental microvascular endothelial cells (HPMECs), present in the fetal capillaries of chorionic villi, and macrovascular human umbilical vein endothelial cells (HUVECs) also play a role in this process. These are the two types of endothelial cells that form the placenta and differ in morphology and function. The placental vasculature represents a distinct territory that is highly specialized in structure and function. To distinguish the differences between HPMECs and HUVECs, we isolated HPMECs by paramagnetic particle separation and HUVECs through trypsinization and validated their characteristics. Then, we examined their response to fibroblast growth factor 2 (FGF2), vascular endothelial growth factor (VEGF) and endocrine-gland-derived vascular endothelial growth factor (EG-VEGF), as well as the underlying signaling mechanisms and their transcriptomes. We found that cultured HPMECs and HUVECs took up DiI-Ac-LDL and formed capillary-like tube structures on Matrigel. HPMECs and HUVECs had different expressions of eNOS, PROKR1 and PROKR2, and these characteristics substantiate the endothelial nature of cultured cells. FGF2 and VEGF stimulated the proliferation and migration of HPMECs and HUVECs via activation of PI3K/AKT1 and MEK1/MEK2/ERK1/ERK2. Interestingly, EG-VEGF increased the proliferation and migration of HPMECs via only MEK1/MEK2/ERK1/ERK2 and not PI3K/AKT1. Microarray analysis showed that there were some differentially expressed genes between HPMECs and HUVECs. Gene ontology analysis indicated that the differentially expressed genes were highly related to G-protein coupled receptor signaling pathway, angiogenesis, L-lysine transmembrane transport and blood vessel remodeling. These data provided evidence of heterogeneity between microvascular HPMECs and macrovascular HUVECs that most likely reflected significant differences in endothelial cell function in the two different cellular environments.

Asymmetric dimethylarginine contributes to retinal neovascularization of diabetic retinopathy through EphrinB2 pathway

Diabetic retinopathy (DR) is a leading cause of vision loss with retinal neovascularization. This study aims to investigate whether Asymmetric dimethylarginine (ADMA) impacts the pathogenesis of DR via focusing on promoting retinal neovascularization and its underlying molecular mechanisms. Diabetic rats were induced by a single intraperitoneal injection of streptozotocin (STZ) for 20 weeks. ADMA levels in aqueous and the influence of hypoxia on ADMA and angiogenesis in RF/6A cells were examined. The effects and underlying molecular mechanisms of ADMA on neovascularization of RF/6A cells were further evaluated by administration of ADMA, DDAH siRNA or ephrinB2 siRNA. Results showed that ADMA levels were elevated in both aqueous from diabetic rats and culture medium in RF/6A cells pretreated with hypoxia. Administration of ADMA directly promoted proliferation, migration, adhesion and tube formation of RF/6A cells, which was further confirmed by DDAH1 siRNA or DDAH2 siRNA. In addition, ephrinB2 expression was increased under diabetic conditions, and the angiogenic effects of ADMA were blocked by ephrinB2 siRNA. In conclusion, ADMA contributes to the neovascularization of retina in diabetic mellitus, which is regulated by ephrinB2.

Co-Emergence of Specialized Endothelial Cells from Embryonic Stem Cells

A well-formed and robust vasculature is critical to the health of most organ systems in the body. However, the endothelial cells (ECs) forming the vasculature can exhibit a number of distinct functional subphenotypes like arterial or venous ECs, as well as angiogenic tip and stalk ECs. In this study, we investigate the in vitro differentiation of EC subphenotypes from embryonic stem cells (ESCs). Using our staged induction methods and chemically defined mediums, highly angiogenic EC subpopulations, as well as less proliferative and less migratory EC subpopulations, are derived. Furthermore, the EC subphenotypes exhibit distinct surface markers, gene expression profiles, and positional affinities during sprouting. While both subpopulations contained greater than 80% VE-cad⁺/CD31⁺ cells, the tip/stalk-like EC contained predominantly Flt4⁺/Dll4⁺/CXCR4⁺/Flt-1^- cells, while the phalanx-like EC was composed of higher numbers of Flt-1⁺ cells. These studies suggest that the tip-specific EC can be derived in vitro from stem cells as a distinct and relatively stable EC subphenotype without the benefit of its morphological positioning in the sprouting vessel.

Endothelial Alterations in Systemic Lupus Erythematosus and Rheumatoid Arthritis: Potential Effect of Monocyte Interaction

Patients with systemic autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are prone to develop atherosclerosis and cardiovascular diseases five times more often than the general population; this increase in frequency could be partially explained by an increase in the macrovasculature endothelial damage. In these autoimmune diseases, a microvascular endothelial injury has also been reported in different organs and tissues, especially in sites where ultrafiltration processes occur. Different components that are characteristic to the immunopathology of RA and SLE could be involved in the endothelial cell activation, permeability increase, functional alteration, and vascular injury. Circulating immune complexes (IC) detected in SLE and RA have been proposed to participate in the endothelial injury. In the vascular environment, IC can generate different responses that could be mediated by monocytes, because these cells have patrolling and monitoring functions on the endothelium. However, with certain stimuli such as TLR ligands, the monocytes are retained in the lumen, releasing proinflammatory mediators that participate in the endothelial damage. This paper aims to review some aspects about the endothelial activation and dysfunction in the context of SLE and RA, as well as the potential role that monocytes apparently play in this process.

Endothelial cell-derived endothelin-1 is involved in abnormal scar formation by dermal fibroblasts through RhoA/Rho-kinase pathway

Hypertrophic scars and keloids are characterized by excessive dermal deposition of extracellular matrix due to fibroblast-to-myofibroblast differentiation. Endothelin-1 (ET-1) is primarily produced by vascular endothelial cells and plays multiple roles in the wound-healing response and organ fibrogenesis. In this study, we investigated the pathophysiological significance of ET-1 and involvement of RhoA, a member of the Rho GTPases, in hypertrophic scar/keloid formation. We found that ET-1 expression on dermal microvascular endothelial cells (ECs) in hypertrophic scars and keloids was higher than that in normal skin and mature scars. We also confirmed that ET-1 induced myofibroblast differentiation and collagen synthesis in cultured human dermal fibroblasts through the RhoA/Rho-kinase pathway. Finally, since hypertrophic scar/keloid formation was most prominent in areas exposed to mechanical stretch, we examined how mechanical stretch affected ET-1 secretion in human dermal microvascular ECs, and found that mechanical stretch increased ET-1 gene expression and secretion from ECs. Taken together, these results suggest that dermal microvascular ECs release ET-1 in response to mechanical stretch, and thereby contribute to the formation of hypertrophic scars and keloids through the RhoA/Rho-kinase pathway.

Endocrine Gland-Derived Vascular Endothelial Growth Factor/Prokineticin-1 in Cancer Development and Tumor Angiogenesis

A lot of data suggests endocrine gland-derived vascular endothelial growth factor (EG-VEGF) to be restricted to endocrine glands and to some endocrine-dependent organs. Many evidences show that EG-VEGF stimulates angiogenesis and cell proliferation, although it is not a member of the VEGF family. At the time, a lot of data regarding the role of this growth factor in normal development are available. However, controversial results have been published in the case of pathological conditions and particularly in malignant tumors. Thus, our present paper has been focused on the role of EG-VEGF in normal tissues and various malignant tumors and their angiogenic processes.

4-Hydroxy-7-oxo-5-heptenoic Acid Lactone Induces Angiogenesis through Several Different Molecular Pathways

Oxidative stress and angiogenesis have been implicated not only in normal phenomena such as tissue healing and remodeling but also in many pathological processes. However, the relationships between oxidative stress and angiogenesis still remain unclear, although oxidative stress has been convincingly demonstrated to influence the progression of angiogenesis under physiological and pathological conditions. The retina is particularly susceptible to oxidative stress because of its intensive oxygenation and high abundance of polyunsaturated fatty acyls. In particular, it has high levels of docosahexanoates, whose oxidative fragmentation produces 4-hydroxy-7-oxo-5-heptenoic acid lactone (HOHA-lactone). Previously, we found that HOHA-lactone is a major precursor of 2-(ω-carboxyethyl)pyrrole (CEP) derivatives, which are tightly linked to age-related macular degeneration (AMD). CEPs promote the pathological angiogenesis of late-stage AMD. We now report additional mechanisms by which HOHA-lactone promotes angiogenesis. Using cultured ARPE-19 cells, we observed that HOHA-lactone induces secretion of vascular endothelial growth factor (VEGF), which is correlated to increases in reactive oxygen species and decreases in intracellular glutathione (GSH). Wound healing and tube formation assays provided, for the first time, in vitro evidence that HOHA-lactone induces the release of VEGF from ARPE-19 cells, which promotes angiogenesis by human umbilical vein endothelial cells (HUVEC) in culture. Thus, HOHA-lactone can stimulate vascular growth through a VEGF-dependent pathway. In addition, results from MTT and wound healing assays as well as tube formation experiments showed that GSH-conjugated metabolites of HOHA-lactone stimulate HUVEC proliferation and promote angiogenesis in vitro. Previous studies demonstrated that HOHA-lactone, through its CEP derivatives, promotes angiogenesis in a novel Toll-like receptor 2-dependent manner that is independent of the VEGF receptor or VEGF expression. The new studies show that HOHA-lactone also participates in other angiogenic signaling pathways that include promoting the secretion of VEGF from retinal pigmented epithelial cells.

The JAK/STAT3 signalling pathway regulated angiogenesis in an endothelial cell/adipose-derived stromal cell co-culture, 3D gel model

OBJECTIVES

The aim of the study was to investigate the role of the JAK/STAT3 signalling pathway in angiogenesis.

MATERIALS AND METHODS

The model established in vitro, involved a 3D collagen gel being implanted with endothelial cells (ECs) from red fluorescent protein-labelled mice, and adipose-derived stromal cells (ASCs) from green fluorescent protein-labelled mice. Phenomena of angiogenesis, after treatment by the inhibitor and the activator of JAK/STAT3 pathway respectively, were observed using confocal laser scanning microscopy. Transwell co-culture of ECs and ASCs was used to elucidate mechanisms.

RESULTS

Stattic, inhibitor of JAK/STAT3 pathway, attenuated angiogenesis in the model. In contrast, angiogenesis was promoted after treatment of Olanzapine, an activator. We found that protein levels of VEGFA and cyclin D1 were regulated by the JAK/STAT3 pathway, and flow cytometry further confirmed variations in cell cycle parameters of ECs and ASCs. Genes VEGFA/B, VEGFR2, MMP-2, MMP-9, IGF-1 and b-FGF were down-regulated by Stattic in ECs, while Olanzapine significantly up-regulated mRNA levels of these genes. As for ASCs, genes VEGFA, MMP-2, MMP-9, IGF-1 and b-FGF were modulated by the JAK/STAT3 pathway.

CONCLUSIONS

Angiogenesis in the 3D collagen gel was regulated by the JAK/STAT3 pathway which involved changes in vessel length, vessel diameter and sprout number. The underlying mechanism was that the JAK/STAT3 signalling pathway regulated angiogenesis by modulation of numbers of angiogenesis-related growth factors and by direct regulation of cell cycle.

TGFβ signalling pathway regulates angiogenesis by endothelial cells, in an adipose-derived stromal cell/endothelial cell co-culture 3D gel model

OBJECTIVE

This study aimed to investigate the role of the TGFβ signalling pathway in angiogenesis in a three-dimensional (3D) collagen gel model, with co-culture between adipose-derived stromal cells (ASCs) and endothelial cells (ECs).

MATERIALS AND METHODS

A 3D collagen gel, implanted with green fluorescent protein-labelled mouse ASCs and red fluorescent protein-labelled mouse ECs, was established in vitro. Phenomena of angiogenesis with or without type I TGFβ receptor inhibitor (LY2157299) treatment, were observed 7 days post-implantation, using confocal laser scanning microscopy. To detect expression of angiogenesis-related genes, semi-quantitative PCR and quantitative real-time PCR were conducted. Zymography was performed to explore secretion of matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) after treatment with LY2157299 of 5, 10, 20 to 50 μm concentrations, for 24 h.

RESULTS

Angiogenesis was found to be attenuated in co-culture gels after ASC and EC treatment with LY2157299. Genes VEGF-A, VEGF-B, VE-ca, FGF-1, FGF-2, PDGF, HGF, BMP-4 were significantly reduced in the presence of LY2157299 in both mono-cultured and co-cultured ECs. Furthermore, reduction in co-cultured ECs was prominent relative to mono-cultured ECs, while the same results did not occur to ASCs. We further confirmed that gelatinases secreted by ECs were reduced in a dose-dependent manner, after treatment with LY2157299.

CONCLUSIONS

These results indicate that in ASC/EC co-culture, the TGFβ signalling pathway regulated angiogenesis via EC activity. Co-cultured ECs were regulated more significantly than mono-cultured ECs suggesting that inhibition of TGFβRI may regulate paracrine secretion of ASCs to further modulate EC angiogenesis.

Role of the fetoplacental endothelium in fetal growth restriction with abnormal umbilical artery Doppler velocimetry

Growth-restricted fetuses with absent or reversed end-diastolic velocities in the umbilical artery are at substantially increased risk for adverse perinatal and long-term outcome, even in comparison to growth-restricted fetuses with preserved end-diastolic velocities. Translational studies show that this Doppler velocimetry correlates with fetoplacental blood flow, with absent or reversed end-diastolic velocities signifying abnormally elevated resistance within the placental vasculature. The fetoplacental vasculature is unique in that it is not subject to autonomic regulation, unlike other vascular beds. Instead, humoral mediators, many of which are synthesized by local endothelial cells, regulate placental vascular resistance. Existing data demonstrate that in growth-restricted pregnancies complicated by absent or reversed umbilical artery end-diastolic velocities, an imbalance in production of these vasoactive substances occurs, favoring vasoconstriction. Morphologically, placentas from these pregnancies also demonstrate impaired angiogenesis, whereby vessels within the terminal villi are sparsely branched, abnormally thin, and elongated. This structural deviation from normal placental angiogenesis restricts blood flow and further contributes to elevated fetoplacental vascular resistance. Although considerable work has been done in the field of fetoplacental vascular development and function, much remains unknown about the mechanisms underlying impaired development and function of the human fetoplacental vasculature, especially in the context of severe fetal growth restriction with absent or reversed umbilical artery end-diastolic velocities. Fetoplacental endothelial cells are key regulators of angiogenesis and vasomotor tone. A thorough understanding of their role in placental vascular biology carries the significant potential of discovering clinically relevant and innovative approaches to prevention and treatment of fetal growth restriction with compromised umbilical artery end-diastolic velocities.

The multiple roles of EG-VEGF/PROK1 in normal and pathological placental angiogenesis

Placentation is associated with several steps of vascular adaptations throughout pregnancy. These vascular changes occur both on the maternal and fetal sides, consisting of maternal uterine spiral arteries remodeling and placental vasculogenesis and angiogenesis, respectively. Placental angiogenesis is a pivotal process for efficient fetomaternal exchanges and placental development. This process is finely controlled throughout pregnancy, and it involves ubiquitous and pregnancy-specific angiogenic factors. In the last decade, endocrine gland derived vascular endothelial growth factor (EG-VEGF), also called prokineticin 1 (PROK1), has emerged as specific placental angiogenic factor that controls many aspects of normal and pathological placental angiogenesis such as recurrent pregnancy loss (RPL), gestational trophoblastic diseases (GTD), fetal growth restriction (FGR), and preeclampsia (PE). This review recapitulates EG-VEGF mediated-angiogenesis within the placenta and at the fetomaternal interface and proposes that its deregulation might contribute to the pathogenesis of several placental diseases including FGR and PE. More importantly this paper argues for EG-VEGF clinical relevance as a potential biomarker of the onset of pregnancy pathologies and discusses its potential usefulness for future therapeutic directions.

Selective Activation of Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 Mediates C-Reactive Protein–Evoked Endothelial Vasodilator Dysfunction in Coronary Arterioles

Rationale :

Studies in cultured endothelium implicate that lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) or Fcγ receptor II (CD32) contributes to the proatherogenic effects of C-reactive protein (CRP). However, the identity of the receptors linking to deleterious actions of CRP in vasomotor regulation remains unknown.

Objective :

We tested the hypothesis that LOX-1 contributes to adverse effects of CRP on endothelium-dependent vasomotor function in resistance arterioles.

Methods and Results :

Porcine coronary arterioles were isolated for vasoreactivity study, dihydroethidium fluorescence staining of superoxide, immunohistochemical localization of receptors, immunoprecipitation of receptor/CRP interaction, and protein blot. Intraluminal treatment of pressurized arterioles with a pathophysiological level of CRP (7 µg/mL; 60 minutes) attenuated endothelium-dependent nitric oxide–mediated and prostacyclin-mediated dilations to serotonin and arachidonic acid, respectively. LOX-1 and CD32 were detected in the endothelium of arterioles. Blockade of LOX-1 with either pharmacological antagonist κ-carrageenan or anti–LOX-1 antibody prevented the detrimental effect of CRP on vasodilator function, whereas anti-CD32 antibody treatment was ineffective. Denudation of endothelium and blockade of LOX-1 but not CD32 prevented CRP-induced elevation of superoxide in the vessel wall. CRP was coimmunoprecipitated with LOX-1 and CD32 from CRP-treated arterioles. Similarly, LOX-1 and CD32 blockade prevented CRP-induced arteriolar expression of plasminogen activator inhibitor-1, a thrombogenic protein.

Conclusions :

CRP elicits endothelium-dependent oxidative stress and compromises nitric oxide–mediated and prostacyclin-mediated vasomotor function via LOX-1 activation. In contrast, both LOX-1 and CD32 mediate plasminogen activator inhibitor-1 upregulation in arterioles by CRP. Thus, activation of LOX-1 and CD32 may contribute to vasomotor dysfunction and proatherogenic actions of CRP, respectively.

GM-CSF exhibits anti-inflammatory activity on endothelial cells derived from chronic venous disease patients

Twenty patients affected by chronic venous disease (CVD) in tertiary venous network and/or saphenous vein were analyzed before surgical ablation by echo-color-doppler for the hemodynamic parameters reflux time (RT) and resistance index (RI), a negative and a positive prognostic factor, respectively. RT and RI were next correlated with relevant in vitro parameters of venous endothelial cells (VEC) obtained from surgical specimens, such as cell migration in response to serum gradient, proliferation index, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 expression, as well as cytokines release. Of interest, ICAM-1 expression in patient-derived VEC cultures correlated positively with RT and negatively with RI. Moreover, RT showed a positive correlation with the baseline osteoprotegerin (OPG) expression by VEC and an inverse correlation with VEC proliferation index. On the other hand, RI correlated positively with TNF-related apoptosis inducing ligand (TRAIL) expression. Among the cytokines released by VEC, GM-CSF showed a positive correlation with VEC proliferation and TRAIL expression and a negative correlation with OPG, ICAM-1 and VCAM-1 expression. Since in vitro recombinant GM-CSF induced VEC proliferation and counteracted the induction of ICAM-1, VCAM-1 and OPG upon exposure to TNF-α, our data suggest an anti-inflammatory activity of GM-CSF on venous endothelial cells.

Astragalus Polysaccharide Suppresses the Expression of Adhesion Molecules through the Regulation of the p38 MAPK Signaling Pathway in Human Cardiac Microvascular Endothelial Cells after Ischemia-Reperfusion Injury

Astragalus polysaccharide is a major component of radix astragali, a vital qi-reinforcing herb medicine with favorable immune-regulating effects. In a previous animal experiment, we demonstrated that astragalus polysaccharide effectively alleviates ischemia-reperfusion injury (IRI) of cardiac muscle through the regulation of the inflammatory reactions. However, the relationship between this herb and the cohesion molecules on the cell surface remains controversial. In this study, human cardiac microvascular endothelial cells (HCMECs) were used to validate the protective effects of astragalus under an IRI scheme simulated through hypoxia/reoxygenation in vitro. The results indicated that astragalus polysaccharide inhibited the cohesion between HCMECs and polymorphonuclear leukocyte (PMN) during IRI through the downregulation of p38 MAPK signaling and the reduction of cohesive molecule expression in HCMECs.

Genetic variation in a miR-335 binding site in BIRC5 alters susceptibility to lung cancer in Chinese Han populations

Polymorphisms in 3' untranslated region (UTR) of cancer-related genes might affect their regulation by microRNAs (miRNAs) and thereby contribute to carcinogenesis. In this study, we screened single nucleotide polymorphisms (SNPs) in 3' UTR of cancer-related genes and investigated their effects on risk of lung cancer. First, we genotyped seven SNPs in a Chinese Han population with 600 lung cancer patients and 600 matched healthy controls and found that compared with the TT genotype of rs2239680 in 3' UTR of baculoviral IAP repeat containing 5 (BIRC5), C allele was associated with a significantly increased risk of lung cancer and advanced pathologic stage, with the odds ratio for participants carrying the CT or CC genotype being 1.50 [95% confidence interval (CI) 1.20-1.89, P<0.01] and 2.29 (95% CI 1.64-3.18, P<0.01), respectively. These results were further replicated and confirmed in another independent population with 1000 lung cancer cases and 1000 matched healthy controls. In support of the postulation that the 3' UTR SNP may directly affect miRNA-binding site, reporter gene assays indicated BIRC5 was a direct target of miR-335, and the rs2239680 T>C change resulted in altered regulation of BIRC5 expression. Moreover, BIRC5 was over expressed in lung cancer tissues compared with the normal lung tissues, and the protein levels of BIRC5 correlated with SNP genotypes in normal lung tissues. Our findings defined a 3' UTR SNP in human BIRC5 oncogene that may increase individual susceptibility to lung cancer probably by attenuating the interaction between miR-335 and BIRC5.

Rotational co-culture of clonal β-cells with endothelial cells: effect of PPAR-γ agonism in vitro on insulin and VEGF secretion

AIM

Delayed graft revascularization impedes the success of human islet transplantation. This study utilized rotational co-culture of insulin secreting β-cells with human umbilical vein endothelial cells (HUVECs) and a peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist to promote insulin and vascular endothelial growth factor (VEGF) secretory function.

METHODS

Clonal BRIN-BD11 (D11) cells were maintained in static culture (SC) and rotational culture (RC) ± HUVEC and ± the TZD (thiazolidinedione) rosiglitazone (10 mmol/l) as a specific PPAR-γ agonist. HUVECs were cultured in SC and RC ± D11 and ± TZD. D11 insulin secretion was induced by static incubation with low glucose (1.67 mmol/l), high glucose (16.7 mmol/l) and high glucose with 10 mmol/l theophylline (G+T) and assessed by enzyme-linked immunosorbent assay (ELISA). HUVEC proliferation was determined by ATP luminescence, whereas VEGF secretion was quantified by ELISA. Co-cultured cells were characterized by immunostaining for insulin and CD31.

RESULTS

D11 SC and RC showed enhanced insulin secretion in response to 16.7 mmol/l and G+T (p < 0.01); without significant alteration by the TZD. Co-culture with HUVEC in SC and RC also increased D11 insulin secretion when challenged with 16.7 mmol/l and G+T (p < 0.01), and this was slightly enhanced by the TZD. The presence of HUVEC increased D11 SC and RC insulin secretion in response to high glucose and G+T, respectively (p < 0.01). Addition of the TZD increased SC and RC HUVEC ATP content (p < 0.01) and VEGF production (p < 0.01) in the presence and absence of D11 cells.

CONCLUSIONS

Rotational co-culture of insulin secreting cells with endothelial cells, and exposure to a PPAR-γ agonist may improve the prospects for graft revascularization and function after implantation.

Molecular characterization of EG-VEGF-mediated angiogenesis: differential effects on microvascular and macrovascular endothelial cells

Endocrine gland derived vascular endothelial growth factor (EG-VEGF) also called prokineticin (PK1), has been identified and linked to several biological processes including angiogenesis. EG-VEGF is abundantly expressed in the highest vascularized organ, the human placenta. Here we characterized its angiogenic effect using different experimental procedures. Immunohistochemistry was used to localize EG-VEGF receptors (PROKR1 and PROKR2) in placental and umbilical cord tissue. Primary microvascular placental endothelial cell (HPEC) and umbilical vein-derived macrovascular EC (HUVEC) were used to assess its effects on proliferation, migration, cell survival, pseudovascular organization, spheroid sprouting, permeability and paracellular transport. siRNA and neutralizing antibody strategies were used to differentiate PROKR1- from PROKR2-mediated effects. Our results show that 1) HPEC and HUVEC express both types of receptors 2) EG-VEGF stimulates HPEC's proliferation, migration and survival, but increases only survival in HUVECs. and 3) EG-VEGF was more potent than VEGF in stimulating HPEC sprout formation, pseudovascular organization, and it significantly increases HPEC permeability and paracellular transport. More importantly, we demonstrated that PROKR1 mediates EG-VEGF angiogenic effects, whereas PROKR2 mediates cellular permeability. Altogether, these data characterized angiogenic processes mediated by EG-VEGF, depicted a new angiogenic factor in the placenta, and suggest a novel view of the regulation of angiogenesis in placental pathologies.

Angiogenesis, adipokines and breast cancer

The prevalence of overweight and obesity is rapidly increasing world wide. Numerous epidemiological studies have shown that obesity is a risk factor for postmenopausal breast cancer and relapse. However, the biological factors that drive the growth and progression of these tumors and how obesity contributes to the tumor microenvironment are poorly understood. Tumor development and metastasis are dependent on the process of angiogenesis or the formation of new blood vessels. More importantly, a ready supply of adipose tissue-derived angiogenic adipokines, notably VEGF and leptin, and the production of inflammatory cytokines by infiltrating macrophages that occurs in adipose tissues with obesity, promotes the paracrine stimulation of vascular endothelial cell growth needed for adipogenesis, while maintaining a microenvironment that is favorable for breast tumorigenesis.

Neuropilin2 expressed in gastric cancer endothelial cells increases the proliferation and migration of endothelial cells in response to VEGF

The structure and characteristics of the tumor vasculature are known to be different from those of normal vessels. Neuropilin2 (Nrp2), which is expressed in non-endothelial cell types, such as neuronal or cancer cells, functions as a receptor for both semaphorin and vascular endothelial growth factor (VEGF). After isolating tumor and normal endothelial cells from advanced gastric cancer tissue and normal gastric mucosa tissues, respectively, we identified genes that were differentially expressed in gastric tumor endothelial (TEC) and normal endothelial cells (NEC) using DNA oligomer chips. Using reverse transcriptase-PCR, we confirmed the chip results by showing that Nrp2 gene expression is significantly up-regulated in TEC. Genes that were found to be up-regulated in TEC were also observed to be up-regulated in human umbilical vein endothelial cells (HUVECs) that were co-cultured with gastric cancer cells. In addition, HUVECs co-cultured with gastric cancer cells showed an increased reactivity to VEGF-induced proliferation and migration. Moreover, overexpression of Nrp2 in HUVECs significantly enhanced the proliferation and migration induced by VEGF. Observation of an immunohistochemical analysis of various human tumor tissue arrays revealed that Nrp2 is highly expressed in the tumor vessel lining and to a lesser extent in normal tissue microvessels. From these results, we suggest that Nrp2 may function to increase the response to VEGF, which is more significant in TEC than in NEC given the differential expression, leading to gastric TEC with aggressive angiogenesis phenotypes.

P2Y2 receptor desensitization on single endothelial cells

Receptor desensitization, or decreased responsiveness of a receptor to agonist stimulation, represents a regulatory process with the potential to have a significant impact on cell behavior. P2Y(2), a G-protein-coupled receptor activated by extracellular nucleotides, undergoes desensitization at many tissues, including the vascular endothelium. Endothelial cells from a variety of vascular beds are normally exposed to extracellular nucleotides released from damaged cells and activated platelets. The purpose of the present study was to compare P2Y(2) receptor desensitization observed in endothelial cells derived from bovine retina, a model of microvascular endothelium, and human umbilical vein endothelial cells (HUVECs), a model of a large blood vessel endothelium. P2Y(2) receptor desensitization was monitored by following changes in UTP-stimulated intracellular free Ca(2 +) in single cells using fura-2 microfluorometry. Both endothelial cell models exhibited desensitization of the P2Y(2) receptor after stimulation with UTP. However, the cells differed in the rate, dependence on agonist concentration, and percentage of maximal desensitization. These results suggest differential mechanisms of P2Y(2) receptor desensitization and favors heterogeneity in extracellular nucleotide activity in endothelial cells according to its vascular bed origin.

Human fetal placental endothelial cells have a mature arterial and a juvenile venous phenotype with adipogenic and osteogenic differentiation potential

Growing interest in the sources of origin of blood vessel related diseases has led to an increasing knowledge about the heterogeneity and plasticity of endothelial cells lining arteries and veins. So far, most of these studies were performed on animal models. Here, we hypothesized that the plasticity of human fetal endothelial cells depends on their vascular bed of origin i.e. vein or artery and further that the differences between arterial and venous endothelial cells would extend to phenotype and genotype. We established a method for the isolation of fetal arterial and venous endothelial cells from the human placenta and studied the characteristics of both cell types. Human placental arterial endothelial cells (HPAEC) and human placental venous endothelial cells (HPVEC) express classical endothelial markers and differ in their phenotypic, genotypic, and functional characteristics: HPAEC are polygonal cells with a smooth surface growing in loose arrangements and forming monolayers with classical endothelial cobblestone morphology. They express artery-related genes (hey-2, connexin 40, depp) and more endothelial-associated genes than HPVEC. Functional testing demonstrated that vascular endothelial growth factors (VEGFs) induce a higher proliferative response on HPAEC, whereas placental growth factors (PlGFs) are only effective on HPVEC. HPVEC are spindle-shaped cells with numerous microvilli at their surface. They grow closely apposed to each other, form fibroblastoid swirling patterns at confluence and have shorter generation and population doubling times than HPAEC. HPVEC overexpress development-associated genes (gremlin, mesenchyme homeobox 2, stem cell protein DSC54) and show an enhanced differentiation potential into adipocytes and osteoblasts in contrast to HPAEC. These data provide collective evidence for a juvenile venous and a more mature arterial phenotype of human fetal endothelial cells. The high plasticity of the fetal venous endothelial cells may reflect their role as tissue-resident endothelial progenitors during embryonic development with a possible benefit for regenerative cell therapy.

Hypoxia-induced increase of endostatin in murine aorta and lung

In the lung, hypoxia induces pulmonary hypertension caused by vasoconstriction and vascular remodeling. Additionally, hypoxia is an inducer of angiogenesis, which is assumed to counteract pulmonary hypertension. We asked whether the anti-angiogenic factor endostatin--a cleavage product of collagen XVIII--participates in the vascular alterations induced by hypoxia. By employing Western blotting of tissue extracts of murine brain, liver and heart an endostatin fragment of 22 kDa was detectable, whereas in lung and aorta additional bands of 24 and 26 kDa were found. The amount of these larger fragments was increased in tissues obtained from mice housed for 4 days or 3 weeks at hypobaric hypoxia. By immunohistochemistry endostatin was detected in association with elastic fibers and in close neighborhood to smooth muscle cells of intrapulmonary vessels and the aorta. In the lung, the activity of matrix metalloproteinases (MMP) known to generate endostatin by cleavage of collagen XVIII was increased (MMP-2) and decreased (proMMP-9), respectively, by hypoxia. Elevated amounts of endostatin within the aortic wall of mice exposed to hypobaric hypoxia may stabilize the vascular wall by inhibition of microvascular sprouting. The surprising finding of increased endostatin in the lung presumably contributes to the development of pulmonary hypertension by reduction of angiogenesis.

Endostatin signaling and regulation of endothelial cell-matrix interactions

The growth and survival of a malignant tumor are dependent on the formation and maintenance of its own microvasculature, a process termed angiogenesis. Inhibition of this phenomenon is an emerging strategy in cancer therapy. The extracellular matrix surrounding the vascular endothelial cells contains cryptic protein domains, which are exposed by changes in the proteolytic homeostasis of the tumor microenvironment. These fragments transmit local signals, which regulate vascular endothelial cell proliferation and migration. Endostatin, the proteolytic fragment of collagen type XVIII, is a potent inhibitor of tumor angiogenesis in various mouse models and is currently in clinical trials for therapeutic use in human cancer. Multiple cell surface receptors have been described for endostatin, but the signals transmitted by these receptors resulting in the inhibition of angiogenesis have so far been poorly characterized. Studies on the effects of endostatin on cultured endothelial cells suggest that the antimigratory and antiproliferative properties of this molecule are the major mechanisms underlying its antiangiogenic potential. These effects may be a consequence of endostatin modulation of endothelial cell-matrix interactions and pericellular proteolysis.

Inhibitors of cytochrome P450 4A suppress angiogenic responses

Cytochrome P450 enzymes of the 4A family (CYP4A) convert arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE) in blood vessels of several vascular beds. The present study examined the effects of inhibiting the formation of 20-HETE with N-hydroxy-N'-(4-butyl-2-methylphenol) formamidine (HET0016) on the mitogenic response of vascular endothelial growth factor (VEGF) in human umbilical vein endothelial cells (HUVECs) in vitro, and on growth factor-induced angiogenesis in the cornea of rats in vivo. HET0016 (10 micromol/L and 20 microg, respectively) abolished the mitogenic response to VEGF in HUVECs and the angiogenic response to VEGF, basic fibroblast growth factor, and epidermal growth factor in vivo by 80 to 90% (P < 0.001). Dibromododecenyl methylsulfonimide (DDMS), a structurally and mechanistically different inhibitor of 20-HETE synthesis, also abolished angiogenic responses when tested with VEGF. Additionally, administration of the stable 20-HETE agonist, 20-hydroxyeicosa-6(Z) 15(Z)-dienoic acid (WIT003) induced mitogenesis in HUVECs and angiogenesis in the rat cornea in vivo. We studied the ability of HET0016 to alter the angiogenic response in the rat cornea to human glioblastoma cancer cells (U251). When administered locally into the cornea, HET0016 (20 microg) reduced the angiogenic response to U251 cancer cells by 70%. These results suggest that a product of CYP4A product, possibly 20-HETE, plays a critical role in the regulation of angiogenesis and may provide a useful target for reduction of pathological angiogenesis.

In vitro endothelial cell susceptibility to xenobiotics: Comparison of three cell types

In three different endothelial cell (EC) cultures (primary human umbilical cord vein, so-called HUVEC; and immortalized cell lines HBMEC and EA-hy-926), the effects of different xenobiotics were studied in order to standardize vascular EC models for in vitro pharmacotoxicological studies. Cell characteristics were first investigated by the production and the mRNA levels of known endothelial markers in the three EC culture models. EC secretory products, tissue plasminogen activator (tPA) and von Willebrand factor (vWF), were present in the supernatant of the immortalized cell lines. The mRNA levels of vWF, tPA, platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31), and beta -integrin subunit, which are involved in the control of platelet function, coagulation, and fibrinolysis as well as in cell-matrix interactions, were investigated in all EC types. For at least three parameters, cultured cells provided marked characteristics of EC phenotype, in HUVEC and in immortalized cell lines, regardless of their origin from the macro- or microcirculation. Toxicity experiments were assessed after 24 h exposure to cadmium, cyclosporin A and cisplatin by MTT assay. These experiments show nonsignificant difference in susceptibility to cyclosporin A and cadmium on HUVEC, HBMEC, and EA-hy-926. However, HBMEC, seems to be highly susceptible to cisplatin compared to HUVEC, the latter being more sensitive than EA-hy-926. For experiments conducted with cyclosporin and cadmium, cell lines could constitute an alternative material for routine cytotoxicity studies.

Role of human cripto-1 in tumor angiogenesis

BACKGROUND

Human cripto-1 (CR-1) promotes cell transformation and increases migration and invasion of various mouse and human epithelial cell lines. We investigated whether CR-1 also stimulates angiogenesis.

METHODS

We used human umbilical vein endothelial cells (HUVECs) to measure in vitro migration with fibronectin-coated Boyden chambers, invasion with Matrigel-coated Boyden chambers, proliferation with a tetrazolium salt, and differentiation with an in vitro Matrigel assay. We investigated new blood vessel formation in vivo by use of Matrigel-filled silicone cylinders implanted under the skin of nude mice and by use of a breast cancer xenograft model with CR-1-transfected or control Neo-transfected MCF-7 human breast cancer cells. We also used a blocking anti-CR-1 monoclonal antibody to investigate the role of CR-1 in angiogenesis in vivo and in vitro. All statistical tests were two-sided.

RESULTS

CR-1 stimulated HUVEC proliferation, migration, and invasion and induced HUVEC differentiation into vascular-like structures on Matrigel. In vivo, recombinant CR-1 protein induced microvessel formation in Matrigel-filled silicone cylinders, and microvessel formation was statistically significantly inhibited with a blocking anti-CR-1 monoclonal antibody (CR-1 and antibody = 127% of microvessel formation compared with that in untreated control cylinders and CR-1 alone = 259%; difference = 132%, 95% confidence interval [CI] = 123% to 140%; P<.001). Tumors formed by CR-1-transfected MCF-7 cells in the cleared mammary fat pad of nude mice had higher microvessel density than tumors formed by control Neo-transfected MCF-7 cells (CR-1-transfected cells = 4.66 vessels per field and Neo-transfected cells = 2.33 vessels per field; difference = 2.33 vessels per field, 95% CI = 1.2 to 2.8; P = .004).

CONCLUSION

CR-1 appears to have an important role in the multistep process of angiogenesis.

Plasmalemmal vesicle-associated protein (PLVAP) is expressed by tumour endothelium and is upregulated by vascular endothelial growth factor-A (VEGF)

Vascular endothelial growth factor-A (VEGF) is an important regulator of vascular permeability. In preclinical studies, VEGF induces endothelial fenestrations in pre-existing and neo-vasculature, while inhibition of VEGF leads to a reduction in endothelial fenestrations. Recently, vascular regression in response to VEGF inhibition has been shown to correlate with the presence of endothelial fenestrations. Plasmalemmal vesicle-associated protein (PLVAP) is believed to be a component of diaphragmed endothelial fenestrations, but a direct relationship with VEGF signalling has not been established. The aim of this study was to characterize the expression pattern of PLVAP and investigate whether PLVAP is a transcriptional target of VEGF signal transduction. The expression pattern of PLVAP was characterized in normal and neoplastic human tissues by in situ hybridization and/or immunohistochemistry. The role of VEGF signal transduction in the regulation of PLVAP expression was investigated in vitro using receptor-selective engineered forms of VEGF, a neutralizing monoclonal antibody against VEGF, and inhibitors of downstream signalling pathways. PLVAP mRNA and protein were widely expressed in the endothelium of normal and neoplastic tissues. In cultured endothelial cells, VEGF signalling through receptor 2 stimulated expression of PLVAP total RNA and protein. This induction could be blocked with an anti-VEGF monoclonal antibody and by inhibitors of phosphatidylinositol 3-kinase (LY294002) or p38 mitogen-activated protein kinase (SB203580), but not by PD98059, a mitogen-activated protein/extracellular signal-regulated kinase 1 inhibitor. These data show that PLVAP is more widely expressed in the vasculature of normal tissues than previously thought and that it is expressed in the vasculature of most human tumours. We suggest that PLVAP is a downstream target of VEGF signalling. This work solidifies the association between VEGF and the appearance and maintenance of fenestrations by providing a potential mechanistic link.

Red blood cells inhibit proliferation and stimulate apoptosis in human lung fibroblasts in vitro

Cell proliferation and apoptosis are both important mechanisms for the regulation of tissue homeostasis. For instance, proliferation is crucial in wound repair, whereas apoptosis is important for removal of damaged cells and resolution of inflammation. Imbalance between cell proliferation and apoptosis can therefore lead to pathological conditions and disease. In inflammatory and fibrotic lung disorders, red blood cells (RBCs) can interact with fibroblasts and connective tissue. In the present study, we therefore hypothesized that the presence of RBCs can affect fibroblast proliferation and apoptosis. Human foetal lung fibroblasts (HFL-1) were cultured in the presence or absence of purified whole RBCs and RBC-conditioned media. RBC significantly decreased fibroblast proliferation as determined both by DNA content analysis (Hoechst 33258 staining, P < 0.01; WST-1, P < 0.001) and BrdU incorporation. After treatment with staurosporine (STS) for 48 h, apoptosis was determined by TUNEL and propidium iodide staining followed by flow cytometry analysis. RBCs augmented STS-induced apoptosis (median: 46.4%; range 12.0-90.4) compared to control cells (median 26.2%; range 7.1-45.5). Thus, our data indicate that the presence of RBCs affects both fibroblast proliferation and susceptibility to undergo apoptosis. Our findings therefore suggest a role for RBCs in regulating fibroblast homeostasis after tissue injury.

Effects of aspirin and indomethacin on endothelial cell proliferation in vitro

BACKGROUND AND AIM

Non-steroidal anti-inflammatory drugs (NSAID) are associated with delayed peptic ulcer healing. Ulcer healing is dependent on angiogenesis, which requires endothelial cell (EC) proliferation. The present study aimed to determine whether NSAID and prostaglandin E2 (PGE2) inhibited EC proliferation in vitro.

METHODS

Effects of 50 micro L aspirin (10 micro M-1 mM), indomethacin (10 micro M-1 mM) and PGE2 (1 micro M-0.1 mM) on the proliferation, viability and cell cycle of human dermal microvascular (HuDMEC) and human umbilical vein (HUVEC) EC were assessed using dual staining cell viability, 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide and flow cytometry assays.

RESULTS

Proliferation of HuDMEC and HUVEC was significantly inhibited by 0.1 mM/1 mM indomethacin, 1 mM aspirin and 100 micro M PGE2, with a significant (P < 0.05) increase in EC necrosis with 1 mM indomethacin and 100 micro M PGE2. No effects on cell cycle were demonstrated.

CONCLUSIONS

High concentrations of NSAID inhibit both HuDMEC and HUVEC proliferation in vitro by cytotoxic (indomethacin) or cytostatic (aspirin and indomethacin) mechanisms. Interestingly, PGE2 was also antiproliferative. Inhibition of EC proliferation may prevent angiogenesis at the ulcer site, which may in part explain the delayed ulcer healing associated with NSAID.

Heterogeneity of microvascular endothelial cells isolated from human term placenta and macrovascular umbilical vein endothelial cells

The present study compares some phenotypic and physiologic characteristics of microvascular and macrovascular endothelial cells from within one human organ. To this end microvascular endothelial cells from human full-term placenta (PLEC) were isolated using a new method and compared with macrovascular human umbilical vein endothelial cells (HUVEC) and an SV40-transformed placental venous endothelial cell line (HPEC-A2). PLEC were isolated by enzymatic perfusion of small placental vessels, purified on a density gradient and cultured subsequently. Histological sections of the enzyme-treated vessels showed a selective removal of the endothelial lining in the perfused placental cotyledons. The endothelial identity of the cells was confirmed by staining with the endothelial markers anti-von Willebrand factor, Ulex europaeus lectin and anti-QBEND10. The cells internalized acetylated low-density lipoprotein and did not show immunoreactivity with markers for macrophages, smooth muscle cells and fibroblasts. The spindle-shaped PLEC grew in swirling patterns similar to that described for venous placental endothelial cells. However, scanning electron microscopic examination clearly showed that PLEC remained elongated at the confluent state, in contrast to the more polygonal phenotype of HPEC-A2 and HUVEC that were studied in parallel. The amount of vasoactive substances (endothelin-1,2, thromboxane, angiotensin II, prostacyclin) released into the culture medium and the proliferative response to cytokines was more similar to human dermal microvessels (MIEC) derived from non-fetal tissue than to HUVEC. Potent mitogens such as vascular endothelial growth factors (VEGF121, VEGF165) and basic fibroblast growth factor (FGF-2) induced proliferation of all endothelial cell types. Placental growth factors PIGF-1 and PIGF-2 effectively stimulated cell proliferation on PLEC (142 +/- 7% and 173 +/- 10%) and MIEC (160 +/- 20% and 143 +/- 28%) in contrast to HUVEC (9 +/- 8% and 15 +/- 20%) and HPEC-A2 (15 +/- 7% and 24 +/- 6%) after 48 h incubation time under serum-free conditions. These data support evidence for (1) the microvascular identity of the isolated PLEC described in this study, and (2) the phenotypic and physiologic heterogeneity of micro- and macrovascular endothelial cells within one human organ.

TWEAK is an endothelial cell growth and chemotactic factor that also potentiates FGF-2 and VEGF-A mitogenic activity

OBJECTIVE

TWEAK, a member of the tumor necrosis factor superfamily, binds to the Fn14 receptor and stimulates angiogenesis in vivo. In this study, we investigated Fn14 gene expression in human endothelial cells (ECs) and examined the effect of TWEAK, added either alone or in combination with fibroblast growth factor-2 (FGF-2) or vascular endothelial growth factor-A (VEGF-A), on EC proliferation, migration, and survival in vitro. We also determined whether a soluble Fn14-Fc fusion protein could inhibit TWEAK biologic activity on ECs and investigated TWEAK signal transduction in ECs.

METHODS AND RESULTS

We found that both FGF-2 and VEGF-A could induce Fn14 mRNA expression in ECs. TWEAK was a mitogen for ECs, and this proliferative activity could be inhibited by an Fn14-Fc decoy receptor. Furthermore, TWEAK treatment activated several intracellular signaling pathways in ECs and potentiated FGF-2--and VEGF-A--stimulated EC proliferation. TWEAK also had EC chemotactic activity, but it did not promote EC survival.

CONCLUSIONS

These results indicate that TWEAK is an EC growth and migration factor but not a survival factor. TWEAK can also enhance both FGF-2 and VEGF-A mitogenic activity on ECs. Thus, TWEAK may act alone as well as in combination with FGF-2 or VEGF-A to regulate pathological angiogenesis.

Endothelial cells release phenotypically and quantitatively distinct microparticles in activation and apoptosis

BACKGROUND

Endothelial cells (EC) shed endothelial microparticles (EMP) in activation and apoptosis.

OBJECTIVES

We compared the antigenic expression of EMP species released during activation as compared to apoptosis, in three cell lines.

METHODS

EC from renal and brain microvascular (MiVEC) and coronary macrovascular (MaVEC) origin were incubated with TNF-alpha to induce activation, or deprived of growth factors to induce apoptosis. Antigens expressed on EMP and EC were assayed flow cytometrically and included constitutive markers (CD31, CD51/61, CD105), inducible markers (CD54, CD62E and CD106), and annexin V binding.

RESULTS

It was found that in apoptosis, constitutive markers in EMP were markedly increased (CD31>CD105), with a concomitant decrease in expression in EC. Annexin V EC surface binding and annexin V+ EMP were more sharply increased in apoptosis than in activation. In contrast, in activation, inducible markers in EMP were markedly increased in both EMP and EC (CD62E>CD54>CD106). Coronary MaVEC released significantly less EMP than MiVEC.

CONCLUSION

EC release qualitatively and quantitatively distinct EMP during activation compared to apoptosis. Analysis of EMP phenotypic signatures may provide clinically useful information on the status of the endothelium.

Microarray analysis reveals the involvement of beta-2 microglobulin (B2M) in human osteoarthritis

OBJECTIVE

To assess whether beta-2 microglobulin (B2M) has effects on articular chondrocytes that would implicate B2M involvement in osteoarthritis (OA) pathogenesis.

METHODS

The mRNA levels of B2M in fetal and osteoarthritic chondrocytes were detected by RT-PCR. B2M levels in synovial fluid and tissue cultured media from cartilage explants were tested using B2M ELISA kit. Primary cultured chondrocytes were used for proliferation and microarray experiments.

RESULTS

The average B2M level in OA synovial fluid is significantly higher than that found in normal synovial fluid. However, there was no significant difference in B2M synovial fluid levels amongst differing OA stages. The release of B2M by osteoarthritic cartilage was detectable after 24h in culture and continued to increase during the 72 h study period. B2M had an inhibitory effect on chondrocyte growth at 1.0 microg/ml, and became significantly inhibitory at 10.0 microg/ml. Genes regulated by B2M were detected through microarray technology. Twenty genes were found to be up-regulated by B2M, including collagen type III which is known to be up-regulated in OA. Eleven genes were found to be down-regulated at least two-fold by B2M.

CONCLUSION

These results indicate that B2M is highly expressed in OA cartilage and synovial fluid compared to normal, and suggest that B2M may have effects on chondrocyte function that could contribute to OA pathogenesis. Published by Elsevier Science Ltd.

Heterogeneity of bronchial endothelial cell permeability

In vivo models of airway inflammation suggest that most protein transudation occurs from bronchial microcirculation. However, due to technical limitations in the isolation and culture of bronchial endothelial cells, most studies of lung vascular permeability have focused on pulmonary endothelium. Thus conditions for culture of sheep bronchial artery endothelial cells (BAEC) and bronchial microvascular endothelial cells (BMVEC) were established. The bronchial artery and the mainstem bronchi, stripped of epithelium, were dissected, and endothelial cells were isolated by enzymatic treatment. BAEC and BMVEC demonstrated positive staining for factor VIII-related antigen, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate-labeled low-density lipoprotein, and PECAM-1. Radioligand binding studies confirmed equivalent numbers of bradykinin B(2) receptors on BAEC and BMVEC. Permeability of BAEC and BMVEC was determined after treatment with bradykinin and thrombin by comparing the translocation of FITC-dextran (mol wt 9,500) across confluent monolayers (n = 10-12). Bradykinin caused a maximal increase in permeability in BAEC (165% increase) and BMVEC (144% increase) by 15 min compared with vehicle controls. Thrombin treatment altered BMVEC permeability only, reaching a maximal response at 60 min (109% increase). These results demonstrate bronchial endothelial cell heterogeneity and establish methods to determine intracellular mechanisms contributing to airway disease in relevant cell systems.

Isolation and culture of rat microvascular endothelial cells

The purpose of this study is to identify the separation techniques that result in pure cultures of rat microvascular endothelial cells (MECs). A multistep process is used to optimize the separation of the cells from rat epididymal fat pads, obtaining as pure a culture as possible within a relatively short processing time. The process initially employs the digestion, filtration, and density gradient separation steps. We further describe the use of an attachment phase that allows the differential adherence of contaminating cell types. Immunomagnetic purification is the final step in the process and is performed using anti-PECAM-1 (CD31) monoclonal antibody-labeled DynaBeads.