Synthesis of disaccharides derived from heparin and evaluation of effects on endothelial cell growth and on binding of heparin to FGF-2

The disaccharide beta-D-GlcA-(1-->4)-alpha-D-GlcNAc-1-->OMe and other small nonsulfated oligosaccharides related to heparin/heparan sulfate have been shown to bind to FGF and activated the fibroblast growth factor (FGF) signalling pathway in (F32) cells expressing the FGF receptor. Synthetic routes to beta-D-GlcA-(1-->4)-alpha-D-GlcNAc-1-->OMe and a glucose analogue beta-D-Glc-(1-->4)-alpha-D-GlcNAc-1-->OMe are described. The effects of these disaccharides on endothelial cell growth, which is relevant to angiogenesis, were evaluated and it was found they did not mimic the inhibitory effects that were observed for heparin albumin (HA) and that have also been observed by monosaccharide conjugates. They did not alter bovine aortic endothelial cell (BAEC) proliferation, in the presence of FGF-2 in serum free medium or in absence of FGF-2 in serum free and complete medium. Disaccharides (10 microg/mL) reduced by 25-31% the inhibition caused by HA (10 microg/mL) on BAEC growth in serum-free medium but had no effect in complete medium. There was no evidence obtained for the binding of these oligosaccharides to FGF-2 in competition with HA by ELISA.     

Alternatively spliced FGFR-1 isoforms differentially modulate endothelial cell activation of c-YES

Ligand activation of fibroblast growth factor receptor-1 (FGFR-1) induces an angiogenic response following activation of multiple intracellular signaling substrates, including the Src family of nonreceptor tyrosine kinases (SFK). However, the direct association between FGFR-1 and SFK and the involvement of SFK in FGFR-1-dependent cell proliferation have been controversial. Structural variants of FGFR-1 are generated by alternative splicing which results in two major isoforms, containing either three (FGFR-1α) or two (FGFR-1β) immunoglobulin-like domains in the extracellular region. To determine whether alternatively spliced FGFR-1 isoforms differentially activate SFK, we have examined FGF receptor-negative endothelial cells stably transfected with human cDNA encoding either FGFR-1α or FGFR-1β. Transient activation of c-YES, the predominant SFK expressed in these endothelial cells, was restricted to FGFR-1β transfectants following exposure to acidic fibroblast growth factor (FGF-1). Co-immunoprecipitation studies revealed that c-YES directly associated with FGFR-1β. The Src homology (SH)2 domain (and not the SH3 domain) of c-YES was able to recognize tyrosine phosphorylated FGFR-1β. FGFR-1β-specific activation of c-YES was accompanied by its association with and activation of cortactin. FGF-1 treatment of both FGFR-1α and FGFR-1β transfectants induced SFK-independent cellular proliferation and growth in low density cultures. At high density, under both anchorage-dependent and -independent conditions, FGF-1 failed to induce proliferation and growth of FGFR-1α transfectants. In contrast, FGF-1 induced proliferation, growth, and formation of cord-like structures in high density cultures of FGFR-1β transfectants in an SFK-dependent manner. In vitro cord formation on Matrigel was restricted to FGFR-1β transfectants in an SFK-dependent manner. Formation of vascular structures in vivo was limited to endothelial cells transfected with FGFR-1β. Collectively, these results emphasize the roles of alternatively spliced FGFR-1 structural isoforms and activation of SFK as modulators of endothelial cell growth during the formation of neovascular structures.     

Dissociation of ERK and Akt signaling in endothelial cell angiogenic responses to beta-amyloid

Cerebrovascular deposits of beta-amyloid (Abeta) peptides are found in Alzheimer's disease and cerebral amyloid angiopathy with stroke or dementia. Dysregulations of angiogenesis, the blood-brain barrier and other critical endothelial cell (EC) functions have been implicated in aggravating chronic hypoperfusion in AD brain. We have used cultured ECs to model the effects of beta-amyloid on the activated phosphorylation states of multifunctional serine/threonine kinases since these are differentially involved in the survival, proliferation and migration aspects of angiogenesis. Serum-starved EC cultures containing amyloid-beta peptides underwent a 2- to 3-fold increase in nuclear pyknosis. Under growth conditions with sublethal doses of beta-amyloid, loss of cell membrane integrity and inhibition of cell proliferation were observed. By contrast, cell migration was the most sensitive to Abeta since inhibition was significant already at 1 muM (P = 0.01, migration vs. proliferation). In previous work, intracellular Abeta accumulation was shown toxic to ECs and Akt function. Here, extracellular Abeta peptides do not alter Akt activation, resulting instead in proportionate decreases in the phosphorylations of the MAPKs: ERK1/2 and p38 (starting at 1 microM). This inhibitory action occurs proximal to MEK1/2 activation, possibly through interference with growth factor receptor coupling. Levels of phospho-JNK remained unchanged. Addition of PD98059, but not LY294002, resulted in a similar decrease in activated ERK1/2 levels and inhibition of EC migration. Transfection of ERK1/2 into Abeta-poisoned ECs functionally rescued migration. The marked effect of extracellular Abeta on the migration component of angiogenesis is associated with inhibition of MAPK signaling, while Akt-dependent cell survival appears more affected by cellular Abeta.     

Hypoxia-induced mitogenic factor enhances angiogenesis by promoting proliferation and migration of endothelial cells

Our previous studies have indicated that hypoxia-induced mitogenic factor (HIMF) has angiogenic properties in an in vivo matrigel plug model and HIMF upregulates expression of vascular endothelial growth factor (VEGF) in mouse lungs and cultured lung epithelial cells. However, whether HIMF exerts angiogenic effects through modulating endothelial cell function remains unknown. In this study, mouse aortic rings cultured with recombinant HIMF protein resulted in enhanced vascular sprouting and increased endothelial cell spreading as confirmed by Dil-Ac-LDL uptake, von Willebrand factor and CD31 staining. In cultured mouse endothelial cell line SVEC 4-10, HIMF dose-dependently enhanced cell proliferation, in vitro migration and tubulogenesis, which was not attenuated by SU1498, a VEGFR2/Flk-1 receptor tyrosine kinase inhibitor. Moreover, HIMF stimulation resulted in phosphorylation of Akt, p38 and ERK1/2 kinases in SVEC 4-10 cells. Treatment of mouse aortic rings and SVEC 4-10 cells with LY294002, but not SB203580, PD098059 or U0126, abolished HIMF-induced vascular sprouting and angiogenic responses. In addition, transfection of a dominant-negative mutant of phosphatidylinositol 3-kinase (PI-3K), Deltap85, blocked HIMF-induced phosphorylation of Akt, endothelial activation and tubulogenesis. These results indicate that HIMF enhances angiogenesis by promoting proliferation and migration of endothelial cells via activation of the PI-3K/Akt pathways.     

Adiponectin promotes endothelial progenitor cell number and function

Obesity-linked diseases are associated with suppressed endothelial progenitor cell (EPC) function. Adiponectin is an adipose-derived protein that is downregulated in obese and diabetic subjects. Here, we investigated the effects of adiponectin on EPCs. EPC levels did not increase in adiponectin deficient (APN-KO) in response to hindlimb ischemia. Adenovirus-mediated delivery of adiponectin increased EPC levels in both WT and APN-KO mice. Incubation of human peripheral blood mononuclear cells with adiponectin led to an increase of the number of EPCs. Adiponectin induced EPC differentiation into network structures and served as a chemoattractant in EPC migration assays. These data suggest that hypoadiponectinemia may contribute to the depression of EPC levels that are observed in patients with obesity-related cardiovascular disorders.     

Vascular endothelial growth factor increases the intracellular magnesium

Vascular endothelial growth factor (VEGF) is one of the key players in the process of angiogenesis. However, its underlying mechanism remains unclear. Mg2+ is the most abundant intracellular divalent cation in the body and plays critical roles in many cell functions. We investigated the effect of VEGF on intracellular Mg2+ in human umbilical vein endothelial cells (HUVECs). VEGF-A165 increased the intracellular Mg2+ concentration ([Mg2+]i) in a dose-dependent manner, with or without extracellular Mg2+, and the increase of [Mg2+]i was blocked by pretreatment with SU1498, tyrosine kinase inhibitors (tyrphostin A-23 and genistein), phosphatidylinositol 3-kinase (PI3K) inhibitors (wortmannin and LY294002) or phospholipase Cgamma (PLCgamma) inhibitor (U73122). In contrast, mitogen-activated protein kinase inhibitors (SB202190 and PD98059) had no effect on the VEGF-induced [Mg2+]i increase. These results suggest that VEGF-A165 increases the [Mg2+]i from the intracellular Mg2+ stores through the tyrosine kinase/PI3K/PLCgamma-dependent signaling pathways.     

N-Glycosyl-thiophene-2-carboxamides: synthesis, structure and effects on the growth of diverse cell types

A range of N-glycosyl-thiophene-2-carboxamides, including a 6H-thieno[2,3-c]pyridin-7-one and a bivalent compound, have been synthesised and assayed for their effects on DNA synthesis in bovine aortic endothelial cells or on the growth of synoviocytes. Per-O-acetylated analogues of the glycoconjugates were significantly more effective inhibitors when compared to their corresponding non-acetylated analogues, indicating that the lower potency observed for hydroxylated derivatives is due to less efficient transport of these compounds across the cell membrane. Thiophene-2-carboxamide was inactive as an inhibitor of bFGF induced proliferation, confirming the requirement of the carbohydrate residue for the observed biological properties. Glucose, mannose, galactose and 2-amino-2-deoxy-glucose analogues were active as were a variety of substituted thiophene derivatives; the 6H-thieno[2,3-c]pyridin-7-one conjugate was inactive. Conformational analysis of the title compounds was investigated. X-ray crystal structural analysis of four N-glucosyl-thiophene-2-carboxamides showed that the pyranose rings adopted the expected 4C1 conformations and that Z-anti structures were predominant (H1-C1-N-H anomeric torsion angle varied from -168.2 degrees to -175.0 degrees ) and that the carbonyl oxygen and sulfur of the thiophene adopted an s-cis conformation in three of the isomers. In a crystal structure of a 3-alkynyl derivative, the hydrogen atom of the NH group was directed toward the acetylene group. The distance between the hydrogen atom and acetylene carbons and angles between nitrogen, hydrogen and carbon atoms were consistent with hydrogen bonding and this was supported by IR and NMR spectroscopic studies. The geometries of thiophene-2-carboxamides were explored by density functional theory (DFT) and M?ller-Plesset (MP2) calculations and the s-cis conformer of thiophene-2-carboxamide was found to be more stable than its s-trans isomer by 0.83 kcal mol(-1). The s-cis conformer of 3-ethynyl-thiophene-2-carboxamide was 5.32 kcal mol(-1) more stable than the s-trans isomer. The larger stabilisation for the s-cis conformer in the 3-alkynyl derivatives is explained to be due to a moderate hydrogen bonding interaction between the alkyne and NH group.     

Protein kinases as mediators of fluid shear stress stimulated signal transduction in endothelial cells: A hypothesis for calcium-dependent and calcium-independent events activated by flow

Fluid shear stress regulates endothelial cell function, but the signal transduction mechanisms involved in mechanotransduction remain unclear. Recent findings demonstrate that several intracellular kinases are activated by mechanical fórces. In particular, members of the mitogen-activated protein (MAP) kinase family are stimulated by hyperosmolárity, stretch, and stress such as heat shock. We propose a model for mechanotransduction in endothelial cells involving calcium-dependent and calcium-independent protein kinase pathways. The calcium-dependent pathway involves activation of phospholipase C, hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP₂), increases in intracellular calcium and stimulation of kinases such as calcium-calmodulin and C kinases (PKC). The calcium-independent pathway involves activation of a small GTP-binding protein and stimulation of calcium-independent PKC and MAP kinases. The calcium-dependent pathway mediates the rapid, transient response to fluid shear stress including activation of nitric oxide synthase (NOS) and ion transport. In contrast, the calcium-independent pathway mediates a slower response including the sustained activation of NOS and changes in cell morphology and gene expression. We propose that focal adhesion complexes link the calcium-dependent and calcium-independent pathways by regulating activity of phosphatidylinositol 4-phosphate (PIP) 5-kinase (which regulates PIP₂ levels0 and p125 focal adhesion kinase (FAK, which phosphorylates paxillin and interacts with cytoskeletal proteins). This model predicts that dynamic interactions between integrin molecules present in focal adhesion complexes and membrane events involved in mechanotransduction will be integrated by calcium-dependent and calcium-independent kinases to generate intracellular signals involved in the endothelial cell response to flow.     

Hepatocyte growth factor induces angiogenesis in injured lungs through mobilizing endothelial progenitor cells

Circulating endothelial progenitor cells (EPCs) play a pivotal role in angiogenesis. Hepatocyte growth factor (HGF) is known to induce proliferation and motility in endothelial cells, and to play a role in mitogenic and morphogenic actions. However, the role of HGF in EPC mobilization has not been clearly described yet. We investigated the effect of HGF on mobilizing EPCs and on angiogenesis in elastase-induced lung injury. HGF significantly increased the triple-positive (Sca-1(+), Flk-1(+), and c-kit(+)) fraction in peripheral mononuclear cells in mice. The bone marrow-derived cells were recruited into the injured lungs, where they differentiated to capillary endothelial cells. HGF induced proliferation of both bone marrow-derived and resident endothelial cells in the alveolar wall. In conclusion, the present study suggests that HGF induces EPC mobilization from the bone marrow and enhances the proliferation of endothelial cells in vivo. These complex effects induced by HGF orchestrate pulmonary regeneration in emphysematous lung parenchyma.     

Leptin-induced transphosphorylation of vascular endothelial growth factor receptor increases Notch and stimulates endothelial cell angiogenic transformation

Leptin increases vascular endothelial growth factor (VEGF), VEGF receptor-2 (VEGFR-2), and Notch expression in cancer cells, and transphosphorylates VEGFR-2 in endothelial cells. However, the mechanisms involved in leptin’s actions in endothelial cells are not completely known. Here we investigated whether a leptin-VEGFR-Notch axis is involved in these leptin’s actions. To this end, human umbilical vein and porcine aortic endothelial cells (wild type and genetically modified to overexpress VEGFR-1 or -2) were cultured in the absence of VEGF and treated with leptin and inhibitors of Notch (gamma-secretase inhibitors: DAPT and S2188, and silencing RNA), VEGFR (kinase inhibitor: SU5416, and silencing RNA) and leptin receptor, OB-R (pegylated leptin peptide receptor antagonist 2: PEG-LPrA2). Interestingly, in the absence of VEGF, leptin induced the expression of several components of Notch signaling pathway in endothelial cells. Inhibition of VEGFR and Notch signaling significantly decreased leptin-induced S-phase progression, proliferation, and tube formation in endothelial cells. Moreover, leptin/OB-R induced transphosphorylation of VEGFR-1 and VEGFR-2 was essential for leptin’s effects. These results unveil for the first time a novel mechanism by which leptin could induce angiogenic features via upregulation/trans-activation of VEGFR and downstream expression/activation of Notch in endothelial cells. Thus, high levels of leptin found in overweight and obese patients might lead to increased angiogenesis by activating VEGFR-Notch signaling crosstalk in endothelial cells. These observations might be highly relevant for obese patients with cancer, where leptin/VEGFR/Notch crosstalk could play an important role in cancer growth, and could be a new target for the control of tumor angiogenesis.     

Bi-directional cell contact-dependent regulation of gene expression between endothelial cells and osteoblasts in a three-dimensional spheroidal coculture model

Multiple cell-cell interactions control bone morphogenesis and vascularization. We have employed a spheroidal coculture system of endothelial cells (EC) and osteoblasts (OB) to study cell contact-dependent gene regulation between these two cell types that may play a role in regulating OB differentiation and EC angiogenic properties. Coculture spheroids differentiate spontaneously to organize into a core of OB and a surface layer of endothelial cells. Individual spheroid culture of EC or OB leads to significant alterations in gene expression compared to standard monolayer culture (upregulation of Tie-2 in EC; upregulation of angiopoietin-2 in osteoblasts). More importantly, spheroidal coculture of endothelial cells and osteoblasts leads to significant changes of gene expression in both cell populations (upregulation of VEGFR-2 in EC; downregulation of VEGF, and upregulation of alkaline phosphatase in osteoblasts). These changes are dependent on cell-cell contact and are not seen in stimulation experiments with conditioned supernatants. Collectively, the data demonstrate complex bi-directional gene regulation mechanisms between EC and OB that are likely to play a critical role during OB differentiation and in controlling the properties of angiogenic EC.     

Inhibition of endothelial cell proliferation by targeting Rac1 GTPase with small interference RNA in tumor cells

Hypoxia-induced angiogenesis plays an important role in the malignancy of solid tumors. A number of recent studies including our own have suggested that Rho family small GTPases are involved in this process, and Racl, a prominent member of the Rho family, may be critical in regulating hypoxia-induced gene activation of several angiogenesis factors and tumor suppressors. To fur-ther define Racl function in angiogenesis and to explore novel approaches to modulate angiogenesis, we employed the small interference RNA technique to knock down gene expression of Racl in gastric cancer cell line AGS that expresses a high level of Racl.Both the mRNA and protein levels of Racl in the AGS cells were decreased dramatically after transfection with a Racl-specific siRNA vector. When the conditioned medium derived from the Racl downregulated AGS cells was applied to the human endothelial cells. it could significantly inhibit the cell proliferation. Further study proved that, VEGF and HIF-la, two angiogenesis promoting factors, were found to be downregulated whereas p53 and VHL, which are tumor suppressors and angiogenesis inhibitors. were upregulated in the Racl siRNA transfected cells. Our results suggest that Racl may be involved in angiogenesis by controlling the expression of angiogenesis-related factors and provide a possible strategy for the treatment of tumor angiogenesis by targeting the Racl GTPase.     

Heat shock proteins and other components of cellular machinery for protein synthesis are up-regulated in vascular endothelial cell growth factor-activated human endothelial cells

Proteome analysis of human umbilical endothelial cells was performed to identify proteins that are modified during vascular endothelial cell growth factor (VEGF)-induced transition from the quiescent into the proliferating-migrative phenotype. Subtractive analysis of two-dimensional gel patterns of human endothelial cells, before and after stimulation with VEGF(165), revealed differences in 85 protein spots. All proteins were identified by peptide sequencing and peptide mass fingerprinting using an electrospray spectrometer. The proteins identified were members of specific families including Ca(2+)-binding proteins, fatty-acid binding proteins, structural proteins, and chaperones. Remarkably, there was a massive activation of cellular machinery for both protein synthesis and protein degradation. Thus, among up-regulated proteins there were members of all groups of heat shock proteins (HSPs; HSP 27, HSP 60, HSP 70p5, HSP 70p8, HSP 90, and HSP 96) and some other proteins showing either chaperone activity or which participate in assembly of multimolecular structures (TCP-1, desmoplakins, junction plakoglobin, GRP 94, thioredoxin related protein, and peptidylprolyl isomerase). The increased expression of HSPs was confirmed at the mRNA level at different stages of treatment with VEGF. Similarly, components of the proteolytic machinery for the degradation of misfolded proteins (ER-60, cathepsin D, proteasome subunits, and protease inhibitor 6) were also up-regulated. On the other hand, changes in the expression of structural proteins (T-plastin, vimentin, alpha tubulin, actin, and myosin) could account, at least in part, for the different morphologies displayed by migrating endothelial cells. In summary, our data show that VEGF levels similar to those during physiological stresses induce a number of genes and multiple endogenous pathways seem to be engaged in restoring cellular homeostasis. To ensure cell survival, the molecular chaperones (the heat shock family of stress proteins) are highly up-regulated providing protein-folding machinery to repair or degrade misfolded proteins.     

PRKX critically regulates endothelial cell proliferation, migration, and vascular-like structure formation

Angiogenesis is a fundamental step in several important physiological events and pathological conditions including embryonic development, wound repair, tumor growth and metastasis. PRKX was identified as a novel type-I cAMP-dependent protein kinase gene expressed in multiple developing tissues. PRKX has also been shown to be phylogenetically and functionally distinct from PKA. This study presents the first evidence that PRKX stimulates endothelial cell proliferation, migration, and vascular-like structure formation, which are the three essential processes for angiogenesis. In contrast, classic PKA demonstrated an inhibitory effect on endothelia vascular-like structure formation. Our findings suggest that PRKX is an important protein kinase engaged in the regulation of angiogenesis and could play critical roles in various physiological and pathological conditions involving angiogenesis. PRKX binds to Pin-1, Magi-1 and Bag-3, which regulate cell proliferation, apoptosis, differentiation and tumorigenesis. The interaction of PRKX with Pin-1, Magi-1 and Bag-3 could contribute to the stimulating role of PRKX in angiogenesis.     

细胞生长因子对冠状动脉内皮细胞增殖与迁移的影响

目的 :观察肝细胞生长因子 (HGF)和血管内皮细胞生长因子 (VEGF)对体外培养牛冠状动脉内皮细胞(BCAEC)增殖、迁移的影响。方法 :分离和培养BCAEC ,设对照组、VEGF组、HGF组。采用四甲基偶氮唑蓝法(MTT)观察细胞增殖 ;倒置显微镜观察培养的血管内皮细胞的迁移。结果 :对照组、VEGF组、HGF组的OD值分别为 0 .2 2± 0 .0 1、0 .40± 0 .1 4、0 .44± 0 .1 5 ;VEGF组、HGF组BCAEC的增殖率分别为 81 .8%± 1 6 .9%、1 0 0 %±2 1 .1 % ;对照组BCAEC迁移不明显 ,而VEGF组和HGF组BCAEC迁移明显。结论 :VEGF、HGF能促进BCAEC增殖、迁移 ,HGF作用强度不亚于VEGF。     

Short- and long-term effects of silver nanoparticles on human microvascular endothelial cells

AIM: To study the response to silver nanoparticles (Ag NP) of human microvascular endothelial cells, protagonists of angiogenesis.METHODS: We cultured human microvascular endothelial cells and endothelial colony-forming cells in their corresponding growth medium. Stock solutions of Ag NP were prepared in culture medium and sonicated before use. They were added at different concentrations and for different times to culture media. The toxicity of Ag NP was investigated by measuring the reduction of yellow tetrazolium salt to dark purple formazan (MTT assay) at 575 nm. After staining with trypan blue, cell proliferation was assessed by counting viable cells. The lactate dehydrogenase leakage assay was performed on culture media by following the oxidation of NADH to NAD+ and monitoring the reaction kinetically at 340 nm. Reactive oxygen species production was quantified using 2’-7’-dichlorofluorescein diacetate. The alkaline comet assay was performed after mixing the cells with low melting-point agarose. Electrophoresis was then conducted and the samples were stained with ethidium bromide and analyzed with a fluorescence microscope.RESULTS: Ag NP are cytotoxic in a dose and time dependent fashion for HMEC. At high concentrations, Ag NP determine loss of membrane integrity as demonstrated by the increased activity of lactate dehydrogenase in the culture medium. Ag NP rapidly stimulate the formation of free radicals. However, pre-incubation with Trolox, apocynin, or N-acetyl-L-cysteine, antioxidants which have different structure and act through different mechanisms, is not sufficient to prevent cytotoxicity. Ag NP also induce DNA damage dose-dependently, as shown by comet assay. When exposed to sublethal concentrations of Ag NP for long times, the cells remain viable but are growth retarded. Interestingly, removal of Ag NP partially rescues cell growth. Also genotoxicity is reversible upon removal of Ag NP from culture medium, suggesting that no permanent modifications occur. It is noteworthy that Ag NP are cytotoxic and genotoxic also for endothelial progenitors, in particular for endothelial colony-forming cells, which participate to angiogenesis.CONCLUSION: Silver nanoparticles are cytotoxic and genotoxic for human microvascular endothelial cells and might become a useful tool to control excessive angiogenesis.     

Arterial-venous endothelial cell fate is related to vascular endothelial growth factor and Notch status during human bone mesenchymal stem cell differentiation

Human bone mesenchymal stem cells (hMSCs) can differentiate into endothelial cells (ECs), so we aimed to investigate whether hMSCs could also differentiate into a specific arterial or venous ECs. hMSCs were induced to differentiate into ECs using vascular endothelial growth factor (VEGF). Low VEGF concentration (50ng/ml) upregulated the venous marker gene EphB4, however high concentration (100ng/ml) upregulated the arterial marker genes ephrinB2, Dll4 and Notch4, and downregulated the venous marker genes EphB4 and COUP-TFll. This VEGF dose-dependent induction was largely blocked by inhibition of the Notch pathway in hMSCs treated with gamma-secretase inhibitor. Therefore, differentiation of hMSCs into arterial- or venous-specific ECs depends on VEGF and is regulated by the Notch pathway.     

Morphological differences between guinea pig aortic and venous endothelial cells in situ

Endothelial cells (ECs) respond to fluid shear stress. They reveal shear stress related morphological changes in both their cell shape and cytoskeletal organization. Little is known about the cytoskeletal organization of ECs in situ. We studied, together with the living ultrasound high resolution imaging system, the distribution of stress fibers (SFs), certain focal adhesion (FA) and signal transduction associated proteins in guinea pig aortic and venous ECs. Although SFs present in the basal portion of venous ECs ran along the direction of the blood flow, their size was smaller and their number was fewer than those of aortic ECs. Venous ECs were elongated to the direction of flow than in aortic ECs exposed over normal shear stress (SS). Since fluid SS in the vein is low, a sustained and uni-directional low SS over a long period might thus cause these structural features observed in venous ECs.     

Role of specific microRNAs for endothelial function and angiogenesis

Accumulating evidence indicates that various aspects of angiogenesis, such as proliferation, migration, and morphogenesis of endothelial cells, can be regulated by specific miRNAs in an endothelial-specific manner. As novel molecular targets, miRNAs have a potential value for treatment of angiogenesis-associated diseases such as cancers, inflammation, and vascular diseases. In this article, we review the latest advances in the identification and validation of angiogenesis-regulatory miRNAs and their targets, and discuss their roles and mechanisms in regulating endothelial cell function and angiogenesis.