An affordable method to obtain cultured endothelial cells from peripheral blood

The culture of endothelial progenitor cells (EPC) provides an excellent tool to research on EPC biology and vascular regeneration and vasculogenesis. The use of different protocols to obtain EPC cultures makes it difficult to obtain comparable results in different groups. This work offers a systematic comparison of the main variables of most commonly used protocols for EPC isolation, culture and functional evaluation. Peripheral blood samples from healthy individuals were recovered and mononuclear cells were cultured. Different recovery and culture conditions were tested: blood volume, blood anticoagulant, coating matrix and percentage of foetal bovine serum (FBS) in culture media. The success of culture procedure, first colonies of endothelial cells appearance time, correlation with number of circulating EPC (cEPC) and functional comparison with human umbilical vein endothelial cells (HUVEC) were studied. The use of heparin, a minimum blood volume of 30 ml, fibronectin as a coating matrix and endothelial growing media‐2 supplemented with 20% FBS increased the success of obtaining EPC cultures up to 80% of the processed samples while reducing EPC colony appearance mean time to a minimum of 13 days. Blood samples exhibiting higher cEPC numbers resulted in reduced EPC colony appearance mean time. Cells isolated by using this combination were endothelial cell‐like EPCs morphological and phenotypically. Functionally, cultured EPC showed decreased growing and vasculogenic capacity when compared to HUVEC. Thus, above‐mentioned conditions allow the isolation and culture of EPC with smaller blood volumes and shorter times than currently used protocols.     

Breakdown of the endothelial barrier function in tumor cell transmigration

The ability of tumor cells to metastasize is associated with a poor prognosis for cancer. During the process of metastasis, tumor cells circulating in the blood or lymph vessels can adhere to, and potentially transmigrate through, the endothelium and invade the connective tissue. We studied the effectiveness of the endothelium as a barrier against the invasion of 51 tumor cell lines into a three-dimensional collagen matrix. Only nine tumor cell lines showed attenuated invasion in the presence of an endothelial cell monolayer, whereas 17 cell lines became invasive or showed a significantly increased invasion. Endothelial cells cocultured with invasive tumor cells increased chemokine gene expression of IL-8 and Gro-β. Expression of the IL-8 and Gro-β receptor, CXCR2, was upregulated in invasive tumor cells. Addition of IL-8 or Gro-β increased tumor cell invasiveness by more than twofold. Tumor cell variants selected for high CXCR2 expression were fourfold more invasive in the presence of an endothelial cell layer, whereas CXCR2 siRNA knock-down cells were fivefold less invasive. We demonstrate that Gro-β and IL-8 secreted by endothelial cells, together with CXCR2 receptor expression on invasive tumor cells, contribute to the breakdown of the endothelial barrier by enhancing tumor cell force generation and cytoskeletal remodeling dynamics.     

内皮祖细胞对急性肺损伤保护作用的研究进展

内皮祖细胞（EPC）是一种多潜能细胞,主要来源于骨髓。外周血EPC可以参与修复多种血管内皮细胞损伤的疾病。目前研究证实EPC通过动员、迁移、归巢和分化等步骤在受损的肺组织处参与内皮细胞修复,调节失控的炎症反应,增强抗氧化能力,对修复和维持肺泡毛细血管屏障的完整性起着重要作用。EPC在心血管疾病和组织工程领域应用研究的成功,为EPC在急性肺损伤的治疗提供了新的思路。     

Coupling of endothelial injury and repair: an analysis using an in vivo experimental model

The repair of the endothelium after inflammatory injury is essential to maintaining homeostasis. The link between inflammation-induced endothelial damage and repair has not been fully characterized in vivo. We have developed a rat model to evaluate the coupling of lipopolysaccharide (LPS)-induced endothelial injury and repair. Aortic endothelium injury was analyzed by both inmunohistochemistry and flow cytometry to quantify the number of endothelial cells and the percentage of apoptotic endothelial cells. We have also identified the percentage of circulating angiogenic cells capable of repairing the damaged endothelium. Erythropoietin was administered to inhibit LPS-induced endothelial apoptosis. Loss of the normal endothelial structure was observed in the aorta of the animals treated with LPS. Eight hours after LPS administration, the number of endothelial cells decreased by 40%, returning to normal after 24 h. There was a threefold increase in the percentage of circulating angiogenic cells, which did not return to normal levels until 48 h after LPS administration. Circulating angiogenic cell levels did not change when LPS-induced endothelial damage was prevented by erythropoietin. The endothelial injury caused by inflammation activates the mobilization of circulating angiogenic cells, thus completing endothelial repair. Inflammation without endothelial injury does not trigger the mobilization of circulating angiogenic cells.     

Low-dose aspirin promotes endothelial progenitor cell migration and adhesion and prevents senescence

Circulating endothelial progenitor cells (EPCs) play a key role in restoring endothelial function and enhancing angiogenesis. However, the effects of low-dose aspirin on circulating EPCs are not well known. We investigated the effects of low-dose aspirin on EPC migration, adhesion, senescence, proliferation, apoptosis and endothelial nitric oxide synthase (eNOS) expression. EPC migration was detected by a modified Boyden chamber assay. EPC adhesion assay was performed by counting adherent cells on fibronectin-coated culture dishes. EPC senescence was assessed by both senescence-associated-beta-galactosidase staining and DAPI staining. EPC proliferation was analyzed by MTT assay. EPC apoptosis was evaluated by flow cytometric analysis. eNOS protein expression was measured by Western blotting analysis. Aspirin promoted EPC migratory and adhesive capacity at concentrations between 0.1 and 100micromol/L and prevented senescence at concentrations between 50 and 100micromol/L. Meanwhile, aspirin in a range of these concentrations did not affect EPC proliferation, apoptosis or eNOS expression. Our findings indicate that low-dose aspirin promotes migration and adhesion and delays the onset of senescence of EPCs.     

Angiopoietin-2 stimulates migration of endothelial progenitors and their interaction with endothelium

The factors controlling recruitment of endogenous and transplanted endothelial progenitor cells (EPC) to areas of neovascularization are largely unknown. In this study, we have examined the possibility that EPC migration and adhesion could be regulated by angiopoietin-2 (Ang2), a soluble ligand expressed by endothelial cells at sites of vessel remodelling and angiogenesis. We show for the first time that Ang2 causes a marked stimulation of EPC migration. This was specific for EPC as the ligand failed to affect endothelial cell migration. Ang2-stimulated EPC migration was inhibited by soluble Tie2 ectodomain. Furthermore, the ligand stimulated adhesion between EPC and endothelial monolayers.     

The distribution of centrosomes in migrating endothelial cells during wound healing in situ.

We have examined the distribution of centrioles in rabbit thoracic aortic endothelial cells induced to migrate by wounding the endothelium in situ. Following denudation of the endothelium from a segment of the aorta with a balloon catheter, a wound edge was created from which endothelial cells began to migrate onto the denuded surface. In this in situ model of cell migration, the position of centrioles was determined in cells along the wound edge by immunofluorescence and antibodies which specifically label these cell organelles, and then they were classified in relation to the nucleus and the direction of cell migration as being oriented toward the wound, in the center, or away from wound. At time 0, as in normal unwounded adult rabbit aorta, no preferential orientation of centrioles was evident. Within 12 h after wounding, the centrioles in about 53% of endothelial cells near the wound edge were oriented toward the wound, while in less than 20% of the cells they were oriented away from wound. At 24 h, in cells up to 800 microns from the wound edge, centrioles in only about 10% of the endothelial cells were oriented away from wound, while in about 52% of cells they were found in the center and in 38% of the cells they remained oriented toward the wound. At 48 h, up to 2000 microns from the wound edge, the majority of endothelial cells had their centrioles in the center, possibly as a result of an increase in mitotic index as cells replicate to reestablish an intact endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)     

PKA and Epac1 regulate endothelial integrity and migration through parallel and independent pathways

The vascular endothelium provides a semi-permeable barrier, which restricts the passage of fluid, macromolecules and cells to the surrounding tissues. Cyclic AMP promotes endothelial barrier function and protects the endothelium against pro-inflammatory mediators. This study analyzed the relative contribution of two cAMP targets, PKA and Epac1, to the control of endothelial barrier function and endothelial cell migration. Real-time recording of transendothelial electrical resistance showed that activation of either PKA or Epac1 with specific cAMP analogues increases endothelial barrier function and promotes endothelial cell migration. In addition, reduction of Epac1 expression showed that Epac1 and PKA control endothelial integrity and cell motility by two independent and complementary signaling pathways. We demonstrate that integrin-mediated adhesion is required for PKA, but not Epac1-Rap1-driven stimulation of endothelial barrier function. In contrast, both PKA- and Epac1-stimulated endothelial cell migration requires integrin function. These data show that activation of Epac1 and PKA by cAMP results in the stimulation of two parallel, independent signaling pathways that positively regulate endothelial integrity and cell migration, which is important for recovery after endothelial damage and for restoration of compromised endothelial barrier function.     

Cancer cells regulate biomechanical properties of human microvascular endothelial cells

Metastasis is a key event of malignant tumor progression. The capability to metastasize depends on the ability of the cancer cell to migrate into connective tissue, adhere, and possibly transmigrate through the endothelium. Previously we reported that the endothelium does not generally act as barrier for cancer cells to migrate in three-dimensional extracellular matrices (3D-ECMs). Instead, the endothelium acts as an enhancer or a promoter for the invasiveness of certain cancer cells. How invasive cancer cells diminish the endothelial barrier function still remains elusive. Therefore, this study investigates whether invasive cancer cells can decrease the endothelial barrier function through alterations of endothelial biomechanical properties. To address this, MDA-MB-231 breast cancer cells were used that invade deeper and more numerous into 3D-ECMs when co-cultured with microvascular endothelial cells. Using magnetic tweezer measurements, MDA-MB-231 cells were found to alter the mechanical properties of endothelial cells by reducing endothelial cell stiffness. Using spontaneous bead diffusion, actin cytoskeletal remodeling dynamics were shown to be increased in endothelial cells co-cultured with MDA-MB-231 cells compared with mono-cultured endothelial cells. In addition, knockdown of the α5 integrin subunit in highly transmigrating α5β1(high) cells derived from breast, bladder, and kidney cancer cells abolished the endothelial invasion-enhancing effect comparable with the inhibition of myosin light chain kinase. These results indicate that the endothelial invasion-enhancing effect is α5β1 integrin-dependent. Moreover, inhibition of Rac-1, Rho kinase, MEK kinase, and PI3K reduced the endothelial invasion-enhancing effect, indicating that signaling via small GTPases may play a role in the endothelial facilitated increased invasiveness of cancer cells. In conclusion, decreased stiffness and increased cytoskeletal remodeling dynamics of endothelial cells may account for the breakdown of endothelial barrier function, suggesting that biomechanical alterations are sufficient to facilitate the transmigration and invasion of invasive cancer cells into 3D-ECMs.     

Distribution of a 69-kD laminin-binding protein in aortic and microvascular endothelial cells: modulation during cell attachment, spreading, and migration

Affinity chromatography and immunolocalization techniques were used to investigate the mechanism(s) by which endothelial cells interact with the basement membrane component laminin. Bovine aortic endothelial cells (BAEC) membranes were solubilized and incubated with a laminin-Sepharose affinity column. SDS-PAGE analysis of the eluted proteins identified a 69-kD band as the major binding protein, along with minor components migrating at 125, 110, 92, 85, 75, 55, and 30 kD. Polyclonal antibodies directed against a peptide sequence of the 69-kD laminin-binding protein isolated from human tumor cells identified this protein in BAEC lysates. In frozen sections, these polyclonal antibodies and monoclonal antibodies raised against human tumor 69-kD stained the endothelium of bovine aorta and the medial smooth muscle cells, but not surrounding connective tissue or elastin fibers. When nonpermeabilized BAEC were stained in an in vitro migration assay, there appeared to be apical patches of 69 kD staining in stationary cells. However, when released from contact inhibition, 69 kD was localized to ruffling membranes on cells at the migrating front. Permeabilized BAEC stained for 69 kD diffusely, with a granular perinuclear distribution and in linear arrays throughout the cell. During migration a redistribution from diffuse to predominanately linear arrays that co-distributed with actin microfilaments was noted in double-label experiments. The 69-kD laminin-binding protein colocalized with actin filaments in permeabilized cultured microvascular endothelial cells in a continuous staining pattern at 6 h postplating which redistributed to punctate patches along the length of the filaments at confluence (96 h). In addition, 69 kD co-distribution with laminin could also be demonstrated in cultured subconfluent cells actively synthesizing matrix. Endothelial cells express a 69-kD laminin-binding protein that is membrane associated and appears to colocalize with actin microfilaments. The topological distribution of 69 kD and its cytoskeletal associations can be modulated by the cell during cell migration and growth suggesting that 69 kD may be a candidate for a membrane protein involved in signal transduction from extracellular matrix to cell via cytoskeletal connections.     

Inhibition of Lp(a)-induced functional impairment of endothelial cells and endothelial progenitor cells by hepatocyte growth factor

BackgroundLipoprotein (a) (Lp(a)) is one of the risk factors for peripheral artery disease (PAD). Our previous report demonstrated that hepatocyte growth factor (HGF) gene therapy attenuated the impairment of collateral formation in Lp(a) transgenic mice. Since risk factors for atherosclerosis accelerate endothelial senescence and impair angiogenesis, we examined the role of Lp(a) in dysfunction and senescence of endothelial progenitor cells (EPC) and endothelial cells.MethodsIn vitro and in vivo incorporation assays were performed using ex-vivo expanded DiI-labeled human EPC. Senescence of cultured endothelial cells, production of oxidative stress and angiogenesis function were evaluated by SA-β-galactosidase staining, dihydroethidium (DHE) staining and Matrigel assay, respectively.ResultsEPC transplantation significantly stimulated recovery of ischemic limb perfusion, while EPC pre-treated with Lp(a) did not increase ischemic limb perfusion. Impairment of angiogenesis by EPC with Lp(a) was associated with a significant decrease in CD31-positive capillaries and DiI-labeled EPC. Importantly, Lp(a) significantly accelerated the onset of senescence and production of reactive oxygen species (ROS) in human aortic endothelial cells, accompanied by a significant increase in the protein expression of p53 and p21. On the other hand, HGF significantly attenuated EPC dysfunction, senescence, ROS production, and p53 and p21 expression induced by Lp(a).ConclusionLp(a) might affect atherosclerosis via acceleration of senescence, ROS production, and functional impairment of the endothelial cell lineage. HGF might have inhibitory effects on these atherogenic actions of Lp(a).     

Ultrastructural identification and distribution of the adhesion molecules ICAM-1 and LFA-1 in the vascular and extravascular compartments of the human palatine tonsil

Summary Immunohistological analysis of sections prepared from human palatine tonsils revealed marked differences in the distribution of the adhesion molecule, leucocyte function antigen-1 (LFA-1) and its counter receptor, intercellular adhesion molecule-1 (ICAM-1). Light microscopy showed that LFA-1 was restricted to the leucocytes, particularly the lymphocytes. In contrast, staining of ICAM-1 was predominantly confined to the vascular endothelium with the greatest expression seen on the morphologically distinct high endothelial venules in the parafollicular areas; these are the sites that appear to support lymphocyte migration. Electron microscopy revealed that ICAM-1 was present on the luminal and lateral surfaces of the high endothelium and absent from the abluminal surface supported by basal lamina. The ICAM-1 was also absent from those surfaces of the endothelium that were in close contact with intravascular lymphocytes. Other cells stained by the anti-ICM-1 antibody included dendritic cells, plasma cells and epithelial cells in the reticulated crypt epithelium and in the upper strata of the non-keratinised stratified squamous epithelium. The high expression of LFA-1 was most prominent on lymphocytes, low on antigen-presenting cells and activated lymphoid cells, and not detectable on plasma cells, epithelial and endothelial cells. We propose that LFA-1/ICAM-1 binding participates in mediating the transendothelial migration of lymphocytes across the high endothelial venules of palatine tonsil.     

Brain endothelial cells and the glio-vascular complex

We present and discuss the role of endothelial and astroglial cells in managing the blood-brain barrier (BBB) and aspects of pathological alterations in the BBB. The impact of astrocytes, pericytes, and perivascular cells on the induction and maintenance of the gliovascular unit is largely unidentified so far. An understanding of the signaling pathways that lie between these cell types and the endothelium and that possibly are mediated by components of the basal lamina is just beginning to emerge. The metabolism for the maintenance of the endothelial barrier is intimately linked to and dependent on the microenvironment of the brain parenchyma. We report the structure and function of the endothelial cells of brain capillaries by describing structures involved in the regulation of permeability, including transporter systems, caveolae, and tight junctions. There is increasing evidence that caveolae are not only vehicles for endo- and transcytosis, but also important regulators of tight-junction-based permeability. Tight junctions separate the luminal from the abluminal membrane domains of the endothelial cell (“fence function”) and control the paracellular pathway (“gate function”) thus representing the most significant structure of the BBB. In addition, the extracellular matrix between astrocytes/pericytes and endothelial cells contains numerous molecules with inherent signaling properties that have to be considered if we are to improve our knowledge of the complex and closely regulated BBB. Any work of our own cited in this review was supported by grants from the Deutsche Krebshilfe (to H.W.), the Deutsche Forschungsgemeinschaft (to H.W.), and the Hertie-Foundation (to H.W. and to Britta Engelhardt, Bern, Switzerland).     

High-density lipoprotein exerts vasculoprotection via endothelial progenitor cells

Endothelial progenitor cells (EPC) enhance endothelial cell repair, improve endothelial dysfunction and are a predictor for cardiovascular mortality. High-density lipoprotein (HDL) cholesterol levels inversely correlate with cardiovascular events and have vasculoprotective effects. Here we postulate that HDL influences EPC biology. HDL and EPC were isolated according to standard procedures. Differentiation of mononuclear cells into DiLDL/lectin positive cells was enhanced after HDL treatment compared to vehicle. HDL was able to inhibit apoptosis (TUNEL assay, annexin V staining) while proliferation (BrdU incorporation) of early outgrowth colonies after extended cell cultivation (14 days) was increased. Flow chamber experiments revealed an improved adhesion of HDL pre-incubated EPC on human coronary artery endothelial cells (HCAEC) compared to vehicle while HDL treatment of HCAEC prevented adhesion of inflammatory cells. Flow cytometry demonstrated an up-regulation of beta2- and alpha4-integrins on HDL pre-incubated EPC. Blocking experiments revealed a unique role of beta2-integrin in EPC adhesion. Treatment of wild-type mice with recombinant HDL after endothelial denudation resulted in enhanced re-endothelialization compared to vehicle. Finally, in patients with coronary artery disease a correlation between circulating EPC and HDL concentrations was demonstrated. We provide evidence that HDL mediates important vasculoprotective action via the improvement of function of circulating EPC.     

Circulating endothelial cells, microparticles and progenitors: key players towards the definition of vascular competence

The balance between lesion and regeneration of the endothelium is critical for the maintenance of vessel integrity. Exposure to cardiovascular risk factors (CRF) alters the regulatory functions of the endothelium that progresses from a quiescent state to activation, apoptosis and death. In the last 10 years, identification of circulating endothelial cells (CEC) and endothelial-derived microparticles (EMP) in the circulation has raised considerable interest as non-invasive markers of vascular dysfunction. Indeed, these endothelial-derived biomarkers were associated with most of the CRFs, were indicative of a poor clinical outcome in atherothrombotic disorders and correlated with established parameters of endothelial dysfunction. CEC and EMP also behave as potential pathogenic vectors able to accelerate endothelial dysfunction and promote disease progression. The endothelial response to injury has been enlarged by the discovery of a powerful physiological repair process based on the recruitment of circulating endothelial progenitor cells (EPC) from the bone marrow. Recent studies indicate that reduction of EPC number and function by CRF plays a critical role in the progression of cardiovascular diseases. This EPC-mediated repair to injury response can be integrated into a clinical endothelial phenotype defining the 'vascular competence' of each individual. In the future, provided that standardization of available methodologies could be achieved, multimarker strategies combining CEC, EMP and EPC levels as integrative markers of 'vascular competence' may offer new perspectives to assess vascular risk and to monitor treatment efficacy.     

内皮细胞间连接的研究进展

内皮细胞形成了大分子物质和循环细胞从知液到细胞的最主要屏障,内皮细胞的通航性主要是通过内皮细胞间连接进行调控的,本文从内容细胞间连接的几种方式,信号的传导,连接变化的调控,篾这中液体的流动及中性粒细胞渗出对内皮细胞间连接的影响进行阐述,讨论了目前内皮细胞间连接的研究进展,提出内皮细胞间连接和骨架结构对血管通透性的调控,中性粒细胞的渗出和血管内皮细胞间连接的重建都具有非常重要的作用,其中内皮细胞的渗     

Dose-dependent effect of nocodazole on endothelial cell cytoskeleton

The endothelium lining the inner surface of blood vessels fulfils an important barrier function and specifically, it controls vascular membrane permeability as well as nutrient and metabolite exchange in circulating blood and tissue fluids. Disturbances in vascular endothelium barrier function (vascular endothelium dysfunction) are coupled to cytoskeleton rearrangements, actomyosin contractility, and as a consequence, formation of paracellular gaps between endothelial cells. Microtubules constitute the first effector link in the reaction cascade resulting in vascular endothelium dysfunction. Increased vascular permeability associated with many human diseases is also manifested as a side effect in anticancer mitosis-blocking therapy. The aim of this study was to examine the possibility of preventing side effects of mitostatic drugs in patients with vascular endothelium dysfunction and to establish effective doses able to disrupt the microtubular network without interfering with the endothelial barrier function. Previously, it was found that the population of endothelial cell microtubules is heterogeneous. Along with dynamic microtubules, cell cytoplasm contains a certain amount of post-translationally modified microtubules that are less active and less susceptible to external influences than dynamic microtubules. We have shown that the area occupied with stable microtubules is relatively large (approx. one third of the total cell area). We assume that it can account for a higher resistance of the endothelial monolayer to factors responsible for vascular endothelium dysfunction. This hypothesis was validated in this study, in which nocodazole was used to induce vascular endothelium dysfunction in lung endothelial cells. The effect of nocodazole on endothelial cell cytoskeleton was found to be dose-dependent. Nocodazole in micromolar concentrations not only irreversibly changed the barrier function, but also upset the viability of endothelial cells and induced their death. Nanomolar concentrations of nocodazole also increased the permeability of the endothelial monolayer; this effect was reversible at the drug concentration ranging from 100 to 200 nM. At 100 nM, nocodazole induced partial disruption of the microtubule network near the cell margin without any appreciable effect on acetylated microtubules and actin filaments. At 200 nM, nocodazole exerted a pronounced effect on the system of dynamic (but not acetylated) microtubules and increased the population of actin filaments in the central region of the cell. Our data suggest that disruption of peripheral microtubules triggers a cascade of reactions culminating in endothelial barrier dysfunction; however, the existence of a large population of microtubules resistant to nanomolar concentrations of the drug provides higher viability of endothelial cells and restores their functional activity.     

Effect of Lumican on the Migration of Human Mesenchymal Stem Cells and Endothelial Progenitor Cells: Involvement of Matrix Metalloproteinase-14

Background

Increasing number of evidence shows that soluble factors and extracellular matrix (ECM) components provide an optimal microenvironment controlling human bone marrow mesenchymal stem cell (MSC) functions. Successful in vivo administration of stem cells lies in their ability to migrate through ECM barriers and to differentiate along tissue-specific lineages, including endothelium. Lumican, a protein of the small leucine-rich proteoglycan (SLRP) family, was shown to impede cell migration and angiogenesis. The aim of the present study was to analyze the role of lumican in the control of MSC migration and transition to functional endothelial progenitor cell (EPC).

Methodology/Principal Findings

Lumican inhibited tube-like structures formation on Matrigel® by MSC, but not EPC. Since matrix metalloproteinases (MMPs), in particular MMP-14, play an important role in remodelling of ECM and enhancing cell migration, their expression and activity were investigated in the cells grown on different ECM substrata. Lumican down-regulated the MMP-14 expression and activity in MSC, but not in EPC. Lumican inhibited MSC, but not EPC migration and invasion. The inhibition of MSC migration and invasion by lumican was reversed by MMP-14 overexpression.

Conclusion/Significance

Altogether, our results suggest that lumican inhibits MSC tube-like structure formation and migration via mechanisms that involve a decrease of MMP-14 expression and activity.     

Paracellular and transcellular migration of metastatic cells through the cerebral endothelium

Breast cancer and melanoma are among the most frequent cancer types leading to brain metastases. Despite the unquestionable clinical significance, important aspects of the development of secondary tumours of the central nervous system are largely uncharacterized, including extravasation of metastatic cells through the blood‐brain barrier. By using transmission electron microscopy, here we followed interactions of cancer cells and brain endothelial cells during the adhesion, intercalation/incorporation and transendothelial migration steps. We observed that brain endothelial cells were actively involved in the initial phases of the extravasation by extending filopodia‐like membrane protrusions towards the tumour cells. Melanoma cells tended to intercalate between endothelial cells and to transmigrate by utilizing the paracellular route. On the other hand, breast cancer cells were frequently incorporated into the endothelium and were able to migrate through the transcellular way from the apical to the basolateral side of brain endothelial cells. When co‐culturing melanoma cells with cerebral endothelial cells, we observed N‐cadherin enrichment at melanoma‐melanoma and melanoma‐endothelial cell borders. However, for breast cancer cells N‐cadherin proved to be dispensable for the transendothelial migration both in vitro and in vivo. Our results indicate that breast cancer cells are more effective in the transcellular type of migration than melanoma cells.     

Decreased circulating endothelial progenitor cell levels and function in patients with nonalcoholic fatty liver disease

Objectives

Nonalcoholic fatty liver disease (NAFLD) is associated with advanced atherosclerosis and a higher risk of cardiovascular disease. Increasing evidence suggests that injured endothelial monolayer is regenerated by circulating bone marrow derived-endothelial progenitor cells (EPCs), and levels of circulating EPCs reflect vascular repair capacity. However, the relation between NAFLD and EPC remains unclear. Here, we tested the hypothesis that patients with nonalcoholic fatty liver disease (NAFLD) might have decreased endothelial progenitor cell (EPC) levels and attenuated EPC function.

Methods and Results

A total of 312 consecutive patients undergoing elective coronary angiography because of suspected coronary artery disease were screened and received examinations of abdominal ultrasonography between July 2009 and November 2010. Finally, 34 patients with an ultrasonographic diagnosis of NAFLD, and 68 age- and sex-matched controls without NAFLD were enrolled. Flow cytometry with quantification of EPC markers (defined as CD34⁺, CD34⁺KDR⁺, and CD34⁺KDR⁺CD133⁺) in peripheral blood samples was used to assess circulating EPC numbers. The adhesive function, and migration, and tube formation capacities of EPCs were also determined in NAFLD patients and controls. Patients with NAFLD had a significantly higher incidence of metabolic syndrome, previous myocardial infarction, hyperuricemia, and higher waist circumference, body mass index, fasting glucose and triglyceride levels. In addition, patients with NAFLD had significantly decreased circulating EPC levels (all P<0.05), attenuated EPC functions, and enhanced systemic inflammation compared to controls. Multivariate logistic regression analysis showed that circulating EPC level (CD34⁺KDR⁺ [cells/10⁵ events]) was an independent reverse predictor of NAFLD (Odds ratio: 0.78; 95% confidence interval: 0.69–0.89, P<0.001).

Conclusions

NAFLD patients have decreased circulating EPC numbers and functions than those without NAFLD, which may be one of the mechanisms to explain atherosclerotic disease progression and enhanced cardiovascular risk in patients with NAFLD.