Hybrid M-mode-like OCT imaging of three-dimensional microvasculature in vivo using reference-free processing of complex valued B-scans

We propose a novel OCT-based method for visualizing microvasculature in three-dimension using reference-free processing of individual complex valued B-scans with highly overlapped A-scans. In the lateral direction of such a B-scan, the amplitude and phase of speckles corresponding to vessel regions exhibit faster variability and, thus, can be detected without comparison with other B-scans recorded in the same plane. This method combines elements of several existing OCT angiographic approaches and exhibits: (1) enhanced robustness with respect to bulk tissue motion with frequencies up to tens of Hz, (2) resolution of microcirculation images equal to that of structural images, and (3) possibility of quantifying the vessels in terms of their decorrelation rates.

[The transfection of lentiviral siRNA vectors targeting ezrin, radixin and moesin facilitates influenza virus replication in primary pulmonary microvascular endothelial cells]

OBJECTIVE

To construct lentivirus siRNA vectors targeting ezrin (E), radixin (R) and moesin (M), transfect rat primary pulmonary microvascular endothelial cells (PMVECs) with the vectors and observe the effects of the transfection on E, R, M gene expressions and influenza virus replication.

METHODS

According to the principles of siRNA synthesis, siRNA sequences targeting E, R and M genes were synthesized and cloned into lentiviral plasmid GV248 to construct lentiviral siRNA vectors Lenti-E-siRNA, Lenti-R-siRNA and Lenti-M-siRNA, respectively. Random Lenti-control-siRNA was also constructed targeting nonsense sequences. Rat PMVECs were cultured by peripheral lung tissue-sticking method. Rat PMVECs were transfected with Lenti-E-siRNA, Lenti-R-siRNA and Lenti-M-siRNA, respectively. The levels of ezrin, radixin and moesin mRNA and proteins were detected by real-time quantitative PCR and Western blotting, the distributions of ERM proteins were detected using confocal laser scanning microscope; After lentivirus-transfected PMVECs were infected with influenza virus, the effects of lentiviral vectors on influenza virus replication were measured by real-time quantitative PCR.

RESULTS

Lenti-E-siRNA, Lenti-R-siRNA, Lenti-M-siRNA and Lenti-control-siRNA were successfully constructed according to sequencing identification of recombinant plasmids. The infection efficacy of lentiviral siRNA vectors in rat PMVECs was above 80% at a multiplicity of infection (MOI) of 10. The transcription and expressions of ezrin, radixin and moesin in rat PMVECs were significantly inhibited by Lenti-E-siRNA, Lenti-R-siRNA, Lenti-M-siRNA respectively. Lentivirus control (containing no target genes) and Lenti-control-siRNA inhibited influenza virus replication in influenza virus-infected PMVECs, while Lenti-E-siRNA, Lenti-R-siRNA and Lenti-M-siRNA increased the levels of influenza virus mRNA in the infected PMVECs.

CONCLUSION

Lentiviral siRNA vectors targeting E, R and M genes were constructed successfully and could inhibit E, R and M gene expressions specifically and effectively. Lentiviral vectors could inhibit influenza virus replication whereas lentiviral siRNA vectors targeting E, R and M facilitated influenza virus replication.

Effect of anti-ApoA-I antibody-coating of stents on neointima formation in a rabbit balloon-injury model

Background and Aims

Since high-density lipoprotein (HDL) has pro-endothelial and anti-thrombotic effects, a HDL recruiting stent may prevent restenosis. In the present study we address the functional characteristics of an apolipoprotein A-I (ApoA-I) antibody coating in vitro. Subsequently, we tested its biological performance applied on stents in vivo in rabbits.

Materials and Methods

The impact of anti ApoA-I- versus apoB-antibody coated stainless steel discs were evaluated in vitro for endothelial cell adhesion, thrombin generation and platelet adhesion. In vivo, response to injury in the iliac artery of New Zealand white rabbits was used as read out comparing apoA-I-coated versus bare metal stents.

Results

ApoA-I antibody coated metal discs showed increased endothelial cell adhesion and proliferation and decreased thrombin generation and platelet adhesion, compared to control discs. In vivo, no difference was observed between ApoA-I and BMS stents in lumen stenosis (23.3±13.8% versus 23.3±11.3%, p=0.77) or intima surface area (0.81±0.62 mm² vs 0.84±0.55 mm², p=0.85). Immunohistochemistry also revealed no differences in cell proliferation, fibrin deposition, inflammation and endothelialization.

Conclusion

ApoA-I antibody coating has potent pro-endothelial and anti-thrombotic effects in vitro, but failed to enhance stent performance in a balloon injury rabbit model in vivo.

The complex mural cell: pericyte function in health and disease

Pericytes are perivascular cells that can be distinguished from vascular smooth muscle cells by their specific morphology and expression of distinct molecular markers. Found in the microvascular beds distributed throughout the body, they are well known for their regulation of a healthy vasculature. In this review, we examine the mechanism of pericyte support to vasomotion, and the known pathways that regulate pericyte response in angiogenesis and neovascular stabilization. We will also discuss the role of pericytes in vascular basement membrane and endothelial barrier function regulation. In contrast, recent findings have indicated that pericyte dysfunction, characterized by changes in pericyte contractility or pericyte loss of microvascular coverage, plays an important role in onset and progression of vascular-related and fibrogenic diseases. From a therapeutic point of view, pericytes have recently been identified as a putative pool of endogenous mesenchymal stem cells that could be activated in response to tissue injury to contribute to the regenerative process on multiple levels. We will discuss the mechanisms via which pericytes are involved in disease onset and development in a number of pathophysiological conditions, as well as present the evidence that supports a role for multipotent pericytes in tissue regeneration. The emerging field of pericyte research will not only contribute to the identification of new drug targets in pericyte dysfunction associated diseases, but may also boost the use of this cell type in future cell-based regenerative strategies.

A mathematical model for understanding fluid flow through engineered tissues containing microvessels

Knowledge is limited about fluid flow in tissues containing engineered microvessels, which can be substantially different in topology than native capillary networks. A need exists for a computational model that allows for flow through tissues dense in nonpercolating and possibly nonperfusable microvessels to be efficiently evaluated. A finite difference (FD) model based on Poiseuille flow through a distribution of straight tubes acting as point sources and sinks, and Darcy flow through the interstitium, was developed to describe fluid flow through a tissue containing engineered microvessels. Accuracy of the FD model was assessed by comparison to a finite element (FE) model for the case of a single tube. Because the case of interest is a tissue with microvessels aligned with the flow, accuracy was also assessed in depth for a corresponding 2D FD model. The potential utility of the 2D FD model was then explored by correlating metrics of flow through the model tissue to microvessel morphometric properties. The results indicate that the model can predict the density of perfused microvessels based on parameters that can be easily measured.

Targeting glycosaminoglycans in the lung by an engineered CXCL8 as a novel therapeutic approach to lung inflammation

It is broadly recognized that chemokine-activated neutrophils play a crucial role in the inflammation and disruption of lung tissue observed in several acute and chronic lung diseases. Since glycosaminoglycan side chains of proteoglycans act as chemokine co-receptors in inflammation, we have used a CXCL8-based dominant-negative mutant, dnCXCL8, to displace neutrophil-related chemokines in murine lungs using models of lung inflammation. Treatment with dnCXCL8 resulted in a dose-dependent reduction of neutrophil counts in bronchoalveolar lavage (BAL) of mice exposed to lipopolysaccharide after intravenous, subcutaneous and intratracheal administration. A strong and significant therapeutic effect was achieved already at a dose of 40 µg/kg of dnCXCL8. A similar dose response, but showing a broader spectrum of reduced inflammatory cells and soluble inflammatory markers, was observed in a murine model of tobacco smoke (TS)-induced lung inflammation. The broad spectrum of reduced inflammatory cells and markers can be due to the strong inhibition of neutrophil extravasation into the lung parenchyma, and/or to a relatively broad protein displacement profile of dnCXCL8 which may compete not only with wtCXCL8 for glycosaminoglycan-binding but possibly also with other related glycosaminoglycan-binding pro-inflammatory chemokines. Overall our results demonstrate that antagonizing CXCL8/glycosaminoglycan binding reduces lung inflammation as well as associated lung tissue damage due to LPS and TS and may therefore be a new therapeutic approach for lung pathologies characterized by a neutrophilic inflammatory phenotype.

Ascorbic acid transport in brain microvascular pericytes

Intracellular vitamin C, or ascorbic acid, has been shown to prevent the apoptosis of cultured vascular pericytes under simulated diabetic conditions. We sought to determine the mechanism by which ascorbate is transported into pericytes prior to exerting this protective effect. Measuring intracellular ascorbate, we found that pericytes display a linear uptake over 30 min and an apparent transport Km of 21 μM, both of which are consistent with activity of the Sodium-dependent Vitamin C Transporter 2 (SVCT2). Uptake of both radiolabeled and unlabeled ascorbate was prevented by inhibiting SVCT2 activity, but not by inhibiting the activity of GLUT-type glucose transporters, which import dehydroascorbate to also generate intracellular ascorbate. Likewise, uptake of dehydroascorbate was prevented with the inhibition of GLUTs, but not by inhibiting the SVCT2, indicating substrate specificity of both transporters. Finally, presence of the SVCT2 in pericytes was confirmed by western blot analysis, and immunocytochemistry was used to localize it to the plasma membrane and intracellular sites. Together, these data clarify previous inconsistencies in the literature, implicate SVCT2 as the pericyte ascorbate transporter, and show that pericytes are capable of concentrating intracellular ascorbate against a gradient in an energy- and sodium-dependent fashion.

RNA-Seq reveals a role for NFAT-signaling in human retinal microvascular endothelial cells treated with TNFα

TNFα has been identified as playing an important role in pathologic complications associated with diabetic retinopathy and retinal inflammation, such as retinal leukostasis. However, the transcriptional effects of TNFα on retinal microvascular endothelial cells and the different signaling pathways involved are not yet fully understood. In the present study, RNA-seq was used to profile the transcriptome of human retinal microvascular endothelial cells (HRMEC) treated for 4 hours with TNFα in the presence or absence of the NFAT-specific inhibitor INCA-6, in order to gain insight into the specific effects of TNFα on RMEC and identify any involvement of NFAT signaling. Differential expression analysis revealed that TNFα treatment significantly upregulated the expression of 579 genes when compared to vehicle-treated controls, and subsequent pathway analysis revealed a TNFα-induced enrichment of transcripts associated with cytokine-cytokine receptor interactions, cell adhesion molecules, and leukocyte transendothelial migration. Differential expression analysis comparing TNFα-treated cells to those co-treated with INCA-6 revealed 10 genes whose expression was significantly reduced by the NFAT inhibitor, including those encoding the proteins VCAM1 and CX3CL1 and cytokines CXCL10 and CXCL11. This study identifies the transcriptional effects of TNFα on HRMEC, highlighting its involvement in multiple pathways that contribute to retinal leukostasis, and identifying a previously unknown role for NFAT-signaling downstream of TNFα.

[Role of RAGE in lipopolysaccharide-induced cytoskeletal changes in mouse pulmonary microvascular endothelial cells]

OBJECTIVE

To investigate lipopolysaccharide (LPS)-induced changes of cytoskeletal filamentous actin in primary isolated pulmonary microvascular endothelial cells (PMVECs) from wild-type and RAGE knock-out mouse.

METHODS

The lungs of wild-type and RAGE knock-out mice were digested with collagenase type I to obtain endothelial cells purified by anti-CD31-coupled magnetic beads. The PMVEC identified by factor VIII labeling were stimulated with LPS at different concentrations and the changes of filamentous actin were observed by confocal microscopy.

RESULTS

The cultured primary cells showed typical endothelial cell phenotype as examined with factor VIII labeling. LPS stimulation caused rearrangement of the cytoskeletal filament F-actin in wild-type mouse PMVECs with stress fiber formation, but such changes were not obvious in RAGE knock-out mouse PMVECs.

CONCLUSION

Mouse PMVECs of a high purity can be obtained by immune magnetic beads. RAGE is involved in LPS-induced destruction of mouse PMVEC cytoskeletons.

Oriented matrix promotes directional tubulogenesis

Detailed control over the structural organization of scaffolds and engineered tissue constructs is a critical need in the quest to engineer functional tissues using biomaterials. This work presents a new approach to spatially direct endothelial tubulogenesis. Micropatterned fibronectin substrates were used to control lung fibroblast adhesion and growth and the subsequent deposition of fibroblast-derived matrix during culture. The fibroblast-derived matrix produced on the micropatterned substrates was tightly oriented by these patterns, with an average variation of only 8.5°. Further, regions of this oriented extracellular matrix provided directional control of developing endothelial tubes to within 10° of the original micropatterned substrate design. Endothelial cells seeded directly onto the micropatterned substrate did not form tubes. A metric for matrix anisotropy showed a relationship between the fibroblast-derived matrix and the endothelial tubes that were subsequently developed on the same micropatterns with a resulting aspect ratio over 1.5 for endothelial tubulogenesis. Micropatterns in "L" and "Y" shapes were used to direct endothelial tubes to turn and branch with the same level of precision. These data demonstrate that anisotropic fibroblast-derived matrices instruct the alignment and shape of endothelial tube networks, thereby introducing an approach that could be adapted for future design of microvascular implants featuring organ-specific natural matrix that patterns microvascular growth.

[THE AGING OF MICROVASCULAR NETWORK FORMED IN CORTEX FOLLOWING INTRACEREBRAL TRANSPLANTATION OF MESENCHYMAL STEM CELLS]

Using a TV device to study microcirculation in brain we found that intracerebral transplantation of mesenchymal stem cells to 12-months old rats led to a significant increase (circa 1,5-fold times) of microvascular density in pia tissue and to increased constriction reactions of pia arterioles in response to noradrenalin application on a brain surface. Both microvascular density and pia arterioles reactivity was completely preserved in aging until 22-24 months.

Ion transporters in brain endothelial cells that contribute to formation of brain interstitial fluid

Ions and water transported across the endothelium lining the blood–brain barrier contribute to the fluid secreted into the brain and are important in maintaining appropriate volume and ionic composition of brain interstitial fluid. Changes in this secretion process may occur after stroke. The present study identifies at transcript and protein level ion transporters involved in the movement of key ions and examines how levels of certain of these alter following oxidative stress. Immunohistochemistry provides evidence for Cl⁻/HCO₃⁻ exchanger, AE2, and Na⁺, HCO₃⁻ cotransporters, NBCe1 and NBCn1, on brain microvessels. mRNA analysis by RT-PCR reveals expression of these transporters in cultured rat brain microvascular endothelial cells (both primary and immortalized GPNT cells) and also Na⁺/H⁺ exchangers, NHE1 (primary and immortalized) and NHE2 (primary cells only). Knock-down using siRNA in immortalized GPNT cells identifies AE2 as responsible for much of the Cl⁻/HCO₃⁻ exchange following extracellular chloride removal and NHE1 as the transporter that accounts for most of the Na⁺/H⁺ exchange following intracellular acidification. Transcript levels of both AE2 and NHE1 are increased following hypoxia/reoxygenation. Further work is now required to determine the localization of the bicarbonate transporters to luminal or abluminal membranes of the endothelial cells as well as to identify and localize additional transport mechanisms that must exist for K⁺ and Cl⁻.

Bioactive copper-doped glass scaffolds can stimulate endothelial cells in co-culture in combination with mesenchymal stem cells

Bioactive glass (BG) scaffolds are being investigated for bone tissue engineering applications because of their osteoconductive and angiogenic nature. However, to increase the in vivo performance of the scaffold, including enhancing the angiogenetic growth into the scaffolds, some researchers use different modifications of the scaffold including addition of inorganic ionic components to the basic BG composition. In this study, we investigated the in vitro biocompatibility and bioactivity of Cu2+-doped BG derived scaffolds in either BMSC (bone-marrow derived mesenchymal stem cells)-only culture or co-culture of BMSC and human dermal microvascular endothelial cells (HDMEC). In BMSC-only culture, cells were seeded either directly on the scaffolds (3D or direct culture) or were exposed to ionic dissolution products of the BG scaffolds, kept in permeable cell culture inserts (2D or indirect culture). Though we did not observe any direct osteoinduction of BMSCs by alkaline phosphatase (ALP) assay or by PCR, there was increased vascular endothelial growth factor (VEGF) expression, observed by PCR and ELISA assays. Additionally, the scaffolds showed no toxicity to BMSCs and there were healthy live cells found throughout the scaffold. To analyze further the reasons behind the increased VEGF expression and to exploit the benefits of the finding, we used the indirect method with HDMECs in culture plastic and Cu2+-doped BG scaffolds with or without BMSCs in cell culture inserts. There was clear observation of increased endothelial markers by both FACS analysis and acetylated LDL (acLDL) uptake assay. Only in presence of Cu2+-doped BG scaffolds with BMSCs, a high VEGF secretion was demonstrated by ELISA; and typical tubular structures were observed in culture plastics. We conclude that Cu2+-doped BG scaffolds release Cu2+, which in turn act on BMSCs to secrete VEGF. This result is of significance for the application of BG scaffolds in bone tissue engineering approaches.

Apolipoprotein E isoform-specific effects on lipoprotein receptor processing

Recent findings indicate an isoform-specific role for apolipoprotein E (apoE) in the elimination of beta-amyloid (Aβ) from the brain. ApoE is closely associated with various lipoprotein receptors, which contribute to Aβ brain removal via metabolic clearance or transit across the blood–brain barrier (BBB). These receptors are subject to ectodomain shedding at the cell surface, which alters endocytic transport and mitigates Aβ elimination. To further understand the manner in which apoE influences Aβ brain clearance, these studies investigated the effect of apoE on lipoprotein receptor shedding. Consistent with prior reports, we observed an increased shedding of the low-density lipoprotein receptor (LDLR) and the LDLR-related protein 1 (LRP1) following Aβ exposure in human brain endothelial cells. When Aβ was co-treated with each apoE isoform, there was a reduction in Aβ-induced shedding with apoE2 and apoE3, while lipoprotein receptor shedding in the presence of apoE4 remained increased. Likewise, intracranial administration of Aβ to apoE-targeted replacement mice (expressing the human apoE isoforms) resulted in an isoform-dependent effect on lipoprotein receptor shedding in the brain (apoE4 > apoE3 > apoE2). Moreover, these results show a strong inverse correlation with our prior work in apoE transgenic mice in which apoE4 animals showed reduced Aβ clearance across the BBB compared to apoE3 animals. Based on these results, apoE4 appears less efficient than other apoE isoforms in regulating lipoprotein receptor shedding, which may explain the differential effects of these isoforms in removing Aβ from the brain.

Anatomic distribution of nerves and microvascular density in the human anterior vaginal wall: prospective study

Background

The presence of the G-spot (an assumed erotic sensitive area in the anterior wall of the vagina) remains controversial. We explored the histomorphological basis of the G-spot.

Methods

Biopsies were drawn from a 12 o’clock direction in the distal- and proximal-third areas of the anterior vagina of 32 Chinese subjects. The total number of protein gene product 9.5–immunoreactive nerves and smooth muscle actin–immunoreactive blood vessels in each specimen was quantified using the avidin-biotin-peroxidase assay.

Results

Vaginal innervation was observed in the lamina propria and muscle layer of the anterior vaginal wall. The distal-third of the anterior vaginal wall had significantly richer small-nerve-fiber innervation in the lamina propria than the proximal-third (p = 0.000) and in the vaginal muscle layer (p = 0.006). There were abundant microvessels in the lamina propria and muscle layer, but no small vessels in the lamina propria and few in the muscle layer. Significant differences were noted in the number of microvessels when comparing the distal- with proximal-third parts in the lamina propria (p = 0.046) and muscle layer (p = 0.002).

Conclusions

Significantly increased density of nerves and microvessels in the distal-third of the anterior vaginal wall could be the histomorphological basis of the G-spot. Distal anterior vaginal repair could disrupt the normal anatomy, neurovascular supply and function of the G-spot, and cause sexual dysfunction.

Vascular and neural stem cells in the gut: do they need each other?

Enteric neurons and blood vessels form intricate networks throughout the gastrointestinal tract. To support the hypothesis of a possible interaction of both networks, we investigated whether primary mesenteric vascular cells (MVCs) and enteric nervous system (ENS)-derived cells (ENSc) depend on each other using two- and three-dimensional in vitro assays. In a confrontation assay, both cell types migrated in a target-oriented manner towards each other. The migration of MVCs was significantly increased when cultured in ENSc-conditioned medium. Co-cultures of ENSc with MVCs resulted in an improved ENSc proliferation and differentiation. Moreover, we analysed the formation of the vascular and nervous system in developing mice guts. It was found that the patterning of newly formed microvessels and neural stem cells, as confirmed by nestin and SOX2 stainings, is highly correlated in all parts of the developing gut. In particular in the distal colon, nestin/SOX2-positive cells were found in the tissues adjacent to the capillaries and in the capillaries themselves. Finally, in order to provide evidences for a mutual interaction between endothelial and neural cells, the vascular patterns of a RET((-/-)) knockout mouse model as well as human Hirschsprung's cases were analysed. In the distal colon of postnatal RET((-/-)) knockout mice, the vascular and neural networks were similarly disrupted. In aganglionic zones of Hirschsprung's patients, the microvascular density was significantly increased compared with the ganglionic zone within the submucosa. Taken together, these findings indicate a strong interaction between the enteric nervous and vascular system.

Erythropoietin increases bioavailability of tetrahydrobiopterin and protects cerebral microvasculature against oxidative stress induced by eNOS uncoupling

This study was designed to determine whether treatment with erythropoietin (EPO) could protect cerebral microvasculature against the pathological consequences of endothelial nitric oxide (NO) synthase uncoupling. Wild-type and GTP cyclohydrolase I (GTPCH-I)-deficient hph1 mice were administered EPO (1000 U/kg/day, s.c., 3 days). Cerebral microvessels of hph1 mice demonstrated reduced tetrahydrobiopterin (BH4) bioavailability, increased production of superoxide anions and impaired endothelial NO signaling. Treatment of hph1 mice with EPO attenuated the levels of 7,8-dihydrobiopterin, the oxidized product of BH4, and significantly increased the ratio of BH4 to 7,8-dihydrobiopterin. Moreover, EPO decreased the levels of superoxide anions and increased NO bioavailability in cerebral microvessels of hph1 mice. Attenuated oxidation of BH4 and inhibition of endothelial NO synthase uncoupling were explained by the increased expression of antioxidant proteins, manganese superoxide dismutase, and catalase. The protective effects of EPO observed in cerebral microvessels of hph1 mice were also observed in GTPCH-I siRNA-treated human brain microvascular endothelial cells exposed to EPO (1 U/mL or 10 U/mL; 3 days). Our results suggest that EPO might protect the neurovascular unit against oxidative stress by restoring bioavailability of BH4 and endothelial NO in the cerebral microvascular endothelium. We demonstrate that treatment with erythropoietin (EPO) could protect cerebral microvasculature against the pathological consequences of endothelial nitric oxide (NO) synthase uncoupling. Our results suggest that EPO might protect the neurovascular unit against oxidative stress by restoring bioavailability of tetrahydrobiopterin (BH4) and endothelial nitric oxide.

Selenoglycoproteins attenuate adhesion of tumor cells to the brain microvascular endothelium via a process involving NF-κB activation

Selenium-containing compounds and selenized yeast have anticancer properties. In order to address possible mechanisms involved in these effects, selenoglycoproteins (SGPs) were extracted from selenium-enriched yeast at pH 4.0 and 6.5 (the fractions are called SGP40 and SGP65, respectively), followed by evaluation of their impact on the interactions of lung and breast tumor cells with human brain microvascular endothelial cells (HBMECs). Extracted SGPs, especially SGP40, significantly inhibited adhesion of tumor cells to HBMECs and their transendothelial migration. Because the active components of SGPs are unknown, small selenium-containing compounds [leucyl-valyl-selenomethionyl-arginine (LVSe-MR) and methylselenoadenosine (M-Se-A)], which are normally present in selenized yeast, were introduced as additional treatment groups. Treatment of HBMECs with SGP40, LVSe-MR and M-Se-A induced changes in gene signatures, which suggested a central involvement of nuclear factor (NF)-κB-dependent pathway. These observations were confirmed in the subsequent analysis of NF-κB DNA binding activity, quantitative measurements of the expression of selected genes and proteins, and tumor cell adhesion assay with a specific NF-κB inhibitor as the additional treatment factor. These findings indicate that specific organic selenium-containing compounds have the ability to inhibit tumor cell adhesion to brain endothelial cells via down-regulation of NF-κB. SGPs appear to be more effective than small selenium-containing compounds, suggesting the role of not only selenium but also the glycoprotein component in the observed protective impact.

Vasodilator-stimulated phosphoprotein protects against vascular inflammation and insulin resistance

Among the pleotropic effects of endothelial nitric oxide (NO) is protection against vascular inflammation during high-fat diet (HFD) feeding. The current work investigated the role of the enzyme vasodilatory-stimulated phosphoprotein (VASP) as a downstream mediator of the anti-inflammatory effect of NO signaling in vascular tissue. Relative to mice fed a low-fat diet (LFD), levels of VASP Ser(239) phosphorylation, a marker of VASP activation, were dramatically reduced in aortic tissue of mice with obesity induced by consuming a HFD. As reported previously, the effect of the HFD was associated with increased aortic inflammation, as measured by increased NF-κB-dependent gene expression, and reduced vascular insulin sensitivity (including insulin-stimulated phosphorylation of eNOS and Akt). These effects of the HFD were recapitulated by VASP knockout, implying a physiological role for VASP to constrain inflammatory signaling and thereby maintain vascular insulin sensitivity. Conversely, overexpression of VASP in endothelial cells blocked inflammation and insulin resistance induced by palmitate. The finding that transplantation of bone marrow from VASP-deficient donors into normal recipients does not recapitulate the vascular effects of whole body VASP deficiency suggests that the protective effects of this enzyme are not mediated in immune or other bone marrow-derived cells. These studies implicate VASP as a downstream mediator of the NO/cGMP pathway that is both necessary and sufficient to protect against vascular inflammation and insulin resistance. As such, this work identifies VASP as a potential therapeutic target in the treatment of obesity-related vascular dysfunction.

[A method for isolated culture of bone microvascular endothelial cells of human femoral head]

OBJCETIVE

To investigate the method of separation of culture of bone microvascular endothelial cells (BMECs) of human femoral head in vitro.

METHODS

From October 2013 to January 2014,15 femoral heads without pathologic change from patients resected during hip replacement were selected involving 2 males and 13 females with a mean age of 71.2 years old ranging from 38 to 92. Cancellous bone in femoral head was bited into broken bone grain and transfered into medium in aseptic contidion. Cells were isolated by the methods of enzymic digestion and density gradient centrifugation,purified by differiential attachment. The characteristics of cells was observed by inverted microscope. vWF and CD31 immunofluorescence analysis was applied for identification of cells.

RESULTS

The number of cells was positively correlated with patients' age after 24 hours in primary culture. The older patients had the less cells numbered. After 4 to 5 days' culture, primary cells appeared short spindle,polygon shaped and cobblestone-like morphology. After 7 to 10 days' culture, primary cells proliferated densely, became fusion, arranged in swirl, and contact inhibition appeared significantly. Immunofluorescence staining revealed the cells were 100% positive for vWF and CD31, and it showed that the cultured cells were BMECs.

CONCLUSION

It was a simple, steady, effective method with good reproducibility, by which highly purified human BMECs can be obtained.

PKA compartmentalization via AKAP220 and AKAP12 contributes to endothelial barrier regulation

cAMP-mediated PKA signaling is the main known pathway involved in maintenance of the endothelial barrier. Tight regulation of PKA function can be achieved by discrete compartmentalization of the enzyme via physical interaction with A-kinase anchoring proteins (AKAPs). Here, we investigated the role of AKAPs 220 and 12 in endothelial barrier regulation. Analysis of human and mouse microvascular endothelial cells as well as isolated rat mesenteric microvessels was performed using TAT-Ahx-AKAPis peptide, designed to competitively inhibit PKA-AKAP interaction. In vivo microvessel hydraulic conductivity and in vitro transendothelial electrical resistance measurements showed that this peptide destabilized endothelial barrier properties, and dampened the cAMP-mediated endothelial barrier stabilization induced by forskolin and rolipram. Immunofluorescence analysis revealed that TAT-Ahx-AKAPis led to both adherens junctions and actin cytoskeleton reorganization. Those effects were paralleled by redistribution of PKA and Rac1 from endothelial junctions and by Rac1 inactivation. Similarly, membrane localization of AKAP220 was also reduced. In addition, depletion of either AKAP12 or AKAP220 significantly impaired endothelial barrier function and AKAP12 was also shown to interfere with cAMP-mediated barrier enhancement. Furthermore, immunoprecipitation analysis demonstrated that AKAP220 interacts not only with PKA but also with VE-cadherin and ß-catenin. Taken together, these results indicate that AKAP-mediated PKA subcellular compartmentalization is involved in endothelial barrier regulation. More specifically, AKAP220 and AKAP12 contribute to endothelial barrier function and AKAP12 is required for cAMP-mediated barrier stabilization.

Modulation of selectin-mediated adhesion of flowing lymphoma and bone marrow cells by immobilized SDF-1

The α-chemokine, stromal-derived factor-1 (SDF-1), has been linked to the homing of circulating tumor cells to bone. SDF-1 is expressed by bone microvascular cells and osteoblasts and normally functions to attract blood-borne hematopoietic stem and progenitor cells to marrow. It has been shown that treatment of cancer cells with soluble SDF-1 results in a more aggressive phenotype; however, the relevance of the administration of the soluble protein is unclear. As such, a flow device was functionalized with P-selectin and SDF-1 to mimic the bone marrow microvasculature and the initial steps of cell adhesion. The introduction of SDF-1 onto the adhesive surface was found to significantly enhance the adhesion of lymphoma cells, as well as low-density bone marrow cells (LDBMC), both in terms of the number of adherent cells and the strength of cell adhesion. Thus, SDF-1 has a synergistic effect with P-selectin on cancer cell adhesion and may be sufficient to promote preferential metastasis to bone.

In vivo fast variable focus photoacoustic microscopy using an electrically tunable lens

Fast focusing scan over a large depth range is challenging in photoacoustic microscopic imaging. In this paper, a fast variable focus photoacoustic microscopy (VF-PAM) with a large range of imaging depth was presented by using an electrically tunable lens (ETL). The ETL controlled the divergence angle of the laser beam for fast and continuous focus-shifting in depth direction with the shifting time of 15 ms, and 2.82 mm focus-shifting range with a 1 µm shifting accuracy was achieved by combining the ETL with a 0.3 NA plan microscope objective lens. Carbon fibers imaging verified the depth imaging ability of the system, in vivo microvasculature of mouse ear and brain tissues of the mouse imaging further demonstrated the focusing scan ability in biomedical application. The fast VF-PAM system allows substantial shortening of the focus-shifting time, which will be more conducive to studying living biological tissue, and will promote the development of in vivo noninvasive PA depth imaging without mechanical scan.

Chemokine receptor CXCR7 is a functional receptor for CXCL12 in brain endothelial cells

The chemokine CXCL12 regulates multiple cell functions through its receptor, CXCR4. However, recent studies have shown that CXCL12 also binds a second receptor, CXCR7, to potentiate signal transduction and cell activity. In contrast to CXCL12/CXCR4, few studies have focused on the role of CXCR7 in vascular biology and its role in human brain microvascular endothelial cells (HBMECs) remains unclear. In this report, we used complementary methods, including immunocytofluorescence, Western blot, and flow cytometry analyses, to demonstrate that CXCR7 was expressed on HBMECs. We then employed short hairpin RNA (shRNA) technology to knockdown CXCR7 in HBMECs. Knockdown of CXCR7 in HBMECs resulted in significantly reduced HBMEC proliferation, tube formation, and migration, as well as adhesion to matrigel and tumor cells. Blocking CXCR7 with a specific antibody or small molecule antagonist similarly disrupted HBMEC binding to matrigel or tumor cells. We found that tumor necrosis factor (TNF)-α induced CXCR7 in a time and dose-response manner and that this increase preceded an increase in vascular cell adhesion molecule-1 (VCAM-1). Knockdown of CXCR7 resulted in suppression of VCAM-1, suggesting that the reduced binding of CXCR7-knockdown HBMECs may result from suppression of VCAM-1. Collectively, CXCR7 acted as a functional receptor for CXCL12 in brain endothelial cells. Targeting CXCR7 in tumor vasculature may provide novel opportunities for improving brain tumor therapy.

Cell type-specific recycling of tetrahydrobiopterin by dihydrofolate reductase explains differential effects of 7,8-dihydrobiopterin on endothelial nitric oxide synthase uncoupling

(6R)-5,6,7,8-Tetrahydro-L-biopterin (BH4) availability regulates nitric oxide and superoxide formation by endothelial nitric oxide synthase (eNOS). At low BH4 or low BH4 to 7,8-dihydrobiopterin (BH2) ratios the enzyme becomes uncoupled and generates superoxide at the expense of NO. We studied the effects of exogenously added BH2 on intracellular BH4/BH2 ratios and eNOS activity in different types of endothelial cells. Incubation of porcine aortic endothelial cells with BH2 increased BH4/BH2 ratios from 8.4 (controls) and 0.5 (BH4-depleted cells) up to ~20, demonstrating efficient reduction of BH2. Uncoupled eNOS activity observed in BH4-depleted cells was prevented by preincubation with BH2. Recycling of BH4 was much less efficient in human endothelial cells isolated from umbilical veins or derived from dermal microvessels (HMEC-1 cells), which exhibited eNOS uncoupling and low BH4/BH2 ratios under basal conditions and responded to exogenous BH2 with only moderate increases in BH4/BH2 ratios. The kinetics of dihydrofolate reductase-catalyzed BH4 recycling in endothelial cytosols showed that the apparent BH2 affinity of the enzyme was 50- to 300-fold higher in porcine than in human cell preparations. Thus, the differential regulation of eNOS uncoupling in different types of endothelial cells may be explained by striking differences in the apparent BH2 affinity of dihydrofolate reductase.

P-glycoprotein mediated efflux limits the transport of the novel anti-Parkinson's disease candidate drug FLZ across the physiological and PD pathological in vitro BBB models

FLZ, a novel anti-Parkinson's disease (PD) candidate drug, has shown poor blood-brain barrier (BBB) penetration based on the pharmacokinetic study using rat brain. P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are two important transporters obstructing substrates entry into the CNS as well as in relation to PD neuropathology. However, it is unclear whether P-gp and BCRP are involved in low BBB permeability of FLZ and what the differences of FLZ brain penetration are between normal and Parkinson's conditions. For this purpose, in vitro BBB models mimicking physiological and PD pathological-related BBB properties were constructed by C6 astroglial cells co-cultured with primary normal or PD rat cerebral microvessel endothelial cells (rCMECs) and in vitro permeability experiments of FLZ were carried out. High transepithelial electrical resistance (TEER) and low permeability for sodium fluorescein (NaF) confirmed the BBB functionality of the two models. Significantly greater expressions of P-gp and BCRP were detected in PD rCMECs associated with the lower in vitro BBB permeability of FLZ in pathological BBB model compared with physiological model. In transport studies only P-gp blocker effectively inhibited the efflux of FLZ, which was consistent with the in vivo permeability data. This result was also confirmed by ATPase assays, suggesting FLZ is a substrate for P-gp but not BCRP. The present study first established in vitro BBB models reproducing PD-related changes of BBB functions in vivo and demonstrated that poor brain penetration of FLZ and low BBB permeability were due to the P-gp transport.

[A method for primary culture of pulmonary microvascular endothelial cells]

OBJECTIVE

To explore a simple and practical method of primarily culturing rat pulmonary microvascular endothelial cells (PMECs) in vitro, and observe the cell growth status and identify the PMECs.

METHODS

Wistar rats (n=40, aged 4-5 weeks) were sacrificed to take the lung tissue. After removal of pleura, the peripheral lung tissues were cut into pieces (1 mm(3)) in aseptic condition. The endothelial cells were cultured in the DMEM medium containing heparin sodium and in the RPMI1640 medium supplemented with special additives or not, respectively. Cell growth and morphology was observed under an inverted microscope. The expression of CD31 in cells was detected by immunofluorescence staining.

RESULTS

After incubation for 24 hours, PMECs in the medium containing special additives were the most in number and purity compared with the other two culture systems. At 24 hours, endothelial cells migrated from the lung tissue, and at 14 days, the cells aggregated and grew obviously, exhibiting a polygon shape, being tightly arranged and paving the base of Petri dish. After sub-culturing, the cells spread much more and most cells became spindle shaped, which showed a tendency of endothelial cell angiogenesis in vitro. CD31 was positive in immunofluorescence staining.

CONCLUSION

The adherent culture method of tissue explants in the medium added by the special additives was proved to a good method to obtain a high-purity rat PMECs in vitro.

Differential angiogenic properties of lithium chloride in vitro and in vivo

Wnt/β-catenin signaling induced by the Norrin/Frizzled-4 pathway has been shown to improve capillary repair following oxygen induced retinopathy (OIR) in the mouse, a model for retinopathy of prematurity. Here we investigated if treatment with the monovalent cation lithium that has been shown to augment Wnt/β-catenin signaling in vitro and in vivo has similar effects. In cultured human microvascular endothelial cells, LiCl as well as SB 216763, another small molecule that activates Wnt/β-catenin signaling, induced proliferation, survival and migration, which are all common parameters for angiogenic properties in vitro. Moreover, treatment with both agents caused an increase in the levels of β-catenin and their translocation to nuclei while quercetin, an inhibitor of Wnt/β-catenin signaling, completely blocked the effects of LiCl on proliferation. In mice with OIR, intraperitonal or intravitreal treatment with LiCl markedly increased the retinal levels of β-catenin, but did not improve capillary repair. In contrast, repair was significantly improved following intravitreal treatment with Norrin. The effects of LiCl on HDMEC in vitro have minor relevance for OIR in vivo, and the influence of the Norrin/Frizzled-4 pathway on capillary repair in OIR is not reproducible upon enhancing Wnt/β-catenin signaling by LiCl treatment strongly indicating the presence of additional and essential mechanisms.

Aging impairs transcriptional regulation of vascular endothelial growth factor in human microvascular endothelial cells: implications for angiogenesis and cell survival

In some tissues, aging impairs angiogenesis and reduces expression of vascular endothelial growth factor A (VEGF), a fundamental regulator of angiogenesis. We previously examined angiogenesis in aging and young gastric mucosa in vivo and in vitro and showed that an imbalance between expressions of VEGF (pro-angiogenic factor) and endostatin (anti-angiogenic protein) results in an aging-related impairment of angiogenesis in rats. However, the human relevance of these findings, and whether these mechanisms apply to endothelial cells derived from other tissues, is not clear. Since P-STAT3 and P-CREB are transcription factors that, in association with HIF-1α, can activate VEGF gene expression in some cells (e.g., liver cancer cells, vascular smooth muscle cells), we examined the expression of these two proteins in human dermal microvascular endothelial cells (HMVECs) derived from aging and neonatal individuals. We examined and quantified in vitro angiogenesis, expression of VEGF, P-STAT3, P-CREB and importin-α in HMVECs isolated from neonates (neonatal) and a 66 year old subject (aging). We also examined the effects of treatment with exogenous VEGF and endostatin on in vitro angiogenesis in these cells. Endothelial cells isolated from aging individuals had impaired angiogenesis (vs. neonatal endothelial cells) and reduced expression of VEGF mRNA and protein. Aged HMVECs also had reduced importin-α expression, and reduced expression and nuclear translocation of P-STAT3 and P-CREB. Reduced VEGF gene expression in aged HMVECs strongly correlated with the decreased levels of P-STAT3, P-CREB and importin-α in these cells. Our study clearly demonstrates that endothelial cells from aging individuals have impaired angiogenesis and reduced expression of VEGF likely due to impaired nuclear transport of P-STAT3 and P-CREB transcription factors in these cells.

Des-acyl ghrelin protects microvascular endothelial cells from oxidative stress-induced apoptosis through sirtuin 1 signaling pathway

OBJECTIVE

Ghrelin is a stomach-derived hormone. Acylation of ghrelin has been essential for its biological activities such as stimulating appetite. On the other hand, the function of des-acyl ghrelin (Des-G) has not been fully elucidated. The aim of the present study is to examine the anti-apoptotic effect of Des-G on endothelial cells.

MATERIALS/METHODS

After human retinal microvascular endothelial cells (RMECs) were pretreated with or without 100nmol/L Des-G, apoptosis was induced with 0.1mmol/L hydrogen peroxide (H2O2). For pharmacological inhibition of surtuin 1 (SIRT1) catalytic activity, the cells were treated with 10μmol/L Ex-527. Inhibition of SIRT1 with siRNA was also performed. The quantitative estimation of DNA fragmentation was used as a marker of apoptosis. Furthermore, total SIRT activity in nuclear extracts, mRNA and protein levels of SIRT1, manganese superoxide dismutase (MnSOD) and catalase were determined.

RESULTS

Des-G pretreatment protected RMECs from oxidative stress-induced apoptosis and increased SIRTs deacetylase activity in nuclear extracts. On the other hand, both pharmacological and siRNA mediated inhibition of SIRT1 attenuated the anti-apoptotic effect of Des-G. Moreover, Des-G increased mRNA and protein levels of SIRT1 and antioxidant enzymes such as MnSOD and CAT, which are downstream targets of SIRT1. Although the treatment of Ex-527 did not alter mRNA expression levels of SIRT1, it decreased mRNA expression levels of antioxidant enzymes in the cells with Des-G pretreatment.

CONCLUSIONS

Our results suggest that SIRT1 signaling pathway contributes to protective effect of Des-G against oxidative stress-induced apoptosis.

Knock-down of CD44 regulates endothelial cell differentiation via NFκB-mediated chemokine production

A striking feature of microvascular endothelial cells is their capacity to fuse and differentiate into tubular structures when grown in three-dimensional (3D) extracellular matrices, in collagen or Matrigel, mimicking the in vivo blood vessel formation. In this study we demonstrate that human telomerase-immortalised foreskin microvascular endothelial (TIME) cells express high levels of the hyaluronan receptor CD44 and the hyaluronidase HYAL2. Knock-down of CD44 or HYAL2 resulted in an inability of TIME cells to form a tubular network, suggesting a key regulatory role of hyaluronan in controlling TIME cell tubulogenesis in 3D matrices. Knock-down of CD44 resulted in an upregulation of mRNA expression of the chemokines CXCL9 and CXCL12, as well as their receptors CXCR3 and CXCR4. This was accompanied by a defect maturation of the tubular structure network and increased phosphorylation of the inhibitor of NFκB kinase (IKK) complex and thus translocation of NFκB into the nucleus and activation of chemokine targed genes. Furthermore, the interaction between CD44 and hyaluronan determines the adhesion of breast cancer cells. In summary, our observations support the notion that the interaction between CD44 and hyaluronan regulates microvascular endothelial cell tubulogenesis by affecting the expression of cytokines and their receptors, as well as breast cancer dissemination.

Simultaneous viewing of individual cells and ambient microvasculature using optical absorption and fluorescence contrasts

Viewing individual cells and ambient microvasculature simultaneously is crucial for understanding tumor angiogenesis and microenvironments. We developed a confocal fluorescence microscopy (CFM) and photoacoustic microscopy (PAM) dual-modality imaging system that can assess fluorescent contrast and optical absorption contrast in biologic samples simultaneously. After staining tissues with fluorescent dye at an appropriate concentration, each laser pulse can generate not only sufficient fluorescent signals from cells for CFM but also sufficient photoacoustic signals from microvessels for PAM. To explore the potential of this system for diagnosis of bladder cancer, experiments were conducted on a rat bladder model. The CFM image depicts the morphology of individual cells, showing not only large polygonal umbrella cells but also intracellular components. The PAM image acquired at the same time provides complementary information on the microvascular distribution in the bladder wall, ranging from large vessels to capillaries. This device provides an opportunity to realize both histologic assay and microvascular characterization simultaneously. The combination of the information of individual cells and local microvasculature in the bladder offers the capability of envisioning the viability and activeness of these cells and holds promise for more comprehensive study of bladder cancer in vivo.

Regulation of monocarboxylic acid transporter-1 by cAMP dependent vesicular trafficking in brain microvascular endothelial cells

In this study, a detailed characterization of Monocarboxylic Acid Transporter-1 (Mct1) in cytoplasmic vesicles of cultured rat brain microvascular endothelial cells shows them to be a diverse population of endosomes intrinsic to the regulation of the transporter by a brief 25 to 30 minute exposure to the membrane permeant cAMP analog, 8Br-cAMP. The vesicles are heterogeneous in size, mobility, internal pH, and co-localize with discreet markers of particular types of endosomes including early endosomes, clathrin coated vesicles, caveolar vesicles, trans-golgi, and lysosomes. The vesicular localization of Mct1 was not dependent on its N or C termini, however, the size and pH of Mct1 vesicles was increased by deletion of either terminus demonstrating a role for the termini in vesicular trafficking of Mct1. Using a novel BCECF-AM based assay developed in this study, 8Br-cAMP was shown to decrease the pH of Mct1 vesicles after 25 minutes. This result and method were confirmed in experiments with a ratiometric pH-sensitive EGFP-mCherry dual tagged Mct1 construct. Overall, the results indicate that cAMP signaling reduces the functionality of Mct1 in cerebrovascular endothelial cells by facilitating its entry into a highly dynamic vesicular trafficking pathway that appears to lead to the transporter's trafficking to autophagosomes and lysosomes.

Angiotensin II evokes angiogenic signals within skeletal muscle through co-ordinated effects on skeletal myocytes and endothelial cells

Skeletal muscle overload induces the expression of angiogenic factors such as vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP)-2, leading to new capillary growth. We found that the overload-induced increase in angiogenesis, as well as increases in VEGF, MMP-2 and MT1-MMP transcripts were abrogated in muscle VEGF KO mice, highlighting the critical role of myocyte-derived VEGF in controlling this process. The upstream mediators that contribute to overload-induced expression of VEGF have yet to be ascertained. We found that muscle overload increased angiotensinogen expression, a precursor of angiotensin (Ang) II, and that Ang II signaling played an important role in basal VEGF production in C2C12 cells. Furthermore, matrix-bound VEGF released from myoblasts induced the activation of endothelial cells, as evidenced by elevated endothelial cell phospho-p38 levels. We also found that exogenous Ang II elevates VEGF expression, as well as MMP-2 transcript levels in C2C12 myotubes. Interestingly, these responses also were observed in skeletal muscle endothelial cells in response to Ang II treatment, indicating that these cells also can respond directly to the stimulus. The involvement of Ang II in muscle overload-induced angiogenesis was assessed. We found that blockade of AT1R-dependent Ang II signaling using losartan did not attenuate capillary growth. Surprisingly, increased levels of VEGF protein were detected in overloaded muscle from losartan-treated rats. Similarly, we observed elevated VEGF production in cultured endothelial cells treated with losartan alone or in combination with Ang II. These studies conclusively establish the requirement for muscle derived VEGF in overload-induced angiogenesis and highlight a role for Ang II in basal VEGF production in skeletal muscle. However, while Ang II signaling is activated following overload and plays a role in muscle VEGF production, inhibition of this pathway is not sufficient to halt overload-induced angiogenesis, indicating that AT1-independent signals maintain VEGF production in losartan-treated muscle.

Purification of endothelial cells from rat brain

Endothelial cells make up a minor population of cells in a tissue, but play a major role in tissue homeostasis, as well as in diverse pathologies. To understand the biology of cerebral endothelium, purification and characterization of the cerebrocortical endothelial cell population is highly desirable. For this purpose, rat brains are mechanically minced and subsequently digested enzymatically with collagenase. In this protocol, the capillary fraction (microvessels) and the fraction enriched in small arterioles and arteries (resistance vessels) are separated. Each produces its own homogenous endothelial culture, namely, MV-EC and RV-EC. The endothelial origin of these cells is identified by positive immunofluorescent staining for the endothelial cell surface antigen Factor VIII. Unlike MV-EC, RV-EC cultures are capable of serial cultivation for up to 15 passages. Primary MV-ECs are able to retain their characteristic endothelial morphology for 6-8 weeks.

Microvascular protective role of pericytes in melatonin-treated spinal cord injury in the C57BL/6 mice

BACKGROUND

Pericytes, located on microvessels, help to maintain vascular stability and blood-brain barrier integrity. The influence of pericytes on microvessels after spinal cord injury (SCI) is less clear. Therefore, the aim of this study was to investigate whether pericytes took a protective effect on microvessels in melatonin-treated SCI.

METHODS

C57BL/6 mice were randomly divided into three groups: sham group, SCI group, and melatonin group (n = 27 per group). Functional recovery was evaluated using the Basso Mouse Scale. Motor neurons were observed using hematoxylin and eosin staining. Pericyte coverage was analyzed using immunofluorescence. Permeability of blood-spinal cord barrier (BSCB) was assessed by administration of Evan's Blue. Protein levels of occludin, aquaporin-4 (AQP4), angiopoietin-1 (Ang1), intercellular cell adhesion molecule-1 (ICAM-1), Bcl-2, and Bax were determined using Western blotting. Mimicking the pathological conditions of SCI, melatonin-treated primary pericytes were subjected to oxygen-glucose deprivation/reperfusion (OGD/R). Secretion of Ang1 was analyzed using an enzyme-linked immunosorbent assay, and the expression of ICAM-1 was detected by immunofluorescence.

RESULTS

Melatonin treatment improved locomotor functional outcome and rescued motor neurons. Pericyte coverage was significantly reduced after SCI; melatonin treatment alleviated the loss of pericyte coverage and rescued perfused microvessels 7 days after injury. The permeability of BSCB and loss of occludin were attenuated, and edema formation and upregulation of AQP4 were inhibited, after melatonin treatment. The expression of Ang1 and Bcl-2 was improved, while the expression of ICAM-1 and Bax was inhibited, in melatonin-treated SCI mice. Furthermore, the secretion of Ang1 was increased and the expression of ICAM-1 was inhibited in melatonin-treated pericytes after OGD/R.

CONCLUSIONS

Melatonin ameliorated the loss of blood vessels and disruption of BSCB to exert a protective effect on SCI, which might be mediated by increased pericyte coverage. The upregulation of Ang1 in pericytes could inhibit inflammation and apoptosis to protect the microvessels.

A neurovascular blood-brain barrier in vitro model

The cerebral microvasculature possesses certain cellular features that constitute the blood-brain barrier (BBB) (Abbott et al., Neurobiol Dis 37:13-25, 2010). This dynamic barrier separates the brain parenchyma from peripheral blood flow and is of tremendous clinical importance: for example, BBB breakdown as in stroke is associated with the development of brain edema (Rosenberg and Yang, Neurosurg Focus 22:E4, 2007), inflammation (Kuhlmann et al., Neurosci Lett 449:168-172, 2009; Coisne and Engelhardt, Antioxid Redox Signal 15:1285-1303, 2011), and increased mortality. In vivo, the BBB consists of brain endothelial cells (BEC) that are embedded within a precisely regulated environment containing astrocytes, pericytes, smooth muscle cells, and glial cells. These cells experience modulation by various pathways of intercellular communication and by pathophysiological processes, e.g., through neurovascular coupling (Attwell et al., Nature 468:232-243, 2010), cortical spreading depression (Gursoy-Ozdemir et al., J Clin Invest 113:1447-1455, 2004), or formation of oxidative stress (Yemisci et al., Nat Med 15:1031-1037, 2009). Hence, this interdependent assembly of cells is referred to as the neurovascular unit (NVU) (Zlokovic, Nat Med 16:1370-1371, 2010; Zlokovic, Neuron 57:178-201, 2008). Experimental approaches to investigate the BBB in vitro are highly desirable to study the cerebral endothelium in health and disease. However, due to the complex interactions taking place within the NVU in vivo, it is difficult to mimic this interplay in vitro.Here, we describe a murine blood-brain barrier coculture model consisting of cortical organotypic slice cultures and brain endothelial cells that includes most of the cellular components of the NVU including neurons, astrocytes, and brain endothelial cells. This model allows the experimental analysis of several crucial BBB parameters such as transendothelial electrical resistance or tight junction protein localization by immunohistochemistry and live cell imaging of reactive oxygen species.

[Mesenchymal stem sell donor age effect on the cerebral cortex microvascular net density in old age rats-recipients of transplant]

Male Wistar-Kyoto rats aged 22-24 months were intracerebrally transplanted with syngenic bone marrow mesenchymal stem cells (BM MSC) established from the donor aged 3-4 months and 20-22 months, respectively. Using a TV device to study microcirculation in vivo, we have established that transplantation of BM MSC from young donors increased a density of the microvascular network in the pia mater of the sensorimotor cortex in old rats approximately 1.9-fold, comparing to age-matched controls, while a density of the arteriolar compartment increased approximately 2.1-fold. Transplantation of BM MSC from old donors did not lead to the significant increase in the density of the microvascular network in the pia mater, while a density of the arteriolar compartment increased approximately 1.5-fold.

Assays to examine endothelial cell migration, tube formation, and gene expression profiles

Common methods for studying angiogenesis in vitro include the tube formation assay, the migration assay, and the study of the endothelial genome. The formation of capillary-like tubes in vitro on basement membrane matrix mimics many steps of the angiogenesis process in vivo and is used widely as a screening test for angiogenic or antiangiogenic factors. Other assays related to the study of angiogenesis include the cell migration assay, the study of gene expression changes during the process of angiogenesis, and the study of endothelial-derived microparticles. Protocols for these procedures will be described here.

Isolation and culture of primary pericytes from mouse brain

Pericytes are perivascular cells that play an important role in the development, maturation, and remodeling of blood vessels. However, studies of this important cell type on vascular remodeling have been hindered due to the difficulty of culturing pericytes in adequate numbers to high purity. In this chapter, we present a novel yet simple method to isolate and culture large numbers of pure pericytes from the mouse central nervous system (CNS). In our approach, vascular cells obtained from adult mice brains are cultured initially under conditions optimized for endothelial cells. Following two passages, the medium is switched over to optimize pericyte growth. After growing the cells for 2-3 additional passages, this approach produces a largely homogeneous population of cells that express the pericyte markers NG2, PDGFβ receptor, and CD146 but are negative for markers of endothelial cells (CD31), astrocytes (GFAP), and microglia (Mac-1), demonstrating a highly pure pericyte culture. Thus, our technique provides an effective method to culture CNS pericytes that is easy to establish and provides large numbers of highly pure pericytes for extended periods of time. This system provides a useful tool for those wishing to study pericyte behavior.

Generation of primary cultures of bovine brain endothelial cells and setup of cocultures with rat astrocytes

In vitro models of the blood-brain barrier are useful tools to study blood-brain barrier function as well as drug permeation from the systemic circulation to the brain parenchyma. However, a large number of the available in vitro models fail to reflect the tightness of the in vivo blood-brain barrier. The present protocol describes the setup of an in vitro coculture model based on primary cultures of endothelial cells from bovine brain microvessels and primary cultures of rat astrocytes. The model displays a high electrical tightness and expresses blood-brain barrier marker proteins.

The effect of detergents on the basement membrane complex of a biologic scaffold material

The basement membrane complex (BMC) is a critical component of the extracellular matrix (ECM) that supports and facilitates the growth of cells. This study investigates four detergents commonly used in the process of tissue decellularization and their effect upon the BMC. The BMC of porcine urinary bladder was subjected to 3% Triton-X 100, 8mM 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), 4% sodium deoxycholate or 1% sodium dodecyl sulfate (SDS) for 24h. The BMC structure for each treatment group was assessed by immunolabeling, scanning electron microscopy (SEM) and second harmonic generation (SHG) imaging of the fiber network. The composition was assessed by quantification of dsDNA, glycosaminoglycans (GAG) and collagen content. The results showed that collagen fibers within samples treated with 1% SDS and 8mM CHAPS were denatured, and the ECM contained fewer GAG compared with samples treated with 3% Triton X-100 or 4% sodium deoxycholate. Human microvascular endothelial cells (HMEC) were seeded onto each BMC and cultured for 7 days. Cell-ECM interactions were investigated by immunolabeling for integrin β-1, SEM imaging and semi-quantitative assessment of cellular infiltration, phenotype and confluence. HMEC cultured on a BMC treated with 3% Triton X-100 were more confluent and had a normal phenotype compared with HMEC cultured on a BMC treated with 4% sodium deoxycholate, 8mM CHAPS and 1% SDS. Both 8mM CHAPS and 1% SDS damaged the BMC to the extent that seeded HMEC were able to infiltrate the damaged sub-basement membrane tissue, showed decreased confluence and an atypical phenotype. The choice of detergents used for tissue decellularization can have a marked effect upon the integrity of the BMC of the resultant bioscaffold.

In vitro models of the blood-brain barrier

The blood-brain barrier (BBB) proper is composed of endothelial cells (ECs) of the cerebral microvasculature, which are interconnected by tight junctions (TJs) that in turn form a physical barrier restricting paracellular flux. Tight control of vascular permeability is essential for the homeostasis and functionality of the central nervous system (CNS). In vitro BBB models have been in use for decades and have been of great benefit in the process of investigating and understanding the cellular and molecular mechanisms underlying BBB establishment. BBB integrity changes can be addressed in vitro by determining cell monolayer permeability (Pe) to different solutes and measuring trans-endothelial electrical resistance (TEER).This chapter describes procedures that can be utilized for both freshly isolated mouse brain microvascular ECs (MBMECs) and murine or human brain EC lines (bEnd5 or hCMEC/D3), cultivated either as a single monolayer or in cocultivation with primary mouse astrocytes (ACs). It starts with detailed information on how to perform transwell cell culture, including coating of inserts and seeding of the ECs and ACs. Moreover, it encompasses instructions for electrical assessment of the in vitro BBB using the more recent cellZscope(®) device, which was traditionally performed with chopstick electrodes of voltohmmeter type (EVOM). From continuous impedance measurements, the cellZscope(®) device provides TEER (paracellular resistance) and cell membrane capacitance (Ccl-transcellular resistance), two independent measures of monolayer integrity. Additionally, this chapter provides guidance through subsequent experiments such as permeability analysis (Pe, flux), expression analysis (qRT-PCR and Western blotting), and localization analysis of BBB junction proteins (immunocytochemistry) using the same inserts subjected earlier to impedance analysis.As numerous diseases are associated with BBB breakdown, researchers aim to continuously improve and refine in vitro BBB models to mimic in vivo conditions as closely as possible. This chapter summarizes protocols with the intention to provide a collection of BBB in vitro assays that generate reproducible results not only with primary brain ECs but also with EC lines to open up the field for a broader spectrum of researchers who intend to investigate the BBB in vitro particularly aiming at therapeutic aspects.

Caveolin-1 Tyr14 phosphorylation induces interaction with TLR4 in endothelial cells and mediates MyD88-dependent signaling and sepsis-induced lung inflammation

Activation of TLR4 by the endotoxin LPS is a critical event in the pathogenesis of Gram-negative sepsis. Caveolin-1, the signaling protein associated with caveolae, is implicated in regulating the lung inflammatory response to LPS; however, the mechanism is not understood. In this study, we investigated the role of caveolin-1 in regulating TLR4 signaling in endothelial cells. We observed that LPS interaction with CD14 in endothelial cells induced Src-dependent caveolin-1 phosphorylation at Tyr(14). Using a TLR4-MD2-CD14-transfected HEK-293 cell line and caveolin-1-deficient (cav-1(-/-)) mouse lung microvascular endothelial cells, we demonstrated that caveolin-1 phosphorylation at Tyr(14) following LPS exposure induced caveolin-1 and TLR4 interaction and, thereby, TLR4 activation of MyD88, leading to NF-κB activation and generation of proinflammatory cytokines. Exogenous expression of phosphorylation-deficient Y14F caveolin-1 mutant in cav-1(-/-) mouse pulmonary vasculature rendered the mice resistant to LPS compared with reintroduction of wild-type caveolin-1. Thus, caveolin-1 Y14 phosphorylation was required for the interaction with TLR4 and activation of TLR4-MyD88 signaling and sepsis-induced lung inflammation. Inhibiting caveolin-1 Tyr(14) phosphorylation and resultant inactivation of TLR4 signaling in pulmonary vascular endothelial cells represent a novel strategy for preventing sepsis-induced lung inflammation and injury.

Endothelial progenitor cells promote directional three-dimensional endothelial network formation by secreting vascular endothelial growth factor

Endothelial progenitor cell (EPC) transplantation induces the formation of new blood-vessel networks to supply nutrients and oxygen, and is feasible for the treatment of ischemia and cardiovascular diseases. However, the role of EPCs as a source of proangiogenic cytokines and consequent generators of an extracellular growth factor microenvironment in three-dimensional (3D) microvessel formation is not fully understood. We focused on the contribution of EPCs as a source of proangiogenic cytokines on 3D microvessel formation using an in vitro 3D network model. To create a 3D network model, EPCs isolated from rat bone marrow were sandwiched with double layers of collagen gel. Endothelial cells (ECs) were then cultured on top of the upper collagen gel layer. Quantitative analyses of EC network formation revealed that the length, number, and depth of the EC networks were significantly enhanced in a 3D model with ECs and EPCs compared to an EC monoculture. In addition, conditioned medium (CM) from the 3D model with ECs and EPCs promoted network formation compared to CM from an EC monoculture. We also confirmed that EPCs secreted vascular endothelial growth factor (VEGF). However, networks cultured with the CM were shallow and did not penetrate the collagen gel in great depth. Therefore, we conclude that EPCs contribute to 3D network formation at least through indirect incorporation by generating a local VEGF gradient. These results suggest that the location of EPCs is important for controlling directional 3D network formation in the field of tissue engineering.

PECAM-1 and caveolae form the mechanosensing complex necessary for NOX2 activation and angiogenic signaling with stopped flow in pulmonary endothelium

We showed that stop of flow triggers a mechanosignaling cascade that leads to the generation of reactive oxygen species (ROS); however, a mechanosensor coupled to the cytoskeleton that could potentially transduce flow stimulus has not been identified. We showed a role for KATP channel, caveolae (caveolin-1), and NADPH oxidase 2 (NOX2) in ROS production with stop of flow. Based on reports of a mechanosensory complex that includes platelet endothelial cell adhesion molecule-1 (PECAM-1) and initiates signaling with mechanical force, we hypothesized that PECAM-1 could serve as a mechanosensor in sensing disruption of flow. Using lungs in situ, we observed that ROS production with stop of flow was significantly reduced in PECAM-1(-/-) lungs compared with lungs from wild-type (WT) mice. Lack of PECAM-1 did not affect NOX2 activation machinery or the caveolin-1 expression or caveolae number in the pulmonary endothelium. Stop of flow in vitro triggered an increase in angiogenic potential of WT pulmonary microvascular endothelial cells (PMVEC) but not of PECAM-1(-/-) PMVEC. Obstruction of flow in lungs in vivo showed that the neutrophil infiltration as observed in WT mice was significantly lowered in PECAM-1(-/-) mice. With stop of flow, WT lungs showed higher expression of the angiogenic marker VEGF compared with untreated (sham) and PECAM-1(-/-) lungs. Thus PECAM-1 (and caveolae) are parts of the mechanosensing machinery that generates superoxide with loss of shear; the resultant ROS potentially drives neutrophil influx and acts as an angiogenic signal.

Norepinephrine and adenosine-5'-triphosphate synergize in inducing IL-6 production by human dermal microvascular endothelial cells

Endothelial cells (ECs) play important roles in cutaneous inflammation, in part, by release of inflammatory chemokines/cytokines. Because dermal blood vessels are innervated by sympathetic nerves, the sympathetic neurotransmitter norepinephrine (NE) and the co-transmitter adenosine-5'-triphosphate (ATP) may regulate expression of EC inflammatory factors. We focused on IL-6 regulation because it has many inflammatory and immune functions, including participation in Th17 cell differentiation. Strikingly, NE and ATP synergistically induced release of IL-6 by a human dermal microvascular endothelial cell line (HMEC-1). Adrenergic antagonist and agonist studies indicated that the effect of NE on induced IL-6 release is primarily mediated by β2-adrenergic receptors (ARs). By real-time PCR IL-6 mRNA was also synergistically induced in HMEC-1 cells. This synergistic effect of NE and ATP was reproduced in primary human dermal endothelial cells (pHDMECs) and is also primarily mediated by β2-ARs. Under conditions of stress, activation of the symphathetic nervous system may lead to release of ATP and NE by sympathetic nerves surrounding dermal blood vessels with induction of IL-6 production by ECs. IL-6 may then participate in immune and inflammatory processes including generation of Th17 cells. Production of IL-6 in this manner might explain stress-induced exacerbation of psoriasis, and perhaps, other skin disorders involving Th17-type immunity.

Hyperglycaemia promotes cerebral barrier dysfunction through activation of protein kinase C-β

AIM

To examine whether protein kinase C (PKC) and associated downstream mechanisms are involved in hyperglycaemia (HG)-evoked blood-brain barrier (BBB) damage.

METHODS

The activities of total PKC (Peptag assay), NADPH oxidase (lucigenin assay) and matrix metalloproteinase-2 (MMP-2; gelatin zymography) were measured in human brain microvascular endothelial cells (HBMEC) exposed to normoglycaemia (5.5 mM) or HG (25 mM) using the specific assays indicated in parentheses. The integrity and function of the in vitro models of human BBB were assessed by measurements of transendothelial electrical resistance and paracellular flux of permeability markers, respectively. Occludin protein expression was studied by immunoblotting.

RESULTS

HG significantly compromised the BBB integrity and enhanced total PKC activity to which increases in PKC-β and PKC-βII isoforms contributed the most. Elevations in NADPH oxidase and MMP-2 activities and decreases in occludin levels contributed to barrier dysfunction. Selective inhibition of PKC-β isoform prevented the changes observed in occludin expression and the aforementioned enzyme activities and thus effectively preserved barrier integrity. Similarly, apocynin, a specific NADPH oxidase inhibitor, also effectively neutralized the effects of HG on barrier integrity, MMP-2 activity, occludin expression and PKC-β activity.

CONCLUSION

HG promotes cerebral-barrier dysfunction through activation of PKC-β and consequent stimulations of oxidative stress and tight junction dissolution.

Establishment of human retinal microvascular endothelial cells with extended life-span

AIM

To generate and characterize a telomerase-immortalized human retinal microvascular endothelial cell (HREC) line. This cell line may be utilized as an in vitro model to study the molecular basis of several diseases of the human retina.

MATERIALS AND METHODS

Primary retinal neuronal cells were isolated and transfected with plasmid encoding full-length human telomerase reverse transcriptase (hTERT). Transfected cells were selected and characterized to determine telomerase activity, karyotype, proliferative capacity and functionality.

RESULTS

HREC-hTERT cells appear morphologically similar to primary endothelial cells and have an extended in vitro life-span. HREC-hTERT cells express the progenitor/stem cell marker nestin. They have active telomerase and a high proliferative capacity. These cells also maintain a diploid karyotype. The HREC-hTERT cells showed high colony-formation capacity and plating efficiency compared to the primary cells. These cells are capable of differentiation into neuronal and glial cell phenotypes and the differentiated cells express the astrocyte marker glial fibrillary acidic protein (GFAP) and the neuronal marker microtubule-associated protein-2 (MAP2), respectively.

CONCLUSION

The in vitro life-span of human retinal neuronal endothelial cells can be extended by ectopic expression of hTERT without altering the genetic stability and functionality of these cells. These cells will be a valuable tool to further our understanding on the role of HRECs in the human blood-retinal-barrier and in angiogenesis and neovascularization.

Rapid formation of plasma protein corona critically affects nanoparticle pathophysiology

In biological fluids, proteins bind to the surface of nanoparticles to form a coating known as the protein corona, which can critically affect the interaction of the nanoparticles with living systems. As physiological systems are highly dynamic, it is important to obtain a time-resolved knowledge of protein-corona formation, development and biological relevancy. Here we show that label-free snapshot proteomics can be used to obtain quantitative time-resolved profiles of human plasma coronas formed on silica and polystyrene nanoparticles of various size and surface functionalization. Complex time- and nanoparticle-specific coronas, which comprise almost 300 different proteins, were found to form rapidly (<0.5 minutes) and, over time, to change significantly in terms of the amount of bound protein, but not in composition. Rapid corona formation is found to affect haemolysis, thrombocyte activation, nanoparticle uptake and endothelial cell death at an early exposure time.