SciCombinator

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Concept: Endothelium

688

As multiple spacefaring nations contemplate extended manned missions to Mars and the Moon, health risks could be elevated as travel goes beyond the Earth’s protective magnetosphere into the more intense deep space radiation environment. The primary purpose of this study was to determine whether mortality rates due to cardiovascular disease (CVD), cancer, accidents and all other causes of death differ in (1) astronauts who never flew orbital missions in space, (2) astronauts who flew only in low Earth orbit (LEO), and (3) Apollo lunar astronauts, the only humans to have traveled beyond Earth’s magnetosphere. Results show there were no differences in CVD mortality rate between non-flight (9%) and LEO (11%) astronauts. However, the CVD mortality rate among Apollo lunar astronauts (43%) was 4-5 times higher than in non-flight and LEO astronauts. To test a possible mechanistic basis for these findings, a secondary purpose was to determine the long-term effects of simulated weightlessness and space-relevant total-body irradiation on vascular responsiveness in mice. The results demonstrate that space-relevant irradiation induces a sustained vascular endothelial cell dysfunction. Such impairment is known to lead to occlusive artery disease, and may be an important risk factor for CVD among astronauts exposed to deep space radiation.

Concepts: Mortality rate, Atherosclerosis, Earth's magnetic field, Earth, Blood vessel, Moon, Endothelium, Human spaceflight

186

Here, for the first time, we test a novel hypothesis that systemic treatment of stroke with exosomes derived from multipotent mesenchymal stromal cells (MSCs) promote neurovascular remodeling and functional recovery after stroke in rats. Adult male Wistar rats were subjected to 2 hours of middle cerebral artery occlusion (MCAo) followed by tail vein injection of 100 μg protein from MSC exosome precipitates or an equal volume of vehicle phosphate-buffered saline (PBS) (n=6/group) 24 hours later. Animals were killed at 28 days after stroke and histopathology and immunohistochemistry were employed to identify neurite remodeling, neurogenesis, and angiogenesis. Systemic administration of MSC-generated exosomes significantly improved functional recovery in stroke rats compared with PBS-treated controls. Axonal density and synaptophysin-positive areas were significantly increased along the ischemic boundary zone of the cortex and striatum in MCAo rats treated with exosomes compared with PBS control. Exosome treatment significantly increased the number of newly formed doublecortin (a marker of neuroblasts) and von Willebrand factor (a marker of endothelial cells) cells. Our results suggest that intravenous administration of cell-free MSC-generated exosomes post stroke improves functional recovery and enhances neurite remodeling, neurogenesis, and angiogenesis and represents a novel treatment for stroke.Journal of Cerebral Blood Flow & Metabolism advance online publication, 21 August 2013; doi:10.1038/jcbfm.2013.152.

Concepts: Atherosclerosis, Mesenchymal stem cell, Blood vessel, Middle cerebral artery, Endothelium, Cardiovascular system, Von Willebrand factor, Von Willebrand disease

182

During embryonic development, vascular networks remodel to meet the increasing demand of growing tissues for oxygen and nutrients. This is achieved by the pruning of redundant blood vessel segments, which then allows more efficient blood flow patterns. Because of the lack of an in vivo system suitable for high-resolution live imaging, the dynamics of the pruning process have not been described in detail. Here, we present the subintestinal vein (SIV) plexus of the zebrafish embryo as a novel model to study pruning at the cellular level. We show that blood vessel regression is a coordinated process of cell rearrangements involving lumen collapse and cell-cell contact resolution. Interestingly, the cellular rearrangements during pruning resemble endothelial cell behavior during vessel fusion in a reversed order. In pruning segments, endothelial cells first migrate toward opposing sides where they join the parental vascular branches, thus remodeling the multicellular segment into a unicellular connection. Often, the lumen is maintained throughout this process, and transient unicellular tubes form through cell self-fusion. In a second step, the unicellular connection is resolved unilaterally, and the pruning cell rejoins the opposing branch. Thus, we show for the first time that various cellular activities are coordinated to achieve blood vessel pruning and define two different morphogenetic pathways, which are selected by the flow environment.

Concepts: Inflammation, Atherosclerosis, Heart, Blood vessel, Capillary, Tissues, Endothelium, Vein

177

Despite public awareness that tobacco secondhand smoke (SHS) is harmful, many people still assume that marijuana SHS is benign. Debates about whether smoke-free laws should include marijuana are becoming increasingly widespread as marijuana is legalized and the cannabis industry grows. Lack of evidence for marijuana SHS causing acute cardiovascular harm is frequently mistaken for evidence that it is harmless, despite chemical and physical similarity between marijuana and tobacco smoke. We investigated whether brief exposure to marijuana SHS causes acute vascular endothelial dysfunction.

Concepts: Smoking, Tobacco, Tobacco smoking, Law, Endothelium, Endothelial dysfunction, Cannabis, Smoke

174

Endothelial hyperpermeability induced by hyperglycemia is the initial step in the development of atherosclerosis, one of the most serious cardiovascular complications in diabetes. In the present study, we investigated the effects of resveratrol (RSV), a bioactive ingredient extracted from Chinese herb rhizoma polygonum cuspidatum, on permeability in vitro and the molecular mechanisms involved. Permeability was assessed by the efflux of fluorescein isothiocyanate (FITC)-dextran permeated through the monolayer endothelial cells (ECs). The mRNA levels, protein expressions, and secretions were measured by quantitative real-time PCR, western blot, and ELISA, respectively. Increased permeability and caveolin-1 (cav-1) expression were observed in monolayer ECs exposed to high glucose. Resveratrol treatment alleviated the hyperpermeability and the overexpression of cav-1 induced by high glucose in a dose-dependent manner. β-Cyclodextrin, a structural inhibitor of caveolae, reduced the hyperpermeability caused by high glucose. Resveratrol also down-regulated the increased expressions of vascular endothelial growth factor (VEGF) and kinase insert domain receptor (KDR, or VEGF receptor-2) induced by high glucose. Inhibition of VEGF/KDR pathway by using SU5416, a selective inhibitor of KDR, alleviated the hyperpermeability and the cav-1 overexpression induced by high glucose. The above results demonstrate that RSV ameliorates caveolae-mediated hyperpermeability induced by high glucose via VEGF/KDR pathway.

Concepts: Protein, Gene expression, Molecular biology, Signal transduction, Enzyme, Angiogenesis, Vascular endothelial growth factor, Endothelium

171

Inflammation and oxidative stress play a crucial role in angiotensin (Ang) II-mediated vascular injury. Angiotensin-converting enzyme 2 (ACE2) has recently been identified as a specific Ang II-degrading enzyme but its role in vascular biology remains elusive. We hypothesized that loss of ACE2 would facilitate Ang II-mediated vascular inflammation and peroxynitrite production. 10-week wildtype (WT, Ace2(+/y)) and ACE2 knockout (ACE2KO, Ace2(-/y)) mice received with mini-osmotic pumps with Ang II (1.5 mg.kg⁻¹.d⁻¹) or saline for 2 weeks. Aortic ACE2 protein was obviously reduced in WT mice in response to Ang II related to increases in profilin-1 protein and plasma levels of Ang II and Ang-(1-7). Loss of ACE2 resulted in greater increases in Ang II-induced mRNA expressions of inflammatory cytokines monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-1β, and IL-6 without affecting tumor necrosis factor-α in aortas of ACE2KO mice. Furthermore, ACE2 deficiency led to greater increases in Ang II-mediated profilin-1 expression, NADPH oxidase activity, and superoxide and peroxynitrite production in the aortas of ACE2KO mice associated with enhanced phosphorylated levels of Akt, p70S6 kinase, extracellular signal-regulated kinases (ERK1/2) and endothelial nitric oxide synthase (eNOS). Interestingly, daily treatment with AT1 receptor blocker irbesartan (50 mg/kg) significantly prevented Ang II-mediated aortic profilin-1 expression, inflammation, and peroxynitrite production in WT mice with enhanced ACE2 levels and the suppression of the Akt-ERK-eNOS signaling pathways. Our findings reveal that ACE2 deficiency worsens Ang II-mediated aortic inflammation and peroxynitrite production associated with the augmentation of profilin-1 expression and the activation of the Akt-ERK-eNOS signaling, suggesting potential therapeutic approaches by enhancing ACE2 action for patients with vascular diseases.

Concepts: Inflammation, Signal transduction, Adenosine triphosphate, Enzyme, Endothelium, Angiotensin II receptor antagonist, Nitric oxide, Nitric oxide synthase

170

Despite a general repression of translation under hypoxia, cells selectively upregulate a set of hypoxia-inducible genes. Results from deep sequencing revealed that Let-7 and miR-103/107 are hypoxia-responsive microRNAs (HRMs) that are strongly induced in vascular endothelial cells. In silico bioinformatics and in vitro validation showed that these HRMs are induced by HIF1α and target argonaute 1 (AGO1), which anchors the microRNA-induced silencing complex (miRISC). HRM targeting of AGO1 resulted in the translational desuppression of VEGF mRNA. Inhibition of HRM or overexpression of AGO1 without the 3' untranslated region decreased hypoxia-induced angiogenesis. Conversely, AGO1 knockdown increased angiogenesis under normoxia in vivo. In addition, data from tumor xenografts and human cancer specimens indicate that AGO1-mediated translational desuppression of VEGF may be associated with tumor angiogenesis and poor prognosis. These findings provide evidence for an angiogenic pathway involving HRMs that target AGO1 and suggest that this pathway may be a suitable target for anti- or proangiogenesis strategies.

Concepts: DNA, Gene expression, RNA, Angiogenesis, MicroRNA, In vivo, Endothelium, In vitro

170

The aim of this study was to investigate the feasibility of inducing rat neural crest cells (NCC) to differentiate to functional corneal endothelial cell (CEC)-like cells in vitro. Rat NCC were induced with adult CEC-derived conditioned medium. Immunofluorescence, flow cytometry and real time RT-PCR assay were used to detect expression of the corneal endothelium differentiation marker N-cadherin and transcription factors FoxC1 and Pitx2. CFDA SE-labeled CEC-like cells were transplanted to the corneal endothelium of a rat corneal endothelium deficiency model, and an eye-down position was maintained for 24 hours to allow cell attachment. The animals were observed for as long as 2 months after surgery and underwent clinical and histological examination. Spindle-like NCC turned to polygonal CEC-like after induction and expressed N-cadherin, FoxC1, Pitx2, zonula occludens-1 and sodium-potassium pump Na(+)/K(+) ATPase. The corneas of the experimental group were much clearer than those of the control group and the mean corneal thickness in the experimental group was significantly less than in the control group7, 14, 21 and 28 days after surgery. Confocal microscopy through focusing and histological analysis confirmed that green fluorescence-positive CEC-like cells formed a monolayer covering the Descemet’s membrane in the experimental group. In conclusion, CEC-like cells derived from NCCs displayed characters of native CEC, and the induction protocol provides guidance for future human CEC induction from NCC.

Concepts: DNA, Gene expression, Embryo, Developmental biology, Epithelium, Endothelium, Cornea, Corneal endothelium

168

Current treatments for reversible blindness caused by corneal endothelial cell failure involve replacing the failed endothelium with donor tissue using a one donor-one recipient strategy. Due to the increasing pressure of a worldwide donor cornea shortage there has been considerable interest in developing alternative strategies to treat endothelial disorders using expanded cell replacement therapy. Protocols have been developed which allow successful expansion of endothelial cells in vitro but this approach requires a supporting material that would allow easy transfer of cells to the recipient. We describe the first use of plastic compressed collagen as a highly effective, novel carrier for human corneal endothelial cells. A human corneal endothelial cell line and primary human corneal endothelial cells retained their characteristic cobblestone morphology and expression of tight junction protein ZO-1 and pump protein Na+/K+ ATPase α1 after culture on collagen constructs for up to 14 days. Additionally, ultrastructural analysis suggested a well-integrated endothelial layer with tightly opposed cells and apical microvilli. Plastic compressed collagen is a superior biomaterial in terms of its speed and ease of production and its ability to be manipulated in a clinically relevant manner without breakage. This method provides expanded endothelial cells with a substrate that could be suitable for transplantation allowing one donor cornea to potentially treat multiple patients.

Concepts: Protein, Cell, Collagen, Epithelium, Endothelium, Cornea, Corneal endothelium

168

Childhood exposure to environmental particulates increases the risk of development of asthma. The underlying mechanisms may include oxidant injury to airway epithelial cells (AEC). We investigated the ability of ambient environmental particulates to contribute to sensitization via the airways, and thus to the pathogenesis of childhood asthma. To do so, we devised a novel model in which weanling BALB/c mice were exposed to both ambient particulate pollutants and ovalbumin for sensitization via the respiratory tract, followed by chronic inhalational challenge with a low mass concentration of the antigen. We also examined whether these particulates caused oxidant injury and activation of AEC in vitro. Furthermore, we assessed the potential benefit of minimizing oxidative stress to AEC through the period of sensitization and challenge, by dietary intervention. We found that characteristic features of asthmatic inflammation developed only in animals which received particulates at the same time as respiratory sensitization, and were then chronically challenged with allergen. However, these animals did not develop airway hyper-responsiveness. Ambient particulates induced epithelial injury in vitro, with evidence of oxidative stress, and production of both pro-inflammatory cytokines and Th2-promoting cytokines such as IL-33. Treatment of AEC with an anti-oxidant in vitro inhibited the pro-inflammatory cytokine response to these particulates. Ambient particulates also induced pro-inflammatory cytokine expression following administration to weanling mice. However, early-life dietary supplementation with anti-oxidants did not prevent the development of an asthmatic inflammatory response in animals that were exposed to particulates, sensitized and challenged. We conclude that injury to airway epithelium by ambient environmental particulates in early life is capable of promoting the development of an asthmatic inflammatory response in sensitized and antigen-challenged mice. These findings are likely to be relevant to the induction of childhood asthma.

Concepts: Immune system, Inflammation, Cytokine, Asthma, Antioxidant, Interleukin, Endothelium, Respiratory epithelium