Endothelial Progenitors as Tools to Study Vascular Disease

Endothelial progenitor cells (EPCs) have great clinical value because they can be used as diagnostic biomarkers and as a cellular therapy for promoting vascular repair of ischaemic tissues. However, EPCs also have an additional research value in vascular disease modelling to interrogate human disease mechanisms. The term EPC is used to describe a diverse variety of cells, and we have identified a specific EPC subtype called outgrowth endothelial cell (OEC) as the best candidate for vascular disease modelling because of its high-proliferative potential and unambiguous endothelial commitment. OECs are isolated from human blood and can be exposed to pathologic conditions (forward approach) or be isolated from patients (reverse approach) in order to study vascular human disease. The use of OECs for modelling vascular disease will contribute greatly to improving our understanding of endothelial pathogenesis, which will potentially lead to the discovery of novel therapeutic strategies for vascular diseases.

INTRAVASCULAR ANTI-IGE CHALLENGE IN PERFUSED LUNGS - MEDIATOR RELEASE AND VASCULAR PRESSOR-RESPONSE

Intravascular application of goat anti-rabbit immunoglobulin E (IgE) was used to stimulate parenchymal mast cells in situ in perfused rabbit lungs. Sustained pulmonary arterial pressure rise was evoked in the absence of lung vascular permeability increase and lung edema formation. Early prostaglandin (PG) D2 and histamine release into the perfusate was documented, accompanied by more sustained liberation of cysteinyl leukotrienes (LT), LTB4, and PGI2. The quantities of these inflammatory mediators displayed the following order: histamine > cysteinyl-LT > PGI2 > LTB4 > PGD2. Pressor response and inflammatory mediator release revealed corresponding bell-shaped dose dependencies. Cyclooxygenase inhibition (acetylsalicylic acid) suppressed prostanoid generation, increased LT release, and did not substantially affect pressor response and histamine liberation. BW755 C, a cyclo- and lipoxygenase inhibitor, blocked the release of cysteinyl-LT and markedly reduced the liberation of the other inflammatory mediators as well as the pressor response. The H-1-antagonist clemastine caused a moderate reduction of the anti-IgE-provoked pressure rise. We conclude that intravascular anti-IgE challenge in intact lungs provokes the release of an inflammatory mediator profile compatible with in situ lung parenchymal mast cell activation. Pulmonary hypertension represents the predominant vascular response, presumably mediated by cysteinyl-LT and, to a minor extent, histamine liberation.

Therapeutic revascularisation of ischaemic tissue. The opportunities and challenges for therapy using vascular stem/ progenitor cells

Ischaemia-related diseases such as peripheral artery disease and coronary heart disease constitute a major issue in medicine as they affect millions of individuals each year and represent a considerable economic burden to healthcare systems. If the underlying ischaemia is not sufficiently resolved it can lead to tissue damage, with subsequent cell death. Treating such diseases remains difficult and several strategies have been used to stimulate the growth of blood vessels and promote regeneration of ischaemic tissues, such as the use of recombinant proteins and gene therapy. Although these approaches remain promising, they have limitations and results from clinical trials using these methods have had limited success. Recently, there has been growing interest in the therapeutic potential of using a cell-based approach to treat vasodegenerative disorders. In vascular medicine, various stem cells and adult progenitors have been highlighted as having a vasoreparative role in ischaemic tissues. This review will examine the clinical potential of several stem and progenitor cells that may be utilised to regenerate defunct or damaged vasculature and restore blood flow to the ischaemic tissue. In particular, we focus on the therapeutic potential of endothelial progenitor cells as an exciting new option for the treatment of ischaemic diseases. © 2012 BioMed Central Ltd

Glucose-induced oxidative stress in vascular contractile cells - Comparison of aortic smooth muscle cells and retinal pericytes

Free radical-mediated damage to vascular cells may be involved in the pathogenesis of diabetic vasculopathy. The aim of this study was to compare the extent of glucose-induced oxidative stress in both vascular smooth muscle cells (VSMCs) and pericytes and the effect on antioxidant enzyme gene expression and activities. Porcine aortic VSMC and retinal pericytes were cultured in either 5 or 25 mmol/l glucose for 10 days. Intracellular malondialdehyde (MDA) was measured as a marker of peroxidative damage, and mRNA expression of CuZn-SOD, MnSOD, catalase, and glutathione peroxidase (GPX) were measured by Northern analysis. Glutathione (GSH) was also measured. There was a significant increase in MDA in VSMCs in 25 mmol/l glucose (1.34 +/- 0.11 vs. 1.88 +/- 0.24 nmol/mg protein, 5 vs. 25 mmol/l D-glucose, mean +/- SE, n = 15, P

eNOS overexpression exacerbates vascular closure in the obliterative phase of OIR and increases angiogenic drive in the subsequent proliferative stage

Purpose: In ischemic retinopathies, the misdirection of reparative angiogenesis away from the hypoxic retina leads to pathologic neovascularization. Thus, therapeutic strategies that reverse this trend would be extremely beneficial. Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) is an important mediator of vascular endothelial growth factor (VEGF) function facilitating vascular growth and maturation. However, in addition to NO, eNOS can also produce superoxide (O), exacerbating pathology. Here, our aim was to investigate the effect of eNOS overexpression on vascular closure and subsequent recovery of the ischemic retina.

Methods: Mice overexpressing eNOS-GFP were subjected to oxygen-induced retinopathy (OIR) and changes in retinal vascularization quantified. Background angiogenic drive was assessed during vascular development and in aortic rings. NOS activity was measured by Griess assay or conversion of radiolabeled arginine to citrulline, nitrotyrosine (NT), and superoxide by immunolabeling and dihydroethidium fluorescence and VEGF by ELISA.

Results: In response to hyperoxia, enhanced eNOS expression led to increased NOS-derived superoxide and dysfunctional NO production, NT accumulation, and exacerbated vessel closure associated with tetrahydrobiopterin (BH) insufficiency. Despite worse vaso-obliteration, eNOS overexpression resulted in elevated hypoxia-induced angiogenic drive, independent of VEGF production. This correlated with increased vascular branching similar to that observed in isolated aortas and during development. Enhanced recovery was also associated with neovascular tuft formation, which showed defective NO production and increased eNOS-derived superoxide and NT levels.

Conclusions: In hyperoxia, reduced BH bioavailability causes overexpressed eNOS to become dysfunctional, exacerbating vaso-obliteration. In the proliferative phase, however, eNOS has important prorepair functions enhancing angiogenic growth potential and recovery in ischemia. © 2012 The Association for Research in Vision and Ophthalmology, Inc.

Mitigation of Fatigue Damage in Self-Healing Vascular Materials

The fatigue response of an epoxy matrix containing vasculature for the delivery of liquid healing agents is investigated. The release of a rapidly curing, two-part epoxy healing chemistry into the wake of a propagating crack reduces the rate of crack extension by shielding the crack tip from the full range of applied stress intensity factor. Crack propagation is studied for a variety of loading conditions, with the maximum applied stress intensity factor ranging from 62 to 84% of the quasi-static fracture toughness of the material. At the highest level of applied load, the rate of mechanical damage is so fast that the healing agents do not fully mix and polymerize, and the effect of healing is minimal. The self-healing response is most effective at impeding the slower propagating cracks, with complete crack arrest occurring at the lowest level of applied load, and reductions of 79–84% in the rate of crack extension at intermediate loads.

Oxidative-nitrosative stress and systemic vascular function in highlanders with and without exaggerated hypoxemia

ABSTRACT BACKGROUND: Acute exposure to high-altitude stimulates free radical formation in lowlanders yet whether this persists during chronic exposure in healthy well-adapted and maladapted highlanders suffering from chronic mountain sickness (CMS) remains to be established. METHODS: Oxidative-nitrosative stress [ascorbate radical (A•-), electron paramagnetic resonance spectroscopy and nitrite (NO2-), ozone-based chemiluminescence] was assessed in venous blood of 25 male highlanders living at 3,600 m with (n = 13, CMS+) and without (n = 12, CMS-) CMS. Twelve age and activity-matched healthy male lowlanders were examined at sea-level and during acute hypoxia. We also measured flow-mediated dilatation (FMD), arterial stiffness (AIx-75) and carotid intima-media thickness (IMT). RESULTS: Compared to normoxic lowlanders, oxidative-nitrosative stress was moderately increased in CMS- (P < 0.05) as indicated by elevated A•- (3,191 ± 457 vs. 2,640 ± 445 arbitrary units (AU)] and lower NO2- (206 ± 55 vs. 420 ± 128 nmol/L) whereas vascular function remained preserved. This was comparable to that observed during acute hypoxia in lowlanders in whom vascular dysfunction is typically observed. In contrast, this response was markedly exaggerated in CMS+ (A•-: 3,765 ± 429 AU and NO2- : 148 ± 50 nmol/L) compared to both CMS- and lowlanders (P < 0.05). This was associated with systemic vascular dysfunction as indicated by lower (P < 0.05 vs. CMS-) FMD (4.2 ± 0.7 vs. 7.6 ± 1.7 %) and increased AIx-75 (23 ± 8 vs. 12 ± 7 %) and carotid IMT (714 ± 127 vs. 588 ± 94 µM). CONCLUSIONS: Healthy highlanders display a moderate sustained elevation in oxidative-nitrosative stress that unlike the equivalent increase evoked by acute hypoxia in healthy lowlanders, failed to affect vascular function. Its more marked elevation in patients with CMS may contribute to systemic vascular dysfunction.Clinical Trials Gov Registration # NCT011827921Neurovascular Research Laboratory, Faculty of Health, Science and Sport, University of Glamorgan, Wales, UK;2Sondes Moléculaires en Biologie et Stress Oxydant, Institut de Chimie Radicalaire, CNRS UMR 7273, Aix-Marseille University, France;3Department of Cardiology, University Hospital of Bern, Bern, Switzerland;4Institute of Clinical Physiology, CNR, Pisa, Italy;5Instituto Bolivano de Biologia de Altura, La Paz, Bolivia;6Centre for Clinical and Population Sciences, Queen's University Belfast, Belfast, Northern Ireland,7Botnar Center for Clinical Research, Hirslanden Group, Lausanne, Switzerland;8Facultad de Ciencias, Departamento de Biología, Universidad de Tarapacá, Arica, Chile and9Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland*Drs Bailey, Rimoldi, Scherrer and Sartori contributed equally to this workCorrespondence: Damian Miles Bailey, Neurovascular Research Laboratory, Faculty of Health, Science and Sport, University of Glamorgan, UK CF37 4AT email: dbailey1@glam.ac.uk.

Cognitive, global, and functional benefits of donepezil in Alzheimer's disease and vascular dementia:results from large-scale clinical trials

Alzheimer's disease (AD) and vascular dementia (VaD) are both associated with deficits in cholinergic neurotransmission that are amenable to therapeutic intervention. The cholinesterase inhibitor, donepezil, is clinically effective in both AD and VaD. Results from a 10-study metaanalysis of donepezil (5 or 10 mg/day) in AD and a two-study combined analysis of donepezil (5 or 10 mg/day) in VaD are presented to compare patient characteristics and donepezil treatment outcomes. The analyzed studies were randomized, placebo-controlled, and of up to 24 weeks duration. In both AD and VaD, donepezil provided significant benefits compared with placebo on measures of cognition and global function. Placebo-treated AD patients showed a decline in cognition and global function, whereas placebo-treated VaD patients remained stable, suggesting treatment effects of donepezil in VaD were driven by improvement rather than stabilization or reduced decline. More VaD patients than AD patients received concomitant medications. Cardiovascular adverse events were more common in VaD than AD patients but were not increased by donepezil. In conclusion, although there are differences between AD and VaD patients in comorbid conditions and concomitant medications, donepezil is effective and well tolerated in both types of dementia.

Moderately elevated plasma homocysteine, methylenetetrahydrofolate reductase genotype, and risk for stroke, vascular dementia, and Alzheimer disease in Northern Ireland

Elevated plasma homocysteine level has been associated with increased risk for cardiovascular and cerebrovascular disease. Variation in the levels of this amino acid has been shown to be due to nutritional status and methylenetetrahydrofolate reductase (MTHFR) genotype.