The level of circulating CD34+KDR+ endothelial progenitor cells predicts the occurrence of cardiovascular events and death from cardiovascular causes and may help to identify patients at increased cardiovascular risk.

Background-The molecular mechanisms by which physical training improves peripheral and coronary artery disease are poorly understood. Bone marrow-derived endothelial progenitor cells (EPCs) are thought to exert beneficial effects on atherosclerosis, angiogenesis, and vascular repair. Methods and Results-To study the effect of physical activity on the bone marrow, EPCs were quantified by fluorescence-activated cell sorter analysis in mice randomized to running wheels (5.1Ϯ0.8 km/d, nϭ12 to 16 per group) or no running wheel. Numbers of EPCs circulating in the peripheral blood of trained mice were enhanced to 267Ϯ19%, 289Ϯ22%, and 280Ϯ25% of control levels after 7, 14, and 28 days, respectively, accompanied by a similar increase of EPCs in the bone marrow and EPCs expanded from spleen-derived mononuclear cells. eNOS Ϫ/Ϫ mice and wild-type mice treated with N G -nitro-L-arginine methyl ester showed lower EPC numbers at baseline and a significantly attenuated increase of EPC in response to physical activity. Exercise NO dependently increased serum levels of vascular endothelial growth factor and reduced the rate of apoptosis in spleen-derived EPCs. Running inhibited neointima formation after carotid artery injury by 22Ϯ2%. Neoangiogenesis, as assessed in a subcutaneous disc model, was increased by 41Ϯ16% compared with controls. In patients with stable coronary artery disease (nϭ19), moderate exercise training for 28 days led to a significant increase in circulating EPCs and reduced EPC apoptosis. Conclusions-Physical activity increases the production and circulating numbers of EPCs via a partially NO-dependent, antiapoptotic effect that could potentially underlie exercise-related beneficial effects on cardiovascular diseases.

Abstract-Endothelial cell damage is one important pathophysiological step of atherosclerosis and restenosis after angioplasty. Accelerated reendothelialization impairs neointima formation. We evaluated the role of intravenously transfused endothelial progenitor cells (EPCs) on reendothelialization and neointima formation in a mouse model of arterial injury. 4 or transplanted stem cells 5-9 on remodeling after myocardial infarction. Special attention has been directed to endothelial progenitor cells (EPCs), a subset of BM-derived progenitor cells, which have been shown to play an important role in (patho-)physiological neoangiogenesis 1,10 -15 and vascular regeneration after myocardial infarction. 8,13,16 -18 The role of stem cells and BM-derived progenitor cells in atherosclerosis, the underlying reason for myocardial infarction and tissue damage, remains unclear. Atherosclerotic lesion formation is initiated by endothelial cell damage leading to endothelial dysfunction. Apoptosis of endothelial cells, macrophage adhesion and invasion, and smooth muscle cell migration and growth finally lead to stenosis of the targeted vessel. 19 Accelerated reendothelialization effectively impairs smooth muscle cell proliferation and neointima formation 20,21 and is therefore of special interest with regard to prevention of the early stages of atherosclerosis and restenosis after angioplasty. 22 It has been shown that the number of circulating EPCs inversely correlates with risk factors for atherosclerosis 23,24 and that risk factors such as diabetes impair the migratory capacity of EPCs. 25 Furthermore, reduced levels of EPCs are associated with endothelial dysfunction as determined by flow-mediated brachial-artery reactivity. 24 We and others have recently demonstrated that BM-derived progenitor cells significantly contribute to reendothelialization after endothelial cell injury. Mobilization of EPCs to the circulation by statins is associated with an enhanced reendothelialization and decreased neointima formation, resulting in a reduction of restenosis. 26,27 However, it could not be excluded that the demonstrated beneficial effects were exerted by statin therapy rather than EPC mobilization. To provide evidence that EPCs are involved in vascular remodeling, we evaluated the possible impact of intravenously transfused EPCs on reendothelialization and neointima formation in a mouse model of arterial injury.

AstraZeneca, Biosensors, and The Medicines Company.

Background-Repair of the endothelium after vascular injury is crucial for preserving endothelial integrity and preventing the development of vascular disease. The underlying mechanisms of endothelial cell repair are largely unknown. We sought to investigate whether endothelial microparticles (EMPs), released from apoptotic endothelial cells (ECs), influence EC repair. Methods and Results-Systemic treatment of mice with EMPs after electric denudation of the endothelium accelerated reendothelialization in vivo. In vitro experiments revealed that EMP uptake in ECs promotes EC migration and proliferation, both critical steps in endothelial repair. To dissect the underlying mechanisms, Taqman microRNA array was performed, and microRNA (miR)-126 was identified as the predominantly expressed miR in EMPs. The following experiments demonstrated that miR-126 was transported into recipient human coronary artery endothelial cells by EMPs and functionally regulated the target protein sprouty-related, EVH1 domain-containing protein 1 (SPRED1). Knockdown of miR-126 in EMPs abrogated EMP-mediated effects on human coronary artery endothelial cell migration and proliferation in vitro and reendothelialization in vivo. Interestingly, after simulating diabetic conditions, EMPs derived from glucose-treated ECs contained significantly lower amounts of miR-126 and showed reduced endothelial repair capacity in vitro and in vivo. Finally, expression analysis of miR-126 in circulating microparticles from 176 patients with stable coronary artery disease with and without diabetes mellitus revealed a significantly reduced miR-126 expression in circulating microparticles from diabetic patients. Conclusions-Endothelial

The endothelium holds a pivotal role in cardiovascular health and disease. Assessment of its function was until recently limited to experimental designs due to its location. The advent of novel techniques has facilitated testing on a more detailed basis, with focus on distinct pathways. This review presents available in-vivo and ex-vivo methods for evaluating endothelial function with special focus on more recent ones. The diagnostic modalities covered include assessment of epicardial and microvascular coronary endothelial function, local vasodilation by venous occlusion plethysmography and flow-mediated dilatation, arterial pulse wave analysis and pulse amplitude tonometry, microvascular blood flow by laser Doppler flowmetry, biochemical markers and bioassays, measurement of endothelial-derived microparticles and progenitor cells, and glycocalyx measurements. Insights and practical information on the theoretical basis, methodological aspects, and clinical application in various disease states are discussed. The ability of these methods to detect endothelial dysfunction before overt cardiovascular disease manifests make them attractive clinical tools for prevention and rehabilitation. METHODS FOR EVALUATING ENDOTHELIAL FUNCTION. A POSITION STATEMENT FROM THE EUROPEAN SOCIETY OF CARDI-OLOGY WORKING GROUP ON PERIPHERAL CIRCULATION. John Venous occlusion plethysmographyVenous occlusion plethysmography (VOP), established more than 100 years ago, is the longest living method for investigating blood flow in humans. Flow-mediated dilatationConduit vessels respond to alterations in blood flow by increasing vessel diameter via an endothelial dependent mechanism. 20,21 The flow-mediated dilatation (FMD)technique measures changes in conduit artery diameter by ultrasound. This response has been shown to reflect local bioactivity of endothelial-derived NO. 22 MethodologyThe brachial artery is most often imaged (online Supplemental Figure 2). FMD studies are performed in a quiet temperature controlled room while subjects are lying supine for >10 min prior to image acquisition. A straight, non-branching segment of the brachial artery above the antecubital fossa is imaged in the longitudinal plane with the ultrasound probe securely fixed using a stereotactic clamp. This permits fine adjustments in the coronal and sagittal planes. A blood pressure cuff is placed 1-2 cm below the antecubital fossa and inflated to supra-systolic pressure. 23 After cuff release, reactive hyperaemia results and is quantified using Doppler. The arterial diameter is recorded at end diastole using electrocardiographic gating during image acquisition, to determine the response of the conduit artery to increase in flow. 24 Changes in the arterial diameter are assessed using commercial digital edge detection software. Pulse wave analysisThe arterial waveform contains important information about the stiffness of the large arteries and amount of wave reflection within the arterial system. 32 Wave reflection occurs at sites of impedance mismatc...

Intracoronary administration of BMCs is associated with a significant reduction of the occurrence of major adverse cardiovascular events after AMI. Large-scale studies are warranted to confirm the effects of BMC administration on mortality and morbidity in patients with AMIs.

Objective-Atherosclerosis and restenosis after vascular injury are both characterized by endothelial dysfunction, apoptosis, inappropriate endothelialization, and neointimal formation. Bone marrow-derived endothelial progenitor cells have been implicated in neovascularization, resulting in adult blood vessel formation. Despite the anticipated stem cell plasticity, the role of bone marrow-derived endothelial progenitor cells has not been clarified in vascular lesion development. Methods and Results-We