Arterial endothelial cells: still the craftsmen of regenerated endothelium

For more than a decade, a prevailing hypothesis in research related to arterial disease has been that circulating endothelial progenitor cells (EPCs) provide protection by their innate ability to replace dysfunctional or damaged endothelium. This paradigm has led to extensive investigation of EPCs in the hope of finding therapeutic targets to control their homing and differentiation. However, from the very beginning, the nomenclature and the phenotype of EPCs have been subject to controversy and there are currently no specific markers that can unambiguously identify these cells. Moreover, many of the initial observations that EPCs differentiate to endothelial cells in the course of arterial disease have been criticized for methodological problems. The present review discusses the contrasting experimental evidence as to the role of EPCs in contributing to relining of the endothelium and highlights some of the methodological pitfalls and terminological ambiguities that confuse the field.postprin

Inducing persistent flow disturbances accelerates atherogenesis and promotes thin cap fibroatheroma development in D374Y-PCSK9 hypercholesterolemic minipigs

BACKGROUND: -Although disturbed flow is thought to play a central role in the development of advanced coronary atherosclerotic plaques, no causal relationship has been established. We evaluated whether inducing disturbed flow would cause the development of advanced coronary plaques, including thin cap fibroatheroma (TCFA). METHODS AND RESULTS: -D374Y-PCSK9 hypercholesterolemic minipigs (N=5) were instrumented with an intracoronary shear-modifying stent (SMS). Frequency-domain optical coherence tomography was obtained at baseline, immediately post-stent, 19, and 34 weeks and used to compute shear stress metrics of disturbed flow. At 34 weeks, plaque type was assessed within serially-collected histological sections and co-registered to the distribution of each shear metric. The SMS caused a flow-limiting stenosis and blood flow exiting the SMS caused regions of increased shear stress on the outer curvature and large regions of low and multidirectional shear stress on the inner curvature of the vessel. As a result, plaque burden was ~3-fold higher downstream of the SMS compared to both upstream of the SMS and in the control artery (p<0.001). Advanced plaques were also primarily observed downstream of the SMS, in locations initially exposed to both low (p<0.002) and multidirectional (p<0.002) shear stress. TCFA regions demonstrated significantly lower shear stress that persisted over the duration of the study compared to other plaque types (p<0.005). CONCLUSIONS: -These data support a causal role for lowered and multidirectional shear stress in the initiation of advanced coronary atherosclerotic plaques. Persistently lowered shear stress appears to be the principal flow disturbance needed for the formation of TCFA

Moderate beer consumption does not change early or mature atherosclerosis in mice

BACKGROUND: Although the consumption of wine in particular has been associated with a lower risk of atherothrombotic cardiovascular disease, systematic reviews differ as to the relative protective effect of beer, wine and spirits. Two previous studies showed that red wine reduces fatty streak formation (early atherosclerosis) but not mature atherosclerosis in apolipoprotein (apo) E-deficient (apoE-/-) mice. AIM OF THE STUDY: To determine whether a moderate beer intake would affect early and mature atherosclerotic lesion formation using control C57BL/6 and apoE-/- mice, respectively, as models. METHODS: Control C57BL/6 and apoE-/- mice were randomized to receive either water, ethanol, mild beer, dark beer or ethanol-free beer. The level of beer was designed to approximate the alcohol intake currently believed to be beneficial in reducing human vascular risk. Control C57BL/6 mice were fed a Western diet for 24 weeks, and apoE-/- mice a chow diet for 12 weeks. At the end of the trial period, mice were euthanized and atherosclerotic lesions quantified. Plasma lipid concentrations were also measured. RESULTS: The amount of atherosclerosis and average number of lesions in the proximal aortic region did not differ among groups in control C57BL/6 mice (p = 0.32 and p = 0.29, respectively) and apoE-/- mice (p = 0.19 and p = 0.59, respectively). No consistent differences were observed in plasma lipid and lipoprotein concentrations among water, ethanol and beer groups. CONCLUSIONS: Moderate beer consumption does not change the development of early or mature atherosclerosis in mice. Our findings do not support the hypothesis of an anti-atherogenic effect of beer. Other potential protective actions of moderate beer consumption such as plaque stabilization, a reduction in plaque intrinsic thrombogenicity, or a reduction in the systemic propensity to thrombosis, remain to be studied

Contribution of Recipient-Derived Cells in Allograft Neointima Formation and the Response to Stent Implantation

Allograft coronary disease is the dominant cause of increased risk of death after cardiac transplantation. While the percutaneous insertion of stents is the most efficacious revascularization strategy for allograft coronary disease there is a high incidence of stent renarrowing. We developed a novel rabbit model of sex-mismatched allograft vascular disease as well as the response to stent implantation. In situ hybridization for the Y-chromosome was employed to detect male cells in the neointima of stented allograft, and the population of recipient derived neointimal cells was measured by quantitative polymerase chain reaction and characterized by immunohistochemistry. To demonstrate the participation of circulatory derived cells in stent neointima formation we infused ex vivo labeled peripheral blood mononuclear cells into native rabbit carotid arteries immediately after stenting. Fourteen days after stenting the neointima area was 58% greater in the stented vs. non-stented allograft segments (p = 0.02). Male cells were detected in the neointima of stented female-to-male allografts. Recipient-derived cells constituted 72.1±5.7% and 81.5±4.2% of neointimal cell population in the non-stented and stented segments, respectively and the corresponding proliferation rates were only 2.7±0.5% and 2.3±0.2%. Some of the recipient-derived neointimal cells were of endothelial lineage. The ex vivo tagged cells constituted 9.0±0.4% of the cells per high power field in the stent neointima 14 days after stenting. These experiments provide important quantitative data regarding the degree to which host-derived blood-borne cells contribute to neointima formation in allograft vasculopathy and the early response to stent implantation

Nanomedical Theranostics in Cardiovascular Disease

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. New diagnostic and therapeutic strategies are needed to mitigate this public health issue. Advances in nanotechnology have generated innovative strategies for diagnosis and therapy in a variety of diseases, foremost in cancer. Based on these studies, a novel concept referred to as nanomedical theranostics, or the combinatory application of nanoparticulate agents to allow diagnostic therapy, is being explored to enable image-guided, personalized, or targeted treatment. Preclinically, theranostics have been gradually applied to CVD with several interesting and encouraging findings. This article summarizes studies and challenges of nanotheranostic strategies in CVD. It also evaluates nanotheranostic strategies that may potentially be utilized to benefit patients

LDL-Induced Impairment of Human Vascular Smooth Muscle Cells Repair Function Is Reversed by HMG-CoA Reductase Inhibition

Growing human atherosclerotic plaques show a progressive loss of vascular smooth muscle cells (VSMC) becoming soft and vulnerable. Lipid loaded-VSMC show impaired vascular repair function and motility due to changes in cytoskeleton proteins involved in cell-migration. Clinical benefits of statins reducing coronary events have been related to repopulation of vulnerable plaques with VSMC. Here, we investigated whether HMG-CoA reductase inhibition with rosuvastatin can reverse the effects induced by atherogenic concentrations of LDL either in the native (nLDL) form or modified by aggregation (agLDL) on human VSMC motility. Using a model of wound repair, we showed that treatment of human coronary VSMC with rosuvastatin significantly prevented (and reversed) the inhibitory effect of nLDL and agLDL in the repair of the cell depleted areas. In addition, rosuvastatin significantly abolished the agLDL-induced dephosphorylation of myosin regulatory light chain as demonstrated by 2DE-electrophoresis and mass spectrometry. Besides, confocal microscopy showed that rosuvastatin enhances actin-cytoskeleton reorganization during lipid-loaded-VSMC attachment and spreading. The effects of rosuvastatin on actin-cytoskeleton dynamics and cell migration were dependent on ROCK-signalling. Furthermore, rosuvastatin caused a significant increase in RhoA-GTP in the cytosol of VSMC. Taken together, our study demonstrated that inhibition of HMG-CoA reductase restores the migratory capacity and repair function of VSMC that is impaired by native and aggregated LDL. This mechanism may contribute to the stabilization of lipid-rich atherosclerotic plaques afforded by statins

Plasma Cholesterol-Induced Lesion Networks Activated before Regression of Early, Mature, and Advanced Atherosclerosis

Plasma cholesterol lowering (PCL) slows and sometimes prevents progression of atherosclerosis and may even lead to regression. Little is known about how molecular processes in the atherosclerotic arterial wall respond to PCL and modify responses to atherosclerosis regression. We studied atherosclerosis regression and global gene expression responses to PCL (&gt;= 80%) and to atherosclerosis regression itself in early, mature, and advanced lesions. In atherosclerotic aortic wall from Ldlr(-/-)Apob(100/100)Mttp(flox/flox)Mx1-Cre mice, atherosclerosis regressed after PCL regardless of lesion stage. However, near-complete regression was observed only in mice with early lesions; mice with mature and advanced lesions were left with regression-resistant, relatively unstable plaque remnants. Atherosclerosis genes responding to PCL before regression, unlike those responding to the regression itself, were enriched in inherited risk for coronary artery disease and myocardial infarction, indicating causality. Inference of transcription factor (TF) regulatory networks of these PCL-responsive gene sets revealed largely different networks in early, mature, and advanced lesions. In early lesions, PPARG was identified as a specific master regulator of the PCL-responsive atherosclerosis TF-regulatory network, whereas in mature and advanced lesions, the specific master regulators were MLL5 and SRSF10/XRN2, respectively. In a THP-1 foam cell model of atherosclerosis regression, siRNA targeting of these master regulators activated the time-point-specific TF-regulatory networks and altered the accumulation of cholesterol esters. We conclude that PCL leads to complete atherosclerosis regression only in mice with early lesions. Identified master regulators and related PCL-responsive TF-regulatory networks will be interesting targets to enhance PCL-mediated regression of mature and advanced atherosclerotic lesions. Author Summary The main underlying cause of heart attacks and strokes is atherosclerosis. One strategy to prevent these often deadly clinical events is therefore either to slow atherosclerosis progression or better, induce regression of atherosclerotic plaques making them more stable. Plasma cholesterol lowering (PCL) is the most efficient way to induce atherosclerosis regression but sometimes fails to do so. In our study, we used a mouse model with elevated LDL cholesterol levels, similar to humans who develop early atherosclerosis, and a genetic switch to lower plasma cholesterol at any time during atherosclerosis progression. In this model, we examined atherosclerosis gene expression and regression in response to PCL at three different stages of atherosclerosis progression. PCL led to complete regression in mice with early lesions but was incomplete in mice with mature and advanced lesions, indicating that early prevention with PCL in individuals with increased risk for heart attack or stroke would be particularly useful. In addition, by inferring PCL-responsive gene networks in early, mature and advanced atherosclerotic lesions, we identified key drivers specific for regression of early (PPARG), mature (MLL5) and advanced (SRSF10/XRN2) atherosclerosis. These key drivers should be interesting therapeutic targets to enhance PCL-mediated regression of atherosclerosis