Plaque angiogenesis and atherosclerosis

Impact of statin therapy on CD40:CD40L signaling: mechanistic insights and therapeutic opportunities

Statins are widely utilized to reduce cholesterol levels, particularly in cardiovascular diseases. They interface with cholesterol synthesis by inhibiting the 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase enzyme. Besides their primary effect, statins demonstrate anti-inflammatory and immune-modulating properties in various diseases, highlighting the pleiotropic effect of these drugs. The CD40:CD40L signaling pathway is considered a prominent inflammatory pathway in multiple diseases, including autoimmune, inflammatory, and cardiovascular diseases. The findings from clinical trials and in vitro and in vivo studies suggest the potential anti-inflammatory effect of statins in modulating the CD40 signaling pathway and downstream inflammatory mediator. Accordingly, as its classic ligand, statins can suppress immune responses in autoimmune diseases by inhibiting CD40 expression and blocking its interaction with CD40L. Additionally, statins affect intracellular signaling and inhibit inflammatory mediator secretion in chronic inflammatory diseases like asthma and autoimmune disorders such as myasthenia gravis, multiple sclerosis, systemic lupus erymanthus, and cardiovascular diseases like atherosclerosis. However, it is essential to note that the anti-inflammatory effect of statins may vary depending on the specific type of statin used. In this study, we aim to explore the potential anti-inflammatory effects of statins in treating inflammatory diseases by examining their role in regulating immune responses, particularly their impact on the CD40:CD40L signaling pathway, through a comprehensive review of existing literature.

Protocatechuic aldehyde increases pericyte coverage and mitigates pericyte damage to enhance the atherosclerotic plaque stability

Pericyte dysfunction and loss contribute substantially to the destabilization and rupture of atherosclerotic plaques. Protocatechuic aldehyde (PCAD), a natural polyphenol, exerts anti-atherosclerotic effects. However, the effects and mechanisms of this polyphenol on pericyte recruitment, coverage, and pericyte function remain unknown. We here treated apolipoprotein E-deficient mice having high-fat diet-induced atherosclerosis with PCAD. PCAD achieved therapeutic effects similar to rosuvastatin in lowering lipid levels and thus preventing atherosclerosis progression. With PCAD administration, plaque phenotype exhibited higher stability with markedly reduced lesion vulnerability, which is characterized by reduced lipid content and macrophage accumulation, and a consequent increase in collagen deposition. PCAD therapy increased pericyte coverage in the plaques, reduced VEGF-A production, and inhibited intraplaque neovascularization. PCAD promoted pericyte proliferation, adhesion, and migration to mitigate ox-LDL-induced pericyte dysfunction, which thus maintained the capillary network structure and stability. Furthermore, TGFBR1 silencing partially reversed the protective effect exerted by PCAD on human microvascular pericytes. PCAD increased pericyte coverage and impeded ox-LDL-induced damages through TGF-β1/TGFBR1/Smad2/3 signaling. All these novel findings indicated that PCAD increases pericyte coverage and alleviates pericyte damage to improve the stability of atherosclerotic plaques, which is accomplished by regulating TGF-β1/TGFBR1/Smad2/3 signaling in pericytes.

The (pro)renin receptor as a pharmacological target in cardiorenal diseaes

The (pro)renin receptor ((P)RR) is not only a member of the renin-angiotensin system (RAS) but also exerts several RAS-independent functions due to its multiple signal transductions pathways. In this mini-review, we shortly discuss the molecular functions of this receptor and its pathophysiological significance with a focus on cardiorenal diseases. Finally, we provide a short summary regarding a drug discovery and drug development program on small molecule-based renin/ prorenin receptor blockers (RERBs).

Vessel wall MR imaging of aortic arch, cervical carotid and intracranial arteries in patients with embolic stroke of undetermined source: A narrative review

Despite advancements in multi-modal imaging techniques, a substantial portion of ischemic stroke patients today remain without a diagnosed etiology after conventional workup. Based on existing diagnostic criteria, these ischemic stroke patients are subcategorized into having cryptogenic stroke (CS) or embolic stroke of undetermined source (ESUS). There is growing evidence that in these patients, non-cardiogenic embolic sources, in particular non-stenosing atherosclerotic plaque, may have significant contributory roles in their ischemic strokes. Recent advancements in vessel wall MRI (VW-MRI) have enabled imaging of vessel walls beyond the degree of luminal stenosis, and allows further characterization of atherosclerotic plaque components. Using this imaging technique, we are able to identify potential imaging biomarkers of vulnerable atherosclerotic plaques such as intraplaque hemorrhage, lipid rich necrotic core, and thin or ruptured fibrous caps. This review focuses on the existing evidence on the advantages of utilizing VW-MRI in ischemic stroke patients to identify culprit plaques in key anatomical areas, namely the cervical carotid arteries, intracranial arteries, and the aortic arch. For each anatomical area, the literature on potential imaging biomarkers of vulnerable plaques on VW-MRI as well as the VW-MRI literature in ESUS and CS patients are reviewed. Future directions on further elucidating ESUS and CS by the use of VW-MRI as well as exciting emerging techniques are reviewed.

Tumors resurrect an embryonic vascular program to escape immunity

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Assessment of Therapeutic Response to Statin Therapy in Patients With Intracranial or Extracranial Carotid Atherosclerosis by Vessel Wall MRI: A Systematic Review and Updated Meta-Analysis

Background and Aims: Statin therapy is an essential component of cardiovascular preventive care. In recent years, various vessel wall MRI (VW-MRI) techniques have been used to monitor atherosclerosis progression or regression in patients with extracranial or intracranial large-artery atherosclerosis. We aimed to perform a systematic review and meta-analysis on the effects of statin therapy on plaque evolution as assessed by VW-MRI.

Materials and Methods: Prospective studies investigating carotid and intracranial atherosclerotic plaques in patients on statin therapy monitored by serial VW-MRI were systematically identified in the literature. The plaque burden and lipid-rich necrotic core (LRNC) volume of carotid plaque and the imaging features of intracranial plaques were extracted and summarized. For studies investigating carotid artery wall volume and LRNC volume, combined estimates were derived by meta-analysis.

Results: The study identified 21 studies of carotid plaque and two studies of intracranial plaque. While 16 studies investigating carotid plaques that included 780 patients by High-resolution VW-MRI were included in the meta-analysis. There was no significant change in carotid wall volume from baseline to 12 months. A significant change in LRNC volume was observed at > 12 months compared with baseline (Effect = −10.69, 95% CI = −19.11, −2.28, P < 0.01), while no significant change in LRNC volume at 3–6 months or 7–12 months after statin therapy initiation in 6 studies. Increases in fibrous tissue and calcium and reduction in neovascularization density of the plaque were seen in 2/3 studies (including 48/59 patients), 1/3 studies (including 17/54 patients), and 2/2 studies (including 71 patients) after statin therapy, respectively. Two studies with 257 patients in intracranial atherosclerosis showed that statins could effectively decrease wall volume and plaque enhancement volume.

Conclusions: Collective data indicated that statins could potentially stabilize carotid plaques by significantly reducing LRNC with 1 year of therapy as shown on serial carotid VW-MRI. There was no significant decrease in wall volume, which nonetheless indicated that plaque composition changes might be more sensitive to response monitoring than wall volume. It is likely that more sensitive, clinically relevant, and preferably quantitative indicators of therapeutic effects on intracranial vessel plaque morphology will be developed in the future.

The Effects of Atorvastatin on Global Cerebral Ischemia-Induced Neuronal Death

(1) Background and Purpose: Global cerebral ischemia-induced severe hypoxic brain damage is one of the main causes of mortality and long-term neurologic disability even after receiving early blood reperfusion. This study aimed to test the hypothesis that atorvastatin potentially has neuroprotective effects in global cerebral ischemia (GCI). (2) Methods: We performed two sets of experiments, analyzing acute (1-week) and chronic (4-week) treatments. For the vehicle (Veh) and statin treatments, 1 mL of 0.9% saline and 5 mg/kg of atorvastatin (ATOR) were administered orally. For histological analysis, we used the following staining protocols: Fluoro-Jade B and NeuN, 4-hydroxynonenal, CD11b and GFAP, IgG, SMI71, and vWF. Finally, we evaluated the cognitive function with a battery of behavioral tests. (3) Results: The GCI-ATOR group showed significantly reduced neuronal death, oxidative stress, inflammation, and BBB disruption compared with the GCI-Veh group. Moreover, the GCI-ATOR group showed decreased endothelial damage and VV proliferation and had significantly improved cognitive function compared with the GCI-Veh group in both models. (4) Conclusions: ATOR has neuroprotective effects and helps recover the cognitive function after GCI in rats. Therefore, administration of atorvastatin may be a therapeutic option in managing GCI after CA.

Functional lncRNA-miRNA-mRNA networks in rabbit carotid atherosclerosis

Atherosclerosis is one of the most common clinical cardiovascular disorders. Accumulating evidence indicates that lncRNAs exert critical functions in atherosclerosis; however, their functional roles and regulatory mechanisms remain unclear. In this study, we induced atherosclerotic plaques in three rabbit carotid arteries through an atherogenic diet and balloon injury; three age-matched rabbits were fed normal chow and served as controls. We thoroughly investigated the RNA (mRNA, lncRNA and miRNA) expression profiles in atherosclerotic rabbit carotid models with deep RNA sequencing. We identified several significantly differentially expressed RNAs. The corresponding lncRNA-miRNA-mRNA network was constructed, and the significantly dysregulated network was selected. Furthermore, Gene Ontology and  Kyoto Encyclopedia of Genes and Genomes analyses indicated that the mRNAs in the network were involved in leukocyte activation, cell proliferation, cell adhesion molecules and cytokine-cytokine receptor interaction. After rigorous screening, we obtained a differentially expressed lncRNA-miRNA-mRNA interaction network associated with atherosclerosis. In the network, XLOC_054118 and XLOC_030217 upregulate the CHI3L1, SOAT, CTSB and CAPG genes by competitively binding to the miRNA ocu-miR-96-5p. XLOC_062719 and XLOC_063297 upregulate CTSS, CTSB and EDNRA genes by competitively binding to the miRNA ocu-miR-185-5p.

Plasma Placental Growth Factor Concentrations Are Elevated Well in Advance of Type 2 Diabetes Mellitus Onset: Prospective Data From the WHS

Background

Pathologic angiogenesis is a hallmark of type 2 diabetes mellitus (T2DM) microvascular complications and may modulate adipogenesis and precede the onset of clinical diabetes mellitus; however, longitudinal data are unavailable. Placental growth factor is a potent proangiogenic factor that stimulates the formation of mature and durable vessels but is understudied in human diseases.

Methods and Results

We conducted a prospective case‐cohort study of baseline placental growth factor and incident T2DM within the WHS (Women's Health Study). A random sample of incident T2DM cases (n=491) occurring over a 15‐year follow‐up period was selected and compared with a reference subcohort (n=561). Case subjects were matched to the reference risk set on 5‐year age groups and race. All subjects in this analysis were required to have a hemoglobin A_1c <6.5% at WHS enrollment. Median baseline levels of placental growth factor were higher in case subjects compare to the reference subcohort (18.0 pg/mL versus 17.2 pg/mL) but were only weakly correlated with glycemic measures and not associated with obesity. The risk of diabetes mellitus increased across placental growth factor quartile in the base model (hazard ratios, 1.00, 1.14, 1.46, and 2.14; P‐trend<0.001) and in multivariable‐adjusted models accounting for clinical T2DM risk factors (hazard ratios, 1.00, 1.17, 1.45, and 2.61; P‐trend<0.001). These findings were not substantially altered by further adjustment for high‐sensitivity C‐reactive protein, hemoglobin A_1c, or fasting insulin and remained robust in sensitivity analyses excluding those diagnosed within 2 years of enrollment and those with baseline hemoglobin A_1c ≥6.0%.

Conclusions

Elevated placental growth factor levels are associated with future T2DM independent of traditional risk factors, measures of glycemia, insulin resistance, and high‐sensitivity C‐reactive protein. These prospective data suggest that pathologic angiogenesis may occur well before the clinical onset of T2DM and thus may have relevance to vascular complications of this disease.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000479.

Ultrasound Microbubble Delivery Targeting Intraplaque Neovascularization Inhibits Atherosclerotic Plaque in an APOE-deficient Mouse Model

BACKGROUND/AIM

Intraplaque neovascularization is often associated with plaque formation, development and instability, and clinical symptoms in atherosclerosis. The aim of the present study was to investigate a new strategy for treating athrosclerosis by ultrasound-targeted microbubble delivery (UTMD) targeting intraplaque neovascularization in an APOE-deficient mouse model of atherosclerosis.

MATERIALS AND METHODS

A mouse model of atherosclerosis was induced by feeding Apoe^-/- mice a hypercholesterolemic diet and was verified with hematoxylin and eosin staining and intercellular adhesion molecule 1 (ICAM-1) expression. Targeted microbubbles (MB) were prepared by conjugating microbubbles with biotinylated antibody to ICAM1 (MBi) or with both biotinylated anti-ICAM1 and the angiogenesis inhibitor Endostar (MBie). The targeted microbubbles were analyzed with epifluorescence microscopy and flow cytometry. The animals with induced atherosclerotic plaques received MBi or MBie followed by UTMD treatment. Endostar treatment alone was given to other animals for comparison. Morphological assessment of atherosclerotic plaques was performed after treatment. The expression of angiogenesis marker CD31 was detected by immunohistochemical analysis.

RESULTS

Atherosclerotic plaques developed in the entire aorta with significant intraplaque ICAM-1 expression in the APOE-deficient mice following a 30-week hypercholesterolemic diet. Microbubbles were successfully conjugated with anti-ICAM-1 and Endostar, with a conjugation rate of 98.3% and 63.5%, respectively. UTMD with MBie significantly reduced the area of atherosclerotic plaque as compared to the model control (p<0.05). Treatment with Endostar and UTMD with MBie significantly reduced CD31 expression compared with the model control group (p<0.01). Greater significant inhibitory effect on CD31 expression was found in the group treated with UTMD and MBie compared to the Endostar- and UTMD with MBi groups (p<0.01).

CONCLUSION

UTMD targeting intraplaque neovascularization was found to inhibit atherosclerotic plaque in a mouse model of atherosclerosis, suggesting the potential of microbubble-mediated ultrasound technology in aiding drug delivery for atherosclerosis treatment.

Semaphorins and Their Receptors: From Axonal Guidance to Atherosclerosis

Semaphorins are a large family of secreted, transmembrane, or GPI-anchored proteins initially identified as axon guidance cues signaling through their receptors, neuropilins, and plexins. Emerging evidence suggests that beyond the guidance, they also function in a broad spectrum of pathophysiological conditions, including atherosclerosis, a vascular inflammatory disease. Particular semaphorin members have been demonstrated to participate in atherosclerosis via eliciting endothelial dysfunction, leukocyte infiltration, monocyte-macrophage retention, platelet hyperreactivity, and neovascularization. In this review, we focus on the role of those semaphorin family members in the development of atherosclerosis and highlight the mechanistic relevance of semaphorins to atherogenesis.

Role of Hyperglycemia-Induced Advanced Glycation End Product (AGE) Accumulation in Atherosclerosis

There is a growing body of evidence that cumulative hyperglycemic exposure plays a central role in the development and progression of atherosclerotic cardiovascular disease in diabetic patients. Monosaccharides, such as glucose, fructose, and glyceraldehyde can react non-enzymatically with amino groups of proteins, lipids, nucleic acids to form senescent macromolecules termed advanced glycation end products (AGEs), whose formation and accumulation has been known to progress in diabetic patients, especially in those with a long history of disease. The sustained accumulation of AGEs could contribute to the phenomenon of metabolic memory or legacy effects observed in long-term follow-up clinical studies of diabetic patients. AGE modification alters the structural integrity and function of various types of macromolecules, and interaction of AGEs with a receptor for AGEs (RAGE) has been shown to evoke inflammatory and thrombotic reactions. Therefore, the AGE-RAGE axis is a novel therapeutic target of atherosclerotic cardiovascular disease in diabetic patients. In this paper, we briefly review the pathological role of AGEs and their receptor RAGE system in atherosclerotic cardiovascular disease, including peripheral artery disease and discuss the clinical utility of measuring AGEs in evaluating the severity of atherosclerosis in patients with diabetes.

Holistic Regulation of Angiogenesis with Chinese Herbal Medicines as a New Option for Coronary Artery Disease

Effectively improving myocardial blood flow and controlling atherosclerotic plaque have always been key and difficult points in the prevention and treatment of coronary artery disease (CAD). Although “therapeutic angiogenesis” is regarded as a promising approach for ischemic heart disease by improving blood flow, angiogenesis itself can induce the destabilization of atherosclerotic plaque, which reflects the double-edged role of angiogenesis. Modulating the balance of angiogenesis can be an important target for CAD treatment. Traditional Chinese medicine (TCM) emphasizes the holistic view and dynamic balance of the body. Furthermore, the principle of activating blood circulation and removing blood stasis (ABCRS) is closely connected with angiogenesis and CAD. Recent research suggests that Chinese herbal medicines for ABCRS are effective in balancing the regulation of angiogenesis. This review presents the progress of recent research on the angiogenesis regulation with Chinese herbal medicines for ABCRS in CAD. Moreover, this review demonstrates that Chinese herbal medicines for ABCRS can not only promote angiogenesis in the ischemic area to improve myocardial blood flow but also alleviate angiogenesis to stabilize plaque in atherosclerosis, which reflects the holistic regulatory role in CAD treatment.

Mathematical modeling of atherosclerotic plaque destabilization: Role of neovascularization and intraplaque hemorrhage

Observational studies have identified angiogenesis from the adventitial vasa vasorum and intraplaque hemorrhage (IPH) as critical factors in atherosclerotic plaque progression and destabilization. Here we propose a mathematical model incorporating intraplaque neovascularization and hemodynamic calculation with plaque destabilization for the quantitative evaluation of the role of neoangiogenesis and IPH in the vulnerable atherosclerotic plaque formation. An angiogenic microvasculature is generated by two-dimensional nine-point discretization of endothelial cell proliferation and migration from the vasa vasorum. Three key cells (endothelial cells, smooth muscle cells and macrophages) and three key chemicals (vascular endothelial growth factors, extracellular matrix and matrix metalloproteinase) are involved in the plaque progression model, and described by the reaction-diffusion partial differential equations. The hemodynamic calculation of the microcirculation on the generated microvessel network is carried out by coupling the intravascular, interstitial and transvascular flow. The plasma concentration in the interstitial domain is defined as the description of IPH area according to the diffusion and convection with the interstitial fluid flow, as well as the extravascular movement across the leaky vessel wall. The simulation results demonstrate a series of pathophysiological phenomena during the vulnerable progression of an atherosclerotic plaque, including the expanding necrotic core, the exacerbated inflammation, the high microvessel density (MVD) region at the shoulder areas, the transvascular flow through the capillary wall and the IPH. The important role of IPH in the plaque destabilization is evidenced by simulations with varied model parameters. It is found that the IPH can significantly speed up the plaque vulnerability by increasing necrotic core and thinning fibrous cap. In addition, the decreased MVD and vessel permeability may slow down the process of plaque destabilization by reducing the IPH dramatically. We envision that the present model and its future advances can serve as a valuable theoretical platform for studying the dynamic changes in the microenvironment during the plaque destabilization.

Non-coding RNA regulation of endothelial and macrophage functions during atherosclerosis

The endothelial lining can be viewed as the first line of defense against risk factors of vascular disease. Endothelial dysfunction is regarded as an initial event for atherogenesis since defects in vascular integrity and homeostasis are responsible for lipid infiltration and recruitment of monocytes into the vessel wall. Monocytes-turned-macrophages, which possess astounding inflammatory plasticity, perpetuate chronic inflammation and growth of atherosclerotic plaques and, are therefore central for the pathogenesis of atherosclerosis. Because endothelial cells and macrophages are key players during atherogenesis, it is crucial to understand the regulation of their functions in order to develop strategies to intervene disease progression. Interestingly, non-coding RNAs (ncRNAs), broad class of RNA molecules that do not code for proteins, are capable of reprogramming multiple cell functions and, thus, can be used as target agents. MicroRNAs are small ncRNAs whose roles in the regulation of vascular functions and development of atherosclerosis through post-transcriptional manipulation of gene expression have been widely explored. Recently, other ncRNAs including long noncoding RNAs (lncRNAs) have also emerged as potential regulators of these functions. However, given their poor-genetic conservation between species, much work will be needed to elucidate the specific role of lncRNAs in vascular biology. This review aims to provide a comprehensive perspective of ncRNA, mostly focusing in lncRNAs, mechanism of action and relevance in regulating lipid metabolism-independent endothelial and macrophages functions in the pathogenesis of atherosclerosis.

MicroRNAs in Cardiovascular Disease: Perspectives and Reality

Since the discovery of the first noncoding RNA decades ago, the transcriptomics evolution has made a great leap reaching to the detection and recognition of microRNAs (miRNAs) in the early 1990s. Thereafter, numerous miRNAs were reported in different species, with a great body of literature focusing on their role in human health and in pathophysiological processes. miRNAs play a significant role in the cardiovascular system, not only in physiology and normal development but also in disease processes and evolution. Further studies on miRNAs have highlighted their participation in several expressions of cardiovascular disease, such as atherosclerosis, acute and chronic syndromes of coronary artery disease, heart failure, and cardiac arrhythmias. To date, the challenge remains to understand the underlying mechanisms of miRNAs that drive their expression profile so as to use them as innovative diagnostic tools or therapeutic targets in cardiovascular disease.

Advanced Glycation End Products: A Molecular Target for Vascular Complications in Diabetes

A nonenzymatic reaction between reducing sugars and amino groups of proteins, lipids and nucleic acids contributes to the aging of macromolecules and subsequently alters their structural integrity and function. This process has been known to progress at an accelerated rate under hyperglycemic and/or oxidative stress conditions. Over a course of days to weeks, early glycation products undergo further reactions such as rearrangements and dehydration to become irreversibly cross-linked, fluorescent and senescent macroprotein derivatives termed advanced glycation end products (AGEs). There is a growing body of evidence indicating that interaction of AGEs with their receptor (RAGE) elicits oxidative stress generation and as a result evokes proliferative, inflammatory, thrombotic and fibrotic reactions in a variety of cells. This evidence supports AGEs' involvement in diabetes- and aging-associated disorders such as diabetic vascular complications, cancer, Alzheimer's disease and osteoporosis. Therefore, inhibition of AGE formation could be a novel molecular target for organ protection in diabetes. This report summarizes the pathophysiological role of AGEs in vascular complications in diabetes and discusses the potential clinical utility of measurement of serum levels of AGEs for evaluating organ damage in diabetes.

The Use of Contrast-enhanced Ultrasonography for Imaging of Carotid Atherosclerotic Plaques: Current Evidence, Future Directions

Contrast-enhanced ultrasonography (CEUS) is a rapidly evolving modality for imaging carotid artery disease and systemic atherosclerosis. CEUS coupled with diagnostic ultrasonography predicts the degree of carotid artery stenosis and is comparable with computed tomography and magnetic resonance angiography. This article reviews the literature on the evolving role of CEUS for the identification and characterization of carotid plaques with an emphasis on detection of intra-plaque neovascularization and related high-risk morphologic features notably present in symptomatic patients. CEUS carotid imaging may play a prominent additive role in risk stratifying patients and serve as a powerful tool for monitoring therapeutic interventions.

Muscle weakness during aging: a deficiency state involving declining angiogenesis

This essay begins by proposing that muscle weakness of old age from sarcopenia is due in large part to reduced capillary density in the muscles, as documented in 9 reports of aged persons and animals. Capillary density (CD) is determined by local levels of various angiogenic factors, which also decline in muscles with aging, as reported in 7 studies of old persons and animals. There are also numerous reports of reduced CD in the aged brain and other studies showing reduced CD in the kidney and heart of aged animals. Thus a waning angiogenesis throughout the body may be a natural occurrence in later years and may account significantly for the lesser ailments (physical and cognitive) of elderly people. Old age is regarded here as a deficiency state which may be corrected by therapeutic angiogenesis, much as a hormonal deficiency can be relieved by the appropriate hormone therapy. Such therapy could employ recombinant angiogenic factors which are now commercially available.

The therapeuatic effect of Endostar on soft carotid plaque neovascularization in patients with non-small cell lung cancer

The purpose of this study was to investigate the effect of the angiogenesis inhibitor Endostar on carotid plaque neovascularization in patients with non-small cell lung cancer (NSCLC) using contrast-enhanced ultrasound (CEUS). Ninety-one patients who had NSCLC with soft carotid plaques were selected for treatment either with the NP regimen (vinorelbine + cisplatin) (43 patients) or with the ENP regimen (Endostar + NP) (48 patients). Plaque thickness and neovascularization of the plaque were assessed before and at 1 month after treatment using CEUS. Enhanced intensity (EI) of CEUS was used for quantification of plaque neovascularization. There was no significant changes in any group in thickness of plaque between recruitment and 1 month after treatment (P > 0.05 for all). There was no significant change in the EI of plaque in the controls or NP groups at 1 month after treatment (P > 0.05), while EI in the ENP group was significantly reduced at 1 month after treatment (P < 0.01) and significantly lower than that in the controls or NP group at 1 month after treatment (P < 0.001 both). This study indicates that carotid soft plaque neovascularization in patients with NSCLC can be reduced by anti-angiogenesis treatment.

Targeting P-selectin by gallium-68-labeled fucoidan positron emission tomography for noninvasive characterization of vulnerable plaques: correlation with in vivo 17.6T MRI

OBJECTIVE

Nuclear imaging of active plaques still remains challenging. Advanced atherosclerotic plaques have a strong expression of P-selectin by the endothelium overlying active atherosclerotic plaques, but not on the endothelium overlying inactive fibrous plaques. We proposed a new approach for noninvasive in vivo characterization of P-selectin on active plaques based on (68)Ga-Fucoidan, which is a polysaccharidic ligand of P-selectin with a nanomolar affinity.

APPROACH AND RESULTS

(68)Ga-Fucoidan was tested for its potential to discriminate vulnerable plaques on apolipoprotein E-deficient mice receiving a high cholesterol diet by positron emission tomography and in correlation with 17.6T MRI. Furthermore, (68)Ga-Fucoidan was evaluated on endothelial cells in vitro and ex vivo on active plaques using autoradiography. The cellular uptake rate was increased ≈2-fold by lipopolysaccharide induction. Interestingly, on autoradiography, more intensive tracer accumulation at active plaques with thin fibrous caps and high-density foam cells were observed in comparison with a weaker focal uptake in inactive fibrous plaque segments (R=1.7±0.3; P<0.05) and fatty streaks (R=2.4±0.4; P<0.01). Strong uptake of radiotracer colocalized with increased P-selectin expression and high-density macrophage. Focal vascular uptake (mean of target to background ratio=5.1±0.8) of (68)Ga-Fucoidan was detected in all apolipoprotein E-deficient mice. Anatomic structures of plaque were confirmed by 17.6T MRI. The autoradiography showed a good agreement of (68)Ga-Fucoidan uptake with positron emission tomography.

CONCLUSIONS

Our data suggest that (68)Ga-Fucoidan represents a versatile imaging biomarker for P-selectin with the potential to specifically detect P-selectin expression using positron emission tomography and to discriminate vulnerable plaques in vivo.

Panax notoginseng saponins inhibits atherosclerotic plaque angiogenesis by down-regulating vascular endothelial growth factor and nicotinamide adenine dinucleotide phosphate oxidase subunit 4 expression

OBJECTIVE

To investigate the mechanism of Panax notoginseng saponins (PNS), an effective component extracted from Panax notoginseng, on atherosclerotic plaque angiogenesis in atherosclerosis-prone apolipoprotein E-knockout (ApoE-KO) mice fed with high-fat, high-cholesterol diet.

METHODS

Twenty ApoE-KO mice were divided into two groups, the model group and the PNS group. Ten normal C57BL/6J mice were used as a control group. PNS (60 mg/kg) was orally administered daily for 12 weeks in the PNS group. The ratio of plaque area to vessel area was examined by histological staining. The tissue sample of aortic root was used to detect the CD34 and vascular endothelial growth factor (VEGF) expression areas by immunohistochemistry. The expression of VEGF and nicotinamide adenine dinucleotide phosphate oxidase subunit 4 (NOX4) were measured by reverse transcription polymerase chain reaction and Western blotting respectively.

RESULTS

After treatment with PNS, the plaque areas were decreased (P<0.05). CD34 expressing areas and VEGF expression areas in plaques were significantly decreased (P<0.05). Meanwhile, VEGF and NOX4 mRNA expression were decreased after treatment with PNS. VEGF and NOX4 protein expression were also decreased by about 72% and 63%, respectively (P<0.01).

CONCLUSION

PNS, which decreases VEGF and NOX4 expression, could alleviate plaque angiogenesis and attenuate atherosclerosis.

Ethanolic extract of propolis inhibits atherosclerosis in ApoE-knockout mice

Background

The present study was undertaken to investigate the effects and underlying mechanism of ethanolic extract of propolis (EEP) on the development of atherosclerotic lesions in ApoE^−/− mice.

Methods

Eight-week-old male ApoE^−/− mice fed a high-fat diet were treated with EEP (160 mg/kg/d) or vehicle (the same dose) respectively for 14 weeks. The serum levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) were determined by enzymatic methods. Non-HDL-C was calculated as TC minus HDL-C. Serum interleukin-6 (IL-6), interleukin-17 (IL-17), endothelin (ET), inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor (VEGF) were determined with enzyme-linked immunosorbent assay methods. Nitric oxide (NO) content was measured with an enzymatic nitrate reductase assay. Analyses of atherosclerotic lesions in whole aorta and aortic root sections were performed with plaque staining using Oil Red O.

Results

Compared with the vehicle-treated group, serum contents of total cholesterol (TC), triglycerides (TG) and non-HDL-C reduced significantly by 31.88%, 21.01%, and 27.11% respectively in the EEP-treated group. Administration of EEP decreased the level of IL-6 and increased the level of IL-17 in ApoE^−/− mice with a high-fat diet. Compared with the vehicle-treated group,EEP significantly reduced the levels of ET and VEGF,and showed a trend to increase NO and inhibit iNOS. In the ApoE^−/− mice fed a high-fat diet, EEP significantly reduced atherosclerotic lesion development in the aortic root and whole aorta.

Conclusion

EEP can inhibit atherosclerotic lesion formation in ApoE^−/− mice fed a high-fat diet possibly through modulating cholesterol, regulating inflammatory reaction,inhibiting ET and VEGF, and protecting vascular endothelial cells.

Vascular calcifying progenitor cells possess bidirectional differentiation potentials

Calcifying progenitor cells in blood vessels have the potential to differentiate into cells that either promote calcium accumulation or reverse accumulation, and treatment with PPAR? can shift the direction of this differentiation.

Vascular calcification is an advanced feature of atherosclerosis for which no effective therapy is available. To investigate the modulation or reversal of calcification, we identified calcifying progenitor cells and investigated their calcifying/decalcifying potentials. Cells from the aortas of mice were sorted into four groups using Sca-1 and PDGFRα markers. Sca-1⁺ (Sca-1⁺/PDGFRα⁺ and Sca-1⁺/PDGFRα⁻) progenitor cells exhibited greater osteoblastic differentiation potentials than Sca-1⁻ (Sca-1⁻/PDGFRα⁺ and Sca-1⁻/PDGFRα⁻) progenitor cells. Among Sca-1⁺ progenitor populations, Sca-1⁺/PDGFRα⁻ cells possessed bidirectional differentiation potentials towards both osteoblastic and osteoclastic lineages, whereas Sca-1⁺/PDGFRα⁺ cells differentiated into an osteoblastic lineage unidirectionally. When treated with a peroxisome proliferator activated receptor γ (PPARγ) agonist, Sca-1⁺/PDGFRα⁻ cells preferentially differentiated into osteoclast-like cells. Sca-1⁺ progenitor cells in the artery originated from the bone marrow (BM) and could be clonally expanded. Vessel-resident BM-derived Sca-1⁺ calcifying progenitor cells displayed nonhematopoietic, mesenchymal characteristics. To evaluate the modulation of in vivo calcification, we established models of ectopic and atherosclerotic calcification. Computed tomography indicated that Sca-1⁺ progenitor cells increased the volume and calcium scores of ectopic calcification. However, Sca-1⁺/PDGFRα⁻ cells treated with a PPARγ agonist decreased bone formation 2-fold compared with untreated cells. Systemic infusion of Sca-1⁺/PDGFRα⁻ cells into Apoe^−/− mice increased the severity of calcified atherosclerotic plaques. However, Sca-1⁺/PDGFRα⁻ cells in which PPARγ was activated displayed markedly decreased plaque severity. Immunofluorescent staining indicated that Sca-1⁺/PDGFRα⁻ cells mainly expressed osteocalcin; however, activation of PPARγ triggered receptor activator for nuclear factor-κB (RANK) expression, indicating their bidirectional fate in vivo. These findings suggest that a subtype of BM-derived and vessel-resident progenitor cells offer a therapeutic target for the prevention of vascular calcification and that PPARγ activation may be an option to reverse calcification.

Atherosclerosis involves hardening of the arteries and can lead to heart disease. Calcium accumulation in blood vessels contributes to this process, and this process is regulated by cells that promote calcium accumulation (osteoblasts) and cells that reverse the accumulation (osteoclasts). In this study, we show that vascular calcifying progenitor cells in the blood vessel have the potential to become either osteoblasts or osteoclasts, and that a drug can push these cells towards becoming osteoclasts instead of osteoblasts. Progenitor cells that express both Sca-1 and PDGFRα cell surface proteins were more committed to differentiate into osteoblasts, while cells that only expressed Sca-1 could differentiate into osteoblasts or osteoclasts in a bidirectional manner. Moreover, treatment with a PPARγ agonist could shift the direction of differentiation of Sca-1⁺/PDGFRα⁻ progenitor cells toward osteoclast-like cells, whereas it cannot influence the fates of Sca-1⁺/PDGFRα⁺ progenitors. These results offer new therapeutic targets for reversing calcium accumulation in blood vessels.

Tryptase promotes atherosclerotic plaque haemorrhage in ApoE-/- mice

Tryptase, the most abundant mast cell (MC) granule protein, plays an important role in atherosclerosis plaque development. To test the hypothesis that tryptase participates directly in atherosclerosis plaque haemorrhage, the gene sequence and siRNA for tryptase were cloned into a lentivirus carrier and atherosclerosis plaque haemorrhage models in ApoE-/- mice were constructed. After a cuffing-cervical artery operation, the mice were randomly divided into 6 groups. Hematoxylin and eosin(HE) staining showed that the cervical artery plaque area was much larger in the tryptase overexpression group compared to the other groups, and there was greater artery stenosis. The artery stenosis from the cuff-side in all groups was more than 90%, except the siRNA group. Tryptase promotes plaque haemorrhage distinctively because 50% of the mice in the tryptase overexpression group had plaque haemorrhage, while only 10% in the siRNA group did. The immunohistochemistry of the cervical artery plaque showed that plasminogen activator inhibitor-1 (PAI-1) expression was the lowest while tissue plasminogen activator (tPA), CD31, CD34 and VEGF was the highest in the tryptase overexpression groups. This observation was completely contrary to what was observed in the siRNA group. Tryptase promoted bEnd.3 cell growth, migration and capillary-like tube formation, which suggests that tryptase can promote microvessel angiogenesis. PAI-1 expression was inhibited, while tPA expression was increased by tryptase in bEnd.3 cells. Our in vivo and in vitro studies suggest that trypase can promote atherosclerotic plaque haemorrhage by promoting angiogenesis and regulating the balance of PAI-1 and tPA. Thus, regulating tryptase expression in MCs may provide a potential target for atherosclerosis treatment.

Assessment of atherosclerotic plaques in the rabbit abdominal aorta with interleukin-8 monoclonal antibody-targeted ultrasound microbubbles

In this study, we aimed to prepare a neovascularization-relevant inflammatory cytokine-targeted ultrasound contrast agent and apply it in the ultrasound imaging of atherosclerotic plaque. An interleukin-8 (IL-8) monoclonal antibody was conjugated to SonoVue microbubbles using the N-succinimidyl-3-(2-pyridyldithio)propionate cross-linking method. Then, a prepared IL-8-targeted contrast agent was used for contrast-enhanced ultrasound (CEU) to detect rabbit abdominal aorta atherosclerotic plaque and to investigate the imaging characteristics of atherosclerotic plaque with the contrast agent. We found that an IL-8 monoclonal antibody can be successfully coupled to SonoVue microbubbles with stable biological characteristics. CEU with this IL-8-targeted contrast agent can increase the atherosclerotic plaque detection sensitivity, with stronger echo, so that three more plaques were detected compared with using non-targeted SonoVue microbubbles. Thus, an inflammatory cytokine-targeting ultrasound contrast agent carrying IL-8 monoclonal antibody can provide unique advantages for researching the characteristics of atherosclerotic plaque.

Adventitial biology: differentiation and function

Recent evidence indicates that stem/progenitor cells are present in the adventitia and participate in vascular repair and the formation of neointimal lesions in severely damaged vessels. Data have also demonstrated that these resident stem/progenitor cells could differentiate into endothelial or smooth muscle cells in response to different stimuli. Under pathological conditions, adventitial inflammation results in releasing a panel of cytokines, such as stromal cell-derived factor-1 and tumor necrosis factor-α, that may lead to local stem/progenitor mobilization and differentiation. Overall, these data support the impact of the adventitial progenitors in pathophysiological processes of lesion development in the arterial wall. In the present review, we aim to summarize the data concerning the presence of the resident stem cells and discuss the pathological impact of the adventitia in vascular diseases. We will also discuss the possible signal pathways orchestrating stem cell differentiation toward vascular lineage and highlight controversial issues related to the role of adventitial progenitors.

Progenitor cells in arteriosclerosis: good or bad guys?

Accumulating evidence indicates that the mobilization and recruitment of circulating or tissue-resident progenitor cells that give rise to endothelial cells (ECs) and smooth muscle cells (SMCs) can participate in atherosclerosis, neointima hyperplasia after arterial injury, and transplant arteriosclerosis. It is believed that endothelial progenitor cells do exist and can repair and rejuvenate the arteries under physiologic conditions; however, they may also contribute to lesion formation by influencing plaque stability in advanced atherosclerotic plaque under specific pathologic conditions. At the same time, smooth muscle progenitors, despite their capacity to expedite lesion formation during restenosis, may serve to promote atherosclerotic plaque stabilization by producing extracellular matrix proteins. This profound evidence provides support to the hypothesis that both endothelial and smooth muscle progenitors may act as a double-edged sword in the pathogenesis of arteriosclerosis. Therefore, the understanding of the regulatory networks that control endothelial and smooth muscle progenitor differentiation is undoubtedly fundamental both for basic research and for improving current therapeutic avenues for atherosclerosis. We update the progress in progenitor cell study related to the development of arteriosclerosis, focusing specifically on the role of progenitor cells in lesion formation and discuss the controversial issues that regard the origins, frequency, and impact of the progenitors in the disease.

New advances in noninvasive imaging of the carotid artery: CIMT, contrast-enhanced ultrasound, and vasa vasorum

Carotid ultrasound measurement of carotid intima-media thickness (CIMT) and detection of plaques is a useful method to better assess cardiovascular disease risk status, especially in those at intermediate risk. We discuss the use CIMT and other emerging techniques such as contrast-enhanced carotid ultrasound imaging in the evaluation of the carotid artery and its value in cardiovascular disease.

Resident vascular progenitor cells

Homeostasis of the vessel wall is essential for maintaining its function, including blood pressure and patency of the lumen. In physiological conditions, the turnover rate of vascular cells, i.e. endothelial and smooth muscle cells, is low, but markedly increased in diseased situations, e.g. vascular injury after angioplasty. It is believed that mature vascular cells have an ability to proliferate to replace lost cells normally. On the other hand, recent evidence indicates stem/progenitor cells may participate in vascular repair and the formation of neointimal lesions in severely damaged vessels. It was found that all three layers of the vessels, the intima, media and adventitia, contain resident progenitor cells, including endothelial progenitor cells, mesenchymal stromal cells, Sca-1+ and CD34+ cells. Data also demonstrated that these resident progenitor cells could differentiate into a variety of cell types in response to different culture conditions. However, collective data were obtained mostly from in vitro culture assays and phenotypic marker studies. There are many unanswered questions concerning the mechanism of cell differentiation and the functional role of these cells in vascular repair and the pathogenesis of vascular disease. In the present review, we aim to summarize the data showing the presence of the resident progenitor cells, to highlight possible signal pathways orchestrating cell differentiation toward endothelial and smooth muscle cells, and to discuss the data limitations, challenges and controversial issues related to the role of progenitors. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".

Assessment of neovascularization within carotid plaques in patients with ischemic stroke

AIM

To assess neovascularization within human carotid atherosclerotic soft plaques in patients with ischemic stroke.

METHODS

Eighty-one patients with ischemic stroke and 95 patients without stroke who had soft atherosclerotic plaques in the internal carotid artery were studied. The thickest soft plaque in each patient was examined using contrast-enhanced ultrasound. Time-intensity curves were collected from 5 s to 3 min after contrast injection. The neovascularization within the plaques in the internal carotid artery was evaluated using the ACQ software built into the scanner by 2 of the experienced investigators who were blinded to the clinical history of the patients.

RESULTS

Ischemic stroke was present in 7 of 33 patients (21%) with grade I plaque, in 14 of 51 patients (28%) with grade II plaque, in 26 of 43 patients (61%) with grade III plaque, and in 34 of 49 patients (69%) with grade IV plaque (P < 0.001 comparing grade IV plaque with grade I plaque and with grade II plaque and P = 0.001 comparing grade III plaque with grade I plaque and with grade II plaque). Analysis of the time intensity curves revealed that patients with ischemic stroke had a significantly higher intensity of enhancement (IE) than those without ischemic stroke (P < 0.01). The wash-in time (WT) of plaque was significantly shorter in stroke patients (P < 0.05). The sensitivity and specificity for IE in the plaque were 82% and 80%, respectively, and for WT were 68% and 74%, respectively. There was no significant difference in the peak intensity or time to peak between the 2 groups.

CONCLUSION

This study shows that the higher the grade of plaque enhancement, the higher the risk of ischemic stroke. The data suggest that the presence of neovascularization is a marker for unstable plaque.

VEGF and soluble VEGF receptor-1 (sFlt-1) distributions in peripheral arterial disease: an in silico model

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis, the growth of new capillaries from existing microvasculature. In peripheral arterial disease (PAD), lower extremity muscle ischemia develops downstream of atherosclerotic obstruction. A working hypothesis proposed that the maladaptive overexpression of soluble VEGF receptor 1 (sVEGFR1) in ischemic muscle tissues, and its subsequent antagonism of VEGF bioactivity, may contribute to the deficient angiogenic response in PAD, as well as the limited success of therapeutic angiogenesis strategies where exogenous VEGF genes/proteins are delivered. The objectives of this study were to develop a computational framework for simulating the systemic distributions of VEGF and sVEGFR1 (e.g., intramuscular vs. circulating, free vs. complexed) as observed in human PAD patients and to serve as a platform for the systematic optimization of diagnostic tools and therapeutic strategies. A three-compartment model was constructed, dividing the human body into the ischemic calf muscle, blood, and the rest of the body, connected through macromolecular biotransport processes. Detailed molecular interactions between VEGF, sVEGFR1, endothelial surface receptors (VEGFR1, VEGFR2, NRP1), and interstitial matrix sites were modeled. Our simulation results did not support a simultaneous decrease in plasma sVEGFR1 during PAD-associated elevations in plasma VEGF reported in literature. Furthermore, despite the overexpression in sVEGFR1, our PAD control demonstrated increased proangiogenic signaling complex formation, relative to our previous healthy control, due to sizeable upregulations in VEGFR2 and VEGF expression, thus leaving open the possibility that impaired angiogenesis in PAD may be rooted in signaling pathway disruptions downstream of ligand-receptor binding.

Anti-angiogenic perfluorocarbon nanoparticles for diagnosis and treatment of atherosclerosis

Complementary developments in nanotechnology, genomics, proteomics, molecular biology and imaging offer the potential for early, accurate diagnosis. Molecularly-targeted diagnostic imaging agents will allow noninvasive phenotypic characterization of pathologies and, therefore, tailored treatment close to the onset. For atherosclerosis, this includes anti-angiogenic therapy with specifically-targeted drug delivery systems to arrest the development of plaques before they impinge upon the lumen. Additionally, monitoring the application and effects of this targeted therapy in a serial fashion will be important. This review covers the specific application of alpha(nu)beta(3)-targeted anti-angiogenic perfluorocarbon nanoparticles in (1) the detection of molecular markers for atherosclerosis, (2) the immediate verification of drug delivery with image-based prediction of therapy outcomes, and (3) the serial, noninvasive observation of therapeutic efficacy.

Peroxisome proliferator-activated receptors and angiogenesis

The peroxisome proliferator-activated receptors (PPARs) are a group of three nuclear receptor isoforms, PPARalpha, PPARgamma and PPARdelta, encoded by different genes, and they form a subfamily of the nuclear receptor superfamily. The clinical interest in PPARs originates with fibrates and thiazolidinediones, which, respectively, act on PPARalpha and PPARgamma and are used to ameliorate hyperlipidaemia and hyperglycaemia in subjects with type 2 diabetes mellitus (T2DM). PPARs play a central role in these patients due to their ability to regulate the expression of numerous genes involved in glycaemic control, lipid metabolism, vascular tone and inflammation. Abnormal angiogenesis is implicated in several of the long-term complications of diabetes mellitus, characterized by vasculopathy associated with aberrant growth of new blood vessels. This pathological process plays a crucial role in diabetic retinopathy, nephropathy and neuropathy, impaired wound healing and impaired coronary collateral vessel development. In recent years, there has been increasing appreciation of the fact that PPARs might be involved in the molecular mechanisms that regulate angiogenesis through the action of growth factors and cytokines that stimulate migration, proliferation and survival of endothelial cells. During the last few years direct comparative analyses have been performed, using selective PPARs agonists, to clarify the angiogenic properties of the different members of the PPAR family. Lately, the findings provide new information to order to understand the biological, clinical and therapeutic effects of PPARs, and the role of these nuclear receptors in angiogenesis, with potentially important implications for the management of subjects affected by T2DM.

A systems biology perspective on sVEGFR1: its biological function, pathogenic role and therapeutic use

Angiogenesis is the growth of new capillaries from pre-existent microvasculature. A wide range of pathological conditions, from atherosclerosis to cancer, can be attributed to either excessive or deficient angiogenesis. Central to the physiological regulation of angiogenesis is the vascular endothelial growth factor (VEGF) system – its ligands and receptors (VEGFRs) are thus prime molecular targets of pro-angiogenic and anti-angiogenic therapies. Of growing interest as a prognostic marker and therapeutic target in angiogenesis-dependent diseases is soluble VEGF receptor-1 (sVEGFR1, also known as sFlt-1) – a truncated version of the cell membrane-spanning VEGFR1. For instance, it is known that sVEGFR1 is involved in the endothelial dysfunction characterizing the pregnancy disorder of pre-eclampsia, and sVEGFR1’s therapeutic potential as an anti-angiogenic agent is being evaluated in pre-clinical models of cancer. This mini review begins with an examination of the protein domain structure and biomolecular interactions of sVEGFR1 in relation to the full-length VEGFR1. A synopsis of known and inferred physiological and pathological roles of sVEGFR1 is then given, with emphasis on the utility of computational systems biology models in deciphering the molecular mechanisms by which sVEGFR1’s purported biological functions occur. Finally, we present the need for a systems biology perspective in interpreting circulating VEGF and sVEGFR1 concentrations as surrogate markers of angiogenic status in angiogenesis-dependent diseases.

Controlling the angiogenic switch in developing atherosclerotic plaques: possible targets for therapeutic intervention

Plaque angiogenesis may have an important role in the development of atherosclerosis. Vasa vasorum angiogenesis and medial infiltration provides nutrients to the developing and expanding intima and therefore, may prevent cellular death and contribute to plaque growth and stabilization in early lesions. However in more advanced plaques, inflammatory cell infiltration, and concomitant production of numerous pro-angiogenic cytokines may be responsible for induction of uncontrolled neointimal microvessel proliferation resulting in production of immature and fragile neovessels similar to that seen in tumour development. These could contribute to development of an unstable haemorrhagic rupture-prone environment. Increasing evidence has suggested that the expression of intimal neovessels is directly related to the stage of plaque development, the risk of plaque rupture, and subsequently, the presence of symptomatic disease, the timing of ischemic neurological events and myocardial/cerebral infarction. Despite this, there is conflicting evidence regarding the causal relationship between neovessel expression and plaque thrombosis with some in vivo experimental models suggesting the contrary and as yet, few direct mediators of angiogenesis have been identified and associated with plaque instability in vivo.In recent years, an increasing number of angiogenic therapeutic targets have been proposed in order to facilitate modulation of neovascularization and its consequences in diseases such as cancer and macular degeneration. A complete knowledge of the mechanisms responsible for initiation of adventitial vessel proliferation, their extension into the intimal regions and possible de-novo synthesis of neovessels following differentiation of bone-marrow-derived stem cells is required in order to contemplate potential single or combinational anti-angiogenic therapies. In this review, we will examine the importance of angiogenesis in complicated plaque development, describe the current knowledge of molecular mechanisms of its initiation and maintenance, and discuss possible future anti-angiogenic therapies to control plaque stability.

Low vasa vasorum densities correlate with inflammation and subintimal thickening: potential role in location--determination of atherogenesis

OBJECTIVES

To assess the role of coronary vasa vasorum (VV) spatial distribution in determining the location of early atherosclerotic lesion development.

METHODS AND RESULTS

Six, 3-month-old, female, crossbred swine were fed 2% high-cholesterol (HC) diet for 3 months prior to euthanasia. Six other pigs were fed normal diet (N) for the entire 6 months. Right coronary arteries were harvested and scanned intact with micro-CT (20mum cubic-voxel-size). After scanning, randomly selected cross-sectional histological sections were stained for nuclear-factor kappaB (NF-kappaB), hypoxia-inducible factor-1alpha (HIF-1alpha), macrophages, von-Willebrand-factor, dihydroethidium (DHE), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). The number of positive stained cells, as well as intima-to-media ratio, were compared with VV density (#/mm(2)) obtained from micro-CT images (which closely matched the location of the histological sections) in each of four equal quadrants of the coronary vessel wall. In normal, as well as HC pigs, the number of NF-kappaB (r=0.73 and 0.70), HIF-1alpha (r=0.74 and 0.77), TNF-alpha (r=0.58 and 0.72) and IL-6 (r=0.70 and 0.72) positive cells as well as the expression of DHE (Kendall tau coefficient -0.64 and -0.63) inversely correlated with VV density. In HC the VV density also inversely correlated with intima/media ratios (r=0.65).

CONCLUSIONS

Our data suggest that low VV density territories within the coronary vessel wall are susceptible to hypoxia, oxidative stress and microinflammation and may therefore be starting points of early atherogenesis.

Imaging of the vulnerable plaque: noninvasive and invasive techniques

In a large proportion of previously asymptomatic individuals, sudden coronary death or acute myocardial infarction occurs as the first manifestation of coronary atherosclerosis. Imaging of coronary atheromatous plaques has traditionally centered on assessing the degree of luminal stenosis. The angiographic techniques that are routinely used to identify stenotic atherosclerotic lesions are unable to identify high-risk plaques; plaques prone to rupture and cause a cardiovascular event. This is partly due to the fact that the majority of culprit lesions that produce acute cardiovascular syndromes are not severely stenotic, possibly due to significant positive remodeling and reduced protective collateral circulation as well as because the risk of plaque rupture is more closely related to plaque content than plaque size. Recently, the focus of new imaging techniques is to identify the high risk plaques; the "vulnerable plaques." In this review, we will refer to the noninvasive and invasive techniques that can detect the vulnerable plaque.

Contrast-enhanced sonographic characteristics of neovascularization in carotid atherosclerotic plaques

PURPOSE

To evaluate neovascularization within carotid atherosclerotic plaques with contrast-enhanced sonography.

METHODS

We used contrast-enhanced sonography to examine 63 patients with carotid atherosclerotic plaques. The features of neovascularization within the plaques were analyzed and correlated with plaque size and echogenicity.

RESULTS

There were 81 atherosclerotic plaques, 62 of which (43 soft and 19 mixed) enhanced after injection of a contrast agent. The enhancement occurred from the carotid wall to the center of the plaque with a short-line pattern in 36 plaques, whereas 26 plaques enhanced from both the carotid wall and the carotid lumen, with a sparse spot pattern. The arrival time of contrast was shorter (p < 0.001) and time to peak was longer (p < 0.001) in the plaques than in the carotid lumen. Time to peak was shorter, whereas enhanced intensity was greater in soft plaques than in mixed plaques (p < 0.01 and p < 0.05, respectively). Among the 19 unenhanced plaques, 6 were hard, 3 were calcified, 3 were soft, and 7 were mixed. The thickness of the unenhanced plaques was <2.4 mm.

CONCLUSION

Contrast-enhanced sonography allows the noninvasive, dynamic evaluation of neovascularization within carotid plaques, and the presence of neovascularization may correlate with plaque morphology.