Sequential patterns of chemokine- and chemokine receptor-synthesis following vessel wall injury in porcine coronary arteries

Connecting the Dots: How Injury in the Arterial Wall Contributes to Atherosclerotic Disease

PURPOSE

The occurrence and development of atherosclerotic cardiovascular disease, which can result in severe outcomes, such as myocardial infarction, stroke, loss of limb, renal failure, and infarction of the gut, are strongly associated with injury to the intimal component of the arterial wall whether via the inside-out or outside-in pathways. The role of injury to the tunica media as a pathway of atherosclerosis initiation is an underresearched area. This review focuses on potential pathways to vessel wall injury as well as current experimental and clinical research in the middle-aged and elderly populations, including the role of exercise, as it relates to injury to the tunica media.

METHODS

A database search using PubMed and Google Scholar was conducted for research articles published between 1909 and 2023 that focused on pathways of atherogenesis and the impact of mechanical forces on wall injury. The following key words were searched: wall injury, tunica media, atherogenesis, vascular aging, and wall strain. Studies were analyzed, and the relevant information was extracted from each study.

FINDINGS

A link between high mechanical stress in the arterial wall and reduced vascular compliance was found. The stiffening and calcification of the arterial wall with aging induce high blood pressure and pulse pressure, thereby causing incident hypertension and cardiovascular disease. In turn, prolonged high mechanical stress, particularly wall strain, applied to the arterial wall during vigorous exercise, results in stiffening and calcification of tunica media, accelerated arterial aging, and cardiovascular disease events. In both scenarios, the tunica media is the primary target of mechanical stress and the first to respond to hemodynamic changes. The cyclical nature of these impacts confounds the results of each because they are not mutually exclusive.

IMPLICATIONS

The role of stress in the tunica media appears to be overlooked despite its relevance, and further research into new primary preventive therapies is needed aside from cautioning the role of vigorous exercise in the elderly population.

The p53 pathway in vasculature revisited: A therapeutic target for pathological vascular remodeling?

Pathological vascular remodeling contributes to the development of restenosis following intraluminal interventions, transplant vasculopathy, and pulmonary arterial hypertension. Activation of the tumor suppressor p53 may counteract vascular remodeling by inhibiting aberrant proliferation of vascular smooth muscle cells and repressing vascular inflammation. In particular, the development of different lines of small-molecule p53 activators ignites the hope of treating remodeling-associated vascular diseases by targeting p53 pharmacologically. In this review, we discuss the relationships between p53 and pathological vascular remodeling, and summarize current experimental data suggesting that drugging the p53 pathway may represent a novel strategy to prevent the development of vascular remodeling.

Effects of clopidogrel vs. prasugrel vs. ticagrelor on endothelial function, inflammatory parameters, and platelet function in patients with acute coronary syndrome undergoing coronary artery stenting: a randomized, blinded, parallel study

AIMS

In a randomized, parallel, blinded study, we investigate the impact of clopidogrel, prasugrel, or ticagrelor on peripheral endothelial function in patients undergoing stenting for an acute coronary syndrome.

METHODS AND RESULTS

The primary endpoint of the study was the change in endothelium-dependent flow-mediated dilation (FMD) following stenting. A total of 90 patients (age 62 ± 9 years, 81 males, 22 diabetics, 49 non-ST elevation myocardial infarctions) were enrolled. There were no significant differences among groups in any clinical parameter. Acutely before stenting, all three drugs improved FMD without differences between groups (P = 0.73). Stenting blunted FMD in the clopidogrel and ticagrelor group (both P < 0.01), but not in the prasugrel group. During follow-up, prasugrel was superior to clopidogrel [mean difference 2.13, 95% confidence interval (CI) 0.68-3.58; P = 0.0047] and ticagrelor (mean difference 1.57, 95% CI 0.31-2.83; P = 0.0155), but this difference was limited to patients who received the study therapy 2 h before stenting. Ticagrelor was not significantly superior to clopidogrel (mean difference 0.55, 95% CI -0.73 to 1.82; P = 0.39). No significant differences were seen among groups for low-flow-mediated dilation. Plasma interleukin (IL)-6 (P = 0.02 and P = 0.01, respectively) and platelet aggregation reactivity in response to adenosine diphosphate (P = 0.002 and P = 0.035) were lower in the prasugrel compared to clopidogrel and ticagrelor group.

CONCLUSION

As compared to ticagrelor and clopidogrel, therapy with prasugrel in patients undergoing stenting for an acute coronary syndrome is associated with improved endothelial function, stronger platelet inhibition, and reduced IL-6 levels, all of which may have prognostic implications. This effect was lost in patients who received the study medication immediately after stenting.

EUDRACT-NO

2011-005305-73.

Calciprotein Particles: Balancing Mineral Homeostasis and Vascular Pathology

[Figure: see text].

Identification of key pathways and core genes involved in atherosclerotic plaque progression

Background

Atherosclerosis leads to the occurrence of cardiovascular diseases. However, the molecular mechanisms that contribute to atherosclerotic plaque rupture are incompletely characterized. We aimed to identify the genes related to atherosclerotic plaque progression that could serve as novel biomarkers and interventional targets for plaque progression.

Methods

The datasets of GSE28829 in early vs. advanced atherosclerotic plaques and those of GSE41571 in stable vs. ruptured plaques from Gene Expression Omnibus (GEO) were analyzed by using bioinformatics methods. In addition, we used quantitative reverse transcription polymerase chain reaction (qRT-PCR) to verify the expression level of core genes in a mouse atherosclerosis model.

Results

There were 29 common differentially expressed genes (DEGs) between the GSE28829 and GSE41571 datasets, and the DEGs were mainly enriched in the chemokine signaling pathway and the Staphylococcus aureus infection pathway (P<0.05). We identified 6 core genes (FPR3, CCL18, MS4A4A, CXCR4, CXCL2, and C1QB) in the protein-protein interaction (PPI) network, 3 of which (CXCR4, CXCL2, and CCL18) were markedly enriched in the chemokine signaling pathway. qRT-PCR analysis showed that the messenger RNA levels of two core genes (CXCR4 and CXCL2) increased significantly during plaque progression in the mouse atherosclerosis model.

Conclusions

In summary, bioinformatics techniques proved useful for the screening and identification of novel biomarkers of disease. A total of 29 DEGs and 6 core genes were linked to atherosclerotic plaque progression, in particular the CXCR4 and CXCL2 genes.

Chemokine (C-C motif) ligand 2 and coronary artery disease: Tissue expression of functional and atypical receptors

Chemokines, particularly chemokine (C-C- motif) ligand 2 (CCL2), control leukocyte migration into the wall of the artery and regulate the traffic of inflammatory cells. CCL2 is bound to functional receptors (CCR2), but also to atypical chemokine receptors (ACKRs), which do not induce cell migration but can modify chemokine gradients. Whether atherosclerosis alters CCL2 function by influencing the expression of these receptors remains unknown. In a necropsy study, we used immunohistochemistry to explore where and to what extent CCL2 and related receptors are present in diseased arteries that caused the death of men with coronary artery disease compared with unaffected arteries. CCL2 was marginally detected in normal arteries but was more frequently found in the intima. The expression of CCL2 and related receptors was significantly increased in diseased arteries with relative differences among the artery layers. The highest relative increases were those of CCL2 and ACKR1. CCL2 expression was associated with a significant predictive value of atherosclerosis. Findings suggest the need for further insight into receptor specificity or activity and the interplay among chemokines. CCL2-associated conventional and atypical receptors are overexpressed in atherosclerotic arteries, and these may suggest new potential therapeutic targets to locally modify the overall anti-inflammatory response.

Endothelial Function: A Short Guide for the Interventional Cardiologist

An impaired function of the coronary endothelium is an important determinant of all stages of atherosclerosis, from initiation, to mediation of functional phenomena—such as spasm and plaque erosion, to atherothrombotic complications. Endothelial function is modified by therapies, including stent implantation. Finally, endothelial function changes over time, in response to physical stimuli and pharmocotherapies, and its assessment might provide information on how individual patients respond to specific therapies. In this review, we describe the role of the endothelium in the continuum of coronary atherosclerosis, from the perspective of the interventional cardiologist. In the first part, we review the current knowledge of the role of endothelial (dys)function on atherosclerotic plaque progression/instabilization and on the mechanisms of ischemia, in the absence of coronary artery stenosis. In the second part of this review, we describe the impact of coronary artery stenting on endothelial function, platelet aggregation, and inflammation.

Imaging of chemokine receptor CXCR4 expression in culprit and nonculprit coronary atherosclerotic plaque using motion-corrected [68Ga]pentixafor PET/CT

Purpose

The chemokine receptor CXCR4 is a promising target for molecular imaging of CXCR4⁺ cell types, e.g. inflammatory cells, in cardiovascular diseases. We speculated that a specific CXCR4 ligand, [⁶⁸Ga]pentixafor, along with novel techniques for motion correction, would facilitate the in vivo characterization of CXCR4 expression in small culprit and nonculprit coronary atherosclerotic lesions after acute myocardial infarction by motion-corrected targeted PET/CT.

Methods

CXCR4 expression was analysed ex vivo in separately obtained arterial wall specimens. [⁶⁸Ga]Pentixafor PET/CT was performed in 37 patients after stent-based reperfusion for a first acute ST-segment elevation myocardial infarction. List-mode PET data were reconstructed to five different datasets using cardiac and/or respiratory gating. Guided by CT for localization, the PET signals of culprit and various groups of nonculprit coronary lesions were analysed and compared.

Results

Ex vivo, CXCR4 was upregulated in atherosclerotic lesions, and mainly colocalized with CD68⁺ inflammatory cells. In vivo, elevated CXCR4 expression was detected in culprit and nonculprit lesions, and the strongest CXCR4 PET signal (median SUV_max 1.96; interquartile range, IQR, 1.55–2.31) was observed in culprit coronary artery lesions. Stented nonculprit lesions (median SUV_max 1.45, IQR 1.23–1.88; P = 0.048) and hot spots in naive remote coronary segments (median SUV_max 1.34, IQR 1.23–1.74; P = 0.0005) showed significantly lower levels of CXCR4 expression. Dual cardiac/respiratory gating provided the strongest CXCR4 PET signal and the highest lesion detectability.

Conclusion

We demonstrated the basic feasibility of motion-corrected targeted PET/CT imaging of CXCR4 expression in coronary artery lesions, which was triggered by vessel wall inflammation but also by stent-induced injury. This novel methodology may serve as a platform for future diagnostic and therapeutic clinical studies targeting the biology of coronary atherosclerotic plaque.

Electronic supplementary material

The online version of this article (10.1007/s00259-018-4076-2) contains supplementary material, which is available to authorized users.

Roles of Cells from the Arterial Vessel Wall in Atherosclerosis

Atherosclerosis has been identified as a chronic inflammatory disease of the arterial vessel wall. Accumulating evidence indicates that different cells from the tunica intima, media, adventitia, and perivascular adipose tissue not only comprise the intact and normal arterial vessel wall but also participate all in the inflammatory response of atherosclerosis via multiple intricate pathways. For instance, endothelial dysfunction has historically been considered to be the initiator of the development of atherosclerosis. The migration and proliferation of smooth muscle cells also play a pivotal role in the progression of atherosclerosis. Additionally, the fibroblasts from the adventitia and adipocytes from perivascular adipose tissue have received considerable attention given their special functions that contribute to atherosclerosis. In addition, numerous types of cytokines produced by different cells from the arterial vessel wall, including endothelium-derived relaxing factors, endothelium-derived contracting factors, tumor necrosis factors, interleukin, adhesion molecules, interferon, and adventitium-derived relaxing factors, have been implicated in atherosclerosis. Herein, we summarize the possible roles of different cells from the entire arterial vessel wall in the pathogenesis of atherosclerosis.

Clinical significance of monocyte heterogeneity

Monocytes are primitive hematopoietic cells that primarily arise from the bone marrow, circulate in the peripheral blood and give rise to differentiated macrophages. Over the past two decades, considerable attention to monocyte diversity and macrophage polarization has provided contextual clues into the role of myelomonocytic derivatives in human disease. Until recently, human monocytes were subdivided based on expression of the surface marker CD16. "Classical" monocytes express surface markers denoted as CD14(++)CD16(-) and account for greater than 70% of total monocyte count, while "non-classical" monocytes express the CD16 antigen with low CD14 expression (CD14(+)CD16(++)). However, recognition of an intermediate population identified as CD14(++)CD16(+) supports the new paradigm that monocytes are a true heterogeneous population and careful identification of specific subpopulations is necessary for understanding monocyte function in human disease. Comparative studies of monocytes in mice have yielded more dichotomous results based on expression of the Ly6C antigen. In this review, we will discuss the use of monocyte subpopulations as biomarkers of human disease and summarize correlative studies in mice that may yield significant insight into the contribution of each subset to disease pathogenesis.

Adventitial CXCL1/G-CSF expression in response to acute aortic dissection triggers local neutrophil recruitment and activation leading to aortic rupture

RATIONALE

In-hospital outcomes are generally acceptable in patients with type B dissection; however, some patients present with undesirable complications, such as aortic expansion and rupture. Excessive inflammation is an independent predictor of adverse clinical outcomes.

OBJECTIVE

We have investigated the underlying mechanisms of catastrophic complications after acute aortic dissection (AAD) in mice.

METHODS AND RESULTS

When angiotensin II was administered in lysyl oxidase inhibitor-preconditioned mice, AAD emerged within 24 hours. The dissection was initiated at the proximal site of the descending thoracic aorta and propagated distally into an abdominal site. Dissection of the aorta caused dilatation, and ≈70% of the mice died of aortic rupture. AAD triggered CXCL1 and granulocyte-colony stimulating factor expression in the tunica adventitia of the dissected aorta, leading to elevation of circulating CXCL1/granulocyte-colony stimulating factor levels. Bone marrow CXCL12 was reduced. These chemokine changes facilitated neutrophil egress from bone marrow and infiltration into the aortic adventitia. Interference of CXCL1 function using an anti-CXCR2 antibody reduced neutrophil accumulation and limited aortic rupture post AAD. The tunica adventitia of the expanded dissected aorta demonstrated high levels of interleukin-6 (IL-6) expression. Neutrophils were the major sources of IL-6, and CXCR2 neutralization significantly reduced local and systemic levels of IL-6. Furthermore, disruption of IL-6 effectively suppressed dilatation and rupture of the dissected aorta without any influence on the incidence of AAD and neutrophil mobilization.

CONCLUSIONS

Adventitial CXCL1/granulocyte-colony stimulating factor expression in response to AAD triggers local neutrophil recruitment and activation. This leads to adventitial inflammation via IL-6 and results in aortic expansion and rupture.

Proinflammatory phenotype of perivascular adipocytes

Perivascular adipose tissue (PVAT) directly abuts the lamina adventitia of conduit arteries and actively communicates with the vessel wall to regulate vascular function and inflammation. Mounting evidence suggests that the biological activities of PVAT are governed by perivascular adipocytes, a unique class of adipocyte with distinct molecular and phenotypic characteristics. Perivascular adipocytes surrounding human coronary arteries (pericoronary perivascular adipocytes) exhibit a reduced state of adipogenic differentiation and a heightened proinflammatory state, secreting ≤50-fold higher levels of the proinflammatory cytokine monocyte chemoattractant peptide-1 compared with adipocytes from other regional depots. Thus, perivascular adipocytes may contribute to upregulated inflammation of PVAT observed in atherosclerotic human blood vessels. However, perivascular adipocytes also secrete anti-inflammatory molecules such as adiponectin, and elimination of PVAT in rodent models has been shown to augment vascular disease, suggesting that some amount of PVAT is required to maintain vascular homeostasis. Evidence in animal models and humans suggests that inflammation of PVAT may be modulated by environmental factors, such as high-fat diet and tobacco smoke, which are relevant to atherosclerosis. These findings suggest that the inflammatory phenotype of PVAT is diverse depending on species, anatomic location, and environmental factors and that these differences are fundamentally important in determining a pathogenic versus protective role of PVAT in vascular disease. Additional research into the mechanisms that regulate the inflammatory balance of perivascular adipocytes may yield new insight into, and treatment strategies for, cardiovascular disease.

The CXCL12/CXCR4 chemokine ligand/receptor axis in cardiovascular disease

The chemokine receptor CXCR4 and its ligand CXCL12 play an important homeostatic function by mediating the homing of progenitor cells in the bone marrow and regulating their mobilization into peripheral tissues upon injury or stress. Although the CXCL12/CXCR4 interaction has long been regarded as a monogamous relation, the identification of the pro-inflammatory chemokine macrophage migration inhibitory factor (MIF) as an important second ligand for CXCR4, and of CXCR7 as an alternative receptor for CXCL12, has undermined this interpretation and has considerably complicated the understanding of CXCL12/CXCR4 signaling and associated biological functions. This review aims to provide insight into the current concept of the CXCL12/CXCR4 axis in myocardial infarction (MI) and its underlying pathologies such as atherosclerosis and injury-induced vascular restenosis. It will discuss main findings from in vitro studies, animal experiments and large-scale genome-wide association studies. The importance of the CXCL12/CXCR4 axis in progenitor cell homing and mobilization will be addressed, as will be the function of CXCR4 in different cell types involved in atherosclerosis. Finally, a potential translation of current knowledge on CXCR4 into future therapeutical application will be discussed.

Effects of clopidogrel, prasugrel and ticagrelor on endothelial function, inflammatory and oxidative stress parameters and platelet function in patients undergoing coronary artery stenting for an acute coronary syndrome. A randomised, prospective, controlled study

INTRODUCTION

Particularly in the setting of acute coronary syndromes, the interplay between vascular and platelet function has been postulated to have direct clinical implications. The present trial is designed to test the effect of clopidogrel, prasugrel and ticagrelor on multiple parameters of vascular function, platelet aggregation, oxidative and inflammatory stress before and up to 4 weeks after coronary artery stenting.

METHODS AND ANALYSIS

The study is designed as a three-arm, parallel design, randomised, investigator-blinded study. Patients with unstable angina or non-ST elevation myocardial infarction undergoing coronary intervention with a drug-eluting stent will be randomised to receive 600 mg clopidogrel, 60 mg prasugrel or 180 mg ticagrelor followed by oral therapy with the same drug. The primary endpoint of the trial is the impact of antiplatelet treatments on endothelial function as assessed by flow-mediated dilation at 1 day, 1 week and 1 month in patients who have undergone stenting. Secondary endpoints include the impact of study medications on parameters of macrovascular and microvascular function, platelet reactivity, oxidative and inflammatory stress. The study recruitment is currently ongoing and, after an interim analysis which was performed at 50% of the initially planned population, it is planned to continue until July 2015.

ETHICS AND DISSEMINATION

The protocol was approved by the local ethics committee. The trial will provide important pathophysiological insight on the relationship between platelet aggregation and endothelial function, two parameters that have been shown to influence patients' prognosis.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT01700322; EudraCT-Nr.: 2011-005305-73. Current V.1.3, from 24 February 2014.

Immune-related chemotactic factors were found in acute coronary syndromes by bioinformatics

DNA microarray data for thrombus-related leukocyte from patients with acute coronary syndrome (ACS) was analyzed to acquire key genes associated with ACS. Microarray data set GSE19339, including four ACS patients' samples and four normal samples, were downloaded from Gene Expression Omnibus database. Raw data was pre-processed and differentially expressed genes (DEGs) were identified by Affy packages of R. The interaction network was established with STRING. DrugBank was retrieved to obtain relevant small molecules. A total of 487 differentially expressed genes were identified as DEGs between normal and disease samples. Among which, ten up-regulated genes belonging to chemokine family (CCL2, CCR1, CXCL3, CXCL2, CCL8, CXCL11, CCL7, IL10, CCL22 and CCL20) were related to inflammatory response. In addition, two inhibitors of CCL2 (L-Mimosine) were retrieved from the DrugBank database. Considering the roles of inflammatory response in the progression of ACS and the functions of the ten up-regulated genes, we speculated that these genes might be related to ACS. Moreover, the inhibitors could provide guidelines for future drug design acting on these genes.

The CCR5 chemokine receptor mediates vasoconstriction and stimulates intimal hyperplasia in human vessels in vitro

AIMS

The chemokine receptor CCR5 and its inflammatory ligands have been linked to atherosclerosis, an accelerated form of which occurs in saphenous vein graft disease. We investigated the function of vascular smooth muscle CCR5 in human coronary artery and saphenous vein, vascular tissues susceptible to atherosclerosis, and vasospasm.

METHODS AND RESULTS

CCR5 ligands were vasoconstrictors in saphenous vein and coronary artery. In vein, constrictor responses to CCL4 were completely blocked by CCR5 antagonists, including maraviroc. CCR5 antagonists prevented the development of a neointima after 14 days in cultured saphenous vein. CCR5 and its ligands were expressed in normal and diseased coronary artery and saphenous vein and localized to medial and intimal smooth muscle, endothelial, and inflammatory cells. [(125)I]-CCL4 bound to venous smooth muscle with KD = 1.15 ± 0.26 nmol/L and density of 22 ± 9 fmol mg(-1) protein.

CONCLUSIONS

Our data support a potential role for CCR5 in vasoconstriction and neointimal formation in vitro and imply that CCR5 chemokines may contribute to vascular remodelling and augmented vascular tone in human coronary artery and vein graft disease. The repurposing of maraviroc for the treatment of cardiovascular disease warrants further investigation.

Blocking Notch in endothelial cells prevents arteriovenous fistula failure despite CKD

Neointima formation causes the failure of 60% of arteriovenous fistulas (AVFs) within 2 years. Neointima-forming mechanisms are controversial but possibly linked to excess proinflammatory responses and dysregulated Notch signaling. To identify how AVFs fail, we anastomosed the carotid artery to the internal jugular vein in normal and uremic mice and compared these findings with those in failed AVFs from patients with ESRD. Endothelial cells (ECs) of AVFs in uremic mice or patients expressed mesenchymal markers (FSP-1 and/or α-SMA) and exhibited increased expression and nuclear localization of Notch intracellular domain compared with ECs of AVFs in pair-fed control mice. Furthermore, expression of VE-Cadherin decreased, whereas expression of Notch1 and -4, Notch ligands, the downstream transcription factor of Notch, RBP-Jκ, and Notch target genes increased in ECs of AVFs in uremic mice. In cultured ECs, ectopic expression of Notch ligand or treatment with TGF-β1 triggered the expression of mesenchymal markers and induced endothelial cell barrier dysfunction, both of which were blocked by Notch inhibition or RBP-Jκ knockout. Furthermore, Notch-induced defects in barrier function, invasion of inflammatory cells, and neointima formation were suppressed in mice with heterozygous knockdown of endothelial-specific RBP-Jκ. These results suggest that increased TGF-β1, a complication of uremia, activates Notch in endothelial cells of AVFs, leading to accelerated neointima formation and AVF failure. Suppression of Notch activation could be a strategy for improving AFV function in uremia.

The adventitia: Essential role in pulmonary vascular remodeling

A rapidly emerging concept is that the vascular adventitia acts as a biological processing center for the retrieval, integration, storage, and release of key regulators of vessel wall function. It is the most complex compartment of the vessel wall and comprises a variety of cells including fibroblasts, immunomodulatory cells, resident progenitor cells, vasa vasorum endothelial cells, and adrenergic nerves. In response to vascular stress or injury, resident adventitial cells are often the first to be activated and reprogrammed to then influence tone and structure of the vessel wall. Experimental data indicate that the adventitial fibroblast, the most abundant cellular constituent of adventitia, is a critical regulator of vascular wall function. In response to vascular stresses such as overdistension, hypoxia, or infection, the adventitial fibroblast is activated and undergoes phenotypic changes that include proliferation, differentiation, and production of extracellular matrix proteins and adhesion molecules, release of reactive oxygen species, chemokines, cytokines, growth factors, and metalloproteinases that, collectively, affect medial smooth muscle cell tone and growth directly and that stimulate recruitment and retention of circulating inflammatory and progenitor cells to the vessel wall. Resident dendritic cells also participate in "sensing" vascular stress and actively communicate with fibroblasts and progenitor cells to simulate repair processes that involve expansion of the vasa vasorum, which acts as a conduit for further delivery of inflammatory/progenitor cells. This review presents the current evidence demonstrating that the adventitia acts as a key regulator of pulmonary vascular wall function and structure from the "outside in."

Monocyte chemoattractant protein 1-mediated migration of mesenchymal stem cells is a source of intimal hyperplasia

OBJECTIVE

Intimal hyperplasia is considered to be a healing response and is a major cause of vessel narrowing after injury, where migration of vascular progenitor cells contributes to pathological events, including transplant arteriosclerosis.

APPROACH AND RESULTS

In this study, we used a rat aortic-allograft model to identify the predominant cell types associated with transplant arteriosclerosis and to identify factors important in their recruitment into the graft. Transplantation of labeled adventitial tissues allowed us to identify the adventitia as a major source of cells migrating to the intima. RNA microarrays revealed a potential role for monocyte chemoattractant protein 1 (MCP-1), stromal cell-derived factor 1, regulated on activation, normal T cell expressed and secreted, and interferon-inducible protein 10 in the induced vasculopathy. MCP-1 induced migration of adventitial fibroblast cells. CCR2, the receptor for MCP-1, was coexpressed with CD90, CD44, NG2, or sca-1 on mesenchymal stem cells. In vivo experiments using MCP-1-deficient and CCR2-deficient mice confirmed an important role of MCP-1 in the formation of intimal hyperplasia in a mouse model of vascular injury.

CONCLUSIONS

The adventitia is a potentially important cellular source that contributes to intimal hyperplasia, and MCP-1 is a potent chemokine for the recruitment of adventitial vascular progenitor cells to intimal lesions.

Gene therapy for the prevention of vein graft disease

Ischemic cardiovascular disease remains the leading cause of death worldwide. Despite advances in the medical management of atherosclerosis over the past several decades, many patients require arterial revascularization to reduce mortality and alleviate ischemic symptoms. Technological advancements have led to dramatic increases in the use of percutaneous and endovascular approaches, yet surgical revascularization (bypass surgery) with autologous vein grafts remains a mainstay of therapy for both coronary and peripheral artery disease. Although bypass surgery is highly efficacious in the short term, long-term outcomes are limited by relatively high failure rates as a result of intimal hyperplasia, which is a common feature of vein graft disease. The supply of native veins is limited, and many individuals require multiple grafts and repeat procedures. The need to prevent vein graft failure has led to great interest in gene therapy approaches to this problem. Bypass grafting presents an ideal opportunity for gene therapy, as surgically harvested vein grafts can be treated with gene delivery vectors ex vivo, thereby maximizing gene delivery while minimizing the potential for systemic toxicity and targeting the pathogenesis of vein graft disease at its onset. Here we will review the pathogenesis of vein graft disease and discuss vector delivery strategies and potential molecular targets for its prevention. We will summarize the preclinical and clinical literature on gene therapy in vein grafting and discuss additional considerations for future therapies to prevent vein graft disease.

Targeting the adventitial microenvironment in pulmonary hypertension: A potential approach to therapy that considers epigenetic change

Experimental data indicate that the adventitial compartment of blood vessels, in both the pulmonary and systemic circulations, like the connective tissue stroma in tissues throughout the body, is a critical regulator of vessel wall function in health and disease. It is clear that adventitial cells, and in particular the adventitial fibroblast, are activated early following vascular injury, and play essential roles in regulating vascular wall structure and function through production of chemokines, cytokines, growth factors, and reactive oxygen species (ROS). The recognition of the ability of these cells to generate and maintain inflammatory responses within the vessel wall provides insight into why vascular inflammatory responses, in certain situations, fail to resolve. It is also clear that the activated adventitial fibroblast plays an important role in regulating vasa vasorum growth, which can contribute to ongoing vascular remodeling by acting as a conduit for delivery of inflammatory and progenitor cells. These functions of the fibroblast clearly support the idea that targeting chemokine, cytokine, adhesion molecule, and growth factor production in activated fibroblasts could be helpful in abrogating vascular inflammatory responses and thus in ameliorating vascular disease. Further, the recent observations that fibroblasts in vascular and fibrotic diseases may maintain their activated state through epigenetic alterations in key inflammatory and pro-fibrotic genes suggests that current therapies used to treat pulmonary hypertension may not be sufficient to induce apoptosis or to inhibit key inflammatory signaling pathways in these fibroblasts. New therapies targeted at reversing changes in the acetylation or methylation status of key transcriptional networks may be needed. At present, therapies specifically targeting abnormalities of histone deacytelase (HDAC) activity in fibroblast-like cells appear to hold promise.

Prevention of vessel desiccation and maintenance of normal morphology during endovascular harvesting using humidified warmed gas

Dry, cold CO₂ gas was found to cause tissue damage during endovascular harvest. The use of warmed, humidified CO₂ gas appeared to maintain vessel morphology and integrity during endovascular harvest by preventing tissue desiccation.

Background and Objectives:

Endoscopic vessel harvesting (EVH) traditionally uses carbon dioxide (CO₂) gas for insufflation. The CO₂ based on government regulations is bone dry and room temperature. All previous EVH studies use this type of unconditioned gas. It is hypothesized that by changing the quality of CO₂ gas differences may occur that are attributable to dry gas versus wet gas exposure.

Methods:

A comparison of the effect(s) of traditional dry CO₂ gas compared to humidified exposure was done using a porcine model and evaluated in a double-blind randomized controlled fashion.

Results:

Vessels exposed to traditional dry cold gas had morphologic and structural changes noted on histologic evaluation. This included desiccation changes of the tunica adventitia desiccation and tunica media collagen and elastin. Vessels exposed to dry gas showed 10% to 12% contraction and constriction with tortuous changes to the intima and endothelial lining that were progressive with increasing volumes of gas exposure. No desiccation or morphologic changes were seen with humidified warmed gas produced using the VesselGuardian.

Conclusions:

Traditional dry cold CO₂ caused vascular tissue damage extending from the adventitia to intima, changing the vessel in morphologic and structural configuration. With the VesselGuardian humidified warmed, gas maintained vessel morphology and integrity by preventing desiccation. Changing the quality of CO₂ from dry and cold to wet and warm may offer clinical utility for a better quality conduit for coronary artery bypass graft procedures.

From Skeleton to Cytoskeleton

Rationale:

The expression of osteocalcin is augmented in human atherosclerotic lesions. How osteocalcin triggers vascular pathogenesis and remodeling is unclear.

Objective:

To investigate whether osteocalcin promotes transformation of adventitial fibroblast to myofibroblasts and the molecular mechanism involved.

Methods and Results:

Immunohistochemistry indicated that osteocalcin was expressed in the neointima of renal arteries from diabetic patients. Western blotting and wound-healing assay showed that osteocalcin induced fibroblast transformation and migration, which were attenuated by blockers of the renin-angiotensin system and protein kinase Cδ (PKCδ), toll-like receptor 4 (TLR4) neutralizing antibody, and antagonist and inhibitors of free radical production and cyclooxygenase-2. Small interfering RNA silencing of TLR4 and PKCδ abolished fibroblast transformation. Angiotensin II level in the conditioned medium from the osteocalcin-treated fibroblasts was found elevated using enzyme immunoassay. Culturing of fibroblasts in conditioned medium collected from differentiated osteoblasts promoted fibroblast transformation. The expression of fibronectin, TLR4, and cyclooxygenase-2 is augmented in human mesenteric arteries after 5-day in vitro exposure to osteocalcin.

Conclusions:

Osteocalcin transforms adventitial fibroblasts to myofibroblasts through stimulating angiotensin II release and subsequent activation of PKCδ/TLR4/reactive oxygen species/cyclooxygenase-2 signaling cascade. This study reveals that the skeletal hormone osteocalcin cross-talks with vascular system and contributes to vascular remodeling.

Chemokine receptor CCR5: from AIDS to atherosclerosis

There is increasing recognition of an important contribution of chemokines and their receptors in the pathology of atherosclerosis and related cardiovascular disease. The chemokine receptor CCR5 was initially known for its role as a co-receptor for HIV infection of macrophages and is the target of the recently approved CCR5 antagonist maraviroc. However, evidence is now emerging supporting a role for CCR5 and its ligands CCL3 (MIP-1α), CCL4 (MIP-1β) and CCL5 (RANTES) in the initiation and progression of atherosclerosis. Specifically, the CCR5 deletion polymorphism CCR5delta32, which confers resistance to HIV infection, has been associated with a reduced risk of cardiovascular disease and both CCR5 antagonism and gene deletion reduce atherosclerosis in mouse models of the disease. Antagonism of CCL5 has also been shown to reduce atherosclerotic burden in these animal models. Crucially, CCR5 and its ligands CCL3, CCL4 and CCL5 have been identified in human and mouse vasculature and have been detected in human atherosclerotic plaque. Not unexpectedly, CC chemokines have also been linked to saphenous vein graft disease, which shares similarity to native vessel atherosclerosis. Distinct roles for chemokine-receptor systems in atherogenesis have been proposed, with CCR5 likely to be critical in recruitment of monocytes to developing plaques. With an increased burden of cardiovascular disease observed in HIV-infected individuals, the potential cardiovascular-protective effects of drugs that target the CCR5 receptor warrant greater attention. The availability of clinically validated antagonists such as maraviroc currently provides an advantage for targeting of CCR5 over other chemokine receptors.

Adipose inflammation initiates recruitment of leukocytes to mouse femoral artery: role of adipo-vascular axis in chronic inflammation

Background

Although inflammation within adipose tissues is known to play a role in metabolic syndrome, the causative connection between inflamed adipose tissue and atherosclerosis is not fully understood. In the present study, we examined the direct effects of adipose tissue on macro-vascular inflammation using intravital microscopic analysis of the femoral artery after adipose tissue transplantation.

Methods and Results

We obtained subcutaneous (SQ) and visceral (VIS) adipose tissues from C57BL/6 mice fed normal chow (NC) or a high fat diet (HF), then transplanted the tissues into the perivascular area of the femoral artery of recipient C57/BL6 mice. Quantitative intravital microscopic analysis revealed an increase in adherent leukocytes after adipose tissue transplantation, with VIS found to induce significantly more leukocyte accumulation as compared to SQ. Moreover, adipose tissues from HF fed mice showed significantly more adhesion to the femoral artery. Simultaneous flow cytometry demonstrated upregulation of CD11b on peripheral granulocyte and monocytes after adipose tissue transplantation. We also observed dominant expressions of the inflammatory cytokine IL-6, and chemokines MCP-1 and MIP-1β in the stromal vascular fraction (SVF) of these adipose tissues as well as sera of recipient mice after transplantation. Finally, massive accumulations of pro-inflammatory and dendritic cells were detected in mice with VIS transplantation as compared to SQ, as well as in HF mice as compared to those fed NC.

Conclusion

Our in vivo findings indicate that adipose tissue stimulates leukocyte accumulation in the femoral artery. The underlying mechanisms involve upregulation of CD11b in leukocytes, induction of cytokines and chemokines, and accumulation of pro-inflammatory cells in the SVF.

The vascular adventitia: its role in the arterial injury response

The belief that the adventitia serves only a structural purpose has changed over the last decade. Studies have begun to elucidate the role the adventitia plays in the arterial response to injury. The adventitial fibroblast plays an integral part in the development of neointimal hyperplasia. Adiponectin, an adipokine produced from periadventitial adipose tissue, exhibits numerous vasoprotective properties. Stem cells arise, in part, from the adventitia, and stem cell recruitment into the adventitia from the vasa vasorum has been shown to be important in the development of neointimal hyperplasia. The exact role the vasa vasorum plays in neointimal growth is poorly understood and different studies endorse conflicting viewpoints. Thus, understanding the nuances of adventitial pathophysiology will allow us to better appreciate the mechanisms behind the pathology of neointimal hyperplasia. This review will summarize recent findings on the active role the adventitia plays toward the development of neointimal hyperplasia.

Fibroblast activation in vascular inflammation

Vascular inflammation is implicated in both local and systemic inflammatory conditions. Endothelial activation and leukocyte extravasation are key events in vascular inflammation. Lately, the role of the stromal microenvironment as a source of proinflammatory stimuli has become increasingly appreciated. Stromal fibroblasts produce cytokines, growth factors and proteases that trigger and maintain acute and chronic inflammatory conditions. Fibroblasts have been associated with connective tissue pathologies such as scar formation and fibrosis, but recent research has also connected them with vascular dysfunctions. Fibroblasts are able to modulate endothelial cell functions in a paracrine manner, including proinflammatory activation and promotion of angiogenesis. They are also able to activate and attract leukocytes. Stromal fibroblasts can thus cause a proinflammatory switch in endothelial cells, and promote leukocyte infiltration into tissues. New insights in the role of adventitial fibroblasts have further strengthened the link between stromal fibroblasts and proinflammatory vascular functions. This review focuses on the role of fibroblasts in inducing and maintaining vascular inflammation, and describes recent findings and concepts in the field, along with examples of pathologic implications.

Bone marrow-derived cells contribute to vascular inflammation but do not differentiate into smooth muscle cell lineages

BACKGROUND

It has been proposed that bone marrow-derived cells infiltrate the neointima, where they differentiate into smooth muscle (SM) cells; however, technical limitations have hindered clear identification of the lineages of bone marrow-derived "SM cell-like" cells.

METHODS AND RESULTS

Using a specific antibody against the definitive SM cell lineage marker SM myosin heavy chain (SM-MHC) and mouse lines in which reporter genes were driven by regulatory programs for either SM-MHC or SM α-actin, we demonstrated that although some bone marrow-derived cells express SM α-actin in the wire injury-induced neointima, those cells did not express SM-MHC, even 30 weeks after injury. Likewise, no SM-MHC(+) bone marrow-derived cells were found in vascular lesions in apolipoprotein E(-/-)mice or in a heart transplantation vasculopathy model. Instead, the majority of bone marrow-derived SM α-actin(+) cells were also CD115(+)CD11b(+)F4/80(+)Ly-6C(+), which is the surface phenotype of inflammatory monocytes. Moreover, adoptively transferred CD11b(+)Ly-6C(+) bone marrow cells expressed SM α-actin in the injured artery. Expression of inflammation-related genes was significantly higher in neointimal subregions rich in bone marrow-derived SM α-actin(+) cells than in other regions.

CONCLUSIONS

It appears that bone marrow-derived SM α-actin(+) cells are of monocyte/macrophage lineage and are involved in vascular remodeling. It is very unlikely that these cells acquire the definitive SM cell lineage.

Associations of four circulating chemokines with multiple atherosclerosis phenotypes in a large population-based sample: results from the dallas heart study

Specific chemokines contribute to vascular inflammation and may be useful biomarkers to detect atherosclerosis. The chemokines CXCL1 and CCL11 have previously been studied in animal or human models of atherosclerosis, while CXCL2 and CCL23 have not. Among 2,454 subjects enrolled in the Dallas Heart Study, a multi-ethnic population-based sample, we measured plasma CCL11, CCL23, CXCL1, and CXCL2, and associated levels with coronary artery calcium (CAC) by computed tomography, and aortic wall thickness, plaque burden, and compliance by magnetic resonance imaging. Elevated chemokine levels were defined as greater than or equal to the median for CCL11 and CCL23 and greater than or equal to the upper detection limit for CXCL1 and CXCL2. Elevated CCL23 (P < 0.01) and CXCL1 (P = 0.01), but not CCL11 and CXCL2, associated with CAC in univariable analyses. After adjustment for traditional risk factors, elevated CCL23 remained associated with CAC (OR 1.3, 95% CI 1.0-1.7; P = 0.02), while the association with CXCL1 was modestly attenuated (OR 1.4, 95% CI 1.0-2.1; P = 0.06). CCL23 also associated with aortic wall thickness, plaque, and compliance in univariable analyses (P < 0.05 for each), but these associations were attenuated after multivariable adjustment. The novel chemotactic protein, CCL23, which has not been previously studied in atherosclerosis, is independently associated with coronary atherosclerosis, suggesting that this chemokine merits further study in animal and human models.

NOX and inflammation in the vascular adventitia

Vascular inflammation has traditionally been thought to be initiated at the luminal surface and progress through the media toward the adventitial layer. In recent years, however, evidence has emerged suggesting that the vascular adventitia is activated early in a variety of cardiovascular diseases and that it plays an important role in the initiation and progression of vascular inflammation. Adventitial fibroblasts have been shown to produce substantial amounts of NAD(P)H oxidase-derived reactive oxygen species (ROS) in response to vascular injury. Additionally, inflammatory cytokines, lipids, and various hormones, implicated in fibroblast proliferation and migration, lead to recruitment of inflammatory cells to the adventitial layer and impairment of endothelium-dependent relaxation. Early in the development of vascular disease, there is clear evidence for progression toward a denser vasa vasorum which delivers oxygen and nutrients to an increasingly hypoxic and nutrient-deficient media. This expanded vascularization appears to provide enhanced delivery of inflammatory cells to the adventitia and outer media. Combined adventitial fibroblast and inflammatory cell-derived ROS therefore are expected to synergize their local effect on adventitial parenchymal cells, leading to further cytokine release and a feed-forward propagation of adventitial ROS production. In fact, data from our laboratory and others suggest a broader paracrine positive feedback role for adventitia-derived ROS in medial smooth muscle cell hypertrophy and neointimal hyperplasia. A likely candidate responsible for the adventitia-derived paracrine signaling across the vessel wall is the superoxide anion metabolite hydrogen peroxide, which is highly stable, cell permeant, and capable of activating downstream signaling mechanisms in smooth muscle cells, leading to phenotypic modulation of smooth muscle cells. This review addresses the role of adventitial NAD(P)H oxidase-derived ROS from a nontraditional, perivascular vantage of promoting vascular inflammation and will discuss how ROS derived from adventitial NAD(P)H oxidases may be a catalyst for vascular remodeling and dysfunction.

Sustained hypoxia promotes the development of a pulmonary artery-specific chronic inflammatory microenvironment

Recent studies demonstrate that sustained hypoxia induces the robust accumulation of leukocytes and mesenchymal progenitor cells in pulmonary arteries (PAs). Since the factors orchestrating hypoxia-induced vascular inflammation are not well-defined, the goal of this study was to identify mediators potentially responsible for recruitment to and retention and differentiation of circulating cells within the hypoxic PA. We analyzed mRNA expression of 44 different chemokine/chemokine receptor, cytokine, adhesion, and growth and differentiation genes in PAs obtained via laser capture microdissection in adjacent lung parenchyma and in systemic arteries by RT-PCR at several time points of hypoxic exposure (1, 7, and 28 days) in Wistar-Kyoto rats. Analysis of inflammatory cell accumulation and protein expression of selected genes was concomitantly assessed by immunochemistry. We found that hypoxia induced progressive accumulation of monocytes and dendritic cells in the vessel wall with few T cells and no B cells or neutrophils. Upregulation of stromal cell-derived factor-1 (SDF-1), VEGF, growth-related oncogene protein-alpha (GRO-alpha), C5, ICAM-1, osteopontin (OPN), and transforming growth factor-beta (TGF-beta) preceded mononuclear cell influx. With time, a more complex pattern of gene expression developed with persistent upregulation of adhesion molecules (ICAM-1, VCAM-1, and OPN) and monocyte/fibrocyte growth and differentiation factors (TGF-beta, endothelin-1, and 5-lipoxygenase). On return to normoxia, expression of many genes (including SDF-1, monocyte chemoattractant protein-1, C5, ICAM-1, and TGF-beta) rapidly returned to control levels, changes that preceded the disappearance of monocytes and reversal of vascular remodeling. In conclusion, sustained hypoxia leads to the development of a complex, PA-specific, proinflammatory microenvironment capable of promoting recruitment, retention, and differentiation of circulating monocytic cell populations that contribute to vascular remodeling.

Pathway analysis of differentially expressed genes in patients with acute aortic dissection

Background

Acute aortic dissection (AAD) is a life-threatening condition with high mortality and a relatively unclarified pathophysiological mechanism. Although differentially expressed genes in AAD have been recognized, interactions between these genes remain poorly defined. This study was conducted to gain a better understanding of the molecular mechanisms underlying AAD and to support the future development of a clinical test for monitoring patients at high risk.

Materials and Methods

Aortic tissue was collected from 19 patients with AAD (mean age 61.7 ± 13.1 years), and from eight other patients (mean age 32.9 ± 12.2 years) who carried the mutated gene for Marfan syndrome (MS). Six patients (mean age 56.7 ± 12.3 years) served as the control group. The PIQOR^TM Immunology microarray with 1076 probes in quadruplicates was utilized; the differentially expressed genes were analysed in a MedScan search using Pathway Assist software. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and protein analysis were performed.

Results

Interactions of MS fibrillin-1 (FBN1) in the MedScan pathway analysis showed four genes, fibulin-1 (FBLN1), fibulin-2 (FBLN2), decorin (DCN) and microfibrillar associated protein 5 (MFAP5), which were differentially expressed in all tissue from AAD. The validation of these genes by qRT-PCR revealed a minimum of three-fold downregulation of FBLN1 (0.5 ± 0.4 vs. 6.1 ± 2.3 fold, p = 0.003) and of DCN (2.5 ± 1.0 vs. 8.5 ± 4.7 fold, p = 0.04) in AAD compared to MS and control samples.

Conclusions

Downregulation of fibrillin-1 (FBN1) may weaken extracellular components in the aorta and/or interfer with the transmission of cellular signals and eventually cause AAD. Additional research on these four identified genes can be a starting point to develop a diagnostic tool.

Expression profiles in surgically-induced carotid stenosis: a combined transcriptomic and proteomic investigation

Vascular injury aimed at stenosis removal induces local reactions often leading to restenosis. The aim of this study was a concerted transcriptomic-proteomics analysis of molecular variations in a model of rat carotid arteriotomy, to dissect the molecular pathways triggered by vascular surgical injury and to identify new potential anti-restenosis targets. RNA and proteins extracted from inbred Wistar Kyoro (WKY) rat carotids harvested 4 hrs, 48 hrs and 7 days after arteriotomy were analysed by Affymetrix rat microarrays and by bidimensional electrophoresis followed by liquid chromatography and tandem mass spectrometry, using as reference the RNA and the proteins extracted from uninjured rat carotids. Results were classified according to their biological function, and the most significant Kyoro Encyclopedia of Genes and Genomes (KEGG) pathways were identified. A total of 1163 mRNAs were differentially regulated in arteriotomy-injured carotids 4 hrs, 48 hrs and 7 days after injury (P < 0.0001, fold-change > or =2), while 48 spots exhibited significant changes after carotid arteriotomy (P < 0.05, fold-change > or =2). Among them, 16 spots were successfully identified and resulted to correspond to a set of 19 proteins. mRNAs were mainly involved in signal transduction, oxidative stress/inflammation and remodelling, including many new potential targets for limitation of surgically induced (re)stenosis (e.g. Arginase I, Kruppel like factors). Proteome analysis confirmed and extended the microrarray data, revealing time-dependent post-translational modifications of Hsp27, haptoglobin and contrapsin-like protease inhibitor 6, and the differential expression of proteins mainly involved in contractility. Transcriptomic and proteomic methods revealed functional categories with different preferences, related to the experimental sensitivity and to mechanisms of regulation. The comparative analysis revealed correlation between transcriptional and translational expression for 47% of identified proteins. Exceptions from this correlation confirm the complementarities of these approaches.

The role of the adventitia in vascular inflammation

Traditional concepts of vascular inflammation are considered "inside-out" responses centered on the monocyte adhesion and lipid oxidation hypotheses. These mechanisms likely operate in concert, holding the central tenet that the inflammatory response is initiated at the luminal surface. However, growing evidence supports a new paradigm of an "outside-in" hypothesis, in which vascular inflammation is initiated in the adventitia and progresses inward toward the intima. Hallmarks of the outside-in hypothesis include population of the adventitia with exogenous cell types, including monocytes, macrophages, and lymphocytes, the phenotypic switch of adventitial fibroblasts into migratory myofibroblasts, and increased vasa vasorum neovascularization. The resident and migrating cells deposit collagen and matrix components, respond to and upregulate inflammatory chemokines and/or antigens, and regulate the local redox state of the adventitia. B cells and T cells generate local humoral immune responses against local antigen presentation by foam cells and antigen presenting cells. These events result in increased local expression of cytokines and growth factors, evoking an inflammatory response that propagates inward toward the intima. Ultimately, it appears that the basic mechanisms of cellular activation and migration in vascular inflammation are highly conserved across a variety of cardiovascular disease states and that major inflammatory events begin in the adventitia.