Low WSS Induces Intimal Thickening, while Large WSS Variation and Inflammation Induce Medial Thinning, in an Animal Model of Atherosclerosis

OBJECTIVE

Atherosclerotic plaque development in the arterial wall is the result of complex interaction between the wall's endothelial layer and blood hemodynamics. However, the interaction between hemodynamic parameters and inflammation in plaque evolution is not yet fully understood. The aim of the present study was to investigate the relation between wall shear stress (WSS) and vessel wall inflammation during atherosclerotic plaque development in a minipig model of carotid stenosis.

METHODS

A surgical procedure was performed to create left common carotid artery stenosis by placement of a perivascular cuff in minipigs under atherogenic diet. Animals were followed up on 3T MRI, 1 week after surgery and 3, 6, and 8 months after initiation of the diet. Computational fluid dynamics simulation estimated WSS distribution for the first imaging point. Vascular geometries were co-registered for direct comparison of plaque development and features (Gadolinium- and USPIO-Contrast Enhanced MRI, for permeability and inflammation respectively) with the initial WSS. Histological analysis was performed and sections were matched to MR images, based on spatial landmarks.

RESULTS

Vessel wall thickening, permeability and inflammation were observed distally from the stenosis. They were eccentric and facing regions of normal wall thickness. Histological analysis confirmed eccentric plaque formation with lipid infiltration, intimal thickening and medial degradation. High phagocytic activity in the stenosis region was co-localized with high WSS, corresponding to intense medial degradation observed on histology samples.

CONCLUSION

Lower WSS promotes atherosclerotic plaque development distal to an induced stenosis. Vascular and perivascular inflammation locations were predominant in the high WSS stenosis segment, where medial thinning was the major consequence.

Serum macrophage migration inhibitory factor levels are associated with angiographically complex coronary lesions in patients with coronary artery disease

BACKGROUND

Rupture of vulnerable plaque with subsequent thrombus formation has been implicated as the most common pathogenic mechanism responsible for acute coronary syndrome (ACS). Angiographic coronary lesion complexity has been reported to reflect plaque vulnerability. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine and might be involved in the pathophysiology of atherosclerotic plaque destabilization.

OBJECTIVE

This study was designed to investigate if serum MIF levels are associated with angiographic coronary lesion complexity in patients with coronary artery disease (CAD).

MATERIALS AND METHODS

A total of 232 consecutive CAD patients and 76 controls were recruited. CAD patients were subdivided according to the presence of ACS (n=138) or stable angina pectoris (SAP) (n=98). Coronary lesion morphology was assessed by coronary angiography. Serum MIF levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

SAP patients had significantly higher serum MIF levels compared with healthy controls, and ACS patients had significantly higher serum MIF levels compared with SAP patients. In SAP patients, serum MIF levels were independently associated with the presence of complex coronary lesion. In ACS patients, serum MIF levels increased in conjunction with the extent of complex lesions.

CONCLUSIONS

Serum MIF levels are a potential biomarker for reflecting the presence and severity of angiographically complex coronary lesion in CAD patients.

Low eicosapentaenoic acid to arachidonic acid ratio is associated with thin-cap fibroatheroma determined by optical coherence tomography

BACKGROUND

A low eicosapentaenoic acid (EPA)/arachidonic acid (AA) ratio is known to be associated with cardiovascular events. However, the relationship between the EPA/AA ratio and coronary plaque vulnerability assessed by optical coherence tomography (OCT) has not been examined thoroughly. This study examined the relationship between the EPA/AA ratio and coronary plaque vulnerability assessed by OCT in patients with acute coronary syndrome (ACS).

METHODS

We evaluated 59 ACS patients who had undergone percutaneous coronary intervention using OCT. We divided them into 2 groups according to OCT findings-those with and without thin-cap fibroatheroma (TCFA)-and compared the EPA/AA ratio between the groups.

RESULTS

We identified 32 and 27 patients with and without TCFA, respectively. The EPA/AA ratio was significantly lower in patients with TCFA than in those without TCFA [0.35, interquartile range (0.21-0.44) vs. 0.54, interquartile range (0.42-0.70); p<0.001]. In multivariate logistic regression analysis, the EPA/AA ratio was an independent predictor of TCFA (odds ratio, 0.09; 95% confidence interval, 0.007-0.99; p=0.049). The EPA/AA ratio and fibrous cap thickness showed a significant positive correlation (Spearman ρ=0.46; p<0.001). Furthermore, receiver operating characteristic curve analysis showed that an EPA/AA ratio<0.46 could predict TCFA (81.3%, sensitivity; 74.1%, specificity).

CONCLUSIONS

A low serum EPA/AA ratio is significantly associated with coronary plaque vulnerability assessed by OCT in ACS patients.

Identification and characterization of novel serum microRNAs in unstable angina pectoris and subclinical atherosclerotic patients

BACKGROUND

MicroRNAs (miRNAs) are involved in cardiac developmental and pathological processes, and serum profile is useful for identifying novel miRNAs.

METHODS AND RESULTS

Serum samples were collected from unstable angina pectoris (UAP) and subclinical atherosclerotic (AS) patients. Solexa sequencing was used to predict novel miRNAs in 15 control individuals, 15 AS patients and 15 UAP patients. After bioinformatics analysis and filtering out in the newest version of miRbase (version 20.0), three novel miRNAs were validated in 80 control individuals, 80 AS patients and 80 UAP patients by quantitative reverse transcriptase polymerase chain reaction. Two of the three novel microRNAs (N1 and N3) were expressed at the highest levels in the AS group. N1 had an area under curve (AUC) of 0.811 (95% confidence interval 0.743-0.880) for AS. N3 showed a moderate separation with an area under curve (AUC) of 0.748 (95% confidence interval 0.664-0.833) for AS. Combined the two novel microRNAs can significantly distinguish AS from control.

CONCLUSIONS

Three novel miRNAs were identified by Solexa sequencing and two of them may be new potential predictors for arthrosclerosis.

Thrombosis formation on atherosclerotic lesions and plaque rupture

Atherosclerosis is a silent chronic vascular pathology that is the cause of the majority of cardiovascular ischaemic events. The evolution of vascular disease involves a combination of endothelial dysfunction, extensive lipid deposition in the intima, exacerbated innate and adaptive immune responses, proliferation of vascular smooth muscle cells and remodelling of the extracellular matrix, resulting in the formation of an atherosclerotic plaque. High-risk plaques have a large acellular lipid-rich necrotic core with an overlying thin fibrous cap infiltrated by inflammatory cells and diffuse calcification. The formation of new fragile and leaky vessels that invade the expanding intima contributes to enlarge the necrotic core increasing the vulnerability of the plaque. In addition, biomechanical, haemodynamic and physical factors contribute to plaque destabilization. Upon erosion or rupture, these high-risk lipid-rich vulnerable plaques expose vascular structures or necrotic core components to the circulation, which causes the activation of tissue factor and the subsequent formation of a fibrin monolayer (coagulation cascade) and, concomitantly, the recruitment of circulating platelets and inflammatory cells. The interaction between exposed atherosclerotic plaque components, platelet receptors and coagulation factors eventually leads to platelet activation, aggregation and the subsequent formation of a superimposed thrombus (i.e. atherothrombosis) which may compromise the arterial lumen leading to the presentation of acute ischaemic syndromes. In this review, we will describe the progression of the atherosclerotic lesion along with the main morphological characteristics that predispose to plaque rupture, and discuss the multifaceted mechanisms that drive platelet activation and subsequent thrombus formation. Finally, we will consider the current scientific challenges and future research directions.

Obesity and cardiovascular outcomes: a review

The prevalence of obesity is increasing at an epidemic rate globally with more than 1 billion adults overweight and at least 300 million of them clinically obese. This is expected to rise further in the next 20 to 30 years. Obesity is known to be an independent risk factor for serious health conditions, including hypertension, type 2 diabetes, and cardiovascular diseases. Given the association of obesity with cardiovascular disease, it could be speculated that obese individuals would have adverse outcomes after a cardiovascular event compared to those with normal body mass index (BMI). However, various studies have reported a paradoxical U-shaped relationship between obesity and mortality from various diseases, including myocardial infarction and heart failure, suggesting that patients with higher BMI have similar or lower short- and long-term mortality rates. This phenomenon has been termed the 'obesity paradox' or 'reverse epidemiology'. The goal of this review is to evaluate the potential mechanisms behind the obesity paradox and its implications.

Effects of mechanical properties and atherosclerotic artery size on biomechanical plaque disruption - mouse vs. human

Mouse models of atherosclerosis are extensively being used to study the mechanisms of atherosclerotic plaque development and the results are frequently extrapolated to humans. However, major differences have been described between murine and human atherosclerotic lesions and the determination of similarities and differences between these species has been largely addressed recently. This study takes over and extends previous studies performed by our group and related to the biomechanical characterization of both mouse and human atherosclerotic lesions. Its main objective was to determine the distribution and amplitude of mechanical stresses including peak cap stress (PCS) in aortic vessels from atherosclerotic apoE(-/-) mice, in order to evaluate whether such biomechanical data would be in accordance with the previously suggested lack of plaque rupture in this model. Successful finite element analysis was performed from the zero-stress configuration of aortic arch sections and mainly indicated (1) the modest role of atherosclerotic lesions in the observed increase in residual parietal stresses in apoE(-/-) mouse vessels and (2) the low amplitude of murine PCS as compared to humans. Overall, the results from the present study support the hypothesis that murine biomechanical properties and artery size confer less propensity to rupture for mouse lesions in comparison with those of humans.

MicroRNA-containing microvesicles regulating inflammation in association with atherosclerotic disease

In addition to intracellular organelles, eukaryotic cells contain extracellular organelles which are released, or shed, into the microenvironment. In practice, most human studies have examined mixed populations containing both exosomes and shedding microvesicles (also called ectosomes or microparticles); only a few studies have rigorously distinguished between the two. Accordingly, in this review, exosomes and shedding microvesicles are collectively called microvesicles. The first aim of this review was to discuss the role of microvesicles in cell-to-cell communication in general and in specific interactions between cells in chronic inflammation associated with atherosclerotic disease. Hereby, we focused on cell-specific microvesicles derived from platelets, endothelial cells and monocyte and monocyte-derived cells. The latter were also found to be associated with inflammation in obesity and type 2 diabetes prior to atherosclerotic disease, and cancer. Our second aim was to discuss specific changes in microvesicle content in relation with inflammation associated with metabolic and atherosclerotic disease, and cancer. Because many studies supported the putative diagnostic value of microRNAs, we emphasized therein changes in microRNA content rather than protein or lipid content. The most interesting microRNAs in inflammatory microvesicles in association with metabolic and cardiovascular diseases were found to be the let-7 family, miR-17/92 family, miR-21, miR-29, miR-126, miR-133, miR-146, and miR-155. These data warrant further investigation of the potential of microvesicles as putative biomarkers and as novel carriers for the cell-specific transfer of microRNAs and other therapeutic agents.