Heterogeneity of atherosclerotic plaque characteristics in human coronary artery disease: A three-dimensional intravascular ultrasound study

Epigenetic Control of Vascular Smooth Muscle Cell Function in Atherosclerosis: A Role for DNA Methylation

Atherosclerosis is a complex vascular inflammatory disease in which multiple cell types are involved, including vascular smooth muscle cells (VSMCs). In response to vascular injury and inflammatory stimuli, VSMCs undergo a "phenotypic switching" characterized by extracellular matrix secretion, loss of contractility, and abnormal proliferation and migration, which play a key role in the progression of atherosclerosis. DNA methylation modification is an important epigenetic mechanism that plays an important role in atherosclerosis. Studies investigating abnormal DNA methylation in patients with atherosclerosis have determined a specific DNA methylation profile, and proposed multiple pathways and genes involved in the etiopathogenesis of atherosclerosis. Recent studies have also revealed that DNA methylation modification controls VSMC function by regulating gene expression involved in atherosclerosis. In this review, we summarize the recent advances regarding the epigenetic control of VSMC function by DNA methylation in atherosclerosis and provide insights into the development of VSMC-centered therapeutic strategies.

Self-oxygenation mesoporous MnO2 nanoparticles with ultra-high drug loading capacity for targeted arteriosclerosis therapy

Atherosclerosis (AS) is a leading cause of vascular diseases that severely threats the human health due to the lack of efficient therapeutic methods. During the development and progress of AS, macrophages play critical roles, which are polarized into pro-inflammatory M1 phenotype to excrete abundant cytokines and overproduce reactive oxygen species (ROS), and take up excess amount of lipid to form foam cells. In this work, we developed a MnO₂-based nanomedicine to re-educate macrophages for targeting AS therapy. The MnO₂ was one-pot synthesized under mild condition, showing intrinsic catalase-mimic activity for self-oxygenation by using endogenous H₂O₂ as substrate. Moreover, the mesoporous structure as well as the abundant metal coordination sites in MnO₂ structure facilitated the loading of an anti-AS drug of curcumin (Cur), achieving extraordinarily high drug loading capacity of 54%. Cur displayed a broad spectrum of anti-oxidant and anti-inflammatory capabilities to repolarize M1 macrophages into M2 phenotype, and the catalytic MnO₂ recovered the function of lipid efflux transporter to remove lipid from cells by suppressing HIF-1α. Collectively, the nanocarrier and the payload drug functioned as an all-active nanoplatform to synergistically alleviate the syndromes of AS. In ApoE−/− mice model, the nanosystem could significantly prolong the circulation half-life of Cur by sixfold, and enhance drug accumulation in atherosclerotic lesion by 3.5-fold after intravenous injection by virtue of surface hyaluronic acid (HA) modification. As a result, a robust anti-AS efficacy was achieved as evidenced by the decrease of atherosclerotic lesion, plaque area, lipid level.

Epigenetic Regulation of Vascular Smooth Muscle Cell Phenotype Switching in Atherosclerotic Artery Remodeling: A Mini-Review

Atherosclerosis is a chronic inflammatory disease characterized by extensive remodeling of medium and large-sized arteries. Inward remodeling (=lumen shrinkage) of the vascular walls is the underlying cause for ischemia in target organs. Therefore, inward remodeling can be considered the predominant feature of atherosclerotic pathology. Outward remodeling (=lumen enlargement) is a physiological response compensating for lumen shrinkage caused by neointimal hyperplasia, but as a pathological response to changes in blood flow, outward remodeling leads to substantial arterial wall thinning. Thinned vascular walls are prone to rupture, and subsequent thrombus formation accounts for the majority of acute cardiovascular events. Pathological remodeling is driven by inflammatory cells which induce vascular smooth muscle cells to switch from quiescent to a proliferative and migratory phenotype. After decades of intensive research, the molecular mechanisms of arterial remodeling are starting to unfold. In this mini-review, we summarize the current knowledge of the epigenetic and transcriptional regulation of vascular smooth muscle cell phenotype switching from the contractile to the synthetic phenotype involved in arterial remodeling and discuss potential therapeutic options.

Artificial intelligence in personalized cardiovascular medicine and cardiovascular imaging

The collection of large, heterogeneous electronic datasets and imaging from patients with cardiovascular disease (CVD) has lent itself to the use of sophisticated analysis using artificial intelligence (AI). AI techniques such as machine learning (ML) are able to identify relationships between data points by linking input to output variables using a combination of different functions, such as neural networks. In cardiovascular medicine, this is especially pertinent for classification, diagnosis, risk prediction and treatment guidance. Common cardiovascular data sources from patients include genomic data, cardiovascular imaging, wearable sensors and electronic health records (EHR). Leveraging AI in analysing such data points: (I) for clinicians: more accurate and streamlined image interpretation and diagnosis; (II) for health systems: improved workflow and reductions in medical errors; (III) for patients: promoting health with further education and promoting primary and secondary cardiovascular health prevention. This review addresses the need for AI in cardiovascular medicine by reviewing recent literature in different cardiovascular imaging modalities: electrocardiography, echocardiography, cardiac computed tomography, cardiac nuclear imaging, and cardiac magnetic resonance (CMR) imaging as well as the role of EHR. This review aims to conceptulise these studies in relation to their clinical applications, potential limitations and future opportunities and directions.

The relationship between carotid and coronary calcification in patients with coronary artery disease

BACKGROUND

Atherosclerosis is a multi-system pathology with heterogeneous involvement. We aimed to investigate the relationship between the presence and severity of carotid and coronary calcification in a group of patients with coronary artery disease.

METHODS

Sixty-three patients presenting with unstable angina or positive stress test for myocardial ischaemia were enrolled in this study. All patients underwent CT scanning of the carotid and coronary arteries using the conventional protocol and Agatston scoring system. Risk factors for atherosclerosis were also analyzed for correlation with the extent of arterial calcification.

RESULTS

Total coronary artery calcium score (CAC) was several times higher than total carotid calcium score (1274 (1018) vs 6 (124), p = 0·0001, respectively). The left carotid calcium score correlated strongly with the right carotid calcium score (rho = 0·69, p < 0·0001). The total CAC score correlated modestly with the total carotid calcium score (rho = 0·34, p = 0·007), in particular with left carotid score (rho = 0·38, p = 0·002), but not with the right carotid score. The left coronary calcium score correlated with the right coronary calcium score (rho = 0·35, p = 0·004), left carotid calcium score (rho = 0·33, p = 0·007) and left carotid calcium score at the bifurcation (rho = 0·34, p = 0·006). While hypertension correlated with carotid calcium score, diabetes and dyslipidaemia correlated with left CAC score.

CONCLUSION

In patients with coronary disease, the carotid calcification pattern appeared to be similar between the right and left system in contrast to that of the coronary arteries. CAC correlated only modestly with the carotid score, despite being significantly higher. Hypertension was related to carotid calcium score while diabetes and dyslipidaemia correlated with coronary calcification.

Nanoparticle-Aided Characterization of Arterial Endothelial Architecture during Atherosclerosis Progression and Metabolic Therapy

Atherosclerosis is associated with a compromised endothelial barrier, facilitating the accumulation of immune cells and macromolecules in atherosclerotic lesions. In this study, we investigate endothelial barrier integrity and the enhanced permeability and retention (EPR) effect during atherosclerosis progression and therapy in Apoe-/- mice using hyaluronan nanoparticles (HA-NPs). Utilizing ultrastructural and en face plaque imaging, we uncover a significantly decreased junction continuity in the atherosclerotic plaque-covering endothelium compared to the normal vessel wall, indicative of disrupted endothelial barrier. Intriguingly, the plaque advancement had a positive effect on junction stabilization, which correlated with a 3-fold lower accumulation of in vivo administrated HA-NPs in advanced plaques compared to early counterparts. Furthermore, by using super-resolution and correlative light and electron microscopy, we trace nanoparticles in the plaque microenvironment. We find nanoparticle-enriched endothelial junctions, containing 75% of detected HA-NPs, and a high HA-NP accumulation in the endothelium-underlying extracellular matrix, which suggest an endothelial junctional traffic of HA-NPs to the plague. Finally, we probe the EPR effect by HA-NPs in the context of metabolic therapy with a glycolysis inhibitor, 3PO, proposed as a vascular normalizing strategy. The observed trend of attenuated HA-NP uptake in aortas of 3PO-treated mice coincides with the endothelial silencing activity of 3PO, demonstrated in vitro. Interestingly, the therapy also reduced the plaque inflammatory burden, while activating macrophage metabolism. Our findings shed light on natural limitations of nanoparticle accumulation in atherosclerotic plaques and provide mechanistic insight into nanoparticle trafficking across the atherosclerotic endothelium. Furthermore, our data contribute to the rising field of endothelial barrier modulation in atherosclerosis.

Impact of Coronary Plaque Vulnerability on Acute Cardiovascular Events – Design of a CT-based 2-year Follow-up Study

With coronary artery disease (CAD) projected to remain the leading cause of global mortality, prevention strategies seem to be the only effective approach able to reduce the burden and improve mortality and morbidity. At this moment, diagnostic strategies focus mainly on symptomatic patients, ignoring the occurrence of major cardiovascular events as the only manifestation of CAD. As two thirds of fatal myocardial infarction are resulting from plaque rupture, an approach based on the “vulnerable plaque” concept is mandatory in order to improve patient diagnosis, treatment, and, by default, prognosis. Given that the main studies focus on a plaque-centered approach, this is a prospective observational study that will perform a complex assessment of the features that characterize unstable coronary lesions, in terms of both local assessment via specific coronary computed tomography angiography markers of coronary plaque vulnerability and systemic approach based on serological markers of systemic inflammation in patients proved to be “vulnerable” by developing acute cardiovascular events.

Analytic Approaches for the Treatment of Hyperhomocysteinemia and Its Impact on Vascular Disease

Homocysteine is an intermediary metabolite in the methionine cycle. Accumulation of homocysteine is caused either by mutation of relevant genes or by nutritional depletion of related vitamin(s). This review covers the historical background of hyperhomocysteinemia in which indispensable subjects in relation to underlying pathophysiological processes are discussed with the view of metabolism and genetics of folate and methionine cycles. This review emphasizes the unique role of homocysteine that is clearly distinct from other risk factors, particularly cholesterol in the development of vascular disease. The critical issue in understanding the role of homocysteine is the relation with plasma folic acid. The majority of subjects with homocysteine > 15 μmol/L exhibit plasma folate < 9 nmol/ L, indicating that depletion of folate is the main cause of hyperhomocysteinemia irrespective of the presence or absence of vascular disease. Furthermore, only the group of subjects with homocysteine levels > 15 μmol/L demonstrated a higher prevalence of vascular disease. Analytic approaches to treat hyperhomocysteinemia are discussed in which stepwise administration with nutritional doses of folic acid, 5-methyitetrahydrofolate (5-MTHF), and betaine is provided singly or by combined manner based on clinical and laboratory evaluations. Whether correction of hyperhomocysteinemia is able to prevent the development of homocysteine-associated vascular disease remains an unresolved issue. The review discussed a biochemical and mechanistic approach to resolve questions involved in the relation between homocysteine and the development of atherosclerotic vascular disease.

Proteomics and multivariate modelling reveal sex-specific alterations in distinct regions of human carotid atheroma

Background

Atherosclerotic lesions are comprised of distinct regions with different proteomic profiles. Men and women develop differences in lesion phenotype, with lesions from women generally being more stable and less prone to rupture. We aimed to investigate the differences in proteomic profiles between sexes, including distinct lesion regions, to identify altered proteins that contribute to these differences observed clinically.

Methods

Carotid endarterectomy samples (ten men/ten women) were obtained, and intraplaque biopsies from three distinct regions (internal control, fatty streak and plaque) were analysed by tandem-mass spectrometry. Multivariate statistical modelling, using orthogonal partial least square-discriminant analysis, was used to discriminate the proteomes between men and women.

Results

Multivariate discriminant modelling revealed proteins from 16 functional groups that displayed sex-specific associations. Additional statistics revealed ten proteins that display region-specific alterations when comparing sexes, including proteins related to inflammatory response, response to reactive oxygen species, complement activation, transport and blood coagulation. Transport protein afamin and blood coagulation proteins antithrombin-III and coagulation factor XII were significantly increased in plaque region from women. Inflammatory response proteins lysozyme C and phospholipase A2 membrane-associated were significantly increased in plaque region from men. Limitations with this study are the small sample size, limited patient information and lack of complementary histology to control for cell type differences between sexes.

Conclusions

This pilot study, for the first time, utilises a multivariate proteomic approach to investigate sexual dimorphism in human atherosclerotic tissue, and provides an essential proteomic platform for further investigations to help understand sexual dimorphism and plaque vulnerability in atherosclerosis.

Electronic supplementary material

The online version of this article (10.1186/s13293-018-0217-3) contains supplementary material, which is available to authorized users.

Evolving understanding of the heterogeneous natural history of individual coronary artery plaques and the role of local endothelial shear stress

PURPOSE OF REVIEW

Anatomic and morphologic features of high-risk coronary plaque have been identified by novel imaging modalities, but it has been less clear which ostensibly high-risk plaques will actually destabilize and cause a new cardiac event. Different plaques with different morphologies coexist within the same artery, but the impact of this heterogeneity on the natural history of coronary artery disease has not been extensively investigated.

RECENT FINDINGS

Coronary plaques exhibit remarkable heterogeneity of local morphological and blood-flow patterns, including endothelial shear stress (ESS), along their longitudinal axis, with important implications for the heterogeneous natural history of coronary disease. The natural history of individual plaques is considerably divergent, with most plaques, even ostensibly high-risk plaques, becoming quiescent and only a minority progressing to destabilize and precipitate a new clinical event. Local areas of proinflammatory low ESS appear to be an important condition for plaque destabilization.

SUMMARY

Characterization of an individual atherosclerotic plaque based on a snapshot of morphological features at a specific location, such as the minimal lumen diameter, may not be sufficiently comprehensive to accurately reflect the risk associated with that plaque. A detailed assessment of both anatomical and functional pathobiologic characteristics in the longitudinal plaque dimension may enhance our understanding of atherosclerosis progression and improve the management of individual patients with coronary artery disease.

Non-Invasive Identification of Vulnerable Atherosclerotic Plaques Using Texture Analysis in Ultrasound Carotid Elastography: An In Vivo Feasibility Study Validated by Magnetic Resonance Imaging

The aims of this study were to quantify the textural information of strain rate images in ultrasound carotid elastography and evaluate the feasibility of using the textural features in discriminating stable and vulnerable plaques with magnetic resonance imaging as an in vivo reference. Ultrasound radiofrequency data were acquired in 80 carotid plaques from 52 patients, mainly in the longitudinal imaging view, and axial strain rate images were estimated with an ultrasound carotid elastography technique based on an optical flow algorithm. Four textural features of strain rate images-contrast, homogeneity, correlation and angular second moment-were derived based on the gray-level co-occurrence matrix in plaque regions to quantify the deformation distribution pattern. Conventional elastographic indices based on the magnitude of the absolute strain rate, such as the maximum, mean, median, standard deviation and 99th percentile of the axial strain rate, were also obtained for comparison. Composition measurement with magnetic resonance imaging identified 30 plaques as vulnerable and the other 50 as stable. The four textural features, as well as the magnitude of strain rate images, significantly differed between the two groups of plaques. The best performing features for plaque classification were found to be the contrast and 99th percentile of the absolute strain rate, with a comparative area under the receiver operating characteristic curve of 0.81; a slightly higher maximum accuracy of plaque classification can be achieved by the textural feature of contrast (83.8% vs. 81.3%). The results indicate that the use of texture analysis in plaque classification is feasible and that larger local deformations and higher level of complexity in deformation patterns (associated with the elastic or stiffness heterogeneity of plaque tissues) are more likely to occur in vulnerable plaques.

Concise Review of Optical Coherence Tomography in Clinical Practice

Optical coherence tomography (OCT) is a novel image modality with higher resolution in the catheterization laboratory. It can differentiate tissue characteristics and provide detailed information, including dissection, tissue prolapse, thrombi, and stent apposition. In this study, we comprehensively reviewed the current pros and cons of OCT clinical applications and presented our clinical experiences associated with the advantages and limitations of this new imaging modality.

Distinctive proteomic profiles among different regions of human carotid plaques in men and women

The heterogeneity of atherosclerotic tissue has limited comprehension in proteomic and metabolomic analyses. To elucidate the functional implications, and differences between genders, of atherosclerotic lesion formation we investigated protein profiles from different regions of human carotid atherosclerotic arteries; internal control, fatty streak, plaque shoulder, plaque centre, and fibrous cap. Proteomic analysis was performed using 2-DE with MALDI-TOF, with validation using nLC-MS/MS. Protein mapping of 2-DE identified 52 unique proteins, including 15 previously unmapped proteins, of which 41 proteins were confirmed by nLC-MS/MS analysis. Expression levels of 18 proteins were significantly altered in plaque regions compared to the internal control region. Nine proteins showed site-specific alterations, irrespective of gender, with clear associations to extracellular matrix remodelling. Five proteins display gender-specific alterations with 2-DE, with two alterations validated by nLC-MS/MS. Gender differences in ferritin light chain and transthyretin were validated using both techniques. Validation of immunohistochemistry confirmed significantly higher levels of ferritin in plaques from male patients. Proteomic analysis of different plaque regions has reduced the effects of plaque heterogeneity, and significant differences in protein expression are determined in specific regions and between genders. These proteomes have functional implications in plaque progression and are of importance in understanding gender differences in atherosclerosis.

Effect of the local hemodynamic environment on the de novo development and progression of eccentric coronary atherosclerosis in humans: insights from PREDICTION

BACKGROUND

Eccentric distribution of atheroma has been associated with plaques likely to rupture and cause an acute coronary syndrome, but the factors responsible for the development of eccentricity remain unknown. Endothelial shear stress (ESS) drives plaque formation. We aimed to investigate the role of the local ESS characteristics in the de novo development and progressive worsening of plaque eccentricity in humans.

METHODS

Vascular profiling (3-vessel 3D coronary reconstruction by angiography/intravascular ultrasound, and blood flow simulation for ESS computation) was performed in 374 patients at baseline & 6-10 months follow-up. At baseline, we identified (i) disease-free segments (n=2157), and (ii) diseased regions of luminal obstructions (n=408).

RESULTS

In disease-free regions, baseline low ESS magnitude (p<0.001), marked ESS circumferential heterogeneity (p=0.001), and their interaction (p=0.026) were associated with an increased probability of de novo eccentric plaque formation at follow-up. In diseased regions, baseline low ESS (odds ratio [OR]: 2.33, p=0.003) and large plaque burden (OR: 2.46, p=0.002) were independent predictors of substantially increasing plaque eccentricity index with worsening lumen encroachment. This combined outcome was more frequent in obstructions with both features vs. all others (33 vs. 12%; p<0.001). The incidence of percutaneous coronary intervention in worsening obstructions with increasing plaque eccentricity was higher (13.3 vs. 4.3%, p=0.011).

CONCLUSIONS

The local hemodynamic environment has a critical effect on the development of eccentric coronary plaques at both an early and advanced stage of atherosclerosis. Local ESS assessment could help in predicting sites prone to plaque disruption and acute coronary syndromes in humans.

The mononuclear phagocyte system in homeostasis and disease: a role for heme oxygenase-1

SIGNIFICANCE

Heme oxygenase-1 (HO-1) is a potential therapeutic target in many diseases, especially those mediated by oxidative stress and inflammation. HO-1 expression appears to regulate the homeostatic activity and distribution of mononuclear phagocytes (MP) in lymphoid tissue under physiological conditions. It also regulates the ability of MP to modulate the inflammatory response to tissue injury.

RECENT ADVANCES

The induction of HO-1 within MP-particularly macrophages and dendritic cells-modulates the effector functions that they acquire after activation. These effector functions include cytokine production, surface receptor expression, maturation state, and polarization toward a pro- or anti-inflammatory phenotype. The importance of HO-1 in MP is emphasized by their expression of specific receptors that primarily function to ingest heme-containing substrate and deliver it to HO-1.

CRITICAL ISSUES

MP are the first immunological responders to tissue damage. They critically affect the outcome of injury to many organ systems, yet few therapies are currently available to specifically target MP during disease pathogenesis. Elucidation of the role of HO-1 expression in MP may help to direct broadly applicable therapies to clinical use that are based on the immunomodulatory capabilities of HO-1.

FUTURE DIRECTIONS

Unraveling the complexities of HO-1 expression specifically within MP will more completely define how HO-1 provides cytoprotection in vivo. The use of models in which HO-1 expression is specifically modulated in bone marrow-derived cells will allow for a more complete characterization of its immunoregulatory properties.

Contrast-enhanced 3T high-resolution MR imaging in symptomatic atherosclerotic basilar artery stenosis

BACKGROUND AND PURPOSE

Contrast-enhanced 3T high-resolution MR imaging can be used to determine the wall enhancement pattern of the basilar artery in symptomatic atherosclerotic stenosis. We used this method to explore the relationship between wall enhancement and both recent infarction in the territory of the stenotic BA and subsequent ischemic events associated with the stenotic BA.

MATERIALS AND METHODS

Sixty patients with symptomatic atherosclerotic BA stenosis ≥70% were enrolled consecutively. HR-MRI of cross-sectional BAs was obtained before and after contrast media injection, and wall enhancement indices were calculated for sections proximal to, at, and distal to the site of maximal luminal narrowing. DWI of the brain was performed to determine the presence of recent infarction.

RESULTS

Images from 56 patients were suitable for analysis. Thirty-three patients underwent stent placement for the stenotic BA, and 23 patients underwent conservative medical treatment with antiplatelet agents and risk-factor control. All 23 patients with medical treatment had a 12-month follow-up. Greater wall enhancement was seen in the section proximal to the MLN section in both patients with recent infarction (74 ± 65% versus 44 ± 44%; P = .046) and in patients with subsequent ischemic events (100 ± 57% versus 44 ± 44%; P = .014).

CONCLUSIONS

Greater wall enhancement proximal to the MLN site correlates with recent infarction in the territory of the stenotic BA and subsequent ischemic events associated with the stenotic BA. Contrast-enhanced HR-MRI may serve as a noninvasive tool for risk stratification of BA atherosclerosis.