Asymptomatic carotid plaque rupture with unexpected thrombosis over a non-canonical vulnerable lesion

Impact of the environmental pollution on cardiovascular diseases: From epidemiological to molecular evidence

Environmental pollution poses a significant threat to human health, particularly concerning its impact on cardiovascular diseases (CVDs). This review synthesizes epidemiological and molecular evidence to elucidate the intricate relationship between environmental pollutants and CVDs. Epidemiological studies highlight the association between exposure to air, water, and soil pollutants and increased CVD risk, including hypertension, coronary artery disease, and stroke. Furthermore, molecular investigations unravel the underlying mechanisms linking pollutant exposure to CVD pathogenesis, such as oxidative stress, inflammation, endothelial dysfunction, and autonomic imbalance. Understanding these molecular pathways is crucial for developing targeted interventions and policy strategies to mitigate the adverse effects of environmental pollution on cardiovascular health. By integrating epidemiological and molecular evidence, this review provides insights into the complex interplay between environmental factors and CVDs, emphasizing the urgent need for comprehensive preventive measures and environmental policies to safeguard public health.

Developing Theoretical Models for Atherosclerotic Lesions: A Methodological Approach Using Interdisciplinary Insights

Atherosclerosis, a leading cause of cardiovascular disease, necessitates advanced and innovative modeling techniques to better understand and predict plaque dynamics. The present work presents two distinct hypothetical models inspired by different research fields: the logistic map from chaos theory and Markov models from stochastic processes. The logistic map effectively models the nonlinear progression and sudden changes in plaque stability, reflecting the chaotic nature of atherosclerotic events. In contrast, Markov models, including traditional Markov chains, spatial Markov models, and Markov random fields, provide a probabilistic framework to assess plaque stability and transitions. Spatial Markov models, visualized through heatmaps, highlight the spatial distribution of transition probabilities, emphasizing local interactions and dependencies. Markov random fields incorporate complex spatial interactions, inspired by advances in physics and computational biology, but present challenges in parameter estimation and computational complexity. While these hypothetical models offer promising insights, they require rigorous validation with real-world data to confirm their accuracy and applicability. This study underscores the importance of interdisciplinary approaches in developing theoretical models for atherosclerotic plaques.

Macrophage polarization and metabolism in atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of fatty deposits in the inner walls of vessels. These plaques restrict blood flow and lead to complications such as heart attack or stroke. The development of atherosclerosis is influenced by a variety of factors, including age, genetics, lifestyle, and underlying health conditions such as high blood pressure or diabetes. Atherosclerotic plaques in stable form are characterized by slow growth, which leads to luminal stenosis, with low embolic potential or in unstable form, which contributes to high risk for thrombotic and embolic complications with rapid clinical onset. In this complex scenario of atherosclerosis, macrophages participate in the whole process, including the initiation, growth and eventually rupture and wound healing stages of artery plaque formation. Macrophages in plaques exhibit high heterogeneity and plasticity, which affect the evolving plaque microenvironment, e.g., leading to excessive lipid accumulation, cytokine hyperactivation, hypoxia, apoptosis and necroptosis. The metabolic and functional transitions of plaque macrophages in response to plaque microenvironmental factors not only influence ongoing and imminent inflammatory responses within the lesions but also directly dictate atherosclerotic progression or regression. In this review, we discuss the origin of macrophages within plaques, their phenotypic diversity, metabolic shifts, and fate and the roles they play in the dynamic progression of atherosclerosis. It also describes how macrophages interact with other plaque cells, particularly T cells. Ultimately, targeting pathways involved in macrophage polarization may lead to innovative and promising approaches for precision medicine. Further insights into the landscape and biological features of macrophages within atherosclerotic plaques may offer valuable information for optimizing future clinical treatment for atherosclerosis by targeting macrophages.

Analysis of Risk Factors for Vulnerable Plaque Formation and Pathogenic in Carotid Artery

OBJECTIVES

The formation of vulnerable carotid artery plaque may be closely related to a single factor or caused by multiple factors. This paper discusses the pathogenic risk factors for vulnerable plaque in patients with severe internal carotid artery (ICA) stenosis who received endarterectomy through regression analysis.

MATERIALS AND METHODS

A total of 98 patients with a complete clinical and laboratory assessment underwent carotid endarterectomy. Metabolic syndrome (MetS) and MetS components, ICA plaque thickness and ICA peak systolic velocity, previous ischemic stroke or transient ischemic attack (TIA), and other risk factors were included in the pathogenic risk factor for vulnerable plaque. Univariate logistic regression analysis was used to determine vulnerable carotid plaque risk factors. If P <0.2, it was considered potential confounders. Binary logistic regression model was controlled for potential confounders.

RESULTS

Among the 98 patients, stable carotid plaques 38 (39%) and unstable carotid plaques 60 (61%), male 76 (77.6%) and female 22 (22.4%), and Han Chinese 68 (68.4%) and Mongols 30 (30.6%). Univariate logistic regression to P <0.2 has 6 risk factors, which are previous ischemic stroke or TIA, ICA peak systolic velocity, ICA plaque thickness, body mass index, total cholesterol, and alcohol consumption. The significant result of the binary logistic regression analysis was the previous ischemic stroke or TIA (OR=4.52; 95% CI, 1.67-12.09), P =0.003 and ICA peak systolic velocity (OR=1.01; 95% CI, 1.00-1.02), P =0.014.

CONCLUSIONS

The patients with previous ischemic stroke or TIA and higher ICA peak systolic velocity are associated with vulnerable plaque pathogenic features. There is no obligatory association between MetS and formation of carotid plaque vulnerability.

Clinical application of super sensitive microflow ultrasound on the detection of intraplaque neovascularization in patients with atheromatous carotid artery plaque

BACKGROUND

Contrast-enhanced ultrasound (CEUS) is a routine technique for detecting intraplaque neovascularization (IPN). However, the invasiveness and complexity of CEUS severely limit its clinical application. This article aims to investigate the application value of AngioPLUS (AP) technique in assessing IPN formation in patients with atheromatous (AS) carotid artery plaque.

METHODS

Patients diagnosed with carotid artery atherosclerosis combined plaque formation were recruited and their demographic characteristics including serum fasting blood glucose (FBG), triglyceride (TG), and low-density lipoprotein (LDL) were collected. AP was used to scoring intraplaque microvascular flow (IMVF), measuring the thickness and length of the plaque and determining the number of IPN of the plaque.

RESULTS

IMVF score evaluated by AP was positively correlated with plaque length, thickness, IPN number, serum TG, LDL and FBG levels in patients with carotid atherosclerosis with plaque. The evaluation results of CEUS score and IMVF classification detected by AP of plaques were consistent in patients with carotid atherosclerosis.

CONCLUSION

IMVF scoring by AP is a promising approach to assess IPN and plaque status in patients with atheromatous carotid artery plaque.

Imaging Approaches to the Diagnosis of Vascular Diseases

PURPOSE OF REVIEW

Vascular imaging is a complex field including numerous modalities and imaging markers. This review is focused on important and recent findings in atherosclerotic carotid artery plaque imaging with an emphasis on developments in magnetic resonance imaging (MRI) and computed tomography (CT).

RECENT FINDINGS

Recent evidence shows that carotid plaque characteristics and not only established measures of carotid plaque burden and stenosis are associated independently with cardiovascular outcomes. On carotid MRI, the presence of a lipid-rich necrotic core (LRNC) has been associated with incident cardiovascular disease (CVD) events independent of wall thickness, a traditional measure of plaque burden. On carotid MRI, intraplaque hemorrhage (IPH) presence has been identified as an independent predictor of stroke. The presence of a fissured carotid fibrous cap has been associated with contrast enhancement on CT angiography imaging. Carotid artery plaque characteristics have been associated with incident CVD events, and advanced plaque imaging techniques may gain additional prominence in the clinical treatment decision process.

High Sensitivity C-Reactive Protein Increases the Risk of Carotid Plaque Instability in Male Dyslipidemic Patients

Background: The aim of this study was to evaluate how the high sensitivity C-reactive protein (hs-CRP) values influence the risk of carotid plaque instability in association with other cardiovascular risk factors. Methods: One hundred and fifty-six carotid plaques from both symptomatic and asymptomatic patients requiring surgical carotid endarterectomy were retrospectively collected. According to the modified American Heart Association, atherosclerosis plaques have been histologically distinguished into unstable and stable. The following anamnestic and hematochemical data were also considered: age, gender, hypertension, diabetes mellitus, smoking habit, therapy, low-density lipoprotein (LDL)-C, kidney failure and hs-CRP. Results: The results of our study clearly show that high levels of hs-CRP significantly increase the carotid plaque instability in dyslipidemic patients. Specifically, a 67% increase of the risk of carotid plaque instability was observed in patients with high LDL-C. Therefore, the highest risk was observed in male dyslipidemic patients 2333 (95% CI 0.73–7.48) and in aged female patients 2713 (95% CI 0.14–53.27). Discussion: These data strongly suggest a biological relationship between the hs-CRP values and the alteration of lipidic metabolism mostly in male patients affected by carotid atherosclerosis. The measurement of hs-CRP might be useful as a potential screening tool in the prevention of atheroscletotic disease.

Effects of Risk Factors on In Situ Expression of Proinflammatory Markers Correlated to Carotid Plaque Instability

BACKGROUND AND AIMS

Several studies demonstrated a role of active chronic inflammatory infiltrate in carotid plaques progression suggesting a possible link between cardiovascular risk factors and inflammation-related plaque instability. The aim of this study is therefore to evaluate the possible effects of cardiovascular risk factors on in situ expression of proinflammatory markers associated with carotid plaque instability.

METHODS AND RESULTS

A tissue microarray containing carotid plaques from 36 symptomatic (major stroke or transient ischemic attack) and 37 asymptomatic patients was built. Serial sections were employed to evaluate the expression of some inflammatory markers by immunohistochemistry [CD3, CD4a, CD8, CD20, CD86, CD163, interleukin (IL)-2, IL-6, IL-17]. Immunohistochemical data were analyzed to study the possible associations between in situ expression of inflammatory biomarker and the main cardiovascular risk factors. Our data demonstrated that plaque instability is associated with the high in situ expression of some cytokines, such as IL-2, IL-6, IL-17. Besides the female sex, none of the risk factors analyzed showed a significant association between the in situ expression of these markers and unstable plaques. A significant increase of IL-6-positive and IL-17-positive cells was observed in unstable atheromatous plaques of female patients, as compared with unstable plaques of male patients.

CONCLUSIONS

Plaque destabilization is certainly correlated with the presence of the major cardiovascular risk factors, however, our results showed that, with the exception of sex, their action in the evolutive process of plaque instability seems rather nonspecific, favoring a general release of proinflammatory cytokines.

The risk of carotid plaque instability in patients with metabolic syndrome is higher in women with hypertriglyceridemia

Background

Metabolic syndrome certainly favors growth of carotid plaque; however, it is uncertain if it determines plaque destabilization. Furthermore, it is likely that only some components of metabolic syndrome are associated with increased risk of plaque destabilization. Therefore, we evaluated the effect of different elements of metabolic syndrome, individually and in association, on carotid plaques destabilization.

Methods

A total of 186 carotid endarterectomies from symptomatic and asymptomatic patients were histologically analysed and correlated with major cardiovascular risk factors.

Results

Metabolic syndrome, regardless of the cluster of its components, is not associated with a significant increase in risk of plaque destabilization, rather with the presence of stable plaques. The incidence of unstable plaques in patients with metabolic syndrome is quite low (43.9 %), when compared with that seen in the presence of some risk factors, but significantly increases in the subgroup of female patients with hypertriglyceridemia, showing an odds ratio of 3.01 (95% CI, 0.25–36.30).

Conclusions

Our data may help to identify patients with real increased risk of acute cerebrovascular diseases thus supporting the hypothesis that the control of hypertriglyceridemia should be a key point on prevention of carotid atherosclerotic plaque destabilization, especially in post-menopausal female patients.

Imaging atherosclerotic plaques by targeting Galectin-3 and activated macrophages using (89Zr)-DFO- Galectin3-F(ab')2 mAb

Rationale: The high expression of Galectin-3 (Gal3) in macrophages of atherosclerotic plaques suggests its participation in atherosclerosis pathogenesis, and raises the possibility to use it as a target to image disease severity in vivo. Here, we explored the feasibility of tracking atherosclerosis by targeting Gal3 expression in plaques of apolipoprotein E knockout (ApoE-KO) mice via PET imaging. Methods: Targeting of Gal3 in M0-, M1- and M2 (M2a/M2c)-polarized macrophages was assessed in vitro using a Gal3-F(ab')₂ mAb labeled with AlexaFluor®488 and ⁸⁹Zr- desferrioxamine-thioureyl-phenyl-isothiocyanate (DFO). To visualize plaques in vivo, ApoE-KO mice were injected i.v. with ⁸⁹Zr-DFO-Gal3-F(ab')₂ mAb and imaged via PET/CT 48 h post injection. Whole length aortas harvested from euthanized mice were processed for Sudan-IV staining, autoradiography, and immunostaining for Gal3, CD68 and α-SMA expression. To confirm accumulation of the tracer in plaques, ApoE-KO mice were injected i.v. with Cy5.5-Gal3-F(ab')₂ mAb, euthanized 48 h post injection, followed by cryosections of the body and acquisition of fluorescent images. To explore the clinical potential of this imaging modality, immunostaining for Gal3, CD68 and α-SMA expression were carried out in human plaques. Single cell RNA sequencing (scRNA-Seq) analyses were performed to measure LGALS3 (i.e. a synonym for Gal3) gene expression in each macrophage of several subtypes present in murine or human plaques. Results: Preferential binding to M2 macrophages was observed with both AlexaFluor®488-Gal3-F(ab')₂ and ⁸⁹Zr-DFO-Gal3-F(ab')₂ mAbs. Focal and specific ⁸⁹Zr-DFO-Gal3-F(ab')₂ mAb uptake was detected in plaques of ApoE-KO mice by PET/CT. Autoradiography and immunohistochemical analyses of aortas confirmed the expression of Gal3 within plaques mainly in macrophages. Moreover, a specific fluorescent signal was visualized within the lesions of vascular structures burdened by plaques in mice. Gal3 expression in human plaques showed similar Gal3 expression patterns when compared to their murine counterparts. Conclusions: Our data reveal that ⁸⁹Zr-DFO-Gal3-F(ab')₂ mAb PET/CT is a potentially novel tool to image atherosclerotic plaques at different stages of development, allowing knowledge-based tailored individual intervention in clinically significant disease.

The Paradox Effect of Calcification in Carotid Atherosclerosis: Microcalcification is Correlated with Plaque Instability

Background: this study aims to investigate the possible association among the histopathologic features of carotid plaque instability, the presence of micro- or macrocalcifications, the expression of in situ inflammatory biomarkers, and the occurrence of the major risk factors in this process in a large series of carotid plaques. Methods: a total of 687 carotid plaques from symptomatic and asymptomatic patients were collected. Histological evaluation was performed to classify the calcium deposits in micro or macrocalcifications according to their morphological features (location and size). Immunohistochemistry was performed to study the expression of the main inflammatory biomarkers. Results: results here reported demonstrated that calcifications are very frequent in carotid plaques, with a significant difference between the presence of micro- and macrocalcifications. Specifically, microcalcifications were significantly associated to high inflamed unstable plaques. Paradoxically, macrocalcifications seem to stabilize the plaque and are associated to a M2 macrophage polarization instead. Discussion: the characterization of mechanisms involved in the formation of carotid calcifications can lay the foundation for developing new strategies for the management of patients affected by carotid atherosclerosis. Data of this study could provide key elements for an exhaustive evaluation of carotid plaque calcifications allowing to establish the risk of associated clinical events.

Correlation between SHP-1 and carotid plaque vulnerability in humans

BACKGROUND

Advanced atherosclerotic plaques tend to indicate an increased risk of cerebral ischemic events. SH2 domain-containing protein tyrosine phosphatase 1 (SHP-1) is a class I classical nonreceptor protein tyrosine phosphatase associated with plaque stability, as shown by analysis of a Gene Expression Omnibus (GEO) dataset showing differences in mRNA levels. However, the correlation between SHP-1 and human carotid plaque stability at the protein level remains unclear.

METHODS AND RESULTS

Thirty-nine carotid plaque tissue samples were acquired from 39 carotid artery stenosis patients after carotid endarterectomy. Hematoxylin and eosin, Masson trichrome, and CD68 staining was performed for pathological characterization, and immunohistochemical staining for SHP-1 was carried out. Within stable and unstable plaques, SHP-1 mainly accumulated in the necrotic area, plaque shoulder, and fibrous cap, similar to the distribution of CD68. A quantitative analysis of SHP-1 was carried out. The relative SHP-1-positive cell area was higher in the vulnerable group than in the stable group (P < .001). The number of symptomatic patients in the vulnerable group was no greater than that in the stable group (P = .098). Moreover, the integrated optical density (IOD)/area of SHP-1 was significantly higher in the vulnerable group than in the stable group (P < .001). Besides, SHP-1 colocalized with CD68 and vascular cell adhesion protein 1(VCAM-1).

CONCLUSIONS

We demonstrate that SHP-1 expression increases during carotid atherosclerotic plaque progression. The protein expression of SHP-1 was related to an increase in plaque instability in not only symptomatic but also asymptomatic patients with carotid artery stenosis. SHP-1 may play a role in atherosclerosis progression by macrophage polarization-mediated efferocytosis. Furthermore, SHP-1 may become a promising biomarker for plaque vulnerability in the future.

Calcification in Atherosclerotic Plaque Vulnerability: Friend or Foe?

Calcification is a clinical marker of atherosclerosis. This review focuses on recent findings on the association between calcification and plaque vulnerability. Calcified plaques have traditionally been regarded as stable atheromas, those causing stenosis may be more stable than non-calcified plaques. With the advances in intravascular imaging technology, the detection of the calcification and its surrounding plaque components have evolved. Microcalcifications and spotty calcifications represent an active stage of vascular calcification correlated with inflammation, whereas the degree of plaque calcification is strongly inversely related to macrophage infiltration. Asymptomatic patients have a higher content of plaque calcification than that in symptomatic patients. The effect of calcification might be biphasic. Plaque rupture has been shown to correlate positively with the number of spotty calcifications, and inversely with the number of large calcifications. There may be certain stages of calcium deposition that may be more atherogenic. Moreover, superficial calcifications are independently associated with plaque rupture and intraplaque hemorrhage, which may be due to the concentrated and asymmetrical distribution of biological stress in plaques. Conclusively, calcification of differential amounts, sizes, shapes, and positions may play differential roles in plaque homeostasis. The surrounding environments around the calcification within plaques also have impacts on plaque homeostasis. The interactive effects of these important factors of calcifications and plaques still await further study.

Targeting mannose receptor expression on macrophages in atherosclerotic plaques of apolipoprotein E-knockout mice using 68Ga-NOTA-anti-MMR nanobody: non-invasive imaging of atherosclerotic plaques

Background

Rupture-prone atherosclerotic plaques are characterized by heavy macrophage infiltration, and the presence of certain macrophage subsets might be a sign for plaque vulnerability. The mannose receptor (MR, CD206) is over-expressed in several types of alternatively activated macrophages. In this study, our objective was to evaluate the feasibility of a Gallium-68 (⁶⁸Ga)-labelled anti-MR nanobody (⁶⁸Ga-anti-MMR Nb) for the visualization of MR-positive (MR⁺) macrophages in atherosclerotic plaques of apolipoprotein E-knockout (ApoE-KO) mice.

Results

NOTA-anti-MMR Nb was labelled with ⁶⁸Ga with radiochemical purity > 95%. In vitro cell-binding studies demonstrated selective and specific binding of the tracer to M2a macrophages. For in vivo atherosclerotic plaque imaging studies, ⁶⁸Ga-NOTA-anti-MMR Nb was injected into ApoE-KO and control mice intravenously (i.v.) and scanned 1 h post-injection for 30 min using a dedicated animal PET/CT. Focal signals could be detected in aortic tissue of ApoE-KO mice, whereas no signal was detected in the aortas of control mice. ⁶⁸Ga-NOTA-anti-MMR Nb uptake was detected in atherosclerotic plaques on autoradiographs and correlated well with Sudan-IV-positive areas. The calculated ratio of plaque-to-normal aortic tissue autoradiographic signal intensity was 7.7 ± 2.6 in aortas excised from ApoE-KO mice. Immunofluorescence analysis of aorta cross-sections confirmed predominant MR expression in macrophages located in the fibrous cap layer and shoulder region of the plaques.

Conclusions

⁶⁸Ga-NOTA-anti-MMR Nb allows non-invasive PET/CT imaging of MR expression in atherosclerotic lesions in a murine model and may represent a promising tool for clinical imaging and evaluation of plaque (in)stability.

The Growing Field of Imaging of Atherosclerosis in Peripheral Arteries

In the past decades, peripheral arteries have represented a model for the comprehension of atherosclerosis as well as for the development of new diagnostic imaging modalities and therapeutic strategies. Peripheral arteries may represent a window to study atherosclerosis. Pathology has prominently contributed to move the clinical and research attention from the arterial lumen stenosis and angiography to morphological and functional imaging techniques. Evidence from large and prospective cohort or randomized controlled studies is still modest. Nevertheless, several emerging imaging investigations represent a potential tool for a comprehensive "in vivo" evaluation of the entire natural history of peripheral atherosclerosis. This constitutes a demanding assignment, as it would be desirable to obtain both single-lesion focused and extensive arterial system views to achieve the most accurate prognostic information. Our narrative review rests upon the fundamental pathological evidence, summarizing the rapidly growing field of imaging of atherosclerosis in peripheral arteries and presenting a selection of both currently available and emerging imaging techniques.

The role of obesity in carotid plaque instability: interaction with age, gender, and cardiovascular risk factors

BACKGROUND

In the last decade, several studies have reported an unexpected and seemingly paradoxical inverse correlation between BMI and incidence of cardiovascular diseases. This so called "obesity paradox effect" has been mainly investigated through imaging methods instead of histologic evaluation, which is still the best method to study the instability of carotid plaque. Therefore, the purpose of our study was to evaluate by histology the role of obesity in destabilization of carotid plaques and the interaction with age, gender and other major cerebrovascular risk factors.

METHODS

A total of 390 carotid plaques from symptomatic and asymptomatic patients submitted to endarterectomy, for whom complete clinical and laboratory assessment of major cardiovascular risk factors was available, were studied by histology. Patients with a BMI ≥ 30.0 kg/m2 were considered as obese. Data were analyzed by multivariate logistic regression and for each variable in the equation the estimated odds ratio (OR) was calculated.

RESULTS

Unstable carotid plaque OR for obese patients with age < 70 years was 5.91 (95% CI 1.17-29.80), thus being the highest OR compared to that of other risk factors. Unstable carotid plaque OR decreased to 4.61 (95% CI 0.54-39.19) in males ≥ 70 years, being only 0.93 (95% CI 0.25-3.52) among women. When obesity featured among metabolic syndrome risk factors, the OR for plaque destabilization was 3.97 (95% CI 1.81-6.22), a significantly higher value compared to OR in non-obese individuals with metabolic syndrome (OR = 1.48; 95% CI 0.86-2.31). Similar results were obtained when assessing the occurrence of acute cerebrovascular symptoms.

CONCLUSIONS

Results from our study appear to do not confirm any paradoxical effect of obesity on the carotid artery district. Conversely, obesity is confirmed to be an independent risk factor for carotid plaque destabilization, particularly in males aged < 70 years, significantly increasing such risk among patients with metabolic syndrome.

Kinin B1 receptor as a novel, prognostic progression biomarker for carotid atherosclerotic plaques

Stroke caused by atherosclerosis remains a leading cause of morbidity and mortality worldwide, associated with carotid plaque rupture and inflammation progression. However, the inflammatory biomarkers which aid in predicting the future course of plaques are less detailed. The present study investigated the association between plaque vulnerable and inflammatory biomarkers using blood and plaque specimens. Carotid plaque specimens were obtained from 80 patients following stroke, 14 patients suffering from transient ischaemic attack and 17 asymptomatic patients that underwent carotid endarterectomy. To assess changes in plaque characteristics at histological levels, plaques were categorized by the time between the latest ischemic stroke and surgical intervention within 30, 30‑90, 90‑180 and over 180 days following stroke. Serum levels of inflammatory biomarkers interleukin (IL)‑6, IL‑10 and kinin B1 receptor (B1R) were measured by ELISA. Histological assessment of plaque was used to evaluate the plaque stability, progression and the inflammatory biomarker levels. Comparisons of histological characteristics demonstrated that plaques revealed an unstable phenotype following stroke within 30, 30‑90 days and then remodeled into more stable plaques following stroke at 90‑180 and over 180 days. By comparing the serum levels of inflammatory biomarkers, it was observed that IL‑6 and B1R levels tended to decline whereas IL‑10 levels increased in stroke patients from <30 days to over 180 days. Immunohistochemical analysis of IL‑6, IL‑10 and B1R demonstrated similar alterations in serum levels. Correlation analyses revealed that only B1R serum level was significantly correlated with histological level in patients with carotid atherosclerosis. The findings revealed that serum B1R levels may provide prognostic information and currently act as potential indicators for progression in atherosclerosis.

Carotid plaque instability is not related to quantity but to elemental composition of calcification

BACKGROUND AND AIMS

Recent studies highlighted the role of calcification processes in the clinical progression of chronic cardiovascular diseases. In this study we investigated the relationship between the chemical composition of calcification and atherosclerotic plaque stability in carotid arteries.

METHODS AND RESULTS

To this end, we characterized the calcification on 229 carotid plaques, by morphology, immunohistochemistry, transmission electron microscopy and energy dispersive X-ray microanalysis. Plaques were classified into two categories: unstable and stable. No significant differences were found in the incidence of the various risk factors between patients with and without carotid calcification, with the exception of diabetes. The energy dispersive X-ray microanalysis allowed us to identify two types of calcium salts in the atheromatous plaques, hydroxyapatite (HA) and calcium oxalate (CO). Our results showed that calcification is a common finding in carotid plaques, being present in 77.3% of cases, and the amount of calcium is not a factor of vulnerability. Noteworthy, we observed an association between HA calcification and unstable plaques. On the contrary, CO calcifications were mainly detected in stable plaques.

CONCLUSIONS

The presence of different types of calcification in atheromatous plaques may open new perspectives in understanding the molecular mechanisms of atheroma formation and plaque instability.

Targeting mannose receptor expression on macrophages in atherosclerotic plaques of apolipoprotein E-knockout mice using 111In-tilmanocept

Background

Atherosclerotic plaque phenotypes are classified based on the extent of macrophage infiltration into the lesions, and the presence of certain macrophage subsets might be a sign for plaque vulnerability. The mannose receptor (MR) is over-expressed in activated macrophages. Tilmanocept is a tracer that targets MR and is approved in Europe and the USA for the detection of sentinel lymph nodes. In this study, our aim was to evaluate the potential of ¹¹¹In-labelled tilmanocept for the detection of MR-positive macrophages in atherosclerotic plaques of apolipoprotein E-knockout (ApoE-KO) mouse model.

Methods

Tilmanocept was labelled with ¹¹¹In. The labelling stability and biodistribution of the tracer was first evaluated in control mice (n = 10) 1 h post injection (p.i.). For in vivo imaging studies, ¹¹¹In-tilmanocept was injected into ApoE-KO (n = 8) and control (n = 8) mice intravenously (i.v.). The mice were scanned 90 min p.i. using a dedicated animal SPECT/CT. For testing the specificity of ¹¹¹In-tilmanocept uptake in plaques, a group of ApoE-KO mice was co-injected with excess amount of non-labelled tilmanocept. For ex vivo imaging studies, the whole aortas (n = 9 from ApoE-KO and n = 4 from control mice) were harvested free from adventitial tissue for Sudan IV staining and autoradiography. Cryosections were prepared for immunohistochemistry (IHC).

Results

¹¹¹In radiolabelling of tilmanocept provided a yield of greater than 99%. After i.v. injection, ¹¹¹In-tilmanocept accumulated in vivo in MR-expressing organs (i.e. liver and spleen) and showed only low residual blood signal 1 h p.i. MR-binding specificity in receptor-positive organs was demonstrated by a 1.5- to 3-fold reduced uptake of ¹¹¹In-tilmanocept after co-injection of a blocking dose of non-labelled tilmanocept. Focal signal was detected in atherosclerotic plaques of ApoE-KO mice, whereas no signal was detected in the aortas of control mice. ¹¹¹In-tilmanocept uptake was detected in atherosclerotic plaques on autoradiography correlating well with Sudan IV-positive areas and associating with subendothelial accumulations of MR-positive macrophages as demonstrated by IHC.

Conclusions

After i.v. injection, ¹¹¹In-tilmanocept accumulated in MR-expressing organs and was associated with only low residual blood signal. In addition, ¹¹¹In-tilmanocept uptake was detected in atherosclerotic plaques of mice containing MR-expressing macrophages suggesting that tilmanocept represents a promising tracer for the non-invasive detection of macrophages in atherosclerotic plaques.

Morphometric analysis of calcification and fibrous layer thickness in carotid endarterectomy tissues

BACKGROUND

Advanced atherosclerotic lesions are commonly characterized by the presence of calcification. Several studies indicate that extensive calcification is associated with plaque stability, yet recent studies suggest that calcification morphology and location may adversely affect the mechanical stability of atherosclerotic plaques. The underlying cause of atherosclerotic calcification and the importance of intra-plaque calcium distribution remains poorly understood.

METHOD

The goal of this study was the characterization of calcification morphology based on histological features in 20 human carotid endarterectomy (CEA) specimens. Representative frozen sections (10μm thick) were cut from the common, bulb, internal and external segments of CEA tissues and stained with von Kossa׳s reagent for calcium phosphate. The morphology of calcification (calcified patches) and fibrous layer thickness were quantified in 135 histological sections.

RESULTS

Intra-plaque calcification was distributed heterogeneously (calcification %-area: bulb segment: 14.2±2.1%; internal segment: 12.9±2.8%; common segment: 4.6±1.1%; p=0.001). Calcified patches were found in 20 CEAs (patch size: <0.1mm(2) to >1.0mm(2)). Calcified patches were most abundant in the bulb and least in the common segment (bulb n=7.30±1.08; internal n=4.81±1.17; common n=2.56±0.56; p=0.0007). Calcified patch circularity decreased with increasing size (<0.1mm(2): 0.77±0.01, 0.1-1mm(2): 0.62±0.01, >1.0mm(2): 0.51±0.02; p=0.0001). A reduced fibrous layer thickness was associated with increased calcium patch size (p<0.0001).

CONCLUSIONS

In advanced carotid atherosclerosis, calcification appears to be a heterogeneous and dynamic atherosclerotic plaque component, as indicated by the simultaneous presence of few large stabilizing calcified patches and numerous small calcific patches. Future studies are needed to elucidate the associations of intra-plaque calcification size and distribution with atherothrombotic events.

Distribution of calcification in carotid endarterectomy tissues: Comparison of micro-computed tomography imaging with histology

Background:

Calcification in atherosclerotic plaques has been viewed as a marker of plaque stability, but whether calcification accumulates in specific anatomic sites in the carotid artery is unknown. We determined the burden and distribution of calcified plaque in carotid endarterectomy (CEA) tissues.

Methods:

A total of 22 CEA tissues were imaged with high-resolution micro-computed tomography (micro-CT). Total plaque burden and total calcium score using the Agatston method were quantified. The Agatston score (AS) was also normalized for tissue size. Plaque and calcium distribution were analyzed separately for three CEA regions: common segment (CS), bulb segment (BS), and internal/external segments (IES).

Results:

The average CEA tissue length was 40.83 (interquartile range [IQR] 33.31–42.41) mm with total plaque burden of 103.45 (IQR: 78.84–156.81) mm3 and total AS of 38.58 (IQR 11.59–89.97). Total plaque volume was 21.02 (IQR: 14.47–25.42) mm3 in the CS, 37.89 (22.59–48.32) mm3 in the BS, and 54.05 (36.87–74.52) mm3 in the IES. Of the 22 tissues, 15 had no calcium in the CS compared with three in the bulb and two in the IES. Normalized calcified plaque was most prevalent in the BS, the IES and was least prevalent in the CS. The overall correlation of calcification between histology sections and matched micro-CT images was 0.86 ( p<0.001).

Conclusions:

Calcified plaque is heterogeneously distributed in CEA tissues with most in the bulb and IES regions. The amount of calcification in micro-CT slices shows a high correlation with matched histology sections.

Imaging of the carotid artery vulnerable plaque

Atherosclerosis involving the carotid arteries has a high prevalence in the population worldwide. This condition is significant because accidents of the carotid artery plaque are associated with the development of cerebrovascular events. For this reason, carotid atherosclerotic disease needs to be diagnosed and those determinants that are associated to an increased risk of stroke need to be identified. The degree of stenosis typically has been considered the parameter of choice to determine the therapeutical approach, but several recently published investigations have demonstrated that the degree of luminal stenosis is only an indirect indicator of the atherosclerotic process and that direct assessment of the plaque structure and composition may be key to predict the development of future cerebrovascular ischemic events. The concept of "vulnerable plaque" was born, referring to those plaque's parameters that concur to the instability of the plaque making it more prone to the rupture and distal embolization. The purpose of this review is to describe the imaging characteristics of "vulnerable carotid plaques."

Comparison of contrast agents for atherosclerosis imaging using cultured macrophages: FDG versus ultrasmall superparamagnetic iron oxide

Various noninvasive imaging methods have been developed to evaluate atherosclerotic plaques. Among them, (18)F-FDG PET and MR imaging with ultrasmall superparamagnetic iron oxide particles (USPIO) have been used to quantify plaque inflammation. Both methods are based on the efficient uptake of FDG and USPIO by macrophages in atherosclerotic lesions. Differently polarized macrophages have been reported to have different characteristics that are involved in the pathologic development of atherosclerosis. M1 polarized macrophages are considered the more proatherogenic phenotype than M2 polarized macrophages. However, little is known regarding the association between macrophage polarization and FDG or USPIO accumulation. In this study, we investigated intracellular FDG and USPIO accumulation in M1 and M2 polarized macrophages.

METHODS

THP-1 macrophages were differentiated into M1 and M2 polarized macrophages. Under optimal glucose conditions, we investigated the (3)H-labeled FDG uptake in M1 and M2 polarized macrophages. We then investigated intracellular USPIO uptake by M1 and M2 macrophages.

RESULTS

We found that M1 polarization, compared with M2 polarization, results in increased intracellular accumulation of FDG. To elucidate the mechanism by which FDG was preferentially accumulated in M1 macrophages, we examined messenger RNA expressions of glucose transporters (GLUTs) and hexokinases, which have pivotal roles in glucose uptake, and glucose-6-phosphatase (G6Pase), which catalyzes the reverse reaction of hexokinase. In M1 macrophages, GLUT-1, GLUT-3, hexokinase 1, and hexokinase 2 were upregulated and G6Pase was downregulated. In contrast to FDG, M1 polarization resulted in decreased intracellular accumulation of USPIO. We found that scavenger receptor A and CD11b, which are involved in USPIO binding and uptake, were significantly downregulated by M1 polarization.

CONCLUSION

Compared with M2, proatherogenic M1 macrophages preferentially accumulated FDG but not USPIO, suggesting that FDG PET is a useful method for the detection of proinflammatory M1 macrophages.

Sex-related differences in carotid plaque features and inflammation

OBJECTIVE

Severe carotid stenosis is a frequent cause of stroke in both men and women. Whereas several sex-related comparisons are available on coronary atherosclerosis, there are few data appraising gender-specific features of carotid plaques. We aimed to systematically compare the pathology and inflammatory features of carotid plaques in men vs women.

METHODS

Carotid plaque specimens were collected from patients undergoing surgical endarterectomy for asymptomatic or symptomatic carotid stenosis. Histologic analysis was performed, as well as measurements of plaque composition and inflammation.

RESULTS

A total of 457 patients were included (132 women, 325 men). Baseline analyses showed a greater prevalence of hypercholesterolemia, hypertension, and former smoking status in women, despite a higher Framingham Heart Score in men (all P < .05). Women had a lower prevalence of thrombotic plaques, smaller percentage area of necrotic core, and hemorrhage extension (all P < .05). Plaque inflammation analysis showed a lower concentration of inflammatory and, in particular, of macrophage foam cells in the plaque cap of women (both P < .05). These differences were, however, no longer significant at multivariable analysis, including several baseline features, such as symptom status and stenosis severity.

CONCLUSIONS

Carotid plaques seem significantly different in women and men, but the main drivers of such pathologic differences are baseline features, including stenosis severity and symptom status.