Circulating CD14+ and CD14highCD16- classical monocytes are reduced in patients with signs of plaque neovascularization in the carotid artery

Harnessing the potential of monocytes/macrophages to regenerate tissue-engineered vascular grafts

Cell-free tissue-engineered vascular grafts provide a promising alternative to treat cardiovascular disease, but timely endothelialization is essential for ensuring patency and proper functioning post-implantation. Recent studies from our lab showed that blood cells like monocytes (MCs) and macrophages (Mϕ) may contribute directly to cellularization and regeneration of bioengineered arteries in small and large animal models. While MCs and Mϕ are leucocytes that are part of the innate immune response, they share common developmental origins with endothelial cells (ECs) and are known to play crucial roles during vessel formation (angiogenesis) and vessel repair after inflammation/injury. They are highly plastic cells that polarize into pro-inflammatory and anti-inflammatory phenotypes upon exposure to cytokines and differentiate into other cell types, including EC-like cells, in the presence of appropriate chemical and mechanical stimuli. This review focuses on the developmental origins of MCs and ECs; the role of MCs and Mϕ in vessel repair/regeneration during inflammation/injury; and the role of chemical signalling and mechanical forces in Mϕ inflammation that mediates vascular graft regeneration. We postulate that comprehensive understanding of these mechanisms will better inform the development of strategies to coax MCs/Mϕ into endothelializing the lumen and regenerate the smooth muscle layers of cell-free bioengineered arteries and veins that are designed to treat cardiovascular diseases and perhaps the native vasculature as well.

The discovery of GGT1 as a novel gene for ischemic stroke conferring protection against disease risk in non-smokers and non-abusers of alcohol

OBJECTIVES

Increased plasma gamma-glutamyl transferase (GGT1) has been identified as a robust and independent risk factor for ischemic stroke (IS), but the molecular mechanisms of the enzyme-disease association are unclear. The present study investigated whether polymorphisms in the GGT1 gene contribute to IS susceptibility.

MATERIALS AND METHODS

DNA samples obtained from 1288 unrelated individuals (600 IS patients and 688 controls) were genotyped for common single nucleotide polymorphisms of GGT1 using the MassArray-4 platform.

RESULTS

The rs5751909 polymorphism was significantly associated with decreased risk of ischemic stroke regardless sex and age (Pperm ≤ 0.01, dominant genetic model). The haplotype rs4820599A-rs5760489A-rs5751909A showed strong protection against ischemic stroke (OR 0.53, 95 %CI 0.36 - 0.77, Pperm ≤ 0.0001). The protective effect of SNP rs5751909 in the stroke phenotype was successfully replicated in the UK Biobank, SiGN, and ISGC cohorts (P ≤ 0.01). GGT1 polymorphisms showed joint (epistatic) effects on the risk of ischemic stroke, with some known IS-associated GWAS loci (e.g., rs4322086 and rs12646447) investigated in our population. In addition, SNP rs5751909 was found to be strongly associated with a decreased risk of ischemic stroke in non-smokers (OR 0.54 95 %CI 0.39-0.75, Pperm = 0.0002) and non-alcohol abusers (OR 0.43 95 %CI 0.30-0.61, Pperm = 2.0 × 10-6), whereas no protective effects of this SNP against disease risk were observed in smokers and alcohol abusers (Pperm < 0.05).

CONCLUSIONS

We propose mechanisms underlying the observed associations between GGT1 polymorphisms and ischemic stroke risk. This pilot study is the first to demonstrate that GGT1 is a novel susceptibility gene for ischemic stroke and provides additional evidence of the genetic contribution to impaired redox homeostasis underlying disease pathogenesis.

Radiomics in Carotid Plaque: A Systematic Review and Radiomics Quality Score Assessment

Imaging modalities provide information on plaque morphology and vulnerability; however, they are operator dependent and miss a great deal of microscopic information. Recently, many radiomics models for carotid plaque that identify unstable plaques and predict cardiovascular outcomes have been proposed. This systematic review was aimed at assessing whether radiomics is a reliable and reproducible method for the clinical prediction of carotid plaque. A systematic search was conducted to identify studies published in PubMed and Cochrane library from January 1, 2001, to September 30, 2022. Both retrospective and prospective studies that developed and/or validated machine learning models based on radiomics data to classify or predict carotid plaques were included. The general characteristics of each included study were selected, and the methodological quality of radiomics reports and risk of bias were evaluated using the radiomics quality score (RQS) tool and Quality Assessment of Diagnostic Accuracy Studies-2, respectively. Two investigators independently reviewed each study, and the consensus data were used for analysis. A total of 2429 patients from 16 studies were included. The mean area under the curve of radiomics models for diagnostic or predictive performance of the included studies was 0.88 ± 0.02, with a range of 0.741-0.989. The mean RQS was 9.25 (standard deviation: 6.04), representing 25.7% of the possible maximum value of 36, whereas the lowest point was -2, and the highest score was 22. Radiomics models have revealed additional information on patients with carotid plaque, but with respect to methodological quality, radiomics reports are still in their infancy, and many hurdles need to be overcome.

Effect of pharmacologic anti-atherosclerotic therapy on carotid intraplaque neovascularization: A systematic review

Intraplaque neovascularization (IPN), a key feature of vulnerable carotid plaque, is associated with adverse cardiovascular (CV) events. Statin therapy has been shown to diminish and stabilize atherosclerotic plaque, but its effect on IPN is uncertain. This review investigated the effects of common pharmacologic anti-atherosclerotic therapies on carotid IPN. Electronic databases (MEDLINE, EMBASE and Cochrane Library) were searched from inception until July 13, 2022. Studies evaluating the effect of anti-atherosclerotic therapy on carotid IPN among adults with carotid atherosclerosis were included. Sixteen studies were eligible for inclusion. Contrast-enhanced ultrasound (CEUS) was the most common IPN assessment modality (n=8), followed by dynamic contrast-enhanced MRI (DCE-MRI) (n=4), excised plaque histology (n=3) and superb microvascular imaging (n=2). In fifteen studies, statins were the therapy of interest and one study assessed PCSK9 inhibitors. Among CEUS studies, baseline statin use was associated with a lower frequency of carotid IPN (median OR = 0.45). Prospective studies showed regression of IPN after 6-12 months of lipid-lowering therapy, with more regression observed in treated participants compared to untreated controls. Our findings suggest that lipid-lowering therapy with statins or PCSK9 inhibitors is associated with IPN regression. However, there was no correlation between change in IPN parameters and change in serum lipids and inflammatory markers in statin-treated participants, so it is unclear whether these factors are mediators in the observed IPN changes. Lastly, this review was limited by study heterogeneity and small sample sizes, so larger trials are needed to validate findings.

An Unbiased Flow Cytometry-Based Approach to Assess Subset-Specific Circulating Monocyte Activation and Cytokine Profile in Whole Blood

Monocytes are the third most frequent type of leukocytes in humans, linking innate and adaptive immunity and are critical drivers in many inflammatory diseases. Based on the differential expression of surface antigens, three monocytic subpopulations have been suggested in humans and two in rats with varying inflammatory and phenotype characteristics. Potential intervention strategies that aim to manipulate these cells require an in-depth understanding of monocyte behavior under different conditions. However, monocytes are highly sensitive to their specific activation state and expression of surface markers, which can change during cell isolation and purification. Thus, there is an urgent need for an unbiased functional analysis of activation in monocyte subtypes, which is not affected by the isolation procedure. Here, we present a flow cytometry-based protocol for evaluating subset-specific activation and cytokine expression of circulating blood monocytes both in humans and rats using small whole blood samples (50 - 100 μL). In contrast to previously described monocyte isolation and flow cytometry visualization methods, the presented approach virtually leaves monocyte subsets in a resting state or fixes them in their current state and allows for an unbiased functional endpoint analysis without prior cell isolation. This protocol is a comprehensive tool for studying differential monocyte regulation in the inflammatory and allogeneic immune response in vitro and vivo.

Long non-coding RNA GAS5 knockdown facilitates proliferation and impedes apoptosis by regulating miR-128-3p/FBLN2 axis in ox-LDL-induced THP-1 cells

BACKGROUND

Long non-coding RNAs (lncRNAs) are found to involve in modulating the development of atherosclerosis (AS). But the molecular mechanism of lncRNA growth-arrest specific transcript 5 (GAS5) in AS is not fully understood.

METHODS

QRT-PCR was performed to measure the abundances of GAS5, miR-128-3p and fibulin 2 (FBLN2). Oxidized low-density lipoprotein (ox-LDL)-treated THP-1 cells were employed as cell models of AS. The cell proliferation and apoptosis were analyzed using CCK-8 and Flow cytometry assays, respectively. Levels of all protein were examined by western blot. The interaction among GAS5, miR-128-3p and FBLN2 was confirmed via dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.

RESULTS

GAS5 was elevated and miR-128-3p was decreased in the serum of patients with AS and ox-LDL-stimulated THP-1 cells. Ox-LDL stimulation inhibited proliferation and induced apoptosis of THP-1 cells. Meanwhile, GAS5 directly targeted miR-128-3p and inversely modulated its expression. Importantly, GAS5 depletion facilitated cell proliferation and impaired apoptosis in ox-LDL-induced THP-1 cells. Additionally, GAS5 augmented FBLN2 expression through sponging miR-128-3p, and miR-128-3p facilitated proliferation and retarded apoptosis of ox-LDL-induced THP-1 cells by targeting FBLN2.

CONCLUSION

GAS5 knockdown promoted the growth of ox-LDL-induced THP-1 cells through down-modulating FBLN2 and increasing miR-128-3p, suggesting the potential value of GAS5 for treatment of AS.

In vitro Phenotype Induction of Circulating Monocytes: CD16 and CD163 Analysis

Introduction

CD14 (monocyte differentiation antigen, LPS binding protein – endotoxin receptor) and CD16 (FcγRIII, Low-affinity receptor for IgG) define three subpopulations of circulating monocytes with different inflammatory and phagocytic capabilities. Contradictory reports exist regarding both in vivo monocyte phenotype-disease association and response of these circulating monocytes to in vitro stimulation. We analyzed phenotypic changes in circulating monocytes when stimulated with LPS (pro-inflammatory stimulus) and IL-4 (alternative inflammatory stimulus).

Methods

Mononuclear cells from nine healthy donors were extracted and studied for surface and intracellular markers using flow cytometry. PBMC were extracted using Ficoll technic and immediately analyzed using flow cytometry. Pro-inflammatory interleukin IL-1β and IL-6 were measured by intracellular cytometry. Mononuclear cells were stimulated using LPS and IL-4 as previously described. Changes against non-stimulated populations were statistically analyzed.

Results

Compared to non-stimulated and IL-4 stimulated monocytes, LPS-stimulated cells display a singular pattern of markers, with higher levels of intracellular IL-1β and IL-6 directly correlating with CD14+CD163- cell frequency and diminishing membrane CD163 fluorescence. CD14+CD16- classical monocytes show greater percentage of CD163- cells upon LPS stimulation. CD86 levels on monocytes’ surface did not change with LPS or IL-4 stimulation.

Conclusions and Discussion

We showed that CD14+CD16- classical monocytes display higher sensitivity to LPS stimulation, with more IL-1β and IL-6 levels than intermediate and non-classical monocytes. This subset also diminishes its CD163 levels on the membrane after LPS stimulation with a contemporary raise in CD163- cells, suggesting that classical monocytes preferentially acquire CD163- defined M1 characteristics upon in vitro LPS stimulation. Intermediate and non-classical monocytes respond with lower levels of interleukins and display surface proteins in an M2-type profile (CD163+).

The new prognostic factor for pulmonary embolism: The ratio of monocyte count to HDL cholesterol

PURPOSE

Aim of this study is to investigate effectiveness of the monocyte to HDL cholesterol ratio in patients diagnosed with pulmonary embolism for predicting intra-hospital mortality.

METHOD

A total of 269 patients diagnosed with pulmonary embolism in the emergency clinic were included in the study. Study was conducted retrospectively. Pulmonary Embolism Severity Index (PESI), Monocyte count and high density lipoprotein cholesterol (HDL) values were determined. MHR values of the patients were calculated. SPSS 26 package program was used to investigate the effectiveness of MHR in predicting mortality.

FINDINGS

Mean age of the patients was 64.51 ± 12.4 years. PESI, Number of monocytes and MHR were significantly higher in the group with mortality than the group without mortality (p < .05). HDL values were significantly lower (p < .05) in mortality group. Sensitivity of MHR 19 cut off value was 89.3%, and its specificity was 82.0%.

CONCLUSION

Use of predictors for mortality estimation in patients diagnosed with acute pulmonary embolism is important for faster administration of treatment modalities. We think MHR values can be used as a strong predictor according to the hemogram parameters and biochemical results.

Extent and characteristics of carotid plaques and brain parenchymal loss in asymptomatic patients with no indication for revascularization

BACKGROUND AND AIMS

Extent of subclinical atherosclerosis has been associated with brain parenchymal loss in community-dwelling aged subjects. Identification of patient-related and plaque-related markers could identify subjects at higher risk of brain atrophy, independent of cerebrovascular accidents. Aim of the study was to investigate the relation between extent and characteristics of carotid plaques and brain atrophy in asymptomatic patients with no indication for revascularization.

METHODS AND RESULTS

Sixty-four patients (aged 69 ± 8 years, 45% females) with carotid stenosis <70% based on Doppler flow velocity were enrolled in the study. Potential causes of cerebral damage other than atherosclerosis, including history of atrial fibrillation, heart failure, previous cardiac or neurosurgery and neurological disorders were excluded. All subjects underwent carotid computed tomography angiography, contrast enhanced ultrasound for assessment of plaque neovascularization and brain magnetic resonance imaging for measuring brain volumes. On multivariate regression analysis, age and fibrocalcific plaques were independently associated with lower total brain volumes (β = -3.13 and β = -30.7, both p < 0.05). Fibrocalcific plaques were also independently associated with lower gray matter (GM) volumes (β = -28.6, p = 0.003). On the other hand, age and extent of carotid atherosclerosis were independent predictors of lower white matter (WM) volumes.

CONCLUSIONS

WM and GM have different susceptibility to processes involved in parenchymal loss. Contrary to common belief, our results show that presence of fibrocalcific plaques is associated with brain atrophy.

Contrast imaging ultrasound for the detection and characterization of carotid vulnerable plaque

Not only the degree of luminal narrowing but also the plaque morphology and composition play an important role in risk stratification of carotid atherosclerotic lesions. During the last few years, carotid contrast-enhanced ultrasound (CEUS) has emerged as a valuable imaging tool to assess such vulnerable carotid plaques. This review article discussed the use of CEUS for the detection of carotid plaque irregularities and ulcerations as well as the quantification of intraplaque neovascularization and its correlation with histology and inflammatory biomarkers. Apart from evaluating for markers of vulnerable carotid plaques, CEUS enhancement is directly associated with past cerebrovascular events. More importantly, preliminary evidence has shown that CEUS could be used to predict future cerebrovascular and cardiovascular events. Despite the progress in CEUS imaging for carotid atherosclerotic disease, past studies still suffer from the retrospective nature, small sample size, and a lack of matched, well controlled prospective studies. In the future, large multi-center prospective studies addressing the relationship between CEUS findings and patient clinical outcomes in carotid atherosclerotic disease are warranted.

Perivascular Fat Density and Contrast Plaque Enhancement: Does a Correlation Exist?

BACKGROUND AND PURPOSE

Inflammatory changes in the fat tissue surrounding the coronary arteries have been associated with coronary artery disease and high-risk vulnerable plaques. Our aim was to investigate possible correlations between the presence and degree of perivascular fat density and a marker of vulnerable carotid plaque, namely contrast plaque enhancement on CTA.

MATERIALS AND METHODS

One-hundred patients (76 men, 24 women; mean age, 69 years) who underwent CT angiography for investigation of carotid artery stenosis were retrospectively analyzed. Contrast plaque enhancement and perivascular fat density were measured in 100 carotid arteries, and values were stratified according to symptomatic (ipsilateral-to-cerebrovascular symptoms)/asymptomatic status (carotid artery with the most severe degree of stenosis). Correlation coefficients (Pearson ρ product moment) were calculated between the contrast plaque enhancement and perivascular fat density. The differences among the correlation ρ values were calculated using the Fisher r-to-z transformation. Mann-Whitney analysis was also calculated to test differences between the groups.

RESULTS

There was a statistically significant positive correlation between contrast plaque enhancement and perivascular fat density (ρ value = 0.6582, P value = .001). The correlation was stronger for symptomatic rather than asymptomatic patients (ρ value = 0.7052, P value = .001 versus ρ value = 0.4092, P value = .001).

CONCLUSIONS

There was a positive association between perivascular fat density and contrast plaque enhancement on CTA. This correlation was stronger for symptomatic rather than asymptomatic patients. Our results suggest that perivascular fat density could be used as an indirect marker of plaque instability.

Impact of monocyte to high-density lipoprotein ratio on prevalent hyperuricemia: findings from a rural Chinese population

BACKGROUND

Monocyte to high-density lipoprotein cholesterol ratio (MHR) is a novel inflammatory marker that has been used to predict various inflammation-related diseases. This study aims to explore the association between MHR and prevalent hyperuricemia in a rural Chinese population.

METHODS

8163 eligible participants (mean age: 54.13 years, males: 45.71%) from northeast China were enrolled in this cross-sectional study between 2012 to 2013. MHR was determined as blood monocyte count ratio to high-density lipoprotein cholesterol concentration.

RESULTS

The prevalence of hyperuricemia was 12.86%. After adjusting for potential confounding factors, per SD increase of MHR caused a 25.2% additional risk for hyperuricemia, and the top quartile of MHR had an 82.9% increased risk for hyperuricemia compared with the bottom quartile. Additionally, smooth curve fitting and subgroup analyses showed a linear and robust association between MHR and prevalent hyperuricemia respectively. Finally, after introducing MHR into the established model of risk factors, the AUC displayed a significant improvement (0.718 vs 0.724, p = 0.008). Furthermore, Category-free net reclassification improvement (0.160, 95% CI: 0.096-0.224, P < 0.001) and integrated discrimination improvement (0.003, 95% CI: 0.002-0.005, P < 0.001) also demonstrated significant improvements.

CONCLUSIONS

The present study suggests that MHR was positively and independently correlated with prevalent hyperuricemia among rural Chinese adults. Our results also implicate an important value for MHR in optimizing the risk stratification of hyperuricemia.

Contrast-Enhanced Ultrasound to Assess Carotid Intraplaque Neovascularization

Contrast-enhanced ultrasound (CEUS) is increasingly being used to identify patients with carotid plaques that are vulnerable to rupture, so-called vulnerable atherosclerotic plaques, by assessment of intraplaque neovascularization. A complete overview of the strengths and limitations of carotid CEUS is currently not available. The aim of this systematic review was to provide a complete overview of existing publications on the role of CEUS in assessment of carotid intraplaque neovascularization. The systematic review of the literature yielded 52 studies including a total of 4660 patients (mean age: 66 y, 71% male) who underwent CEUS for the assessment of intraplaque neovascularization. The majority of the patients (76%) were asymptomatic and had no history of transient ischemic attack (TIA) or stroke. The assessment of intraplaque neovascularization was mostly performed using a visual scoring system; several studies used time-intensity curves or dedicated quantification software to optimize analysis. In 17 studies CEUS was performed in patients before carotid surgery (endarterectomy), allowing a comparison of pre-operative CEUS findings with histologic analysis of the tissue sample that is removed from the carotid artery. In a total of 576 patients, the CEUS findings were compared with histopathological analysis of the plaque after surgery. In 16 of the 17 studies, contrast enhancement was found to correlate with the presence and degree of intraplaque neovascularization on histology. Plaques with a larger amount of contrast enhancement had significantly increased density of microvessels in the corresponding region on histology. In conclusion, CEUS is a readily available imaging modality for the assessment of patients with carotid atherosclerosis, providing information on atherosclerotic plaques, such as ulceration and intraplaque neovascularization, which may be clinically relevant. The ultimate clinical goal is the early identification of carotid atherosclerosis to start early preventive therapy and prevent clinical complications such as TIA and stroke.

Abnormal Distribution and Function of Circulating Monocytes and Enhanced Bacterial Translocation in Major Depressive Disorder

Introduction: Major depressive disorder (MDD) patients experience a systemic inflammatory stage. Monocytes play an important role in innate inflammatory responses and may be modulated by bacterial translocation. Our aim was to investigate the subset distribution and function of circulating monocytes, levels of proinflammatory cytokines, gut barrier damage, and bacterial translocation in MDD patients. Methods: Twenty-two MDD patients without concomitant diseases and 14 sex- and age-matched healthy controls were studied. The levels of circulating CD14++CD16- (classical), CD14++CD16++ (intermediate) and CD14-CD16++ (nonclassical) monocytes and the intracytoplasmic tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-10 expression in the presence or absence of lipopolysaccharide (LPS) stimulation were analyzed by polychromatic flow cytometry. The serum TNF-α, IL-1β, IL-6, and IL-10 levels were measured by Luminex. LPS-binding protein (LBP), intestinal fatty acid-binding protein (I-FABP), and zonulin were measured by enzyme-linked immunosorbent assay (ELISA). Results: MDD patients had a significant increase in the frequency of intermediate monocytes and a significant decrease in the frequency of classical monocytes compared to those in the healthy controls. MDD patients had a significantly increased percentage of classical monocytes that expressed IL-1β, intermediate monocytes that expressed IL-1β and IL6 and nonclassical monocytes that expressed IL-1β, and decreased levels of nonclassical monocytes that expressed IL6 compared to those in the healthy controls. MDD patients had significantly increased levels of circulating TNF-α, IL-1β, LBP, and I-FABP compared to those in the healthy controls. MDD patients with high LBP levels had a significant reduction in the number of circulating monocytes compared to that in the normal-LBP MDD patients, which can be mainly ascribed to a decrease in the number of intermediate and nonclassical monocytes. Conclusions: We have demonstrated that compared to the healthy controls, MDD patients show a marked alteration in circulating monocytes, with an expansion of the intermediate subset with increased frequency of IL-1β and IL-6 producing cells. These patients also exhibited a systemic proinflammatory state, which was characterized by the enhanced serum TNF-α and IL-1β levels compared to those in the healthy controls. Furthermore, MDD patients showed increased LBP and I-FABP levels compared to those in healthy controls, indicating increased bacterial translocation and gut barrier damage.

Human Monocyte Subsets and Phenotypes in Major Chronic Inflammatory Diseases

Human monocytes are divided in three major populations; classical (CD14⁺CD16⁻), non-classical (CD14^dimCD16⁺), and intermediate (CD14⁺CD16⁺). Each of these subsets is distinguished from each other by the expression of distinct surface markers and by their functions in homeostasis and disease. In this review, we discuss the most up-to-date phenotypic classification of human monocytes that has been greatly aided by the application of novel single-cell transcriptomic and mass cytometry technologies. Furthermore, we shed light on the role of these plastic immune cells in already recognized and emerging human chronic diseases, such as obesity, atherosclerosis, chronic obstructive pulmonary disease, lung fibrosis, lung cancer, and Alzheimer's disease. Our aim is to provide an insight into the contribution of human monocytes to the progression of these diseases and highlight their candidacy as potential therapeutic cell targets.

The Role of Monocytes and Macrophages in Human Atherosclerosis, Plaque Neoangiogenesis, and Atherothrombosis

Atherosclerosis is one of the leading causes of death and disability worldwide. It is a complex disease characterized by lipid accumulation within the arterial wall, inflammation, local neoangiogenesis, and apoptosis. Innate immune effectors, in particular monocytes and macrophages, play a pivotal role in atherosclerosis initiation and progression. Although most of available evidence on the role of monocytes and macrophages in atherosclerosis is derived from animal studies, a growing body of evidence elucidating the role of these mononuclear cell subtypes in human atherosclerosis is currently accumulating. A novel pathogenic role of monocytes and macrophages in terms of atherosclerosis initiation and progression, in particular concerning the role of these cell subsets in neovascularization, has been discovered. The aim of the present article is to review currently available evidence on the role of monocytes and macrophages in human atherosclerosis and in relation to plaque characteristics, such as plaque neoangiogenesis, and patients' prognosis and their potential role as biomarkers.

Circulating CD14+CD16- classical monocytes do not associate with a vulnerable plaque phenotype, and do not predict secondary events in severe atherosclerotic patients

AIMS

Mouse studies have established distinct monocyte subtypes that participate in the process of atherosclerotic lesion formation. The pro-inflammatory Ly6C^high monocyte subtype actively contributes to murine plaque progression and destabilization. Also in humans, different peripheral monocyte subtypes have been identified, of which the CD14⁺CD16^- classical monocyte is suggested to display similar pro-atherosclerotic properties as the murine Ly6C^high subtype. We aimed to investigate if circulating CD14⁺CD16^- classical monocytes associate with characteristics of a vulnerable carotid atherosclerotic plaque and if they associate with the risk of secondary adverse manifestations of atherosclerotic disease.

METHODS AND RESULTS

We enrolled 175 carotid endarterectomy patients of the Athero-Express biobank in our study. Just prior to surgical procedure, blood was collected and peripheral blood mononuclear cells were isolated. Characterization of monocyte subsets was performed by flow cytometry. Plaque characteristics were semi-quantitatively scored for the presence of fat, collagen, intraplaque hemorrhage and calcification. Vessel density, smooth muscle cells and macrophages were assessed quantitatively on a continuous scale. All features of a vulnerable plaque phenotype, including low amounts of collagen and smooth muscle cells, and increased fat content, vessel density, intraplaque hemorrhage and plaque macrophages were not significantly associated with differential levels of peripheral classical CD14⁺CD16^- monocytes or other monocyte subsets. Using Cox regression models to evaluate the prognostic value of circulating monocyte subtypes, we found that total counts of peripheral monocytes, as well as CD14⁺CD16^- classical and other monocyte subtypes were not associated with the risk of secondary cardiovascular events during 3 years follow-up.

CONCLUSION

Circulating classical CD14⁺CD16^- monocytes do not associate with specific vulnerable plaque characteristics. In addition, they do not predict secondary adverse manifestations. This suggests that in patients with established carotid artery disease, the circulating monocytes do not reflect plaque characteristics and have no value in identifying patients at risk for future cardiovascular events.

Carotid artery plaque uptake of 11C-PK11195 inversely correlates with circulating monocytes and classical CD14++CD16- monocytes expressing HLA-DR

Background

We explored the relation between blood concentrations of monocyte/lymphocyte subsets and carotid artery plaque macrophage content, measured by positron emission tomography (PET) with ¹¹C-PK11195.

Methods and results

In 9 patients with carotid plaques we performed ¹¹C-PK11195-PET/computed tomography angiography imaging and measurement of absolute concentrations and frequencies of circulating monocytes and T-cell subsets. Plaque standardized uptake value (SUV) for ¹¹C-PK11195 was negatively correlated with concentrations of total monocytes (r = -0.58, p = 0.05) and CD14⁺⁺CD16^-HLA-DR⁺ classical subset (r = -0.82, p = 0.005). These correlations hold true also in relation to plaque target to background ratio. No correlation was observed between plaque SUV and CD3⁺T lymphocytes, CD4⁺T lymphocytes nor with activated CD3⁺CD4⁺T cells expressing HLA-DR.

Conclusions

We first demonstrated a reduction in the absolute concentration of monocytes and particularly in classical monocytes expressing HLA-DR in the presence of an increased uptake of ¹¹C-PK11195 in carotid plaques. The present work, despite being a pilot study comprising only a small number of subjects provides new insights in the search for specific cellular biomarkers with potential diagnostic and prognostic value in patients with a known carotid plaque.

Monocyte-to-HDL-cholesterol ratio as a prognostic marker in cardiovascular diseases

Inflammation and lipid accumulation are two basic hallmarks of atherosclerosis as a chronic disease. Inflammation not only is a local response but can also be considered as a systemic process followed by an elevation of inflammatory mediators. Monocytes are a major source of proinflammatory species during atherogenesis. In atherosclerosis, modified low-density lipoproteins (LDLs) are removed by macrophages; these are recruited in the vessel wall, inducing the release of inflammatory cytokines in inflamed tissue. Hence, inflammatory cholesterol ester-loaded plaque is generated. High-density lipoprotein-cholesterol (HDL-C) exhibits antiatherosclerotic effects by neutralizing the proinflammatory and pro-oxidant effects of monocytes via inhibiting the migration of macrophages and LDL oxidation in addition to the efflux of cholesterol from these cells. Furthermore, HDL plays a role in suppressing the activation of monocytes and proliferation-differentiation of monocyte progenitor cells. Thus, accumulation of monocytes and reduction of HDL-C may participate in atherosclerosis and cardiovascular diseases (CVD). Given that the relationship between the high number of monocytes and low HDL-C levels has been reported in inflammatory disorders, this review focused on understanding whether the monocyte-to-HDL ratio could be a convenient marker to predict atherosclerosis development and progression, hallmarks of CV events, instead of the individual monocyte count or HDL-C level.

Carotid vulnerable plaques are associated with circulating leukocytes in acute ischemic stroke patients: an clinical study based on contrast-enhanced ultrasound

Inflammatory activity plays a central role in the development of carotid rupture-vulnerable atherosclerotic plaques, which is one of the major contributors to acute ischemic stroke. Our objective was to characterize carotid intraplaque neovascularizations (INP) using contrast-enhanced ultrasound (CEUS) and evaluate plaque burden through exploring the relationship between INP and cell count of peripheral leukocytes. Sixty-two patients with large artery atherosclerosis (LAA) were enrolled in this study. CEUS was performed to characterize the carotid artery plaques. The correlations between the CEUS imaging features of carotid plaques and leukocyte counts were investigated. The results showed that the characteristic parameters derived from CEUS, including peak of time-intensity curve (TIC-P), mean of time-intensity curve (TIC-M), peak (FC-P), sharpness (FC-S) and area under the curve (FC-AUC) compared with the control group, were all increased in the stroke group. TIC-P, TIC-M and FC-P were negatively related to lymphocytes, respectively. FC-S and FC-AUC were positively correlated with neutrophils, respectively. Our study indicated carotid INP was closely related to the peripheral leukocytes count. CEUS may serve as a useful tool to predict vulnerability of plaque.

Fractal analysis of plaque border, a novel method for the quantification of atherosclerotic plaque contour irregularity, is associated with pro-atherogenic plasma lipid profile in subjects with non-obstructive carotid stenoses

BACKGROUND AND AIMS

Plaque border irregularity is a known imaging characteristic of vulnerable plaques, but its evaluation heavily relies on subjective evaluation and operator expertise. Aim of the present work is to propose a novel fractal-analysis based method for the quantification of atherosclerotic plaque border irregularity and assess its relation with cardiovascular risk factors.

METHODS AND RESULTS

Forty-two asymptomatic subjects with carotid stenosis underwent ultrasound evaluation and assessment of cardiovascular risk factors. Total, low-density lipoprotein (LDL), high-density lipoprotein (HDL) plasma cholesterol and triglycerides concentrations were measured for each subject. Fractal analysis was performed in all the carotid segments affected by atherosclerosis, i.e. 147 segments. The resulting fractal dimension (FD) is a measure of irregularity of plaque profile on long axis view of the plaque. FD in the severest stenosis (main plaque FD,mFD) was 1.136±0.039. Average FD per patient (global FD,gFD) was 1.145±0.039. FD was independent of other plaque characteristics. mFD significantly correlated with plasma HDL (r = -0.367,p = 0.02) and triglycerides-to-HDL ratio (r = 0.480,p = 0.002).

CONCLUSIONS

Fractal analysis is a novel, readily available, reproducible and inexpensive technique for the quantitative measurement of plaque irregularity. The correlation between low HDL levels and plaque FD suggests a role for HDL in the acquisition of morphologic features of plaque instability. Further studies are needed to validate the prognostic value of fractal analysis in carotid plaques evaluation.

Relation between characteristics of carotid atherosclerotic plaques and brain white matter hyperintensities in asymptomatic patients

White matter hyperintensities (WMH) can be incidentally found in patients with carotid atherosclerosis on brain magnetic resonance imaging (MRI). We investigated the relationship between WMH and characteristics of carotid plaques in asymptomatic patients without indication for carotid revascularization. We prospectively screened 235 consecutive patients with carotid stenosis <70%. After excluding patients with confounding causes of cerebral damage, 67 asymptomatic patients underwent carotid computed tomography angiography (CTA), contrast-enhanced ultrasound and brain MRI. Number and quantitative measurement of volume of WMH were associated with history of resistant hypertension, degree of stenosis (Doppler) and presence of an ulcerated plaque at CTA (p < 0.05). At multivariate regression analysis, resistant hypertension was independently associated with both number and volume of WMH, presence of an ulcer with number of WMH and degree of stenosis with WMH volume (p < 0.05), although WMH were equally distributed in both hemispheres irrespectively of plaque side. In conclusion, in asymptomatic patients with carotid plaques <70%, a higher burden of WMHs is associated with history of resistant hypertension that could be the expression of microvascular damage. Stenosis severity and presence of plaque ulceration are also associated with WMH burden although their causative relation is not supported by the bilateral distribution of WMH.