Pathophysiology and Optimal Treatment of Intracranial Branch Atheromatous Disease.

Intracranial branch atheromatous disease (BAD) is a pathological condition characterized by the occlusion of a relatively large perforating branch (700-800 µm) near the orifice of a parent artery due to atherosclerotic plaque-based thrombus (microatheroma). BAD is refractory to treatment and follows a course of progressive exacerbation, especially motor paralysis. Uniform treatment for common atherothrombotic cerebral infarction or lacunar infarction does not prevent the progressive exacerbation of BAD, and consequently affects functional prognosis. To date, various combinations of treatments have been investigated and proposed to attenuate the worsening symptoms of BAD. However, no therapy with established efficacy is yet available for BAD. Since it is the most difficult condition to treat in the area of cerebral infarction, the establishment of optimal treatment methods for BAD is keenly awaited. This review presents an overview of the acute treatments available for BAD and discusses the prospects for optimal treatment.

Association of Coronary Plaque With Low-Density Lipoprotein Cholesterol Levels and Rates of Cardiovascular Disease Events Among Symptomatic Adults.

Importance: Atherosclerosis burden and coronary artery calcium (CAC) are associated with the risk for atherosclerotic cardiovascular disease (ASCVD) events, with absence of plaque and CAC indicating low risk. Whether this is true in patients with elevated levels of low-density lipoprotein cholesterol (LDL-C) is not known. Specifically, a high prevalence of noncalcified plaque might signal high risk. Objective: To determine the prevalence of noncalcified and calcified plaque in symptomatic adults and assess its association with cardiovascular events across the LDL-C spectrum. Design, Setting, and Participants: This cohort study included symptomatic patients undergoing coronary computed tomographic angiography from January 1, 2008, to December 31, 2017, from the seminational Western Denmark Heart Registry. Follow-up was completed on July 6, 2018. Data were analyzed from April 2 to December 2, 2021. Exposures: Prevalence of calcified and noncalcified plaque according to LDL-C strata of less than 77, 77 to 112, 113 to 154, 155 to 189, and at least 190 mg/dL. Severity of coronary artery disease was categorized using CAC scores of 0, 1 to 99, and ≥100, where higher numbers indicate greater CAC burden. Main Outcomes and Measures: Atherosclerotic cardiovascular disease events (myocardial infarction and stroke) and death. Results: A total of 23 143 patients with a median age of 58 (IQR, 50-65) years (12 857 [55.6%] women) were included in the analysis. During median follow-up of 4.2 (IQR, 2.3-6.1) years, 1029 ASCVD and death events occurred. Across all LDL-C strata, absence of CAC was a prevalent finding (ranging from 438 of 948 [46.2%] in patients with LDL-C levels of at least 190 mg/dL to 4370 of 7964 [54.9%] in patients with LDL-C levels of 77-112 mg/dL) and associated with no detectable plaque in most patients, ranging from 338 of 438 (77.2%) in those with LDL-C levels of at least 190 mg/dL to 1067 of 1204 (88.6%) in those with LDL-C levels of less than 77 mg/dL. In all LDL-C groups, absence of CAC was associated with low rates of ASCVD and death (6.3 [95% CI, 5.6-7.0] per 1000 person-years), with increasing rates in patients with CAC scores of 1 to 99 (11.1 [95% CI, 10.0-12.5] per 1000 person-years) and CAC scores of at least 100 (21.9 [95% CI, 19.9-24.4] per 1000 person-years). Among those with CAC scores of 0, the event rate per 1000 person-years was 6.3 (95% CI, 5.6-7.0) in the overall population compared with 6.9 (95% CI, 4.0-11.9) in those with LDL-C levels of at least 190 mg/dL. Across all LDL-C strata, rates were similar and low in those with CAC scores of 0, regardless of whether they had no plaque or purely noncalcified plaque. Conclusions and Relevance: The findings of this cohort study suggest that in symptomatic patients with severely elevated LDL-C levels of at least 190 mg/dL who are universally considered to be at high risk by guidelines, absence of calcified and noncalcified plaque on coronary computed tomographic angiography was associated with low risk for ASCVD events. These results further suggest that atherosclerosis burden, including CAC, can be used to individualize treatment intensity in patients with severely elevated LDL-C levels.

Effect of Calcification Based on Computer-Aided System on CT-Fractional Flow Reserve in Diagnosis of Coronary Artery Lesion.

This study was to analyze the diagnostic value of coronary computed tomography angiography (CCTA) and fractional flow reserve (FFR) based on computer-aided diagnosis (CAD) system for coronary lesions and the possible impact of calcification. 80 patients who underwent CCTA and FFR examination in hospital were selected as the subjects. The FFR value of 0.8 was used as the dividing line and divided into the ischemic group (FFR ≤ 0.8) and nonischemic group (FFR > 0.8). The basic data and imaging characteristics of patients were analyzed. The maximum diameter stenosis rate (MDS %), maximum area stenosis rate (MAS %), and napkin ring sign (NRS) in the ischemic group were significantly lower than those in the nonischemic group (P < 0.05). Remodeling index (RI) and eccentric index (EI) compared with the nonischemic group had no significant difference (P > 0.05). The total plaque volume (TPV), total plaque burden (TPB), calcified plaque volume (CPV), lipid plaque volume (LPV), and lipid plaque burden (LPB) in the ischemic group were significantly different from those in the non-ischemic group (P < 0.05). MAS % had the largest area under curve (AUC) for the diagnosis of coronary myocardial ischemia (0.74), followed by MDS % (0.69) and LPV (0.68). CT-FFR had high diagnostic sensitivity, specificity, accuracy, truncation value, and AUC area data for patients in the ischemic group and nonischemic group. The diagnostic sensitivity, specificity, accuracy, cutoff value, and AUC area data of CT-FFR were higher in the ischemic group (89.93%, 92.07%, 95.84%, 60.51%, 0.932) and nonischemic group (93.75%, 90.88%, 96.24%, 58.22%, 0.944), but there were no significant differences between the two groups (P > 0.05). In summary, CT-FFR based on CAD system has high accuracy in evaluating myocardial ischemia caused by coronary artery stenosis, and within a certain range of calcification scores, calcification does not affect the diagnostic accuracy of CT-FFR.

Normalized Subendocardial Myocardial Attenuation on Coronary Computed Tomography Angiography Predicts Postoperative Adverse Cardiovascular Events: Coronary CTA VISION Substudy.

BACKGROUND: Abnormalities in computed tomography myocardial perfusion has been associated with coronary artery disease and major adverse cardiovascular events (MACE). We sought to investigate if subendocardial attenuation using coronary computed tomography angiography predicts MACE 30 days postelective noncardiac surgery. METHODS: Using a 17-segment model, coronary computed tomography angiography images were analyzed for subendocardial and transmural attenuation and the corresponding blood pool. The segment with the lowest subendocardial attenuation and transmural attenuation were normalized to the segment with the highest subendocardial and transmural attenuation, respectively (SUBnormalized, and TRANSnormalized, respectively). We evaluated the independent and incremental value of myocardial attenuation to predict the composite of cardiovascular death or nonfatal myocardial infarction. RESULTS: Of a total of 995 coronary CTA VISION (Coronary Computed Tomographic Angiography and Vascular Events in Noncardiac Surgery Patients Cohort Evaluation Study) patients, 735 had available images and complete data for these analyses. Among these patients, 60 had MACE. Based on Revised Cardiovascular Risk Index, 257, 302, 138, and 38 patients had scores of 0, 1, 2, and ≥3, respectively. On coronary computed tomography angiography, 75 patients had normal coronary arteries, 297 patients had nonobstructive coronary artery disease, 264 patients had obstructive disease, and 99 patients had extensive obstructive coronary artery disease. SUBnormalized was an independent and incremental predictor of events in the model that included Revised Cardiovascular Risk Index and coronary artery disease severity. Compared with patients in the highest tertile of SUBnormalized, patients in the second and first tertiles had an increased hazards ratio for events (2.23 [95% CI, 1.091-4.551] and 2.36 [95% CI, 1.16-4.81], respectively). TRANSnormalized, as a continuous variable, was also found to be a predictor of MACE (P=0.027). CONCLUSIONS: Our study demonstrates that SUBnormalized and TRANSnormalized are independent and incremental predictors of MACE 30 days after elective noncardiac surgery. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01635309.

Prolonged sitting time links to subclinical atherosclerosis.

BACKGROUND: This study investigates the association between daily sitting time and subclinical atherosclerosis by using coronary computed tomography angiography (CCTA). METHODS: The study enrolled 203 subjects (age 57.6 ± 8.8 years) who underwent CCTA at annual medical checkups. Sitting time was categorized as < 5 hours/day (short), 5 to 9 hours/day (moderate) and ≥10 hours/d (long). We analyzed the coronary calcium score, plaque characteristics, and severity of coronary artery stenosis, including the segment involvement score (SIS) and segment stenosis score (SSS). RESULTS: Subjects with longer sitting times tended to be male gender and have lower levels of high-density lipoprotein cholesterol (p for trend < 0.05). In addition, those with longer sitting time had higher SIS (1.2 ± 1.5 vs. 1.6 ± 2.1 vs. 2.3 ± 2.0 for short, moderate, and long sitting time, respectively) (p for trend = 0.015) and SSS (1.4 ± 2.0 vs. 1.9 ± 2.7 vs. 2.7 ± 2.6) (p for trend = 0.015), suggesting longer sitting time-correlated with the severity of coronary atherosclerosis. When considering the coronary plaque patterns, subjects with shorter sitting time (<5 hours/d) tended to have more calcified plaque and subjects with longer sitting time (≥10 hours/d) had more mixed plaque (p for trend = 0.018). After adjusting for age, gender, comorbidities, body mass index, and lipid profiles, increased sitting time was independently associated with the presence of mixed plaque, suggesting longer sitting time may be associated with higher risk of the formation of vulnerable plaque. CONCLUSION: Longer sitting time was linked to the severity of subclinical atherosclerosis and the presence of high-risk vulnerable plaque in the general population.

Predictive mouse model reflects distinct stages of human atheroma in a single carotid artery.

Identification of patients with high-risk asymptomatic atherosclerotic plaques remains an elusive but essential step in preventing stroke. However, there is a lack of animal model that provides a reproducible method to predict where, when and what types of plaque formation, which fulfils the American Heart Association (AHA) histological classification of human plaques. We have developed a predictive mouse model that reflects different stages of human plaques in a single carotid artery by means of shear-stress modifying cuff. Validated with over 30000 histological sections, the model generates a specific pattern of plaques with different risk levels along the same artery depending on their position relative to the cuff. The further upstream of the cuff-implanted artery, the lower the magnitude of shear stress, the more unstable the plaques of higher grade according to AHA classification; with characteristics including greater degree of vascular remodeling, plaque size, plaque vulnerability and inflammation, resulting in higher risk plaques. By weeks 20 and 30, this model achieved 80% and near 100% accuracy respectively, in predicting precisely where, when and what stages/AHA types of plaques develop along the same carotid artery. This model can generate clinically-relevant plaques with varying phenotypes fulfilling AHA classification and risk levels, in specific locations of the single artery with near 100% accuracy of prediction. The model offers a promising tool for development of diagnostic tools to target high-risk plaques, increasing accuracy in predicting which individual patients may require surgical intervention to prevent stroke, paving the way for personalized management of carotid atherosclerotic disease.

The Key Genes Underlying Pathophysiology Association between Plaque Instability and Progression of Myocardial Infarction.

Young patients with type 2 diabetes and myocardial infarction (MI) have higher long-term all-cause and cardiovascular mortality. In addition, the observed increased, mildly abnormal baseline lipid levels, but not lipid variability, are associated with an increased risk of atherosclerotic cardiovascular disease events, particularly MI. This study investigated differentially expressed genes (DEGs), which might be potential targets for young patients with MI and a high-fat diet (HFD). GSE114695 and GSE69187 were downloaded and processed using the limma package. A Venn diagram was applied to identify the same DEGs, and further pathway analysis was performed using Metascape. Protein-protein interaction (PPI) network analysis was then applied, and the hub genes were screened out. Pivotal miRNAs were predicted and validated using the miRNA dataset in GSE114695. To investigate the cardiac function of the screened genes, an MI mouse model, echocardiogram, and ELISA of hub genes were applied, and a correlation analysis was also performed. From aged mice fed HFD, 138 DEGs were extracted. From aged mice fed with chow, 227 DEGs were extracted. Pathway enrichment analysis revealed that DEGs in aging mice fed HFD were enriched in lipid transport and lipid biosynthetic process 1 d after MI and in the MAPK signaling pathway at 1 w after MI, suggesting that HFD has less effect on aging with MI. A total of 148 DEGs were extracted from the intersection between plaques fed with HFD and chow in young mice and MI_1d, respectively, which demonstrated increased inflammatory and adaptive immune responses, in addition to myeloid leukocyte activation. A total of 183 DEGs were screened out between plaques fed with HFD vs. chow in young mice and MI_1w, respectively, which were mainly enriched in inflammatory response, cytokine production, and myeloid leukocyte activation. After validation, PAK3, CD44, CD5, SOCS3, VAV1, and PIK3CD were demonstrated to be negatively correlated with LVEF; however, P2RY1 was demonstrated to be positively correlated. This study demonstrated that the screened hub genes may be therapeutic targets for treating STEMI patients and preventing MI recurrence, especially in young MI patients with HFD or diabetes.

Impact of H-Type Hypertension on Pericarotid Adipose Tissue and Plaque Characteristics Based on Computed Tomography (CT) Angiography: A Propensity Score Matching Study.

BACKGROUND We analyzed the correlation among the inflammatory changes in pericarotid adipose tissue (PCAT), plaque characteristics, and H-type hypertension on CT angiography (CTA) and explored the utility of CTA in the prevention and treatment of carotid atherosclerosis. MATERIAL AND METHODS A total of 135 patients who underwent head and neck CTA to investigate carotid artery atherosclerosis were retrospectively analyzed. The plaque characteristic parameters (plaque burden and remodeling index), PCAT attenuation value, and net enhancement value around the carotid artery, where the plaques were located, were recorded, and confounding factors were matched by propensity score analysis. A paired t test was used to compare the differences in fat tissue inflammatory changes and plaque characteristic parameters between the 2 groups, and logistic regression analysis was used to evaluate the relationship between plaque characteristics and the attenuation values and net enhancement values of PCAT. The correlation coefficient was calculated between type H hypertension and plaque risk grade. RESULTS The results of the experiment indicate that PCAT attenuation values and net enhancement values gradually increased as the degree of hypertension increased. Compared with those of patients in the normal Hcy group, these values increased more clearly in patients with high Hcy (HHcy) (r=0.641, P<0.001, r=0.581, P<0.001), although, regardless of whether the Hcy value increased, there were significant differences between the groups. However, this effect was more pronounced in patients with H-type hypertension. Logistic regression analysis of risk factors for carotid atherosclerotic plaque suggests that Hcy (OR=1.391, 95% CI 1.146-1.689, P=0.001), PCAT attenuation values (OR=1.212, 95% CI 1.074-1.367, P=0.002), and net enhancement values (OR=1.201, 95% CI 1.042-1.383, P=0.011) were independent risk factors for plaque vulnerability. CONCLUSIONS Our results suggest that H-type hypertension is significantly associated with PCAT attenuation and net enhancement and that PCAT net enhancement values are useful in predicting plaque risk as attenuation.

Inflammation Drives Stiffness Mediated Uptake of Lipoproteins in Primary Human Macrophages and Foam Cell Proliferation.

Macrophage to foam cell transition and their accumulation in the arterial intima are the key events that trigger atherosclerosis, a multifactorial inflammatory disease. Previous studies have linked arterial stiffness and cardiovascular disease and have highlighted the use of arterial stiffness as a potential early-stage marker. Yet the relationship between arterial stiffness and atherosclerosis in terms of macrophage function is poorly understood. Thus, it is pertinent to understand the mechanobiology of macrophages to clarify their role in plaque advancement. We explore how substrate stiffness affects proliferation of macrophages and foam cells, traction forces exerted by macrophages and uptake of native and oxidized low-density lipoproteins. We demonstrate that stiffness influences foam cell proliferation under both naïve and inflammatory conditions. Naïve foam cells proliferated faster on the 4 kPa polyacrylamide gel and glass whereas under inflammatory conditions, maximum proliferation was recorded on glass. Macrophage and foam cell traction forces were positively correlated to the substrate stiffness. Furthermore, the influence of stiffness was demonstrated on the uptake of lipoproteins on macrophages treated with lipopolysaccharide + interferon gamma. Cells on softer 1 kPa substrates had a significantly higher uptake of low-density lipoproteins and oxidized low-density lipoproteins compared to stiffer substrates. The results herein indicate that macrophage function is modulated by stiffness and help better understand ways in which macrophages and foam cells could contribute to the development and progression of atherosclerotic plaque.

IRGM/Irgm1 facilitates macrophage apoptosis through ROS generation and MAPK signal transduction: Irgm1+/- mice display increases atherosclerotic plaque stability.

Rationale: Atherosclerosis plaque rupture (PR) is the pathological basis and chief culprit of most acute cardiovascular events and death. Given the complex and important role of macrophage apoptosis and autophagy in affecting plaque stability, an important unanswered question include is whether, and how, immunity-related GTPase family M protein (IRGM) and its mouse orthologue IRGM1 affect macrophage survival and atherosclerotic plaque stability. Methods: To investigate whether serum IRGM of ST-segment elevation myocardial infarction (STEMI) patients is related to plaque morphology, we divided 85 STEMI patients into those with and without plaque rupture (PR and non-PR, respectively) based on OCT image analysis, and quantified the patients' serum IRGM levels. Next, we engineered Irgm1 deficient mice (Irgm1+/-) and chimera mice with Irgm1 deficiency in the bone marrow on an ApoE-/- background, which were then fed a high-fat diet for 16 weeks. Pathological staining was used to detect necrotic plaque cores, ratios of neutral lipids and cholesterol crystal, as well as collagen fiber contents in these mice to characterize plaque stability. In addition, immunofluorescence, immunohistochemical staining and western blot were used to detect the apoptosis of macrophages in the plaques. In vitro, THP-1 and RAW264.7 cells were stimulated with ox-LDL to mimic the in vivo environment, and IRGM/IRGM1 expression were modified by specific siRNA (knockdown) or IRGM plasmid (knocked-in). The effect of IRGM/Irgm1 on autophagy and apoptosis of macrophages induced by ox-LDL was then evaluated. In addition, we introduced inhibitors of the JNK/p38/ERK signaling pathway to verify the specific mechanism by which Irgm1 regulates RAW264.7 cell apoptosis. Results: The serum IRGM levels of PR patients is significantly higher than that of non-PR patients and healthy volunteers, which may be an effective predictor of PR. On a high-fat diet, Irgm1-deficient mice exhibit reduced necrotic plaque cores, as well as neutral lipid and cholesterol crystal ratios, with increased collagen fiber content. Additionally, macrophage apoptosis is inhibited in the plaques of Irgm1-deficient mice. In vitro, IRGM/Irgm1 deficiency rapidly inhibits ox-LDL-induced macrophage autophagy while inhibiting ox-LDL-induced macrophage apoptosis in late stages. Additionally, IRGM/Irgm1 deficiency suppresses reactive oxygen species (ROS) production in macrophages, while removal of ROS effectively inhibits macrophage apoptosis induced by IRGM overexpression. We further show that Irgm1 can affect macrophage apoptosis by regulating JNK/p38/ERK phosphorylation in the MAPK signaling pathway. Conclusions: Serum IRGM may be related to the process of PR in STEMI patients, and IRGM/Irgm1 deficiency increases plaque stability. In addition, IRGM/Irgm1 deficiency suppresses macrophage apoptosis by inhibiting ROS generation and MAPK signaling transduction. Cumulatively, these results suggest that targeting IRGM may represent a new treatment strategy for the prevention and treatment of acute cardiovascular deaths caused by PR.

Optical Coherence Tomography of Coronary Plaque Progression and Destabilization: JACC Focus Seminar Part 3/3.

The development of optical coherence tomography (OCT) has revolutionized our understanding of coronary artery disease. In vivo OCT research has paralleled with advances in computational fluid dynamics, providing additional insights in the various hemodynamic factors influencing plaque growth and stability. Recent OCT studies introduced a new concept of plaque healing in relation to clinical presentation. In addition to known mechanisms of acute coronary syndromes such as plaque rupture and plaque erosion, a new classification of calcified plaque was recently reported. This review will focus on important new insights that OCT has provided in recent years into coronary plaque development, progression, and destabilization, with a focus on the role of local hemodynamics and endothelial shear stress, the layered plaque (signature of previous subclinical plaque destabilization and healing), and the calcified culprit plaque.

Status of biomarkers for the identification of stable or vulnerable plaques in atherosclerosis.

Atherosclerosis is a systemic inflammation of the arteries characterized by atherosclerotic plaque due to the accumulation of lipids, inflammatory cells, apoptotic cells, calcium and extracellular matrix (ECM) proteins. Stable plaques present a chronic inflammatory infiltration, whereas vulnerable plaques present an 'active' inflammation involved in the thinning of the fibrous cap that predisposes to plaque rupture. Several complex biological cellular processes lead plaques to evolve from stable to vulnerable predisposing them to rupture and thrombosis. In this review, we analyze some emerging circulating biomarkers related to inflammation, ECM and lipid infiltration, angiogenesis, metalloproteinases and microRNA (miRNA), as possible diagnostic and prognostic indicators of plaque vulnerability.

DNA methylome profiling reveals epigenetic regulation of lipoprotein-associated phospholipase A2 in human vulnerable atherosclerotic plaque.

BACKGROUND: Atherosclerotic plaque vulnerability is a key feature of atheroprogression and precipitating acute cardiovascular events. Although the pivotal role of epigenetic regulation in atherosclerotic plaque destabilization is being recognized, the DNA methylation profile and its potential role in driving the progression and destabilization of atherosclerotic cardiovascular disease remains largely unknown. We conducted a genome-wide analysis to identify differentially methylated genes in vulnerable and non-vulnerable atherosclerotic lesions to understand more about pathogenesis. RESULTS: We compared genome-wide DNA methylation profiling between carotid artery plaques of patients with clinically symptomatic (recent stroke or transient ischemic attack) and asymptomatic disease (no recent stroke) using Infinium Methylation BeadChip arrays, which revealed 90,368 differentially methylated sites (FDR < 0.05, |delta beta|> 0.03) corresponding to 14,657 annotated genes. Among these genomic sites, 30% were located at the promoter regions and 14% in the CpG islands, according to genomic loci and genomic proximity to the CpG islands, respectively. Moreover, 67% displayed hypomethylation in symptomatic plaques, and the differentially hypomethylated genes were found to be involved in various aspects of inflammation. Subsequently, we focus on CpG islands and revealed 14,596 differentially methylated sites (|delta beta|> 0.1) located at the promoter regions of 7048 genes. Integrated analysis of methylation and gene expression profiles identified that 107 genes were hypomethylated in symptomatic plaques and showed elevated expression levels in both advanced plaques and ruptured plaques. The imprinted gene PLA2G7, which encodes lipoprotein-associated phospholipase A2 (Lp-PLA2), was one of the top hypomethylated genes with an increased expression upon inflammation. Further, the hypomethylated CpG site at the promoter region of PLA2G7 was identified as cg11874627, demethylation of which led to increased binding of Sp3 and expression of Lp-PLA2 through bisulfate sequencing, chromatin immunoprecipitation assay and enzyme-linked immunosorbent assay. These effects were further enhanced by deacetylase. CONCLUSION: Extensive DNA methylation modifications serve as a new and critical layer of biological regulation that contributes to atheroprogression and destabilization via inflammatory processes. Revelation of this hitherto unknown epigenetic regulatory mechanism could rejuvenate the prospects of Lp-PLA2 as a therapeutic target to stabilize the atherosclerotic plaque and reduce clinical sequelae.

Mechanical characterization of 3D printed mimic of human artery affected by atherosclerotic plaque through numerical and experimental methods.

This paper proposes a novel experimental investigation based on 3D printing to validate numerical models for biomechanics simulations. Soft elastomeric materials have been used in Polyjet multi-material 3D printer to mimicking arteries affected by atherosclerotic plaque. The nonlinear mechanical properties of five digital materials are characterized and used as an input for finite element (FE) modeling. Pressurized air is applied to the internal cavity of the printed model to reproduce the internal blood pressure in the artery. Digital Imaging Correlation is adopted to measure the displacement and deformation. A 1D linear higher-order FE model based on the Carrera Unified Formulation is compared to 3D nonlinear FE solutions.

Studying dynamic stress effects on the behaviour of THP-1 cells by microfluidic channels.

Atherosclerosis is a long-term disease process of the vascular system that is characterized by the formation of atherosclerotic plaques, which are inflammatory regions on medium and large-sized arteries. There are many factors contributing to plaque formation, such as changes in shear stress levels, rupture of endothelial cells, accumulation of lipids, and recruitment of leukocytes. Shear stress is one of the main factors that regulates the homeostasis of the circulatory system; therefore, sudden and chronic changes in shear stress may cause severe pathological conditions. In this study, microfluidic channels with cavitations were designed to mimic the shape of the atherosclerotic blood vessel, where the shear stress and pressure difference depend on design of the microchannels. Changes in the inflammatory-related molecules ICAM-1 and IL-8 were investigated in THP-1 cells in response to applied shear stresses in an continuous cycling system through microfluidic channels with periodic cavitations. ICAM-1 mRNA expression and IL-8 release were analyzed by qRT-PCR and ELISA, respectively. Additionally, the adhesion behavior of sheared THP-1 cells to endothelial cells was examined by fluorescence microscopy. The results showed that 15 Pa shear stress significantly increases expression of ICAM-1 gene and IL-8 release in THP-1 cells, whereas it decreases the adhesion between THP-1 cells and endothelial cells.

Investigation of Wall Shear Stress in Cardiovascular Research and in Clinical Practice-From Bench to Bedside.

In the 1900s, researchers established animal models experimentally to induce atherosclerosis by feeding them with a cholesterol-rich diet. It is now accepted that high circulating cholesterol is one of the main causes of atherosclerosis; however, plaque localization cannot be explained solely by hyperlipidemia. A tremendous amount of studies has demonstrated that hemodynamic forces modify endothelial athero-susceptibility phenotypes. Endothelial cells possess mechanosensors on the apical surface to detect a blood stream-induced force on the vessel wall, known as "wall shear stress (WSS)", and induce cellular and molecular responses. Investigations to elucidate the mechanisms of this process are on-going: on the one hand, hemodynamics in complex vessel systems have been described in detail, owing to the recent progress in imaging and computational techniques. On the other hand, investigations using unique in vitro chamber systems with various flow applications have enhanced the understanding of WSS-induced changes in endothelial cell function and the involvement of the glycocalyx, the apical surface layer of endothelial cells, in this process. In the clinical setting, attempts have been made to measure WSS and/or glycocalyx degradation non-invasively, for the purpose of their diagnostic utilization. An increasing body of evidence shows that WSS, as well as serum glycocalyx components, can serve as a predicting factor for atherosclerosis development and, most importantly, for the rupture of plaques in patients with high risk of coronary heart disease.

Nonlinear multiscale analysis of coronary atherosclerotic vulnerable plaque artery: fluid-structural modeling with micromechanics.

A unique three-dimensional (3D) computational multiscale modeling approach is proposed to investigate the influence of presence of microcalcification particles on the stress field distribution in the thin cap layer of a coronary atherosclerotic vulnerable plaque system. A nested 3D modeling analysis framework spanning the multiscale nature of a coronary atherosclerotic vulnerable plaque is presented. At the microscale level, a micromechanical modeling approach, which is based on computational finite-element (FE) representative unit cell, is applied to obtain the homogenized nonlinear response of the calcified tissue. This equivalent response effectively allows the integration of extremely small microcalcification inclusions in a global biomechanical FE model. Next, at the macroscale level, a 3D patient-based fluid-structure interaction FE model, reconstructing a refined coronary artery geometry with calcified plaque lesion, is generated to study the mechanical behavior of such multi-component biomechanical system. It is shown that the proposed multiscale modeling approach can generate a higher resolution of stress and strain field distributions within the coronary atherosclerotic vulnerable plaque system and allow the assessment of the local concentration stress around the microcalcifications in plaque cap layers. A comparison of stress field distributions within cap layers with and without inclusion of microcalcifications is also presented.

Extracellular vesicles from monocyte/platelet aggregates modulate human atherosclerotic plaque reactivity.

Extracellular vesicles (EVs) are emerging as key players in different stages of atherosclerosis. Here we provide evidence that EVs released by mixed aggregates of monocytes and platelets in response to TNF-α display pro-inflammatory actions on endothelial cells and atherosclerotic plaques. Tempering platelet activation with Iloprost, Aspirin or a P2Y12 inhibitor impacted quantity and phenotype of EV produced. Proteomics of EVs from cells activated with TNF-α alone or in the presence of Iloprost revealed a distinct composition, with interesting hits like annexin-A1 and gelsolin. When added to human atherosclerotic plaque explants, EVs from TNF-α stimulated monocytes augmented release of cytokines. In contrast, EVs generated by TNF-α together with Iloprost produced minimal plaque activation. Notably, patients with coronary artery disease that required percutaneous coronary intervention had elevated plasma numbers of monocyte, platelet as well as double positive EV subsets. In conclusion, EVs released following monocyte/platelet activation may play a potential role in the development and progression of atherosclerosis. Whereas attenuating platelet activation modifies EV composition released from monocyte/platelet aggregates, curbing their pro-inflammatory actions may offer therapeutic avenues for the treatment of atherosclerosis.