Vasa Vasorum Densities in Human Carotid Atherosclerosis Is Associated with Plaque Development and Vulnerability

Real-time Elastography and Contrast-Enhanced Ultrasound for Evaluating Adventitia in the Early Diagnosis of Vulnerable Plaques: an Exploratory Study Based on Histopathology

Vulnerable plaque is closely related to the occurrence of ischemic stroke. Therefore, early accurate identification of plaque vulnerability is crucial in risk stratification. In the development of vulnerable plaques, the change of the adventitia is earlier than that of the intima. Currently, researchers focused on the ultrasound detection of intraplaque and intima, but adventitia was often ignored in the examination. Real-time elastography technology (RTE) provides an estimation of adventitia stiffness, and contrast-enhanced ultrasound (CEUS) provides the quantification of adventitial VV. Therefore, we aimed to evaluate the value of adventitia in the early diagnosis of plaque vulnerability by combining CEUS and RTE based on histopathology. Rabbit carotid atherosclerosis models were established, and CEUS and RTE were performed. Normalized maximal video-intensity enhancement (MVE) was calculated to quantify adventitial VV density, and strain values were acquired to evaluate the adventitial elasticity. After removal of the lesion lumen, histological analysis of each excised plaque and adventitia was performed, and vulnerable plaques (n = 32) and stable group (n = 13) were distinguished. Normalized MVE of the adventitial VV and adventitial strain values in the vulnerable group was significantly higher than those in the stable group. Normalized MVE and strain values had a positive linear correlation with histological findings. Normalized MVE of the adventitial VV combined with adventitial strain values could identify plaque vulnerability with the area under the curve of 0.913 (sensitivity 90% and specificity 97%). Accordingly, the multimodal ultrasound detection strategy of adventitia has a high diagnostic value for early plaque vulnerability.

Cellular and Molecular Mechanisms of Mast Cells in Atherosclerotic Plaque Progression and Destabilization

Mast cells (MCs) are commonly recognized for their crucial involvement in the pathogenesis of allergic diseases, but over time, it has come to light that they also play a role in the pathophysiology of non-allergic disorders including atherosclerosis. The involvement of MCs in the pathology of atherosclerosis is supported by their accumulation in atherosclerotic plaques upon their progression and the association of intraplaque MC numbers with acute cardiovascular events. MCs that accumulate within the atherosclerotic plaque release a cocktail of mediators through which they contribute to neovascularization, plaque progression, instability, erosion, rupture, and thrombosis. At a molecular level, MC-released proteases, especially cathepsin G, degrade low-density lipoproteins (LDL) and mediate LDL fusion and binding of LDL to proteoglycans (PGs). Through a complicated network of chemokines including CXCL1, MCs promote the recruitment of among others CXCR2+ neutrophils, therefore, aggravating the inflammation of the plaque environment. Additionally, MCs produce extracellular traps which worsen inflammation and contribute to atherothrombosis. Altogether, evidence suggests that MCs actively, via several underlying mechanisms, contribute to atherosclerotic plaque destabilization and acute cardiovascular syndromes, thus, making the study of interventions to modulate MC activation an interesting target for cardiovascular medicine.

The microenvironment of the atheroma expresses phenotypes of plaque instability

Data from histopathology studies of human atherosclerotic tissue specimens and from vascular imaging studies support the concept that the local arterial microenvironment of a stable atheroma promotes destabilizing conditions that result in the transition to an unstable atheroma. Destabilization is characterized by several different plaque phenotypes that cause major clinical events such as acute coronary syndrome and cerebrovascular strokes. There are several rupture-associated phenotypes causing thrombotic vascular occlusion including simple fibrous cap rupture of an atheroma, fibrous cap rupture at site of previous rupture-and-repair of an atheroma, and nodular calcification with rupture. Endothelial erosion without rupture has more recently been shown to be a common phenotype to promote thrombosis as well. Microenvironment features that are linked to these phenotypes of plaque instability are neovascularization arising from the vasa vasorum network leading to necrotic core expansion, intraplaque hemorrhage, and cap rupture; activation of adventitial and perivascular adipose tissue cells leading to secretion of cytokines, growth factors, adipokines in the outer artery wall that destabilize plaque structure; and vascular smooth muscle cell phenotypic switching through transdifferentiation and stem/progenitor cell activation resulting in the promotion of inflammation, calcification, and secretion of extracellular matrix, altering fibrous cap structure, and necrotic core growth. As the technology evolves, studies using noninvasive vascular imaging will be able to investigate the transition of stable to unstable atheromas in real time. A limitation in the field, however, is that reliable and predictable experimental models of spontaneous plaque rupture and/or erosion are not currently available to study the cell and molecular mechanisms that regulate the conversion of the stable atheroma to an unstable plaque.

Connecting the Dots: How Injury in the Arterial Wall Contributes to Atherosclerotic Disease

PURPOSE

The occurrence and development of atherosclerotic cardiovascular disease, which can result in severe outcomes, such as myocardial infarction, stroke, loss of limb, renal failure, and infarction of the gut, are strongly associated with injury to the intimal component of the arterial wall whether via the inside-out or outside-in pathways. The role of injury to the tunica media as a pathway of atherosclerosis initiation is an underresearched area. This review focuses on potential pathways to vessel wall injury as well as current experimental and clinical research in the middle-aged and elderly populations, including the role of exercise, as it relates to injury to the tunica media.

METHODS

A database search using PubMed and Google Scholar was conducted for research articles published between 1909 and 2023 that focused on pathways of atherogenesis and the impact of mechanical forces on wall injury. The following key words were searched: wall injury, tunica media, atherogenesis, vascular aging, and wall strain. Studies were analyzed, and the relevant information was extracted from each study.

FINDINGS

A link between high mechanical stress in the arterial wall and reduced vascular compliance was found. The stiffening and calcification of the arterial wall with aging induce high blood pressure and pulse pressure, thereby causing incident hypertension and cardiovascular disease. In turn, prolonged high mechanical stress, particularly wall strain, applied to the arterial wall during vigorous exercise, results in stiffening and calcification of tunica media, accelerated arterial aging, and cardiovascular disease events. In both scenarios, the tunica media is the primary target of mechanical stress and the first to respond to hemodynamic changes. The cyclical nature of these impacts confounds the results of each because they are not mutually exclusive.

IMPLICATIONS

The role of stress in the tunica media appears to be overlooked despite its relevance, and further research into new primary preventive therapies is needed aside from cautioning the role of vigorous exercise in the elderly population.

Injury to the tunica media initiates atherogenesis in the presence of hyperlipidemia

Background and aims

Fatty streaks initiating the formation of atheromatous plaque appear in the tunica intima. The tunica media is not known to be a nidus for lipid accumulation initiating atherogenesis. We assessed changes to the tunica media in response to a micro-injury produced in the pig aorta. In addition, we assessed human carotid endarterectomy plaques for indication of atheroma initiation in the tunica media.

Methods

Three healthy landrace female pigs underwent laparotomy to inject autologous blood and create micro-hematomas at 6 sites within the tunica media of the infrarenal abdominal aorta. These pigs were fed a high-fat diet (HFD) for 4-12 weeks. Post-mortem aortas from all pigs, including a control group of healthy pigs, were serially stained to detect lipid deposits, vasa vasora (VV), immune cell infiltration and inflammatory markers, as well as changes to the vascular smooth muscle cell (vSMC) compartment. Moreover, 25 human carotid endarterectomy (CEA) specimens were evaluated for their lipid composition in the tunica media and intima.

Results

High lipid clusters, VV density, and immune cell infiltrates were consistently observed at 5 out of 6 injection sites under prolonged hyperlipidemia. The hyperlipidemic diet also affected the vSMC compartment in the tunica media adjacent to the tunica adventitia, which correlated with VV invasion and immune cell infiltration. Analysis of human carotid specimens post-CEA indicated that 32% of patients had significantly greater atheroma in the tunica media than in the arterial intima.

Conclusion

The arterial intima is not the only site for atherosclerosis initiation. We show that injury to the media can trigger atherogenesis.

Immune and non-immune mechanisms that determine vasculitis and coronary artery aneurysm topography in Kawasaki disease and MIS-C

The overlap between multisystem inflammatory syndrome in children (MIS-C) and Kawasaki disease (KD) including coronary artery aneurysms (CAA) and broadly shared gastrointestinal and mucocutaneous disease is poorly defined. In this perspective, we highlight common age-related extravascular epicardial microanatomical and immunological factors that might culminate in CAA expression in both MIS-C and KD. Specifically, the coronary vasa vasorum originates outside the major coronary arteries. Widespread inflammation in the epicardial interstitial compartment in shared between KD and MIS-C. Age-related changes in the neonatal and immature coronary vasculature including the impact of coronary artery biomechanical factors including coronary vessel calibre, age-related vessel distensibility, flow, and vessel neurovascular innervation may explain the decreasing CAA frequency from neonates to older children and the virtual absence of CAA in young adults with the MIS-C phenotype. Other KD and MIS-C features including mucocutaneous disease with keratinocyte-related immunopathology corroborate that disease phenotypes are centrally influenced by inflammation originating outside vessel walls but a potential role for primary coronary artery vascular wall inflammation cannot be excluded. Hence, common extravascular originating tissue-specific responses to aetiologically diverse triggers including superantigens may lead to widespread interstitial tissue inflammation characteristically manifesting as CAA development, especially in younger subjects. Given that CAA is virtually absent in adults, further studies are needed to ascertain whether epicardial interstitial inflammation may impact on both coronary artery physiology and cardiac conduction tissue and contribute to cardiovascular disease- a hitherto unappreciated consideration.

Targeting non-coding RNAs in unstable atherosclerotic plaques: Mechanism, regulation, possibilities, and limitations

Cardiovascular diseases (CVDs) caused by arteriosclerosis are the leading cause of death and disability worldwide. In the late stages of atherosclerosis, the atherosclerotic plaque gradually expands in the blood vessels, resulting in vascular stenosis. When the unstable plaque ruptures and falls off, it blocks the vessel causing vascular thrombosis, leading to strokes, myocardial infarctions, and a series of other serious diseases that endanger people's lives. Therefore, regulating plaque stability is the main means used to address the high mortality associated with CVDs. The progression of the atherosclerotic plaque is a complex integration of vascular cell apoptosis, lipid metabolism disorders, inflammatory cell infiltration, vascular smooth muscle cell migration, and neovascular infiltration. More recently, emerging evidence has demonstrated that non-coding RNAs (ncRNAs) play a significant role in regulating the pathophysiological process of atherosclerotic plaque formation by affecting the biological functions of the vasculature and its associated cells. The purpose of this paper is to comprehensively review the regulatory mechanisms involved in the susceptibility of atherosclerotic plaque rupture, discuss the limitations of current approaches to treat plaque instability, and highlight the potential clinical value of ncRNAs as novel diagnostic biomarkers and potential therapeutic strategies to improve plaque stability and reduce the risk of major cardiovascular events.

Mechanically Rotating Intravascular Ultrasound (IVUS) Transducer: A Review

Intravascular ultrasound (IVUS) is a valuable imaging modality for the diagnosis of atherosclerosis. It provides useful clinical information, such as lumen size, vessel wall thickness, and plaque composition, by providing a cross-sectional vascular image. For several decades, IVUS has made remarkable progress in improving the accuracy of diagnosing cardiovascular disease that remains the leading cause of death globally. As the quality of IVUS images mainly depends on the performance of the IVUS transducer, various IVUS transducers have been developed. Therefore, in this review, recently developed mechanically rotating IVUS transducers, especially ones exploiting piezoelectric ceramics or single crystals, are discussed. In addition, this review addresses the history and technical challenges in the development of IVUS transducers and the prospects of next-generation IVUS transducers.