Calcium regulates key components of vascular smooth muscle cell-derived matrix vesicles to enhance mineralization

The role of SERCA in vascular diseases, a potential therapeutic target

SERCA, the sarco/endoplasmic reticulum Ca2+-ATPase, is a pivotal protein that transports calcium ions (Ca2+) from the cytoplasm into the sarcoplasmic/endoplasmic reticulum (SR/ER), thus sustaining cellular Ca2+ homeostasis. A growing body of evidence indicates that SERCA dysfunction correlates with disrupted cellular Ca2+ homeostasis and ER stress, precipitating a spectrum of chronic diseases. As a regulator of Ca2+ homeostasis, SERCA emerges as a potential therapeutic target for conditions associated with Ca2+ imbalance. This review delineates the association between SERCA and a variety of vascular diseases.

Molecular imaging of cardiovascular disease: Current status and future perspective

Advancements in knowledge of cardiovascular disease, pharmacology, and chemistry have led to the development of newer radiopharmaceuticals and targets for new and more suitable molecules. Molecular imaging encompasses multiple imaging techniques for identifying the characteristics of key components involved in disease. Despite its limitations in spatial resolution, the affinity for key molecules compensates for disadvantages in diagnosing diseases and elucidating their pathophysiology. This review introduce established molecular tracers involved in clinical practice and emerging tracers already applied in clinical studies, classifying the key component in A: artery, specifically those vulnerable plaque (A-I) inflammatory cells [18F-FDG]; A-II) lipid/fatty acid; A-III) hypoxia; A-IV) angiogenesis; A-V) protease [18F/68Ga-FAPI]; A-VI) thrombus/hemorrhage; A-VII) apoptosis and A-VIII) microcalcification [18F-NaF]) and B: myocardium, including myocardial ischemia, infarction and myocardiopathy (B-I) myocardial ischemia; B-II) myocardial infarction (myocardial damage and fibrosis); B-III) myocarditis and endocarditis; B-IV) sarcoidosis; B-V) amyloidosis; B-VI) metabolism; B-VII) innervation imaging). In addition to cardiovascular-specific tracers tested in animal models, many radiotracers may have been developed in other areas, such as oncology imaging or neuroimaging. While this review does not cover all available tracers, some of them hold potential for future use assessing cardiovascular disease. Advances in molecular biology, pharmaceuticals, and imaging sciences will facilitate the identification of precise disease mechanisms, enabling precise diagnoses, better assessment of disease status, and enhanced therapeutic evaluation in this multi-modality era.

Collagen-mediated cardiovascular calcification

Cardiovascular calcification is a pathological process commonly observed in the elderly. Based on the location of the calcification, cardiovascular calcification can be classified into two main types: vascular calcification and valvular calcification. Collagen plays a critical role in the development of cardiovascular calcification lesions. The content and type of collagen are the result of a dynamic balance between synthesis and degradation. Unregulated processes can lead to adverse outcomes. During cardiovascular calcification, collagen not only serves as a scaffold for ectopic mineral deposition but also acts as a signal transduction pathway that mediates calcification by guiding the aggregation and nucleation of matrix vesicles and promoting the proliferation, migration and phenotypic changes of cells involved in the lesion. This review provides an overview of collagen subtypes in the cardiovascular system under physiological conditions and discusses their distribution. Additionally, we introduce pathological changes and mechanisms of collagen in blood vessels and heart valves. Then, the formation process and characteristic stages of cardiovascular calcification are described. Finally, we highlight the role of collagen in cardiovascular calcification, explore strategied for mediating calcification, and suggest potential directions for future research.

The Role of Serum Calcium Levels in the Progression of Arterial Stiffness: Cross-Sectional and Longitudinal Analyses in a Multicenter Cohort

Increased arterial stiffness measured by brachial-ankle pulse wave velocity (baPWV) is a well-known risk factor for hypertension and future cardiovascular events. The relationship between serum calcium levels and increased arterial stiffness is not well understood. Individuals undergoing baPWV measurements as part of a generalized health examination, with normal serum calcium (8.5-10.5 mg/dL) and phosphate levels and no significant renal dysfunction, were selected from the Korea Initiatives on Coronary Artery (KOICA) registry. The cross-sectional relationship between serum calcium levels and baPWV, and the longitudinal effect of baseline serum calcium levels on baPWV progression in those with repeated baPWV measurements, were analyzed using multivariable regression models. A total of 9150 individuals with baseline baPWV and 2329 individuals (5451 PWV measurements) with follow-up baPWV were selected for cross-sectional and longitudinal analyses, respectively. After adjustment for confounders, higher serum calcium levels were associated with increased baseline baPWV (β-coefficient per 1 mg/dL increase, 19.61; 95% CI 7.77-31.45; p = 0.001). Higher serum calcium was also independently associated with a greater annualized baPWV progression rate longitudinally (β-coefficient per 1 mg/dL increase, 5.17; 95% CI, 1.82-8.67; p = 0.004). Subgroup analysis showed that the effect of serum calcium on baPWV progression had a significant interaction with baseline baPWV, systolic blood pressure, and the presence of diabetes (interaction p < 0.001). In conclusion, higher serum calcium levels within the normal range were associated with faster arterial stiffness progression measured by baPWV. Further studies are required to explore the potential for modulating calcium metabolism to slow arterial stiffness progression.

Investigating the role of elastin and extracellular matrix damage in cardiovascular calcification

Although calcification in the cardiovascular system is highly studied, the mechanisms behind it are not well understood. Current proposed mechanisms focus on cellular processes leading to, or controlling the unwanted mineralization in soft tissues. However, extracellular components such as collagen and elastin fundamentally regulate the mechanical properties of heart tissues. Here, we report on a toolkit to control the composition of tissues through the selective digestion of extracellular matrix (ECM) components, which can be used to design disease-specific in vitro models. Using this technique, we show that elastin as well as matrix tissue damage may play major role in cardiovascular calcification. This study highlights a novel approach to understand the role of proteins in soft tissue calcifications and may lead to the development of strategies to treat and prevent these unwanted pathological disorders.

ECM Modifications Driven by Age and Metabolic Stress Directly Promote Vascular Smooth Muscle Cell Osteogenic Processes

BACKGROUND

The ECM (extracellular matrix) provides the microenvironmental niche sensed by resident vascular smooth muscle cells (VSMCs). Aging and disease are associated with dramatic changes in ECM composition and properties; however, their impact on VSMC phenotype remains poorly studied.

METHODS

Here, we describe a novel in vitro model system that utilizes endogenous ECM to study how modifications associated with age and metabolic disease impact VSMC phenotype. ECM was synthesized using primary human VSMCs and modified during culture or after decellularization. Integrity, stiffness, and composition of the ECM was measured using superresolution microscopy, atomic force microscopy, and proteomics, respectively. VSMCs reseeded onto the modified ECM were analyzed for viability and osteogenic differentiation.

RESULTS

ECMs produced in response to mineral stress showed extracellular vesicle-mediated hydroxyapatite deposition and sequential changes in collagen composition and ECM properties. VSMCs seeded onto the calcified ECM exhibited increased extracellular vesicle release and Runx2 (Runt-related transcription factor 2)-mediated osteogenic gene expression due to the uptake of hydroxyapatite, which led to increased reactive oxygen species and the induction of DNA damage signaling. VSMCs seeded onto the nonmineralized, senescent ECM also exhibited increased Runx2-mediated osteogenic gene expression and accelerated calcification. In contrast, glycated ECM specifically induced increased ALP (alkaline phosphatase) activity, and this was dependent on RAGE (receptor for advanced glycation end products) signaling with both ALP and RAGE receptor inhibition attenuating calcification.

CONCLUSIONS

ECM modifications associated with aging and metabolic disease can directly induce osteogenic differentiation of VSMCs via distinct mechanisms and without the need for additional stimuli. This highlights the importance of the ECM microenvironment as a key driver of phenotypic modulation acting to accelerate age-associated vascular pathologies and provides a novel model system to study the mechanisms of calcification.

Understanding Vascular Calcification in Chronic Kidney Disease: Pathogenesis and Therapeutic Implications

Vascular calcification (VC) is a biological phenomenon characterized by an accumulation of calcium and phosphate deposits within the walls of blood vessels causing the loss of elasticity of the arterial walls. VC plays a crucial role in the incidence and progression of chronic kidney disease (CKD), leading to a significant increase in cardiovascular mortality in these patients. Different conditions such as age, sex, dyslipidemia, diabetes, and hypertension are the main risk factors in patients affected by chronic kidney disease. However, VC may occur earlier and faster in these patients if it is associated with new or non-traditional risk factors such as oxidative stress, anemia, and inflammation. In chronic kidney disease, several pathophysiological processes contribute to vascular calcifications, including osteochondrogenic differentiation of vascular cells, hyperphosphatemia and hypercalcemia, and the loss of specific vascular calcification inhibitors including pyrophosphate, fetuin-A, osteoprotegerin, and matrix GLA protein. In this review we discuss the main traditional and non-traditional risk factors that can promote VC in patients with kidney disease. In addition, we provide an overview of the main pathogenetic mechanisms responsible for VC that may be crucial to identify new prevention strategies and possible new therapeutic approaches to reduce cardiovascular risk in patients with kidney disease.

Matrix vesicles from osteoblasts promote atherosclerotic calcification

Atherosclerotic calcification often coincides with osteoporosis, suggesting a potential interplay between bone and vascular mineralization. Osteoblast-derived matrix vesicles (Ost-MVs), pivotal in bone mineralization, have emerged as potential contributors to ectopic vascular calcification. However, the precise role of Ost-MVs in vascular calcification and the underlying mechanisms remain elusive. In this study, we observed a concomitant increase in atherosclerotic calcification and bone loss, accompanied by elevated release of Ost-MVs into circulation. We demonstrate that circulating Ost-MVs target plaque lesions in the setting of atherosclerosis. Mechanistically, vascular injury facilitates transendothelial transport of Ost-MVs, collagen І remodeling promotes Ost-MVs aggregation, and vascular smooth muscle cell (VSMC) phenotypic switching enhances MV uptake. These pathological changes during atherosclerosis collectively contribute to Ost-MVs recruitment into the vasculature. Furthermore, Ost-MVs and VSMC-derived matrix vesicles (VSMC-MVs) exacerbate calcification via the Ras-Raf-ERK pathway. Our findings unveil a novel Ost-MVs-mediated mechanism participating in vascular calcification and enriching our understanding of bone-vascular crosstalk.

Dedifferentiation- and aging-induced loss of mechanical contractility and polarity in vascular smooth muscle cells: Heterogeneous changes in macroscopic and microscopic behavior of cells in serial passage culture

Dedifferentiation and aging of vascular smooth muscle cells (VSMCs) are associated with serious vascular diseases, such as arteriosclerosis and aneurysm. However, how cell dedifferentiation and aging affect cellular mechanical behaviors at the single-cell and intracellular structure levels remains unclear. An in-depth understanding of these interactions is extremely important for understanding the mechanism underlying VSMC mechanical integrity and homeostatic regulation of vascular walls. Herein, we systematically investigated changes in VSMC morphology, structure, contractility, and motility during dedifferentiation and aging induced by serial passage culture using traction force microscopy with elastic micropillar substrates, laser nanodissection of cytoskeletons, confocal fluorescence microscopy, and atomic force microscopy. We found that VSMC dedifferentiation started in the middle stage of serial passage culture, accompanied by a transient cell spreading in the cell width and decrease in contractile protein expression. Dedifferentiated VSMCs showed a significant decrease in the contraction and stiffness of individual actin stress fibers; however, their overall cell traction forces were maintained. Simultaneously, a significant increase in cell motility and the number of actin fibers was observed in dedifferentiated VSMCs, which may be associated with the enhancement of cell migration and disruption of cell/tissue integrity during the early stage of vascular diseases. As cell senescence progressed in the later stage of serial passage culture, VSMCs displayed reduced cell spreading and migration with decrease in the overall cell traction forces and drastic reduction in mechanical polarity of cell structures and forces. These results suggested that cell senescence causes loss of mechanical contractility and polarity in VSMCs, which may be an important factor in vascular disease progression. The experimental systems established in this study can be powerful tools for understanding the mechanisms underlying cellular dedifferentiation and aging from a biomechanical perspective.

Gla Rich Protein (GRP) Mediates Vascular Smooth Muscle Cell (VSMC) Osteogenic Differentiation, Extracellular Vesicle (EV) Calcification Propensity, and Immunomodulatory Properties

Vascular calcification (VC) is a complex process involving vascular smooth muscle cell (VSMC) osteogenic differentiation, inflammation, and extracellular vesicle (EV) calcification and communication networks. Gla rich protein (GRP) is a calcification inhibitor involved in most of these processes. However, the molecular mechanism of GRP in VC and the specific characteristics, cargo, and functionality of calcifying EVs require further elucidation. Here, we use a combination of human ex vivo aortic fragments and primary vascular smooth muscle cell (VSMC) models to obtain new information on GRP function in VC and EVs released by VSMCs. We demonstrate that GRP inhibits VSMC osteogenic differentiation through downregulation of bone-related proteins and upregulation of mineralization inhibitors, with decreased mineral crystallinity in EVs deposited into the tissue extracellular matrix (ECM). EVs isolated by ultracentrifugation at 30K and 100K from the cell media (CM) and deposited in the ECM from control (CTR) and mineralizing (MM) VSMCs were biochemically, physically, and proteomically characterized. Four different EV populations were identified with shared markers commonly present in all EVs but with unique protein cargo and specific molecular profiles. Comparative proteomics identified several regulated proteins specifically loaded into MM EV populations associated with multiple processes involved in VC. Functional analysis demonstrated that 30K and 100K ECM-MM EVs with higher calcium and lower GRP levels induced macrophage inflammation. Our findings reinforce the functional relevance of GRP in multiple VC processes and suggest that ECM EVs released under calcification stress function as a new signaling axis on the calcification-inflammation cycle.

Pathophysiology and clinical implications of coronary artery calcifications

PURPOSE OF REVIEW

To provide a summary of current understanding of coronary artery calcifications (CACs), outlining the role of calcium in atherosclerosis to comprehend the clinical implications of CAC.

RECENT FINDINGS

CAC serves as a reliable indicator of coronary artery disease (CAD) and it is associated with cardiovascular events. In recognition of its significance, recent global guidelines have integrated CAC assessment into risk evaluation protocols, highlighting its role as a noninvasive tool for evaluating and stratifying patients' risk for cardiovascular events. Beyond the amount of CAC values, also, calcium morphology had been linked to cardiovascular events.By leveraging CAC assessment, healthcare providers can effectively up or down reclassify patients' risk and tailor preventive strategies accordingly. This comprehensive approach may involve lifestyle modifications, meticulous management of risk factors, and judicious use of preventive medications to mitigate the likelihood of future cardiovascular events, or withhold treatments in those without signs of CAC, to optimize resource use.

SUMMARY

The identification of CAC burden and morphology through noninvasive imaging modalities can reclassify the prediction of future cardiovascular risk and serve as a risk modifier for atherosclerosis. These data underscore the utility of selectively using CAC assessment in both primary and secondary prevention strategies for atherosclerotic cardiovascular disease.

Direct and cell-mediated EV-ECM interplay

Extracellular vesicles (EV) are a heterogeneous group of lipid particles excreted by cells. They play an important role in regeneration, development, inflammation, and cancer progression, together with the extracellular matrix (ECM), which they constantly interact with. In this review, we discuss direct and indirect interactions of EVs and the ECM and their impact on different physiological processes. The ECM affects the secretion of EVs, and the properties of the ECM and EVs modulate EVs' diffusion and adhesion. On the other hand, EVs can affect the ECM both directly through enzymes and indirectly through the modulation of the ECM synthesis and remodeling by cells. This review emphasizes recently discovered types of EVs bound to the ECM and isolated by enzymatic digestion, including matrix-bound nanovesicles (MBV) and tissue-derived EV (TiEV). In addition to the experimental studies, computer models of the EV-ECM-cell interactions, from all-atom models to quantitative pharmacology models aiming to improve our understanding of the interaction mechanisms, are also considered. STATEMENT OF SIGNIFICANCE: Application of extracellular vesicles in tissue engineering is an actively developing area. Vesicles not only affect cells themselves but also interact with the matrix and change it. The matrix also influences both cells and vesicles. In this review, different possible types of interactions between vesicles, matrix, and cells are discussed. Furthermore, the united EV-ECM system and its regulation through the cellular activity are presented.

A nontoxic strontium nanoparticle that holds the potential to act upon osteocompetent cells: An in vitro and in vivo characterization

Estrogen deficiency, long-term immobilization, and/or aging are commonly related to bone mass loss, thus increasing the risk of fractures. One option for bone replacement in injuries caused by either traumas or pathologies is the use of orthopedic cement based on polymethylmethacrylate (PMMA). Nevertheless, its reduced bioactivity may induce long-term detachment from the host tissue, resulting in the failure of the implant. In view of this problem, we developed an alternative PMMA-based porous cement (pPMMA) that favors cell invasion and improves osteointegration with better biocompatibility. The cement composition was changed by adding bioactive strontium-nanoparticles that mimic the structure of bone apatite. The nanoparticles were characterized regarding their physical-chemical properties, and their effects on osteoblasts and osteoclast cultures were assessed. Initial in vivo tests were also performed using 16 New Zealand rabbits as animal models, in which the pPMMA-cement containing the strontium nanoparticles were implanted. We showed that the apatite nanoparticles in which 90% of Ca2+ ions were substituted by Sr2+ (NanoSr 90%) upregulated TNAP activity and increased matrix mineralization. Moreover, at the molecular level, NanoSr 90% upregulated the mRNA expression levels of, Sp7, and OCN. Runx2 was increased at both mRNA and protein levels. In parallel, in vivo tests revealed that pPMMA-cement containing NanoSr 90%, upregulated two markers of bone maturation, OCN and BMP2, as well as the formation of apatite minerals after implantation in the femur of rabbits. The overall data support that strontium nanoparticles hold the potential to up-regulate mineralization in osteoblasts when associated with synthetic biomaterials.

Vascular Calcification Is Accelerated by Hyponatremia and Low Osmolality

BACKGROUND

Hyponatremia, frequently observed in patients with chronic kidney disease, is associated with increased cardiovascular morbidity and mortality. Hyponatremia or low osmolality induces oxidative stress and cell death, both of which accelerate vascular calcification (VC), a critical phenotype in patients with chronic kidney disease. Whether hyponatremia or low osmolality plays a role in the pathogenesis of VC is unknown.

METHODS

Human vascular smooth muscle cells (VSMCs) and mouse aortic rings were cultured in various osmotic conditions and calcifying medium supplemented with high calcium and phosphate. The effects of low osmolality on phenotypic change and oxidative stress in the cultured VSMCs were examined. Microarray analysis was conducted to determine the main signaling pathway of osmolality-related VC. The transcellular sodium and calcium ions flux across the VSMCs were visualized by live imaging. Furthermore, the effect of osmolality on calciprotein particles (CPPs) was investigated. Associations between arterial intimal calcification and hyponatremia or low osmolality were examined by a cross-sectional study using human autopsy specimens obtained in the Hisayama Study.

RESULTS

Low osmolality exacerbated calcification of the ECM (extracellular matrix) of cultured VSMCs and mouse aortic rings. Oxidative stress and osteogenic differentiation of VSMCs were identified as the underlying mechanisms responsible for low osmolality-induced VC. Microarray analysis showed that low osmolality activated the Rac1 (Ras-related C3 botulinum toxin substrate 1)-Akt (protein kinase B) pathway and reduced NCX1 (Na-Ca exchanger 1) expression. Live imaging showed synchronic calcium ion efflux and sodium ion influx via NCX1 when extracellular sodium ion concentrations were increased. An NCX1 inhibitor promoted calcifying media-induced VC by reducing calcium ion efflux. Furthermore, low osmolality accelerated the generation and maturation steps of CPPs. The cross-sectional study of human autopsy specimens showed that hyponatremia and low osmolality were associated with a greater area of arterial intimal calcification.

CONCLUSIONS

Hyponatremia and low osmolality promote VC through multiple cellular processes, including the Rac1-Akt pathway activation.

Extracellular Vesicles as Mediators in Atherosclerotic Cardiovascular Disease

Atherosclerosis is a chronic inflammatory disease of the arterial intima, characterized by accumulation of lipoproteins and accompanying inflammation, leading to the formation of plaques that eventually trigger occlusive thrombotic events, such as myocardial infarction and ischemic stroke. Although many aspects of plaque development have been elucidated, the role of extracellular vesicles (EVs), which are lipid bilayer-delimited vesicles released by cells as mediators of intercellular communication, has only recently come into focus of atherosclerosis research. EVs comprise several subtypes that may be differentiated by their size, mode of biogenesis, or surface marker expression and cargo. The functional effects of EVs in atherosclerosis depend on their cellular origin and the specific pathophysiological context. EVs have been suggested to play a role in all stages of plaque formation. In this review, we highlight the known mechanisms by which EVs modulate atherogenesis and outline current limitations and challenges in the field.

Yin-Yang: two sides of extracellular vesicles in inflammatory diseases

The concept of Yin-Yang, originating in ancient Chinese philosophy, symbolizes two opposing but complementary forces or principles found in all aspects of life. This concept can be quite fitting in the context of extracellular vehicles (EVs) and inflammatory diseases. Over the past decades, numerous studies have revealed that EVs can exhibit dual sides, acting as both pro- and anti-inflammatory agents, akin to the concept of Yin-Yang theory (i.e., two sides of a coin). This has enabled EVs to serve as potential indicators of pathogenesis or be manipulated for therapeutic purposes by influencing immune and inflammatory pathways. This review delves into the recent advances in understanding the Yin-Yang sides of EVs and their regulation in specific inflammatory diseases. We shed light on the current prospects of engineering EVs for treating inflammatory conditions. The Yin-Yang principle of EVs bestows upon them great potential as, therapeutic, and preventive agents for inflammatory diseases.

Unraveling the role of carboxylate groups and elastin particle size in medial calcification

While it is known that calcium phosphate (CaP) minerals deposit in elastin-rich medial layers of arteries during medial calcification, their nucleation and growth sites are still debated. Neutral carbonyl groups and carboxylate groups are possible candidates. Also, while it is known that elastin degradation leads to calcification, it is unclear whether this is due to formation of new carboxylate groups or elastin fragmentation. In this work, we disentangle effects of carboxylate groups and particle size on elastin calcification; in doing so, we shed light on CaP mineralization sites on elastin. We find carboxylate groups accelerate calcification only in early stages; they mainly function as Ca2+ ion chelation sites but not calcification sites. Their presence promotes formation (likely on Ca2+ ions adsorbed on nearby carbonyl groups) of CaP minerals with high calcium-to-phosphate ratio as intermediate phases. Larger elastin particles calcify slower but reach similar amounts of CaP minerals in late stages; they promote direct formation of hydroxyapatite and CaP minerals with low calcium-to-phosphate ratio as intermediate phases. This work provides new perspectives on how carboxylate groups and elastin particle size influence calcification; these parameters can be tuned to study the mechanism of medial calcification and design drugs to inhibit the process.

Mitochondrial Dysfunction: A Roadmap for Understanding and Tackling Cardiovascular Aging

Cardiovascular aging is a progressive remodeling process constituting a variety of cellular and molecular alterations that are closely linked to mitochondrial dysfunction. Therefore, gaining a deeper understanding of the changes in mitochondrial function during cardiovascular aging is crucial for preventing cardiovascular diseases. Cardiac aging is accompanied by fibrosis, cardiomyocyte hypertrophy, metabolic changes, and infiltration of immune cells, collectively contributing to the overall remodeling of the heart. Similarly, during vascular aging, there is a profound remodeling of blood vessel structure. These remodeling present damage to endothelial cells, increased vascular stiffness, impaired formation of new blood vessels (angiogenesis), the development of arteriosclerosis, and chronic vascular inflammation. This review underscores the role of mitochondrial dysfunction in cardiac aging, exploring its impact on fibrosis and myocardial alterations, metabolic remodeling, immune response remodeling, as well as in vascular aging in the heart. Additionally, we emphasize the significance of mitochondria-targeted therapies in preventing cardiovascular diseases in the elderly.

The interplay of collagen, macrophages, and microcalcification in atherosclerotic plaque cap rupture mechanics

The rupture of an atherosclerotic plaque cap overlying a lipid pool and/or necrotic core can lead to thrombotic cardiovascular events. In essence, the rupture of the plaque cap is a mechanical event, which occurs when the local stress exceeds the local tissue strength. However, due to inter- and intra-cap heterogeneity, the resulting ultimate cap strength varies, causing proper assessment of the plaque at risk of rupture to be lacking. Important players involved in tissue strength include the load-bearing collagenous matrix, macrophages, as major promoters of extracellular matrix degradation, and microcalcifications, deposits that can exacerbate local stress, increasing tissue propensity for rupture. This review summarizes the role of these components individually in tissue mechanics, along with the interplay between them. We argue that to be able to improve risk assessment, a better understanding of the effect of these individual components, as well as their reciprocal relationships on cap mechanics, is required. Finally, we discuss potential future steps, including a holistic multidisciplinary approach, multifactorial 3D in vitro model systems, and advancements in imaging techniques. The obtained knowledge will ultimately serve as input to help diagnose, prevent, and treat atherosclerotic cap rupture.

Phosphate in Cardiovascular Disease: From New Insights Into Molecular Mechanisms to Clinical Implications

Hyperphosphatemia is a common feature in patients with impaired kidney function and is associated with increased risk of cardiovascular disease. This phenomenon extends to the general population, whereby elevations of serum phosphate within the normal range increase risk; however, the mechanism by which this occurs is multifaceted, and many aspects are poorly understood. Less than 1% of total body phosphate is found in the circulation and extracellular space, and its regulation involves multiple organ cross talk and hormones to coordinate absorption from the small intestine and excretion by the kidneys. For phosphate to be regulated, it must be sensed. While mostly enigmatic, various phosphate sensors have been elucidated in recent years. Phosphate in the circulation can be buffered, either through regulated exchange between extracellular and cellular spaces or through chelation by circulating proteins (ie, fetuin-A) to form calciprotein particles, which in themselves serve a function for bulk mineral transport and signaling. Either through direct signaling or through mediators like hormones, calciprotein particles, or calcifying extracellular vesicles, phosphate can induce various cardiovascular disease pathologies: most notably, ectopic cardiovascular calcification but also left ventricular hypertrophy, as well as bone and kidney diseases, which then propagate phosphate dysregulation further. Therapies targeting phosphate have mostly focused on intestinal binding, of which appreciation and understanding of paracellular transport has greatly advanced the field. However, pharmacotherapies that target cardiovascular consequences of phosphate directly, such as vascular calcification, are still an area of great unmet medical need.

Two-step regulation by matrix Gla protein in brown adipose cell differentiation

OBJECTIVE

Bone morphogenetic protein (BMP) signaling is intricately involved in adipose tissue development. BMP7 together with BMP4 have been implicated in brown adipocyte differentiation but their roles during development remains poorly specified. Matrix Gla protein (MGP) inhibits BMP4 and BMP7 and is expressed in endothelial and progenitor cells. The objective was to determine the role of MGP in brown adipose tissue (BAT) development.

METHODS

The approach included global and cell-specific Mgp gene deletion in combination with RNA analysis, immunostaining, thermogenic activity, and in vitro studies.

RESULTS

The results revealed that MGP directs brown adipogenesis at two essential steps. Endothelial-derived MGP limits triggering of white adipogenic differentiation in the perivascular region, whereas MGP derived from adipose cells supports the transition of CD142-expressing progenitor cells to brown adipogenic maturity. Both steps were important to optimize the thermogenic function of BAT. Furthermore, MGP derived from both sources impacted vascular growth. Reduction of MGP in either endothelial or adipose cells expanded the endothelial cell population, suggesting that MGP is a factor in overall plasticity of adipose tissue.

CONCLUSION

MGP displays a dual and cell-specific function in BAT, essentially creating a "cellular shuttle" that coordinates brown adipogenic differentiation with vascular growth during development.

The functional role of cellular senescence during vascular calcification in chronic kidney disease

Vascular calcification (VC) has emerged as a key predictor of cardiovascular events in patients with chronic kidney disease (CKD). In recent years, an expanding body of research has put forth the concept of accelerated vascular aging among CKD patients, highlighting the significance of vascular cells senescence in the process of VC. Within the milieu of uremia, senescent vascular endothelial cells (VECs) release extracellular microvesicles (MV) that promote vascular smooth muscle cells (VSMCs) senescence, thereby triggering the subsequent osteogenic phenotypic switch and ultimately contributing to the VC process. In addition, senescent vascular progenitor or stem cells with diminished ability to differentiate into VECs and VSMCS, compromise the repair of vascular integrity, on the other hand, release a cascade of molecules associated with senescence, collectively known as the senescence-associated secretory phenotype (SASP), perpetuating the senescence phenomenon. Furthermore, SASP triggers the recruitment of monocytes and macrophages, as well as adjacent VECs and VSMCs into a pro-adhesive and pro-inflammatory senescent state. This pro-inflammatory microenvironment niche not only impacts the functionality of immune cells but also influences the differentiation of myeloid immune cells, thereby amplifying the reduced ability to effectively clear senescent cells of senescent macrophages, promoted calcification of VSMCs. The objective of this paper is to provide a comprehensive review of the contribution of vascular cell senescence to the emergence and advancement of VC. Gaining a comprehensive understanding of the involvement of cellular senescence within the vessel wall is pivotal, especially when it comes to its intersection with VC. This knowledge is essential for advancing groundbreaking anti-aging therapies, aiming to effectively mitigate cardiovascular diseases.

A new perspective on intervertebral disc calcification-from bench to bedside

Disc degeneration primarily contributes to chronic low back and neck pain. Consequently, there is an urgent need to understand the spectrum of disc degeneration phenotypes such as fibrosis, ectopic calcification, herniation, or mixed phenotypes. Amongst these phenotypes, disc calcification is the least studied. Ectopic calcification, by definition, is the pathological mineralization of soft tissues, widely studied in the context of conditions that afflict vasculature, skin, and cartilage. Clinically, disc calcification is associated with poor surgical outcomes and back pain refractory to conservative treatment. It is frequently seen as a consequence of disc aging and progressive degeneration but exhibits unique molecular and morphological characteristics: hypertrophic chondrocyte-like cell differentiation; TNAP, ENPP1, and ANK upregulation; cell death; altered Pi and PPi homeostasis; and local inflammation. Recent studies in mouse models have provided a better understanding of the mechanisms underlying this phenotype. It is essential to recognize that the presentation and nature of mineralization differ between AF, NP, and EP compartments. Moreover, the combination of anatomic location, genetics, and environmental stressors, such as aging or trauma, govern the predisposition to calcification. Lastly, the systemic regulation of calcium and Pi metabolism is less important than the local activity of PPi modulated by the ANK-ENPP1 axis, along with disc cell death and differentiation status. While there is limited understanding of this phenotype, understanding the molecular pathways governing local intervertebral disc calcification may lead to developing disease-modifying drugs and better clinical management of degeneration-related pathologies.

Do Media Extracellular Vesicles and Extracellular Vesicles Bound to the Extracellular Matrix Represent Distinct Types of Vesicles?

Mineralization-competent cells, including hypertrophic chondrocytes, mature osteoblasts, and osteogenic-differentiated smooth muscle cells secrete media extracellular vesicles (media vesicles) and extracellular vesicles bound to the extracellular matrix (matrix vesicles). Media vesicles are purified directly from the extracellular medium. On the other hand, matrix vesicles are purified after discarding the extracellular medium and subjecting the cells embedded in the extracellular matrix or bone or cartilage tissues to an enzymatic treatment. Several pieces of experimental evidence indicated that matrix vesicles and media vesicles isolated from the same types of mineralizing cells have distinct lipid and protein composition as well as functions. These findings support the view that matrix vesicles and media vesicles released by mineralizing cells have different functions in mineralized tissues due to their location, which is anchored to the extracellular matrix versus free-floating.

Extracellular Vesicles in Atherosclerosis: State of the Art

Atherosclerosis is a chronic inflammatory disease driven by lipid accumulation in the arteries, leading to narrowing and thrombosis that causes mortality. Emerging evidence has confirmed that atherosclerosis affects younger people and is involved in the majority of deaths worldwide. EVs are associated with critical steps in atherosclerosis, cholesterol metabolism, immune response, endothelial dysfunction, vascular inflammation, and remodeling. Endothelial cell-derived EVs can interact with platelets and monocytes, thereby influencing endothelial dysfunction, atherosclerotic plaque destabilization, and the formation of thrombus. EVs are potential diagnostic and prognostic biomarkers in atherosclerosis (AS) and cardiovascular disease (CVD). Importantly, EVs derived from stem/progenitor cells are essential mediators of cardiogenesis and cardioprotection and may be used in regenerative medicine and tissue engineering.

Vascular calcification: from the perspective of crosstalk

Vascular calcification (VC) is highly correlated with cardiovascular disease morbidity and mortality, but anti-VC treatment remains an area to be tackled due to the ill-defined molecular mechanisms. Regardless of the type of VC, it does not depend on a single cell but involves multi-cells/organs to form a complex cellular communication network through the vascular microenvironment to participate in the occurrence and development of VC. Therefore, focusing only on the direct effect of pathological factors on vascular smooth muscle cells (VSMCs) tends to overlook the combined effect of other cells and VSMCs, including VSMCs-VSMCs, ECs-VMSCs, Macrophages-VSMCs, etc. Extracellular vesicles (EVs) are a collective term for tiny vesicles with a membrane structure that are actively secreted by cells, and almost all cells secrete EVs. EVs docked on the surface of receptor cells can directly mediate signal transduction or transfer their contents into the cell to elicit a functional response from the receptor cells. They have been proven to participate in the VC process and have also shown attractive therapeutic prospects. Based on the advantages of EVs and the ability to be detected in body fluids, they may become a novel therapeutic agent, drug delivery vehicle, diagnostic and prognostic biomarker, and potential therapeutic target in the future. This review focuses on the new insight into VC molecular mechanisms from the perspective of crosstalk, summarizes how multi-cells/organs interactions communicate via EVs to regulate VC and the emerging potential of EVs as therapeutic methods in VC. We also summarize preclinical experiments on crosstalk-based and the current state of clinical studies on VC-related measures.

AnnexinA6: a potential therapeutic target gene for extracellular matrix mineralization

The mineralization of the extracellular matrix (ECM) is an essential and crucial process for physiological bone formation and pathological calcification. The abnormal function of ECM mineralization contributes to the worldwide risk of developing mineralization-related diseases; for instance, vascular calcification is attributed to the hyperfunction of ECM mineralization, while osteoporosis is due to hypofunction. AnnexinA6 (AnxA6), a Ca2+-dependent phospholipid-binding protein, has been extensively reported as an essential target in mineralization-related diseases such as osteoporosis, osteoarthritis, atherosclerosis, osteosarcoma, and calcific aortic valve disease. To date, AnxA6, as the largest member of the Annexin family, has attracted much attention due to its significant contribution to matrix vesicles (MVs) production and release, MVs-ECM interaction, cytoplasmic Ca2+ influx, and maturation of hydroxyapatite, making it an essential target in ECM mineralization. In this review, we outlined the recent advancements in the role of AnxA6 in mineralization-related diseases and the potential mechanisms of AnxA6 under normal and mineralization-related pathological conditions. AnxA6 could promote ECM mineralization for bone regeneration in the manner described previously. Therefore, AnxA6 may be a potential osteogenic target for ECM mineralization.

Multiomics of Tissue Extracellular Vesicles Identifies Unique Modulators of Atherosclerosis and Calcific Aortic Valve Stenosis

BACKGROUND

Fewer than 50% of patients who develop aortic valve calcification have concomitant atherosclerosis, implying differential pathogenesis. Although circulating extracellular vesicles (EVs) act as biomarkers of cardiovascular diseases, tissue-entrapped EVs are associated with early mineralization, but their cargoes, functions, and contributions to disease remain unknown.

METHODS

Disease stage-specific proteomics was performed on human carotid endarterectomy specimens (n=16) and stenotic aortic valves (n=18). Tissue EVs were isolated from human carotid arteries (normal, n=6; diseased, n=4) and aortic valves (normal, n=6; diseased, n=4) by enzymatic digestion, (ultra)centrifugation, and a 15-fraction density gradient validated by proteomics, CD63-immunogold electron microscopy, and nanoparticle tracking analysis. Vesiculomics, comprising vesicular proteomics and small RNA-sequencing, was conducted on tissue EVs. TargetScan identified microRNA targets. Pathway network analyses prioritized genes for validation in primary human carotid artery smooth muscle cells and aortic valvular interstitial cells.

RESULTS

Disease progression drove significant convergence (P<0.0001) of carotid artery plaque and calcified aortic valve proteomes (2318 proteins). Each tissue also retained a unique subset of differentially enriched proteins (381 in plaques; 226 in valves; q<0.05). Vesicular gene ontology terms increased 2.9-fold (P<0.0001) among proteins modulated by disease in both tissues. Proteomics identified 22 EV markers in tissue digest fractions. Networks of proteins and microRNA targets changed by disease progression in both artery and valve EVs revealed shared involvement in intracellular signaling and cell cycle regulation. Vesiculomics identified 773 proteins and 80 microRNAs differentially enriched by disease exclusively in artery or valve EVs (q<0.05); multiomics integration found tissue-specific EV cargoes associated with procalcific Notch and Wnt signaling in carotid arteries and aortic valves, respectively. Knockdown of tissue-specific EV-derived molecules FGFR2, PPP2CA, and ADAM17 in human carotid artery smooth muscle cells and WNT5A, APP, and APC in human aortic valvular interstitial cells significantly modulated calcification.

CONCLUSIONS

The first comparative proteomics study of human carotid artery plaques and calcified aortic valves identifies unique drivers of atherosclerosis versus aortic valve stenosis and implicates EVs in advanced cardiovascular calcification. We delineate a vesiculomics strategy to isolate, purify, and study protein and RNA cargoes from EVs entrapped in fibrocalcific tissues. Integration of vesicular proteomics and transcriptomics by network approaches revealed novel roles for tissue EVs in modulating cardiovascular disease.

Extracellular vesicles stimulate smooth muscle cell migration by presenting collagen VI

The extracellular matrix (ECM) supports blood vessel architecture and functionality and undergoes active remodelling during vascular repair and atherogenesis. Vascular smooth muscle cells (VSMCs) are essential for vessel repair and, via their secretome, are able to invade from the vessel media into the intima to mediate ECM remodelling. Accumulation of fibronectin (FN) is a hallmark of early vascular repair and atherosclerosis and here we show that FN stimulates VSMCs to secrete small extracellular vesicles (sEVs) by activating the β1 integrin/FAK/Src pathway as well as Arp2/3-dependent branching of the actin cytoskeleton. Spatially, sEV were secreted via filopodia-like cellular protrusions at the leading edge of migrating cells. We found that sEVs are trapped by the ECM in vitro and colocalise with FN in symptomatic atherosclerotic plaques in vivo. Functionally, ECM-trapped sEVs induced the formation of focal adhesions (FA) with enhanced pulling forces at the cellular periphery. Proteomic and GO pathway analysis revealed that VSMC-derived sEVs display a cell adhesion signature and are specifically enriched with collagen VI. In vitro assays identified collagen VI as playing the key role in cell adhesion and invasion. Taken together our data suggests that the accumulation of FN is a key early event in vessel repair acting to promote secretion of collage VI enriched sEVs by VSMCs. These sEVs stimulate migration and invasion by triggering peripheral focal adhesion formation and actomyosin contraction to exert sufficient traction forces to enable VSMC movement within the complex vascular ECM network.

Macrophage death in atherosclerosis: potential role in calcification

Cell death is an important aspect of atherosclerotic plaque development. Insufficient efferocytosis of death cells by phagocytic macrophages leads to the buildup of a necrotic core that impacts stability of the plaque. Furthermore, in the presence of calcium and phosphate, apoptotic bodies resulting from death cells can act as nucleation sites for the formation of calcium phosphate crystals, mostly in the form of hydroxyapatite, which leads to calcification of the atherosclerotic plaque, further impacting plaque stability. Excessive uptake of cholesterol-loaded oxidized LDL particles by macrophages present in atherosclerotic plaques leads to foam cell formation, which not only reduces their efferocytosis capacity, but also can induce apoptosis in these cells. The resulting apoptotic bodies can contribute to calcification of the atherosclerotic plaque. Moreover, other forms of macrophage cell death, such as pyroptosis, necroptosis, parthanatos, and ferroptosis can also contribute by similar mechanisms to plaque calcification. This review focuses on macrophage death in atherosclerosis, and its potential role in calcification. Reducing macrophage cell death and/or increasing their efferocytosis capacity could be a novel therapeutic strategy to reduce the formation of a necrotic core and calcification and thereby improving atherosclerotic plaque stability.

EphrinB2 drives osteogenic fate of adult cardiac fibroblasts in a calcium influx dependent manner

Cardiac calcification is a crucial but underrecognized pathological process, greatly increasing the risk of cardiovascular diseases. Little is known about how cardiac fibroblasts, as a central mediator, facilitate abnormal mineralization. Erythropoietin-producing hepatoma interactor B2 (EphrinB2), previously identified as an angiogenic regulator, is involved in fibroblast activation, while its role in the osteogenic differentiation of cardiac fibroblasts is unknown. Bioinformatics analysis was conducted to characterize the expression of the Ephrin family in human calcified aortic valves and calcific mouse hearts. The effects of EphrinB2 on cardiac fibroblasts to adopt osteogenic fate was determined by gain- and loss-of-function. EphrinB2 mRNA level was downregulated in calcified aortic valves and mouse hearts. Knockdown of EphrinB2 attenuated mineral deposits in adult cardiac fibroblasts, whereas overexpression of EphrinB2 promoted their osteogenic differentiation. RNA sequencing data implied that Ca2+-related S100/receptor for advanced glycation end products (RAGE) signaling may mediate EphrinB2-induced mineralization in cardiac fibroblasts. Moreover, L-type calcium channel blockers inhibited osteogenic differentiation of cardiac fibroblasts, implying a critical role in Ca2+ influx. In conclusion, our data illustrated an unrecognized role of EphrinB2, which functions as a novel osteogenic regulator in the heart through Ca2+ signaling and could be a potential therapeutic target in cardiovascular calcification.NEW & NOTEWORTHY In this study, we observed that adult cardiac fibroblasts but not neonatal cardiac fibroblasts exhibit the ability of osteogenic differentiation. EphrinB2 promoted osteogenic differentiation of cardiac fibroblasts through activating Ca2+-related S100/RAGE signaling. Inhibition of Ca2+ influx using L-type calcium channel blockers inhibited EphrinB2-mediated calcification of cardiac fibroblasts. Our data implied an unrecognized role of EphrinB2 in regulating cardiac calcification though Ca2+-related signaling, suggesting a potential therapeutic target of cardiovascular calcification.

Vascular calcification in CKD: New insights into its mechanisms

Vascular calcification (VC) is a common complication of chronic kidney disease (CKD) and contributes to an increased risk of cardiovascular morbidity and mortality. However, effective therapies are still unavailable at present. It has been well established that VC associated with CKD is not a passive process of calcium phosphate deposition, but an actively regulated and cell-mediated process that shares many similarities with bone formation. Additionally, numerous studies have suggested that CKD patients have specific risk factors and contributors to the development of VC, such as hyperphosphatemia, uremic toxins, oxidative stress and inflammation. Although research efforts in the past decade have greatly improved our knowledge of the multiple factors and mechanisms involved in CKD-related VC, many questions remain unanswered. Moreover, studies from the past decade have demonstrated that epigenetic modifications abnormalities, such as DNA methylation, histone modifications and noncoding RNAs, play an important role in the regulation of VC. This review seeks to provide an overview of the pathophysiological and molecular mechanisms of VC associated with CKD, mainly focusing on the involvement of epigenetic modifications in the initiation and progression of uremic VC, with the aim to develop promising therapies for CKD-related cardiovascular events in the future.

FHL5 Controls Vascular Disease-Associated Gene Programs in Smooth Muscle Cells

BACKGROUND

Genome-wide association studies have identified hundreds of loci associated with common vascular diseases, such as coronary artery disease, myocardial infarction, and hypertension. However, the lack of mechanistic insights for many GWAS loci limits their translation into the clinic. Among these loci with unknown functions is UFL1-four-and-a-half LIM (LIN-11, Isl-1, MEC-3) domain 5 (FHL5; chr6q16.1), which reached genome-wide significance in a recent coronary artery disease/ myocardial infarction GWAS meta-analysis. UFL1-FHL5 is also associated with several vascular diseases, consistent with the widespread pleiotropy observed for GWAS loci.

METHODS

We apply a multimodal approach leveraging statistical fine-mapping, epigenomic profiling, and ex vivo analysis of human coronary artery tissues to implicate FHL5 as the top candidate causal gene. We unravel the molecular mechanisms of the cross-phenotype genetic associations through in vitro functional analyses and epigenomic profiling experiments in coronary artery smooth muscle cells.

RESULTS

We prioritized FHL5 as the top candidate causal gene at the UFL1-FHL5 locus through expression quantitative trait locus colocalization methods. FHL5 gene expression was enriched in the smooth muscle cells and pericyte population in human artery tissues with coexpression network analyses supporting a functional role in regulating smooth muscle cell contraction. Unexpectedly, under procalcifying conditions, FHL5 overexpression promoted vascular calcification and dysregulated processes related to extracellular matrix organization and calcium handling. Lastly, by mapping FHL5 binding sites and inferring FHL5 target gene function using artery tissue gene regulatory network analyses, we highlight regulatory interactions between FHL5 and downstream coronary artery disease/myocardial infarction loci, such as FOXL1 and FN1 that have roles in vascular remodeling.

CONCLUSIONS

Taken together, these studies provide mechanistic insights into the pleiotropic genetic associations of UFL1-FHL5. We show that FHL5 mediates vascular disease risk through transcriptional regulation of downstream vascular remodeling gene programs. These transacting mechanisms may explain a portion of the heritable risk for complex vascular diseases.

Signaling pathways in vascular function and hypertension: molecular mechanisms and therapeutic interventions

Hypertension is a global public health issue and the leading cause of premature death in humans. Despite more than a century of research, hypertension remains difficult to cure due to its complex mechanisms involving multiple interactive factors and our limited understanding of it. Hypertension is a condition that is named after its clinical features. Vascular function is a factor that affects blood pressure directly, and it is a main strategy for clinically controlling BP to regulate constriction/relaxation function of blood vessels. Vascular elasticity, caliber, and reactivity are all characteristic indicators reflecting vascular function. Blood vessels are composed of three distinct layers, out of which the endothelial cells in intima and the smooth muscle cells in media are the main performers of vascular function. The alterations in signaling pathways in these cells are the key molecular mechanisms underlying vascular dysfunction and hypertension development. In this manuscript, we will comprehensively review the signaling pathways involved in vascular function regulation and hypertension progression, including calcium pathway, NO-NOsGC-cGMP pathway, various vascular remodeling pathways and some important upstream pathways such as renin-angiotensin-aldosterone system, oxidative stress-related signaling pathway, immunity/inflammation pathway, etc. Meanwhile, we will also summarize the treatment methods of hypertension that targets vascular function regulation and discuss the possibility of these signaling pathways being applied to clinical work.

Extracellular Vesicles as Regulators of the Extracellular Matrix

Extracellular vesicles (EVs) are small membrane-bound vesicles secreted into the extracellular space by all cell types. EVs transfer their cargo which includes nucleic acids, proteins, and lipids to facilitate cell-to-cell communication. As EVs are released and move from parent to recipient cell, EVs interact with the extracellular matrix (ECM) which acts as a physical scaffold for the organization and function of cells. Recent work has shown that EVs can modulate and act as regulators of the ECM. This review will first discuss EV biogenesis and the mechanism by which EVs are transported through the ECM. Additionally, we discuss how EVs contribute as structural components of the matrix and as components that aid in the degradation of the ECM. Lastly, the role of EVs in influencing recipient cells to remodel the ECM in both pathological and therapeutic contexts is examined.

Inhibition of Neutral Sphingomyelinase 2 by Novel Small Molecule Inhibitors Results in Decreased Release of Extracellular Vesicles by Vascular Smooth Muscle Cells and Attenuated Calcification

Vascular calcification (VC) is an important contributor and prognostic factor in the pathogenesis of cardiovascular diseases. VC is an active process mediated by the release of extracellular vesicles by vascular smooth muscle cells (VSMCs), and the enzyme neutral sphingomyelinase 2 (nSMase2 or SMPD3) plays a key role. Upon activation, the enzyme catalyzes the hydrolysis of sphingomyelin, thereby generating ceramide and phosphocholine. This conversion mediates the release of exosomes, a type of extracellular vesicles (EVs), which ultimately forms the nidus for VC. nSMase2 therefore represents a drug target, the inhibition of which is thought to prevent or halt VC progression. In search of novel druglike small molecule inhibitors of nSMase2, we have used virtual ligand screening to identify potential ligands. From an in-silico collection of 48,6844 small druglike molecules, we selected 996 compounds after application of an in-house multi-step procedure combining different filtering and docking procedures. Selected compounds were functionally tested in vitro; from this, we identified 52 individual hit molecules that inhibited nSMase2 activity by more than 20% at a concentration of 150 µM. Further analysis showed that five compounds presented with IC₅₀s lower than 2 µM. Of these, compounds ID 5728450 and ID 4011505 decreased human primary VSMC EV release and calcification in vitro. The hit molecules identified here represent new classes of nSMase2 inhibitors that may be developed into lead molecules for the therapeutic or prophylactic treatment of VC.

Extracellular Vesicles and Vascular Inflammation

Vascular inflammation is the most common pathological feature in the pathogenesis of human disease. It is a complex immune process involved with many different types of cells including platelet, monocytes, macrophages, endothelial cells, and others. It is widely accepted that both innate and adaptive immune responses are important for the initiation and progression of vascular inflammation. The cell-cell interaction constitutes an important aspect of those immune responses in the vascular inflammation. Extracellular vesicles (EVs) are nanometer-sized double-layer lipid membrane vesicles released from most types of cells. They have been proved to play critical roles in intercellular communication in the occurrence and development of multisystem diseases. With the advancement of basal medical science, the biological roles of EVs in vascular inflammation have been clearer today. In this chapter, we will summarize the advance progress of extracellular vesicles in regulating vascular inflammation and its potential application in the clinical.

The mechanosensitive Piezo1 channels contribute to the arterial medial calcification

Vascular calcification (VC) is associated with a number of cardiovascular diseases, as well as chronic kidney disease. The role of smooth muscle cells (SMC) has already been widely explored in VC, as has the role of intracellular Ca²⁺ in regulating SMC function. Increased intracellular calcium concentration ([Ca²⁺]_i) in vascular SMC has been proposed to stimulate VC. However, the contribution of the non-selective Piezo1 mechanosensitive cation channels to the elevation of [Ca²⁺]_i, and consequently to the process of VC has never been examined. In this work the essential contribution of Piezo1 channels to arterial medial calcification is demonstrated. The presence of Piezo1 was proved on human aortic smooth muscle samples using immunohistochemistry. Quantitative PCR and Western blot analysis confirmed the expression of the channel on the human aortic smooth muscle cell line (HAoSMC). Functional measurements were done on HAoSMC under control and calcifying condition. Calcification was induced by supplementing the growth medium with inorganic phosphate (1.5 mmol/L, pH 7.4) and calcium (CaCl₂, 0.6 mmol/L) for 7 days. Measurement of [Ca²⁺]_i using fluorescent Fura-2 dye upon stimulation of Piezo1 channels (either by hypoosmolarity, or Yoda1) demonstrated significantly higher calcium transients in calcified as compared to control HAoSMCs. The expression of mechanosensitive Piezo1 channel is augmented in calcified arterial SMCs leading to a higher calcium influx upon stimulation. Activation of the channel by Yoda1 (10 μmol/L) enhanced calcification of HAoSMCs, while Dooku1, which antagonizes the effect of Yoda1, reduced this amplification. Application of Dooku1 alone inhibited the calcification. Knockdown of Piezo1 by siRNA suppressed the calcification evoked by Yoda1 under calcifying conditions. Our results demonstrate the pivotal role of Piezo1 channels in arterial medial calcification.

Annexins and cardiovascular diseases: Beyond membrane trafficking and repair

Cardiovascular diseases (CVD) remain the leading cause of mortality worldwide. The main cause underlying CVD is associated with the pathological remodeling of the vascular wall, involving several cell types, including endothelial cells, vascular smooth muscle cells, and leukocytes. Vascular remodeling is often related with the development of atherosclerotic plaques leading to narrowing of the arteries and reduced blood flow. Atherosclerosis is known to be triggered by high blood cholesterol levels, which in the presence of a dysfunctional endothelium, results in the retention of lipoproteins in the artery wall, leading to an immune-inflammatory response. Continued hypercholesterolemia and inflammation aggravate the progression of atherosclerotic plaque over time, which is often complicated by thrombus development, leading to the possibility of CV events such as myocardial infarction or stroke. Annexins are a family of proteins with high structural homology that bind phospholipids in a calcium-dependent manner. These proteins are involved in several biological functions, from cell structural organization to growth regulation and vesicle trafficking. In vitro gain- or loss-of-function experiments have demonstrated the implication of annexins with a wide variety of cellular processes independent of calcium signaling such as immune-inflammatory response, cell proliferation, migration, differentiation, apoptosis, and membrane repair. In the last years, the use of mice deficient for different annexins has provided insight into additional functions of these proteins in vivo, and their involvement in different pathologies. This review will focus in the role of annexins in CVD, highlighting the mechanisms involved and the potential therapeutic effects of these proteins.

Vascular Calcification: In Vitro Models under the Magnifying Glass

Vascular calcification is a systemic disease contributing to cardiovascular morbidity and mortality. The pathophysiology of vascular calcification involves calcium salt deposition by vascular smooth muscle cells that exhibit an osteoblast-like phenotype. Multiple conditions drive the phenotypic switch and calcium deposition in the vascular wall; however, the exact molecular mechanisms and the connection between vascular smooth muscle cells and other cell types are not fully elucidated. In this hazy landscape, effective treatment options are lacking. Due to the pathophysiological complexity, several research models are available to evaluate different aspects of the calcification process. This review gives an overview of the in vitro cell models used so far to study the molecular processes underlying vascular calcification. In addition, relevant natural and synthetic compounds that exerted anticalcifying properties in in vitro systems are discussed.

Attenuating effect of magnesium on pulmonary arterial calcification in rodent models of pulmonary hypertension

OBJECTIVE

Vascular calcification has been considered as a potential therapeutic target in pulmonary hypertension. Mg2+ has a protective role against calcification. This study aimed to investigate whether Mg2+ could alleviate pulmonary hypertension by reducing medial calcification of pulmonary arteries.

METHODS

Monocrotaline (MCT)-induced and chronic hypoxia-induced pulmonary hypertension rats were given an oral administration of 10% MgSO4 (10 ml/kg per day). Additionally, we administered Mg2+ in calcified pulmonary artery smooth muscle cells (PASMCs) after incubating with β-glycerophosphate (β-GP, 10 mmol/l).

RESULTS

In vivo, MCT-induced and chronic hypoxia-induced pulmonary hypertension indexes, including right ventricular systolic pressure, right ventricular mass index, and arterial wall thickness, as well as Alizarin Red S (ARS) staining-visualized calcium deposition, high calcium levels, and osteochondrogenic differentiation in pulmonary arteries, were mitigated by dietary Mg2+ intake. In vitro, β-GP-induced calcium-rich deposits stained by ARS, calcium content, as well as the detrimental effects of calcification to proliferation, migration, and resistance to apoptosis of PASMCs were alleviated by high Mg2+ but exacerbated by low Mg2+. Expression levels of mRNA and protein of β-GP-induced osteochondrogenic markers, RUNX Family Transcription Factor 2, and Msh Homeobox 2 were decreased by high Mg2+ but increased by low Mg2+; however, Mg2+ did not affect β-GP-induced expression of SRY-Box Transcription Factor 9. Moreover, mRNA expression and protein levels of β-GP-reduced calcification inhibitor, Matrix GLA protein was increased by high Mg2+ but decreased by low Mg2+.

CONCLUSION

Mg2+ supplement is a powerful strategy to treat pulmonary hypertension by mitigating pulmonary arterial calcification as the calcification triggered physiological and pathological changes to PASMCs.

EZH2 Regulates ANXA6 Expression via H3K27me3 and Is Involved in Angiotensin II-Induced Vascular Smooth Muscle Cell Senescence

Objectives

Abdominal aortic aneurysm (AAA) has a high risk of rupture of the aorta and is one of the leading causes of death in older adults. This study is aimed at confirming the influence and mechanism of the abnormally expressed ANXA6 gene in AAA.

Methods

Clinical samples were collected for proteome sequencing to screen for differentially expressed proteins. An Ang II-induced vascular smooth muscle cell (VSMC) aging model as well as an AAA animal model was used. Using RT-qPCR to detect the mRNA levels of EZH2, ANXA6, IK-6, and IL-8 in cells and tissues were assessed. Western blotting and immunohistochemistry staining were used apply for the expression of associated proteins in cells and tissues. SA-β-gal staining, flow cytometry, and DHE staining were used to detect senescent cells and the level of ROS. The cell cycle was assessed by flow cytometry. Arterial pathology was observed by HE staining. The aging of VSMCs in arterial tissue was assessed by coimmunofluorescence for α-SMA and p53.

Results

There were 24 differentially expressed proteins in the AAA clinical samples, including 10 upregulated protein and 14 downregulated protein, and the differential expression of ANXA6 was associated with vascular disease. Our study found that ANXA6 was highly expressed and EZH2 was lowly expressed in an Ang II-induced VSMC aging model. Knockdown of ANXA6 or overexpression of EZH2 inhibited Ang II-induced ROS, inhibited cell senescence, decreased Ang II evoked G1 arrest, and increased cells in G2 phase, while overexpression of ANXA6 played the opposite role. Overexpression of EZH2 inhibited ANXA6 expression by increasing H3K27me3 modification at the ANXA6 promoter. Simultaneous overexpression of EZH2 and the protective effect of EZH2 on cell senescence were partially reversed by ANXA6. Similarly, ANXA6 was highly expressed and EZH2 was lowly expressed in an Ang II-induced AAA animal model. Knockdown of ANXA6 and overexpression of EZH2 alleviated Ang II-induced VSMC senescence and inhibited AAA progression, while simultaneous overexpression of EZH2 and ANXA6 partially reversed the protective effect of EZH2 on AAA.

Conclusion

EZH2 regulates the ANXA6 promoter H3K27me3 modification, inhibits ANXA6 expression, alleviates Ang II-induced VSMC senescence, and inhibits AAA progression.

Vascular Smooth Muscle Cell Neutral Sphingomyelinase 2 in the Release of Exosomes and Vascular Calcification

Vascular calcification (VC) is the pathological precipitation of calcium salts in the walls of blood vessels. It is a risk factor for cardiovascular events and their associated mortality. VC can be observed in a variety of cardiovascular diseases and is most prominent in diseases that are associated with dysregulated mineral homeostasis such as in chronic kidney disease. Local factors and mechanisms underlying VC are still incompletely understood, but it is appreciated that VC is a multifactorial process in which vascular smooth muscle cells (VSMCs) play an important role. VSMCs participate in VC by releasing extracellular vesicles (EVs), the extent, composition, and propensity to calcify of which depend on VSMC phenotype and microenvironment. Currently, no targeted therapy is available to treat VC. In-depth knowledge of molecular players of EV release and the understanding of their mechanisms constitute a vital foundation for the design of pharmacological treatments to combat VC effectively. This review highlights our current knowledge of VSMCs in VC and focuses on the biogenesis of exosomes and the role of the neutral Sphingomyelinase 2 (nSMase2).

Sorting through the extensive and confusing roles of sortilin in metabolic disease

Sortilin is a post-Golgi trafficking receptor homologous to the yeast vacuolar protein sorting receptor 10 (VPS10). The VPS10 motif on sortilin is a 10-bladed β-propeller structure capable of binding more than 50 proteins, covering a wide range of biological functions including lipid and lipoprotein metabolism, neuronal growth and death, inflammation, and lysosomal degradation. Sortilin has a complex cellular trafficking itinerary, where it functions as a receptor in the trans-Golgi network, endosomes, secretory vesicles, multivesicular bodies, and at the cell surface. In addition, sortilin is associated with hypercholesterolemia, Alzheimer's disease, prion diseases, Parkinson's disease, and inflammation syndromes. The 1p13.3 locus containing SORT1, the gene encoding sortilin, carries the strongest association with LDL-C of all loci in human genome-wide association studies. However, the mechanism by which sortilin influences LDL-C is unclear. Here, we review the role sortilin plays in cardiovascular and metabolic diseases and describe in detail the large and often contradictory literature on the role of sortilin in the regulation of LDL-C levels.

Induced pluripotent stem cell-derived smooth muscle cells to study cardiovascular calcification

Cardiovascular calcification is the lead predictor of cardiovascular events and the top cause of morbidity and mortality worldwide. To date, only invasive surgical options are available to treat cardiovascular calcification despite the growing understanding of underlying pathological mechanisms. Key players in vascular calcification are vascular smooth muscle cells (SMCs), which transform into calcifying SMCs and secrete mineralizing extracellular vesicles that form microcalcifications, subsequently increasing plaque instability and consequential plaque rupture. There is an increasing, practical need for a large scale and inexhaustible source of functional SMCs. Here we describe an induced pluripotent stem cell (iPSC)-derived model of SMCs by differentiating iPSCs toward SMCs to study the pathogenesis of vascular calcification. Specifically, we characterize the proteome during iPSC differentiation to better understand the cellular dynamics during this process. First, we differentiated human iPSCs toward an induced-SMC (iSMC) phenotype in a 10-day protocol. The success of iSMC differentiation was demonstrated through morphological analysis, immunofluorescent staining, flow cytometry, and proteomics characterization. Proteomics was performed throughout the entire differentiation time course to provide a robust, well-defined starting and ending cell population. Proteomics data verified iPSC differentiation to iSMCs, and functional enrichment of proteins on different days showed the key pathways changing during iSMC development. Proteomics comparison with primary human SMCs showed a high correlation with iSMCs. After iSMC differentiation, we initiated calcification in the iSMCs by culturing the cells in osteogenic media for 17 days. Calcification was verified using Alizarin Red S staining and proteomics data analysis. This study presents an inexhaustible source of functional vascular SMCs and calcifying vascular SMCs to create an in vitro model of vascular calcification in osteogenic conditions, with high potential for future applications in cardiovascular calcification research.

Low Plasma Ionized Calcium Is Associated With Increased Mortality: A Population-based Study of 106 768 Individuals

CONTEXT

Low circulating total calcium or albumin-adjusted calcium has been associated with higher mortality, especially in hospital settings; however, these measures tend to misclassify patients with derangements in calcium homeostasis.

OBJECTIVE

As the association of the biologically active ionized calcium with mortality is poorly elucidated, we tested the hypothesis that low plasma ionized calcium is associated with higher risk of all-cause and cause-specific mortality in the general population.

METHODS

We included 106 768 individuals from the Copenhagen General Population Study. Information on all-cause and cause-specific mortality was from registries and risks were calculated using Cox regression and competing-risks regression by the STATA command stcompet.

RESULTS

During a median follow-up period of 9.2 years, 11 269 individuals died. Each 0.1 mmol/L lower plasma ionized calcium below the median of 1.21 mmol/L was associated with a multivariable adjusted hazard ratio of 1.23 (95% CI, 1.10-1.38) for all-cause mortality. Corresponding hazard ratios for cancer and other mortality were 1.29 (1.06-1.57) and 1.24 (1.01-1.53), respectively. In contrast, for cardiovascular mortality, only high plasma ionized calcium was associated with mortality with a hazard ratio of 1.17 (1.02-1.35) per 0.1 mmol/L higher plasma ionized calcium above the median. We found no interactions between plasma ionized calcium and preexisting cardiovascular or renal disease on all-cause mortality.

CONCLUSION

In the general population, low plasma ionized calcium was associated with increased all-cause, cancer, and other mortality, while high levels were associated with increased cardiovascular mortality.