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

Extracellular vesicle signalling in atherosclerosis

Atherosclerosis is a major cardiovascular disease and in 2016, the World Health Organisation (WHO) estimated 17.5 million global deaths, corresponding to 31% of all global deaths, were driven by inflammation and deposition of lipids into the arterial wall. This leads to the development of plaques which narrow the vessel lumen, particularly in the coronary and carotid arteries. Atherosclerotic plaques can become unstable and rupture, leading to myocardial infarction or stroke. Extracellular vesicles (EVs) are a heterogeneous population of vesicles secreted from cells with a wide range of biological functions. EVs participate in cell-cell communication and signalling via transport of cargo including enzymes, DNA, RNA and microRNA in both physiological and patholophysiological settings. EVs are present in atherosclerotic plaques and have been implicated in cellular signalling processes in atherosclerosis development, including immune responses, inflammation, cell proliferation and migration, cell death and vascular remodeling during progression of the disease. In this review, we summarise the current knowledge regarding EV signalling in atherosclerosis progression and the potential of utilising EV signatures as biomarkers of disease.

Avian eggshell formation reveals a new paradigm for vertebrate mineralization via vesicular amorphous calcium carbonate

Amorphous calcium carbonate (ACC) is an unstable mineral phase, which is progressively transformed into aragonite or calcite in biomineralization of marine invertebrate shells or avian eggshells, respectively. We have previously proposed a model of vesicular transport to provide stabilized ACC in chicken uterine fluid where eggshell mineralization takes place. Herein, we report further experimental support for this model. We confirmed the presence of extracellular vesicles (EVs) using transmission EM and showed high levels of mRNA of vesicular markers in the oviduct segments where eggshell mineralization occurs. We also demonstrate that EVs contain ACC in uterine fluid using spectroscopic analysis. Moreover, proteomics and immunofluorescence confirmed the presence of major vesicular, mineralization-specific and eggshell matrix proteins in the uterus and in purified EVs. We propose a comprehensive role for EVs in eggshell mineralization, in which annexins transfer calcium into vesicles and carbonic anhydrase 4 catalyzes the formation of bicarbonate ions (HCO[Formula: see text]), for accumulation of ACC in vesicles. We hypothesize that ACC is stabilized by ovalbumin and/or lysozyme or additional vesicle proteins identified in this study. Finally, EDIL3 and MFGE8 are proposed to serve as guidance molecules to target EVs to the mineralization site. We therefore report for the first-time experimental evidence for the components of vesicular transport to supply ACC in a vertebrate model of biomineralization.

Poly(ADP-Ribose) Links the DNA Damage Response and Biomineralization

Biomineralization of the extracellular matrix is an essential, regulated process. Inappropriate mineralization of bone and the vasculature has devastating effects on patient health, yet an integrated understanding of the chemical and cell biological processes that lead to mineral nucleation remains elusive. Here, we report that biomineralization of bone and the vasculature is associated with extracellular poly(ADP-ribose) synthesized by poly(ADP-ribose) polymerases in response to oxidative and/or DNA damage. We use ultrastructural methods to show poly(ADP-ribose) can form both calcified spherical particles, reminiscent of those found in vascular calcification, and biomimetically calcified collagen fibrils similar to bone. Importantly, inhibition of poly(ADP-ribose) biosynthesis in vitro and in vivo inhibits biomineralization, suggesting a therapeutic route for the treatment of vascular calcifications. We conclude that poly(ADP-ribose) plays a central chemical role in both pathological and physiological extracellular matrix calcification.

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Poly(ADP-ribose) is found close to ECM calcification in developing bone and arteries

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Poly(ADP-ribose) is produced in response to oxidative stress and delivered to the ECM

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Poly(ADP-ribose) forms dense liquid droplets with calcium ions

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Inhibiting PARP enzyme activity blocks calcification in vitro and in vivo

PET/MRI of atherosclerosis

Myocardial infarction and stroke are the most prevalent global causes of death. Each year 15 million people worldwide die due to myocardial infarction or stroke. Rupture of a vulnerable atherosclerotic plaque is the main underlying cause of stroke and myocardial infarction. Key features of a vulnerable plaque are inflammation, a large lipid-rich necrotic core (LRNC) with a thin or ruptured overlying fibrous cap, and intraplaque hemorrhage (IPH). Noninvasive imaging of these features could have a role in risk stratification of myocardial infarction and stroke and can potentially be utilized for treatment guidance and monitoring. The recent development of hybrid PET/MRI combining the superior soft tissue contrast of MRI with the opportunity to visualize specific plaque features using various radioactive tracers, paves the way for comprehensive plaque imaging. In this review, the use of hybrid PET/MRI for atherosclerotic plaque imaging in carotid and coronary arteries is discussed. The pros and cons of different hybrid PET/MRI systems are reviewed. The challenges in the development of PET/MRI and potential solutions are described. An overview of PET and MRI acquisition techniques for imaging of atherosclerosis including motion correction is provided, followed by a summary of vessel wall imaging PET/MRI studies in patients with carotid and coronary artery disease. Finally, the future of imaging of atherosclerosis with PET/MRI is discussed.

Extracellular Vesicles as Delivery Vehicles of Specific Cellular Cargo

Extracellular vesicles (EVs) mediate cell-to-cell communication via the transfer of biomolecules locally and systemically between organs. It has been elucidated that the specific EV cargo load is fundamental for cellular response upon EV delivery. Therefore, revealing the specific molecular machinery that functionally regulates the precise EV cargo intracellularly is of importance in understanding the role of EVs in physiology and pathophysiology and conveying therapeutic use. The purpose of this review is to summarize recent findings on the general rules, as well as specific modulator motifs governing EV cargo loading. Finally, we address available information on potential therapeutic strategies to alter cargo loading.

Reactive Oxygen-Forming Nox5 Links Vascular Smooth Muscle Cell Phenotypic Switching and Extracellular Vesicle-Mediated Vascular Calcification

RATIONALE

Vascular calcification, the formation of calcium phosphate crystals in the vessel wall, is mediated by vascular smooth muscle cells (VSMCs). However, the underlying molecular mechanisms remain elusive, precluding mechanism-based therapies.

OBJECTIVE

Phenotypic switching denotes a loss of contractile proteins and an increase in migration and proliferation, whereby VSMCs are termed synthetic. We examined how VSMC phenotypic switching influences vascular calcification and the possible role of the uniquely calcium-dependent reactive oxygen species (ROS)-forming Nox5 (NADPH oxidase 5).

METHODS AND RESULTS

In vitro cultures of synthetic VSMCs showed decreased expression of contractile markers CNN-1 (calponin 1), α-SMA (α-smooth muscle actin), and SM22-α (smooth muscle protein 22α) and an increase in synthetic marker S100A4 (S100 calcium binding protein A4) compared with contractile VSMCs. This was associated with increased calcification of synthetic cells in response to high extracellular Ca²⁺. Phenotypic switching was accompanied by increased levels of ROS and Ca²⁺-dependent Nox5 in synthetic VSMCs. Nox5 itself regulated VSMC phenotype as siRNA knockdown of Nox5 increased contractile marker expression and decreased calcification, while overexpression of Nox5 decreased contractile marker expression. ROS production in synthetic VSMCs was cytosolic Ca²⁺-dependent, in line with it being mediated by Nox5. Treatment of VSMCs with Ca²⁺ loaded extracellular vesicles (EVs) lead to an increase in cytosolic Ca²⁺. Inhibiting EV endocytosis with dynasore blocked the increase in cytosolic Ca²⁺ and VSMC calcification. Increased ROS production resulted in increased EV release and decreased phagocytosis by VSMCs.

CONCLUSIONS

We show here that contractile VSMCs are resistant to calcification and identify Nox5 as a key regulator of VSMC phenotypic switching. Additionally, we describe a new mechanism of Ca²⁺ uptake via EVs and show that Ca²⁺ induces ROS production in VSMCs via Nox5. ROS production is required for release of EVs, which promote calcification. Identifying molecular pathways that control Nox5 and VSMC-derived EVs provides potential targets to modulate vascular remodeling and calcification in the context of mineral imbalance. Graphic Abstract: A graphic abstract is available for this article.

S100A9-RAGE Axis Accelerates Formation of Macrophage-Mediated Extracellular Vesicle Microcalcification in Diabetes Mellitus

OBJECTIVE

Vascular calcification is a cardiovascular risk factor and accelerated in diabetes mellitus. Previous work has established a role for calcification-prone extracellular vesicles in promoting vascular calcification. However, the mechanisms by which diabetes mellitus provokes cardiovascular events remain incompletely understood. Our goal was to identify that increased S100A9 promotes the release of calcification-prone extracellular vesicles from human macrophages in diabetes mellitus. Approach and Results: Human primary macrophages exposed to high glucose (25 mmol/L) increased S100A9 secretion and the expression of receptor for advanced glycation end products (RAGE) protein. Recombinant S100A9 induced the expression of proinflammatory and osteogenic factors, as well as the number of extracellular vesicles with high calcific potential (alkaline phosphatase activity, P<0.001) in macrophages. Treatment with a RAGE antagonist or silencing with S100A9 siRNA in macrophages abolished these responses, suggesting that stimulation of the S100A9-RAGE axis by hyperglycemia favors a procalcific environment. We further showed that an imbalance between Nrf-2 (nuclear factor 2 erythroid related factor 2) and NF-κB (nuclear factor-κB) pathways contributes to macrophage activation and promotes a procalcific environment. In addition, streptozotocin-induced diabetic Apoe^-/-S100a9^-/- mice and mice treated with S100a9 siRNA encapsulated in macrophage-targeted lipid nanoparticles showed decreased inflammation and microcalcification in atherosclerotic plaques, as gauged by molecular imaging and comprehensive histological analysis. In human carotid plaques, comparative proteomics in patients with diabetes mellitus and histological analysis showed that the S100A9-RAGE axis associates with osteogenic activity and the formation of microcalcification.

CONCLUSIONS

Under hyperglycemic conditions, macrophages release calcific extracellular vesicles through mechanisms involving the S100A9-RAGE axis, thus contributing to the formation of microcalcification within atherosclerotic plaques.

Apelin-13 attenuates high glucose-induced calcification of MOVAS cells by regulating MAPKs and PI3K/AKT pathways and ROS-mediated signals

Vascular calcification (VC) is an inducement of many cardiovascular diseases. Clinic evidences have confirmed that diabetes was the independent risk factor for VC, and the mechanism has not been well explored. Apelin as a ligand molecule is widely found in the cardiovascular system and showed potential in inhibiting VC, but the inhibitory effect and mechanism of apelin-13 against high glucose-induced VC have not been investigated yet. Herein, apelin-13 was employed to inhibit high glucose-induced VC in mouse aortic vascular smooth muscle cells (MOVAS), and the underlying mechanism was explored. The results showed that apelin-13 significantly inhibited high glucose-induced cells proliferation, migration and invasion of MOVAS cells. Apelin-13 also effectively attenuated high glucose-induced calcification by inhibiting alkaline phosphatase (ALP) activity and expression. Further investigation revealed that apelin-13 dramatically suppressed high glucose-induced DNA damage through inhibiting reactive oxide species (ROS) generation. Moreover, apelin-13 also effectively improved high glucose-induced dysfunction of MAPKs and PI3K/AKT. Inhibition of ERK by inhibitor (U0126) significantly blocked high glucose-induced calcification, which further confirmed the significance of MAPKs. Taken together, these results suggested that apelin-13 had the potential to attenuate high glucose-induced calcification of MOVAS cells by inhibiting ROS-mediated DNA damage and regulating MAPKs and PI3K/AKT pathways. Our findings validated the strategy of using apelin-13 maybe a novel way in treating high glucose-mediated VC.

DNA Damage Response: A Molecular Lynchpin in the Pathobiology of Arteriosclerotic Calcification

Vascular calcification is a ubiquitous pathology of aging. Oxidative stress, persistent DNA damage, and senescence are major pathways driving both cellular and tissue aging, and emerging evidence suggests that these pathways are activated, and even accelerated, in patients with vascular calcification. The DNA damage response-a complex signaling platform that maintains genomic integrity-is induced by oxidative stress and is intimately involved in regulating cell death and osteogenic differentiation in both bone and the vasculature. Unexpectedly, a posttranslational modification, PAR (poly[ADP-ribose]), which is a byproduct of the DNA damage response, initiates biomineralization by acting to concentrate calcium into spheroidal structures that can nucleate apatitic mineral on the ECM (extracellular matrix). As we start to dissect the molecular mechanisms driving aging-associated vascular calcification, novel treatment strategies to promote healthy aging and delay pathological change are being unmasked. Drugs targeting the DNA damage response and senolytics may provide new avenues to tackle this detrimental and intractable pathology.

Vascular Calcification: An Important Understanding in Nephrology

Vascular calcification (VC) is a life-threatening state in chronic kidney disease (CKD). High cardiovascular mortality and morbidity of CKD cases may root from medial VC promoted by hyperphosphatemia. Vascular calcification is an active, highly regulated, and complex biological process that is mediated by genetics, epigenetics, dysregulated form of matrix mineral metabolism, hormones, and the activation of cellular signaling pathways. Moreover, gut microbiome as a source of uremic toxins (eg, phosphate, advanced glycation end products and indoxyl-sulfate) can be regarded as a potential contributor to VC in CKD. Here, an update on different cellular and molecular processes involved in VC in CKD is discussed to elucidate the probable therapeutic pathways in the future.

Biomarkers of vascular calcification in serum

Over the last decades, the association between vascular calcification (VC) and all-cause/cardiovascular mortality, especially in patients with high atherogenic status, such as those with diabetes and/or chronic kidney disease, has been repeatedly highlighted. For over a century, VC has been noted as a passive, degenerative, aging process without any treatment options. However, during the past decades, studies confirmed that mineralization of the arteries is an active, complex process, similar to bone genesis and formation. The main purpose of this review is to provide an update of the existing biomarkers of VC in serum and develop the various pathogenetic mechanisms underlying the calcification process, including the pivotal roles of matrix Gla protein, osteoprotegerin, bone morphogenetic proteins, fetuin-a, fibroblast growth-factor-23, osteocalcin, osteopontin, osteonectin, sclerostin, pyrophosphate, Smads, fibrillin-1 and carbonic anhydrase II.

Pathophysiological and Genetic Aspects of Vascular Calcification

Recent evidence suggests that vascular calcification is an independent cardiovascular risk factor (CRF) of morbidity and mortality. New studies point out the existence of a complex physiopathological mechanism that involves inflammation, oxidation, the release of chemical mediators, and genetic factors that promote the osteochondrogenic differentiation of vascular smooth muscle cells (VSMC). This review will evaluate the main mechanisms involved in the pathophysiology and genetics modulation of the process of vascular calcification. Objective. A systematic review of the pathophysiology factors involved in vascular calcification and its genetic influence was performed. Methods. A systematic review was conducted in the Medline and PubMed databases and were searched for studies concerning vascular calcification using the keywords and studies published until 2020/01 in English. Inclusion Criteria. Studies in vitro, animal models, and humans. These include cohort (both retrospective and prospective cohort studies), case-control, cross-sectional, and systematic reviews. Exclusion Criteria. Studies before 2003 of the existing literature.

Vascular Calcification-New Insights Into Its Mechanism

Vascular calcification (VC), which is categorized by intimal and medial calcification, depending on the site(s) involved within the vessel, is closely related to cardiovascular disease. Specifically, medial calcification is prevalent in certain medical situations, including chronic kidney disease and diabetes. The past few decades have seen extensive research into VC, revealing that the mechanism of VC is not merely a consequence of a high-phosphorous and -calcium milieu, but also occurs via delicate and well-organized biologic processes, including an imbalance between osteochondrogenic signaling and anticalcific events. In addition to traditionally established osteogenic signaling, dysfunctional calcium homeostasis is prerequisite in the development of VC. Moreover, loss of defensive mechanisms, by microorganelle dysfunction, including hyper-fragmented mitochondria, mitochondrial oxidative stress, defective autophagy or mitophagy, and endoplasmic reticulum (ER) stress, may all contribute to VC. To facilitate the understanding of vascular calcification, across any number of bioscientific disciplines, we provide this review of a detailed updated molecular mechanism of VC. This encompasses a vascular smooth muscle phenotypic of osteogenic differentiation, and multiple signaling pathways of VC induction, including the roles of inflammation and cellular microorganelle genesis.

The biology of vascular calcification

Vascular calcification (VC), characterized by different mineral deposits (i.e., carbonate apatite, whitlockite and hydroxyapatite) accumulating in blood vessels and valves, represents a relevant pathological process for the aging population and a life-threatening complication in acquired and in genetic diseases. Similarly to bone remodeling, VC is an actively regulated process in which many cells and molecules play a pivotal role. This review aims at: (i) describing the role of resident and circulating cells, of the extracellular environment and of positive and negative factors in driving the mineralization process; (ii) detailing the types of VC (i.e., intimal, medial and cardiac valve calcification); (iii) analyzing rare genetic diseases underlining the importance of altered pyrophosphate-dependent regulatory mechanisms; (iv) providing therapeutic options and perspectives.

Induced osteogenic differentiation of human smooth muscle cells as a model of vascular calcification

Vascular calcification is a severe pathological event in the manifestation of atherosclerosis. Pathogenic triggers mediating osteogenic differentiation of arterial smooth muscle cells (SMC) in humans remain insufficiently understood and are to a large extent investigated in animal models or cells derived thereof. Here, we describe an in vitro model based on SMC derived from healthy and diseased humans that allows to comprehensively investigate vascular calcification mechanisms. Comparing the impact of the commonly used SMC culture media VascuLife, DMEM, and M199, cells were characterised by immunofluorescence, flow cytometry, qPCR, and regarding their contractility and proliferative capacity. Irrespective of the arterial origin, the clinical background and the expansion medium used, all cells expressed typical molecular SMC marker while contractility varied between donors. Interestingly, the ability to induce an osteogenic differentiation strongly depended on the culture medium, with only SMC cultured in DMEM depositing calcified matrix upon osteogenic stimulation, which correlated with increased alkaline phosphatase activity, increased inorganic phosphate level and upregulation of osteogenic gene markers. Our optimized model is suitable for donor-oriented as well as broader screening of potential pathogenic mediators triggering vascular calcification. Translational studies aiming to identify and to evaluate therapeutic targets in a personalized fashion would be feasible.

Arterial Stiffness: A Focus on Vascular Calcification and Its Link to Bone Mineralization

This review focuses on the association between vascular calcification and arterial stiffness, highlighting the important genetic factors, systemic and local microenvironmental signals, and underlying signaling pathways and molecular regulators of vascular calcification. Elevated oxidative stress appears to be a common procalcification factor that induces osteogenic differentiation and calcification of vascular cells in a variety of disease conditions such as atherosclerosis, diabetes mellitus, and chronic kidney disease. Thus, the role of oxidative stress and oxidative stress-regulated signals in vascular smooth muscle cells and their contributions to vascular calcification are highlighted. In relation to diabetes mellitus, the regulation of both hyperglycemia and increased protein glycosylation, by AGEs (advanced glycation end products) and O-linked β-N-acetylglucosamine modification, and its role in enhancing intracellular pathophysiological signaling that promotes osteogenic differentiation and calcification of vascular smooth muscle cells are discussed. In the context of chronic kidney disease, this review details the role of calcium and phosphate homeostasis, parathyroid hormone, and specific calcification inhibitors in regulating vascular calcification. In addition, the impact of the systemic and microenvironmental factors on respective intrinsic signaling pathways that promote osteogenic differentiation and calcification of vascular smooth muscle cells and osteoblasts are compared and contrasted, aiming to dissect the commonalities and distinctions that underlie the paradoxical vascular-bone mineralization disorders in aging and diseases.

Phenomenon of osteocyte lacunar mineralization: indicator of former osteocyte death and a novel marker of impaired bone quality?

An increasing number of patients worldwide suffer from bone fractures that occur after low intensity trauma. Such fragility fractures are usually associated with advanced age and osteoporosis but also with long-term immobilization, corticosteroid therapy, diabetes mellitus, and other endocrine disorders. It is important to understand the skeletal origins of increased bone fragility in these conditions for preventive and therapeutic strategies to combat one of the most common health problems of the aged population. This review summarizes current knowledge pertaining to the phenomenon of micropetrosis (osteocyte lacunar mineralization). As an indicator of former osteocyte death, micropetrosis is more common in aged bone and osteoporotic bone. Considering that the number of mineralized osteocyte lacunae per bone area can distinguish healthy, untreated osteoporotic and bisphosphonate-treated osteoporotic patients, it could be regarded as a novel structural marker of impaired bone quality. Further research is needed to clarify the mechanism of lacunar mineralization and to explore whether it could be an additional target for preventing or treating bone fragility related to aging and various endocrine diseases.

Seaweed Porphyra yezoensis polysaccharides with different molecular weights inhibit hydroxyapatite damage and osteoblast differentiation of A7R5 cells

Vascular calcification (VC) is a common pathological manifestation in patients with cardiovascular diseases, leading to high mortality in patients with chronic kidney diseases. The deposition of hydroxyapatite (HAP) crystals on vascular smooth muscle cells leads to cell damage, which promotes osteogenic transformation. In this study, four different molecular weights (MWs ) of Porphyra yezoensis polysaccharides (PYP1, PYP2, PYP3, and PYP4 with MWs of 576, 49.5, 12.6, and 4.02 kDa, respectively) were used to coat HAP, and the differences in toxicity and calcification of HAP on A7R5 cells before and after coating were studied. The results showed that PYPs could effectively reduce HAP damage to the A7R5 cells. Under the protection of PYPs, cell viability increased and lactate dehydrogenase release, active oxygen level, and cell necrosis rate decreased; also, the amount of the HAP crystals adhering to cell surfaces and entering cells decreased. PYPs with low molecular weights presented better protective effects than high-molecular-weight PYPs. PYPs also inhibited the osteogenic transformation of the A7R5 cells induced by HAP and decreased alkaline phosphatase (ALP) activity and expressions of bone/chondrocyte phenotype genes (runt-related factor 2, ALP, osteopontin, and osteocalcin). In the adenine-induced chronic renal failure (CRF) mouse VC model, PYP4 was found to obviously inhibit the aortic calcium level, and it also inhibited the serum creatinine, serum phosphorus and serum BUN levels. PYP4 (least molecular weight) showed the best inhibitory effect on calcification and may be considered as a candidate drug with therapeutic potential for inhibiting cellular damage and osteoblast differentiation induced by the HAP crystals.

Vascular Smooth Muscle Cell-Derived Exosomal MicroRNAs Regulate Endothelial Cell Migration Under PDGF Stimulation

Intercellular communication between vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) is essential for the maintenance of vascular homeostasis. The presence of exosomes, a recently discovered player in vascular cell communication, has been associated with vascular disease progression. However, the detailed mechanism of how the signal mediated by exosomes affects the function of vascular cells during vascular pathogenesis is yet to be further understood. In this study, we investigated the expression of exosomal microRNAs (miRNAs) secreted by VSMCs and their functional relevance to ECs in pathogenesis, including their role in processes such as platelet-derived growth factor (PDGF) stimulation. We observed that PDGF stimulation contributes to a change in exosomal miRNA release from VSMCs; specifically, miR-1246, miR-182, and miR-486 were deficient in exosomes derived from PDGF-stimulated VSMCs. The reduced miRNA expression in these exosomes is associated with an increase in EC migration. These findings increase our understanding of exosome-mediated crosstalk between vascular cells under a pathological condition.

Effect of Calcium and Vitamin D Co-supplementation on Blood Pressure: A Systematic Review and Meta-Analysis

PURPOSE

Vitamin D and calcium insufficiency has been related to elevated blood pressure (BP) and cardiovascular complications. This systematic review and meta-analysis investigates the effect of calcium and vitamin D co-supplementation on BP.

METHODS

A systematic search was conducted of electronic databases, including Web of Sciences, MEDLINE, Scopus, EMBASE, and the Cochrane Library, along with searches of gray literature and reference lists from included trials. There were no language restrictions, and the databases were searched from inception to October 2019. Randomized controlled trials, using calcium and vitamin D co-supplementation and reporting mean systolic BP and/or diastolic BP (DBP) with SDs, were included in the systematic review. Articles were evaluated independently by 2 researchers based on inclusion and exclusion criteria. A random effects model was conducted to synthesize the data.

FINDINGS

Eight trials were included in the meta-analysis. Meta-analysis of these 8 trials indicated a nonsignificant reduction in systolic BP in the calcium and vitamin D co-supplementation group compared with control (standardized mean difference, -0.23; 95% CI, -0.52 to 0.06). Conversely, there was a statistically significant decrease in DBP (standardized mean difference, -0.29; 95% CI, -0.55 to -0.02). Subgroup analysis suggested that young adults achieve a greater reduction in DBP than other age groups.

IMPLICATIONS

Calcium and vitamin D co-supplementation can modulate DBP and should be investigated more specifically in large, well-designed trials of hypertensive populations. (Clin Ther. 2020;42:XXX-XXX) © 2020 Elsevier HS Journals, Inc.

Calcification in Atherosclerotic Plaque Vulnerability: Friend or Foe?

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

Cardiovascular calcification: artificial intelligence and big data accelerate mechanistic discovery

Cardiovascular calcification is a health disorder with increasing prevalence and high morbidity and mortality. The only available therapeutic options for calcific vascular and valvular heart disease are invasive transcatheter procedures or surgeries that do not fully address the wide spectrum of these conditions; therefore, an urgent need exists for medical options. Cardiovascular calcification is an active process, which provides a potential opportunity for effective therapeutic targeting. Numerous biological processes are involved in calcific disease, including matrix remodelling, transcriptional regulation, mitochondrial dysfunction, oxidative stress, calcium and phosphate signalling, endoplasmic reticulum stress, lipid and mineral metabolism, autophagy, inflammation, apoptosis, loss of mineralization inhibition, impaired mineral resorption, cellular senescence and extracellular vesicles that act as precursors of microcalcification. Advances in molecular imaging and big data technology, including in multiomics and network medicine, and the integration of these approaches are helping to provide a more comprehensive map of human disease. In this Review, we discuss ectopic calcification processes in the cardiovascular system, with an emphasis on emerging mechanistic knowledge obtained through patient data and advances in imaging methods, experimental models and multiomics-generated big data. We also highlight the potential and challenges of artificial intelligence, machine learning and deep learning to integrate imaging and mechanistic data for drug discovery.

The antagonism of 6-shogaol in high-glucose-activated NLRP3 inflammasome and consequent calcification of human artery smooth muscle cells

Background

Vascular calcification is the major reason for high mortality of cardiovascular complications for diabetes. Interleukin (IL)-1β has been implicated in this pathogenesis, but its precise role and clinical evidence have not been clearly identified. Hence, this study was aimed to investigate whether high concentration of glucose (HG), which mimics the hyperglycemia environment, could initiate vascular calcification through NLRP3/IL-1β inflammasome and the underlying mechanism. Recently, 6-shogaol, a major ginger derivate, has been elucidated its pharmaceutic role for various diseases. Therefore, the aims of this study also determined 6-shogaol effect in vascular calcification of HG initiation.

Result

Human artery smooth muscle cells (HASMCs) were used in this study. Glucose concentrations at 5 and 25 mM were defined as normal and HG status, respectively. The results showed that HG could increase the NLRP3, cleaved caspase 1, and pro/mature IL-1β levels to induce the expressions of bone-related matrix proteins and subsequent HASMC calcification. This process was regulated by Akt activation and reactive oxygen species (ROS) production. Moreover, 6-shogaol could inhibit the Akt/ROS signaling and NLRP3/caspase 1/IL-1β inflammasome and hence attenuated HASMC calcification.

Conclusions

This study elucidates the detailed mechanism of HG-initiated HASMC calcification through NLRP3/caspase 1/IL-1β inflammasome and indicates a potential therapeutic role of 6-shogaol in vascular calcification complication of diabetes.

Bavachin Protects Human Aortic Smooth Muscle Cells Against β-Glycerophosphate-Mediated Vascular Calcification and Apoptosis via Activation of mTOR-Dependent Autophagy and Suppression of β-Catenin Signaling

Vascular calcification is a major complication of cardiovascular disease and chronic renal failure. Autophagy help to maintain a stable internal and external environment that is important for modulating arteriosclerosis, but its pathogenic mechanism is far from clear. Here, we aimed to identify the bioactive compounds from traditional Chinese medicines (TCM) that exhibit an anti-arteriosclerosis effect. In β-glycerophosphate (β-GP)-stimulated human aortic smooth muscle cells (HASMCs), the calcium level was increased and the expression of the calcification-related proteins OPG, OPN, Runx2, and BMP2 were all up-regulated, followed by autophagy induction and apoptosis. Meanwhile, we further revealed that β-GP induced apoptosis of human osteoblasts and promoted differentiation of osteoblasts through Wnt/β-catenin signaling. Bavachin, a natural compound from Psoralea corylifolia, dose-dependently reduced the level of intracellular calcium and the expression of calcification-related proteins OPG, OPN, Runx2 and BMP2, thus inhibiting cell apoptosis. In addition, bavachin increased LC3-II and beclin1 expression, along with intracellular LC3-II puncta formation, which autophagy induction is Atg7-dependent and is regulated by suppression of mTOR signaling. Furthermore, addition of autophagy inhibitor, wortmannin (WM) attenuated the inhibitory effect of bavachin on β-GP-induced calcification and apoptosis in HASMCs. Collectively, the present study revealed that bavachin protects HASMCs against apoptosis and calcification by activation of the Atg7/mTOR-autophagy pathway and suppression of the β-catenin signaling, our findings provide a potential clinical application for bavachin in the therapy of cardiovascular disease.

Shape-dependent toxicity and mineralization of hydroxyapatite nanoparticles in A7R5 aortic smooth muscle cells

Vascular smooth muscle cell damage is a key step in inducing vascular calcification that yields hydroxyapatite (HAP) as a major product. The effect of the shape of HAP on the damage to vascular smooth muscle cells has yet to be investigated. In this study, we compared the differences in toxicity of four various morphological nano-HAP crystals, namely, H-Rod, H-Needle, H-Sphere, and H-Plate, in rat aortic smooth muscle cells (A7R5). The sizes of these crystals were 39 nm × 115 nm, 41 nm ×189 nm, 56 nm × 56 nm, and 91 nm × 192 nm, respectively. Results showed that all HAPs decreased cell viability, disorganized cell morphology, disrupted cell membranes, increased intracellular reactive oxygen species concentration, decreased mitochondrial membrane potential, decreased lysosome integrity, increased alkaline phosphatase activity, and increased intracellular calcium concentration, resulting in cell necrosis. The cytotoxicity of the four kinds of HAP was ranked as follows: H-Plate > H-Sphere > H-Needle > H-Rod. The cytotoxicity of each crystal was positively correlated with the following factors: large specific surface area, high electrical conductivity and low surface charge. HAP accelerated calcium deposits on the A7R5 cell surface and induced the expression of osteogenic proteins, such as BMP-2, Runx2, OCN, and ALP. The crystals with high cytotoxicity caused more calcium deposits on the cell surface, higher expression levels of osteogenic protein, and stronger osteogenic transformation abilities. These findings elucidated the relationship between crystal shape and cytotoxicity and provided theoretical references for decreasing the risks of vascular calcification.

Implications of serial coronary computed tomography angiography in the evaluation of coronary plaque progression

PURPOSE OF REVIEW

The purpose is to review the use of coronary computed tomography (CT) angiography to assess coronary plaque burden/progression and to discuss about recent clinical trials that have utilized this imaging modality to study the effect of new pharmacotherapies on plaque burden/progression.

RECENT FINDINGS

There are numerous clinical trials that have utilized coronary CT angiography to demonstrate the potential benefits of statins, apixaban, rivaroxaban, aged garlic extract, biologic agents, and omega-3 fatty acids to reduce coronary plaque progression. Coronary CT angiography can identify high-risk plaques and can also quantify total plaque burden, both of which are independent risk factors to predict major adverse cardiac events.

SUMMARY

Coronary heart disease remains one of the leading cause of mortality in the world. Utilizing coronary CT angiography, it is possible to identify rupture-prone plaques and also to quantify the total plaque burden. New pharmacotherapies that have the potential to reduce plaque progression have been used in clinical trials and these trials have utilized coronary CT angiography to track coronary atheroma progression. In future, we will see frequent utilization of coronary CT angiography to track coronary atheroma.

Barley-ß-glucans reduce systemic inflammation, renal injury and aortic calcification through ADAM17 and neutral-sphingomyelinase2 inhibition

In chronic kidney disease (CKD), hyperphosphatemia-induced inflammation aggravates vascular calcification (VC) by increasing vascular smooth muscle cell (VSMC) osteogenic differentiation, ADAM17-induced renal and vascular injury, and TNFα-induction of neutral-sphingomyelinase2 (nSMase2) to release pro-calcifying exosomes. This study examined anti-inflammatory β-glucans efficacy at attenuating systemic inflammation in health, and renal and vascular injury favoring VC in hyperphosphatemic CKD. In healthy adults, dietary barley β-glucans (Bβglucans) reduced leukocyte superoxide production, inflammatory ADAM17, TNFα, nSMase2, and pro-aging/pro-inflammatory STING (Stimulator of interferon genes) gene expression without decreasing circulating inflammatory cytokines, except for γ-interferon. In hyperphosphatemic rat CKD, dietary Bβglucans reduced renal and aortic ADAM17-driven inflammation attenuating CKD-progression (higher GFR and lower serum creatinine, proteinuria, kidney inflammatory infiltration and nSMase2), and TNFα-driven increases in aortic nSMase2 and calcium deposition without improving mineral homeostasis. In VSMC, Bβglucans prevented LPS- or uremic serum-induced rapid increases in ADAM17, TNFα and nSMase2, and reduced the 13-fold higher calcium deposition induced by prolonged calcifying conditions by inhibiting osteogenic differentiation and increases in nSMase2 through Dectin1-independent actions involving Bβglucans internalization. Thus, dietary Bβglucans inhibit leukocyte superoxide production and leukocyte, renal and aortic ADAM17- and nSMase2 gene expression attenuating systemic inflammation in health, and renal injury and aortic calcification despite hyperphosphatemia in CKD.

Mechanisms of Vascular Calcification in Kidney Disease

The increase in prevalence and severity of vascular calcification in chronic kidney disease is a result of complex interactions between changes in the vascular bed, mineral metabolites, and other uremic factors. Vascular calcification can occur in the intima and the media of arterial wall. Under permissive conditions, vascular smooth muscle cells (VSMCs) can transform to osteoblast-like phenotype. The membrane-bound vesicles released from transformed VSMCs and the apoptotic bodies derived from dying VSMCs serve as nucleating structures for calcium crystal formation. Alterations in the quality and the quantity of endogenous calcification inhibitors also give rise to an environment that potentiates calcification.

Mineral Bone Abnormalities and Vascular Calcifications

Vascular calcification (VC) is common in chronic kidney disease, increases in prevalence as patients progress to end-stage renal disease, and is significantly associated with mortality. VC is a complex and highly regulated process similar to bone formation whereby hydroxyapatite crystals deposit in the intimal or medial layer of arteries. Mineral bone abnormalities are common in chronic kidney disease; reduction in glomerular filtration rate and changes in vitamin D, parathyroid hormone, and fibroblast growth factor 23 result in the dysregulation of phosphorus and calcium metabolism. Cell culture studies, animal models, and observational and clinical studies all suggest this abnormal mineral metabolism plays a role in the initiation and progression of VC in kidney disease. This review will focus on these mineral bone abnormalities and how they may contribute to mechanisms that induce VC in kidney disease.

The role of smooth muscle cells in plaque stability: Therapeutic targeting potential

Events responsible for cardiovascular mortality and morbidity are predominantly caused by rupture of "vulnerable" atherosclerotic lesions. Vascular smooth muscle cells (VSMCs) play a key role in atherogenesis and have historically been considered beneficial for plaque stability. VSMCs constitute the main cellular component of the protective fibrous cap within lesions and are responsible for synthesising strength-giving extracellular matrix components. However, lineage-tracing experiments in mouse models of atherosclerosis have shown that, in addition to the fibrous cap, VSMCs also give rise to many of the cell types found within the plaque core. In particular, VSMCs generate a substantial fraction of lipid-laden foam cells, and VSMC-derived cells expressing markers of macrophages, osteochondrocyte, and mesenchymal stem cells have been observed within lesions. Here, we review recent studies that have changed our perspective on VSMC function in atherosclerosis and discuss how VSMCs could be targeted to increase plaque stability.

Calcium Signaling and Tissue Calcification

Calcification is a regulated physiological process occurring in bones and teeth. However, calcification is commonly found in soft tissues in association with aging and in a variety of diseases. Over the last two decades, it has emerged that calcification occurring in diseased arteries is not simply an inevitable build-up of insoluble precipitates of calcium phosphate. In some cases, it is an active process in which transcription factors drive conversion of vascular cells to an osteoblast or chondrocyte-like phenotype, with the subsequent production of mineralizing "matrix vesicles." Early studies of bone and cartilage calcification suggested roles for cellular calcium signaling in several of the processes involved in the regulation of bone calcification. Similarly, calcium signaling has recently been highlighted as an important component in the mechanisms regulating pathological calcification. The emerging hypothesis is that ectopic/pathological calcification occurs in tissues in which there is an imbalance in the regulatory mechanisms that actively prevent calcification. This review highlights the various ways that calcium signaling regulates tissue calcification, with a particular focus on pathological vascular calcification.

Modifying Phosphate Toxicity in Chronic Kidney Disease

Phosphate toxicity is a well-established phenomenon, especially in chronic kidney disease (CKD), where hyperphosphatemia is a frequent occurrence when CKD is advanced. Many therapeutic efforts are targeted at phosphate, and comprise dietary intervention, modifying dialysis schemes, treating uncontrolled hyperparathyroidism and importantly, phosphate binder therapy. Despite all these interventions, hyperphosphatemia persists in many, and its pathological influence is ongoing. In nephrological care, a somewhat neglected aspect of treatment-when attempts fail to lower exposure to a toxin like phosphate-is to explore the possibility of "anti-dotes". Indeed, quite a long list of factors modify, or are mediators of phosphate toxicity. Addressing these, especially when phosphate itself cannot be sufficiently controlled, may provide additional protection. In this narrative overview, several factors are discussed that may qualify as either such a modifier or mediator, that can be influenced by other means than simply lowering phosphate exposure. A wider scope when targeting phosphate-induced comorbidity in CKD, in particular cardiovascular disease, may alleviate the burden of disease that is the consequence of this potentially toxic mineral in CKD.

Would acetazolamide inhibit progression of atheromatous vascular calcification?

Vascular calcification is a recognised source of morbidity among mid-age and elderly subjects. Its development follows classical mineralisation pathways, inhibited by acidosis. It is known that the final mechanism of tissue mineralization involves three processes, all of which are highly pH dependent. Calcium interacts with phosphate in its trivalent form, but this step is inhibited by pyrophosphate, itself a source of phosphate when hydrolysed by alkaline phosphatase. Separately, matrix vesicles create nucleation sites and may indirectly disrupt vascular smooth muscle cells. Metabolic acidosis acts at every point to delay mineralization. The diuretic acetazolamide creates a sustained mild acidosis with some phosphate loss and, though usually ineffective in the experimental model, has been used with success in certain clinical conditions. We suggest that acetazolamide, well studied and tolerated, might inhibit progression of vascular calcification in subjects at risk through its dual action of lowering tissue pH and local phosphate concentration.

Inhibition of vascular smooth muscle cell calcification by ATP analogues

Arterial medial calcification (AMC) has been associated with phenotypic changes in vascular smooth muscle cells (VSMCs) that reportedly makes them more osteoblast-like. Previous work has shown that ATP/UTP can inhibit AMC directly via P2 receptors and indirectly by NPP1-mediated hydrolysis to produce the mineralisation inhibitor, pyrophosphate (PP_i). This study investigated the role of P2X receptors in the inhibitory effects of extracellular nucleotides on VSMC calcification. We found that Bz-ATP, α,β-meATP and β,γ-meATP inhibited calcification by up to 100%. Culture in a high-phosphate medium (2 mM) was associated with increased VSMC death and apoptosis; treatment with Bz-ATP, α,β-meATP and β,γ-meATP reduced apoptosis to levels seen in non-calcifying cells. Calcification was also associated with alterations in the protein levels of VSMC (e.g. SM22α and SMA) and osteoblast-associated (e.g. Runx2 and osteopontin) markers; Bz-ATP, α,β-meATP and β,γ-meATP attenuated these changes in protein expression. Long-term culture with Bz-ATP, α,β-meATP and β,γ-meATP resulted in lower extracellular ATP levels and an increased rate of ATP breakdown. P2X receptor antagonists failed to prevent the inhibitory effects of these analogues suggesting that they act via P2X receptor-independent mechanisms. In agreement, the breakdown products of α,β-meATP and β,γ-meATP (α,β-meADP and methylene diphosphonate, respectively) also dose-dependently inhibited VSMC calcification. Furthermore, the actions of Bz-ATP, α,β-meATP and β,γ-meATP were unchanged in VSMCs isolated from NPP1-knockout mice, suggesting that the functional effects of these compounds do not involve NPP1-mediated generation of PP_i. Together, these results indicate that the inhibitory effects of ATP analogues on VSMC calcification and apoptosis in vitro may be mediated, at least in part, by mechanisms that are independent of purinergic signalling and PP_i.

Role of smooth muscle cells in vascular calcification: implications in atherosclerosis and arterial stiffness

Vascular calcification is associated with a significant increase in all-cause mortality and atherosclerotic plaque rupture. Calcification has been determined to be an active process driven in part by vascular smooth muscle cell (VSMC) transdifferentiation within the vascular wall. Historically, VSMC phenotype switching has been viewed as binary, with the cells able to adopt a physiological contractile phenotype or an alternate ‘synthetic’ phenotype in response to injury. More recent work, including lineage tracing has however revealed that VSMCs are able to adopt a number of phenotypes, including calcific (osteogenic, chondrocytic, and osteoclastic), adipogenic, and macrophagic phenotypes. Whilst the mechanisms that drive VSMC differentiation are still being elucidated it is becoming clear that medial calcification may differ in several ways from the intimal calcification seen in atherosclerotic lesions, including risk factors and specific drivers for VSMC phenotype changes and calcification. This article aims to compare and contrast the role of VSMCs in driving calcification in both atherosclerosis and in the vessel media focusing on the major drivers of calcification, including aging, uraemia, mechanical stress, oxidative stress, and inflammation. The review also discusses novel findings that have also brought attention to specific pro- and anti-calcifying proteins, extracellular vesicles, mitochondrial dysfunction, and a uraemic milieu as major determinants of vascular calcification.

Involvement of Vitamin K-Dependent Proteins in Vascular Calcification

Vascular calcification results from an imbalance of promoters and inhibitors of mineralization in the vascular wall, culminating in the creation of an organized extracellular matrix deposition. It is characterized by the accumulation of calcium phosphate complex and crystallization of hydroxyapatite in the tunica media, leading to vessel stiffening. The underlying initiators of dysregulated calcification maintenance are diverse. These range from the expression of bone-associated proteins, to the osteogenic transdifferentiation of smooth muscle cells to osteoblast-like cells, to the release of fragmented apoptotic bodies and mineralization competent extracellular vesicles by smooth muscle cells, which act as a nucleation site for the deposition of hydroxyapatite crystals. The process involves a complex interplay between vitamin K-dependent calcification-inhibitory proteins, such as matrix γ-carboxyglutamate acid (Gla) protein, Gla-rich protein and growth arrest-specific gene 6 protein, and stimulatory mediators, such as osteocalcin. Vitamin K plays an important role as a cofactor for posttranslational γ-carboxylation of matrix Gla proteins in converting to a biologically active conformation. Drugs that inhibit vitamin K, such as warfarin, impair γ-carboxylation of Gla proteins, resulting in the accumulation of uncarboxylated proteins lacking calcification-inhibitory capacity. This article overviews the involvement of systemically and locally expressed vitamin K-dependent proteins in vascular calcification and their potential as biomarkers of calcification.

Multifaceted Mechanisms of Vascular Calcification in Aging

Approximately 20% of the world’s population will be around or above 65 years of age by the next decade. Out of these, 40% are suspected to have cardiovascular diseases as a cause of mortality. Arteriosclerosis, characterized by increased vascular calcification, impairing Windkessel effect and tissue perfusion, and determining end-organ damage, is a hallmark of vascular pathology in the elderly population. Risk factors accumulated during aging affect the normal physiological and vascular aging process, which contributes to the progression of arteriosclerosis. Traditional risk factors, age-associated diseases, and respective regulating mechanisms influencing vascular calcification and vascular stiffness have been extensively studied for many years. Despite the well-known fact that aging alone can induce vascular damage, specific mechanisms that implicate physiological aging in vascular calcification, contributing to vascular stiffness, are poorly understood. This review focuses on mechanisms activated during normal aging, for example, cellular senescence, autophagy, extracellular vesicles secretion, and oxidative stress, along with the convergence of premature aging models’ pathophysiology, such as Hutchinson-Gilford Progeria (prelamin accumulation) and Klotho deficiency, to understand vascular calcification in aging. Understanding the mechanisms of vascular damage in aging that intersect with age-associated diseases and risk factors is crucial to foster innovative therapeutic targets to mitigate cardiovascular disease.

Visual Overview—

An online visual overview is available for this article.

The interplay between mineral metabolism, vascular calcification and inflammation in Chronic Kidney Disease (CKD): challenging old concepts with new facts

Chronic kidney disease (CKD) is one of the most powerful predictors of premature cardiovascular disease (CVD), with heightened susceptibility to vascular intimal and medial calcification associated with a high cardiovascular mortality. Abnormal mineral metabolism of calcium (Ca) and phosphate (P) and underlying (dys)regulated hormonal control in CKD-mineral and bone disorder (MBD) is often accompanied by bone loss and increased vascular calcification (VC). While VC is known to be a multifactorial process and a major risk factor for CVD, the view of primary triggers and molecular mechanisms complexity has been shifting with novel scientific knowledge over the last years. In this review we highlight the importance of calcium-phosphate (CaP) mineral crystals in VC with an integrated view over the complexity of CKD, while discuss past and recent literature aiming to highlight novel horizons on this major health burden. Exacerbated VC in CKD patients might result from several interconnected mechanisms involving abnormal mineral metabolism, dysregulation of endogenous calcification inhibitors and inflammatory pathways, which function in a feedback loop driving disease progression and cardiovascular outcomes. We propose that novel approaches targeting simultaneously VC and inflammation might represent valuable new prognostic tools and targets for therapeutics and management of cardiovascular risk in the CKD population.

Mechanisms of Matrix Vesicles Mediating Calcification Transition in Diabetic Plaque

Vascular calcification is a key character of advanced plaque in diabetic atherosclerosis. Microcalcification induces plaque rupture, whereas macrocalcification contributes to plaque stability. However, there is still no clear explanation for the formation and transition of these two types of calcification. Based on existing work and the latest international progress, this article provides a brief review of four aspects: calcification transition in plaque; matrix vesicle-mediated calcification transition in plaque; regulation mechanism of matrix vesicle-mediated calcification transition in diabetic plaque; and proposal of a new hypothesis, which may offer a new perspective on the study of the mechanism of calcification transition in plaque.

Shape-dependent adhesion and endocytosis of hydroxyapatite nanoparticles on A7R5 aortic smooth muscle cells

The interaction between nanohydroxyapatite (HAP) and smooth muscle cells is an important step in vascular calcification. However, the effect of the shape of HAP on adhesion and endocytosis to aortic smooth muscle cells has been rarely reported. Four different morphological HAP crystals (H-Rod, H-Needle, H-Sphere, and H-Plate) were selected to interact with rat aortic smooth muscle cells (A7R5). Fluorescence-labeled HAP was used to detect crystal adhesion and endocytosis and then pretreated with different endocytic inhibitors to explore the pathway of endocytotic crystals. The distribution of crystals inside and outside the cells and the crystal localization in lysosomes was observed through laser confocal microscopy. The effect of crystal on the cell cycle and the changes in the expression of phosphatidylserine, osteopontin, α-actin, core binding factor alpha 1, and osterix on the surface of A7R5 cells were detected. The adhesion and endocytosis of HAP on A7R5 cells were closely related to crystal shapes and ranked as follows: H-Plate > H-Sphere > H-Needle > H-Rod. H-Sphere and H-Needle were internalized into the cells mainly via the clathrin-mediated pathway, whereas H-Plate and H-Rod were internalized into the cells mainly via macropinocytosis. The endocytosed nano-HAP was mainly distributed in the cell lysosome. The adhesion and endocytosis of HAP to A7R5 cells were positively correlated with the specific surface area, and contact area of HAP and negatively correlated with the absolute value of Zeta and contact angle of HAP. This study provided insights into the effect of crystal morphology on vascular calcification and its mechanism.

Impact of Femoral Ossification on Local and Systemic Cardiovascular Patients' Condition

BACKGROUND

Vascular calcifications are associated with a high cardiovascular morbi-mortality in the coronary territory. In parallel, femoral arteries are more calcified and develop osteoid metaplasia (OM). This study was conducted to assess the predictive value of OM and local inflammation on the occurrence of mid- and long-term adverse cardiovascular events.

METHOD

Between 2008 and 2015, 86 atheromatous samples were harvested during femoral endarterectomy on 81 patients and processed for histomorphological analyses of calcifications and inflammation (monocytes and B cells). Histological findings were compared with the long-term follow-up of patients, including major adverse cardiac event (MACE), major adverse limb event (MALE), and mortality. Frequencies were presented as percentage, and continuous data, as mean and standard deviation. A P-value < 0.05 was considered statistically significant.

RESULTS

Median follow-up was 42.4 months (26.9-58.8). Twenty-eight percent of patients underwent a MACE; a MALE occurred in 18 (21%) limbs. Survival rate was 87.2% at 36 months. OM was found in 41 samples (51%), without any significant impact on the occurrence of MACE, MALE, or mortality. Preoperative white blood cell formulae revealed a higher rate of neutrophils associated with MACE (P = 0.04) and MALE (P = 0.0008), correlated with higher B cells counts in plaque samples.

CONCLUSIONS

OM is part of femoral calcifications in almost 50% of the cases but does not seem to be an independent predictive variable for MACE or MALE. However, a higher rate of B cell infiltration of the plaque and preoperative neutrophil blood count may be predictive of adverse events during follow-up.

Signaling pathways involved in vascular smooth muscle cell calcification during hyperphosphatemia

Medial vascular calcification has emerged as a putative key factor contributing to the excessive cardiovascular mortality of patients with chronic kidney disease (CKD). Hyperphosphatemia is considered a decisive determinant of vascular calcification in CKD. A critical role in initiation and progression of vascular calcification during elevated phosphate conditions is attributed to vascular smooth muscle cells (VSMCs), which are able to change their phenotype into osteo-/chondroblasts-like cells. These transdifferentiated VSMCs actively promote calcification in the medial layer of the arteries by producing a local pro-calcifying environment as well as nidus sites for precipitation of calcium and phosphate and growth of calcium phosphate crystals. Elevated extracellular phosphate induces osteo-/chondrogenic transdifferentiation of VSMCs through complex intracellular signaling pathways, which are still incompletely understood. The present review addresses critical intracellular pathways controlling osteo-/chondrogenic transdifferentiation of VSMCs and, thus, vascular calcification during hyperphosphatemia. Elucidating these pathways holds a significant promise to open novel therapeutic opportunities counteracting the progression of vascular calcification in CKD.

Multifaceted Mechanisms of Vascular Calcification in Aging

Approximately 20% of the world's population will be around or above 65 years of age by the next decade. Out of these, 40% are suspected to have cardiovascular diseases as a cause of mortality. Arteriosclerosis, characterized by increased vascular calcification, impairing Windkessel effect and tissue perfusion, and determining end-organ damage, is a hallmark of vascular pathology in the elderly population. Risk factors accumulated during aging affect the normal physiological and vascular aging process, which contributes to the progression of arteriosclerosis. Traditional risk factors, age-associated diseases, and respective regulating mechanisms influencing vascular calcification and vascular stiffness have been extensively studied for many years. Despite the well-known fact that aging alone can induce vascular damage, specific mechanisms that implicate physiological aging in vascular calcification, contributing to vascular stiffness, are poorly understood. This review focuses on mechanisms activated during normal aging, for example, cellular senescence, autophagy, extracellular vesicles secretion, and oxidative stress, along with the convergence of premature aging models' pathophysiology, such as Hutchinson-Gilford Progeria (prelamin accumulation) and Klotho deficiency, to understand vascular calcification in aging. Understanding the mechanisms of vascular damage in aging that intersect with age-associated diseases and risk factors is crucial to foster innovative therapeutic targets to mitigate cardiovascular disease. Visual Overview- An online visual overview is available for this article.

Role of Vascular Smooth Muscle Cell Phenotypic Switching and Calcification in Aortic Aneurysm Formation

Aortic aneurysm is a vascular disease whereby the ECM (extracellular matrix) of a blood vessel degenerates, leading to dilation and eventually vessel wall rupture. Recently, it was shown that calcification of the vessel wall is involved in both the initiation and progression of aneurysms. Changes in aortic wall structure that lead to aneurysm formation and vascular calcification are actively mediated by vascular smooth muscle cells. Vascular smooth muscle cells in a healthy vessel wall are termed contractile as they maintain vascular tone and remain quiescent. However, in pathological conditions they can dedifferentiate into a synthetic phenotype, whereby they secrete extracellular vesicles, proliferate, and migrate to repair injury. This process is called phenotypic switching and is often the first step in vascular pathology. Additionally, healthy vascular smooth muscle cells synthesize VKDPs (vitamin K-dependent proteins), which are involved in inhibition of vascular calcification. The metabolism of these proteins is known to be disrupted in vascular pathologies. In this review, we summarize the current literature on vascular smooth muscle cell phenotypic switching and vascular calcification in relation to aneurysm. Moreover, we address the role of vitamin K and VKDPs that are involved in vascular calcification and aneurysm. Visual Overview- An online visual overview is available for this article.

Exosomes: An emerging factor in atherosclerosis

Atherosclerosis is the main reason for morbidity and death caused by cardiovascular disease which leads to approximately 20% of total death around the world. Exosomes secreted by the cells is a kind of extracellular vesicles with lipid bilayer structure, containing a variety of cell specific lipid, nucleic acid and protein, involved in intercellular communication, plays an important role in different physiological and pathological process. In recent years, with the deepening of research, the role of exosomes in cardiovascular diseases has received extensive attention. This review summarizes the roles of exosomes and exosome-derived from microRNAs, proteins and DNA as biomarkers in the development of atherosclerosis, and explores the mechanism of exosome-mediated intercellular crosstalk in atherosclerosis, providing potential roles for diagnosis and treatment.

Vitamin K2-Dependent GGCX and MGP Are Required for Homeostatic Calcium Regulation of Sperm Maturation

A low-calcium microenvironment is essential for spermatozoa to mature in the epididymis; however, it remains unclear how dysregulation of epididymal luminal calcium is associated with male infertility. Using a warfarin-induced vitamin K2 deficiency rat model, we found that vitamin-K-dependent γ-glutamyl carboxylase (GGCX) and matrix Gla protein (MGP) were essential in extracellular calcium signaling of the intercellular communication required for epididymal sperm maturation. We found that GGCX and MGP co-localized in the vesicular structures of epididymal cells and spermatozoa. Calcium-regulated MGP binds to proteins in a biphasic manner; sub-millimolar calcium enhances, whereas excessive calcium inhibits, the binding. Bioinformatic analysis of the calcium-dependent MGP-bound proteome revealed that vesicle-mediated transport and membrane trafficking underlie the intercellular communication networks. We also identified an SNP mutation, rs699664, in the GGCX gene of infertile men with asthenozoospermia. Overall, we revealed that the GGCX-MGP system is integrated with the intercellular calcium signaling to promote sperm maturation.

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Epididymal sperm maturation requires VK2-dependent GGCX-mediated MGP carboxylation

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A GGCX SNP mutation is found in infertile men suffering from asthenozoospermia

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Carboxylated-MGP regulates intercellular calcium signaling in the epididymal lumen

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Calcium-regulated MGP binds to proteins in a biphasic-manner and favors low levels