Msx2 promotes cardiovascular calcification by activating paracrine Wnt signals

Nonclinical cardiovascular safety evaluation of romosozumab, an inhibitor of sclerostin for the treatment of osteoporosis in postmenopausal women at high risk of fracture

Romosozumab (EVENITY™ [romosozumab-aqqg in the US]) is a humanized monoclonal antibody that inhibits sclerostin and has been approved in several countries for the treatment of osteoporosis in postmenopausal women at high risk of fracture. Sclerostin is expressed in bone and aortic vascular smooth muscle (AVSM). Its function in AVSM is unclear but it has been proposed to inhibit vascular calcification, atheroprogression, and inflammation. An increased incidence of positively adjudicated serious cardiovascular adverse events driven by an increase in myocardial infarction and stroke was observed in romosozumab-treated subjects in a clinical trial comparing alendronate with romosozumab (ARCH; NCT01631214) but not in a placebo-controlled trial (FRAME; NCT01575834). To investigate the effects of sclerostin inhibition with sclerostin antibody on the cardiovascular system, a comprehensive nonclinical toxicology package with additional cardiovascular studies was conducted. Although pharmacodynamic effects were observed in the bone, there were no functional, morphological, or transcriptional effects on the cardiovascular system in animal models in the presence or absence of atherosclerosis. These nonclinical studies did not identify evidence that proves the association between sclerostin inhibition and adverse cardiovascular function, increased cardiovascular calcification, and atheroprogression.

Effects of Eicosapentaenoic Acid on Arterial Calcification

Arterial calcification is a hallmark of advanced atherosclerosis and predicts cardiovascular events. However, there is no clinically accepted therapy that prevents progression of arterial calcification. HMG-CoA reductase inhibitors, statins, lower low-density lipoprotein-cholesterol and reduce cardiovascular events, but coronary artery calcification is actually promoted by statins. The addition of eicosapentaenoic acid (EPA) to statins further reduced cardiovascular events in clinical trials, JELIS and REDUCE-IT. Additionally, we found that EPA significantly suppressed arterial calcification in vitro and in vivo via suppression of inflammatory responses, oxidative stress and Wnt signaling. However, so far there is a lack of evidence showing the effect of EPA on arterial calcification in a clinical situation. We reviewed the molecular mechanisms of the inhibitory effect of EPA on arterial calcification and the results of some clinical trials.

Association between Serum Dickkopf-1 (DKK-1) Glycoprotein and Calcific Deposits on Cardiac Valves and Carotid Intimal-Medial Thickness in Hemodialysis Patients

BACKGROUND

Cardiac valve calcification (CVC) is common in hemodialysis (HD) patients, and associated with cardiovascular and all-cause mortality. Once believed to be a passive process, it is now understood that the Wnt signaling pathway has a major role. The aim of the current study was to assess the relationship between circulating DKK-1, a negative regulator of the Wnt signaling pathway, and CVC, as well as carotid intimal-medial thickness (CIMT) in HD patients.

METHODS

We enrolled 74 consecutive adults on maintenance HD. Echocardiographic calcification of the mitral valve (MV) and aortic valve (AV) were detected according to Wilkins score (range 0-4), and the study of Tenenbaum et al. [Int J Cardiol. 2004 Mar;94(1):7-13] (range 0-4), respectively. CVC severity was calculated by a supposed score (range 0-8) that represents the sum of calcification grade of MV and AV. CVC severity was classified into absent (CVC score = 0), mild (CVC score = 1-2), moderate (CVC score = 3-4), and severe (CVC score ≥5). Demographic and biochemical data were collected in addition to serum DKK-1 levels and CIMT.

RESULTS

CVC was present in 67 patients (91.0%). There was a highly significant negative correlation between serum DKK-1 level and CVC score (r = -0.492; p ≤ 0.001), as well as CIMT (r = -0.611; p ≤ 0.001). Age and CIMT were independent determinants of CVC.

CONCLUSIONS

CVC is almost present in all HD patients. DKK-1 seems to have a direct relation with CVC and CIMT in HD patients. Age is the strongest independent determinant of CVC.

Bone mineral density and mortality in end-stage renal disease patients

Osteoporosis characterized by low bone mineral density (BMD) as assessed by dual-energy X-ray absorptiometry (DXA) is common among end-stage renal disease (ESRD) patients and associates with high fracture incidence and high all-cause mortality. This is because chronic kidney disease-mineral bone disorders (CKD-MBDs) promote not only bone disease (osteoporosis and renal dystrophy) but also vascular calcification and cardiovascular disease. The disturbed bone metabolism in ESRD leads to 'loss of cortical bone' with increased cortical porosity and thinning of cortical bone rather than to loss of trabecular bone. Low BMD, especially at cortical-rich bone sites, is closely linked to CKD-MBD, vascular calcification and poor cardiovascular outcomes. These effects appear to be largely mediated by shared mechanistic pathways via the 'bone-vascular axis' through which impaired bone status associates with changes in the vascular wall. Thus, bone is more than just the scaffolding that holds the body together and protects organs from external forces but is-in addition to its physical supportive function-also an active endocrine organ that interacts with the vasculature by paracrine and endocrine factors through pathways including Wnt signalling, osteoprotegerin (OPG)/receptor activator of nuclear factor-κB (RANK)/RANK ligand system and the Galectin-3/receptor of advanced glycation end products axis. The insight that osteogenesis and vascular calcification share many similarities-and the knowledge that vascular calcification is a cell-mediated active rather than a passive mineralization process-suggest that low BMD and vascular calcification ('vascular ossification') to a large extent represent two sides of the same coin. Here, we briefly review changes of BMD in ESRD as observed using different DXA methods (central and whole-body DXA) at different bone sites for BMD measurements, and summarize recent knowledge regarding the relationships between 'low BMD' and 'fracture incidence, vascular calcification and increased mortality' in ESRD patients, as well as potential 'molecular mechanisms' underlying these associations.

Reduction of Secreted Frizzled-Related Protein 5 Drives Vascular Calcification through Wnt3a-Mediated Rho/ROCK/JNK Signaling in Chronic Kidney Disease

Vascular calcification (VC) is commonly associated with bone loss in patients with chronic kidney disease (CKD). The Wingless-related integration site (Wnt) regulates osteoblast activation through canonical signaling pathways, but the common pathophysiology of these pathways during VC and bone loss has not been identified. A rat model of adenine-induced CKD with VC was used in this study. The rats were fed 0.75% adenine (2.5% protein, 0.92% phosphate) with or without intraperitoneal injection of calcitriol (0.08 µg/kg/day) for 4 weeks. Angiotensin II (3 µM)-induced VC was achieved in high phosphate medium (3 mM) through its effect on vascular smooth muscle cells (VSMCs). In an mRNA profiler polymerase chain reaction assay of the Wnt signaling pathway, secreted frizzled-related protein 5 (sFRP5) levels were significantly decreased in the CKD rat model compared with the control group. The repression of sFRP5 on VSMC trans-differentiation was mediated through Rho/Rho-associated coiled coil containing protein kinase (ROCK) and c-Jun N-terminal kinase (JNK) pathways activated by Wnt3a. In a proof of concept study conducted with patients with CKD, serum sFRP5 concentrations were significantly lower in subjects with VC than in those without VC. Our findings suggest that repression of sFRP5 is associated with VC in the CKD environment via activation of the noncanonical Wnt pathway, and thus that sFRP5 might be a novel therapeutic target for VC in CKD.

Calcific Aortic Valve Disease-Natural History and Future Therapeutic Strategies

Calcific aortic valve disease (CAVD) is the most frequent heart valve disorder. It is characterized by an active remodeling process accompanied with valve mineralization, that results in a progressive aortic valve narrowing, significant restriction of the valvular area, and impairment of blood flow.The pathophysiology of CAVD is a multifaceted process, involving genetic factors, chronic inflammation, lipid deposition, and valve mineralization. Mineralization is strictly related to the inflammatory process in which both, innate, and adaptive immunity are involved. The underlying pathophysiological pathways that go from inflammation to calcification and, finally lead to severe stenosis, remain, however, incompletely understood. Histopathological studies are limited to patients with severe CAVD and no samples are available for longitudinal studies of disease progression. Therefore, alternative routes should be explored to investigate the pathogenesis and progression of CAVD.Recently, increasing evidence suggests that epigenetic markers such as non-coding RNAs are implicated in the landscape of phenotypical changes occurring in CAVD. Furthermore, the microbiome, an essential player in several diseases, including the cardiovascular ones, has recently been linked to the inflammation process occurring in CAVD. In the present review, we analyze and discuss the CAVD pathophysiology and future therapeutic strategies, focusing on the real and putative role of inflammation, calcification, and microbiome.

Diabetes and calcification: The potential role of anti-diabetic drugs on vascular calcification regression

Vascular calcification (VC) has been well-established as an independent and strong predictor of cardiovascular diseases (CVD) as well as major cardiac adverse events (MACE). VC is associated with increased mortality in patients with CVD. Pathologically, VC is now believed to be a multi-directional active process ultimately resulting in ectopic calcium deposition in vascular beds. On the other hand, prevalence of diabetes mellitus (DM) is gradually increasing thus making the current population more prone to future CVD. Although the mechanisms involved in development and progression of VC in DM patients are not fully understood, a series of evidences demonstrated positive association between DM and VC. It has been highlighted that different cellular pathways are involved in this process. These intermediates such as tumor necrosis factor alpha (TNF-α), various interleukins (ILs) and different cell-signaling pathways are over-expressed in DM patients leading to development of VC. Thus, considering the burden and significance of VC it is of great importance to find a therapeutic approach to prevent or minimize the development of VC in DM patients. Over the past few years various anti diabetic drugs (ADDs) have been introduced and many of them showed desired glucose control. But no study demonstrated the effects of these medications on regression of VC. In this review, we will briefly discuss the current understanding on DM and VC and how commonly used ADDs modulate the development or progression of VC.

Roles of Histone Acetylation Modifiers and Other Epigenetic Regulators in Vascular Calcification

Vascular calcification (VC) is characterized by calcium deposition inside arteries and is closely associated with the morbidity and mortality of atherosclerosis, chronic kidney disease, diabetes, and other cardiovascular diseases (CVDs). VC is now widely known to be an active process occurring in vascular smooth muscle cells (VSMCs) involving multiple mechanisms and factors. These mechanisms share features with the process of bone formation, since the phenotype switching from the contractile to the osteochondrogenic phenotype also occurs in VSMCs during VC. In addition, VC can be regulated by epigenetic factors, including DNA methylation, histone modification, and noncoding RNAs. Although VC is commonly observed in patients with chronic kidney disease and CVD, specific drugs for VC have not been developed. Thus, discovering novel therapeutic targets may be necessary. In this review, we summarize the current experimental evidence regarding the role of epigenetic regulators including histone deacetylases and propose the therapeutic implication of these regulators in the treatment of VC.

Endothelial-to-Mesenchymal Transition in Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) represents a significant threat to cardiovascular health worldwide, and the incidence of this sclerocalcific valve disease has rapidly increased along with a rise in life expectancy. Compelling evidence has suggested that CAVD is an actively and finely regulated pathophysiological process even though it has been referred to as "degenerative" for decades. A striking similarity has been noted in the etiopathogenesis between CAVD and atherosclerosis, a classical proliferative sclerotic vascular disease.1 Nevertheless, pharmaceutical trials that attempted to target inflammation and dyslipidemia have produced disappointing results in CAVD. While senescence is a well-documented risk factor, the sophisticated regulatory networks have not been adequately explored underlying the aberrant calcification and osteogenesis in CAVD. Valvular endothelial cells (VECs), a type of resident effector cells in aortic leaflets, are crucial in maintaining valvular integrity and homeostasis, and dysfunctional VECs are a major contributor to disease initiation and progression. Accumulating evidence suggests that VECs undergo a phenotypic and functional transition to mesenchymal or fibroblast-like cells in CAVD, a process known as the endothelial-to-mesenchymal transition (EndMT) process. The relevance of this transition in CAVD has recently drawn great interest due to its importance in both valve genesis at an embryonic stage and CAVD development at an adult stage. Hence EndMT might be a valuable diagnostic and therapeutic target for disease prevention and treatment. This mini-review summarized the relevant literature that delineates the EndMT process and the underlying regulatory networks involved in CAVD.

The Role of Sclerostin in Bone and Ectopic Calcification

Sclerostin, a 22-kDa glycoprotein that is mainly secreted by the osteocytes, is a soluble inhibitor of canonical Wnt signaling. Therefore, when present at increased concentrations, it leads to an increased bone resorption and decreased bone formation. Serum sclerostin levels are known to be increased in the elderly and in patients with chronic kidney disease. In these patient populations, there is a high incidence of ectopic cardiovascular calcification. These calcifications are strongly associated with cardiovascular morbidity and mortality. Although data are still controversial, it is likely that there is a link between ectopic calcification and serum sclerostin levels. The main question, however, remains whether sclerostin exerts either a protective or deleterious role in the ectopic calcification process.

Lethal giant larvae 1 inhibits smooth muscle calcification via high mobility group box 1

Vascular calcification is a pathological process closely related to atherosclerosis, diabetic vascular diseases, vascular injury, hypertension, chronic kidney disease and aging. Lethal giant larvae 1 (LGL1) is known as a key regulator of cell polarity and plays an important role in tumorigenesis. However, whether LGL1 regulates vascular calcification remains unclear. In this study, we generated smooth muscle-specific LGL1 knockout (LGL1^SMKO) mice by cross-breeding LGL1^flox/flox mice with α-SMA-Cre mice. LGL1 level was significantly decreased during calcifying conditions. Overexpression of LGL1 restrained high phosphate-induced calcification in vascular smooth muscle cells (VSMCs). Mechanically, LGL1 could bind with high mobility group box 1 (HMGB1) and promote its degradation via the lysosomal pathway, thereby inhibiting calcification. Smooth muscle-specific deletion of LGL1 increased HMGB1 level and aggravated vitamin D3-induced vascular calcification, which was attenuated by an HMGB1 inhibitor. LGL1 may inhibit vascular calcification by preventing osteogenic differentiation via promoting HMGB1 degradation.

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.

The Role of Vitamin D in Modulating Mesenchymal Stem Cells and Endothelial Progenitor Cells for Vascular Calcification

Vascular calcification, which involves the deposition of calcifying particles within the arterial wall, is mediated by atherosclerosis, vascular smooth muscle cell osteoblastic changes, adventitial mesenchymal stem cell osteoblastic differentiation, and insufficiency of the calcification inhibitors. Recent observations implied a role for mesenchymal stem cells and endothelial progenitor cells in vascular calcification. Mesenchymal stem cells reside in the bone marrow and the adventitial layer of arteries. Endothelial progenitor cells that originate from the bone marrow are an important mechanism for repairing injured endothelial cells. Mesenchymal stem cells may differentiate osteogenically by inflammation or by specific stimuli, which can activate calcification. However, the bioactive substances secreted from mesenchymal stem cells have been shown to mitigate vascular calcification by suppressing inflammation, bone morphogenetic protein 2, and the Wingless-INT signal. Vitamin D deficiency may contribute to vascular calcification. Vitamin D supplement has been used to modulate the osteoblastic differentiation of mesenchymal stem cells and to lessen vascular injury by stimulating adhesion and migration of endothelial progenitor cells. This narrative review clarifies the role of mesenchymal stem cells and the possible role of vitamin D in the mechanisms of vascular calcification.

Osteocalcin Regulates Arterial Calcification Via Altered Wnt Signaling and Glucose Metabolism

Arterial calcification is an important hallmark of cardiovascular disease and shares many similarities with skeletal mineralization. The bone-specific protein osteocalcin (OCN) is an established marker of vascular smooth muscle cell (VSMC) osteochondrogenic transdifferentiation and a known regulator of glucose metabolism. However, the role of OCN in controlling arterial calcification is unclear. We hypothesized that OCN regulates calcification in VSMCs and sought to identify the underpinning signaling pathways. Immunohistochemistry revealed OCN co-localization with VSMC calcification in human calcified carotid artery plaques. Additionally, 3 mM phosphate treatment stimulated OCN mRNA expression in cultured VSMCs (1.72-fold, p < 0.001). Phosphate-induced calcification was blunted in VSMCs derived from OCN null mice (Ocn ^-/- ) compared with cells derived from wild-type (WT) mice (0.37-fold, p < 0.001). Ocn ^-/- VSMCs showed reduced mRNA expression of the osteogenic marker Runx2 (0.51-fold, p < 0.01) and the sodium-dependent phosphate transporter, PiT1 (0.70-fold, p < 0.001), with an increase in the calcification inhibitor Mgp (1.42-fold, p < 0.05) compared with WT. Ocn ^-/- VSMCs also showed reduced mRNA expression of Axin2 (0.13-fold, p < 0.001) and Cyclin D (0.71 fold, p < 0.01), markers of Wnt signaling. CHIR99021 (GSK3β inhibitor) treatment increased calcium deposition in WT and Ocn ^-/- VSMCs (1 μM, p < 0.001). Ocn ^-/- VSMCs, however, calcified less than WT cells (1 μM; 0.27-fold, p < 0.001). Ocn ^-/- VSMCs showed reduced mRNA expression of Glut1 (0.78-fold, p < 0.001), Hex1 (0.77-fold, p < 0.01), and Pdk4 (0.47-fold, p < 0.001). This was accompanied by reduced glucose uptake (0.38-fold, p < 0.05). Subsequent mitochondrial function assessment revealed increased ATP-linked respiration (1.29-fold, p < 0.05), spare respiratory capacity (1.59-fold, p < 0.01), and maximal respiration (1.52-fold, p < 0.001) in Ocn ^-/- versus WT VSMCs. Together these data suggest that OCN plays a crucial role in arterial calcification mediated by Wnt/β-catenin signaling through reduced maximal respiration. Mitochondrial dynamics may therefore represent a novel therapeutic target for clinical intervention. © 2019 American Society for Bone and Mineral Research.

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.

Melatonin Attenuates β-Glycerophosphate-Induced Calcification of Vascular Smooth Muscle Cells via a Wnt1/β-Catenin Signaling Pathway

Background

Melatonin has been demonstrated to protect against calcification in cyclosporine nephrotoxicity. The wingless-type MMTV integration site family member 1 (Wnt1)/β-catenin pathway is associated with cardiovascular calcification. This study aimed to explore whether melatonin could attenuate VSMC calcification through regulating the Wnt1/β-catenin signaling pathway.

Methods

The effects of melatonin on vascular calcification were investigated in vascular smooth muscle cells (VSMCs). Calcium deposits were visualized by Alizarin Red Staining. Calcium content and alkaline phosphatase (ALP) activity were used to evaluate osteogenic differentiation. Western blots were used to measure the expression of runt-related transcription factor 2 (Runx2), α-smooth muscle actin (α-SMA), and cleaved caspase-3.

Results

Melatonin markedly ameliorated calcium deposition and ALP activity. Runx2 and cleaved caspase-3 were found to be reduced and α-SMA was found to be increased by melatonin, together with a decrease in apoptosis. Immunofluorescence assay revealed a lower Runx2 protein level in the melatonin group. Melatonin treatment significantly decreased the expression of Wnt1 and β-catenin. Treatment with lithium chloride or transglutaminase 2 abrogated the protective effects of melatonin.

Conclusion

Melatonin can attenuate β-GP-induced VSMC calcification through the suppression of Wnt1/β-catenin system.

Wnt1 inhibits vascular smooth muscle cell calcification by promoting ANKH expression

AIMS

Wnt signaling plays a critical role in vascular calcification (VC). Wnt factors induce different physiological and pathological effects on cardiovascular functions. Wnt1, a ligand of Wnt/β-catenin signaling, promotes pro-angiogenesis and reduces myocardial infarction. The role of Wnt1 on VC in chronic kidney disease (CKD) is not fully understood.

METHODS AND RESULTS

We used human vascular smooth muscle cells (VSMCs) and a rat model of chronic renal failure (CRF), and observed a native protective mechanism by which VC is reduced via the activation of Wnt1 and its transcriptional target ANKH inorganic pyrophosphate transport regulator (ANKH) gene. ANKH is an essential calcification inhibitor that effluxes inorganic pyrophosphate (PPi) from VSMCs to play an inhibitory role in VC. Vascular ANKH and plasma PPi were significantly downregulated in the rat model of CRF. The knockdown or inhibition of ANKH reversed the effect of Wnt1 on VC in VSMCs. Clinical analysis revealed low plasma levels of Wnt1 and PPi were associated with CKD in patients. Applying a Wnt/β-catenin signaling agonist can alleviate the progression of VC.

CONCLUSION

This work reveals the ANKH regulation of Wnt1 in VSMCs is essential for blocking VC. Our findings may contribute to the development of medications that target Wnt signaling and/or ANKH to inhibit VC.

Vitamin D-regulated osteocytic sclerostin and BMP2 modulate uremic extraskeletal calcification

We induced chronic kidney disease (CKD) with adenine in WT mice, mice with osteocyte-specific deletion of Cyp27b1, encoding the 25-hydroxyvitamin D 1(OH)ase [Oct-1(OH)ase-/-], and mice with global deletion of Cyp27b1 [global-1α(OH)ase-/-]; we then compared extraskeletal calcification. After adenine treatment, mice displayed increased blood urea nitrogen, decreased serum 1,25(OH)2D, and severe hyperparathyroidism. Skeletal expression of Cyp27b1 and of sclerostin and serum sclerostin all increased in WT mice but not in Oct-1α(OH)ase-/- mice or global-1α(OH)ase-/- mice. In contrast, skeletal expression of BMP2 and serum BMP2 rose in the Oct-1α(OH)ase-/- mice and in the global-1α(OH)ase-/- mice. Extraskeletal calcification occurred in muscle and blood vessels of mice with CKD and was highest in Oct-1α(OH)ase-/-mice. In vitro, recombinant sclerostin (100 ng/mL) significantly suppressed BMP2-induced osteoblastic transdifferentiation of vascular smooth muscle A7r5 cells and diminished BMP2-induced mineralization. Our study provides evidence that local osteocytic production of 1,25(OH)2D stimulates sclerostin and inhibits BMP2 production in murine CKD, thus mitigating osteoblastic transdifferentiation and mineralization of soft tissues. Increased osteocytic 1,25(OH)2D production, triggered by renal malfunction, may represent a "primary defensive response" to protect the organism from ectopic calcification by increasing sclerostin and suppressing BMP2 production.

Dkk (Dickkopf) Proteins

Clinical and preclinical studies over the past 3 decades have uncovered a multitude of signaling pathways involved in the initiation and progression of atherosclerosis. From these studies, signaling by proteins of the Wnt family has recently emerged as an important player in the development of atherosclerosis. Wnt signaling is characterized by a large number of ligands, receptors, and coreceptors and can be regulated at many different levels. Among Wnt modulators, the evolutionary conserved Dkk (Dickkopf) proteins, and especially Dkk-1, the founding member of the family, are the best characterized. The role of Dkks in the pathophysiology of the arterial wall is only partially understood, but their involvement in atherosclerosis is becoming increasingly evident. This review introduces recent key findings on Dkk proteins and their functions in atherosclerosis and discusses the potential importance of modulating Dkk signaling as part of a novel, improved strategy for preventing and treating atherosclerosis-related diseases.

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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.

Correlation between sclerostin and Dickkopf-1 with aortic arterial stiffness in patients with type 2 diabetes: A prospective, cross-sectional study

BACKGROUND

Sclerostin and Dickkopf-1 are extracellular inhibitors of the canonical Wnt/β-catenin signalling pathway, which is implicated in the development of arterial stiffness. However, the correlation between aortic stiffness and sclerostin or Dickkopf-1 levels in patients with type 2 diabetes mellitus is unknown.

METHODS

Fasting blood samples were collected from 125 patients with type 2 diabetes mellitus. Aortic stiffness was measured by carotid-femoral pulse wave velocity, and high aortic stiffness was defined by a carotid-femoral pulse wave velocity of >10 m/s. The serum sclerostin and Dickkopf-1 concentrations were determined using commercially available enzyme-linked immunosorbent assays.

RESULTS

In total, 46 patients with type 2 diabetes mellitus (36.8%) had high levels of aortic stiffness. Compared to the control group without aortic stiffness, this group was significantly older, had higher systolic and diastolic blood pressures, had higher blood urea nitrogen, creatinine, urinary albumin-to-creatinine ratio and serum sclerostin levels, and had significantly lower high-density lipoprotein cholesterol levels and estimated glomerular filtration rates. After adjusting for confounders, serum sclerostin [odds ratio = 1.005 (1.002-1.007), p = 0.002] levels remained an independent predictor of aortic stiffness. Multivariate analysis showed that the serum sclerostin level ( β = 0.374, adjusted R² change = 0.221, p < 0.001) was positively associated with carotid-femoral pulse wave velocity.

CONCLUSION

Serum levels of sclerostin, but not Dickkopf-1, are positively correlated with carotid-femoral pulse wave velocity and independently predict aortic stiffness in patients with type 2 diabetes mellitus.

Long noncoding RNAs in vascular smooth muscle cells regulate vascular calcification

Vascular calcification is characterized by the accumulation of hydroxyapatite crystals, which is a result of aberrant mineral metabolism. Although many clinical studies have reported its adverse effects on cardiovascular morbidity, the molecular mechanism of vascular calcification, especially the involvement of long noncoding RNAs (lncRNAs), is not yet reported. From the transcriptomic analysis, we discovered hundreds of lncRNAs differentially expressed in rat vascular smooth muscle cells (VSMCs) treated with inorganic phosphate, which mimics vascular calcification. We focused on Lrrc75a-as1 and elucidated its transcript structure and confirmed its cytoplasmic localization. Our results showed that calcium deposition was elevated after knockdown of Lrrc75a-as1, while its overexpression inhibited calcium accumulation in A10 cells. In addition, Lrrc75a-as1 attenuated VSMCs calcification by decreasing the expression of osteoblast-related factors. These findings suggest that Lrrc75a-as1 acts as a negative regulator of vascular calcification, and may serve as a possible therapeutic target in vascular calcification.

The Emerging Role of Mesenchymal Stem Cells in Vascular Calcification

Vascular calcification (VC), characterized by hydroxyapatite crystal depositing in the vessel wall, is a common pathological condition shared by many chronic diseases and an independent risk factor for cardiovascular events. Recently, VC is regarded as an active, dynamic cell-mediated process, during which calcifying cell transition is critical. Mesenchymal stem cells (MSCs), with a multidirectional differentiation ability and great potential for clinical application, play a duplex role in the VC process. MSCs facilitate VC mainly through osteogenic transformation and apoptosis. Meanwhile, several studies have reported the protective role of MSCs. Anti-inflammation, blockade of the BMP2 signal, downregulation of the Wnt signal, and antiapoptosis through paracrine signaling are possible mechanisms. This review displays the evidence both on the facilitating role and on the protective role of MSCs, then discusses the key factors determining this divergence.

Ghrelin combined with sodium tanshinone IIA sulfonate pretreatment reduces apoptosis and fractalkine expression induced by high-dose glucose in human umbilical vein endothelial cells

BACKGROUND

To explore the regulatory role of ghrelin combined with sodium tanshinone IIA sulfonate (STS) pretreatment in cell apoptosis and fractalkine (FKN) expression of human umbilical vein endothelial cells (HUVECs) induced with high-dose glucose.

METHODS

HUVECs were assigned into control group, high-dose glucose group (HG group), high-dose glucose with ghrelin group (Gr+HG group), and high-dose glucose companied with ghrelin and STS group (Gr+STS+HG group). The apoptosis of HUVECs was determined by Hoechst 33258 straining and flow cytometry (FCM). Nitric oxide (NO) level was measured by total NO assay kit. The mRNA and protein levels of β-catenin, p-GSK-3β and FKN were accessed by Western blot and real-time quantitative polymerase chain reaction (RT-qPCR), respectively.

RESULTS

High-dose glucose significantly accelerated apoptosis in HUVECs. The apoptotic rate was lower in Gr+HG group and much lower in Gr+STS+HG group than control group. NO level was significantly reduced in the HG group, which was partly inhibited in Gr+HG group and obviously increased in Gr+STS+HG group than controls. In addition, mRNA levels of GSK-3β and FKN in HUVECs decreased in Gr+HG group, which was more obviously decreased in Gr+STS+HG group. However, ghrelin treatment upregulated β-catenin and p-GSK-3β (Ser9), but downregulated FKN during high-dose glucose treatment, which was more obvious in Gr+STS+HG group.

CONCLUSIONS

Pretreatment of ghrelin combined with STS reduces the apoptosis rate of HUVECs induced by high glucose environment and inhibits the expression of FKN via β-catenin/Wnt signaling pathway.

Calcification: A Disregarded or Ignored Issue in the Gynecologic Tumor Microenvironments

Although calcification in the gynecologic tumor microenvironments is a common phenomenon, doctors and researchers still disregard or ignore the issue. In fact, this change in the gynecologic tumor microenvironments is clinically significant and a number of studies have reported an association between calcification and gynecological tumor progression. In ovarian cancer, calcification is predominantly psammomatous and largely occurs in serous papillary ovarian tumors. In addition, calcification in ovarian cancer correlated with lower histologic grade and may indicate a poorer survival rate. In uterine fibroids, calcification occurs as a degenerative change and is predictive of a good prognosis. As for endometrial cancer and cervical cancer, calcification rarely occurs in these cancers. The mechanism of calcification in the gynecologic tumor microenvironments is not currently clear. One theory is that calcification occurs due to degeneration of the tumor cells; another theory is that calcification occurs in response to secretions from cells in the tumor microenvironment. Although previous studies have revealed a direct association between calcifications and gynecological tumors, this association has not been fully clarified. To better clarify the significance of calcification in terms of diagnosing and treating gynecological tumors, the associations between calcification and the different histologic stages and prognosis in gynecological tumors should be further studied. In particular, more attention should be paid to the morphological characteristics, chemical nature, and mechanism of calcifications in the gynecological tumor microenvironments.

Deletion of Dicer blocks osteogenic differentiation via the inhibition of Wnt signalling

Micro (mi)RNAs are small, non‑coding RNAs and have been reported to have important roles in the epigenetic control of bone development. miRNAs markedly regulate osteoblast differentiation through stages of maturation as well as the activities of osteogenic signaling pathways. Dicer is an important endoribonuclease that regulates miRNA maturation. Previous studies have demonstrated that Dicer deletion decreases fetal survival and bone formation, while excision in differentiated osteoblasts increases bone mass. However, the underlying molecular mechanisms remain unclear. In the present study, whether the deletion of Dicer affects Wnt signaling, which exhibits important roles during osteogenesis, was investigated. Bone marrow stromal cells (BMSCs) were used as an osteogenic model. Dynamic changes of seven Wnt genes and downstream T‑cell factor 1 (Tcf‑1)/lymphoid enhancing binding factor were observed during the osteogenic differentiation of BMSCs, which revealed different roles at early and late differentiation stages. Following the stable knockdown of Dicer in BMSCs using lentiviral short hairpin RNA, osteogenic differentiation was blocked, and the levels of important osteogenic differentiation markers (runt related transcription factor 2 and alkaline phosphatase) were markedly inhibited. Furthermore, stage specific regulation of Wnt genes in Dicer‑deficient BMSCs was investigated in the present study. At the early differentiation stage (days 5‑7), knockdown of Dicer led to the inhibition of Wnt1, Wnt7 and Wnt10b, as well as the upregulation of Wnt4, Wnt10a and Tcf‑1. At the late stage of differentiation (days 14‑21), knockdown of Dicer significantly suppressed the expression levels of all of the included Wnt genes as well as Tcf‑1, with the exception of Wnt10a. The upregulation of Wnt10a following the deletion of Dicer was maintained throughout all stages of differentiation. In addition, differential regulation of Wnt genes and Tcf‑1 were revealed to be associated with dynamic changes in their expression levels during osteogenic differentiation. Furthermore, the four putative Wnt10a‑targeting miRNAs were investigated in the present study, and the results demonstrated that they were upregulated during osteogenic differentiation, which suggested that inhibition of Wnt10a may be an important factor associated with osteogenic differentiation. In conclusion, the present study investigated the mechanism underlying the regulation of Wnt signalling by Dicer during osteogenesis, and identified potential miRNAs targeting the components of Wnt signalling influenced by Dicer. Collectively, the present study identified the association between Dicer and Wnt signalling during bone development.

Thoracic aortic calcification across the clinical dysglycemic continuum in a large Asian population free of cardiovascular symptoms

Thoracic aortic calcification (TAC) is tightly linked to pathological atherosclerosis and associated with certain cardiovascular diseases. While diabetes mellitus (DM) is known as a coronary heart disease equivalent, we examined the presence of TAC across the dysglycemic spectrum of diabetes mellitus (DM). We consecutively studied 3003 asymptomatic ethnic Asians underwent annual cardiovacular health survey, and further categorized them into: 1) 1760 normo-glycemic, 2) 968 pre-diabetic, and 3) 274 overt DM based on dysglycemic indices and medical histories. Several TAC parameters were assessed using non-contrast multi-detector computed tomography (MDCT), and related to dysglycemic indices or diabetes mellitus status. A remarkably graded increases of adjusted total TAC calcium burden, volume and density were seen across Non-diabetes, Pre-diabetes, and diabetes mellitus categories and positively correlated with all dysglycemic profiles (all p<0.001). Multi-variate logistic and linear regression models demonstrated independent associations between greater TAC density and all dysglycemic indices (Coef: 2.5, 1.4, 6.8 for fasting, postprandial sugar and HbA1c) and diabetes mellitus status (all p<0.05). Furthermore, Receiver-operating characteristic curves (ROC) showed fasting sugar and postprandial sugar set at 103mg/dL and 111mg/dL, separately, with HbA1c set at 5.8% all predict the presence of aortic calcification. Dysglycemic status, even without overt diabetes mellitus, were tighly linked to subclinical, pathological thoracic aortic calcification.

The Interplay of SIRT1 and Wnt Signaling in Vascular Calcification

Vascular calcification is a major health risk and is highly correlated with atherosclerosis, diabetes, and chronic kidney disease. The development of vascular calcification is an active and complex process linked with a multitude of signaling pathways, which regulate promoters and inhibitors of osteogenesis, the balance of which become deregulated in disease conditions. SIRT1, a protein deacetylase, known to be protective in inhibiting oxidative stress and inflammation within the vessel wall, has been shown as a possible key player in modulating the cell-fate determining canonical Wnt signaling pathways. Suppression of SIRT1 has been reported in patients suffering with cardiovascular pathologies, suggesting that the sustained acetylation of osteogenic factors could contribute to their activation and in turn, lead to the progression of calcification. There is clear evidence of the synergy between β-Catenin and elevated Runx2, and with Wnt signaling being β-Catenin dependent, further understanding is needed as to how these molecular pathways converge and interact, in order to provide novel insight into the mechanism by which smooth muscle cells switch to an osteogenic differentiation programme. Therefore, this review will describe the current concepts of pathological soft tissue mineralization, with a focus on the contribution of SIRT1 as a regulator of Wnt signaling and its targets, discussing SIRT1 as a potential target for manipulation and therapy.

SIRT7 Regulates the Vascular Smooth Muscle Cells Proliferation and Migration via Wnt/β-Catenin Signaling Pathway

A huge amount of evidence indicates that sirtuin 7 (SIRT7), a key mediator of many cellular activities, plays a crucial role in the pathogenesis of various diseases. However, little is known about the role of SIRT7 in atherosclerosis. This study investigated the potential role of SIRT7 in regulating the proliferation and migration of human vascular smooth muscle cells (HAVSMCs) and its possible molecular mechanism. In this study, human vascular smooth muscle cells (HAVSMCs) were induced by oxidized low-density lipoprotein (ox-LDL) to establish atherosclerosis (AS) cell model. Immunofluorescence staining and Western blot were used to detect the level of α-SMA expression, which was a marker protein in AS. In addition, RT-qPCR and Western blot assay were applied for exploring the mRNA and protein expression levels of SIRT7, Wnt, β-catenin, and cyclin D1 after knockdown or overexpression of SIRT7. And, furthermore, Cell Counting Kit-8 assay, flow cytometry, and wound-healing assay were used to assess HAVSMCs proliferation, cell cycle, and migration. Dickkopf-1 (DKK-1), a secretory glycoprotein that can block Wnt/β-catenin pathway, was used in SIRT7 overexpression HAVSMCs; subsequently cells proliferation and migration were assessed by Cell Counting Kit-8 assay, flow cytometry analysis, and wound-healing assay. We found that knockdown of SIRT7 significantly promoted cell proliferation and migration, decreased the percentages of cells in the G1 and G2 phases, and increased those in the S phase and downregulated the protein expression levels of Wnt, β-catenin, and cyclin D1, while overexpression of SIRT7 had reverse results. After treatment with Wnt/beta-catenin pathway inhibitor DKK-1 in SIRT7 overexpression HAVSMCs, cell proliferation and migration were increased, respectively. In conclusion, SIRT7 inhibited HAVSMCs proliferation and migration via enhancing Wnt/β-catenin activation, which provided a novel therapeutic strategy for antiatherosclerosis.

S100/RAGE-Mediated Inflammation and Modified Cholesterol Lipoproteins as Mediators of Osteoblastic Differentiation of Vascular Smooth Muscle Cells

Arterial calcification is a feature of atherosclerosis and shares many risk factors including diabetes, dyslipidemia, chronic kidney disease, hypertension, and age. Although there is overlap in risk factors, anti-atherosclerotic therapies, including statins, fail to reduce arterial, and aortic valve calcifications. This suggests that low density lipoprotein (LDL) may not be the main driver for aortic valve disease and arterial calcification. This review focuses on modified LDLs and their role in mediating foam cell formation in smooth muscle cells (SMCs), with special emphasis on enzyme modified non-oxidized LDL (ELDL). In vivo, ELDL represents one of the many forms of modified LDLs present in the atherosclerotic vessel. Phenotypic changes of macrophages and SMCs brought about by the uptake of modified LDLs overlap significantly in an atherosclerotic milieu, making it practically impossible to differentiate between the effects from oxidized LDL, ELDL, and other LDL modification. By studying in vitro-generated modifications of LDL, we were able to demonstrate marked differences in the transcriptome of human coronary artery SMCs (HCASMCs) upon uptake of ELDL, OxLDL, and native LDL, indicating that specific modifications of LDL in atherosclerotic plaques may determine the biology and functional consequences in vasculature. Enzyme-modified non-oxidized LDL (ELDL) induces calcification of SMCs and this is associated with reduced mRNA levels for genes protective for calcification (ENPP1, MGP) and upregulation of osteoblastic genes. A second focus of this review is on the synergy between hyperlipidemia and accelerated calcification In vivo in a mouse models with transgenic expression of human S100A12. We summarize mechanisms of S100A12/RAGE mediated vascular inflammation promoting vascular and valve calcification in vivo.

Serum sclerostin and irisin as predictive markers for atherosclerosis in Egyptian type II diabetic female patients: A case control study

Diabetes mellitus represents a major independent risk factor for developing fatal cardiovascular diseases (CVDs) presumably through accelerating atherosclerosis; the underlying cause of most CVDs. Notably, this relative risk is reported to be higher in women than men. Endeavors directed towards identifying novel reliable predictive biomarkers are immensely thereby urged to improve the long-term outcome in these diabetic female patients. Sclerostin (SOST) is a Wnt signaling antagonist whereas irisin is a muscle-derived factor released after exercising which enhances browning of white adipose tissue. Emerging lines of evidence hint at potential crosstalk between them and CVDs. The present study aimed to assess the serum levels of SOST and irisin in Egyptian type 2 diabetic (T2DM) female patients with and without atherosclerosis and explore the possible relationship between both markers and other studied parameters among the studied cohorts. In this case-control study, 69 female subjects were enrolled; 39 type 2 diabetes patients with atherosclerosis (T2DM+ATHR), 22 type 2 diabetes patients without atherosclerosis (T2DM-ATHR) and 8 healthy controls. Their serum levels of SOST and irisin were assessed using ELISA. Significant increase in SOST levels were found in T2DM+ATHR compared to T2DM-ATHR and control (259.9 ±17.98 vs. 165.8±13.12 and 142.0±13.31 pg/mL respectively, P<0.001). Conversely, irisin levels were significantly lower in T2DM+ATHR (P<0.001) and T2DM-ATHR (P<0.01) compared to the control group (32.91±2.545 and 58.55±13.19 vs. 473.6±112.7 pg/mL). Interestingly, significant correlations between the levels of SOST and both irisin and fasting blood glucose were noticed in T2DM+ATHR group (r = 0.3754 and 0.3381 respectively, P<0.05). In conclusion, to the best of our knowledge, this study is the first to demonstrate the correlation between SOST and irisin levels in atherosclerotic T2DM female patients implying their potential implication in diabetic cardiovascular pathophysiology and supporting their use as reliable diagnostic/prognostic biomarkers for monitoring and preventing CVDs progression of T2DM female patients.

Genome-wide association analysis of common genetic variants of resistant hypertension

Resistant hypertension (RHTN), defined as uncontrolled blood pressure (BP) ≥ 140/90 using three or more drugs or controlled BP (<140/90) using four or more drugs, is associated with adverse outcomes, including decline in kidney function. We conducted a genome-wide association analysis in 1194 White and Hispanic participants with hypertension and coronary artery disease from the INternational VErapamil-SR Trandolapril STudy-GENEtic Substudy (INVEST-GENES). Top variants associated with RHTN at p < 10^-4 were tested for replication in 585 White and Hispanic participants with hypertension and subcortical strokes from the Secondary Prevention of Subcortical Strokes GENEtic Substudy (SPS3-GENES). A genetic risk score for RHTN was created by summing the risk alleles of replicated RHTN signals. rs11749255 in MSX2 was associated with RHTN in INVEST (odds ratio (OR) (95% CI) = 1.50 (1.2-1.8), p = 7.3 × 10^-5) and replicated in SPS3 (OR = 2.0 (1.4-2.8), p = 4.3 × 10^-5), with genome-wide significance in meta-analysis (OR = 1.60 (1.3-1.9), p = 3.8 × 10^-8). Other replicated signals were in IFLTD1 and PTPRD. IFLTD1 rs6487504 was associated with RHTN in INVEST (OR = 1.90 (1.4-2.5), p = 1.1 × 10^-5) and SPS3 (OR = 1.70 (1.2-2.5), p = 4 × 10^-3). PTPRD rs324498, a previously reported RHTN signal, was among the top signals in INVEST (OR = 1.60 (1.3-2.0), p = 3.4 × 10^-5) and replicated in SPS3 (OR = 1.60 (1.1-2.4), one-sided p = 0.005). Participants with the highest number of risk alleles were at increased risk of RHTN compared to participants with a lower number (p-trend = 1.8 × 10^-15). Overall, we identified and replicated associations with RHTN in the MSX2, IFLTD1, and PTPRD regions, and combined these associations to create a genetic risk score.

Role of PKB/SGK-dependent phosphorylation of GSK-3α/β in vascular calcification during cholecalciferol overload in mice

Medial vascular calcification is a highly regulated process involving osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells. Both, protein kinase B (PKB) and serum- and glucocorticoid-inducible kinase 1 (SGK1) are involved in the intracellular signaling of vascular calcification and both phosphorylate and inactivate glycogen synthase kinase 3 (GSK-3). The present study explored whether PKB/SGK-dependent phosphorylation of GSK-3α/β is involved in vascular calcification. Experiments were performed in Gsk-3α/β double knockin mice lacking functional PKB/SGK phosphorylation sites (gsk-3^KI) and corresponding wild-type mice (gsk-3^WT) following high-dosed cholecalciferol treatment as well as ex vivo in aortic ring explants from gsk-3^KI and gsk-3^WT mice treated without and with phosphate. In gsk-3^WT mice, high-dosed cholecalciferol induced vascular calcification and aortic osteo-/chondrogenic signaling, shown by increased expression of osteogenic markers Msx2, Cbfa1 and tissue-nonspecific alkaline phosphatase (Alpl). All these effects were suppressed in aortic tissue from gsk-3^KI mice. Cholecalciferol decreased aortic Gsk-3α/β phosphorylation (Ser^21/9) in gsk-3^WT mice, while no phosphorylation was observed in gsk-3^KI mice. Moreover, the mRNA expression of type III sodium-dependent phosphate transporter (Pit1) and plasminogen activator inhibitor 1 (Pai1) was increased following cholecalciferol treatment in aortic tissue of gsk-3^WT mice, effects again blunted in gsk-3^KI mice. In addition, phosphate treatment induced mineral deposition and osteogenic markers expression in aortic ring explants from gsk-3^WT mice, effects reduced in aortic ring explants from gsk-3^KI mice. In conclusion, vascular PKB/SGK-dependent phosphorylation of GSK-3α/β contributes to the osteoinductive signaling leading to vascular calcification.

BMP-2 induces human mononuclear cell chemotaxis and adhesion and modulates monocyte-to-macrophage differentiation

Type 2 diabetes mellitus (T2DM) is a cardiovascular risk factor which leads to atherosclerosis, an inflammatory disease characterized by the infiltration of mononuclear cells in the vessel. Bone morphogenetic protein (BMP)‐2 is a cytokine which has been recently shown to be elevated in atherosclerosis and T2DM and to contribute to vascular inflammation. However, the role of BMP‐2 in the regulation of mononuclear cell function remains to be established. Herein, we demonstrate that BMP‐2 induced human monocyte chemotaxis via phosphoinositide 3 kinase and mitogen‐activated protein kinases. Inhibition of endogenous BMP‐2 signalling, by Noggin or a BMP receptor inhibitor, interfered with monocyte migration. Although BMP‐2 expression was increased in monocytes from T2DM patients, it could still stimulate their migration. Furthermore, BMP‐2 interfered with their differentiation into M2 macrophages. Finally, BMP‐2 both induced the adhesion of monocytes to fibronectin and endothelial cells (ECs), and promoted the adhesive properties of ECs, by increasing expression of adhesion and pro‐inflammatory molecules. Our data demonstrate that BMP‐2 could exert its pro‐inflammatory effects by inducing monocyte migration and adhesiveness to ECs and by interfering with the monocyte differentiation into M2 macrophages. Our findings provide novel insights into the mechanisms by which BMP‐2 may contribute to the development of atherosclerosis.

ER stress regulates alkaline phosphatase gene expression in vascular smooth muscle cells via an ATF4-dependent mechanism

OBJECTIVE

Vascular calcification is the deposition of hydroxyapatite crystals in the blood vessel wall. Osteogenic differentiation of vascular smooth muscle cells (VSMCs) plays a key role in this process. Increased expression of alkaline phosphatase (ALP) occurs in some in vitro models of VSMC calcification and is thought to be crucial for mineralization, however, little is known about the transcriptional regulation of ALP in VSMCs. Recently, ALP upregulation was shown to coincide with endoplasmic reticulum (ER) stress-mediated vascular calcification, specifically with expression of the transcription factor ATF4. As no direct links between ALP expression and ER stress have previously been demonstrated in VSMCs, the aim of this study was to investigate whether ATF4 interacts directly with the ALP promoter.

RESULTS

The present study shows that ALP mRNA and activity were significantly increased by ER stress treatment of human primary VSMCs in vitro and that this was ATF4-dependent. Bioinformatics analysis predicted two ATF4 binding sites in ER-stress responsive regions of the ALP promoter (- 3631 to - 2048 bp from the first intron). However, we found that ATF4 does not bind within this fragment of the ALP promoter region.

High Mobility Group Box 1 Promotes Aortic Calcification in Chronic Kidney Disease via the Wnt/β-Catenin Pathway

Vascular calcification (VC) is common in chronic kidney disease (CKD), where cardiovascular mortality remains the leading cause of death. Here, we examined the role of high-mobility group box1 (HMGB1), a nuclear DNA-binding protein involved in inflammation, in aortic calcification and renal dysfunction induced by high phosphate in a mouse model of CKD induced by 5/6 nephrectomy. HMGB1 and kidney function markers were measured by ELISA in the serum of CKD patients and in CKD mice. Sections of the aortas of mice were analyzed by immunofluorescence and Alizarin red staining, and protein lysates were generated to analyze the expression of related proteins in response to silencing of HMGB1 or β-catenin by western blotting. Our results showed that serum HMGB1 levels were significantly higher in CKD patients than in healthy controls and related to disease stage. High phosphate promoted the translocation of HMGB1 from the nucleus to the cytosol and aortic calcification in CKD mice in vivo, whereas HMGB1 knockdown ameliorated part of renal and vascular function. β-catenin silencing reversed high phosphate-induced calcification and restored renal marker levels. Taken together, our results suggest that HMGB1 is involved in VC associated with CKD via a mechanism involving the β-catenin.

DKK1 and Kremen Expression Predicts the Osteoblastic Response to Bone Metastasis

Bone metastasis is a complication of advanced breast and prostate cancer. Tumor-secreted Dickkopf homolog 1 (DKK1), an inhibitor of canonical Wnt signaling and osteoblast differentiation, was proposed to regulate the osteoblastic response to metastatic cancer in bone. The objectives of this study were to compare DKK1 expression with the in vivo osteoblastic response in a panel of breast and prostate cancer cell lines, and to discover mechanisms that regulate cancer DKK1 expression. DKK1 expression was highest in MDA-MB-231 and PC3 cells that produce osteolytic lesions, and hence a suppressed osteoblastic response, in animal models of bone metastasis. LnCaP, C4-2B, LuCaP23.1, T47D, ZR-75-1, MCF-7, ARCaP and ARCaP_M cancer cells that generate osteoblastic, mixed or no bone lesions had the lowest DKK1 expression. The cell lines with negligible expression, LnCaP, C4-2B and T47D, exhibited methylation of the DKK1 promoter. Canonical Wnt signaling activity was then determined and found in all cell lines tested, even in the MDA-MB-231 and PC3 cell lines despite sizeable amounts of DKK1 protein expression expected to block canonical Wnt signaling. A mechanism of DKK1 resistance in the osteolytic cell lines was investigated and determined to be at least partially due to down-regulation of the DKK1 receptors Kremen1 and Kremen2 in the MDA-MB-231 and PC3 cell lines. Combined DKK1 and Kremen expression in cancer cells may serve as predictive markers of the osteoblastic response of breast and prostate cancer bone metastasis.

Is Sclerostin Level Associated with Cardiovascular Diseases in Hemodialysis Patients?

BACKGROUND/AIMS

The objective of this study is to evaluate the relation between sclerostin, arterial stiffness, and cardiovascular events (CVE) in hemodialysis patients (HD).

METHODS

Sclerostin level and carotid-femoral pulse wave velocity (PWV) in 97 HD patients and sclerostin level in 40 controls were measured.

RESULTS

Sclerostin level was significantly higher in patients than in controls. Sclerostin associated positively with age, male gender, cardiovascular disease, statin use, BMI, and PWV while negatively with alkaline phosphatase, parathormone (PTH), Kt/V, cinacalcet and vitamin D use in univariable correlation analyses. Sclerostin associated positively with male gender and statin use but negatively with PTH in multivariate regression analyses. During observation, 30 fatal or nonfatal CVEs were observed. While univariate correlation analysis showed a positive association between PWV and sclerostin, there was no relation between the two in multivariate regression analysis.

CONCLUSION

Further studies are needed to understand the role of sclerostin in predicting PWV changes in HD patients.

A GTPase-activating protein-binding protein (G3BP1)/antiviral protein relay conveys arteriosclerotic Wnt signals in aortic smooth muscle cells

In aortic vascular smooth muscle (VSM), the canonical Wnt receptor LRP6 inhibits protein arginine (Arg) methylation, a new component of noncanonical Wnt signaling that stimulates nuclear factor of activated T cells (viz NFATc4). To better understand how methylation mediates these actions, MS was performed on VSM cell extracts from control and LRP6-deficient mice. LRP6-dependent Arg methylation was regulated on >500 proteins; only 21 exhibited increased monomethylation (MMA) with concomitant reductions in dimethylation. G3BP1, a known regulator of arteriosclerosis, exhibited a >30-fold increase in MMA in its C-terminal domain. Co-transfection studies confirm that G3BP1 (G3BP is Ras-GAP SH3 domain-binding protein) methylation is inhibited by LRP6 and that G3BP1 stimulates NFATc4 transcription. NFATc4 association with VSM osteopontin (OPN) and alkaline phosphatase (TNAP) chromatin was increased with LRP6 deficiency and reduced with G3BP1 deficiency. G3BP1 activation of NFATc4 mapped to G3BP1 domains supporting interactions with RIG-I (retinoic acid inducible gene I), a stimulus for mitochondrial antiviral signaling (MAVS) that drives cardiovascular calcification in humans when mutated in Singleton-Merten syndrome (SGMRT2). Gain-of-function SGMRT2/RIG-I mutants increased G3BP1 methylation and synergized with osteogenic transcription factors (Runx2 and NFATc4). A chemical antagonist of G3BP, C108 (C108 is 2-hydroxybenzoic acid, 2-[1-(2-hydroxyphenyl)ethylidene]hydrazide CAS 15533-09-2), down-regulated RIG-I-stimulated G3BP1 methylation, Wnt/NFAT signaling, VSM TNAP activity, and calcification. G3BP1 deficiency reduced RIG-I protein levels and VSM osteogenic programs. Like G3BP1 and RIG-I deficiency, MAVS deficiency reduced VSM osteogenic signals, including TNAP activity and Wnt5-dependent nuclear NFATc4 levels. Aortic calcium accumulation is decreased in MAVS-deficient LDLR^-/- mice fed arteriosclerotic diets. The G3BP1/RIG-I/MAVS relay is a component of Wnt signaling. Targeting this relay may help mitigate arteriosclerosis.

Vascular ossification: Pathology, mechanisms, and clinical implications

In recent years, the mechanisms and clinical significance of vascular calcification have been increasingly investigated. For over a century, however, pathologists have recognized that vascular calcification is a form of heterotopic ossification. In this review, we aim to describe the pathology and molecular processes of vascular ossification, to characterize its clinical significance and treatment options, and to elucidate areas that require further investigation. The molecular mechanisms of vascular ossification involve the activation of regulators including bone morphogenic proteins and chondrogenic transcription factors and the loss of mineralization inhibitors like fetuin-A and pyrophosphate. Although few studies have examined the gross pathology of vascular ossification, the presence of these molecular regulators and evidence of microfractures and cartilage have been demonstrated on heart valves and atherosclerotic plaques. These changes are often triggered by common inflammatory and metabolic disorders like diabetes, hyperlipidemia, and chronic kidney disease. The increasing prevalence of these diseases warrants further research into the clinical significance of vascular ossification and future treatment options.

Circulating Wnt inhibitory factor 1 levels are associated with development of cardiovascular disease

BACKGROUND AND AIMS

Wnt signaling is involved in atherosclerotic plaque formation directly and indirectly by modulating cardiovascular risk factors. We investigated whether circulating concentrations of Wnt inhibitors are associated with cardiovascular events in subjects with intermediate cardiovascular risk.

METHODS

904 non-diabetic subjects participating in the SAPHIR study were assessed. In the SAPHIR study, middle-aged women without overt atherosclerotic disease at study entry were followed up for 10 years. 88 patients of our study cohort developed cardiovascular disease at follow-up (CVD group). Subjects of the CVD group were 1:2 case-control matched for age, sex, BMI and smoking behavior with subjects without overt cardiovascular disease after a 10 year-follow-up (control group). 18 patients of the CVD group and 19 subjects of the control group were retrospectively excluded due to fulfilling exclusion criteria. Baseline circulating sclerostin, dickkopf (DKK)-1, secreted frizzled-related protein (SFRP)-1 and Wnt inhibitory factor (WIF)-1 levels were assessed by ELISA.

RESULTS

Baseline systemic SFRP-1 and WIF-1 levels were significantly higher in patients with cardiovascular events (n = 70) when compared to healthy controls (n = 157) while DKK-1 and sclerostin levels were similar in both groups. Logistic regression analysis revealed WIF-1 as a significant predictor of future cardiovascular events.

CONCLUSIONS

Our data suggest that increased SFRP-1 and WIF-1 levels precede the development of symptomatic atherosclerotic disease. Assessment of systemic WIF-1 levels, which turned out to be independently associated with CVD, might help to early identify patients at intermediate cardiovascular risk.

Osteocardiology: Defining the Go/No-Go Time Point for Therapy

Recent epidemiological studies have revealed that the risk factors associated with coronary artery calcification (CAC), including male gender, smoking, hypertension, and elevated serum cholesterol, are similar to the risk factors associated with the development of calcific aortic valve disease (CAVD). The results of the experimental and clinical studies demonstrate that traditional risk factors initiate early atherosclerosis which over time differentiates to form bone in the heart causing clinical CAC and CAVD. Understanding the cellular mechanisms of cardiovascular calcification, the end-stage process of the atherosclerosis will help define the specific time point to modify this cellular process of bone formation in the heart termed osteocardiology. This time point between subclinical atherosclerosis and clinical calcification is the go/no-go time point, or the point of no return with severe clinical calcification in the heart. This review will summarize the development of bone formation in the heart termed osteocardiology, to define the go/no-go time point for therapy initiation to slow the progression of cardiovascular calcification.

Therapeutic Interference With Vascular Calcification-Lessons From Klotho-Hypomorphic Mice and Beyond

Medial vascular calcification, a major pathophysiological process associated with cardiovascular disease and mortality, involves osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). In chronic kidney disease (CKD), osteo-/chondrogenic transdifferentiation of VSMCs and, thus, vascular calcification is mainly driven by hyperphosphatemia, resulting from impaired elimination of phosphate by the diseased kidneys. Hyperphosphatemia with subsequent vascular calcification is a hallmark of klotho-hypomorphic mice, which are characterized by rapid development of multiple age-related disorders and early death. In those animals, hyperphosphatemia results from unrestrained formation of 1,25(OH)₂D₃ with subsequent retention of calcium and phosphate. Analysis of klotho-hypomorphic mice and mice with vitamin D₃ overload uncovered several pathophysiological mechanisms participating in the orchestration of vascular calcification and several therapeutic opportunities to delay or even halt vascular calcification. The present brief review addresses the beneficial effects of bicarbonate, carbonic anhydrase inhibition, magnesium supplementation, mineralocorticoid receptor (MR) blockage, and ammonium salts. The case is made that bicarbonate is mainly effective by decreasing intestinal phosphate absorption, and that carbonic anhydrase inhibition leads to metabolic acidosis, which counteracts calcium-phosphate precipitation and VSMC transdifferentiation. Magnesium supplementation, MR blockage and ammonium salts are mainly effective by interference with osteo-/chondrogenic signaling in VSMCs. It should be pointed out that the, by far, most efficient substances are ammonium salts, which may virtually prevent vascular calcification. Future research will probably uncover further therapeutic options and, most importantly, reveal whether these observations in mice can be translated into treatment of patients suffering from vascular calcification, such as patients with CKD.

Mechanisms of aortic stenosis

The pathobiology of degenerative aortic valve stenosis (AS) is complex and involves multiple features such as fibrosis, inflammation, oxidative stress, angiogenesis, hemorrhage, and osteogenic differentiation. We summarize the mechanism of valve calcification and angiogenesis which is necessary for calcifying processes. A promising therapeutic target is nuclear factor (NF)-κB which activates bone morphogenetic protein (BMP)2 via interleukin-6. BMP2 activates Wnt signaling via msh homeobox 2 causing osteogenic differentiation. BMP2 also activates Runx2/Cbfa1 which is an osteoblast-specific transcription factor. Signals in the hypoxia-inducible factor-2 axis activated by the NF-κB signaling pathway also play important role in calcifying processes including angiogenesis. The reason why angiogenesis takes place in avascular valves is still unknown, but it is likely angiogenesis and angiogenesis-related hemorrhage play critical roles in the progression of AS.

Sclerostin: an Emerging Target for the Treatment of Cancer-Induced Bone Disease

PURPOSE OF REVIEW

This review provides a summary of the current knowledge on Sost/sclerostin in cancers targeting the bone, discusses novel observations regarding its potential as a therapeutic approach to treat cancer-induced bone loss, and proposes future research needed to fully understand the potential of therapeutic approaches that modulate sclerostin function.

RECENT FINDINGS

Accumulating evidence shows that sclerostin expression is dysregulated in a number of cancers that target the bone. Further, new findings demonstrate that pharmacological inhibition of sclerostin in preclinical models of multiple myeloma results in a robust prevention of bone loss and preservation of bone strength, without apparent effects on tumor growth. These data raise the possibility of targeting sclerostin for the treatment of cancer patients with bone metastasis. Sclerostin is emerging as a valuable target to prevent the bone destruction that accompanies the growth of cancer cells in the bone. Further studies will focus on combining anti-sclerostin therapy with tumor-targeted agents to achieve both beneficial skeletal outcomes and inhibition of tumor progression.