Secreted Wnt modulators in symptomatic aortic stenosis

β-Catenin regulates endocardial cushion growth by suppressing p21

Endocardial cushion formation is essential for heart valve development and heart chamber separation. Abnormal endocardial cushion formation often causes congenital heart defects. β-Catenin is known to be essential for endocardial cushion formation; however, the underlying cellular and molecular mechanisms remain incompletely understood. Here, we show that endothelial-specific deletion of β-catenin in mice resulted in formation of hypoplastic endocardial cushions due to reduced cell proliferation and impaired cell migration. By using a β-catenin DM allele in which the transcriptional function of β-catenin is selectively disrupted, we further reveal that β-catenin regulated cell proliferation and migration through its transcriptional and non-transcriptional function, respectively. At the molecular level, loss of β-catenin resulted in increased expression of cell cycle inhibitor p21 in cushion endocardial and mesenchymal cells in vivo. In vitro rescue experiments with HUVECs and pig aortic valve interstitial cells confirmed that β-catenin promoted cell proliferation by suppressing p21. In addition, one savvy negative observation is that β-catenin was dispensable for endocardial-to-mesenchymal fate change. Taken together, our findings demonstrate that β-catenin is essential for cell proliferation and migration but dispensable for endocardial cells to gain mesenchymal fate during endocardial cushion formation. Mechanistically, β-catenin promotes cell proliferation by suppressing p21. These findings inform the potential role of β-catenin in the etiology of congenital heart defects.

Elevated plasma WIF-1 levels are associated with worse prognosis in heart failure with pulmonary hypertension

AIMS

Heart failure (HF) is a progressive condition that is becoming more prevalent in the ageing population. Pulmonary hypertension is a common complicating factor in HF and negatively impacts survival. Plasma biomarkers are a potential method for determining the prognosis of patients with left heart failure with pulmonary hypertension (LHF-PH). We aimed to analyse the prognostic capability of 33 proteins related to, among other pathways, inflammation, coagulation, and Wnt signalling in LHF-PH.

METHODS

Plasma levels of 33 proteins were analysed using proximity extension assay from the plasma of 20 controls and 67 LHF-PH patients, whereof 19 underwent heart transplantation (HT). Haemodynamics in the patients were assessed using right heart catheterization.

RESULTS

Eleven proteins had elevated plasma levels in LHF-PH compared with controls (P < 0.01), which decreased towards the controls' levels after HT (P < 0.01). Survival analysis of these proteins showed that elevated plasma levels of growth hormone, programmed cell death 1 ligand 2, tissue factor pathway inhibitor 2, and Wnt inhibitory factor 1 (WIF-1) were associated with worse transplantation-free survival in LHF-PH (P < 0.05). When adjusted for age, sex and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels using multivariable cox regressions, only WIF-1 remained prognostic [hazard ratio (95% confidence interval)] [1.013 (1.001-1.024)]. WIF-1 levels in LHF-PH patients also correlated with the mean right atrial pressure (r_s  = 0.42; P < 0.01), stroke volume index (r_s  = 0.41; P < 0.01), cardiac index (r_s  = -0.42; P < 0.01), left ventricular stroke work index (r_s  = -0.41; P < 0.01), and NT-proBNP (r_s  = 0.63; P < 0.01).

CONCLUSIONS

The present study demonstrated that LHF-PH patients have higher plasma WIF-1 levels than healthy controls, suggesting that plasma WIF-1 may be a potential future prognostic biomarker in LHF-PH. Its prognostic capability could be further refined by including it in a multi-marker panel. Further studies are needed to establish the potential role of WIF-1 in LHF-PH pathophysiology in larger cohorts to determine its clinical applicability.

KPT-330 Prevents Aortic Valve Calcification via a Novel C/EBPβ Signaling Pathway

[Figure: see text].

Circulating regulators of the wingless pathway in precapillary pulmonary hypertension

BACKGROUND AND OBJECTIVE

Dysregulated Wnt signalling has been implicated in pulmonary hypertension (PH). We hypothesized that plasma levels of secreted Wnt proteins would be increased in patients with precapillary PH, correlate with indices of vascular resistance and cardiac function and give information on long-term prognosis.

METHODS

We measured the Wnt ligand Wnt5a and secreted Wnt antagonists Dickkopf (DKK) DKK1, DKK3, secreted frizzled-related protein 3 (sFRP3), Wnt inhibitory factor-1 (WIF1) and sclerostin (SOST) in 106 patients with precapillary PH and 40 healthy controls. A second sample was obtained after a median of 4 months (n = 52). During a median of 90 months follow-up, 67 patients died.

RESULTS

Our main findings were (i) Precapillary PH is characterized by enhanced systemic Wnt activity as reflected by elevated plasma levels of Wnt5a and secreted antagonists irrespective of diagnostic subgroups. (ii) WIF1 and in particular Wnt5a correlated with pulmonary vascular resistance and cardiac dysfunction. (iii) High levels of Wnt5a, sFRP3, DKK3 and WIF1 were associated with poor prognosis in age- and sex-adjusted analysis (hazard ratios per log/SD change ~1.4) and for DKK3 after further adjustment with right arterial pressure, pulmonary oxygen saturation, cardiac index, N-terminal pro B-type natriuretic peptide and peak oxygen uptake (VO₂ ). Finally, an elevation of Wnt5a and DKK3 during follow-up was independently associated with poor prognosis.

CONCLUSION

Our data indicate that Wnt signalling pathways could be implicated in the pathogenesis of precapillary PH, and that some of the Wnt-related molecules (i.e., Wnt5a and DKK3) should be further investigated in these patients.

The Role of Wnt/β-Catenin Pathway Mediators in Aortic Valve Stenosis

Aortic valve stenosis (AVS) is a prevailing and life-threatening cardiovascular disease in adults over 75 years of age. However, the molecular mechanisms governing the pathogenesis of AVS are yet to be fully unraveled. With accumulating evidence that Wnt signaling plays a key role in the development of AVS, the involvement of Wnt molecules has become an integral study target in AVS pathogenesis. Thus, we hypothesized that the Wnt/β-catenin pathway mediators, SFRP2, DVL2, GSK3β and β-catenin are dysregulated in patients with AVS. Using immunohistochemistry, Real-Time qPCR and Western blotting, we investigated the presence of SFRP2, GSK-3β, DVL2, and β-catenin in normal and stenotic human aortic valves. Markedly higher mRNA and protein expression of GSK-3β, DVL2, β-catenin and SFRP2 were found in stenotic aortic valves. This was further corroborated by observation of their abundant immunostaining, which displayed strong immunoreactivity in diseased aortic valves. Proteomic analyses of selective GSK3b inhibition in calcifying human aortic valve interstitial cells (HAVICs) revealed enrichment of proteins involved organophosphate metabolism, while reducing the activation of pathogenic biomolecular processes. Lastly, use of the potent calcification inhibitor, Fetuin A, in calcifying HAVICs significantly reduced the expression of Wnt signaling genes Wnt3a, Wnt5a, Wnt5b, and Wnt11. The current findings of altered expression of canonical Wnt signaling in AVS suggest a possible role for regulatory Wnts in AVS. Hence, future studies focused on targeting these molecules are warranted to underline their role in the pathogenesis of the disease.

Endothelial cell-glucocorticoid receptor interactions and regulation of Wnt signaling

Vascular inflammation is present in many cardiovascular diseases, and exogenous glucocorticoids have traditionally been used as a therapy to suppress inflammation. However, recent data have shown that endogenous glucocorticoids, acting through the endothelial glucocorticoid receptor, act as negative regulators of inflammation. Here, we performed ChIP for the glucocorticoid receptor, followed by next-generation sequencing in mouse endothelial cells to investigate how the endothelial glucocorticoid receptor regulates vascular inflammation. We identified a role of the Wnt signaling pathway in this setting and show that loss of the endothelial glucocorticoid receptor results in upregulation of Wnt signaling both in vitro and in vivo using our validated mouse model. Furthermore, we demonstrate glucocorticoid receptor regulation of a key gene in the Wnt pathway, Frzb, via a glucocorticoid response element gleaned from our genomic data. These results suggest a role for endothelial Wnt signaling modulation in states of vascular inflammation.

Serum Dkk-1 (Dickkopf-1) Is a Potential Biomarker in the Prediction of Clinical Outcomes Among Patients With Acute Ischemic Stroke

Objective- Serum Dkk-1 (dickkopf-1) level has been shown to be elevated in patients with ischemic stroke, but its impact on clinical outcomes of ischemic stroke remains unclear. The aim of this study is to investigate the association between serum Dkk-1 and prognosis of ischemic stroke. Approach and Results- We measured serum Dkk-1 levels in 3178 patients with ischemic stroke from CATIS (China Antihypertensive Trial in Acute Ischemic Stroke). The primary outcome was a combination of all-cause mortality and major disability (modified Rankin scale score, ≥3) at 1 year after stroke. Secondary outcomes were stroke recurrence and vascular events. After multivariate adjustment, elevated Dkk-1 levels were associated with an increased risk of primary outcome (odds ratio, 1.40; 95% CI, 1.03-1.89; P_trend=0.015) when 2 extreme quartiles were compared. Each SD increase of log-transformed Dkk-1 was associated with 12% (95% CI, 1%-24%) increased risk of primary outcome. Multiple-adjusted spline regression model showed a linear association between serum Dkk-1 and risk of primary outcome ( P for linearity, 0.039). Subgroup analyses further confirmed these associations. The addition of serum Dkk-1 to conventional risk factors improved the predictive power for primary outcome (net reclassification improvement: 10.11%, P=0.029; integrated discrimination improvement: 0.21%, P=0.028). Conclusions- High serum Dkk-1 levels at baseline were associated with poor prognosis at 1 year after ischemic stroke, suggesting that serum Dkk-1 may be a potential prognostic biomarker for ischemic stroke. Further studies from other samples of patients with ischemic stroke are needed to replicate our findings and to clarify the potential mechanisms.

Serum sclerostin level and its relation to subclinical atherosclerosis in subjects with type 2 diabetes

BACKGROUND

Sclerostin, a Wnt-signalling inhibitor, is an established negative regulator of bone formation. However, data regarding its potential importance in vascular disease are less clear. Common carotid artery media thickness (CIMT) assessment and plaque identification using ultrasound imaging are well-recognized tools for identifying and monitoring atherosclerosis. The aim of the present study is to examine the relationship between serum sclerostin and subclinical atherosclerosis (as evidenced by CIMT).

METHODS

This cross-sectional study included 50 subjects with T2DM and 20 subjects as a control group. Multivariable linear regression models were used to assess the association of sclerostin with subclinical atherosclerosis.

RESULTS

Serum sclerostin levels in T2DM patients were significantly higher compared to the control group (167.16 ± 63.60 versus 85.98 ± 23.74 pg/ml, P < 0.0001). A concentration of ≥162.5 pg/ml showed a sensitivity of 90% and a specificity of 86.67% to detect an increased risk of subclinical atherosclerosis. Univariate analysis revealed a significant positive correlation between serum sclerostin and CIMT (r = 0.635, P < 0.001). Sclerostin concentrations remained independently associated with CIMT (β = 63.188 [6.919-119.456], P = 0.017) after adjusting for age and gender.

CONCLUSION

Our data suggest a positive correlation between serum sclerostin level and subclinical atherosclerosis in subjects with type 2 diabetes mellitus.

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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HDAC I inhibitor regulates RUNX2 transactivation through canonical and non-canonical Wnt signaling in aortic valvular interstitial cells

OBJECTIVES

The cellular mechanisms of calcific aortic valve (AV) disease and optimal medications for its treatment are poorly elucidated. Glycogen synthase kinase (GSK)-3β and non-canonical wingless-related integration site (Wnt) signaling play crucial roles in regulating the pathogenesis of valvular interstitial cell (VIC) calcification. Histone acetylation was found to regulate VIC calcification. However, whether histone deacetylases (HDACs) modulate the pathophysiology of AV calcification is unclear. Different HDAC isoforms have dissimilar cardiovascular effects. We hypothesized that distinctive HDAC inhibitors modulate runt-related transcription factor 2 (RUNX2) in aortic VICs through the regulation of Wnt signaling.

METHODS

Western blotting, real-time polymerase chain reaction, and proliferation assay were used to analyze osteogenesis marker expression, Wnt signaling, bone morphogenetic protein (BMP) signaling, and proliferation in porcine VICs treated with osteogenic (OST) medium alone or in combination with HDAC inhibitors.

RESULTS

VICs treated with OST medium for 5 days exhibited higher RUNX2 and GSK-3β expression levels than did control cells. A class I HDAC inhibitor (MS-275 at 1 μM) reduced the RUNX2 mRNA and protein expression levels and alkaline phosphatase activity and downregulated non-canonical Wnt/GSK-3β signaling, canonical Wnt/β-catenin signaling, and BMP signaling. By contrast, a combined class IIa (MC1568) and IIb HDAC (tubacin) inhibitor (0.1 μM) increased RUNX2 expression. MS-275, MC1568, and tubacin reduced VIC proliferation; however, the extent of reduction differed. MS-275 reduced RUNX2 and osteocalcin expression in VICs treated with OST medium for an extended period (14 days).

CONCLUSIONS

MS-275 critically regulates RUNX2 transactivation in VICs through both canonical and non-canonical Wnt signaling pathways.

Identification of DKK-1 as a novel mediator of statin effects in human endothelial cells

This study shows that DKK-1, a member of the Dickkopf family and a regulator of the Wnt pathways, represents a novel target of statins which, through the inhibition of HMG-CoA reductase and of non-steroidal isoprenoid intermediates, exert extra-beneficial effect in preventing atherosclerosis beyond their effect on the lipid profile. We found that atorvastatin downregulates DKK-1 protein (−88.3 ± 4.1%) and mRNA expression (−90 ± 4.2%) through the inhibition of Cdc42, Rho and Rac geranylgeranylated proteins. Further, a combined approach based on the integration of label-free quantitative mass spectrometry based-proteomics and gene silencing allowed us to demonstrate that DKK-1 itself mediates, at least in part, statin effects on human endothelial cells. Indeed, DKK-1 is responsible for the regulation of the 21% of the statin-modulated proteins, which include, among others, clusterin/apoJ, plasminogen activator inhibitor type 1 (PAI-1), myristoylated alanine-rich C-kinase substrate (MARCKS), and pentraxin 3 (PTX3). The Gene Ontology enrichment annotation revealed that DKK-1 is also a potential mediator of the extracellular matrix organization, platelet activation and response to wounding processes induced by statin. Finally, we found that plasma level of DKK-1 from cholesterol-fed rabbits treated with atorvastatin (2.5 mg/kg/day for 8 weeks) was lower (−42 ± 23%) than that of control animals. Thus, DKK-1 is not only a target of statin but it directly regulates the expression of molecules involved in a plethora of biological functions, thus expanding its role, which has been so far restricted mainly to cancer.

The Genetic Regulation of Aortic Valve Development and Calcific Disease

Heart valves are dynamic, highly organized structures required for unidirectional blood flow through the heart. Over an average lifetime, the valve leaflets or cusps open and close over a billion times, however in over 5 million Americans, leaflet function fails due to biomechanical insufficiency in response to wear-and-tear or pathological stimulus. Calcific aortic valve disease (CAVD) is the most common valve pathology and leads to stiffening of the cusp and narrowing of the aortic orifice leading to stenosis and insufficiency. At the cellular level, CAVD is characterized by valve endothelial cell dysfunction and osteoblast-like differentiation of valve interstitial cells. These processes are associated with dysregulation of several molecular pathways important for valve development including Notch, Sox9, Tgfβ, Bmp, Wnt, as well as additional epigenetic regulators. In this review, we discuss the multifactorial mechanisms that contribute to CAVD pathogenesis and the potential of targeting these for the development of novel, alternative therapeutics beyond surgical intervention.

Calcific Aortic Valve Disease: a Developmental Biology Perspective

PURPOSE OF REVIEW

This review aims to highlight the past and more current literature related to the multifaceted pathogenic programs that contribute to calcific aortic valve disease (CAVD) with a focus on the contribution of developmental programs.

RECENT FINDINGS

Calcification of the aortic valve is an active process characterized by calcific nodule formation on the aortic surface leading to a less supple and more stiffened cusp, thereby limiting movement and causing clinical stenosis. The mechanisms underlying these pathogenic changes are largely unknown, but emerging studies have suggested that signaling pathways common to valvulogenesis and bone development play significant roles and include Transforming Growth Factor-β (TGF-β), bone morphogenetic protein (BMP), Wnt, Notch, and Sox9. This comprehensive review of the literature highlights the complex nature of CAVD but concurrently identifies key regulators that can be targeted in the development of mechanistic-based therapies beyond surgical intervention to improve patient outcome.

Expression of the Frizzled receptors and their co-receptors in calcified human aortic valves

The cellular mechanisms that induce calcific aortic stenosis are yet to be unraveled. Wnt signaling is increasingly being considered as a major player in the disease process. However, the presence of Wnt Frizzled (Fzd) receptors and co-receptors LRP5 and 6 in normal and diseased human aortic valves remains to be elucidated. Immunohistochemistry and quantitative polymerase chain reaction were used to determine Fzd receptor expression in normal and calcified human aortic valve tissue, as well as human aortic valve interstitial cells (HAVICs) isolated from calcified and normal human aortic valves. There was significantly higher mRNA expression of 4 out of the 10 Fzd receptors in calcified aortic valve tissues and 8 out of the 10 in HAVICs, and both LRP5/6 co-receptors in calcified aortic valves (P < 0.05). These results were confirmed by immunohistochemistry, which revealed abundant increase in immunoreactivity for Fzd3, 7, and 8, mainly in areas of lipid core and calcified nodules of diseased aortic valves. The findings of abundant expression of Fzd and LRP5/6 receptors in diseased aortic valves suggests a potential role for both canonical and noncanonical Wnt signaling in the pathogenesis of human aortic valve calcification. Future investigations aimed at targeting these molecules may provide potential therapies for aortic valve stenosis.

Wnt signaling in cardiovascular disease: opportunities and challenges

PURPOSE OF REVIEW

Cardiometabolic diseases increasingly afflict our aging, dysmetabolic population. Complex signals regulating low-density lipoprotein receptor-related protein (LRP) and frizzled protein family members - the plasma membrane receptors for the cadre of Wnt polypeptide morphogens - contribute to the control of cardiovascular homeostasis.

RECENT FINDINGS

Both canonical (β-catenin-dependent) and noncanonical (β-catenin-independent) Wnt signaling programs control vascular smooth muscle (VSM) cell phenotypic modulation in cardiometabolic disease. LRP6 limits VSM proliferation, reduces arteriosclerotic transcriptional reprogramming, and preserves insulin sensitivity while LRP5 restrains foam cell formation. Adipose, skeletal muscle, macrophages, and VSM have emerged as important sources of circulating Wnt ligands that are dynamically regulated during the prediabetes-diabetes transition with cardiometabolic consequences. Platelets release Dkk1, a LRP5/LRP6 inhibitor that induces endothelial inflammation and the prosclerotic endothelial-mesenchymal transition. By contrast, inhibitory secreted frizzled-related proteins shape the Wnt signaling milieu to limit myocardial inflammation with ischemia-reperfusion injury. VSM sclerostin, an inhibitor of canonical Wnt signaling in bone, restrains remodeling that predisposes to aneurysm formation, and is downregulated in aneurysmal vessels by epigenetic methylation.

SUMMARY

Components of the Wnt signaling cascade represent novel targets for pharmacological intervention in cardiometabolic disease. Conversely, strategies targeting the Wnt signaling cascade for other therapeutic purposes will have cardiovascular consequences that must be delineated to establish clinically useful pharmacokinetic-pharmacodynamic relationships.

Pathophysiology of Aortic Stenosis and Mitral Regurgitation

The global impact of the spectrum of valve diseases is a crucial, fast-growing, and underrecognized health problem. The most prevalent valve diseases, requiring surgical intervention, are represented by calcific and degenerative processes occurring in heart valves, in particular, aortic and mitral valve. Due to the increasing elderly population, these pathologies will gain weight in the global health burden. The two most common valve diseases are aortic valve stenosis (AVS) and mitral valve regurgitation (MR). AVS is the most commonly encountered valve disease nowadays and affects almost 5% of elderly population. In particular, AVS poses a great challenge due to the multiple comorbidities and frailty of this patient subset. MR is also a common valve pathology and has an estimated prevalence of 3% in the general population, affecting more than 176 million people worldwide. This review will focus on pathophysiological changes in both these valve diseases, starting from the description of the anatomical aspects of normal valve, highlighting all the main cellular and molecular features involved in the pathological progression and cardiac consequences. This review also evaluates the main approaches in clinical management of these valve diseases, taking into account of the main published clinical guidelines. © 2017 American Physiological Society. Compr Physiol 7:799-818, 2017.

Pathophysiology of Aortic Valve Stenosis: Is It Both Fibrocalcific and Sex Specific?

Our understanding of the fundamental biology and identification of efficacious therapeutic targets in aortic valve stenosis has lagged far behind the fields of atherosclerosis and heart failure. In this review, we highlight the most clinically relevant problems facing men and women with fibrocalcific aortic valve stenosis, discuss the fundamental biology underlying valve calcification and fibrosis, and identify key molecular points of intersection with sex hormone signaling.

Role of Noncanonical Wnt Signaling Pathway in Human Aortic Valve Calcification

OBJECTIVE

The mechanisms underlying the pathogenesis of aortic valve calcification remain unclear. With accumulating evidence demonstrating that valve calcification recapitulates bone development, the crucial roles of noncanonical Wnt ligands WNT5a, WNT5b, and WNT11 in osteogenesis make them critical targets in the study of aortic valve calcification.

APPROACH AND RESULTS

Using immunohistochemistry, real-time qPCR, Western blotting, and tissue culture, we examined the tissue distribution of WNT5a, WNT5b, and WNT11 in noncalcified and calcified aortic valves and their effects on human aortic valve interstitial cells (HAVICs). Only focal strong immunostaining for WNT5a was seen in and around areas of calcification. Abundant immunostaining for WNT5b and WNT11 was seen in inflammatory cells, fibrosis, and activated myofibroblasts in areas of calcified foci. There was significant correlation between WNT5b and WNT11 overall staining and presence of calcification, lipid score, fibrosis, and microvessels (P<0.05). Real-time qPCR and Western blotting revealed abundant expression of both Wnts in stenotic aortic valves, particularly in bicuspid valves. Incubation of HAVICs from noncalcified valves with the 3 noncanonical Wnts significantly increased cell apoptosis and calcification (P<0.05). Treatment of HAVICs with the mitogen-activated protein kinase-38β and GSK3β inhibitors significantly reduced their mineralization (P<0.01). Raman spectroscopy identified the inorganic phosphate deposits as hydroxyapatite and showed a significant increase in hydroxyapatite deposition in HAVICs in response to WNT5a and WNT11 (P<0.05). Similar crystallinity was seen in the deposits found in HAVICs treated with Wnts and in calcified human aortic valves.

CONCLUSIONS

These findings suggest a potential role for noncanonical Wnt signaling in the pathogenesis of aortic valve calcification.

Shear-Sensitive Genes in Aortic Valve Endothelium

SIGNIFICANCE

Currently, calcific aortic valve disease (CAVD) is only treatable through surgical intervention because the specific mechanisms leading to the disease remain unclear. In this review, we explore the forces and structure of the valve, as well as the mechanosensors and downstream signaling in the valve endothelium known to contribute to inflammation and valve dysfunction.

RECENT ADVANCES

While the valvular structure enables adaptation to dynamic hemodynamic forces, these are impaired during CAVD, resulting in pathological systemic changes. Mechanosensing mechanisms-proteins, sugars, and membrane structures-at the surface of the valve endothelial cell relay mechanical signals to the nucleus. As a result, a large number of mechanosensitive genes are transcribed to alter cellular phenotype and, ultimately, induce inflammation and CAVD. Transforming growth factor-β signaling and Wnt/β-catenin have been widely studied in this context. Importantly, NADPH oxidase and reactive oxygen species/reactive nitrogen species signaling has increasingly been recognized to play a key role in the cellular response to mechanical stimuli. In addition, a number of valvular microRNAs are mechanosensitive and may regulate the progression of CAVD.

CRITICAL ISSUES

While numerous pathways have been described in the pathology of CAVD, no treatment options are available to avoid surgery for advanced stenosis and calcification of the aortic valve. More work must be focused on this issue to lead to successful therapies for the disease.

FUTURE DIRECTIONS

Ultimately, a more complete understanding of the mechanisms within the aortic valve endothelium will lead us to future therapies important for treatment of CAVD without the risks involved with valve replacement or repair. Antioxid. Redox Signal. 25, 401-414.

Wnt Signaling in Cardiac Disease

Wnt signaling encompasses multiple and complex signaling cascades and is involved in many developmental processes such as tissue patterning, cell fate specification, and control of cell division. Consequently, accurate regulation of signaling activities is essential for proper embryonic development. Wnt signaling is mostly silent in the healthy adult organs but a reactivation of Wnt signaling is generally observed under pathological conditions. This has generated increasing interest in this pathway from a therapeutic point of view. In this review article, the involvement of Wnt signaling in cardiovascular development will be outlined, followed by its implication in myocardial infarct healing, cardiac hypertrophy, heart failure, arrhythmias, and atherosclerosis. The initial experiments not always offer consensus on the effects of activation or inactivation of the pathway, which may be attributed to (i) the type of cardiac disease, (ii) timing of the intervention, and (iii) type of cells that are targeted. Therefore, more research is needed to determine the exact implication of Wnt signaling in the conditions mentioned above to exploit it as a powerful therapeutic target.

The role of Wnt regulation in heart development, cardiac repair and disease: A tissue engineering perspective

Wingless-related integration site (Wnt) signaling has proven to be a fundamental mechanism in cardiovascular development as well as disease. Understanding its particular role in heart formation has helped to develop pluripotent stem cell differentiation protocols that produce relatively pure cardiomyocyte populations. The resultant cardiomyocytes have been used to generate heart tissue for pharmaceutical testing, and to study physiological and disease states. Such protocols in combination with induced pluripotent stem cell technology have yielded patient-derived cardiomyocytes that exhibit some of the hallmarks of cardiovascular disease and are therefore being used to model disease states. While FDA approval of new treatments typically requires animal experiments, the burgeoning field of tissue engineering could act as a replacement. This would necessitate the generation of reproducible three-dimensional cardiac tissues in a well-controlled environment, which exhibit native heart properties, such as cellular density, composition, extracellular matrix composition, and structure-function. Such tissues could also enable the further study of Wnt signaling. Furthermore, as Wnt signaling has been found to have a mechanistic role in cardiac pathophysiology, e.g. heart attack, hypertrophy, atherosclerosis, and aortic stenosis, its strategic manipulation could provide a means of generating reproducible and specific, physiological and pathological cardiac models.

Serum and tissue biomarkers in aortic stenosis

Background: Calcific aortic valve stenosis (CAVS) is seen in a large proportion of individuals over 60 years. It is an active process, influenced by lipid accumulation, mechanical stress, inflammation, and abnormal extracellular matrix turnover. Various biomarkers (BMs) are studied, as regards mechanisms, diagnosis and prognosis. Methods: In the calcified valves calcium deposition, elastin fragmentation and disorganization of cellular matrix were assessed, together with expression of OPN, OPG, osteocalcin (OCN) and RL2.

We prospectively studied the following serum BMs in 60 patients with CAVS and compared them to 20 healthy controls, free from any cardiac disease: Matrix metalloproteinases (MMP) 2 and 9 and tissue inhibitor of metalloproteinase 1 (TIMP1), which regulate collagen turnover, inflammatory factors, i.e. tumor necrosis factor a (TNFa), interleukin 2 (IL2), transforming growth factor β1 (TGF-β1) which regulates fibrosis, fetuin-A (fet-A), osteopontin (OPN), osteoprotegerin (OPG), sclerostin (SOST), and relaxin-2 (RL2) which positively or negatively regulate calcification. Monocyte chemoattractant protein 1 (MCP-1) which regulates migration and infiltration of monocytes/macrophages was also studied as well as malondialdehyde (MDA) an oxidative marker. Results: Extent of tissue valve calcification (Alizarin Red stain) was negatively correlated with tissue elastin, and RL2, and positively correlated with tissue OCN and serum TIMP1 and MCP-1 and negatively with MMP9.

Tissue OCN was positively correlated with OPN and negatively with the elastin. Tissue OPN was negatively correlated with elastin and OPG. Tissue OPN OPG and RL2 were not correlated with serum levels In the serum we found in patients statistically lower TIMP1, fet-A and RL2 levels, while all other BMs were higher compared to the healthy group. Positive correlations between SOST and IL2, OPG and MDA but negative with TNFa and OPN were found; also MMP9 was negatively correlated with TNFa and MCP-1 was negatively correlated with TIMP1. Conclusion: We found that many BMs expressing calcification, collagen breakdown, or formation, and inflammation are increased in the valve tissue and in the serum of patients with CAVS as compared with healthy group. Our findings may give new insights towards diagnosis but also therapy. Thus antisclerostin, and antiflammatory agents could be tried for preventing aortic calcification progression.

Independent association between serum sclerostin levels and carotid artery atherosclerosis in prevalent haemodialysis patients

Background

Sclerostin is a soluble inhibitor of the Wnt signalling pathway and has been shown to be associated with decreased bone turnover and vascular and/or valvular calcification in patients with chronic kidney disease. Common carotid artery intima-media thickness (CIMT) assessment and common carotid artery (CCA) plaque identification with ultrasound imaging are well-recognized tools for the identification and monitoring of atherosclerosis. The aim of the present study was to investigate whether the circulating levels of sclerostin might be associated with carotid artery atherosclerosis in prevalent haemodialysis patients.

Methods

In this cross-sectional study, serum sclerostin concentrations were measured using a commercially available enzyme-linked immunosorbent assay kit. CIMT was measured and carotid plaques were identified by B-mode and Doppler ultrasound imaging.

Results

One hundred and twenty-two prevalent haemodialysis patients were involved in the study. Serum sclerostin levels were higher in patients with plaques in CCA than patients free of plaques (227 ± 166 versus 117 ± 91 pmol/L, P = 0.016). A significant correlation was recorded between serum sclerostin levels and CIMT (r = 0.459, P < 0.0001). In the multiple regression analysis, sclerostin concentrations were one of the independent factors that remained significantly associated with CIMT.

Conclusion

Sclerostin is independently associated with CIMT although further studies are needed.

Lazaroid U-74389G inhibits the osteoblastic differentiation of IL-1β-indcued aortic valve interstitial cells through glucocorticoid receptor and inhibition of NF-κB pathway

BACKGROUND

Aortic valve calcification is characterized as the active process of aortic valve interstitial cells (AVICs), and considered as an inflammatory disease. As an antioxidant, the anti-inflammatory activity of Lazaroid has been exhibited in various models. We hypothesized that Lazaroid U-74389G would inhibit the osteoblastic differentiation of AVICs induced by IL-1β.

METHODS

Normal tricuspid aortic valve leaflets were collected from patients with acute aortic dissection (Type A) undergoing the Bentall procedure. AVICs were isolated and stimulated with IL-1β in presence or absence of U-74389G in culture. Cell lysates were analyzed for osteogenic markers and nuclear factor-κB using real-time PCR and Immunoblotting. Culture media was analyzed for IL-6 and IL-8 with enzyme-linked immunosorbent assay. Alizarin Red Staining was adopted to demonstrate the calcium deposition.

RESULTS

The expression of alkaline phosphatase and bone morphogenetic protein, accompanied by the production of IL-6 and IL-8, was up-regulated in response to IL-1β and was inhibited by the addition of U-74389G. The NF-κB pathway was activated by IL-1β and involved in the suppression of U-74389G on osteoblastic differentiation in AVICs. The negative effects of U-74389G on ostengenic gene expression and mineralization of AVICs were blocked by glucocorticoid receptor antagonist mifepristone and the NF-κB inhibitor Bay 11-7082.

CONCLUSIONS

U-74389G inhibits the pro-osteogenic response to IL-1β stimulation in AVICs. The osteoblastic differentiation and mineralization of AVICs were inhabited by U-74389G though the modulation of NF-κB activation, and this pathway could be potential therapeutic targets for medical treatment of calcified aortic valve disease.

Heritability and genetics of serum dickkopf 1 levels in African ancestry families

The aim of the study was to determine the heritability of serum dickkopf-1 (DKK1) and its association with DKK1 polymorphisms in African ancestry subjects. Serum DKK1 was measured in 422 Afro-Caribbean men and women aged 18+ from 7 large, multi-generational families (mean family size: 60; 3,215 relative pairs). Twenty-four common single nucleotide polymorphisms (SNPs) were genotyped within an 80 kilobase-pair region encompassing the DKK1 gene. Heritability was estimated and SNPs were tested for association with serum DKK1 using variance components analysis. DKK1 mRNA expression was tested in peripheral blood of 16 individuals from each of the rs7069912 genotypes. Mean serum DKK1 was 1724.1 pg/mL and was significantly lower in women than men (P = 0.043). Residual genetic heritability of serum DKK1 was 0.4460 (P < 0.0001). Six SNPs reached nominal significance with DKK1, with rs7069912 being significant after adjustment for multiple comparisons. Two of these six SNPs represented independent association signals (rs7069912 and rs16928725), which accounted for 4.6% of the phenotypic variation in DKK1. Additionally, carriers of the rs7069912 variant had significantly greater DKK1 expression than non-carriers (P = 0.036). Serum DKK1 levels are highly heritable in the African ancestry families. Two SNPs within the DKK1 region accounted for nearly 5% of the variation in serum DKK1.

Circulating dickkopf-1 in diabetes mellitus: association with platelet activation and effects of improved metabolic control and low-dose aspirin

Background

Dickkopf‐1 (DKK‐1) is a major regulator of the Wnt signaling pathway, involved in inflammation, atherogenesis, and the regulation of glucose metabolism. Because platelets are major contributors to circulating levels of DKK‐1 in other clinical settings, we aimed at characterizing the platelet contribution to DKK‐1 in type 2 diabetes mellitus (T2DM) and evaluating associations of DKK‐1 with glucose metabolism, platelet activation, and endothelial dysfunction.

Methods and Results

A cross‐sectional comparison of DKK‐1, soluble CD40L (sCD40L; reflecting platelet‐mediated inflammation), asymmetric dimethylarginine (ADMA; marker of endothelial dysfunction), and urinary 11‐dehydro‐thromboxane B₂ (in vivo marker of platelet activation) was performed among 214 diabetic patients (90 receiving aspirin at 100 mg/day) and 30 healthy controls. Plasma DKK‐1 levels were markedly higher in patients with T2DM than in healthy patients (P<0.0001). DKK‐1 levels were significantly lower in diabetic patients receiving compared with those not on aspirin treatment (P=0.008); in the latter, DKK‐1 was significantly correlated with 11‐dehydro‐thromboxane B₂, ADMA, and CD40L (ρ=0.303. P<0.0001, ρ=0.45. P<0.0001, and ρ=0.37, P<0.0001, respectively) but not with glycemic control or DM duration. Among patients not receiving aspirin, improvement of metabolic control in a subgroup of newly diagnosed patients treated with acarbose for 20 weeks and in a group treated with rosiglitazone for 24 weeks was associated with concurrent significant reductions in DKK‐1 (P=0.005 and P=0.004) and 11‐dehydro‐thromboxane B₂ (P=0.005 and P=0.004).

Conclusions

Circulating DKK‐1 is increased in T2DM and associated with endothelial dysfunction and platelet activation. Plasma DKK‐1 levels are reduced with improvement of glycemic control and low‐dose aspirin treatment.

Molecular and cellular aspects of calcific aortic valve disease

Calcific aortic valve disease (CAVD) increasingly afflicts our aging population. One third of our elderly have echocardiographic or radiological evidence of calcific aortic valve sclerosis, an early and subclinical form of CAVD. Age, sex, tobacco use, hypercholesterolemia, hypertension, and type II diabetes mellitus all contribute to the risk of disease that has worldwide distribution. On progression to its most severe form, calcific aortic stenosis, CAVD becomes debilitating and devastating, and 2% of individuals >60 years are affected by calcific aortic stenosis to the extent that surgical intervention is required. No effective pharmacotherapies exist for treating those at risk for clinical progression. It is becoming increasingly apparent that a diverse spectrum of cellular and molecular mechanisms converge to regulate valvular calcium load; this is evidenced not only in histopathologic heterogeneity of CAVD, but also from the multiplicity of cell types that can participate in valve biomineralization. In this review, we highlight our current understanding of CAVD disease biology, emphasizing molecular and cellular aspects of its regulation. We end by pointing to important biological and clinical questions that must be answered to enable sophisticated disease staging and the development of new strategies to treat CAVD medically.