An epigenetic regulatory loop controls pro-osteogenic activation by TGF-β1 or bone morphogenetic protein 2 in human aortic valve interstitial cells

Unraveling the Mechanisms of Valvular Heart Disease to Identify Medical Therapy Targets: A Scientific Statement From the American Heart Association

Valvular heart disease is a common cause of morbidity and mortality worldwide and has no effective medical therapy. Severe disease is managed with valve replacement procedures, which entail high health care-related costs and postprocedural morbidity and mortality. Robust ongoing research programs have elucidated many important molecular pathways contributing to primary valvular heart disease. However, there remain several key challenges inherent in translating research on valvular heart disease to viable molecular targets that can progress through the clinical trials pathway and effectively prevent or modify the course of these common conditions. In this scientific statement, we review the basic cellular structures of the human heart valves and discuss how these structures change in primary valvular heart disease. We focus on the most common primary valvular heart diseases, including calcific aortic stenosis, bicuspid aortic valves, mitral valve prolapse, and rheumatic heart disease, and outline the fundamental molecular discoveries contributing to each. We further outline potential therapeutic molecular targets for primary valvular heart disease and discuss key knowledge gaps that might serve as future research priorities.

Noncoding RNA regulates the expression of Krm1 and Dkk2 to synergistically affect aortic valve lesions

Calcific aortic valve disease (CAVD) is becoming an increasingly important global medical problem, but effective pharmacological treatments are lacking. Noncoding RNAs play a pivotal role in the progression of cardiovascular diseases, but their relationship with CAVD remains unclear. Sequencing data revealed differential expression of many noncoding RNAs in normal and calcified aortic valves, with significant differences in circHIPK3 and miR-182-5p expression. Overexpression of circHIPK3 ameliorated aortic valve lesions in a CAVD mouse model. In vitro experiments demonstrated that circHIPK3 inhibits the osteogenic response of aortic valve interstitial cells. Mechanistically, DEAD-box helicase 5 (DDX5) recruits methyltransferase 3 (METTL3) to promote the N6-methyladenosine (m6A) modification of circHIPK3. Furthermore, m6A-modified circHIPK3 increases the stability of Kremen1 (Krm1) mRNA, and Krm1 is a negative regulator of the Wnt/β-catenin pathway. Additionally, miR-182-5p suppresses the expression of Dickkopf2 (Dkk2), the ligand of Krm1, and attenuates the Krm1-mediated inhibition of Wnt signaling. Activation of the Wnt signaling pathway significantly contributes to the promotion of aortic valve calcification. Our study describes the role of the Krm1-Dkk2 axis in inhibiting Wnt signaling in aortic valves and suggests that noncoding RNAs are upstream regulators of this process.

Relationship between arginine methylation and vascular calcification

In patients on maintenance hemodialysis (MHD), vascular calcification (VC) is an independent predictor of cardiovascular disease (CVD), which is the primary cause of death in chronic kidney disease (CKD). The main component of VC in CKD is the vascular smooth muscle cells (VSMCs). VC is an ordered, dynamic activity. Under the stresses of oxidative stress and calcium-‑phosphorus imbalance, VSMCs undergo osteogenic phenotypic transdifferentiation, which promotes the formation of VC. In addition to traditional epigenetics like RNA and DNA control, post-translational modifications have been discovered to be involved in the regulation of VC in recent years. It has been reported that the process of osteoblast differentiation is impacted by catalytic histone or non-histone arginine methylation. Its function in the osteogenic process is comparable to that of VC. Thus, we propose that arginine methylation regulates VC via many signaling pathways, including as NF-B, WNT, AKT/PI3K, TGF-/BMP/SMAD, and IL-6/STAT3. It might also regulate the VC-related calcification regulatory factors, oxidative stress, and endoplasmic reticulum stress. Consequently, we propose that arginine methylation regulates the calcification of the arteries and outline the regulatory mechanisms involved.

Molecular Interaction of Soluble Klotho with FGF23 in the Pathobiology of Aortic Valve Lesions Induced by Chronic Kidney Disease

Chronic kidney disease (CKD) is linked to greater prevalence and rapid progression of calcific aortic valve disease (CAVD) characterized by valvular leaflet fibrosis and calcification. Fibroblast growth factor 23 (FGF23) level is elevated, and anti-aging protein Klotho is reduced in CKD patients. However, the roles of FGF23 and Klotho in the mechanism of aortic valve fibrosis and calcification remain unclear. We hypothesized that FGF23 mediates CKD-induced CAVD by enhancing aortic valve interstitial cell (AVIC) fibrosis and calcification, while soluble Klotho inhibits FGF23 effect. Methods and Results: In an old mouse model of CKD, kidney damages were accompanied by aortic valve thickening and calcification. FGF23 levels in plasma and aortic valve were increased, while Klotho levels were decreased. Recombinant FGF23 elevated the inflammatory, fibrogenic, and osteogenic activities in AVICs. Neutralizing antibody or shRNA targeting FGF23 suppressed the pathobiological activities in AVICs from valves affected by CAVD. FGF23 exerts its effects on AVICs via FGF receptor (FGFR)/Yes-associated protein (YAP) signaling, and inhibition of FGFR/YAP reduced FGF23's potency in AVICs. Recombinant Klotho downregulated the pathobiological activities in AVICs exposed to FGF23. Incubation of FGF23 with Klotho formed complexes and decreased FGF23's potency. Further, treatment of CKD mice with recombinant Klotho attenuated aortic valve lesions. Conclusion: This study demonstrates that CKD induces FGF23 accumulation, Klotho insufficiency and aortic valve lesions in old mice. FGF23 upregulates the inflammatory, fibrogenic and osteogenic activities in AVICs via the FGFR/YAP signaling pathway. Soluble Klotho suppresses FGF23 effect through molecular interaction and is capable of mitigating CKD-induced CAVD.

Indoxyl Sulfate-Induced Valve Endothelial Cell Endothelial-to-Mesenchymal Transition and Calcification in an Integrin-Linked Kinase-Dependent Manner

Calcific Aortic Valve Disease (CAVD) is a significant concern for cardiovascular health and is closely associated with chronic kidney disease (CKD). Aortic valve endothelial cells (VECs) play a significant role in the onset and progression of CAVD. Previous research has suggested that uremic toxins, particularly indoxyl sulfate (IS), induce vascular calcification and endothelial dysfunction, but the effect of IS on valve endothelial cells (VECs) and its contribution to CAVD is unclear. Our results show that IS reduced human VEC viability and increased pro-calcific markers RUNX2 and alkaline phosphatase (ALP) expression. Additionally, IS-exposed VECs cultured in pro-osteogenic media showed increased calcification. Mechanistically, IS induced endothelial-to-mesenchymal transition (EndMT), evidenced by the loss of endothelial markers and increased expression of mesenchymal markers. IS triggered VEC inflammation, as revealed by NF-kB activation, and decreased integrin-linked kinase (ILK) expression. ILK overexpression reversed the loss of endothelial phenotype and RUNX2, emphasizing its relevance in the pathogenesis of CAVD in CKD. Conversely, a lower dose of IS intensified some of the effects in EndMT caused by silencing ILK. These findings imply that IS affects valve endothelium directly, contributing to CAVD by inducing EndMT and calcification, with ILK acting as a crucial modulator.

The E3 ubiquitin ligases regulate inflammation in cardiovascular diseases

Accumulating evidence has illustrated that the E3 ubiquitin ligases critically participate in the development and progression of cardiovascular diseases. Dysregulation of E3 ubiquitin ligases exacerbates cardiovascular diseases. Blockade or activation of E3 ubiquitin ligases mitigates cardiovascular performance. Therefore, in this review, we mainly introduced the critical role and underlying molecular mechanisms of E3 ubiquitin ligase NEDD4 family in governing the initiation and progression of cardiovascular diseases, including ITCH, WWP1, WWP2, Smurf1, Smurf2, Nedd4-1 and Nedd4-2. Moreover, the functions and molecular insights of other E3 ubiquitin ligases, such as F-box proteins, in cardiovascular disease development and malignant progression are described. Furthermore, we illustrate several compounds that alter the expression of E3 ubiquitin ligases to alleviate cardiovascular diseases. Therefore, modulation of E3 ubiquitin ligases could be a novel and promising strategy for improvement of therapeutic efficacy of deteriorative cardiovascular diseases.

Similarities and Differences of Vascular Calcification in Diabetes and Chronic Kidney Disease

Presently, the mechanism of occurrence and development of vascular calcification (VC) is not fully understood; a range of evidence suggests a positive association between diabetes mellitus (DM) and VC. Furthermore, the increasing burden of central vascular disease in patients with chronic kidney disease (CKD) may be due, at least in part, to VC. In this review, we will review recent advances in the mechanisms of VC in the context of CKD and diabetes. The study further unveiled that VC is induced through the stimulation of pro-inflammatory factors, which in turn impairs endothelial function and triggers similar mechanisms in both disease contexts. Notably, hyperglycemia was identified as the distinctive mechanism driving calcification in DM. Conversely, in CKD, calcification is facilitated by mechanisms including mineral metabolism imbalance and the presence of uremic toxins. Additionally, we underscore the significance of investigating vascular alterations and newly identified molecular pathways as potential avenues for therapeutic intervention.

Extracellular vesicles in atherosclerosis and vascular calcification: the versatile non-coding RNAs from endothelial cells and vascular smooth muscle cells

Atherosclerosis (AS) is characterized by the accumulation of lipids, fibrous elements, and calcification in the innermost layers of arteries. Vascular calcification (VC), the deposition of calcium and phosphate within the arterial wall, is an important characteristic of AS natural history. However, medial arterial calcification (MAC) differs from intimal calcification and cannot simply be explained as the consequence of AS. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are directly involved in AS and VC processes. Understanding the communication between ECs and VSMCs is critical in revealing mechanisms underlying AS and VC. Extracellular vesicles (EVs) are found as intercellular messengers in kinds of physiological processes and pathological progression. Non-coding RNAs (ncRNAs) encapsulated in EVs are involved in AS and VC, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). The effects of ncRNAs have not been comprehensively understood, especially encapsulated in EVs. Some ncRNAs have demonstrated significant roles in AS and VC, but it remains unclear the functions of the majority ncRNAs detected in EVs. In this review, we summarize ncRNAs encapsulated in EC-EVs and VSMC-EVs, and the signaling pathways that are involved in AS and VC.

Vascular calcification in CKD: New insights into its mechanisms

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

Challenges of Managing Non-rheumatic Aortic Valve Disorder in a Genetically Susceptible Woman

In this case report, we investigated the potential link between SMAD3/transforming growth factor β (TGF-β) pathway dysregulation and aortic valvular disease. We report a middle-aged female, heterozygous for the R18W novel variant of the SMAD3 gene, with a history of an aortic valve disorder and three aortic valve replacements in a span of 15 years. The patient neither has a history of congenital connective tissue disorders nor any known congenital valvular defects. The patient had genetic testing for thoracic aortic aneurysm and dissection (TAAD)/Marfan syndrome/related disorders. She was found to be heterozygous for the p.Arg18Trp (R18W) protein variant of the SMAD3 gene (chromosome position 15:67430416), coding DNA c.52 C>T. Members of the transforming growth factor β (TGF-β) family and their downstream signaling proteins, including SMAD, are important for establishing proper embryogenic development and maintaining adult tissue homeostasis. Investigating the disturbances within the TGF-β signaling pathways may provide insightful knowledge of how genetic factors can cause structural and functional valvular defects.

Abnormally elevated EZH2-mediated H3K27me3 enhances osteogenesis in aortic valve interstitial cells by inhibiting SOCS3 expression

BACKGROUND AND AIMS

The osteogenic transition of aortic valve interstitial cells (AVICs) plays a critical role for the progression of calcific aortic valve disease (CAVD). Enhancer of zeste homolog 2 (EZH2) is an important methyltransferase for histone H3 Lys27 (H3K27) that has been found to be involved in osteogenesis. Here, we investigated the effect and mechanism of EZH2 in CAVD progression.

METHODS

High throughout mRNA sequencing, qRT-PCR and immunoblot were performed to screen differentially expressed genes in non-CAVD and CAVD aortic valves. To investigate the role of EZH2 and SOCS3 in osteogenesis, AVICs were treated with siRNA, adenovirus and specific inhibitors, then osteogenic markers and mineralized deposits were examined. In vivo, the morphology and function of aortic valves were investigated by HE stain and echocardiography in ApoE^-/- mice fed a long-term western diet (WD).

RESULTS

We discovered that EZH2 was upregulated and SOCS3 was downregulated in calcified aortic valves. In AVICs, inhibition or silencing of EZH2 attenuated the osteogenic responses. On the other hand, demethylases inhibitor (GSK-J4) enhanced osteogenic transition of AVICs. Moreover, SOCS3 knockdown enhanced the expression of osteogenic markers, while SOCS3 overexpression suppressed osteogenesis and calcification. The chromatin immunoprecipitation and restored experiments indicated that EZH2 directly targeted SOCS3 to promote osteogenic responses of AVICs. In vivo, treatment with EZH2 inhibitor through intraperitoneal injection attenuated aortic valve thickening, calcification and dysfunction induced by WD.

CONCLUSIONS

Collectively, we found that EZH2-mediated H3K27me3 enhanced osteogenesis and microcalcification of AVICs via inhibiting SOCS3 expression, which provides potential targets for future therapeutic interventions of CAVD.

Integrin-Linked Kinase Expression in Human Valve Endothelial Cells Plays a Protective Role in Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) is highly prevalent during aging. CAVD initiates with endothelial dysfunction, leading to lipid accumulation, inflammation, and osteogenic transformation. Integrin-linked kinase (ILK) participates in the progression of cardiovascular diseases, such as endothelial dysfunction and atherosclerosis. However, ILK role in CAVD is unknown. First, we determined that ILK expression is downregulated in aortic valves from patients with CAVD compared to non-CAVD, especially at the valve endothelium, and negatively correlated with calcification markers. Silencing ILK expression in human valve endothelial cells (siILK-hVECs) induced endothelial-to-mesenchymal transition (EndMT) and promoted a switch to an osteoblastic phenotype; SiILK-hVECs expressed increased RUNX2 and developed calcified nodules. siILK-hVECs exhibited decreased NO production and increased nitrosative stress, suggesting valvular endothelial dysfunction. NO treatment of siILK-hVECs prevented VEC transdifferentiation, while treatment with an eNOS inhibitor mimicked ILK-silencing induction of EndMT. Accordingly, NO treatment inhibited VEC calcification. Mechanistically, siILK-hVECs showed increased Smad2 phosphorylation, suggesting a TGF-β-dependent mechanism, and NO treatment decreased Smad2 activation and RUNX2. Experiments performed in eNOS KO mice confirmed the involvement of the ILK-eNOS signaling pathway in valve calcification, since aortic valves from these animals showed decreased ILK expression, increased RUNX2, and calcification. Our study demonstrated that ILK endothelial expression participates in human CAVD development by preventing endothelial osteogenic transformation.

The mechanistic pathways of oxidative stress in aortic stenosis and clinical implications

Despite the elucidation of the pathways behind the development of aortic stenosis (AS), there remains no effective medical treatment to slow or reverse its progress. Instead, the gold standard of care in severe or symptomatic AS is replacement of the aortic valve. Oxidative stress is implicated, both directly as well as indirectly, in lipid infiltration, inflammation and fibro-calcification, all of which are key processes underlying the pathophysiology of degenerative AS. This culminates in the breakdown of the extracellular matrix, differentiation of the valvular interstitial cells into an osteogenic phenotype, and finally, calcium deposition as well as thickening of the aortic valve. Oxidative stress is thus a promising and potential therapeutic target for the treatment of AS. Several studies focusing on the mitigation of oxidative stress in the context of AS have shown some success in animal and in vitro models, however similar benefits have yet to be seen in clinical trials. Statin therapy, once thought to be the key to the treatment of AS, has yielded disappointing results, however newer lipid lowering therapies may hold some promise. Other potential therapies, such as manipulation of microRNAs, blockade of the renin-angiotensin-aldosterone system and the use of dipeptidylpeptidase-4 inhibitors will also be reviewed.

Fibroblast growth factor 2 inhibits myofibroblastic activation of valvular interstitial cells

Heart valve disease is a growing problem worldwide. Though very common in older adults, the mechanisms behind the development of the disease aren't well understood, and at present the only therapeutic option is valve replacement. Valvular interstitial cells (VICs) may hold the answer. These cells can undergo pathological differentiation into contractile myofibroblasts or osteoblasts, leading to thickening and calcification of the valve tissue. Our study aimed to characterise the effect of fibroblast growth factor 2 (FGF-2) on the differentiation potential of VICs. We isolated VICs from diseased human valves and treated these cells with FGF-2 and TGF-β to elucidate effect of these growth factors on several myofibroblastic outcomes, in particular immunocytochemistry and gene expression. We used TGF-β as a positive control for myofibroblastic differentiation. We found that FGF-2 promotes a 'quiescent-type' morphology and inhibits the formation of α-smooth muscle actin positive myofibroblasts. FGF-2 reduced the calcification potential of VICs, with a marked reduction in the number of calcific nodules. FGF-2 interrupted the 'canonical' TGF-β signalling pathway, reducing the nuclear translocation of the SMAD2/3 complex. The panel of genes assayed revealed that FGF-2 promoted a quiescent-type pattern of gene expression, with significant downregulations in typical myofibroblast markers α smooth muscle actin, extracellular matrix proteins, and scleraxis. We did not see evidence of osteoblast differentiation: neither matrix-type calcification nor changes in osteoblast associated gene expression were observed. Our findings show that FGF-2 can reverse the myofibroblastic phenotype of VICs isolated from diseased valves and inhibit the calcification potential of these cells.

Post-Transcriptional Regulation of Molecular Determinants during Cardiogenesis

Cardiovascular development is initiated soon after gastrulation as bilateral precardiac mesoderm is progressively symmetrically determined at both sides of the developing embryo. The precardiac mesoderm subsequently fused at the embryonic midline constituting an embryonic linear heart tube. As development progress, the embryonic heart displays the first sign of left-right asymmetric morphology by the invariably rightward looping of the initial heart tube and prospective embryonic ventricular and atrial chambers emerged. As cardiac development progresses, the atrial and ventricular chambers enlarged and distinct left and right compartments emerge as consequence of the formation of the interatrial and interventricular septa, respectively. The last steps of cardiac morphogenesis are represented by the completion of atrial and ventricular septation, resulting in the configuration of a double circuitry with distinct systemic and pulmonary chambers, each of them with distinct inlets and outlets connections. Over the last decade, our understanding of the contribution of multiple growth factor signaling cascades such as Tgf-beta, Bmp and Wnt signaling as well as of transcriptional regulators to cardiac morphogenesis have greatly enlarged. Recently, a novel layer of complexity has emerged with the discovery of non-coding RNAs, particularly microRNAs and lncRNAs. Herein, we provide a state-of-the-art review of the contribution of non-coding RNAs during cardiac development. microRNAs and lncRNAs have been reported to functional modulate all stages of cardiac morphogenesis, spanning from lateral plate mesoderm formation to outflow tract septation, by modulating major growth factor signaling pathways as well as those transcriptional regulators involved in cardiac development.

MicroRNA-22 promoted osteogenic differentiation of valvular interstitial cells by inhibiting CAB39 expression during aortic valve calcification

Calcific aortic valve disease (CAVD) is a common valve disease characterized by the fibro-calcific remodeling of the aortic valves, which is an actively regulated process involving osteogenic differentiation of valvular interstitial cells (VICs). MicroRNA (miRNA) is an essential regulator in diverse biological processes in cells. The present study aimed to explore the role and mechanism of miR-22 in the osteogenic differentiation of VICs. The expression profile of osteogenesis-related miRNAs was first detected in aortic valve tissue from CAVD patients (n = 33) and healthy controls (n = 12). miR-22 was highly expressed in calcified valve tissues (P < 0.01), and the expression was positively correlated with the expression of OPN (rs = 0.820, P < 0.01) and Runx2 (rs = 0.563, P < 0.01) in VICs isolated from mild or moderately calcified valves. The sustained high expression of miR-22 was also validated in an in-vitro VICs osteogenic model. Adenovirus-mediated gain-of-function and loss-of-function experiments were then performed. Overexpression of miR-22 significantly accelerated the calcification process of VICs, manifested by significant increases in calcium deposition, alkaline phosphate activity, and expression of osteoblastic differentiation markers. Conversely, inhibition of miR-22 significantly negated the calcification process. Subsequently, calcium-binding protein 39 (CAB39) was identified as a target of miR-22. Overexpression of miR-22 significantly reduced the expression of CAB39 in VICs, leading to decreased catalytic activity of the CAB39-LKB1-STRAD complex, which, in turn, exacerbated changes in the AMPK-mTOR signaling pathway, and ultimately accelerated the calcification process. In addition, ROS generation and autophagic activity during VIC calcification were also regulated by miR-22/CAB39 pathway. These results indicate that miR-22 is an important accelerator of the osteogenic differentiation of VICs, and a potential therapeutic target in CAVD.

Osteomodulin attenuates smooth muscle cell osteogenic transition in vascular calcification

RATIONALE

Vascular calcification is a prominent feature of late-stage diabetes, renal and cardiovascular disease (CVD), and has been linked to adverse events. Recent studies in patients reported that plasma levels of osteomodulin (OMD), a proteoglycan involved in bone mineralisation, associate with diabetes and CVD. We hypothesised that OMD could be implicated in these diseases via vascular calcification as a common underlying factor and aimed to investigate its role in this context.

METHODS AND RESULTS

In patients with chronic kidney disease, plasma OMD levels correlated with markers of inflammation and bone turnover, with the protein present in calcified arterial media. Plasma OMD also associated with cardiac calcification and the protein was detected in calcified valve leaflets by immunohistochemistry. In patients with carotid atherosclerosis, circulating OMD was increased in association with plaque calcification as assessed by computed tomography. Transcriptomic and proteomic data showed that OMD was upregulated in atherosclerotic compared to control arteries, particularly in calcified plaques, where OMD expression correlated positively with markers of smooth muscle cells (SMCs), osteoblasts and glycoproteins. Immunostaining confirmed that OMD was abundantly present in calcified plaques, localised to extracellular matrix and regions rich in α-SMA+ cells. In vivo, OMD was enriched in SMCs around calcified nodules in aortic media of nephrectomised rats and in plaques from ApoE-/- mice on warfarin. In vitro experiments revealed that OMD mRNA was upregulated in SMCs stimulated with IFNγ, BMP2, TGFβ1, phosphate and β-glycerophosphate, and by administration of recombinant human OMD protein (rhOMD). Mechanistically, addition of rhOMD repressed the calcification process of SMCs treated with phosphate by maintaining their contractile phenotype along with enriched matrix organisation, thereby attenuating SMC osteoblastic transformation. Mechanistically, the role of OMD is exerted likely through its link with SMAD3 and TGFB1 signalling, and interplay with BMP2 in vascular tissues.

CONCLUSION

We report a consistent association of both circulating and tissue OMD levels with cardiovascular calcification, highlighting the potential of OMD as a clinical biomarker. OMD was localised in medial and intimal α-SMA+ regions of calcified cardiovascular tissues, induced by pro-inflammatory and pro-osteogenic stimuli, while the presence of OMD in extracellular environment attenuated SMC calcification.

The Complex Interplay of Inflammation, Metabolism, Epigenetics, and Sex in Calcific Disease of the Aortic Valve

Calcification of the aortic valve is one of the most rapidly increasing pathologies in the aging population worldwide. Traditionally associated to cardiovascular risk conditions, this pathology is still relatively unaddressed on a molecular/cellular standpoint and there are no available treatments to retard its progression unless valve substitution. In this review, we will describe some of the most involved inflammatory players, the metabolic changes that may be responsible of epigenetic modifications and the gender-related differences in the onset of the disease. A better understanding of these aspects and their integration into a unique pathophysiology context is relevant to improve current therapies and patients management.

Exploring potential genes and pathways related to calcific aortic valve disease

Calcific aortic valve disease (CAVD) is currently the most prevalent valvular disease. However, the pathological mechanism of CAVD has not yet been fully elucidated, and no drugs can delay or halt the progression of CAVD. This study aimed to screen for potential biomarkers and pathways of CAVD through bioinformatics analysis. The identification of differentially expressed genes (DEGs) between calcific aortic valves and the control group was performed based on four microarray datasets: GSE12644, GSE51472, GSE77287 and GSE83453. Gene Ontology and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment analysis were conducted. Furthermore, the protein-protein interaction network, and microRNA-target interaction was performed, and hub genes were obtained by using twelve cytoHubba algorithms. As a result, 327 DEGs were identified, including 206 up-regulated and 121 down-regulated genes. KEGG analysis showed that these DEGs were mainly enriched in the PI3K-AKT signaling pathway, ECM-receptor interaction, cytokine-cytokine receptor interaction, and chemokine signaling pathway etc. Moreover, we identified 19 hub genes: CXCL8, CXCL12, CSF1R, HCK, PLEK, CCL5, TLR8, VCAM1, CCR1, CCR7, FPR1, TYROBP, CX3CR1, KIT, PPBP, SPP1, SYK, TLR7, and VWF. And multiple potential miRNAs, including miR-141, miR-34a, miR-155, and miR-486, were identified. And western blot was performed to validate the expression level of hub genes. In conclusion, this study identified several promising biomarkers and pathways for CAVD, which may provide novel molecular markers for diagnosis and targeted therapy.

Self-eating and Heart: The Emerging Roles of Autophagy in Calcific Aortic Valve Disease

Autophagy is a self-degradative pathway by which subcellular elements are broken down intracellularly to maintain cellular homeostasis. Cardiac autophagy commonly decreases with aging and is accompanied by the accumulation of misfolded proteins and dysfunctional organelles, which are undesirable to the cell. Reduction of autophagy over time leads to aging-related cardiac dysfunction and is inversely related to longevity. However, despite the increasing interest in autophagy in cardiac diseases and aging, the process remains an undervalued and disregarded object in calcific valvular disease. Neither the nature through which autophagy is triggered nor the interplay between autophagic machinery and targeted molecules during aortic valve calcification are fully understood. Recently, the upregulation of autophagy has been shown to result in cardioprotective effects against cell death as well as its origin. Here, we review the evidence that shows how autophagy can be both beneficial and detrimental as it pertains to aortic valve calcification in the heart.

Isolation of Human Primary Valve Cells for In vitro Disease Modeling

Calcific aortic valve disease (CAVD) is present in nearly a third of the elderly population. Thickening, stiffening, and calcification of the aortic valve causes aortic stenosis and contributes to heart failure and stroke. Disease pathogenesis is multifactorial, and stresses such as inflammation, extracellular matrix remodeling, turbulent flow, and mechanical stress and strain contribute to the osteogenic differentiation of valve endothelial and valve interstitial cells. However, the precise initiating factors that drive the osteogenic transition of a healthy cell into a calcifying cell are not fully defined. Further, the only current therapy for CAVD-induced aortic stenosis is aortic valve replacement, whereby the native valve is removed (surgical aortic valve replacement, SAVR) or a fully collapsible replacement valve is inserted via a catheter (transcatheter aortic valve replacement, TAVR). These surgical procedures come at a high cost and with serious risks; thus, identifying novel therapeutic targets for drug discovery is imperative. To that end, the present study develops a workflow where surgically removed tissues from patients and donor cadaver tissues are used to create patient-specific primary lines of valvular cells for in vitro disease modeling. This protocol introduces the utilization of a cold storage solution, commonly utilized in organ transplant, to reduce the damage caused by the often-lengthy procurement time between tissue excision and laboratory processing with the benefit of greatly stabilizing cells of the excised tissue. The results of the present study demonstrate that isolated valve cells retain their proliferative capacity and endothelial and interstitial phenotypes in culture upwards of several days after valve removal from the donor. Using these materials allows for the collection of control and CAVD cells, from which both control and disease cell lines are established.

Triptolide Attenuates Vascular Calcification by Upregulating Expression of miRNA-204

Background: Triptolide (TP), a naturally derived compound from Tripterygium wilfordii, has been proven effective in protecting against cardiovascular system, but the molecular mechanisms underlying its protective effects are poorly understood. In the current study, we sought to test the potential protective role of TP in the regulation of vascular calcification in a rat model and explore whether TP attenuates medial vascular calcification by upregulating miRNA-204.

Methods: Vitamin D3 plus nicotine (VDN) was used to induce a vascular calcification (VC) model of rat aorta. Von Kossa and Hematoxylin-Eosin staining were applied to assess the degree of calcification of rat aortas. Calcium content and alkaline phosphatase activity were measured. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was applied to quantify miRNA-204 expression. The localization of runt-related transcription factor-2 (RUNX2) and bone morphogenetic protein-2 (BMP2) expressions were detected by immunohistochemistry and western blotting.

Results: Administration of TP greatly reduced vascular calcification in a dose-dependent manner compared with VC controls. The increase in ALP activity and calcium content was ameliorated by TP. Moreover, protein expression levels of BMP2 and RUNX2 were significantly reduced in calcified aortas. MiRNA-204 expression was increased in the TP-treated groups compared with VC controls and the effects of TP were reversed by the intravenous injection of miRNA-204-interfering lentivirus. However, the miRNA-204-overexpressing lentivirus had no additional effects on ALP activity, calcium content, BMP2 and RUNX2 expressions compared with those from TP group.

Conclusion: TP inhibited BMP2 and RUNX2 expression and attenuated vascular calcification via upregulating the level of miRNA-204. TP appears to be a potential new therapeutic option for treating vascular calcification.

The role of bone morphogenetic protein signaling in vascular calcification

Vascular calcification is associated with atherosclerosis, chronic kidney disease, and diabetes, and results from processes resembling endochondral or intramembranous ossification, or from processes that are distinct from ossification. Bone morphogenetic proteins (BMP), as well as other ligands, receptors, and regulators of the transforming growth factor beta (TGFβ) family regulate vascular and valvular calcification by modulating the phenotypic plasticity of multipotent progenitor lineages associated with the vasculature or valves. While osteogenic ligands BMP2 and BMP4 appear to be both markers and drivers of vascular calcification, particularly in atherosclerosis, BMP7 may serve to protect against calcification in chronic kidney disease. BMP signaling regulators such as matrix Gla protein and BMP-binding endothelial regulator protein (BMPER) play protective roles in vascular calcification. The effects of BMP signaling molecules in vascular calcification are context-dependent, tissue-dependent, and cell-type specific. Here we review the current knowledge on mechanisms by which BMP signaling regulates vascular calcification and the potential therapeutic implications.

The roles of non-coding RNAs in vascular calcification and opportunities as therapeutic targets

Vascular calcification (VC) is characterized by an accumulation of calcium phosphate crystals inside the vessel wall. VC is often associated with diabetes, chronic kidney disease (CKD), atherosclerosis, and cardiovascular disease (CVD). Even though the number of patients with VC remains prevalent, there are still no approved therapies for the treatment of VC. Since the pathogenesis of VC is diverse and involves multiple factors and mechanisms, it is critical to reveal the novel mechanisms involved in VC. Although protein-coding RNAs involved in VC have been extensively studied, the roles of non-coding RNAs (ncRNAs) are not yet fully understood. The field of ncRNAs has recently received attention, and accumulating evidence from studies in VC suggests that ncRNAs, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), play an important role in the regulation of VC. NcRNAs can modulate VC by acting as promoters or inhibitors and may be useful in the clinical diagnosis and treatment of VC. In this article, we review and discuss ncRNAs that regulate VC and present the therapeutic implications of these ncRNAs.

E3 Ubiquitin ligase NEDD4 family‑regulatory network in cardiovascular disease

Protein ubiquitination represents a critical modification occurring after translation. E3 ligase catalyzes the covalent binding of ubiquitin to the protein substrate, which could be degraded. Ubiquitination as an important protein post-translational modification is closely related to cardiovascular disease. The NEDD4 family, belonging to HECT class of E3 ubiquitin ligases can recognize different substrate proteins, including PTEN, ENaC, Nav1.5, SMAD2, PARP1, Septin4, ALK1, SERCA2a, TGFβR3 and so on, via the WW domain to catalyze ubiquitination, thus participating in multiple cardiovascular-related disease such as hypertension, arrhythmia, myocardial infarction, heart failure, cardiotoxicity, cardiac hypertrophy, myocardial fibrosis, cardiac remodeling, atherosclerosis, pulmonary hypertension and heart valve disease. However, there is currently no review comprehensively clarifying the important role of NEDD4 family proteins in the cardiovascular system. Therefore, the present review summarized recent studies about NEDD4 family members in cardiovascular disease, providing novel insights into the prevention and treatment of cardiovascular disease. In addition, assessing transgenic animals and performing gene silencing would further identify the ubiquitination targets of NEDD4. NEDD4 quantification in clinical samples would also constitute an important method for determining NEDD4 significance in cardiovascular disease.

MicroRNA‑204‑5p inhibits the osteogenic differentiation of ankylosing spondylitis fibroblasts by regulating the Notch2 signaling pathway

Ankylosing spondylitis (AS) is a chronic inflammatory systemic disease and is difficult to detect in the early stages. The present study aimed to investigate the role of microRNA (miR)-204-5p in osteogenic differentiation of AS fibroblasts. Bone morphogenetic protein 2 (BMP-2) was used to induce osteogenic differentiation. Cells were divided into the following groups: AS group, AS + BMP-2 group, AS + BMP-2 + miR-negative control group, AS + BMP-2 + miR-204-5p mimics group and AS + BMP-2 + miR-204-5p mimics + pcDNA-Notch2 group. The expression levels of miR-204-5p, Notch2, runt-related transcription factor 2 (RUNX2) and osteocalcin were detected via reverse transcription-quantitative PCR analysis. The binding site between Notch2 and miR-204-5p was predicted using TargetScan software and verified via the dual-luciferase reporter assay. Alkaline phosphatase (ALP) activity was assessed via the ALP assay, while the mineralized nodules area was determined via the Alizarin Red S staining assay. The results demonstrated that Notch2 is a target gene of miR-204-5p. Furthermore, treatment with BMP-2 significantly decreased miR-204-5p expression, and significantly increased ALP activity, the mineralized nodules area and the expression levels of Notch2, RUNX2 and osteocalcin in ligament fibroblasts (all P<0.05). Conversely, transfection with miR-204-5p mimics significantly increased miR-204-5p expression, and significantly decreased ALP activity, the mineralized nodules area and the expression levels of Notch2, RUNX2 and osteocalcin in ligament fibroblasts (all P<0.05). Notably, transfection with pcDNA-Notch2 significantly reversed the inhibitory effects induced by miR-204-5p mimics on the osteogenic differentiation of ligament fibroblasts (all P<0.05). Furthermore, miR-204-5p inhibited the osteogenic differentiation of ligament fibroblasts in patients with AS by targeting Notch2. Thus, miR-204-5p may negatively regulate Notch2 expression and may be a potential therapeutic target for AS. Collectively, the results of the present study provide a theoretical basis for the effective treatment of patients with AS.

Non-coding RNAs: Regulators of valvular calcification

There is currently a growing global burden of valvular heart diseases due to aging populations and changing lifestyles. Valvular heart diseases mainly include the malfunctioning of aortic and mitral valves and are characterized by extensive tissue remodeling, which includes calcification, endothelial dysfunction, and endothelial-mesenchymal transition. These valvular remodeling processes are known to be regulated by protein-coding genes as well as non-coding genes. Here, we have summarized studies highlighting the non-coding RNA mediated regulation of valvular tissue remodeling and their potential therapeutic benefits. Additionally, studies investigating the diagnostic capability of circulating non-coding RNA molecules in valvular diseases are also summarized. Overall, of the various candidates, several studies have highlighted miR-214 and miR-204 as central regulators of valvular calcification.

TCDD inhibited the osteogenic differentiation of human fetal palatal mesenchymal cells through AhR and BMP-2/TGF-β/Smad signaling

Exposure to environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes cleft palate at high rates, but little is known about the underlying biological mechanisms. In the present study, we cultured osteoblasts from human fetal palate mesenchymal cells (hFPMCs) to explore the effects of TCDD on osteogenic differentiation. The results showed that TCDD significantly decreased cell proliferation, alkaline phosphatase (ALP) activity and calcium deposition. RNA analyses and protein detection demonstrated that TCDD downregulated a wide array of pro-osteogenic biomarkers. Further investigation of the underlying molecular mechanisms revealed that exposure to TCDD activated aryl hydrocarbon receptor (AhR) signaling and inhibited BMP-2/TGF-β1/Smad pathway molecules. The inactivation of AhR signaling using CRISPR/Cas9-mediated AhR deletion or by genetic siRNA knockdown significantly blocked the effects induced by TCDD, suggesting a critical role of AhR activation in the TCDD-mediated inhibition of hFPMC osteogenic differentiation. The cotreatment with TGF-β1 or BMP-2 and TCDD significantly relieved the activation of AhR and rescued the impairment of osteogenesis caused by TCDD. Taken together, our findings indicated that TCDD inhibited the osteogenic differentiation of hFPMCs via crosstalk between AhR and BMP-2/TGF-β1/Smad signaling pathway.

Potential microRNA-related targets in clearance pathways of amyloid-β: novel therapeutic approach for the treatment of Alzheimer's disease

Imbalance between amyloid-beta (Aβ) peptide synthesis and clearance results in Aβ deregulation. Failure to clear these peptides appears to cause the development of Alzheimer's disease (AD). In recent years, microRNAs have become established key regulators of biological processes that relate among others to the development and progression of neurodegenerative diseases, such as AD. This review article gives an overview on microRNAs that are involved in the Aβ cascade and discusses their inhibitory impact on their target mRNAs whose products participate in Aβ clearance. Understanding of the mechanism of microRNA in the associated signal pathways could identify novel therapeutic targets for the treatment of AD.

Identification of miR-143 as a Major Contributor for Human Stenotic Aortic Valve Disease

Calcification of aortic valves leads to aortic stenosis mainly in elderly individuals, but the underlying molecular mechanisms are still not understood. Here, we studied microRNA (miR, miRNA) expression and function in healthy and stenotic human aortic valves. We identified miR-21, miR-24, and miR-143 to be highly upregulated in stenotic aortic valves. Using luciferase reporter systems, we found direct binding of miR-143 to the 3'UTR region of the matrix gla protein (MGP), which in turn is a key factor to sustain homeostasis in aortic valves. In subsequent experiments, we demonstrated a therapeutic potential of miRNA regulation during calcification in cardiac valvular interstitial cells. Collectively, our data provide evidence that deregulated miR expression contributes to the development of stenotic valve disease and thus form novel therapeutic opportunities of this severe cardiovascular disease.

Endocardial Cell Plasticity in Cardiac Development, Diseases and Regeneration

Endocardial cells are specialized endothelial cells that form the innermost layer of the heart wall. By virtue of genetic lineage-tracing technology, many of the unexpected roles of endocardium during murine heart development, diseases, and regeneration have been identified recently. In addition to heart valves developed from the well-known endothelial to mesenchymal transition, recent fate-mapping studies using mouse models reveal that multiple cardiac cell lineages are also originated from the endocardium. This review focuses on a variety of different cell types that are recently reported to be endocardium derived during murine heart development, diseases, and regeneration. These multiple cell fates underpin the unprecedented roles of endocardial progenitors in function, pathological progression, and regeneration of the heart. Because emerging studies suggest that developmental mechanisms can be redeployed and recapitulated in promoting heart disease development and also cardiac repair and regeneration, understanding the mechanistic regulation of endocardial plasticity and modulation of their cell fate conversion may uncover new therapeutic potential in facilitating heart regeneration.

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.

Noncoding RNAs in Calcific Aortic Valve Disease: A Review of Recent Studies

Calcific aortic valve disease (CAVD) is the most common heart valve disorder in human populations. Nevertheless, there are presently no effective means for its prevention and treatment. It is therefore critical to comprehensively define key mechanisms of the disease. A major focus of cardiovascular research has been characterization of how regulation of gene expression maintains healthy physiologic status of the component tissues of the system and how derangements of gene regulation may become pathological. Recently, substantial evidence has emerged that noncoding RNAs, which are an enormous and versatile class of regulatory elements, such as microRNAs and long noncoding RNAs, have roles in onset and prognosis of CAVD. Authors of the present report have therefore here provided a summary of the current understanding of contributions made by noncoding RNAs major features of CAVD. It is anticipated that this article will serve as a valuable guide to research strategy in this field and may additionally provide both researchers and clinicians with an expanded range of CAVD-associated biomarkers.

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.

Bone remodeling induced by mechanical forces is regulated by miRNAs

The relationship between mechanical force and alveolar bone remodeling is an important issue in orthodontics because tooth movement is dependent on the response of bone tissue to the mechanical force induced by the appliances used. Mechanical cyclical stretch (MCS), fluid shear stress (FSS), compression, and microgravity play different roles in the cell differentiation and proliferation involved in bone remodeling. However, the underlying mechanisms are unclear, particularly the molecular pathways regulated by non-coding RNAs (ncRNAs) that play essential roles in bone remodeling. Amongst the various ncRNAs, miRNAs act as post-transcriptional regulators that inhibit the expression of their target genes. miRNAs are considered key regulators of many biologic processes including bone remodeling. Here, we review the role of miRNAs in mechanical force-induced bone metabolism.

Metformin ameliorates TGF-β1-induced osteoblastic differentiation of human aortic valve interstitial cells by inhibiting β-catenin signaling

Osteoblastic differentiation of aortic valve interstitial cells (AVICs) is the central process in the development of calcific aortic valve disease (CAVD). Metformin is a widely used first-line antidiabetic drug, and recently, pleiotropic benefits of metformin beyond hypoglycemia have been reported in the cardiovascular system. Here, we examined the effect of metformin on the osteoblastic differentiation of human AVICs. Our results showed that metformin ameliorated TGF-β1-induced production of osteogenic proteins Runx2 and osteopontin as well as calcium deposition in the cultured human AVICs. Experiments using AICAR, Compound C and AMPKα siRNA showed that the beneficial effect of metformin on TGF-β1-induced osteoblastic differentiation of human AVICs was mediated by AMPKα. Moreover, metformin inhibited the TGF-β1-induced activation of β-catenin, and β-catenin siRNA blocked TGF-β1-induced osteoblastic differentiation of AVICs. Smad2/3 and JNK were phosphorylated to promote the TGF-β1-induced activation of β-catenin and osteoblastic differentiation of AVICs, and metformin also alleviated TGF-β1-induced activation of Smad2/3 and JNK. In conclusion, our results suggest a beneficial effect of metformin based on the prevention of osteoblastic differentiation of human AVICs via inhibition of β-catenin, which indicates the therapeutic potential of metformin for CAVD.

Enlightening the Association between Bicuspid Aortic Valve and Aortopathy

Bicuspid aortic valve (BAV) patients have an increased incidence of developing aortic dilation. Despite its importance, the pathogenesis of aortopathy in BAV is still largely undetermined. Nowadays, intense focus falls both on BAV morphology and progression of valvular dysfunction and on the development of aortic dilation. However, less is known about the relationship between aortic valve morphology and aortic dilation. A better understanding of the molecular pathways involved in the homeostasis of the aortic wall, including the extracellular matrix, the plasticity of the vascular smooth cells, TGFβ signaling, and epigenetic dysregulation, is key to enlighten the mechanisms underpinning BAV-aortopathy development and progression. To date, there are two main theories on this subject, i.e., the genetic and the hemodynamic theory, with an ongoing debate over the pathogenesis of BAV-aortopathy. Furthermore, the lack of early detection biomarkers leads to challenges in the management of patients affected by BAV-aortopathy. Here, we critically review the current knowledge on the driving mechanisms of BAV-aortopathy together with the current clinical management and lack of available biomarkers allowing for early detection and better treatment optimization.

Cell Phenotype Transitions in Cardiovascular Calcification

Cardiovascular calcification was originally considered a passive, degenerative process, however with the advance of cellular and molecular biology techniques it is now appreciated that ectopic calcification is an active biological process. Vascular calcification is the most common form of ectopic calcification, and aging as well as specific disease states such as atherosclerosis, diabetes, and genetic mutations, exhibit this pathology. In the vessels and valves, endothelial cells, smooth muscle cells, and fibroblast-like cells contribute to the formation of extracellular calcified nodules. Research suggests that these vascular cells undergo a phenotypic switch whereby they acquire osteoblast-like characteristics, however the mechanisms driving the early aspects of these cell transitions are not fully understood. Osteoblasts are true bone-forming cells and differentiate from their pluripotent precursor, the mesenchymal stem cell (MSC); vascular cells that acquire the ability to calcify share aspects of the transcriptional programs exhibited by MSCs differentiating into osteoblasts. What is unknown is whether a fully-differentiated vascular cell directly acquires the ability to calcify by the upregulation of osteogenic genes or, whether these vascular cells first de-differentiate into an MSC-like state before obtaining a “second hit” that induces them to re-differentiate down an osteogenic lineage. Addressing these questions will enable progress in preventative and regenerative medicine strategies to combat vascular calcification pathologies. In this review, we will summarize what is known about the phenotypic switching of vascular endothelial, smooth muscle, and valvular cells.

Overexpression of tissue-nonspecific alkaline phosphatase (TNAP) in endothelial cells accelerates coronary artery disease in a mouse model of familial hypercholesterolemia

OBJECTIVE

Overexpression of tissue-nonspecific alkaline phosphatase (TNAP) in endothelium leads to arterial calcification in mice. The purpose of this study was to examine the effect of elevated endothelial TNAP on coronary atherosclerosis. In addition, we aimed to examine endogenous TNAP activity in human myocardium.

APPROACH AND RESULTS

A vascular pattern of TNAP activity was observed in human non-failing, ischemic, and idiopathic dilated hearts (5 per group); no differences were noted between groups in this study. Endothelial overexpression of TNAP was achieved in mice harboring a homozygous recessive mutation in the low density lipoprotein receptor (whc allele) utilizing a Tie2-cre recombinase (WHC-eTNAP mice). WHC-eTNAP developed significant coronary artery calcification at baseline compared WHC controls (4312 vs 0μm2 alizarin red area, p<0.001). Eight weeks after induction of atherosclerosis, lipid deposition in the coronary arteries of WHC-eTNAP was increased compared to WHC controls (121633 vs 9330μm2 oil red O area, p<0.05). Coronary lesions in WHC-eTNAP mice exhibited intimal thickening, calcifications, foam cells, and necrotic cores. This was accompanied by the reduction in body weight and left ventricular ejection fraction (19.5 vs. 23.6g, p<0.01; 35% vs. 47%, p<0.05). In a placebo-controlled experiment under atherogenic conditions, pharmacological inhibition of TNAP in WHC-eTNAP mice by a specific inhibitor SBI-425 (30mg*kg-1*d-1, for 5 weeks) reduced coronary calcium (78838 vs.144622μm2) and lipids (30754 vs. 77317μm2); improved body weight (22.4 vs.18.8g) and ejection fraction (59 vs. 47%). The effects of SBI-425 were significant in the direct comparisons with placebo but disappeared after TNAP-negative placebo-treated group was included in the models as healthy controls.

CONCLUSIONS

Endogenous TNAP activity is present in human cardiac tissues. TNAP overexpression in vascular endothelium in mice leads to an unusual course of coronary atherosclerosis, in which calcification precedes lipid deposition. The prevalence and significance of this mechanism in human atherosclerosis requires further investigations.