Notch1 promotes the pro-osteogenic response of human aortic valve interstitial cells via modulation of ERK1/2 and nuclear factor-κB activation

Thrombospondin-1 Silencing Ameliorates Osteoblastic Differentiation of Aortic Valve Interstitial Cells via Inhibiting Nuclear Factor-κB Pathway

Objective: Calcific aortic valve disease (CAVD) is a progressive cardiovascular condition driven by the osteogenic differentiation of valve interstitial cells (VICs), with no effective drug therapies currently available. Hence, our objective is to investigate the impact of thrombospondin-1 (TSP-1) silencing on CAVD progression. Methods: In vitro experiments were employed using human primary VICs with TSP-1 knockdown, cultured in osteogenic induction medium, and followed by analyses including western blot, alkaline phosphatase staining, alizarin red staining, immunofluorescence, and flow cytometry. In vivo experiments used two murine models of CAVD to determine the role of TSP-1 silencing on aortic valve calcification. Results: We observed that silencing of TSP-1 reduced the osteogenic differentiation of VICs. Subsequent experiments demonstrated that TSP-1 knockdown suppressed nuclear factor-κB (NF-κB)-mediated inflammation during osteoblastic differentiation of VICs. Consistent findings were also observed in two murine models of CAVD. Conclusions: The present study has shown that TSP-1 silencing could mitigate the development of CAVD by inhibiting NF-κB-mediated inflammation. We propose that targeting TSP-1-mediated NF-κB pathway could provide a potential therapeutic method for treating CAVD.

Collagen-mediated cardiovascular calcification

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

Advances in Pathophysiological Mechanisms of Degenerative Aortic Valve Disease

Degenerative aortic valve disease (DAVD) represents the most prevalent valvular ailment among the elderly population, which significantly impacts their physical well-being and potentially poses a lethal risk. Currently, the underlying mechanisms of DAVD remain incompletely understood. While the progression of this disease has traditionally been attributed to degenerative processes associated with aging, numerous recent studies have revealed that heart valve calcification may represent a response of valve tissue to a specific initiating factor, involving the interaction of various genes and signaling pathways. This calcification process is further influenced by a range of factors, including genetic predispositions, environmental exposures, metabolic factors, and hemodynamic considerations. Based on the identification of its biomarkers, potential innovative therapeutic targets are proposed for the treatment of this complex condition. The present article primarily delves into the underlying pathophysiological mechanisms and advancements in diagnostic and therapeutic modalities pertaining to this malady.

Influence of Aortic Valve Stenosis and Wall Shear Stress on Platelets Function

Aortic valve stenosis (AS) is a common heart valve disease in the elderly population, and its pathogenesis remains an interesting area of research. The degeneration of the aortic valve leaflets gradually progresses to valve sclerosis. The advanced phase is marked by the presence of extracellular fibrosis and calcification. Turbulent, accelerated blood flow generated by the stenotic valve causes excessive damage to the aortic wall. Elevated shear stress due to AS leads to the degradation of high-molecular weight multimers of von Willebrand factor, which may involve bleeding in the mucosal tissues. Conversely, elevated shear stress has been associated with the release of thrombin and the activation of platelets, even in individuals with acquired von Willebrand syndrome. Moreover, turbulent blood flow in the aorta may activate the endothelium and promote platelet adhesion and activation on the aortic valve surface. Platelets release a wide range of mediators, including lysophosphatidic acid, which have pro-osteogenic effects in AS. All of these interactions result in blood coagulation, fibrinolysis, and the hemostatic process. This review summarizes the current knowledge on high shear stress-induced hemostatic disorders, the influence of AS on platelets and antiplatelet therapy.

Overexpression of microRNA-93-5p and microRNA-374a-5p Suppresses the Osteogenic Differentiation and Mineralization of Human Aortic Valvular Interstitial Cells Through the BMP2/Smad1/5/RUNX2 Signaling Pathway

ABSTRACT

Aortic valve calcification commonly occurs in patients with chronic kidney disease (CKD). However, the regulatory functions of microRNAs (miRNAs/miRs) in the osteogenic differentiation of human aortic valvular interstitial cells (hAVICs) in patients with CKD remain largely unknown. This study aimed to explore the functional role and underlying mechanisms of miR-93-5p and miR-374a-5p in the osteogenic differentiation of hAVICs. For this purpose, hAVICs calcification was induced with high-calcium/high-phosphate medium and the expression levels of miR-93-5p and miR-374a-5p were determined using bioinformatics assay. Alizarin red staining, intracellular calcium content, and alkaline phosphatase activity were used to evaluate calcification. The expression levels of bone morphogenetic protein-2 (BMP2), runt-related transcription factor 2 (Runx2), and phosphorylated (p)-Smad1/5 were detected by luciferase reporter assay, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and western blot analysis. The results revealed that the expression levels of miR-93-5p and miR-374a-5p were significantly decreased in hAVICs in response to high-calcium/high-phosphate medium. The overexpression of miR-93-5p and miR-374a-5p effectively suppressed the high-calcium/high-phosphate-induced calcification and osteogenic differentiation makers. Mechanistically, the overexpression of miR-93-5p and miR-374a-5p inhibits osteogenic differentiation by regulating the BMP2/Smad1/5/Runx2 signaling pathway. Taken together, this study indicates that miR-93-5p and miR-374a-5p suppress the osteogenic differentiation of hAVICs associated with calcium-phosphate metabolic dyshomeostasis through the inhibition of the BMP2/Smad1/5/Runx2 signaling pathway.

Identification of TNFα-mediated inflammation as potential pathological marker and therapeutic target for calcification progress of congenital bicuspid aortic valve

BACKGROUD

Congenital bicuspid aortic valve (cBAV) develops calcification and stenotic obstruction early compared with degenerative tricuspid aortic valve (dTAV), which requires surgical intervention. Here we report a comparative study of patients with cBAV or dTAV to identify risk factors associated with the rapid development of calcified bicuspid valves.

METHODS

A total of 69 aortic valves (24 dTAV and 45 cBAV) were collected at the time of surgical aortic valve replacement for comparative clinical characteristics. Ten samples were randomly selected from each group for histology, pathology, and inflammatory factors expression and comparison analyses. OM-induced calcification in porcine aortic valve interstitial cell cultures were prepared for illustrating the underlying molecular mechanisms about calcification progress of cBAV and dTAV.

RESULTS

We found that cBAV patients have increased cases of aortic valve stenosis compared with dTAV patients. Histopathological examinations revealed increased collagens deposition, neovascularization and infiltrations by inflammatory cells, especially T-lymphocytes and macrophages. We identified that tumor necrosis factor α (TNFα) and its regulated inflammatory cytokines are upregulated in cBAV. Further in vitro study indicated that TNFα-NFκB and TNFα-GSK3β pathway accelerate aortic valve interstitial cells calcification, while inhibition of TNFα significantly delays this process.

CONCLUSION

The finding of intensified TNFα-mediated inflammation in the pathological cBAV advocates the inhibition of TNFα as a potential treatment for patients with cBAV by alleviating the progress of inflammation-induced valve damage and calcification.

Toll-Like Receptor 4 (TLR4) and AMPK Relevance in Cardiovascular Disease

Toll-like receptors (TLRs) are essential receptors of the innate immune system, playing a significant role in cardiovascular diseases. TLR4, with the highest expression among TLRs in the heart, has been investigated extensively for its critical role in different myocardial inflammatory conditions. Studies suggest that inhibition of TLR4 signaling pathways reduces inflammatory responses and even prevents additional injuries to the already damaged myocardium. Recent research results have led to a hypothesis that there may be a relation between TLR4 expression and 5' adenosine monophosphate-activated protein kinase (AMPK) signaling in various inflammatory conditions, including cardiovascular diseases. AMPK, as a cellular energy sensor, has been reported to show anti-inflammatory effects in various models of inflammatory diseases. AMPK, in addition to its physiological acts in the heart, plays an essential role in myocardial ischemia and hypoxia by activating various energy production pathways. Herein we will discuss the role of TLR4 and AMPK in cardiovascular diseases and a possible relation between TLRs and AMPK as a novel therapeutic target. In our opinion, AMPK-related TLR modulators will find application in treating different immune-mediated inflammatory disorders, especially inflammatory cardiac diseases, and present an option that will be widely used in clinical practice in the future.

Effects of the interaction of Notch and TLR4 pathways on inflammation and heart function in septic heart

We investigated the role of the interaction between the Notch and Toll-like receptor 4 (TLR4) pathways in septic myocardial injury. The sepsis model was induced in rats with lipopolysaccharide (LPS). Rats were divided into control, LPS, LPS + TAK242 ((6R)-6-[N-(2-chloro-4-fluorophenyl)sulfamoyl]cyclohex-1-ene-1-carboxylate) and LPS + DAPT (N-[N-(3,5-difluorophenacetyl)-l-alanyl]-s-phenylglycinetbutylester) groups. Heart function was evaluated with a Cardiac Doppler ultrasound. Myocardial morphological changes were detected by hematoxylin-eosin staining (H&E). Apoptosis was assessed by a TUNEL assay. The mRNA and protein levels were detected with real-time PCR, Western blot, and immunohistochemistry analysis. We found that heart function in the LPS + TAK242 group was significantly improved, but not in the LPS + DAPT group. LPS + TAK242 had a lower level of degeneration and necrosis of cardiomyocytes and inflammatory cell infiltration, as well as lower apoptosis and caspase-3 expression than the LPS group. Compared with the LPS group, the inflammatory cell infiltration was reduced in the LPS + DAPT group, while the degeneration and necrosis of cardiomyocytes were not obviously improved. Additionally, the expression levels of tumor necrosis factor-α and Interleukin-6, the protein contents of Notch intracellular domain and Hes1, and the P65 nuclear factor kappa-B (NF-κB) to P-P65 NF-κB ratio in LPS + TAK242 group and LPS + DAPT group were significantly lower than those in LPS group. Conclusively, the interaction between TLR4 and Notch signaling pathways enhances the inflammatory response in the septic heart by activating NF-κB. Blocking the TLR4 pathway with TAK242 can improve heart dysfunction and myocardial damage in sepsis, while blocking the Notch pathway with DAPT cannot effectively prevent heart dysfunction and myocardial damage in sepsis.

Role of oxidative stress in calcific aortic valve disease and its therapeutic implications

Calcific aortic valve disease (CAVD) is the end result of active cellular processes that lead to the progressive fibrosis and calcification of aortic valve leaflets. In western populations, CAVD is a significant cause of cardiovascular morbidity and mortality, and in the absence of effective drugs, it will likely represent an increasing disease burden as populations age. As there are currently no pharmacological therapies available for preventing, treating, or slowing the development of CAVD, understanding the mechanisms underlying the initiation and progression of the disease is important for identifying novel therapeutic targets. Recent evidence has emerged of an important causative role for reactive oxygen species (ROS)-mediated oxidative stress in the pathophysiology of CAVD, inducing the differentiation of valve interstitial cells into myofibroblasts and then osteoblasts. In this review, we focus on the roles and sources of ROS driving CAVD and consider their potential as novel therapeutic targets for this debilitating condition.

Monocytes augment inflammatory responses in human aortic valve interstitial cells via β2-integrin/ICAM-1-mediated signaling

OBJECTIVE

Inflammatory infiltration in aortic valves promotes calcific aortic valve disease (CAVD) progression. While soluble extracellular matrix (ECM) proteins induce inflammatory responses in aortic valve interstitial cells (AVICs), the impact of monocytes on AVIC inflammatory responses is unknown. We tested the hypothesis that monocytes enhance AVIC inflammatory responses to soluble ECM protein in this study.

METHODS

Human AVICs isolated from normal aortic valves were cocultured with monocytes and stimulated with soluble ECM protein (matrilin-2). ICAM-1 and IL-6 productions were assessed. YAP and NF-κB phosphorylation were analyzed. Recombinant CD18, neutralizing antibodies against β₂-integrin or ICAM-1, and inhibitor of YAP or NF-κB were applied.

RESULTS

AVIC expression of ICAM-1 and IL-6 was markedly enhanced by the presence of monocytes, although matrilin-2 did not affect monocyte production of ICAM-1 or IL-6. Matrilin-2 up-regulated the expression of monocyte β₂-integrin and AVIC ICAM-1, leading to monocyte-AVIC adhesion. Neutralizing β₂-integrin or ICAM-1 in coculture suppressed monocyte adhesion to AVICs and the expression of ICAM-1 and IL-6. Recombinant CD18 enhanced the matrilin-2-induced ICAM-1 and IL-6 expression in AVIC monoculture. Further, stimulation of coculture with matrilin-2 induced greater YAP and NF-κB phosphorylation. Inhibiting either YAP or NF-κB markedly suppressed the inflammatory response to matrilin-2 in coculture.

CONCLUSION

Monocyte β₂-integrin interacts with AVIC ICAM-1 to augment AVIC inflammatory responses to soluble matrilin-2 through enhancing the activation of YAP and NF-κB signaling pathways. Infiltrated monocytes may promote valvular inflammation through cell-cell interaction with AVICs to enhance their sensitivity to damage-associated molecular patterns.

Uncoupling the Vicious Cycle of Mechanical Stress and Inflammation in Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) is a common acquired valvulopathy, which carries a high burden of mortality. Chronic inflammation has been postulated as the predominant pathophysiological process underlying CAVD. So far, no effective medical therapies exist to halt the progression of CAVD. This review aims to outline the known pathways of inflammation and calcification in CAVD, focussing on the critical roles of mechanical stress and mechanosensing in the perpetuation of valvular inflammation. Following initiation of valvular inflammation, dysregulation of proinflammatory and osteoregulatory signalling pathways stimulates endothelial-mesenchymal transition of valvular endothelial cells (VECs) and differentiation of valvular interstitial cells (VICs) into active myofibroblastic and osteoblastic phenotypes, which in turn mediate valvular extracellular matrix remodelling and calcification. Mechanosensitive signalling pathways convert mechanical forces experienced by valve leaflets and circulating cells into biochemical signals and may provide the positive feedback loop that promotes acceleration of disease progression in the advanced stages of CAVD. Mechanosensing is implicated in multiple aspects of CAVD pathophysiology. The mechanosensitive RhoA/ROCK and YAP/TAZ systems are implicated in aortic valve leaflet mineralisation in response to increased substrate stiffness. Exposure of aortic valve leaflets, endothelial cells and platelets to high shear stress results in increased expression of mediators of VIC differentiation. Upregulation of the Piezo1 mechanoreceptor has been demonstrated to promote inflammation in CAVD, which normalises following transcatheter valve replacement. Genetic variants and inhibition of Notch signalling accentuate VIC responses to altered mechanical stresses. The study of mechanosensing pathways has revealed promising insights into the mechanisms that perpetuate inflammation and calcification in CAVD. Mechanotransduction of altered mechanical stresses may provide the sought-after coupling link that drives a vicious cycle of chronic inflammation in CAVD. Mechanosensing pathways may yield promising targets for therapeutic interventions and prognostic biomarkers with the potential to improve the management of CAVD.

Network modeling predicts personalized gene expression and drug responses in valve myofibroblasts cultured with patient sera

Aortic valve stenosis (AVS) patients experience pathogenic valve leaflet stiffening due to excessive extracellular matrix (ECM) remodeling. Numerous microenvironmental cues influence pathogenic expression of ECM remodeling genes in tissue-resident valvular myofibroblasts, and the regulation of complex myofibroblast signaling networks depends on patient-specific extracellular factors. Here, we combined a manually curated myofibroblast signaling network with a data-driven transcription factor network to predict patient-specific myofibroblast gene expression signatures and drug responses. Using transcriptomic data from myofibroblasts cultured with AVS patient sera, we produced a large-scale, logic-gated differential equation model in which 11 biochemical and biomechanical signals were transduced via a network of 334 signaling and transcription reactions to accurately predict the expression of 27 fibrosis-related genes. Correlations were found between personalized model-predicted gene expression and AVS patient echocardiography data, suggesting links between fibrosis-related signaling and patient-specific AVS severity. Further, global network perturbation analyses revealed signaling molecules with the most influence over network-wide activity, including endothelin 1 (ET1), interleukin 6 (IL6), and transforming growth factor β (TGFβ), along with downstream mediators c-Jun N-terminal kinase (JNK), signal transducer and activator of transcription (STAT), and reactive oxygen species (ROS). Lastly, we performed virtual drug screening to identify patient-specific drug responses, which were experimentally validated via fibrotic gene expression measurements in valvular interstitial cells cultured with AVS patient sera and treated with or without bosentan-a clinically approved ET1 receptor inhibitor. In sum, our work advances the ability of computational approaches to provide a mechanistic basis for clinical decisions including patient stratification and personalized drug screening.

MiR-138-5p targets RUNX2 to inhibit osteogenic differentiation of aortic valve interstitial cells via Wnt/β-catenin signaling pathway

Background

Human aortic valve interstitial cells (hAVICs) are a key factor in the pathogenesis of calcific aortic valve disease (CAVD). This research examines the role and mechanism of microRNA miR-138-5p in osteogenic differentiation of hAVICs.

Methods

RT-qPCR analysis was applied for detecting miR-138-5p and RUNX2 expression in valve tissues of CAVD patients and controls. On completion of induction of osteogenic differentiation of hAVICs, and after overexpression or interference of miR-138-5p expression, the condition of osteogenic differentiation and calcification of hAVICs was confirmed using alkaline phosphatase staining and alizarin red staining. Subsequently, western blot was utilized to detect the expression of osteogenesis-related proteins OPN and ALP, and Wnt/β-catenin signaling pathway-related proteins. Finally, the relationship between miR-138-5p and RUNX2 was validated by dual-luciferase reporter assay and Pearson’s correlation test.

Results

Down-regulation of miR-138-5p was found in CAVD patients and during osteogenic differentiation of hAVICs. Overexpression of miR-138-5p contribute to the inhibition of osteoblast differentiation and calcium deposition in hAVICs, and of ALP and OPN protein expression. RUNX2 was a target gene of miR-138-5p, and it was negatively correlated with miR-138-5p in CAVD. Additionally, overexpression of RUNX2 could reverse the inhibitory effect of miR-138-5p on osteogenic differentiation of hAVICs.

Conclusion

miR-138-5p can act as a positive regulator of osteogenic differentiation in CAVD patients to involve in inhibiting valve calcification, which is achieved through RUNX2 and Wnt/β-catenin signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02471-6.

Lipoprotein (a)-mediated vascular calcification: population-based and in vitro studies

BACKGROUND

Lipoprotein (a) [Lp(a)] is a causal risk factor for cardiovascular diseases, while its role in vascular calcification has not been well-established. Here, we investigated an association of Lp(a) with vascular calcification using population-based and in vitro study designs.

METHODS

A total of 2806 patients who received coronary computed tomography were enrolled to assess the correlation of Lp(a) with the severity of coronary artery calcification (CAC). Human aortic smooth muscle cells (HASMCs) were used to explore mechanisms of Lp(a)-induced vascular calcification.

RESULTS

In the population study, Lp(a) was independently correlated with the presence and severity of CAC (all p < 0.05). In vitro study showed that cell calcific depositions and alkaline phosphatase (ALP) activity were increased and the expression of pro-calcific proteins, including bone morphogenetic protein-2 (BMP2) and osteopontin (OPN), were up-regulated by Lp(a) stimulation. Interestingly, Lp(a) activated Notch1 signaling, resulting in cell calcification, which was inhibited by the Notch1 signaling inhibitor, DAPT. Lp(a)-induced Notch1 activation up-regulated BMP2-Smad1/5/9 pathway. In contrast, Noggin, an inhibitor of BMP2-Smad1/5/9 pathway, significantly blocked Lp(a)-induced HASMC calcification. Notch1 activation also induced translocation of nuclear factor-κB (NF-κB) accompanied by OPN overexpression and elevated inflammatory cytokines production, while NF-κB silencing alleviated Lp(a)-induced vascular calcification.

CONCLUSIONS

Elevated Lp(a) concentrations are independently associated with the presence and severity of CAC and the impact of Lp(a) on vascular calcification is involved in the activation of Notch1-NF-κB and Notch1-BMP2-Smad1/5/9 pathways, thus implicating Lp(a) as a potential novel therapeutic target for vascular calcification.

Midkine Prevents Calcification of Aortic Valve Interstitial Cells via Intercellular Crosstalk

Calcified aortic valve disease (CAVD), the most common valvular heart disease, lacks pharmaceutical treatment options because its pathogenesis remains unclear. This disease with a complex macroenvironment characterizes notable cellular heterogeneity. Therefore, a comprehensive understanding of cellular diversity and cell-to-cell communication are essential for elucidating the mechanisms driving CAVD progression and developing therapeutic targets. In this study, we used single-cell RNA sequencing (scRNA-seq) analysis to describe the comprehensive transcriptomic landscape and cell-to-cell interactions. The transitional valvular endothelial cells (tVECs), an intermediate state during the endothelial-to-mesenchymal transition (EndMT), could be a target to interfere with EndMT progression. Moreover, matrix valvular interstitial cells (mVICs) with high expression of midkine (MDK) interact with activated valvular interstitial cells (aVICs) and compliment-activated valvular interstitial cells (cVICs) through the MK pathway. Then, MDK inhibited calcification of VICs that calcification was validated by Alizarin Red S staining, real-time quantitative polymerase chain reaction (RT-qPCR), and Western blotting assays in vitro. Therefore, we speculated that mVICs secreted MDK to prevent VICs’ calcification. Together, these findings delineate the aortic valve cells’ heterogeneity, underlining the importance of intercellular cross talk and MDK, which may offer a potential therapeutic strategy as a novel inhibitor of CAVD.

Adding a "Notch" to Cardiovascular Disease Therapeutics: A MicroRNA-Based Approach

Dysregulation of the Notch pathway is implicated in the pathophysiology of cardiovascular diseases (CVDs), but, as of today, therapies based on the re-establishing the physiological levels of Notch in the heart and vessels are not available. A possible reason is the context-dependent role of Notch in the cardiovascular system, which would require a finely tuned, cell-specific approach. MicroRNAs (miRNAs) are short functional endogenous, non-coding RNA sequences able to regulate gene expression at post-transcriptional levels influencing most, if not all, biological processes. Dysregulation of miRNAs expression is implicated in the molecular mechanisms underlying many CVDs. Notch is regulated and regulates a large number of miRNAs expressed in the cardiovascular system and, thus, targeting these miRNAs could represent an avenue to be explored to target Notch for CVDs. In this Review, we provide an overview of both established and potential, based on evidence in other pathologies, crosstalks between miRNAs and Notch in cellular processes underlying atherosclerosis, myocardial ischemia, heart failure, calcification of aortic valve, and arrhythmias. We also discuss the potential advantages, as well as the challenges, of using miRNAs for a Notch-based approach for the diagnosis and treatment of the most common CVDs.

Trimethylamine -N-oxide induces osteogenic responses in human aortic valve interstitial cells in vitro and aggravates aortic valve lesions in mice

AIMS

Recent studies have shown that the choline-derived metabolite trimethylamine N-oxide (TMAO) is a biomarker that promotes cardiovascular disease through the induction of inflammation and stress. Inflammatory responses and stress are involved in the progression of calcified aortic valve disease (CAVD). Here, we examined whether TMAO induces the osteogenic differentiation of aortic valve interstitial cells (AVICs) through endoplasmic reticulum (ER) and mitochondrial stress pathways in vitro and in vivo.

METHODS AND RESULTS

Plasma TMAO levels were higher in patients with CAVD (n = 69) than in humans without CAVD (n = 263), as examined by liquid chromatography-tandem mass spectrometry. Western blot and staining probes showed that TMAO- induced an osteogenic response in human AVICs. Moreover, TMAO promoted ER stress, mitochondrial stress and NF-κB activation in vitro. Notably, the TMAO- mediated effects were reversed by the use of ER stress, mitochondrial stress and NF-κB activation inhibitors and siRNA. Mice treated with supplemental choline in a high fat diet had markedly increased TMAO levels and aortic valve thicknesses, which were reduced by 3,3-dimethyl-1-butanol (DMB, an inhibitor of trimethylamine formation) treatment.

CONCLUSIONS

Choline-derived TMAO promotes osteogenic differentiation through ER and mitochondrial stress pathways in vitro and aortic valve lesions in vivo.

TRANSLATIONAL PERSPECTIVE

Trimethylamine-N-oxide (TMAO), a gut microbiota-generated metabolite, is associated with cardiovascular diseases. Here, we show that patients with calcified aortic valve disease (CAVD) have elevated circulating TMAO levels. TMAO induces osteogenic responses in human aortic valve interstitial cells via endoplasmic reticulum-mitochondrial stress in vitro and aggravates aortic valve lesions in mice. This may provide clues to the pathogenesis of CAVD and attractive potential targets for the prevention, diagnosis and treatment of this disease.

Tumor necrosis factor-α promotes and exacerbates calcification in heart valve myofibroblast populations

Pro-inflammatory cytokines play critical roles in regulating valvular interstitial cell (VIC) phenotypic changes that can cause heart valve fibrosis and calcification. Tumor necrosis factor alpha (TNF-α) is a cytokine known to influence VIC behavior and has been reported at high levels in calcified valves ex vivo. We sought to understand the specific effects of TNF-α on VIC phenotypes (eg, fibroblast, profibrotic activated myofibroblasts) and its link with heart valve disorders. We characterize human aortic valve tissue from patients with valve disorders and identify a high variability of fibrotic and calcific markers between tissues. These results motivated in vitro studies to explore the effects of TNF-α on defined VIC fibroblasts and profibrotic activated myofibroblasts, induced via FGF-2 and TGF-β1 treatment. Using 3D hydrogels to culture VICs, we measure the effect of TNF-α (0.1-10 ng/mL) on key markers of fibrosis (eg, αSMA, COL1A1) and calcification (eg, RUNX2, BMP2, and calcium deposits). We observe calcification in TNF-α-treated VIC activated myofibroblasts and identify the MAPK/ERK signaling cascade as a potential pathway for TNF-α mediated calcification. Conversely, VIC fibroblasts respond to TNF-α with decreased calcification. Treatment of VIC profibrotic activated myofibroblast populations with TNF-α leads to increased calcification. Our in vitro findings correlate with findings in diseased human valves and highlight the importance of understanding the effect of cytokines and signaling pathways on specific VIC phenotypes. Finally, we reveal MAPK/ERK as a potential pathway involved in VIC-mediated matrix calcification with TNF-α treatment, suggesting this pathway as a potential pharmaceutical target for aortic valve disease.

Inflammatory and Biomechanical Drivers of Endothelial-Interstitial Interactions in Calcific Aortic Valve Disease

Calcific aortic valve disease is dramatically increasing in global burden, yet no therapy exists outside of prosthetic replacement. The increasing proportion of younger and more active patients mandates alternative therapies. Studies suggest a window of opportunity for biologically based diagnostics and therapeutics to alleviate or delay calcific aortic valve disease progression. Advancement, however, has been hampered by limited understanding of the complex mechanisms driving calcific aortic valve disease initiation and progression towards clinically relevant interventions.

Age related extracellular matrix and interstitial cell phenotype in pulmonary valves

Heart valve disease is a common manifestation of cardiovascular disease and is a significant cause of cardiovascular morbidity and mortality worldwide. The pulmonary valve (PV) is of primary concern because of its involvement in common congenital heart defects, and the PV is usually the site for prosthetic replacement following a Ross operation. Although effects of age on valve matrix components and mechanical properties for aortic and mitral valves have been studied, very little is known about the age-related alterations that occur in the PV. In this study, we isolated PV leaflets from porcine hearts in different age groups (~ 4-6 months, denoted as young versus ~ 2 years, denoted as adult) and studied the effects of age on PV leaflet thickness, extracellular matrix components, and mechanical properties. We also conducted proteomics and RNA sequencing to investigate the global changes of PV leaflets and passage zero PV interstitial cells in their protein and gene levels. We found that the size, thickness, elastic modulus, and ultimate stress in both the radial and circumferential directions and the collagen of PV leaflets increased from young to adult age, while the ultimate strain and amount of glycosaminoglycans decreased when age increased. Young and adult PV had both similar and distinct protein and gene expression patterns that are related to their inherent physiological properties. These findings are important for us to better understand the physiological microenvironments of PV leaflet and valve cells for correctively engineering age-specific heart valve tissues.

Role of TLR4 in physical exercise and cardiovascular diseases

Cardiovascular diseases are a leading cause of death for adults worldwide. Published articles have shown that toll-like receptor 4 (TLR4), a member of the toll-like receptor (TLR) family, is involved in several cardiovascular diseases and can be modulated by physical exercise. TLR4 is the most expressed TLR in cardiac tissue and is an essential mediator of the inflammatory and apoptosis processes in the heart, playing a pivotal role in the development of cardiovascular diseases. Physical exercise is recognized as a non-pharmacological strategy for the prevention and treatment of these diseases. In addition, physical exercise can modulate the TLR4 in the mice heart, and its absence attenuates apoptosis, endoplasmic reticulum stress, and inflammation. However, the relationship between TLR4 and physical exercise-induced cardiac adaptations has barely been explored. Thus, the objective of this brief review was to discuss studies describing how TLR4 influences cardiac responses to physical exercise and present a link between these responses and cardiovascular diseases, showing physical activity improves the cardiac function of individuals with cardiovascular diseases through the TLR4 modulation.

Precision and Personalized Medicine: How Genomic Approach Improves the Management of Cardiovascular and Neurodegenerative Disease

Life expectancy has gradually grown over the last century. This has deeply affected healthcare costs, since the growth of an aging population is correlated to the increasing burden of chronic diseases. This represents the interesting challenge of how to manage patients with chronic diseases in order to improve health care budgets. Effective primary prevention could represent a promising route. To this end, precision, together with personalized medicine, are useful instruments in order to investigate pathological processes before the appearance of clinical symptoms and to guide physicians to choose a targeted therapy to manage the patient. Cardiovascular and neurodegenerative diseases represent suitable models for taking full advantage of precision medicine technologies applied to all stages of disease development. The availability of high technology incorporating artificial intelligence and advancement progress made in the field of biomedical research have been substantial to understand how genes, epigenetic modifications, aging, nutrition, drugs, microbiome and other environmental factors can impact health and chronic disorders. The aim of the present review is to address how precision and personalized medicine can bring greater clarity to the clinical and biological complexity of these types of disorders associated with high mortality, involving tremendous health care costs, by describing in detail the methods that can be applied. This might offer precious tools for preventive strategies and possible clues on the evolution of the disease and could help in predicting morbidity, mortality and detecting chronic disease indicators much earlier in the disease course. This, of course, will have a major effect on both improving the quality of care and quality of life of the patients and reducing time efforts and healthcare costs.

TLR4 Stimulation Promotes Human AVIC Fibrogenic Activity through Upregulation of Neurotrophin 3 Production

BACKGROUND

Calcific aortic valve disease (CAVD) is a chronic inflammatory disease that manifests as progressive valvular fibrosis and calcification. An inflammatory milieu in valvular tissue promotes fibrosis and calcification. Aortic valve interstitial cell (AVIC) proliferation and the over-production of the extracellular matrix (ECM) proteins contribute to valvular thickening. However, the mechanism underlying elevated AVIC fibrogenic activity remains unclear. Recently, we observed that AVICs from diseased aortic valves express higher levels of neurotrophin 3 (NT3) and that NT3 exerts pro-osteogenic and pro-fibrogenic effects on human AVICs.

HYPOTHESIS

Pro-inflammatory stimuli upregulate NT3 production in AVICs to promote fibrogenic activity in human aortic valves.

METHODS AND RESULTS

AVICs were isolated from normal human aortic valves and were treated with lipopolysaccharide (LPS, 0.20 µg/mL). LPS induced TLR4-dependent NT3 production. This effect of LPS was abolished by inhibition of the Akt and extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) pathways. The stimulation of TLR4 in human AVICs with LPS resulted in a greater proliferation rate and an upregulated production of matrix metallopeptidases-9 (MMP-9) and collagen III, as well as augmented collagen deposition. Recombinant NT3 promoted AVIC proliferation in a tropomyosin receptor kinase (Trk)-dependent fashion. The neutralization of NT3 or the inhibition of Trk suppressed LPS-induced AVIC fibrogenic activity.

CONCLUSIONS

The stimulation of TLR4 in human AVICs upregulates NT3 expression and promotes cell proliferation and collagen deposition. The NT3-Trk cascade plays a critical role in the TLR4-mediated elevation of fibrogenic activity in human AVICs. Upregulated NT3 production by endogenous TLR4 activators may contribute to aortic valve fibrosis associated with CAVD progression.

Interleukin 37 Suppresses M1 Macrophage Polarization Through Inhibition of the Notch1 and Nuclear Factor Kappa B Pathways

Macrophage-orchestrated chronic inflammation plays an important role in cardiovascular disease, including accelerating the development of calcific aortic valve disease (CAVD). M1 and M2 macrophage polarization imbalances can alter intensity of inflammatory responses. Recombinant human interleukin 37 (IL-37) could be involved in regulating immune cell function to attenuate inflammation. This study aimed to identify IL-37 specifically modulates M1 polarization and investigate the underlying mechanism. Compared with normal valves, there are more M1 macrophages accumulation and less IL-37 expression in calcific aortic valves, which may indicate a negative relationship between IL-37 and M1 polarization. THP-1 cells could differentiate into resting macrophages with phorbol-12-myristate-13-acetate (PMA) and then polarize into M1 macrophages following treatment with lipopolysaccharide (LPS) and interferon gamma (IFN-γ). In vitro, recombinant human IL-37 attenuated the expression of inducible nitric oxide synthase (iNOS), CD11c, IL-6 and monocyte chemoattractant protein 1 (MCP-1) in M1 but augmented the expression of CD206 and IL-10 in M2. The suppression of M1 polarization was associated with the inhibition of the activation of the nuclear factor kappa B (NF-κB) and Notch1 signaling pathways. These results demonstrated that IL-37 inhibits the macrophages polarizing into M1 type via the inhibition of the Notch1 and nuclear factor kappa B pathways. In summary, IL-37 could be a potential therapeutic candidate for progressive CAVD by modulating M1 polarization and its orchestrated inflammation.

Deregulation of TLR4 signaling pathway characterizes Bicuspid Aortic valve syndrome

Bicuspid aortic valve (BAV) disease is recognized to be a syndrome with a complex and multifaceted pathophysiology. Its progression is modulated by diverse evolutionary conserved pathways, such as Notch-1 pathway. Emerging evidence is also highlighting the key role of TLR4 signaling pathway in the aortic valve pathologies and their related complications, such as sporadic ascending aorta aneurysms (AAA). Consistent with these observations, we aimed to evaluate the role of TLR4 pathway in both BAV disease and its common complication, such as AAA. To this aim, 70 subjects with BAV (M/F 50/20; mean age: 58.8 ± 14.8 years) and 70 subjects with tricuspid aortic valve (TAV) (M/F 35/35; mean age: 69.1 ± 12.8 years), with and without AAA were enrolled. Plasma assessment, tissue and gene expression evaluations were performed. Consistent with data obtained in the previous study on immune clonotypic T and B altered responses, we found reduced levels of systemic TNF-α, IL-1, IL-6, IL-17 cytokines in BAV cases, either in the presence or absence of AAA, than TAV cases (p < 0.0001 by ANOVA test). Interestingly, we also detected reduced levels of s-TLR4 in BAV cases with or without AAA in comparison to the two groups of TAV subjects (p < 0.0001 by ANOVA test). These results may suggest a deregulation in the activity or in the expression of TLR4 signaling pathway in all BAV cases. Portrait of these data is, indeed, the significantly decreased gene expression of inflammatory cytokines and TLR4, in both normal and aneurysmatic tissue samples, from BAV with AAA than TAV with AAA. In conclusion, our study demonstrates that subjects with BAV display a significant deregulation of TLR4 signaling pathway paralleled by a deregulation of Notch-1 pathway, as previously showed. This data suggests that the crosstalk between the Notch-1 and TLR4 signaling pathways may play a crucial role in both physiological embryological development, and homeostasis and functionality of aortic valve in adult life.

The Notch pathway: a novel therapeutic target for cardiovascular diseases?

Introduction: The Notch pathway is involved in determining cell fate during development and postnatally in continuously renewing tissues, such as the endothelium, the epithelium, and in the stem cells pool. The dysregulation of the Notch pathway is one of the causes of limited response, or resistance, to available cancer treatments and novel therapeutic strategies based on Notch inhibition are being investigated in preclinical and clinical studies in oncology. A large body of evidence now shows that the dysregulation of the Notch pathway is also involved in the pathophysiology of cardiovascular diseases (CVDs). Areas covered: This review discusses the molecular mechanisms involving Notch which underlie heart failure, aortic valve calcification, and aortic aneurysm. Expert opinion: Despite the existence of preventive, pharmacological and surgical interventions approaches, CVDs are the first causes of mortality worldwide. The Notch pathway is becoming increasingly recognized as being involved in heart failure, aortic aneurysm and aortic valve calcification, which are among the most common global causes of mortality due to CVDs. As already shown in cancer, the dissection of the biological processes and molecular mechanisms involving Notch should pave the way for new strategies to prevent and cure these diseases.

Development of calcific aortic valve disease: Do we know enough for new clinical trials?

Calcific aortic valve disease (CAVD), previously thought to represent a passive degeneration of the valvular extracellular matrix (VECM), is now regarded as an intricate multistage disorder with sequential yet intertangled and interacting underlying processes. Endothelial dysfunction and injury, initiated by disturbed blood flow and metabolic disorders, lead to the deposition of low-density lipoprotein cholesterol in the VECM further provoking macrophage infiltration, oxidative stress, and release of pro-inflammatory cytokines. Such changes in the valvular homeostasis induce differentiation of normally quiescent valvular interstitial cells (VICs) into synthetically active myofibroblasts producing excessive quantities of the VECM and proteins responsible for its remodeling. As a result of constantly ongoing degradation and re-deposition, VECM becomes disorganised and rigid, additionally potentiating myofibroblastic differentiation of VICs and worsening adaptation of the valve to the blood flow. Moreover, disrupted and excessively vascularised VECM is susceptible to the dystrophic calcification caused by calcium and phosphate precipitating on damaged collagen fibers and concurrently accompanied by osteogenic differentiation of VICs. Being combined, passive calcification and biomineralisation synergistically induce ossification of the aortic valve ultimately resulting in its mechanical incompetence requiring surgical replacement. Unfortunately, multiple attempts have failed to find an efficient conservative treatment of CAVD; however, therapeutic regimens and clinical settings have also been far from the optimal. In this review, we focused on interactions and transitions between aforementioned mechanisms demarcating ascending stages of CAVD, suggesting a predisposing condition (bicuspid aortic valve) and drug combination (lipid-lowering drugs combined with angiotensin II antagonists and cytokine inhibitors) for the further testing in both preclinical and clinical trials.

The intestinal microbiota associated with cardiac valve calcification differs from that of coronary artery disease

BACKGROUND AND AIMS

Although most risk factors for cardiac valve calcification (VC) are similar to those for coronary artery disease (CAD), they differ regarding lesions and clinical symptoms. Recently, increasing evidence suggests that intestinal bacteria play essential roles in cardiovascular disease (CVD). It is plausible that the gut microbiota is linked to the occurrence of different CVDs under similar risk factors. Thus, we aimed to explore the gut microbiomes in patients with VC or CAD and determine their underlying connections.

METHODS

We collected samples from 119 subjects and performed 16S rRNA gene sequencing to analyze the gut microbiomes in VC and CAD patients and in control volunteers.

RESULTS

The gut microbiomes of VC and CAD patients were significantly different in terms of beta-diversity. Bacteria from Veillonella dispar, Bacteroides plebeius and Fusobacterium were enriched in the VC group, while members of Collinsella aerofaciens, Megamonas, Enterococcus, Megasphaera, Dorea and Blautia were decreased. According to the association with dyslipidemia, seven operational taxonomic units (OTUs), including Parabacteroides distasonis, Megamonas, Fusobacterium, Bacteroides sp., Bacteroides plebeius, Lactobacillus and Prevotella copri, were regarded as potential pathogens for CVDs. Additionally, Prevotella copri might be a keystone of CVDs, especially in VC patients, while Collinsella aerofaciens is a possible keystone of CAD, based on the multi-correlations of these bacteria with other OTUs in microbial communities.

CONCLUSIONS

Patients with VC and CAD suffer from different gut microbial dysbiosis. The gut microbiomes are associated with the clinical characteristics in these diseases and might be potential therapeutic targets.

I-κB kinase-ε knockout protects against angiotensin II induced aortic valve thickening in apolipoprotein E deficient mice

Aortic stenosis (AS) is considered to be an actively regulated progress that involves similar pathophysiological processes as atherosclerosis. I-κB kinase-ε (IKKε) is a proinflammatory molecule involved in atherosclerosis. The objective of the present study was to define the role of IKKε in pathological valvular remodeling. Aortic valves (AVs) from 52 patients undergoing AV replacement (AS) and 13 patients undergoing heart transplant (Control) were analyzed. ApoE^-/- mice (AK, n = 20) and ApoE^-/-IKKε^-/- mice (DK, n = 20) were generated and infused with saline or Ang II for 4 weeks. We found an upregulation of IKKε in human stenotic aortic valves compared to that in control AVs. Our results demonstrated that AK mice receiving AngII exhibited more advanced valvular remodeling and markedly increased IKKε expression. Conversely, loss of IKKε reduced adverse aortic valve thickening in response to Ang II, as measured by histological analyses. Furthermore, according to immunofluorescence analysis, Ang II resulted in obvious increases in the expression of α-SMA, TGF-β and NF-κB pathway components in the AK group, especially in the thickened area, while these increases were blocked in the DK group. Moreover, IKKε was co-expressed with α-SMA in valvular interstitial cells in ApoE^-/- mice after an AngII infusion. These data provide evidence that IKKε plays a key role in the development of valvular remodeling and that it may be a novel target for the treatment of AS.

Relaxin induces up-regulation of ADAM10 metalloprotease in RXFP1-expressing cells by PI3K/AKT signaling

ADAM10 metalloprotease is required for activation of Notch-1, a transmembrane receptor regulating cell differentiation, proliferation and apoptosis, whose intracellular proteolytic fragment NICD mediates some key cardiovascular effects of the hormone relaxin (RLX). This study demonstrates the involvement of ADAM10 and PI3K/Akt signaling in mediating RLX-induced Notch-1 activation. H9c2 cardiomyocytes and NIH3T3 fibroblasts were incubated with human RLX-2 (17 nmol/l, 24 h) in presence or absence of the PI3K or Akt inhibitors wortmannin (WT, 100 nmol/l) and triciribine (TCN, 1 μmol/l). Cyclohexanedione-inactivated RLX (iRLX) served as negative control. RLX significantly increased Akt phosphorylation, ADAM10 and NICD expression, which were abolished by WT or TCN and did not occur with iRLX. These findings highlight a new receptor-specific signal transduction pathway of RLX.

Mir-29b promotes human aortic valve interstitial cell calcification via inhibiting TGF-β3 through activation of wnt3/β-catenin/Smad3 signaling

Herein, we hypothesized that pro-osteogenic MicroRNAs (miRs) could play functional roles in the calcification of the aortic valve and aimed to explore the functional role of miR-29b in the osteoblastic differentiation of human aortic valve interstitial cells (hAVICs) and the underlying molecular mechanism. Osteoblastic differentiation of hAVICs isolated from human calcific aortic valve leaflets obtained intraoperatively was induced with an osteogenic medium. Alizarin red S staining was used to evaluate calcium deposition. The protein levels of osteogenic markers and other proteins were evaluated using western blotting and/or immunofluorescence while qRT-PCR was applied for miR and mRNA determination. Bioinformatics and luciferase reporter assay were used to identify the possible interaction between miR-29b and TGF-β3. Calcium deposition and the number of calcification nodules were pointedly and progressively increased in hAVICs during osteogenic differentiation. The levels of osteogenic and calcification markers were equally increased, thus confirming the mineralization of hAVICs. The expression of miR-29b was significantly increased during osteoblastic differentiation. Furthermore, the osteoblastic differentiation of hAVICs was significantly inhibited by the miR-29b inhibition. TGF-β3 was markedly downregulated while Smad3, Runx2, wnt3, and β-catenin were significantly upregulated during osteogenic induction at both the mRNA and protein levels. These effects were systematically induced by miR-29b overexpression while the inhibition of miR-29b showed the inverse trends. Moreover, TGF-β3 was a direct target of miR-29b. Inhibition of miR-29b hinders valvular calcification through the upregulation of the TGF-β3 via inhibition of wnt/β-catenin and RUNX2/Smad3 signaling pathways.

Toll-Like Receptors, Inflammation, and Calcific Aortic Valve Disease

Inflammation, the primary response of innate immunity, is essential to initiate the calcification process underlying calcific aortic valve disease (CAVD), the most prevalent valvulopathy in Western countries. The pathogenesis of CAVD is multifactorial and includes inflammation, hemodynamic factors, fibrosis, and active calcification. In the development of CAVD, both innate and adaptive immune responses are activated, and accumulating evidences show the central role of inflammation in the initiation and propagation phases of the disease, being the function of Toll-like receptors (TLR) particularly relevant. These receptors act as sentinels of the innate immune system by recognizing pattern molecules from both pathogens and host-derived molecules released after tissue damage. TLR mediate inflammation via NF-κB routes within and beyond the immune system, and play a crucial role in the control of infection and the maintenance of tissue homeostasis. This review outlines the current notions about the association between TLR signaling and the ensuing development of inflammation and fibrocalcific remodeling in the pathogenesis of CAVD. Recent data provide new insights into the inflammatory and osteogenic responses underlying the disease and further support the hypothesis that inflammation plays a mechanistic role in the initiation and progression of CAVD. These findings make TLR signaling a potential target for therapeutic intervention in CAVD.

Beyond cardiomyocyte loss: Role of Notch in cardiac aging

The knowledge of the cellular events occurring in the aging heart has dramatically expanded in the last decade and is expected to further grow in years to come. It is now clear that impaired function and loss of cardiomyocytes are major features of cardiac aging, but other events are likewise important. In particular, accumulating experimental evidence highlights the importance of fibroblast and cardiac progenitor cell (CPC) dysfunction. The Notch pathway regulates cardiomyocyte, fibroblast, and CPC activity and, thus, may be critically involved in heart disease associated with advanced age, especially heart failure. In a translational perspective, thorough investigation of the Notch system in the aging myocardium may lead to the identification of molecular targets for novel therapies for age-related cardiac disease.

Parathyroid hormone promotes osteoblastic differentiation of endothelial cells via the extracellular signal-regulated protein kinase 1/2 and nuclear factor-κB signaling pathways

Vascular calcification (VC) occurs in patients with chronic kidney disease (CKD) and contributes to cardiovascular dysfunction and mortality. Parathyroid hormone (PTH) is a crucial regulator of VC. High PTH serum levels constitute as a major risk factor for patients with CKD. However, the effect and mechanism of PTH on osteoblastic differentiation in endothelial cells have not been fully elucidated. In the present study, the role of PTH in VC was investigated using an in vitro calcification model. Endothelial cells were stimulated with PTH in the femto- to picomolar range. As determined by western blot analysis and ELISA, osteoblastic differentiation, as indicated by the BMP2 marker, occurred with maximum effect at 1×10^-10 mmol/l PTH. The results indicate that PTH promotes osteoblastic differentiation of endothelial cells, as demonstrated by the increased expression of bone morphogenetic protein (BMP) 2 and BMP4. In addition, western blot analysis revealed that PTH activated the extracellular signal-regulated protein kinase (Erk)1/2 and nuclear factor (NF)-κB signaling pathways. However, reverse transcription-quantitative polymerase chain reaction demonstrated that inhibitors specific to Erk1/2 and NF-κB eradicated the effect of PTH treatment on BMP2, BMP4, ALP and RUNX2 expression. These results demonstrate that PTH promotes the osteoblastic differentiation of endothelial cells via the Erk1/2 and NF-κB signaling pathways, which suggests a potential role of PTH in the promotion of VC. These findings provide an insight into the association between PTH and cardiovascular disease.

Different Notch signaling in cells from calcified bicuspid and tricuspid aortic valves

AIMS

Calcific aortic valve disease is the most common heart valve disease in the Western world. Bicuspid and tricuspid aortic valve calcifications are traditionally considered together although the dynamics of the disease progression is different between the two groups of patients. Notch signaling is critical for bicuspid valve development and NOTCH1 mutations are associated with bicuspid valve and calcification. We hypothesized that Notch-dependent mechanisms of valve mineralization might be different in the two groups.

METHODS AND RESULTS

We used aortic valve interstitial cells and valve endothelial cells from patients with calcific aortic stenosis with bicuspid or tricuspid aortic valve. Expression of Notch-related genes in valve interstitial cells by qPCR was different between bicuspid and tricuspid groups. Discriminant analysis of gene expression pattern in the interstitial cells revealed that the cells from calcified bicuspid valves formed a separate group from calcified tricuspid and control cells. Interstitial cells from bicuspid calcified valves demonstrated significantly higher sensitivity to stimuli at early stages of induced proosteogenic differentiation and were significantly more sensitive to the activation of proosteogenic OPN, ALP and POSTIN expression by Notch activation. Notch-activated endothelial-to-mesenchymal transition and the corresponding expression of HEY1 and SLUG were also more prominent in bicuspid valve derived endothelial cells compared to the cells from calcified tricuspid and healthy valves.

CONCLUSION

Early signaling events including Notch-dependent mechanisms that are responsible for the initiation of aortic valve calcification are different between the patients with bicuspid and tricuspid aortic valves.

Mechanisms of Smooth Muscle Cell Differentiation Are Distinctly Altered in Thoracic Aortic Aneurysms Associated with Bicuspid or Tricuspid Aortic Valves

Cellular and molecular mechanisms of thoracic aortic aneurysm are not clear and therapeutic approaches are mostly absent. Thoracic aortic aneurysm is associated with defective differentiation of smooth muscle cells (SMC) of aortic wall. Bicuspid aortic valve (BAV) comparing to tricuspid aortic valve (TAV) significantly predisposes to a risk of thoracic aortic aneurysms. It has been suggested recently that BAV-associated aortopathies represent a separate pathology comparing to TAV-associated dilations. The only proven candidate gene that has been associated with BAV remains NOTCH1. In this study we tested the hypothesis that Notch-dependent and related TGF-β and BMP differentiation pathways are differently altered in aortic SMC of BAV- vs. TAV-associated aortic aneurysms. SMC were isolated from aortic tissues of the patients with BAV- or TAV-associated aortic aneurysms and from healthy donors used as controls. Gene expression was verified by qPCR and Western blotting. For TGF-β induced differentiation SMC were treated with the medium containing TGF-β1. To induce proosteogenic signaling we cultured SMC in the presence of specific osteogenic factors. Notch-dependent differentiation was induced via lentiviral transduction of SMC with activated Notch1 domain. MYOCD expression, a master gene of SMC differentiation, was down regulated in SMC of both BAV and TAV patients. Discriminant analysis of gene expression patterns included a set of contractile genes specific for SMC, Notch-related genes and proosteogenic genes and revealed that control cells form a separate cluster from both BAV and TAV group, while BAV- and TAV-derived SMC are partially distinct with some overlapping. In differentiation experiments TGF-β caused similar patterns of target gene expression for BAV- and TAV derived cells while the induction was higher in the diseased cells than in control ones. Osteogenic induction caused significant change in RUNX2 expression exclusively in BAV group. Notch activation induced significant ACTA2 expression also exclusively in BAV group. We show that Notch acts synergistically with proosteogenic factors to induce ACTA2 transcription and osteogenic differentiation. In conclusion we have found differences in responsiveness of SMC to Notch and to proosteogenic induction between BAV- and TAV-associated aortic aneurysms.

Sex-dependent aortic valve pathology in patients with rheumatic heart disease

Background

Rheumatic heart disease is an autoimmune disease caused by group A streptococci infection and frequently affects the aortic valve. Sex differences are common in the disease progression, treatment, and outcome. However, little is known about the sex differences in the pathology of aortic valves in rheumatic heart disease.

Design

We studied the end-stage calcific aortic valves from male versus female patients to reveal the sex-dependent pathology differences and molecular changes associated with requiring valve replacement.

Methods

Aortic valves from 39 patients with rheumatic heart disease (19 males and 20 females) were collected at the time of aortic valve replacement for comparative pathology, immunohistochemistry, and gene expression analyses. Clinical characteristics were also analyzed and compared between the two groups.

Results

Aortic valves from female patients exhibited increased expression of collagens, infiltration of monocytes/macrophages and neovascularization. Aortic valves from female patients also had increased expression of inflammatory genes involved in the NFKB pathway (phosphorylated NFKB p65 subunit, IL8, and NOS3) and Th1 cytokine genes (IFNA and IL12B). The severe valve pathology in female patients was correlated with a higher serum level of anti-streptolysin O antibodies.

Conclusion

Inflammation is more prominent in aortic valves of female patients with rheumatic heart disease. This sex difference may contribute to the severe valve pathology and worse outcome of female patients.

Toll-like receptor-4 signaling pathway in aorta aging and diseases: "its double nature"

Recent advances in the field of innate immunity have revealed a complex role of innate immune signaling pathways in both tissue homeostasis and disease. Among them, the Toll-like receptor 4 (TLR-4) pathways has been linked to various pathophysiological conditions, such as cardiovascular diseases (CVDs). This has been interrogated by developing multiple laboratory tools that have shown in animal models and clinical conditions, the involvement of the TLR-4 signaling pathway in the pathophysiology of different CVDs, such as atherosclerosis, ischemic heart disease, heart failure, ischemia-reperfusion injury and aorta aneurysm. Among these, aorta aneurysm, a very complex pathological condition with uncertain etiology and fatal complications (i.e. dissection and rupture), has been associated with the occurrence of high risk cardiovascular conditions, including thrombosis and embolism. In this review, we discuss the possible role of TLR-4 signaling pathway in the development of aorta aneurysm, considering the emerging evidence from ongoing investigations. Our message is that emphasizing the role of TLR-4 signaling pathway in aorta aneurysm may serve as a starting point for future studies, leading to a better understanding of the pathophysiological basis and perhaps the effective treatment of this difficult human disease.

Endothelial to mesenchymal transformation is induced by altered extracellular matrix in aortic valve endothelial cells

Alterations in shear stress, mechanical deformation, extracellular matrix (ECM) composition and exposure to inflammatory conditions are known to cause endothelial to mesenchymal transformation (EndMT). This change in endothelial phenotype has only recently been linked to adult pathologies such as cancer progression, organ fibrosis, and calcific aortic valve disease; and its function in adult physiology, especially in response to tissue mechanics, has not been rigorously investigated. EndMT is a response to mechanical and biochemical signals that results in the remodeling of underlying tissues. In diseased aortic valves, glycosaminoglycans (GAGs) are present in the collagen-rich valve fibrosa, and are deposited near calcified nodules. In this study, in vitro models of early and late-stage valve disease were developed by incorporating the GAGs chondroitin sulfate (CS), hyaluronic acid, and dermatan sulfate into 3D collagen hydrogels with or without exposure to TGF-β1 to simulate EndMT in response to microenvironmental changes. High levels of CS induced the highest rate of EndMT and led to the most collagen I and GAG production by mesenchymally transformed cells, which indicates a cell phenotype most likely to promote fibrotic disease. Mesenchymal transformation due to altered ECM was found to depend on cell-ECM bond strength and extracellular signal-regulated protein kinases 1/2 signaling. Determining the environmental conditions that induce and promote EndMT, and the subsequent behavior of mesenchymally transformed cells, will advance understanding on the role of endothelial cells in tissue regeneration or disease progression. © 2017 Wiley Periodicals Inc. J Biomed Mater Res Part A: 105A: 2729-2741, 2017.

ADAMTS5 Deficiency in Calcified Aortic Valves Is Associated With Elevated Pro-Osteogenic Activity in Valvular Interstitial Cells

OBJECTIVE

Extracellular matrix proteinases are implicated in the pathogenesis of calcific aortic valve disease. The ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5) enzyme is secreted, matrix-associated metalloendopeptidase, capable of degrading extracellular matrix proteins, particularly matrilin 2. We sought to determine the role of the ADAMTS5/matrilin 2 axis in mediating the phenotype transition of valvular interstitial cells (VICs) associated with calcific aortic valve disease.

APPROACH AND RESULTS

Levels of ADAMTS5, matrilin 2, and α-SMA (α-smooth muscle actin) were evaluated in calcified and normal human aortic valve tissues and VICs. Calcified aortic valves have reduced levels of ADAMTS5 and higher levels of matrilin 2 and α-SMA. Treatment of normal VICs with soluble matrilin 2 caused an increase in α-SMA level through Toll-like receptors 2 and 4, which was accompanied by upregulation of runt-related transcription factor 2 and alkaline phosphatase. In addition, ADAMTS5 knockdown in normal VICs enhanced the effect of matrilin 2. Matrilin 2 activated nuclear factor (NF) κB and NF of activated T cells complex 1 and induced the interaction of these 2 NFs. Inhibition of either NF-κB or NF of activated T cells complex 1 suppressed matrilin 2's effect on VIC phenotype change. Knockdown of α-SMA reduced and overexpression of α-SMA enhanced the expression of pro-osteogenic factors and calcium deposit formation in human VICs.

CONCLUSIONS

Matrilin 2 induces myofibroblastic transition and elevates pro-osteogenic activity in human VICs via activation of NF-κB and NF of activated T cells complex 1. Myofibroblastic transition in human VICs is an important mechanism of elevating the pro-osteogenic activity. Matrilin 2 accumulation associated with relative ADAMTS5 deficiency may contribute to the mechanism underlying calcific aortic valve disease progression.

Altered MicroRNA Expression Is Responsible for the Pro-Osteogenic Phenotype of Interstitial Cells in Calcified Human Aortic Valves

BACKGROUND

The transition of aortic valve interstitial cells (AVICs) to myofibroblastic and osteoblast-like phenotypes plays a critical role in calcific aortic valve disease progression. Several microRNAs (miRs) are implicated in stem cell differentiation into osteoblast. We hypothesized that an epigenetic mechanism regulates valvular pro-osteogenic activity. This study examined miR profile in AVICs of calcified valves and identified miRs responsible for AVIC phenotypic transition.

METHODS AND RESULTS

AVICs were isolated from normal and diseased valves. The miR microarray analysis revealed 14 upregulated and 12 downregulated miRs in diseased AVICs. Increased miR-486 and decreased miR-204 levels were associated with higher levels of myofibroblastic biomarker α-smooth muscle actin and osteoblastic biomarkers runt-related transcription factor 2 (Runx2) and osterix (Osx). Cotransfection of miR-486 antagomir and miR-204 mimic in diseased AVICs reduced their ability to express Runx2 and Osx. The miR-486 mimic upregulated α-smooth muscle actin expression in normal AVICs through the protein kinase B pathway and moderately elevated Runx2 and Osx levels. Knockdown of α-smooth muscle actin attenuated Runx2 and Osx expression induced by miR-486. The miR-486 mimic and miR-204 antagomir synergistically promoted Runx2 and Osx expression and calcium deposition in normal AVICs and normal aortic valve tissue.

CONCLUSIONS

In AVICs of calcified valves, increased levels of miR-486 induce myofibroblastic transition to upregulate Runx2 and Osx expression and synergize with miR-204 deficiency to elevate cellular and valvular pro-osteogenic activity. These novel findings indicate that modulation of the epigenetic mechanism underlying valvular pro-osteogenic activity has therapeutic potential for prevention of calcific aortic valve disease progression.

IL-37 suppresses MyD88-mediated inflammatory responses in human aortic valve interstitial cells

BACKGROUND

Calcific aortic valve disease (CAVD) is common among the elderly, and aortic valve interstitial cells (AVICs) exhibit unique inflammatory and osteogenic responses to pro-inflammatory stimulation which play an important role in valvular fibrosis and calcification. Thus, suppression of AVIC pro-inflammatory response may have therapeutic utility for prevention of CAVD progression. Interleukin (IL)-37, an anti-inflammatory cytokine, reduces tissue inflammation.

OBJECTIVE

This study was to test the hypothesis that IL-37 suppresses human AVIC inflammatory responses to Toll-like receptor (TLR) agonists.

METHODS AND RESULTS

Human AVICs were exposed to Pam3CSK4, poly(I:C) and lipopolysaccharide, respectively, in the presence and absence of recombinant human IL-37. Stimulation of TLR4 increased the production of intercellular adhesion molecule-1, IL-6, IL-8 and monocyte chemoattractant protein-1. Knockdown of myeloid differentiation factor 88 (MyD88) or TIR-domain-containing adaptor inducing interferon-β (TRIF) differentially affected inflammatory mediator production following TLR4 stimulation. IL-37 reduced the production of these inflammatory mediators induced by TLR4. Moreover, knockdown of IL-37 enhanced the induction of these mediators by TLR4. IL-37 also suppressed inflammatory mediator production induced by the MyD88-dependent TLR2, but had no effect on the inflammatory responses to the TRIF-dependent TLR3. Furthermore, IL-37 inhibited NF-κB activation induced by TLR2 or TLR4 through a mechanism dependent of IL-18 receptor α-chain.

CONCLUSION

Activation of TLR2, TLR3 or TLR4 up-regulates the production of inflammatory mediators in human AVICs. IL-37 suppresses MyD88-mediated responses to reduce inflammatory mediator production following stimulation of TLR2 and TLR4. This anti-inflammatory cytokine may be useful for suppression of aortic valve inflammation elicited by MyD88-dependent TLR signaling.

Klotho suppresses high phosphate-induced osteogenic responses in human aortic valve interstitial cells through inhibition of Sox9

Elevated level of blood phosphate (Pi) associated with chronic kidney disease (CKD) is a risk factor of aortic valve calcification. Aortic valve interstitial cells (AVICs) display osteogenic responses to high Pi although the underlying mechanism is incompletely understood. Sox9 is a pro-chondrogenic factor and may play a role in ectopic tissue calcification. Circulating and kidney levels of Klotho are reduced in patients with CKD. We hypothesized that Sox9 mediates high Pi-induced osteogenic responses in human AVICs and that Klotho inhibits the responses. Treatment of human AVICs with high Pi increased protein levels of Runt-related transcription factor 2 (Runx2) and alkaline phosphatase (ALP), and a prolonged exposure to high Pi caused calcium deposition. High Pi induced Sox9 upregulation through PKD and Akt activation. Knockdown of Sox9 essentially abolished the effect of high Pi on the osteogenic responses. Lower Klotho levels were observed in calcified aortic valve tissues. Interestingly, high Pi decreased Klotho levels in AVICs from normal valves, and treatment with recombinant Klotho markedly reduced the effect of high Pi on the levels of Sox9, Runx2, and ALP and suppressed calcium deposition. We conclude that high Pi induces human AVIC osteogenic responses through Sox9. Human AVICs express Klotho, and its levels in AVICs are modulated by high Pi and valvular calcification. Importantly, Klotho suppresses the pro-osteogenic effect of high Pi on human AVICs. These novel findings indicate that modulation of Klotho may have therapeutic potential for mitigation of valvular calcification associated with CKD.

KEY MESSAGES

CAVD associated with chronic kidney disease is a significant clinical problem. High phosphate upregulates Sox9 through AKT and PKD in human AVICs. Calcified human aortic valves have lower levels of Klotho. Klotho suppresses Sox9 upregulation and intranuclear translocation. Klotho inhibits high phosphate-induced osteogenic activity in human AVICs.

High mobility group box 1 induces calcification of aortic valve interstitial cells via toll-like receptor 4

Chronic inflammation and the calcification of aortic valve interstitial cells (AVICs) are the primary etiologies of calcific aortic valve disease (CAVD). However, the underlying mechanism remains to be elucidated. The present study investigated the importance of high mobility group box 1 (HMGB1) via toll-like receptor 4 (TLR4) for the regulation of inflammation and calcification in AVICs. It was determined that the expression levels of HMGB1 and TLR4 were increased in the calcific region of aortic valves with CAVD. In cultured primary AVICs from wild-type mice, HMGB1 treatment demonstrated a dose-dependent increase in mineralization levels and osteogenic gene expression. These effects were significantly reduced in AVICs obtained from TLR4 knockout mice (TLR4^−/−). In addition, calcification was inhibited by TLR4-specific antibodies in primary AVICs. HMGB1 induced the activation of p38 and nuclear factor-κB (NF-κB) in TLR4^−/− primary AVICs, and inhibited p38 and NF-κB in wild-type AVICs treated with TLR4-specific antibodies. The present study demonstrated that TLR4 may function as an essential mediator of HMGB1-induced calcification and in the activation of p38 and NF-κB.