Ligation of ICAM-1 on human aortic valve interstitial cells induces the osteogenic response: A critical role of the Notch1-NF-κB pathway in BMP-2 expression

Indoxyl-sulfate activation of the AhR- NF-κB pathway promotes interleukin-6 secretion and the subsequent osteogenic differentiation of human valvular interstitial cells from the aortic valve

BACKGROUND

Calcific aortic stenosis (CAS) is more prevalent, occurs earlier, progresses faster and has worse outcomes in patients with chronic kidney disease (CKD). The uremic toxin indoxyl sulfate (IS) is powerful predictor of cardiovascular mortality in these patients and a strong promoter of ectopic calcification whose role in CAS remains poorly studied. The objective of this study was to evaluate whether IS influences the mineralization of primary human valvular interstitial cells (hVICs) from the aortic valve.

METHODS

Primary hVICs were exposed to increasing concentrations of IS in osteogenic medium (OM). The hVICs' osteogenic transition was monitored by qRT-PCRs for BMP2 and RUNX2 mRNA. Cell mineralization was assayed using the o-cresolphthalein complexone method. Inflammation was assessed by monitoring NF-κB activation using Western blots as well as IL-1β, IL-6 and TNF-α secretion by ELISAs. Small interfering RNA (siRNA) approaches enabled us to determine which signaling pathways were involved.

RESULTS

Indoxyl-sulfate increased OM-induced hVICs osteogenic transition and calcification in a concentration-dependent manner. This effect was blocked by silencing the receptor for IS (the aryl hydrocarbon receptor, AhR). Exposure to IS promoted p65 phosphorylation, the blockade of which inhibited IS-induced mineralization. Exposure to IS promoted IL-6 secretion by hVICs, a phenomenon blocked by silencing AhR or p65. Incubation with an anti-IL-6 antibody neutralized IS's pro-calcific effects.

CONCLUSION

IS promotes hVIC mineralization through AhR-dependent activation of the NF-κB pathway and the subsequent release of IL-6. Further research should seek to determine whether targeting inflammatory pathways can reduce the onset and progression of CKD-related CAS.

Sex-Related Signaling of Aldosterone/Mineralocorticoid Receptor Pathway in Calcific Aortic Stenosis

BACKGROUND

There are sex differences in the pathophysiology of aortic valve (AV) calcification in patients with aortic stenosis, although the molecular and cellular mechanisms have not been elucidated. Aldosterone (Aldo) promotes proteoglycan synthesis in valve interstitial cells (VICs) from mitral valves via the mineralocorticoid receptor (MR). We investigated the influence of sex in the role of Aldo/MR pathway in AV alterations in patients with aortic stenosis.

METHODS AND RESULTS

MR was expressed by primary aortic VICs and in AVs from patients with aortic stenosis. MR expression positively correlated with VIC activation markers in AVs from both sexes. However, MR expression was positively associated with molecules involved in AV calcification only in AV from men. Aldo enhanced VIC activation markers in cells from men and women. Interestingly, Aldo increased the expression of calcification markers only in VICs isolated from men. In female VICs, Aldo enhanced fibrotic molecules. MR antagonism (spironolactone) blocked all the above effects. Cytokine arrays showed ICAM (intercellular adhesion molecule)-1 and osteopontin to be specifically increased by Aldo in male VICs. In AVs from men, MR expression positively associated with both ICAM-1 (intercellular adhesion molecule-1) and osteopontin. Only in female VICs, estradiol treatment blocked Aldo-induced VICs activation, inflammation, and fibrosis.

CONCLUSIONS

These findings demonstrate that the Aldo/MR pathway could play a role in early stages of aortic stenosis by promoting VICs activation, fibrosis, and ulterior calcification. Importantly, Aldo/MR pathway is involved in fibrosis in women and in early AV calcification only in men. Accordingly, MR antagonism emerges as a new sex-specific pharmacological treatment to prevent AV alterations.

Identification of Immune-Associated Genes in Diagnosing Aortic Valve Calcification With Metabolic Syndrome by Integrated Bioinformatics Analysis and Machine Learning

Background

Immune system dysregulation plays a critical role in aortic valve calcification (AVC) and metabolic syndrome (MS) pathogenesis. The study aimed to identify pivotal diagnostic candidate genes for AVC patients with MS.

Methods

We obtained three AVC and one MS dataset from the gene expression omnibus (GEO) database. Identification of differentially expressed genes (DEGs) and module gene via Limma and weighted gene co-expression network analysis (WGCNA), functional enrichment analysis, protein–protein interaction (PPI) network construction, and machine learning algorithms (least absolute shrinkage and selection operator (LASSO) regression and random forest) were used to identify candidate immune-associated hub genes for diagnosing AVC with MS. To assess the diagnostic value, the nomogram and receiver operating characteristic (ROC) curve were developed. Finally, immune cell infiltration was created to investigate immune cell dysregulation in AVC.

Results

The merged AVC dataset included 587 DEGs, and 1,438 module genes were screened out in MS. MS DEGs were primarily enriched in immune regulation. The intersection of DEGs for AVC and module genes for MS was 50, which were mainly enriched in the immune system as well. Following the development of the PPI network, 26 node genes were filtered, and five candidate hub genes were chosen for nomogram building and diagnostic value evaluation after machine learning. The nomogram and all five candidate hub genes had high diagnostic values (area under the curve from 0.732 to 0.982). Various dysregulated immune cells were observed as well.

Conclusion

Five immune-associated candidate hub genes (BEX2, SPRY2, CXCL16, ITGAL, and MORF4L2) were identified, and the nomogram was constructed for AVC with MS diagnosis. Our study could provide potential peripheral blood diagnostic candidate genes for AVC in MS patients.

Updated Pathways in Cardiorenal Continuum after Kidney Transplantation

Cardiovascular disease (CVD) remains one of the leading causes for increased morbidity and mortality in chronic kidney disease (CKD). Kidney transplantation is the preferred treatment option for CKD G5. Improved perioperative and postoperative care, personalized immunosuppressive regimes, and refined matching procedures of kidney transplants improves cardiovascular health in the early posttransplant period. However, the long-term burden of CVD is considerable. Previously underrecognized, the role of the complement system alongside innate immunity, inflammaging, structural changes in the glomerular filtration barrier and early vascular ageing also seem to play an important role in the posttransplant management. This review provides up-to-date knowledge on these pathways that may influence the cardiovascular and renal continuum and identifies potential targets for future therapies. Arterial destiffening strategies and the applicability of sodium-glucose cotransporter 2 inhibitors and their role in cardiovascular health after kidney transplantation are also addressed.

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.

A NOTCH1/LSD1/BMP2 co-regulatory network mediated by miR-137 negatively regulates osteogenesis of human adipose-derived stem cells

Background

MicroRNAs have been recognized as critical regulators for the osteoblastic lineage differentiation of human adipose-derived stem cells (hASCs). Previously, we have displayed that silencing of miR-137 enhances the osteoblastic differentiation potential of hASCs partly through the coordination of lysine-specific histone demethylase 1 (LSD1), bone morphogenetic protein 2 (BMP2), and mothers against decapentaplegic homolog 4 (SMAD4). However, still numerous molecules involved in the osteogenic regulation of miR-137 remain unknown. This study aimed to further elucidate the epigenetic mechanisms of miR-137 on the osteogenic differentiation of hASCs.

Methods

Dual-luciferase reporter assay was performed to validate the binding to the 3′ untranslated region (3′ UTR) of NOTCH1 by miR-137. To further identify the role of NOTCH1 in miR-137-modulated osteogenesis, tangeretin (an inhibitor of NOTCH1) was applied to treat hASCs which were transfected with miR-137 knockdown lentiviruses, then together with negative control (NC), miR-137 overexpression and miR-137 knockdown groups, the osteogenic capacity and possible downstream signals were examined. Interrelationships between signaling pathways of NOTCH1-hairy and enhancer of split 1 (HES1), LSD1 and BMP2-SMADs were thoroughly investigated with separate knockdown of NOTCH1, LSD1, BMP2, and HES1.

Results

We confirmed that miR-137 directly targeted the 3′ UTR of NOTCH1 while positively regulated HES1. Tangeretin reversed the effects of miR-137 knockdown on osteogenic promotion and downstream genes expression. After knocking down NOTCH1 or BMP2 individually, we found that these two signals formed a positive feedback loop as well as activated LSD1 and HES1. In addition, LSD1 knockdown induced NOTCH1 expression while suppressed HES1.

Conclusions

Collectively, we proposed a NOTCH1/LSD1/BMP2 co-regulatory signaling network to elucidate the modulation of miR-137 on the osteoblastic differentiation of hASCs, thus providing mechanism-based rationale for miRNA-targeted therapy of bone defect.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02495-3.

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.

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.

Inflammation and Mechanical Stress Stimulate Osteogenic Differentiation of Human Aortic Valve Interstitial Cells

Background: Aortic valve calcification is an active proliferative process, where interstitial cells of the valve transform into either myofibroblasts or osteoblast-like cells causing valve deformation, thickening of cusps and finally stenosis. This process may be triggered by several factors including inflammation, mechanical stress or interaction of cells with certain components of extracellular matrix. The matrix is different on the two sides of the valve leaflets. We hypothesize that inflammation and mechanical stress stimulate osteogenic differentiation of human aortic valve interstitial cells (VICs) and this may depend on the side of the leaflet. Methods: Interstitial cells isolated from healthy and calcified human aortic valves were cultured on collagen or elastin coated plates with flexible bottoms, simulating the matrix on the aortic and ventricular side of the valve leaflets, respectively. The cells were subjected to 10% stretch at 1 Hz (FlexCell bioreactor) or treated with 0.1 μg/ml lipopolysaccharide, or both during 24 h. Gene expression of myofibroblast- and osteoblast-specific genes was analyzed by qPCR. VICs cultured in presence of osteogenic medium together with lipopolysaccharide, 10% stretch or both for 14 days were stained for calcification using Alizarin Red. Results: Treatment with lipopolysaccharide increased expression of osteogenic gene bone morphogenetic protein 2 (BMP2) (5-fold increase from control; p = 0.02) and decreased expression of mRNA of myofibroblastic markers: α-smooth muscle actin (ACTA2) (50% reduction from control; p = 0.0006) and calponin (CNN1) (80% reduction from control; p = 0.0001) when cells from calcified valves were cultured on collagen, but not on elastin. Mechanical stretch of VICs cultured on collagen augmented the effect of lipopolysaccharide. Expression of periostin (POSTN) was inhibited in cells from calcified donors after treatment with lipopolysaccharide on collagen (70% reduction from control, p = 0.001), but not on elastin. Lipopolysaccharide and stretch both enhanced the pro-calcific effect of osteogenic medium, further increasing the effect when combined for cells cultured on collagen, but not on elastin. Conclusion: Inflammation and mechanical stress trigger expression of osteogenic genes in VICs in a side-specific manner, while inhibiting the myofibroblastic pathway. Stretch and lipopolysaccharide synergistically increase calcification.

Simvastatin reduces the TLR4-induced inflammatory response in human aortic valve interstitial cells

BACKGROUND

Calcific aortic stenosis is a chronic inflammatory disease. Proinflammatory stimulation via toll-like receptor 4 (TLR4) causes the aortic valve interstitial cell (AVIC) to undergo phenotypic change. The AVIC first assumes an inflammatory phenotype characterized by the production of inflammatory mediators such as intercellular adhesion molecule-1 (ICAM-1), interleukin-8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1). This change has been linked with an osteogenic phenotypic response. Statins have recently been shown to have anti-inflammatory properties. We therefore hypothesized that statins may have an anti-inflammatory effect on human AVICs by downregulation of TLR4-stimulated inflammatory responses. Our purposes were (1) to determine the effect of simvastatin on TLR4-induced expression of inflammatory mediators in human AVICs and (2) to determine the mechanism(s) through which simvastatin exert this effect.

MATERIALS AND METHODS

Human AVICs were isolated from the explanted hearts of four patients undergoing cardiac transplantation. Cells were treated with simvastatin (50 μM) for 1 h before stimulation with TLR4 agonist lipopolysaccharide (LPS, 0.2 μg/mL). Immunoblotting (IB) was used to analyze cell lysates for ICAM-1 expression, and enzyme-linked immunosorbent assay was used to detect IL-8 and MCP-1 in cell culture media. Likewise, lysates were analyzed for TLR4 and nuclear factor-kappa B activation (IB). After simvastatin treatment, lysates were analyzed for TLR4 levels (IB). Statistics were by analysis of variance (P < 0.05).

RESULTS

Simvastatin reduced TLR4-induced ICAM-1, IL-8, and MCP-1 expression in AVICs. Simvastatin down-regulated TLR4 levels and suppressed TLR4-induced phosphorylation of nuclear factor-kappa B.

CONCLUSIONS

These data demonstrate the potential of a medical therapy (simvastatin) to impact the pathogenesis of aortic stenosis.

Roles of platelet-derived growth factor in vascular calcification

Vascular calcification (VC) is prevalent in aging, and patients with hypertension, chronic kidney disease (CKD), or diabetes. VC is regarded as an active and complex process that involves multiple mechanisms responsible for calcium deposition in vessel wall. In light of the complicated pathogenesis of VC, effective therapy for ameliorating VC is limited. Thus, it is urgent to explore the potential mechanisms and find new targets for the therapy of VC. Platelet-derived growth factor (PDGF), a potent mitogen, and chemoattractant have been found to disturb the vascular homeostasis by inducing inflammation, oxidative stress, and phenotype transition, all of which accelerate the process of VC. The aim of current review is to present a review about the roles of PDGF in affecting VC and to establish a potential target for treating VC.

Roles of aldosterone in vascular calcification: An update

Both clinical and experimental studies have demonstrated that vascular calcification (VC) is a common pathology shared in many chronic diseases such as chronic kidney disease (CKD) and diabetes. It's an independent risk factor for cardiovascular events. Since the pathogenesis of VC is complicated, current therapies have limited effects on the regression of VC. Therefore, it is urgent to investigate the potential mechanisms and find new targets for the treatment of VC. Aldosterone (Aldo), a mineralocorticoid hormone, is the metabolite of renin-angiotensin-aldosterone system (RAAS) activation, which can exert genomic and non-genomic effects on the cardiovascular system. Recent data suggests that Aldo can promote VC. Here, we summarized the roles of Aldo in the process of VC and a series of findings indicated that Aldo could act as a potentially therapeutic target for treating VC.

Cells and extracellular matrix interplay in cardiac valve disease: because age matters

Cardiovascular aging is a physiological process affecting all components of the heart. Despite the interest and experimental effort lavished on aging of cardiac cells, increasing evidence is pointing at the pivotal role of extracellular matrix (ECM) in cardiac aging. Structural and molecular changes in ECM composition during aging are at the root of significant functional modifications at the level of cardiac valve apparatus. Indeed, calcification or myxomatous degeneration of cardiac valves and their functional impairment can all be explained in light of age-related ECM alterations and the reciprocal interplay between altered ECM and cellular elements populating the leaflet, namely valvular interstitial cells and valvular endothelial cells, is additionally affecting valve function with striking reflexes on the clinical scenario. The initial experimental findings on this argument are underlining the need for a more comprehensive understanding on the biological mechanisms underlying ECM aging and remodeling as potentially constituting a pharmacological therapeutic target or a basis to improve existing prosthetic devices and treatment options. Given the lack of systematic knowledge on this topic, this review will focus on the ECM changes that occur during aging and on their clinical translational relevance and implications in the bedside scenario.