Valvular Interstitial Cells Research Articles

Glycosaminoglycans affect endothelial to mesenchymal transformation, proliferation, and calcification in a 3D model of aortic valve disease.

Calcific nodules form in the fibrosa layer of the aortic valve in calcific aortic valve disease (CAVD). Glycosaminoglycans (GAGs), which are normally found in the valve spongiosa, are located local to calcific nodules. Previous work suggests that GAGs induce endothelial to mesenchymal transformation (EndMT), a phenomenon described by endothelial cells’ loss of the endothelial markers, gaining of migratory properties, and expression of mesenchymal markers such as alpha smooth muscle actin (α-SMA). EndMT is known to play roles in valvulogenesis and may provide a source of activated fibroblast with a potential role in CAVD progression. In this study, a 3D collagen hydrogel co-culture model of the aortic valve fibrosa was created to study the role of EndMT-derived activated valvular interstitial cell behavior in CAVD progression. Porcine aortic valve interstitial cells (PAVIC) and porcine aortic valve endothelial cells (PAVEC) were cultured within collagen I hydrogels containing the GAGs chondroitin sulfate (CS) or hyaluronic acid (HA). The model was used to study alkaline phosphatase (ALP) enzyme activity, cellular proliferation and matrix invasion, protein expression, and calcific nodule formation of the resident cell populations. CS and HA were found to alter ALP activity and increase cell proliferation. CS increased the formation of calcified nodules without the addition of osteogenic culture medium. This model has applications in the improvement of bioprosthetic valves by making replacements more micro-compositionally dynamic, as well as providing a platform for testing new pharmaceutical treatments of CAVD.

Single-cell transcriptomics reveal cellular diversity of aortic valve and the immunomodulation by PPARγ during hyperlipidemia

Valvular inflammation triggered by hyperlipidemia has been considered as an important initial process of aortic valve disease; however, cellular and molecular evidence remains unclear. Here, we assess the relationship between plasma lipids and valvular inflammation, and identify association of low-density lipoprotein with increased valvular lipid and macrophage accumulation. Single-cell RNA sequencing analysis reveals the cellular heterogeneity of leukocytes, valvular interstitial cells, and valvular endothelial cells, and their phenotypic changes during hyperlipidemia leading to recruitment of monocyte-derived MHC-IIhi macrophages. Interestingly, we find activated PPARγ pathway in Cd36+ valvular endothelial cells increased in hyperlipidemic mice, and the conservation of PPARγ activation in non-calcified human aortic valves. While the PPARγ inhibition promotes inflammation, PPARγ activation using pioglitazone reduces valvular inflammation in hyperlipidemic mice. These results show that low-density lipoprotein is the main lipoprotein accumulated in the aortic valve during hyperlipidemia, leading to early-stage aortic valve disease, and PPARγ activation protects the aortic valve against inflammation.

Cellular-scale sex differences in extracellular matrix remodeling by valvular interstitial cells.

Males acquire calcific aortic valve disease (CAVD) twice as often as females, yet stenotic valves from females display significantly higher levels of fibrosis compared to males with similar extent of disease. Fibrosis occurs as an imbalance between theproduction and degradation of the extracellular matrix (ECM), specifically type I collagen. This work characterizes ECM production and remodeling by male and female valvular interstitial cells (VICs) to better understand the fibrocalcific divergence between sexes evident in CAVD. Male and female VICs were assessed for gene and protein expression of myofibroblastic markers, ECM components, matrix metalloproteinases (MMPs), and tissue inhibitors of MMPs (TIMPs) via qRT-PCR and western blot. Overall metabolic activity was also measured. Activity assays for collagenase and gelatinase were performed to examine degradation behavior. Male VICs produced greater levels of myofibroblastic markers while female VICs showed greater metabolic activity and collagen production. In general, females displayed a greater level of MMP expression and production than males, but no sex differences were observed in TIMP production. Male VICs also displayed a greater level of collagenase and gelatinase activity than female VICs. This work displays sex differences in ECM remodeling by VICs that could be related to the sexual dimorphism in ECM structure seen in clinical CAVD.

Dexamethasone and olmesartan as potential antiremodelling agents of valvular interstitial cell into myofibroblast

Rheumatic heart disease is a late complication of valvular inflammation caused by rheumatic fever. Studies have shown that the differentiation of valvular interstitial cells (VIC) into fibroblasts plays an important role in valvular remodeling and fibrosis. Various strategies to minimize valvular fibrosis has increased recently. This study aims to analyze the effect of dexamethasone, olmesartan, and its combination in inhibiting TGF-β1-induced VIC differentiation into myofibroblast. In vitro laboratory experimental-posttest only control group design was conducted. Isolated VIC of Oryctolagus cuniculus was pretreated using 2,5 ng/mL of TGF-β1 and divided into groups of dexamethasone (0.1 uM/L), olmesartan (100 nmol/L), and its combination. Inhibition of myofibroblast differentiation was quantified by the expression of α-SMA levels detected by immunofluorescence. Dexamethasone, olmesartan, and its combination administration were significantly reduced TGF-β1-induced VIC differentiation into myofibroblast expressed by α-SMA levels (dexamethasone 6823 ± 1735.3, olmesartan 6683.7 ± 2795.05). Combination of dexamethasone and olmesartan exhibit the most potent inhibition compared to control (5051.87 ± 1612.210 vs 22286.73 ± 2780.2; p < 0.000). In conclusion, dexamethasone, olmesartan, and the combination can significantly reduce the differentiation of VIC into myofibroblasts. The greatest potential is the combined effect of dexamethasone and olmesartan, while dexamethasone and olmesartan have the same potential.

Olmesartan inhibits transdifferentiation of rabbit’s valvular interstitial cells into myofibroblast based on α – smooth muscle actin expression

Recent studies revealed that differentiation of valvular interstitial cell (VIC) into myofibroblasts played an important role in valvular remodeling and fibrosis. Study was performed on in vitro cultured of VIC from New Zealand rabbit (Oryctolagus cuniculus). Isolated VIC was pretreated using 5 ng/mL of TGF-β1 and divided into groups of olmesartan (100 nanomol/L) as short 30 minutes exposure duration and as continuous 72 hours exposure duration. Inhibition of myofibroblast differentiation was quantified by the expression of α-SMA levels detected by immunofluorescence staining. Olmesartan administration either, as short 30 minutes exposure duration or as continuous 72 hours exposure duration, were significantly reduced TGF-β1-induced VIC differentiation into myofibroblast expressed by α-SMA levels compared to control (short 30 minutes exposure duration: 9.18 ±2.25, as continuous 72 hours exposure duration: 10.13 ±0.69, and control 22.29 ±2.78; p < 0.001), but without significant difference between the two treatment groups (p 0.403). Olmesartan both on short and continuous exposure can inhibit the differentiation of valve interstitial cells into myofibroblasts based on the expression of αSMA, but without a significant difference in the inhibitory effect.

Dihydromyricetin ameliorates osteogenic differentiation of human aortic valve interstitial cells by targeting c-KIT/interleukin-6 signaling pathway.

Aims: Calcific aortic valve disease (CAVD) is a chronic cardiovascular disease with high morbidity that lacks effective pharmacotherapeutics. As a natural flavonoid extracted from Ampelopsis grossedentata, dihydromyricetin (DHM) has been shown to be effective in protecting against atherosclerosis; yet, the therapeutic role of DHM in CAVD remains poorly understood. Herein, we aimed to clarify the therapeutic implications of DHM in CAVD and the underlying molecular mechanisms in human valvular interstitial cells (hVICs). Methods and Results: The protein levels of two known osteogenesis-specific genes (alkaline phosphatase, ALP; runt-related transcription factor 2, Runx2) and calcified nodule formation in hVICs were detected by Western blot and Alizarin Red staining, respectively. The results showed that DHM markedly ameliorated osteogenic induction medium (OM)–induced osteogenic differentiation of hVICs, as evidenced by downregulation of ALP and Runx2 expression and decreased calcium deposition. The SwissTargetPrediction database was used to identify the potential AVC-associated direct protein target of DHM. Protein–protein interaction (PPI) analysis revealed that c-KIT, a tyrosine-protein kinase, can act as a credible protein target of DHM, as evidenced by molecular docking. Mechanistically, DHM-mediated inhibition of c-KIT phosphorylation drove interleukin-6 (IL-6) downregulation in CAVD, thereby ameliorating OM-induced osteogenic differentiation of hVICs and aortic valve calcification progression. Conclusion: DHM ameliorates osteogenic differentiation of hVICs by blocking the phosphorylation of c-KIT, thus reducing IL-6 expression in CAVD. DHM could be a viable therapeutic supplement to impede CAVD.

Effects of Cyproheptadine on Mitral Valve Remodeling and Regurgitation After Myocardial Infarction

BackgroundIschemic mitral regurgitation (MR) is primarily caused by left ventricle deformation, but leaflet thickening with fibrotic changes are also observed in the valve. Increased levels of 5-hydroxytryptamine (5-HT; ie, serotonin) are described after myocardial infarction (MI); 5-HT can induce valve fibrosis through the 5-HT type 2B receptor (5-HT2BR). ObjectivesThis study aims to test the hypothesis that post-MI treatment with cyproheptadine (5-HT2BR antagonist) can prevent ischemic MR by reducing the effect of serotonin on mitral biology. MethodsThirty-six sheep were divided into 2 groups: inferior MI and inferior MI treated with cyproheptadine (0.5 mg/kg/d). Animals were followed for 90 days. Blood 5-HT, infarct size, left ventricular volume and function, MR fraction and mitral leaflet size were assessed. In a complementary in vitro study, valvular interstitial cells were exposed to pre-MI and post-MI serum collected from the experimental animals. ResultsIncreased 5-HT levels were observed after MI in nontreated animals, but not in the group treated with cyproheptadine. Infarct size was similar in both groups (11 ± 3 g vs 9 ± 5 g; P = 0.414). At 90 days, MR fraction was 16% ± 7% in the MI group vs 2% ± 6% in the cyproheptadine group (P = 0.0001). The increase in leaflet size following MI was larger in the cyproheptadine group (+40% ± 9% vs +22% ± 12%; P = 0.001). Mitral interstitial cells overexpressed extracellular matrix genes when treated with post-MI serum, but not when exposed to post-MI serum collected from treated animals. ConclusionsCyproheptadine given after inferior MI reduces post-MI 5-HT levels, prevents valvular fibrotic remodeling, is associated with larger increase in mitral valve size and less MR.

The tyrosine kinase inhibitor nilotinib targets the discoidin domain receptor DDR2 in calcific aortic valve stenosis.

Background and PurposeTyrosine kinase inhibitors (TKI) used to treat chronic myeloid leukaemia (CML) have been associated with cardiovascular side effects, including reports of calcific aortic valve stenosis. The aim of this study was to establish the effects of first and second generation TKIs in aortic valve stenosis and to determine the associated molecular mechanisms.Experimental ApproachHyperlipidemic APOE*3Leiden.CETP transgenic mice were treated with nilotinib, imatinib or vehicle. Human valvular interstitial cells (VICs) were isolated and studied in vitro. Gene expression analysis was perfromed in aortic valves from 64 patients undergoing aortic valve replacement surgery.Key ResultsNilotinib increased murine aortic valve thickness. Nilotinib, but not imatinib, promoted calcification and osteogenic activation and decreased autophagy in human VICs. Differential tyrosine kinase expression was detected between healthy and calcified valve tissue. Transcriptomic target identification revealed that the discoidin domain receptor DDR2, which is preferentially inhibited by nilotinib, was predominantly expressed in human aortic valves but markedly downregulated in calcified valve tissue. Nilotinib and selective DDR2 targeting in VICs induced a similar osteogenic activation, which was blunted by increasing the DDR2 ligand, collagen.Conclusions and ImplicationsThese findings suggest that inhibition of DDR2 by nilotinib promoted aortic valve thickening and VIC calcification, with possible translational implications for cardiovascular surveillance and possible personalized medicine in CML patients.

PTP1B Inhibition Improves Mitochondrial Dynamics to Alleviate Calcific Aortic Valve Disease Via Regulating OPA1 Homeostasis

There are currently no pharmacological therapies for calcific aortic valve disease (CAVD). Here, we evaluated the role of protein tyrosine phosphatase 1B (PTP1B) inhibition in CAVD. Up-regulation of PTP1B was critically involved in calcified human aortic valve, and PTP1B inhibition had beneficial effects in preventing fibrocalcific response in valvular interstitial cells and LDLR-/- mice. In addition, we reported a novel function of PTP1B in regulating mitochondrial homeostasis by interacting with the OPA1 isoform transition in valvular interstitial cellosteogenesis. Thus, these findings have identified PTP1B as a potential target for preventing aortic valvecalcification in patients with CAVD.

4-Octyl itaconate suppresses the osteogenic response in aortic valvular interstitial cells via the Nrf2 pathway and alleviates aortic stenosis in mice with direct wire injury

Calcific aortic valve disease (CAVD) is the most prevalent valvular heart disease in older individuals, but there is a lack of drug treatment. The cellular biological mechanisms of CAVD are still unclear. Oxidative stress and endoplasmic reticulum stress (ER stress) have been suggested to be involved in the progression of CAVD. Many studies have demonstrated that 4-octyl itaconate (OI) plays beneficial roles in limiting inflammation and oxidative injury. However, the potential role of OI in CAVD has not been thoroughly explored. Thus, we investigated OI-mediated modulation of ROS generation and endoplasmic reticulum stress to inhibit osteogenic differentiation in aortic valve interstitial cells (VICs). In our study, calcified aortic valves showed increased levels of ER stress and superoxide anion, as well as abnormal expression of Hmox1 and NQO1. In VICs, OI activated the Nrf2 signaling cascade and contributed to Nrf2 stabilization and nuclear translocation, thus augmenting the expression of genes downstream of Nrf2 (Hmox1 and NQO1). Moreover, OI ameliorated osteogenic medium (OM)-induced ROS production, mitochondrial ROS levels and the loss of mitochondrial membrane potential in VICs. Furthermore, OI attenuated the OM-induced upregulation of ER stress markers, osteogenic markers and calcium deposition, which were blocked by the Nrf2-specific inhibitor ML385. Interestingly, we found that OM-induced ER stress and osteogenic differentiation were ROS-dependent and that Hmox1 silencing triggered ROS production, ER stress and elevated osteogenic activity, which were inhibited by NAC. Overexpression of NQO1 mediated by adenovirus vectors significantly suppressed OM-induced ER stress and osteogenic markers. Collectively, these results showed the anti-osteogenic effects of OI on AVICs by regulating the generation of ROS and ER stress by activating the Nrf2 signaling pathway. Furthermore, OI alleviated aortic stenosis in a mouse model with direct wire injury. Due to its antioxidant properties, OI could be a potential drug for the prevention and/or treatment of CAVD.

Melatonin Inhibits NF-κB/CREB/Runx2 Signaling and Alleviates Aortic Valve Calcification.

Calcific aortic valve disease (CAVD) is linked to high mortality. Melatonin inhibits nuclear factor-kappa B (NF-κB)/cyclic AMP response element-binding protein (CREB), contributing to CAVD progression. This study determined the role of melatonin/MT1/MT2 signaling in valvular interstitial cell (VIC) calcification. Western blotting and Alizarin red staining were used to analyze NF-κB/CREB/runt-related transcription factor 2 (Runx2) signaling in porcine VICs treated with an osteogenic (OST) medium without (control) or with melatonin for 5 days. Chromatin immunoprecipitation (ChIP) assay was used to analyze NF-κB's transcription regulation of NF-κB on the Runx2 promoter. OST medium-treated VICs exhibited a greater expression of NF-κB, CREB, and Runx2 than control VICs. Melatonin treatment downregulated the effects of the OST medium and reduced VIC calcification. The MT1/MT2 antagonist (Luzindole) and MT1 receptor neutralized antibody blocked the anticalcification effect of melatonin, but an MT2-specific inhibitor (4-P-PDOT) did not. Besides, the NF-κB inhibitor (SC75741) reduced OST medium-induced VIC calcification to a similar extent to melatonin at 10 nmol/L. The ChIP assay demonstrated that melatonin attenuated OST media increased NF-κB binding activity to the promoter region of Runx2. Activation of the melatonin/MT1-axis significantly reduced VIC calcification by targeting the NF-κB/CREB/Runx2 pathway. Targeting melatonin/MT1 signaling may be a potential therapeutic strategy for CAVD.

Fibroblast growth factor 2 inhibits myofibroblastic activation of valvular interstitial cells.

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

Osteopontin activity modulates sex-specific calcification in engineered valve tissue mimics.

Patients with aortic valve stenosis (AVS) have sexually dimorphic phenotypes in their valve tissue, where male valvular tissue adopts a calcified phenotype and female tissue becomes more fibrotic. The molecular mechanisms that regulate sex-specific calcification in valvular tissue remain poorly understood. Here, we explored the role of osteopontin (OPN), a pro-fibrotic but anti-calcific bone sialoprotein, in regulating the calcification of female aortic valve tissue. Recognizing that OPN mediates calcification processes, we hypothesized that aortic valvular interstitial cells (VICs) in female tissue have reduced expression of osteogenic markers in the presence of elevated OPN relative to male VICs. Human female valve leaflets displayed reduced and smaller microcalcifications, but increased OPN expression relative to male leaflets. To understand how OPN expression contributes to observed sex dimorphisms in valve tissue, we employed enzymatically degradable hydrogels as a 3D cell culture platform to recapitulate male or female VIC interactions with the extracellular matrix. Using this system, we recapitulated sex differences observed in human tissue, specifically demonstrating that female VICs exposed to calcifying medium have smaller mineral deposits within the hydrogel relative to male VICs. We identified a change in OPN dynamics in female VICs in the presence of calcification stimuli, where OPN deposition localized from the extracellular matrix to perinuclear regions. Additionally, exogenously delivered endothelin-1 to encapsulated VICs increased OPN gene expression in male cells, which resulted in reduced calcification. Collectively, our results suggest that increased OPN in female valve tissue may play a sex-specific role in mitigating mineralization during AVS progression.

Sestrin2 Is Increased in Calcific Aortic Disease and Inhibits Osteoblastic Differentiation in Valvular Interstitial Cells via the Nuclear Factor E2-related Factor 2 Pathway.

Sestrin2 (Sesn2) is involved in the progression of cardiovascular diseases, such as hypertension and myocardial infarction. This study aimed to examine Sesn2 expression in human calcific aortic valve disease (CAVD) and explore its possible mechanisms by which Sesn2 participates in this process. CAVD and normal aortic valves were collected. Sesn2 expression and sources were examined, and the results showed that Sesn2 expression was increased in aortic valves from patients with CAVD and was mainly secreted by macrophages. Additionally, U937 macrophages were pretreated with si-Sesn2 or cDNA-Sesn2 and further treated with oxidized low-density lipoprotein (ox-LDL); M1 macrophages and their markers were measured, and we found that pretreatment with si-Sesn2 increased ox-LDL-induced M1 macrophage polarization and marker mRNA levels, whereas pretreatment with cDNA-Sesn2 had the opposite effects. In ox-LDL-treated U937 macrophages, oxidative stress levels were increased in the si-Sesn2 pretreatment group and further increased by si-Nrf2 treatment, whereas oxidative stress levels were decreased in the cDNA-Sesn2 pretreatment group and significantly reversed by ML385, a specific Nrf2 inhibitor. The effects of Sesn2 on ox-LDL-induced oxidative stress and the osteogenic differentiation of ox-LDL-induced valvular interstitial cells (VICs) was examined by down-regulating Nrf2 pathway. When U937 macrophages were co-cultured with VICs, downregulation of Sesn2 increased ox-LDL-induced osteogenic differentiation in VICs, whereas overexpression of Sesn2 exerted the opposite effects. Our study suggests that Sesn2 is increased in CAVD aortic valves and may participate in the development of CAVD by regulating oxidative stress via the Nrf2 pathway.

Oxidative Stress in Calcific Aortic Valve Stenosis: Protective Role of Natural Antioxidants.

Calcific aortic valve stenosis (CAVS) is the most prevalent heart valvular disease worldwide and a slowly progressive disorder characterized by thickening of the aortic valve, calcification, and subsequent heart failure. Valvular calcification is an active cell regulation process in which valvular interstitial cells involve phenotypic conversion into osteoblasts/chondrocytes-like cells. The underlying pathophysiology is complicated, and there have been no pharmacological treatments for CAVS to date. Recent studies have suggested that an increase in oxidative stress is the major trigger of CAVS, and natural antioxidants could ameliorate the detrimental effects of reactive oxygen species in the pathogenesis of CAVS. It is imperative to review the current findings regarding the role of natural antioxidants in CAVS, as they can be a promising therapeutic approach for managing CAVS, a disorder currently without effective treatment. This review summarizes the current findings on molecular mechanisms associated with oxidative stress in the development of valvular calcification and discusses the protective roles of natural antioxidants in the prevention and treatment of CAVS.

Implication of TRPM4 ionic channel in osteogenic differentiation of human valvular interstitial cells

The Ca2 + -activated non selective cationic channel, TRPM4, is involved in cardiac fibroblasts remodelling. In valvular interstitial cells (VIC), with similar properties than fibroblasts, its expression at the mRNA level was reported to be higher in conditions of valvular calcification leading to aortic stenosis. Endothelial dysfunction, followed by inflammation and fibrosis, promote the differentiation of VIC into osteoblastic phenotype cells which is, at term, responsible of valve ossification. The purpose of this study is to search for a potential implication of TRPM4 into osteogenic differentiation of human VIC. Human aortic valves are obtained from surgery for valve replacement. VIC are isolated by enzymatic digestion then maintained in culture. VIC are incubated during 14 days in a pro-calcific mixture in the presence or not of 9-phenanthrol, a pharmacological inhibitor of TRPM4. Expression and functionality of this channel were followed respectively by Western Blot and electrophysiological recordings in the inside-out configuration of the patch clamp technique. The implication of TRPM4 in VIC mineralization process was observed by measuring calcific crystals using alizarin red staining. A typical TRPM4 single channel current was detected in VIC in culture with a single channel conductance of 20 pS, a monovalent cationic permeability as well as voltage and calcium sensitivity. Protein expression of TRPM4 was confirmed by Western Blot. Pharmacological inhibition of the channel by 9-phenanthrol (3.10–6 M), during culture, reduced the mineralization by 30% without affecting cell viability. Thereby, TRPM4 would participate in osteogenic differentiation of human VIC in culture. Further studies are needed to understand which mecanisms link TRPM4 and ostegenic differentiation.

Surface Modification of Polytetrafluoroethylene and Polycaprolactone Promoting Cell-Selective Adhesion and Growth of Valvular Interstitial Cells.

Tissue engineering concepts, which are concerned with the attachment and growth of specific cell types, frequently employ immobilized ligands that interact preferentially with cell types of interest. Creating multicellular grafts such as heart valves calls for scaffolds with spatial control over the different cells involved. Cardiac heart valves are mainly constituted out of two cell types, endothelial cells and valvular interstitial cells. To have control over where which cell type can be attracted would enable targeted cell settlement and growth contributing to the first step of an engineered construct. For endothelial cells, constituting the outer lining of the valve tissue, several specific peptide ligands have been described. Valvular interstitial cells, representing the bulk of the leaflet, have not been investigated in this regard. Two receptors, the integrin α9β1 and CD44, are known to be highly expressed on valvular interstitial cells. Here, we demonstrate that by covalently grafting the corresponding peptide and polysaccharide ligand onto an erodible, polycaprolactone (PCL), and a non-degradable, polytetrafluoroethylene (PTFE), polymer, surfaces were generated that strongly support valvular interstitial cell colonization with minimal endothelial cell and reduced platelet adhesion. The technology for covalent binding of corresponding ligands is a key element towards tissue engineered cardiac valves for in vitro applications, but also towards future in vivo application, especially in combination with degradable scaffold material.

MO759: Indoxyl-Sulfate Activation of the AhR-NFΚB Pathway Promotes IL-6 Secretion and Subsequent Osteogenic Transition and Calcification of Interstitial Cells of the Aortic Valve

Abstract BACKGROUND AND AIMS Calcific aortic valve disease (CAVD) results from fibro-calcific degeneration of the aortic valve leaflets, causing haemodynamic disorders and major cardiovascular complications. In chronic kidney disease (CKD) patients, this pathological remodelling is more frequent, appears earlier, progresses more rapidly and leads to a mortality rate three times higher than in the general population. The uremic toxin indoxyl-sulfate (IS) is a powerful predictor of cardiovascular mortality in CKD patients and a strong promoter of aortic calcification. However, its role in aortic valve leaflets mineralization has never been studied. This work aimed to evaluate whether IS can influence the mineralization of primary human valvular interstitial cells (hVICs) cultured in vitro. METHOD Primary hVICs were isolated from aortic tricuspid valves collected from patients with CAVD undergoing valve replacement surgery at the Amiens Picardie University Hospital. The concentrations of IS used in this study were selected according to the EUTOX registry: IS normal [Isn]: 0.5 µg/mL, IS uremic [Isu]: 37 µg/mL and IS maximum [Ismax]: 233 µg/mL. Human VICs mineralization were induced by exposure to an osteogenic medium containing 2.4 mmol/L calcium and 2.5 mmol/L phosphate (pro-calcific condition) and quantified by the o-cresolphthalein complexone method. The osteogenic transition of hVICs was assessed by qRT-PCR following Bmp2 and Runx2 mRNA expression. The cells’ inflammatory potential was assessed by qRT-PCR and ELISA following IL-1β, IL-6 and TNF-α expression and secretion. Activation of NFkB pathway was studied by analysing the phosphorylation of P65 via western blot. A siRNA approach was used to determine the signaling pathway involved in the effects of IS. RESULTS In pro-calcific conditions, IS increased hVICs osteogenic transition and calcification in a concentration-dependent manner, an effect that was blocked in hVICs transfected with siRNA targeting AhR expression. Data obtained by western blot showed that the exposure to [ISu] and [ISmax] promoted P65 phosphorylation in an AhR dependent manner. Blockade of the NFкB pathway with siRNA targeting P65 inhibited IS-induced expression of Bmp2 and RunX2 as well as hVICs mineralization, suggesting that hVICs inflammation plays a key role in the procalcific effects of IS. Confirming this hypothesis, the exposure to [ISu] and [ISmax] increased the expression of IL-1β, IL-6 and TNF-α transcripts, an effect abolished by silencing AhR and P65. Interestingly, hVICs did not secrete TNF-α and produced only a very low quantity of IL-1β in response to IS. By contrast, the exposure to [ISu] and [ISmax] induced an important release of IL-6 in hVICs culture medium, which was blocked when AhR and P65 were silenced. In this model, the use of an antibody neutralizing IL-6 completely abolished IS-induced hVICs osteogenic transition and calcification. CONCLUSION Our study demonstrates that IS displays direct pro-calcific effects on primary hVICs through AhR-dependent activation of the NFkB pathway and subsequent release of IL-6. We report that the autocrine action of IL-6 is responsible for IS-induced hVICs osteogenic transition and calcification. The observation that antibodies neutralizing IL-6 can block IS pro-calcific effects might be of particular interest knowing that interventional studies evaluating the cardiovascular impact of anti-IL-6 antibodies in patients with CKD are underway.

Hydrogel cultures reveal Transient Receptor Potential Vanilloid 4 regulation of myofibroblast activation and proliferation in valvular interstitial cells.

As aortic valve stenosis develops, valve tissue becomes stiffer. In response to this change in environmental mechanical stiffness, valvular interstitial cells (VICs) activate into myofibroblasts. We aimed to investigate the role of mechanosensitive calcium channel Transient Receptor Potential Vanilloid type 4 (TRPV4) in stiffness induced myofibroblast activation. We verified TRPV4 functionality in VICs using live calcium imaging during application of small molecule modulators of TRPV4 activity. We designed hydrogel biomaterials that mimic mechanical features of healthy or diseased valve tissue microenvironments, respectively, to investigate the role of TRPV4 in myofibroblast activation and proliferation. Our results show that TRPV4 regulates VIC proliferation in a microenvironment stiffness-independent manner. While there was a trend toward inhibiting myofibroblast activation on soft microenvironments during TRPV4 inhibition, we observed near complete deactivation of myofibroblasts on stiff microenvironments. We further identified Yes-activated protein (YAP) as a downstream target for TRPV4 activity on stiff microenvironments. Mechanosensitive TRPV4 channels regulate VIC myofibroblast activation, whereas proliferation regulation is independent of the microenvironmental stiffness. Collectively, the data suggests differential regulation of stiffness-induced proliferation and myofibroblast activation. Our data further suggest a regulatory role for TRPV4 regarding YAP nuclear localization. TRPV4 is an important regulator for VIC myofibroblast activation, which is linked to the initiation of valve fibrosis. Although more validation studies are necessary, we suggest TRPV4 as a promising pharmaceutical target to slow aortic valve stenosis progression.

A disease-driver population within interstitial cells of human calcific aortic valves identified via single-cell and proteomic profiling.

Cellular heterogeneity of aortic valves complicates the mechanistic evaluation of the calcification processes in calcific aortic valve disease (CAVD), and animal disease models are lacking. In this study, we identify a disease-driver population (DDP) within valvular interstitial cells (VICs). Through stepwise single-cell analysis, phenotype-guided omic profiling, and network-based analysis, we characterize the DDP fingerprint as CD44highCD29+CD59+CD73+CD45low and discover potential key regulators of human CAVD. These DDP-VICs demonstrate multi-lineage differentiation and osteogenic properties. Temporal proteomic profiling of DDP-VICs identifies potential targets for therapy, including MAOA and CTHRC1. Invitro loss-of-function experiments confirm our targets. Such a stepwise strategy may be advantageous for therapeutic target discovery in other disease contexts.