Calcific aortic stenosis: a disease ready for prime time

Platelet membrane-coated alterbrassicene A nanoparticle inhibits calcification of the aortic valve by suppressing phosphorylation P65 NF-κB

Rationale: Calcific aortic valve disease (CAVD) is a leading cause of cardiovascular mortality and morbidity with increasing prevalence and incidence. The pathobiology of CAVD involves valvular fibrocalcification, and osteogenic and fibrogenic activities are elevated in aortic valve interstitial cells (VICs) from diseased valves. It has been demonstrated that activated NF-κB pathway was present in the early stage of CAVD process. There is currently no effective clinical drugs targeting NF-κB pathway for CAVD treatment. Therefore, it is of great clinical significance to seek effective treatments for valve calcification. Methods: In this study, we established immortal human valve interstitial cells (im-hVICs) with pGMLV-SV40T-puro lentivirus. Alizarin red staining and western blotting were performed to evaluate the calcification of immortal VICs supplemented with different compounds. The natural fusicoccane diterpenoid alterbrassicene A (ABA) was found to have potential therapeutic functions. Ribonucleic acid sequencing was used to identify the potential target of ABA. Platelet membrane-coated nanoparticle of ABA (PNP-ABA) was fabricated and the IBIDI pump was used to evaluate the adhesion ability of PNP-ABA. Murine wire-induced aortic valve stenosis model was conducted for in vivo study of PNP-ABA. Results: The natural fusicoccane diterpenoid ABA was found to significantly reduce the calcification of human VICs during osteogenic induction via inhibiting the phosphorylation P65. Runt-related transcription factor 2 (Runx2) and bone morphogenetic protein-2 (BMP2) were down regulated with the treatment of ABA in human VICs. Additionally, molecular docking results revealed that ABA bound to RelA (P65) protein. Phosphorylation of P65 (Ser536) was alleviated by ABA treatment, as well as the nuclear translocation of P65 during osteogenic induction in human VICs. Alizarin red staining showed that ABA inhibited osteogenic differentiation of VICs in a dose-dependent manner. PNP-ABA attenuated aortic valve calcification in murine wire-induced aortic valve stenosis model in vivo. Conclusions: The establishment of im-hVICs provides a convenient cell line for the study of CAVD. Moreover, our current research highlights a novel natural compound, ABA, as a promising candidate to prevent the progression of CAVD.

Aortic stenosis: a review on acquired pathogenesis and ominous combination with diabetes mellitus

BACKGROUND

Aortic stenosis (AS) is a progressive disease, with no pharmacological treatment. The prevalence of diabetes mellitus (DM) among AS patients is higher than in the general population. DM significantly increases the risk of AS development and progression from mild to severe. The interplay between AS and DM's mechanism is not entirely known yet.

MAIN BODY

The increased accumulation of advanced glycation end products (AGEs) was linked to increased valvular oxidative stress, inflammation, expression of coagulation factors, and signs of calcification, according to an analysis of aortic stenotic valves. It is interesting to note that in diabetic AS patients, valvular inflammation did not correlate with serum glucose levels but rather only with long-term glycemic management markers like glycated haemoglobin and fructosamine. Transcatheter aortic valve replacement, which has been shown to be safer than surgical aortic valve replacement, is advantageous for AS patients who also have concurrent diabetes. Additionally, novel anti-diabetic medications have been proposed to lower the risk of AS development in DM patients, including sodium-glucose cotransporter-2 inhibitors and glucagon-like peptide-1 receptor agonist that target reduction of AGEs-mediated oxidative stress.

CONCLUSIONS

There are little data on the effects of hyperglycemia on valvular calcification, but understanding the interactions between them is essential to develop a successful treatment strategy to stop or at least slow the progression of AS in DM patients. There is a link among AS and DM and that DM negatively impacts the quality of life and longevity of AS patients. The sole successful treatment, despite ongoing efforts to find new therapeutic modalities, involves aortic valve replacement. More research is required to find methods that can slow the advancement of these conditions, enhancing the prognosis and course of people with AS and DM.

Trans-Aortic Flow Turbulence and Aortic Valve Inflammation: A Pilot Study Using Blood Speckle Imaging and 18F-Sodium Fluoride Positron Emission Tomography/Computed Tomography in Patients With Moderate Aortic Stenosis

BACKGROUND

¹⁸F-sodium fluoride positron emission tomography/computed tomography (¹⁸F-NaF PET/CT) has been proven to be useful in identification of microcalcifications, which are stimulated by inflammation. Blood speckle imaging (BSI) is a new imaging technology used for tracking the flow of blood cells using transesophageal echocardiography (TEE). We evaluated the relationship between turbulent flow identified by BSI and inflammatory activity of the aortic valve (AV) as indicated by the ¹⁸F-NaF uptake index in moderate aortic stenosis (AS) patients.

METHODS

This study enrolled 18 moderate AS patients diagnosed within the past 6 months. BSI within the aortic root was acquired using long-axis view TEE. The duration of laminar flow and the turbulent flow area ratio were calculated by BSI to demonstrate the degree of turbulence. The maximum and mean standardized uptake values (SUVmax, SUVmean) and the total microcalcification burden (TMB) as measured by ¹⁸F-NaF PET/CT were used to demonstrate the degree of inflammatory activity in the AV region.

RESULTS

The mean SUVmean, SUVmax, and TMB were 1.90 ± 0.79, 2.60 ± 0.98, and 4.20 ± 2.18 mL, respectively. The mean laminar flow period and the turbulent area ratio were 116.1 ± 61.5 msec and 0.48 ± 0.32. The correlation between SUVmax and turbulent flow area ratio showed the most positive and statistically significant correlation, with a Pearson's correlation coefficient (R²) of 0.658 and a p-value of 0.014.

CONCLUSIONS

The high degree of trans-aortic turbulence measured by BSI was correlated with severe AV inflammation.

Circulating Monocyte Subsets and Transcatheter Aortic Valve Replacement

Transcatheter aortic valve replacement (TAVR), as an alternative to open heart surgery, has revolutionized the treatment of severe aortic valve stenosis (AVS), the most common valvular disorder in the elderly. AVS is now considered a form of atherosclerosis and, like the latter, partly of inflammatory origin. Patients with high-grade AVS have a highly disturbed blood flow associated with high levels of shear stress. The immediate reopening of the valve during TAVR leads to a sudden restoration of a normal blood flow hemodynamic. Despite its good prognosis for patients, TAVR remains associated with bleeding or thrombotic postprocedural complications, involving mechanisms that are still poorly understood. Many studies report the close link between blood coagulation and inflammation, termed thromboinflammation, including monocytes as a major actor. The TAVR procedure represents a unique opportunity to study the influence of shear stress on human monocytes, key mediators of inflammation and hemostasis processes. The purpose of this study was to conduct a review of the literature to provide a comprehensive overview of the impact of TAVR on monocyte phenotype and subset repartition and the association of these parameters with the clinical outcomes of patients with severe AVS who underwent TAVR.

Rac1 mediates cadherin-11 induced cellular pathogenic processes in aortic valve calcification

BACKGROUND

Calcific aortic valve disease (CAVD), a major cause for surgical aortic valve replacement, currently lacks available pharmacological treatments. Cadherin-11 (Cad11), a promising therapeutic target, promotes aortic valve calcification in vivo, but direct Cad11 inhibition in clinical trials has been unsuccessful. Targeting of downstream Cad11 effectors instead may be clinically useful; however, the downstream effectors that mediate Cad11-induced aortic valve cellular pathogenesis have not been investigated.

APPROACH AND RESULTS

Immunofluorescence of calcified human aortic valves revealed that GTP-Rac1 is highly upregulated in calcified leaflets and is 2.15 times more co-localized with Cad11 in calcified valves than GTP-RhoA. Using dominant negative mutants in porcine aortic valve interstitial cells (PAVICs), we show that Cad11 predominantly regulates Runx2 nuclear localization via Rac1. Rac1-GEF inhibition via NSC23766 effectively reduces calcification in ex vivo porcine aortic valve leaflets treated with osteogenic media by 2.8-fold and also prevents Cad11-induced cell migration, compaction, and calcification in PAVICs. GTP-Rac1 and Trio, a known Cad11 binding partner and Rac1-GEF, are significantly upregulated in Nfatc1Cre; R26-Cad11Tg/Tg (Cad11 OX) mice that conditionally overexpress Cad11 in the heart valves by 3.1-fold and 6.3-fold, respectively. Finally, we found that the Trio-specific Rac1-GEF inhibitor, ITX3, effectively prevents Cad11-induced calcification and Runx2 induction in osteogenic conditions.

CONCLUSION

Here we show that Cad11 induces many cellular pathogenic processes via Rac1 and that Rac1 inhibition effectively prevents many Cad11-induced aortic disease phenotypes. These findings highlight the therapeutic potential of blocking Rac1-GEFs in CAVD.

Induction of aortic valve calcification by celecoxib and its COX-2 independent derivatives is glucocorticoid-dependent

BACKGROUND

Celecoxib, a selective cyclooxygenase-2 inhibitor, was recently associated with increased incidence of aortic stenosis and found to produce a valvular calcification risk in vitro. Several cyclooxygenase-2 independent celecoxib derivatives have been developed and identified as possible therapies for inflammatory diseases due to their cadherin-11 inhibitory functions. Potential cardiovascular toxicities associated with these cyclooxygenase-2 independent celecoxib derivatives have not yet been investigated. Furthermore, the mechanism by which celecoxib produces valvular toxicity is not known.

METHODS AND RESULTS

Celecoxib treatment produces a 2.8-fold increase in calcification in ex vivo porcine aortic valve leaflets and a more than 2-fold increase in calcification in porcine aortic valve interstitial cells cultured in osteogenic media. Its cyclooxygenase-2 independent derivative, 2,5-dimethylcelecoxib, produces a similar 2.5-fold increase in calcification in ex vivo leaflets and a 13-fold increase in porcine aortic valve interstitial cells cultured in osteogenic media. We elucidate that this offtarget effect depends on the presence of either of the two media components: dexamethasone, a synthetic glucocorticoid used for osteogenic induction, or cortisol, a natural glucocorticoid present at basal levels in the fetal bovine serum. In the absence of glucocorticoids, these inhibitors effectively reduce calcification. By adding glucocorticoids or hydrocortisone to a serum substitute lacking endogenous glucocorticoids, we show that dimethylcelecoxib conditionally induces a 3.5-fold increase in aortic valve calcification and osteogenic expression. Treatment with the Mitogen-activated protein kinase kinase inhibitor, U0126, rescues the offtarget effect, suggesting that celecoxib and dimethylcelecoxib conditionally augment Mitogen-activated protein kinase kinase/extracellular-signal-regulated kinase activity in the presence of glucocorticoids.

CONCLUSION

Here we identify glucocorticoids as a possible source of the increased valvular calcification risk associated with celecoxib and its cyclooxygenase-2 independent derivatives. In the absence of glucocorticoids, these inhibitors effectively reduce calcification. Furthermore, the offtarget effects are not due to the drug's intrinsic properties as dual cyclooxygenase-2 and cadherin-11 inhibitors. These findings inform future design and development of celecoxib derivatives for potential clinical therapy.

Overexpression of Biglycan is Associated with Resistance to Rapamycin in Human WERI-Rb-1 Retinoblastoma Cells by Inducing the Activation of the Phosphatidylinositol 3-Kinases (PI3K)/Akt/Nuclear Factor kappa B (NF-κB) Signaling Pathway

Background

Biglycan (BGN) is an extracellular matrix (ECM) protein that regulates the growth of epithelial cells. The mammalian target of rapamycin (mTOR) inhibitor, rapamycin, is a treatment for advanced retinoblastoma. This study aimed to investigate the effects of expression of BGN on the response of human WERI-Rb-1 retinoblastoma cells to rapamycin and to investigate the associated signaling pathways.

Material/Methods

BGN gene expression was induced in human WERI-Rb-1 retinoblastoma cells, which were incubated with rapamycin at doses of 0, 5, 10, 20, 30, and 50 μg/ml. Cells were treated with the PI3K/Akt pathway inhibitor, LY294002. The MTT assay determined the rate of cell inhibition. Real-time polymerase chain reaction (RT-PCR) was performed to measure BGN gene expression using RT²-PCR. Western blot detected the protein levels of BGN, p-PI3K, p-Akt, nuclear NF-κB, and p65.

Results

Rapamycin impaired cell growth, induced cell apoptosis, and suppressed the expression levels of p-PI3K, p-Akt, nuclear NF-κB, and p65. Overexpression of the BGN gene restored growth potential and inhibited apoptosis and was associated with the activation of the PI3K/Akt-mediated NF-κB pathway. In cells that overexpressed BGN, inhibition of the PI3K/Akt pathway by LY294002 increased the sensitivity of human WERI-Rb-1 retinoblastoma cells to rapamycin.

Conclusions

Overexpression of BGN induced rapamycin resistance in WERI-Rb-1 retinoblastoma cells by activating PI3K/Akt/NF-κB signaling.

Involvement of inflammatory responses in the early development of calcific aortic valve disease: lessons from statin therapy

Calcific aortic valve disease (CAVD) is the most common degenerative heart valve disease. Among the many risk factors for this disease are age, hypercholesterolemia, hypertension, smoking, type-2 diabetes, rheumatic fever, and chronic kidney disease. Since many of these overlap with risk factors for atherosclerosis, the molecular and cellular mechanisms of CAVD development have been presumed to be similar to those for atherogenesis. Thus, attempts have been made to evaluate the therapeutic efficacy of statins, representative anti-atherosclerosis drugs with lipid-lowering and anti-inflammatory effects, against CAVD. Unfortunately, statins have shown little or no effect on CAVD development. But some reports suggest that statins may prevent or reduce the development of early stage CAVD in which having calcification is absent or minimal. These results suggest that therapeutic approaches should differ according to the stage of disease, and that a precise understanding of the mechanism of aortic valve calcification is required to identify novel therapeutic targets for advanced CAVD. Given the involvement of inflammatory processes in the development and progression of CAVD, current therapeutic approaches for chronic inflammatory cardiovascular disease like atherosclerosis may help to prevent or minimize the early development of CAVD. In this review, we focus on several inflammatory cellular and molecular components involved in CAVD that might be considered drug targets for preventing CAVD.

Biglycan promotes the chemotherapy resistance of colon cancer by activating NF-κB signal transduction

Biglycan (BGN) is overexpressed in cancer stem cells of colon cancer and induces the activation of NF-κB pathway which contributes to the chemotherapy resistance of diverse cancer types. Therefore, we hypothesized that the overexpression of BGN also promoted the development of multiple drug resistance (MDR) in colon cancer via NF-κB pathway. The expression of BGN was bilaterally modulated in colon cancer cell lines HT-29 and SW-480 and the effect of treatments on the cell proliferation and resistance to 5-FU was assessed. Moreover, the role of NF-κB signaling in the BGN-mediated formation of MDR was further investigated by subjecting BGN-overexpressed SW-480 cells to the co-treatment of chemo-agents and NF-κB inhibitor, PDTC. The inhibition of BGN expression decreased the proliferation potential of HT-29 cells while the induction of BGN expression increased the potential of SW-480 cells. BGN knockdown increased HT-29 cells' sensitivity to 5-FU, represented by the lower colony number and higher apoptotic rate. To the contrary, BGN overexpression promoted the resistance of SW-480 cells to 5-FU. The effect of BGN modulation on colon cancer cells was associated with the changes in apoptosis and NF-κB pathways: BGN inhibition increased the expressions of pro-apoptosis indicators and suppressed NF-κB pathway activity while BGN overexpression had the opposite effect. It was also found that the BGN-mediated formation of MDR was impaired when NF-κB pathway was blocked. Findings outlined in the current study showed that BGN contributed to the formation of chemotherapy resistance in colon cancer cells by activating NF-κB signaling.

A clinical perspective on the utility of alpha 1 antichymotrypsin for the early diagnosis of calcific aortic stenosis

Background

Calcific aortic stenosis (CAS) is the most common heart valve disease in the elderly, representing an important economic and social burden in developed countries. Currently, there is no way to predict either the onset or progression of CAS, emphasizing the need to identify useful biomarkers for this condition.

Methods

We performed a multi-proteomic analysis on different kinds of samples from CAS patients and healthy donors: tissue, secretome and plasma. The results were validated in an independent cohort of subjects by immunohistochemistry, western blotting and selected reaction monitoring.

Results

Alpha 1 antichymotrypsin (AACT) abundance was altered in the CAS samples, as confirmed in the validation phase. The significant changes observed in the amounts of this protein strongly suggest that it could be involved in the molecular mechanisms underlying CAS. In addition, our results suggest there is enhanced release of AACT into the extracellular fluids when the disease commences.

Conclusions

The significant increase of AACT in CAS patients suggests it fulfils an important role in the physiopathology of this disease. These results permit us to propose that AACT may serve as a potential marker for the diagnosis of CAS, with considerable clinical value.

Relation Between Epicardial Adipose and Aortic Valve and Mitral Annular Calcium Determined by Computed Tomography in Subjects Aged ≥65 Years

Epicardial adipose tissue (EAT) has been linked to coronary artery calcium deposits and atherosclerotic disease. Mitral annular (MAC) and aortic valve calcium (AVC) have also been associated with atherosclerosis. This study examined the possible relation between EAT thickness and valvular calcium deposits. We included 294 patients aged ≥65 years who had noncontrast computed tomography scans of the chest. Mean age was 76 ± 7 years; 47% were men. Using reconstructed images, EAT thickness was measured at various locations. MAC and AVC were quantified by Agatston technique. The sum of AVC and MAC was reported as the grand total score (GTS). Subjects were divided into 2 groups based on the value of GTS; GTS = 0, no cardiac calcification and GTS ≥1, cardiac calcification group. Epicardial fat (left and right atrioventricular grooves and superior interventricular groove) was significantly greater in the cardiac calcification group compared with the no cardiac calcification (all values, p <0.05). After adjusting for clinical variables including BMI, EAT at the superior interventricular groove remained significantly associated with total calcium. Left atrioventricular groove EAT demonstrated a trend toward an association with total calcium, but this did not reach statistical significance. In conclusion, epicardial fat is associated with calcium deposits of the mitral annulus and aortic valve.

Cellular Changes during Renal Failure-Induced Inflammatory Aortic Valve Disease

Background

Aortic valve calcification (AVC) secondary to renal failure (RF) is an inflammation-regulated process, but its pathogenesis remains unknown. We sought to assess the cellular processes that are involved in the early phases of aortic valve disease using a unique animal model of RF-associated AVC.

Methods

Aortic valves were obtained from rats that were fed a uremia-inducing diet exclusively for 2, 3, 4, 5, and 6 weeks as well as from controls. Pathological examination of the valves included histological characterization, von Kossa staining, and antigen expression analyses.

Results

After 2 weeks, we noted a significant increase in urea and creatinine levels, reflecting RF. RF parameters exacerbated until the Week 5 and plateaued. Whereas no histological changes or calcification was observed in the valves of any study group, macrophage accumulation became apparent as early as 2 weeks after the diet was started and rose after 3 weeks. By western blot, osteoblast markers were expressed after 2 weeks on the diet and decreased after 6 weeks. Collagen 3 was up-regulated after 3 weeks, plateauing at 4 weeks, whereas collagen 1 levels peaked at 2 and 4 weeks. Fibronectin levels increased gradually until Week 5 and decreased at 6 weeks. We observed early activation of the ERK pathway, whereas other pathways remained unchanged.

Conclusions

We concluded that RF induces dramatic changes at the cellular level, including macrophage accumulation, activation of cell signaling pathway and extracellular matrix modification. These changes precede valve calcification and may increase propensity for calcification, and have to be investigated further.

The lipid theory in the pathogenesis of calcific aortic stenosis

AIMS

Biologically active phenomena, triggered by atherogenesis and inflammation, lead to aortic valve (AV) calcification. Lipids play an important role in activating the cell signaling leading to AV bone deposition. This review, based on evidence from animal and human studies, mainly focused on the involvement of lipids and atherogenic phenomena in the pathogenesis of calcific aortic stenosis (AS).

DATA SYNTHESIS

The role of elevated low density lipoproteins for the risk of both vascular atherosclerosis and AS has been elucidated. Lipid disorders act synergistically with other risk factors to increase prevalence of calcific AS. Atherosclerosis is also involved in the pathogenesis of bone demineralization, a typical hallmark of aging, which is associated with ectopic calcification at vascular and valvular levels. Animal studies have recently contributed to demonstrate that lipids play an important role in AS pathogenesis through the activation of molecular cell signalings, such as Wnt/Lrp5 and RANK/RANKL/Osteprotegerin, which induce the transition of valvular myofibroblasts toward an osteogenic phenotype with consequent valvular bone deposition. Although all these evidence strongly support the lipid theory in AS pathogenesis, lipids lowering therapies failed to demonstrate in controlled trials a significant efficacy to slow AS progression. Encouraging results from animal studies indicate that physical activity may counteract the biological processes inducing AV degeneration.

CONCLUSIONS

This review indicates a robust interplay between lipids, inflammation, and calcific AS. This new pathophysiological scenario of such an emerging valvular disease paves the way to the next challenge of cardiovascular research: "prevent and care aortic valve stenosis".

Decorin and biglycan retain LDL in disease-prone valvular and aortic subendothelial intimal matrix

OBJECTIVE

Subendothelial LDL retention by intimal matrix proteoglycans is an initial step in atherosclerosis and calcific aortic valve disease. Herein, we identify decorin and biglycan as the proteoglycans that preferentially retain LDL in intimal matrix at disease-prone sites in normal valve and vessel wall.

METHODS

The porcine aortic valve and renal artery ostial diverter, initiation sites of calcific valve disease and renal atherosclerosis, respectively, from normal non-diseased animals were used as models in these studies.

RESULTS

Fluorescent human LDL was selectively retained on the lesion-prone collagen/proteoglycan-enriched aortic surface of the valve, where the elastic lamina is depleted, as previously observed in lesion-prone sites in the renal ostium. iTRAQ mass spectrometry of valve and diverter protein extracts identified decorin and biglycan as the major subendothelial intimal matrix proteoglycans electrostatically retained on human LDL affinity columns. Decorin levels correlated with LDL binding in lesion-prone sites in both tissues. Collagen binding to LDL was shown to be proteoglycan-mediated. All known basement membrane proteoglycans bound LDL suggesting they may modulate LDL uptake into the subendothelial matrix. The association of purified decorin with human LDL in an in vitro microassay was blocked by serum albumin and heparin suggesting anti-atherogenic roles for these proteins in vivo.

CONCLUSIONS

LDL electrostatic interactions with decorin and biglycan in the valve leaflets and vascular wall is a major source of LDL retention. The complementary electrostatic sites on LDL or these proteoglycans may provide a novel therapeutic target for preventing one of the earliest events in these cardiovascular diseases.

[The "asymptomatic" patient with chronic acquired heart valve disease]

An intervention for chronic acquired valvular heart disease may either be indicated in symptomatic patients to relieve symptoms and improve quality of life or in asymptomatic patients to improve long-term prognosis, e.g., by preventing disease-related complications like chronic heart failure or arrhythmias. For proper action according to current guidelines, the systematic evaluation of symptoms related to the underlying valve disease is of utmost importance. If a discrepancy between symptoms reported or not reported by the patients and the severity of the valve disease is supposed, true absence of symptoms and exercise tolerance should be verified by spiroergometry. In the truly asymptomatic patient with a severe valvular lesion, preservation of myocardial adaption to the chronic volume or pressure overload should be tested utilizing appropriate imaging techniques like radionuclide ventriculography under exercise conditions. The proper evaluation of the functional status is of growing importance in our aging population with its sedentary lifestyle. In this context, the results of a survey should be kept in mind, which indicated that a significant proportion of patients still have interventions too late during the natural history of their valve disease with symptoms of congestive heart failure, arrhythmias, and the risk of sudden cardiac death persisting after a primarily successful valve repair or replacement.

Ex vivo evidence for the contribution of hemodynamic shear stress abnormalities to the early pathogenesis of calcific bicuspid aortic valve disease

The bicuspid aortic valve (BAV) is the most common congenital cardiac anomaly and is frequently associated with calcific aortic valve disease (CAVD). The most prevalent type-I morphology, which results from left-/right-coronary cusp fusion, generates different hemodynamics than a tricuspid aortic valve (TAV). While valvular calcification has been linked to genetic and atherogenic predispositions, hemodynamic abnormalities are increasingly pointed as potential pathogenic contributors. In particular, the wall shear stress (WSS) produced by blood flow on the leaflets regulates homeostasis in the TAV. In contrast, WSS alterations cause valve dysfunction and disease. While such observations support the existence of synergies between valvular hemodynamics and biology, the role played by BAV WSS in valvular calcification remains unknown. The objective of this study was to isolate the acute effects of native BAV WSS abnormalities on CAVD pathogenesis. Porcine aortic valve leaflets were subjected ex vivo to the native WSS experienced by TAV and type-I BAV leaflets for 48 hours. Immunostaining, immunoblotting and zymography were performed to characterize endothelial activation, pro-inflammatory paracrine signaling, extracellular matrix remodeling and markers involved in valvular interstitial cell activation and osteogenesis. While TAV and non-coronary BAV leaflet WSS essentially maintained valvular homeostasis, fused BAV leaflet WSS promoted fibrosa endothelial activation, paracrine signaling (2.4-fold and 3.7-fold increase in BMP-4 and TGF-β1, respectively, relative to fresh controls), catabolic enzyme secretion (6.3-fold, 16.8-fold, 11.7-fold, 16.7-fold and 5.5-fold increase in MMP-2, MMP-9, cathepsin L, cathepsin S and TIMP-2, respectively) and activity (1.7-fold and 2.4-fold increase in MMP-2 and MMP-9 activity, respectively), and bone matrix synthesis (5-fold increase in osteocalcin). In contrast, BAV WSS did not significantly affect α-SMA and Runx2 expressions and TIMP/MMP ratio. This study demonstrates the key role played by BAV hemodynamic abnormalities in CAVD pathogenesis and suggests the dependence of BAV vulnerability to calcification on the local degree of WSS abnormality.

Proteomic profile of human aortic stenosis: insights into the degenerative process

Degenerative aortic stenosis is the most common worldwide cause of valve replacement. While it shares certain risk factors with coronary artery disease, it is not delayed or reversed by reducing exposure to risk factors (e.g., therapies that lower lipids). Therefore, it is necessary to better understand its pathophysiology for preventive measures to be taken. In this work, aortic valve samples were collected from 20 patients that underwent aortic valve replacement (55% males, mean age of 74 years) and 20 normal control valves were obtained from necropsies (40% males, mean age of 69 years). The proteome of the samples was analyzed by quantitative differential electrophoresis (2D-DIGE) and mass spectrometry, and 35 protein species were clearly increased in aortic valves, including apolipoprotein AI, alpha-1-antitrypsin, serum albumin, lumican, alfa-1-glycoprotein, vimentin, superoxide dismutase Cu-Zn, serum amyloid P-component, glutathione S-transferase-P, fatty acid-binding protein, transthyretin, and fibrinogen gamma. By contrast, 8 protein species were decreased (transgelin, haptoglobin, glutathione peroxidase 3, HSP27, and calreticulin). All of the proteins identified play a significant role in cardiovascular processes, such as fibrosis, homeostasis, and coagulation. The significant changes observed in the abundance of key cardiovascular proteins strongly suggest that they can be involved in the pathogenesis of degenerative aortic stenosis. Further studies are warranted to better understand this process before we can attempt to modulate it.

Molecular imaging insights into early inflammatory stages of arterial and aortic valve calcification

Traditional imaging modalities such as computed tomography, although perfectly adept at identifying and quantifying advanced calcification, cannot detect the early stages of this disorder and offer limited insight into the mechanisms of mineral dysregulation. This review presents optical molecular imaging as a promising tool that simultaneously detects pathobiological processes associated with inflammation and early stages of calcification in vivo at the (sub)cellular levels. Research into treatment of cardiovascular calcification is lacking, as shown by clinical trials that have failed to demonstrate the reduction of calcific aortic stenosis. Hence, the need to elucidate the pathways that contribute to cardiovascular calcification and to develop new therapeutic strategies to prevent or reverse calcification has driven investigations into the use of molecular imaging. This review discusses studies that have used molecular imaging methods to advance knowledge of cardiovascular calcification, focusing in particular on the inflammation-dependent mechanisms of arterial and aortic valve calcification.

Molecular imaging insights into early inflammatory stages of arterial and aortic valve calcification

Traditional imaging modalities such as computed tomography, although perfectly adept at identifying and quantifying advanced calcification, cannot detect the early stages of this disorder and offer limited insight into the mechanisms of mineral dysregulation. This review presents optical molecular imaging as a promising tool that simultaneously detects pathobiological processes associated with inflammation and early stages of calcification in vivo at the (sub)cellular levels. Research into treatment of cardiovascular calcification is lacking, as shown by clinical trials that have failed to demonstrate the reduction of calcific aortic stenosis. Hence, the need to elucidate the pathways that contribute to cardiovascular calcification and to develop new therapeutic strategies to prevent or reverse calcification has driven investigations into the use of molecular imaging. This review discusses studies that have used molecular imaging methods to advance knowledge of cardiovascular calcification, focusing in particular on the inflammation-dependent mechanisms of arterial and aortic valve calcification.

Statins for progression of aortic valve stenosis and the best evidence for making decisions in health care

In the Western world, calcified aortic valve stenosis is the most common form of valvular heart disease, affecting up to 3% of adults over the age of 75 years. It is a gradually progressive disease, characterized by a long asymptomatic phase that may last for several decades, followed by a short symptomatic phase associated with severe restriction of the valve orifice. Investigations on treatments for aortic valve stenosis are still in progress. Thus, it is believed that calcification of aortic valve stenosis is similar to the process of atherosclerosis that occurs in coronary artery disease. Recent studies have suggested that cholesterol lowering through the use of statins may have a salutary effect on the progression of aortic valve stenosis.

Mechanical strain and the aortic valve: influence on fibroblasts, extracellular matrix, and potential stenosis

BACKGROUND

Mechanical strain may affect aortic valve cusp, leading to an altered extracellular matrix ultrastructure and eventually aortic stenosis. The aim of this study was to evaluate the affect of these potential relationships on human tissue.

METHODS

Extracellular matrix protein disposition was analyzed on human aortic valve cusp retrieved from 31 patients during routine aortic valve replacement surgery. Samples were immediately fixed in 2-hydroxyethyl methacrylate. Immunohistology and Western blot analysis were used to quantify decorin, tenascin-C, biglycan, alkaline-phosphatase, osteocalcin, and osteopontin content. Fibroblast function was analyzed on interstitial cells derived from aortic valve cups from patients undergoing aortic valve replacement. Cells were grown to confluency in modified Eagle's medium supplemented with 10% fetal calf serum under sterile conditions. Thereafter, mechanical strain was applied for 72 hours and 60 cycles per minute. Elongation of as much as 10% in comparison with no elongation (control group) was applied. All results were correlated to hemodynamic variables.

RESULTS

Decorin and biglycan were mostly located at the inflow aspects of the cusp, tenascin-C in the central layer, and osteopontin, osteocalcin, and alkaline phosphatase were concentrated near the cell populations surrounding calcified areas. The intensity of this protein expression was significantly related to the pressure gradient. Expression levels were twice to five times higher than normal in patients with a preoperative pressure gradient of more than 100 mm Hg. On fibroblasts subjected to mechanical strain, a similar significant increase in the expression for decorin, biglycan, alkaline-phosphatase, tenascin-C, osteocalcin, and osteopontin was found by immunohistology. Western blot analysis confirmed significantly enhanced expressions of two and eight times the normal levels.

CONCLUSIONS

A specific pattern of extracellular matrix protein expression was found in relation to mechanical strain on human aortic valve cusp tissue and in mechanically stimulated human valvular fibroblasts. This new insight into the process of aortic valve degeneration may be important for further therapeutic approaches to ameliorate the progression or even the initiation of potential aortic valve stenosis.

The 'valvulo-metabolic' risk in calcific aortic valve disease

Calcific aortic stenosis (AS) has been considered a degenerative and unmodifiable process resulting from aging and 'wear and tear' of the aortic valve. Over the past decade, studies in the field of epidemiology, molecular biology and lipid metabolism have highlighted similarities between vascular atherosclerosis and calcific AS. In particular, work from the Quebec Heart Institute and from that of others has documented evidence of valvular infiltration by oxidized low-density lipoproteins and the presence of inflammatory cells, along with important tissue remodelling in valves explanted from patients with AS. Recent studies have also emphasized the role of visceral obesity in the development and progression of AS. In addition, visceral obesity, with its attendant metabolic complications, commonly referred to as the metabolic syndrome, has been associated with degenerative changes in bioprosthetic heart valves. The purpose of the present review is to introduce the concept of 'valvulo-metabolic risk' and to provide an update on the recent and important discoveries regarding the pathogenesis of heart valve diseases in relation to obesity, and to discuss how these novel mechanisms might translate into clinical practice.

Reduced EGFR causes abnormal valvular differentiation leading to calcific aortic stenosis and left ventricular hypertrophy in C57BL/6J but not 129S1/SvImJ mice

Epidermal growth factor receptor (EGFR) signaling contributes to aortic valve development in mice. Because developmental phenotypes in Egfr-null mice are dependent on genetic background, the hypomorphic Egfr(wa2) allele was made congenic on C57BL/6J (B6) and 129S1/SvImJ (129) backgrounds and used to identify the underlying cellular cause of EGFR-related aortic valve abnormalities. Egfr(wa2/wa2) mice on both genetic backgrounds develop aortic valve hyperplasia. Many B6-Egfr(wa2/wa2) mice die before weaning, and those surviving to 3 mo of age or older develop severe left ventricular hypertrophy and heart failure. The cardiac phenotype was accompanied by significantly thicker aortic cusps and larger transvalvular gradients in B6-Egfr(wa2/wa2) mice compared with heterozygous controls and age-matched Egfr(wa2) homozygous mice on either 129 or B6129F1 backgrounds. Histological analysis revealed cellular changes in B6-Egfr(wa2/wa2) aortic valves underlying elevated pressure gradients and progression to heart failure, including increased cellular proliferation, ectopic cartilage formation, extensive calcification, and inflammatory infiltrate, mimicking changes seen in human calcific aortic stenosis. Despite having congenitally enlarged valves, 129 and B6129F1-Egfr(wa2/wa2) mice have normal lifespans, absence of left ventricular hypertrophy, and normal systolic function. These results show the requirement of EGFR activity for normal valvulogenesis and demonstrate that dominantly acting genetic modifiers curtail pathological changes in congenitally deformed valves. These studies provide a novel model of aortic sclerosis and stenosis and suggest that long-term inhibition of EGFR signaling for cancer therapy may have unexpected consequences on aortic valves in susceptible individuals.

Evaluation and management of aortic valve and root disease

Aortic valve disease manifests in the form of stenosis, regurgitation, or some combination, yielding either excessive afterload and/or excessive preload on the left ventricle. Aortic root disease may affect valvular function, causing regurgitation; may simply be coexistent with stenotic aortic valvular disease; or may exist despite normal aortic valve function. Indications for intervening on aortic valve or root disease are determined by the presence of symptoms, by the pathology's impact on left ventricular function, or by the inherent risk of aortic catastrophe (dissection, disruption, or sudden death). Aortic valvular and root diseases are primarily treated by surgical replacement of the pathologic structures. Mechanical aortic valve replacement has long-term durability but requires continuous anticoagulation. Bioprostheses do not require anticoagulation but have more limited durability. Valve-sparing aortic root replacement and aortic valve repair offer the potential for indefinite durability without the need for anticoagulation but are technically more difficult to perform and require more stringent selection criteria based on determining the reparability of an aortic valve. Emerging percutaneous valve technologies offer new hope for patients who are not candidates for aortic valve surgery, but the applicability and durability of percutaneous aortic valves are not yet known. Timely and appropriate intervention in aortic valve and root disease can result in the restoration of a normal life span for patients with aortic valvular and/or root disease.

Timing of operation in asymptomatic severe aortic stenosis

Calcific aortic stenosis is now the main cause of aortic stenosis in the majority of patients, due to declining incidence of rheumatic fever. Risk factors such as hyperlipidemia play an important role in the progression of aortic stenosis. According to the most recent American College of Cardiology/American Heart Association guidelines, peak velocity greater than 4 m/sec, a mean gradient of more than 40 mmHg and a valve area of less than 1.0 cm(2) is considered hemodynamically severe aortic stenosis. Aortic valve surgery promptly should be done in symptomatic patients due to dismal prognosis without operation. Features such as high aortic valve calcium and positive exercise test identify asymptomatic patients who would benefit from early aortic valve surgery. Due to improvement in surgical techniques and better prosthesis, aortic valve surgery can now be offered at low risk to a selected group of asymptomatic patients with severe aortic stenosis. Currently percutaneous aortic valves are used in very high-risk patients with severe symptomatic aortic stenosis. Their role may expand in the future, depending on the improvements in design and operator experience. Whether advances in molecular cardiology lead to novel therapies in preventing calcific aortic stenosis in the future remains to be seen.

Risk factors for progression of calcific aortic stenosis and potential therapeutic targets

Current thought regarding the progression of calcific aortic stenosis (AS) is presented. After summarizing contemporary ideas about AS pathogenesis, the present article examines the factors that may affect disease progression. Data indicate that this process may be accelerated by aortic valve structure, degree of valvular calcification, chronic renal insufficiency and cardiovascular risk factors such as diabetes and dyslipidemia. Finally, the present review discusses potential therapeutic targets to slow AS progression.