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Statins for Calcific Aortic ValveStenosis: Into Oblivion After

SALTIRE and SEAS? An ExtensiveReview from Bench to Bedside

Hadewich Hermans, MD, Paul Herijgers, MD, PhD,Paul Holvoet, PhD, Eric Verbeken, MD, PhD,

Bart Meuris, MD, PhD, Willem Flameng, MD, PhD,and Marie-Christine Herregods, MD, PhD

Abstract: Calcific aortic stenosis is the most frequent heartvalve disease and the main indication for valve replacementin western countries. For centuries attributed to a passivewear and tear process, it is now recognized that aorticstenosis is an active inflammatory and potentially modifiablepathology, with similarities to atherosclerosis. Statins werefirst-line candidates for slowing down progression of thedisease, as established drugs in primary and secondarycardiovascular prevention. Despite promising animal exper-iments and nonrandomized human trials, the prospectiverandomized trials SEAS and SALTIRE did not confirm theexpected benefit. We review SEAS and SALTIRE startingwith the preceding studies and discuss basic science experi-ments covering the major known contributors to the patho-physiology of calcific aortic valve disease, to conclude with ahypothesis on the absent effect of statins, and suggestionsfor further research paths. (Curr Probl Cardiol 2010;
35:284-306.)
C alcific aortic valve disease is a common and progressive pathol-ogy. The prevalence of sclerosis is reported to be �25% in thepopulation aged �65 years; the prevalence of severe aortic valve

tenosis is reported to be �2.5% in the population aged �75 years and

he authors have no conflicts of interests to disclose.adewich Hermans, MD, is supported by the Flanders Research Foundation (FWO) to prepare a PhD thesis.urr Probl Cardiol 2010;35:284-306.
146-2806/$ – see front matteroi:10.1016/j.cpcardiol.2010.02.002
84 Curr Probl Cardiol, June 2010

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8% in the population aged �85 years.1 Aortic valve stenosis (AS) is therimary indication for valve replacement in western countries, and theumber will only increase as elderly people are a growing subpopulation.t present the only established therapy for AS is valve replacement.2

edical prevention of progression is a subject of substantial research fordecade as it was recognized that aortic valve disease is not only a

assive wear and tear process but an active inflammatory process withistopathologic changes and risk profile similar to atherosclerosis, occur-ing from the age of 35 years. This generated possible targets for therapy.tatins were first-line candidates as commercially available drugs withstablished benefit in primary and secondary cardiovascular preventiony atherosclerosis stabilization. Retrospective studies3-7 and prospectiveonrandomized studies8,9 have shown that statins significantly slowedown progression. SEAS10 and SALTIRE,11 being the only prospectiveandomized trials published to date, did not confirm the effect of statinsn rate of progression. How come?

hat Preceded SALTIRE and SEAS?

pidemiology and Histopathology: (Dis)Similaritiesetween Calcific Aortic Valve Disease andtherosclerosisSince the Helsinki Aging Study12 and Cardiovascular Health Study,13 it

s recognized that calcific aortic valve disease and atherosclerosis show anverlap in clinical risk factors, ie, age, male gender, hypertension,moking, dyslipidemia, renal dysfunction, and diabetes. However, there iso absolute correlation as only 33% of the patients in the Euro Hearturvey underwent concomitant coronary artery bypass grafting (CABG)t aortic valve replacement (AVR).14 Histopathologic comparison re-ealed that both entities are characterized by accumulation of (oxidized)ow-density lipoprotein (oxLDL), inflammation, calcification, and boneormation.15-17 We have to emphasize that there are also differences:alcification occurs much earlier in AS, the most prominent cell type isot the smooth muscle cell but the “fibroblast,” and plaque instability ashe cause of symptoms is not a main issue in contrast to atherosclerosis.

nimal Experiments: Based on a Dyslipidemic ModelTo date, the only animal experiment showing benefit of statins is AS,

oncerns a hypercholesterolemic rabbit model.18 As such, this might onlye translated to patients with dyslipidemia as the facilitating factor. The
uest for drug therapy is hampered by the lack of a low-cost spontaneous
urr Probl Cardiol, June 2010 285

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nimal model. Only aging swine develop valvular sclerosis without annciting factor,19 while the other species require diets or genetic muta-ions. The rabbit models are based on high-cholesterol diets with orithout vitamin D supplementation.18,20-25 The mouse models are eitheryslipidemic like the rabbit models, by diets or by mutations in the lipidetabolism (apolipoprotein, LDL receptor, apolipoproteinB), or are based onutations in players of calcification and bone formation (endothelial nitric

xide synthase (eNOS), matrix gla protein, and Notch1 or Madh6) and asuch they might not mirror the development and progression of the diseasen humans where AS develops at later age by a complex inflammatoryrocess.26-33

alini M. Rajamannan: In 2009, the current use of hyperlipidemic animalodels, whether genetic or diet-induced, provides a foundation for evolving

tudies in the field of calcific aortic valve disease. The authors are correct thathe published animal models do not recapitulate fully human calcific aorticalve disease. Each published model, to date, has provided unique cellulareatures that recapitulate the published discoveries important in the pheno-ype of calcification in the aortic valve. The eNOS null mouse by Lee TC, etl,28 expresses bicuspid aortic valves in only 27% of the mouse colonies andot spontaneous calcification. The genetic mouse model that has demon-trated severe aortic stenosis in a third of the mice over a 2-year period is theeversa mouse published by Weiss RM, et al.32 This mouse model is the first

o develop severe stenosis in a third of the mouse cohorts studied.

etrospective Observational Studies: Patients on Statinsor Established IndicationEarly 2000 retrospective observational studies were reported (Table 1).3-7

ote that consequently all patients received statins in primary or second-ry prevention, and note that in the stage of aortic valve disease, nonencluded sclerosis. Aronow focused on aortic valve calcification; the otherroups focused on hemodynamic severity. All investigators found aignificant benefit of statins on the parameters regardless of the degree ofS. As such, the authors concluded that statins might be beneficial in

dvanced stages of the evolutionary disease, considered the retrospectivend nonrandomized nature of the studies. The impact of cholesterol leveln hemodynamic progression was controversial: Aronow and Novaroescribed an association between cholesterol level and progression; in therials of Bellamy and Rosenhek they were unrelated.

alini M. Rajamannan: There is a recent publication by Antonini-Canterin F,
t al,98 demonstrating that there is a stage-related effect of statin treatment

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n the progression of aortic valve sclerosis and stenosis. This study alsoemonstrates the importance of treating the earlier stages of this diseaseith a notable difference in treatment effect.

rospective Nonrandomized Studies: Patients on Statinsor Established IndicationMoura et al performed the Rosuvastatin Affecting Aortic Valve endo-

helium to slow the progression of aortic stenosis study (RAAVE).8

lthough this study was prospective, it was nonrandomized comprisingnly 121 patients with moderate to severe AS; 61 of them were on statinsn accordance to current guidelines. Statins significantly slowed downemodynamic progression, but here again the observed effect of statinsannot be broadened to AS patients without dyslipidemia as facilitatingactor. Pohle et al performed electron beam tomography on 104 patientst baseline and after a mean interval of 15 months.9 Patients were dividedn 2 groups according to LDL cholesterol level: 57 patients �130 mg/dL,f which 39 were on statin treatment; and 47 patients �130 mg/dL, ofhich 15 were on statin treatment. All patients had progression of aorticalve calcification score, but progression was significantly less in theroup �130 mg/dL. Multiple regression analysis showed that LDL level

ABLE 1. Retrospective and prospective nonrandomized trials

Investigators(y)

n (n onstatins) Follow-up

Grade, AS atbaseline Endpoint Pro statins

etrospectiveAronow

(2001)180 (62) 2.75 � 1 y Mild �Pmax Yes (P � 0.01)

Novaro(2001)

174 (57) 1.75 � 0.6 y Mild to moderate �Pmax,AVA

Yes (P � 0.03)

Bellamy(2002)

156 (38) 3.7 � 2.3 y Mild to moderate AVA, Vmax Yes (P � 0.04)

Shavelle(2002)

65 (28) 2.5 � 1.6 y No hemodynamicevaluation

AVC Yes (P � 0.006)

Rosenhek(2004)

211 (82) 2.0 � 1.5 y Mild to severe AVA, Vmax Yes (P � 0.0001)

rospectiveRAAVE

(2007)121 (61) 1.4 � 0.46 y Moderate to

severeVmax Yes (P � 0.007)

bbreviations: y, year; n, number of patients; �Pmax, peak transaortic gradient; AVA, aorticalve area; Vmax, peak transaortic velocity; AVC, aortic valve calcium; RAAVE, Rosuvastatinffecting aortic valve endothelium to slow the progression of aortic valve stenosis.

as an independent predictor of progression, while age, smoking,


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ypertension, and diabetes were not. Statin use was not entered in theegression model, but the authors describe that the patients on statinreatment with LDL �130 mg/dL had a significantly slower progressionhan patients on insufficient dose to control plasma LDL and concludedhat adequate lipid-lowering decreases progression of AS.

alini M. Rajamannan: The RAAVE study was designed to treat patientsith elevated LDL and calcific aortic valve disease compared with patientsith normal LDL and calcific aortic valve disease, because of the ethical

ssues related to randomizing patients with elevated LDL to no statin after theeries of published papers demonstrating the clinical benefits of lipid lower-ng, for example, the 4-S trial. Lancet 344(8934):1383-9, 1994.

leiotropic Effects of Statin: Pathways Partly UnknownThe discrepancies regarding the association between cholesterol level

nd hemodynamic progression of AS give rise to the question of theechanisms by which statins slow down progression in patients with

yslipidemia: only by lipid lowering or in combination with pleiotropicffects. In atherosclerosis the importance of the pleiotropic effects oftatins on cardiovascular mortality and morbidity is well established; theathways and their relative contribution however are partly unknown.tatins are reported to cause an improvement of endothelial dysfunction,

o have anti-inflammatory and antioxidant effects, and to be capable oflaque stabilization, as is nicely reviewed by Davignon.34 The improve-ent of endothelial dysfunction is shown to be caused by increased NO

roduction: at first by diminished inhibition of eNOS-activity by loweringf LDL, as LDL is able to increase caveolin-1, an inhibitor of eNOS;econd, by enhancement of constitutive eNOS activity by (1) stabilizationf eNOS messenger RNA, (2) activation of Akt (protein kinase B) inndothelial cells and as such phosphorylation of its substrate eNOS, and3) prevention of translocation to the cell membrane of Rho GTPase withonsequently less negative regulation of eNOS. The antioxidant effect oftatins with less production of the cytotoxic oxLDL might be due to directiminution of the oxidative ability of macrophages, and to free radicalcavenging. On top statins might decrease the activity of macrophageD36, a receptor of oxLDL and as such foam cell formation. With

egards to the anti-inflammatory effect, statins are reported to cause aeduction of plasma C-reactive protein and reduction of adhesion mole-ules, the latter however with conflicting results. Plaque stabilization is
escribed as the net effect of the mechanisms discussed above, caused by

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smaller lipid core, less macrophages and T-lymphocytes, less apoptosis,nd more collagen content with less matrix metalloproteinase-2 (MMP-2),nd enhanced tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) im-unoreactivity. As conviction grew that AS has a genesis and evolution

imilar to atherosclerosis, the next step was the hypothesis that statins mighte able to influence the progression. There was preliminary proof of concepty the mentioned retrospective and prospective nonrandomized trials thataved the way for the setup of prospective randomized trials.

alini M. Rajamannan: The experimental studies in the field of vascularisease and statins have been clearly defined. The pleiotropic effects oftatins in the signaling pathways include eNOS, hsCRP, MMP-2, and TIMP-1.here is a growing body of literature in the field of aortic valve disease in vitrond in vivo demonstrating that statins have specific pleiotropic effects in thealve also, including the following: eNOS, Rajamannan et al. Atorvastatinnhibits calcification and enhances nitric oxide synthase production in theypercholesterolemic aortic valve. Heart 91(6):806-10, 2005; extracellularucleotides, Osman et al. A novel role of extracellular nucleotides in valvealcification: a potential target for atorvastatin. Circulation 114(1)(Suppl):

566-72, 2006; and inhibition of bone matrix synthesis, Wu B, et al.56

ALTIRE and SEAS

tudy AimThe investigators hypothesized that statins � ezetimibe slow down pro-ression of AS. SALTIRE had as primary endpoint progression in aortic jetelocity and computed tomography aortic valve calcium score, and asecondary endpoints, AVR, death from any cause, hospitalization for anyause, hospitalization for cardiovascular causes, and a composite of clinicalndpoints (death from cardiovascular causes, AVR, hospitalization attribut-ble to severe AS). The primary endpoint of SEAS was the composite ofardiovascular death, AVR, nonfatal myocardial infarction, congestive heartailure because of progression of AS, CABG, percutaneous coronaryntervention, hospitalized unstable angina, and nonhemorrhagic stroke.he secondary endpoints were aortic valve events (AVR, congestive heart

ailure because of progression of AS, and cardiovascular death), echo-ardiographic progression, and ischemic events (CABG, percutaneousoronary intervention, stroke, unstable angina, nonfatal myocardial in-arction, death from cardiovascular cause). The rationale for the compos-te primary endpoint was the assessment of aggressive lipid-lowering on
he entire cardiovascular burden in AS patients (Table 2).

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tudy Design and Baseline CharacteristicsThe trials were double-blind, randomized, and placebo-controlled, andEAS was multicenter. The inclusion criterion was asymptomatic calcificS, in SALTIRE with a peak jet velocity of at least 2.5 m/s, in SEASetween 2.5 and 4 m/s. Both had similar exclusion criteria namely age18 y, contraindications for or current therapy with statins, guidelines

ndication for statins, left ventricular dysfunction, significant valvularisease other than AS, uncontrolled hypertension, or renal insufficiency.s such, the study population of the 2 trials does not fully resemble theeneral AS population as the study cohorts had limited clinical riskactors for AS progression. All patients underwent echocardiography �omputed tomography at baseline, annually during follow-up, and attudy termination, while adverse effects and lipid profile were monitoredore frequently.

esultsSALTIRE did not show a significant reduction in AS progression rate,or in clinical endpoints. SEAS showed similar results, with the exceptionf a significant effect on ischemic events, dominated by a reduction of theeed for CABG in the simvastatin-ezetimibe group. SEAS did not have a

ABLE 2. Published prospective randomized trials

SALTIRE (2005) SEAS (2008)

(n on statins � ezetimibe) 155 (77) 1873 (944)ollow-up 2.08 y 4.35 yrade, AS at baseline Mild to severe Mild to moderaterimary endpoints Vmax (P � 0.95) Composite (P � 0.59)

AVC (P � 0.80)econdary endpoints Composite (P � 0.19) AVA, Vmax (P � 0.83)

Death from cardiovascularcauses (P � 1.0)

Aortic valve events(P � 0.73)

Aortic valve replacement(P � 0.17)

Ischemic events(P � 0.02)

Hospitalization for severeAS (P � 0.73)

Death from any cause(P � 0.73)

Hospitalization for anycause (P � 0.84)

Pro statins No No

Abbreviations: n, number of patients; Vmax, peak transaortic velocity; AVC, aortic valve calcium;VA, aortic valve area; SALTIRE, Scottish Aortic Stenosis and Lipid Lowering Trial, Impact onegression; SEAS, Simvastatin and Ezetimibe In Aortic Stenosis Study.

reatment group on simvastatin or ezetimibe alone. Long-term outcome


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rials of ezetimibe, acting on the intestinal sterol transporter, are notublished yet. As such, the relative contribution of both drugs on thisndpoint cannot be determined.

alini M. Rajamannan: The SEAS and SALTIRE investigators are pioneers inhe field of valvular heart disease trials. These studies provide valuablenformation for the future design of valvular heart disease trials. The design ofhese trials came out before the series of publications for the hyperlipidemicnimal models, which have contributed to the future design of clinical valverials.

ack to Basics: Pathophysiology of Aorticalve StenosisThe normal aortic valve leaflets are covered with endothelium, are

vascular, and consist of the 3 following layers: the ventricularis at theentricular side; the spongiosa; and the fibrosa at the aortic side of the leaflet.he ventricularis is composed of closely aligned elastin fibers; the spongiosaonsists of loose connective tissue, and the fibrosa contains collagenbers. The layers are populated by mesenchymal cells namely valve

nterstitial cells (VICs), maintaining leaflet integrity. The early lesion isharacterized by subendothelial plaque-like lesions at the aortic side, withrogressive infiltration of the adjacent fibrosa, and consists of accumula-ion of lipoproteins, inflammatory cells, and microcalcifications.15-17 Ashe lesion progresses, neo-angiogenesis is noted,35 a process of enhancedalcification, and active bone formation.36 While the AS lesion isharacterized at the microscopic level, the molecular pathways remainhallenging to unravel. We discuss the most studied pathways in thepatho)physiology as presented in Fig 1.

echanical Stress and Shear StressAlthough calcific AS is now recognized as an active process with

imilarities to atherosclerosis, instead of an unmodifiable pathology, dueo long-term mechanical stress and leading to passive accumulation ofalcium, caution is warranted to forget the contribution of increasedechanical and decreased or turbulent shear stress to the initiation and

rogression of AS. Patients with bicuspid valves present 2 decades earlierhan patients with tricuspid valves.37 Hypertension is a risk factor forS,12,13 and lesions are noted to initiate at the flexion area of the leafletshere stress is highest.38 All emphasizing the role of mechanical stress

urrently believed to be leading to endothelial disruption. The noncoro-


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ary cusp is often the first affected, probably by more pronouncedndothelial dysfunction as this cusp might encounter less shear stress thanhe coronary cusps due to absence of diastolic coronary flow. The fibrosas affected first as the aortic side of the valve is exposed to turbulent flow,hile the ventricularis is exposed to laminar flow.39 The molecularathways from stress to endothelial dysfunction are subjected to substan-ial research in the atherosclerosis field, with NO as a key player.40 Asoon as subendothelial lesions are present, endothelial dysfunction isaintained by oxLDL and inflammatory cells.41 The endothelium cov-

ring the valve leaflets, however, is distinct from vascular endothelium.e comment on this below.Regarding the role of mechanical and shear stress, we now leave the

IG 1. Pathophysiology of calcific aortic valve stenosis. Abbreviations: NO, nitric oxidep;CAM, intercellular adhesion molecule; VCAM, vascular cell adhesion molecule; TGF�,ransforming growth factor �; ACE, angiotensin converting enzyme; oxLDL, oxidized LDL;NF-�, tumor necrosis factor �; A1R, angiotensin receptor 1; B2R, bradykinin receptor 2; Lrp, low-density lipoprotein receptor-related protein 5; RANK, receptor activator of nuclear factorappa (B); RANKL, RANK ligand; NF-�B, nuclear factor kappa (B); cbfa-1, core binding factorlpha-1; Msx-2, msh homeobox 2; qVIC, quiescent valvular interstitial cell; obVIC, osteoblasticalvular interstitial cell; aVIC, activated valvular interstitial cell; EGF, vascular endothelialrowth factor; MMPs, matrix metalloproteinases; AS, aortic stenosis. (Color version of figure isvailable online.)

round paths. Quoting Robicsek et al and Singh et al, the importance of


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he functional assembly of the valve leaflets, corresponding sinuses, andinotubular junction is often overlooked.42,43 Intact sinuses and sinotu-ular junction create optimal distribution of pressure load and properalve opening and closure, while loss of aortic wall compliance leads toignificant stress overload of the leaflets. Loss of vascular complianceccurs in every aging subject due to gradual loss of elastin fibers in theedia and is more pronounced in patients with hypertension, diabetes,

nd renal failure, the latter due to superposition of media calcification. Asuch, the role of mechanical stress is not restricted to the initiating step,ut instead is continuous and progressive. Once sclerosis is initiated in theeaflets, the thickened and stiffened leaflets themselves also promotenfavorable stress distribution. This self-perpetuating process mightartly cause the failure of statins to slow down AS progression whendministrated at later stages.Recent reports on the molecular bridge between mechanical stress andS describe in vitro testing of intact porcine valves or aortic VICs. To

nterpret the results of in vitro experiments, remember that the aortic valves exposed to a composite of hemodynamic forces: during systole pulsatileressure and shear stress (laminar at the ventricularis, turbulent at the fibrosa),nd during diastole cyclic stretch and turbulent shear stress, transmitted to theICs by endothelial cells and matrix.44 Cell proliferation, apoptosis,

ollagen content, cathepsin S and K expression, MMP-1, -2, and -9xpression and activity increase with increased cyclic stretch, whileathepsin L expression, TIMP-1 expression, and activity are reduced.45

ransforming growth factor �1 (TGF�1) acts synergistically with cyclictress46 and is also a key player in upregulation of vascular cell adhesionolecule-1 and intercellular adhesion molecule 1 in the valvular endo-

helium at the aortic side in response to oscillatory shear stress.47 Thendothelium is also capable of regulating the mechanical properties of theortic valve cusps. Endothelin-1 leads to increase in cusp stiffness, whileerotonin has the opposite effect; both are endothelium-dependent effectsxerted on the VICs.48 The role of the valvular endothelium in vivo intress distribution, and how mechanotransduction to the VICs takes place,equires further research.

alvular EndotheliumThe endothelium is not a uniform organ, similarly functioning in the

ntire cardiovascular bed. Butcher et al highlighted that the valvularndothelium is distinct from the vascular endothelium. They showed thatn response to shear stress valvular endothelial cells respond by aligning
erpendicular and vascular endothelial cells parallel to the direction of the

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ow, with differences in focal adhesion arrangement and signal kinases.49

ubsequently they showed transcriptional differences between porcineortic valve and aortic endothelial cells exposed to laminar shear stress:alvular endothelial cells are less intrinsically inflammatory, althoughimilar antioxidant and anti-inflammatory genes are expressed and ex-ress more genes associated with chondrogenesis and less with osteogen-sis. In both cell types shear stress protected against calcification byownregulation of bone morphogenic protein 4, in valvular cells also bynhibition of cadherin-11 and in aortic cells by inhibition of periostin.50

s such, the effect of statins on endothelial dysfunction as described forascular endothelium might not be as pronounced for valvular endothe-ium.

alini M. Rajamannan: The gene expression of valve endothelium has beenescribed by Simmons CA, et al,19 demonstrates the unique genotype of thealve aortic endothelial surface versus the ventricular surface the geographicifferences that may contribute to the difference in the predisposition of thealve to calcify on the aortic surface.

ortic Valve Interstitial CellsAs discussed by Liu et al, the terms valvular fibroblasts and osteoblasts

hould be replaced by the at present known 5 phenotypes of valvularnterstitial cells: either embryonic progenitor, quiescent (qVICs), acti-ated (aVICs), progenitor (pVICs), or osteoblastic (ob)VICs.51 VICs areistinct mesenchymal cells that adapt to the valvular environment with ahange in phenotype with specific detectable markers. Embryonic pro-enitor endothelial/mesenchymal cells, present in the embryonic cardiacushions, give rise to qVICs by the developmental process of endothelial-o-mesenchymal transformation (EMT). Their role seems however notnished after the developmental period, as plasticity of aortic andulmonary valve endothelium was described, which might lead to theypothesis that EMT takes place again in adult valves in response tonjury, giving rise to pVICs.52,53 Quiescent VICs maintain physiologicalve structure and inhibit angiogenesis in the leaflets. They can give riseo activated and obVICs in response to a number of chemokines androwth factors, one of the most important being TGF� from activatedndothelium. Activated VICs contain �-smooth-muscle actin and respondo valve injury and mechanical forces by repair processes includingroliferation, migration, and matrix remodeling. ObVICs participate in
alcification, osteogenesis, and chondrogenesis and secrete alkaline phos-

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hatase, osteocalcin, osteopontin, and bone sialoprotein. The least definedhenotype is the pVIC that might originate from the heart valve, the bonearrow via the circulation, or the endothelium via EMT and is CD-34-,D-133-, and/or S100-positive. In case of in vitro experiments, next to

he VIC phenotype used, also the culture conditions should meticulouslye described as the passage number; cell density and matrix all affect thehenotype via incompletely known pathways. Recent intriguing papersescribe that VIC-differentiation and -calcification is regulated by extra-ellular matrix stiffness, as is the efficacy of statin treatment. Yip et alescribe that on compliant calcifying matrices VICs transform to ansteoblast phenotype and form calcification noduli by active deposition.n a stiff matrix, however, they transform to an �-smooth-muscle

ctin-expressing phenotype with apoptosis-dependent dystrophic calcifi-ation. On the stiff matrix, calcification was strongly enhanced byGF�1, but not on compliant matrices, where the VICs expressed lessGF� receptor I.54 This is important, as in current opinion, “myofibro-lasts” are transforming to “osteoblasts” in the evolution of AS, while thistudy implicates that the main cell type might be the “osteoblast” orbVIC in the early stage and the “myofibroblast” or aVIC in the latertage. Monzack et al reported that the inhibiting and even dissipatingffect of simvastatin on calcific nodule formation was dose-dependent,atrix-dependent, and time-dependent.55 In most VIC studies cells are

ultured on unmodified tissue culture polystyrene (TCPS), but theyultured the cells also on TCPS coated with either laminin or fibrin andound that the effect of simvastatin was more pronounced in lamininCPS. Their time experiments showed that the effect of simvastatin wasnly significant when applied within 1 hour after application of TGF�.dding to the importance of time dependency of statin admission, Wu et

l described that simvastatin inhibited dystrophic calcification by valvemyofibroblasts,” but promoted calcific nodule formation by “osteo-lasts,”56 analogous to the “statin paradox” described in osteoporosisesearch. Anger et al showed that statin therapy enhanced phosphorylatedRK in end-stage AS, which might enhance proliferative degeneration.57

These experiments underscore the absolute necessity of studying theomplete in vivo evolution of the disease, with attention for macrome-hanics, cells and cell types, matrix composition, and matrix microme-hanics to understand the pathophysiology, and investigate drug effects,ncluding timing of administration. With the advent of molecular imagings described by Aikawa et al, this could be in the near future for animal
odels, but not yet for patients.33

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alini M. Rajamannan: Aortic valve myofibroblast cell is a mesenchymal-erived cell that has the ability to differentiate to different valve phenotypes

ncluding a robust osteogenic phenotype. Chen JH, et al. Identification andharacterization of aortic valve mesenchymal progenitor cells with robuststeogenic calcification potential. Am J Pathol 174(3):1109-19, 2009.

xtracellular MatrixTo date, little is known about the evolution of extracellular matrix,

lthough primordial to understand both cell-cell- and cell-matrix commu-ication. Comparison of degenerative aortic valves obtained at replace-ent surgery and normal valves at heart transplantation learned that the

iseased valves have an extensive matrix remodeling process, with as aesult disrupted basal membranes, more collagen than elastin, andpportunity for invasion of inflammatory cells and neoangiogenesis. TheMPs and cathepsins are the most studied. An increase of MMP-1, -3,

nd -9 have consistently been reported, while the effect on their inhibitorsIMP-1 and -2 have shown conflicting results.58-60 Cathepsin S, K, V,nd G are significantly increased in stenotic aortic valves, with cathepsin

being highly expressed in activated mast cells.61,62 The importance ofnflammation is underscored by colocalization of TGF�1 and cathepsin Gn mast cells, and of tumor necrosis factor-� with MMP-1.62,63 Remem-er that both inflammation and mechanical stress are reported to be ableo upregulate matrix remodeling and can act synergistically as describedbove.

alini M. Rajamannan: Grande-Allen KJ, et al. Glycosaminoglycan synthesisnd structure as targets for the prevention of calcific aortic valve disease.ardiovasc Res 2007;76(1):19-28, have demonstrated that extracellular ma-

rix synthesis is an important disease phenotype and target for therapeuticnterventions.

ipoproteinsIn the 1990s the uptake of serum neutral lipids and apolipoproteins, and

ipid oxidation around calcium deposits and leukocytes were described inS, resembling the atherosclerotic process.16,17 Mohty et al recently

onducted an important study on severely stenotic valves, explanted atVR,64 supporting the hypothesis that oxLDL also in AS participates in

ecruitment and activation of macrophages, as oxLDL colocated with
acrophages, and an increased oxLDL score correlated with higher tumor

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ecrosis factor-� expression. An increase in oxLDL score also correlatedith increased tissue remodeling score, as defined by Warren and Yong,65

upporting the contribution of oxLDL to calcification in AS, while plasmamall LDL correlated with disease progression and oxLDL score. Theuthors emphasize, however, that 9% of the patients had no oxLDL inheir valves, which might indicate that oxLDL is a contributor but not aequisite for the development of AS.

alini M. Rajamannan: For patients who do not have a genetic abnormality,ost authorities agree that the traditional cardiovascular risk factors are

ritical in the initiation event for this disease. The early histopathologicndings in these patients are critical for the development of animal models,nd future medical therapies. Patients with familial hypercholesterolemia alsoevelop aortic valve disease. Sprecher DL, Schaefer EJ, Kent KM, et al.ardiovascular features of homozygous familial hypercholesterolemia: anal-sis of 16 patients. Am J Cardiol 54(1):20-30, 1984; Rajamannan NM,dwards WD, Spelsberg TC. Hypercholesterolemic aortic-valve disease.Engl J Med 349(7):717-8, 2003.

xidative StressAnalogous to the role of oxidative stress in atherosclerosis, oxidanteneration was confirmed in human AS.66-68 Superoxide and hydrogeneroxide levels were significantly elevated in calcified regions of stenoticalves, but the process might be different from oxidant generation intherosclerosis, namely by reduced expression and activity of antioxidantnzymes and possibly NOS uncoupling instead of NADPH oxidasectivity.66-68 Whether peroxide upregulates Msx2, Wnt/�-catenin, andunx2/cbfa-1 as in vascular osteochondrogenic mineralization,69 needsurther research. We hypothesize that oxidative stress might affectalcification/osteogenesis through different pathways and cell typesuring the evolution of AS, as the dominant cell types may vary atifferent stages of the disease.

alini M. Rajamannan: The authors have clearly defined the differentotential pathways for the development of this disease as described in thisaragraph and also shown in Fig 1.

ineralization and Bone FormationBoth calcific noduli and mature bone formation appear in AS, with

alcific noduli being the first to be described in the era when calcification


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as still considered passive, and later linked to plasma calcium andarathyroid hormone, with and without renal disease.70-72 To date calcificoduli are known to be initiated by macrophage- and obVIC-vesicles, andy apoptosis of aVICs, in response to (inflammatory) chemokines. Boneormation was described later, with presence of obVICs and upregulationf the osteoblast and bone markers osteopontin, bone sialoprotein,steocalcin, alkaline phosphatase, and the osteoblast-specific transcrip-ion factor runx2/cbfa-1.73,74 The pathways modulating osteogenesis inS known to date consist of Lrp-5/Wnt/�-catenin,75 osteoprotegerin/

ankl/RANK,76,77 tenascin-C,78 Toll-like receptors 2 and 4,79,80 andngiotensin II, formed by chymase and cathepsin G from mast cells,81 andy ACE colocalizing with apolipoproteins.82 All pathways are consideredotential new drug targets and subject to research. The exact timing ofnd contribution to calcification and bone formation in vivo needs to beurther mapped.

alini M. Rajamannan: The presence of osteoblastogenesis in the calcifiedortic valve presents the foundation for the future experimental studies in thiseld. Further understanding the timing of the cellular pathways provides theuture direction for the experimental studies in this field.

nflammatory Mechanisms of DegenerationInflammation covers in AS the “cooperation” of endothelium, leuko-

ytes, VICs, oxLDL,83 matrix and neo-angiogenesis as described above.ia a TGF�1-dependent pathway (among others) the endothelium ex-resses adhesion molecules, facilitating uptake of LDL, lymphocytes,onocytes/macrophages, mast cells, and possibly pVICs. oxLDL might

lso in valvular endothelium upregulate caveolin-1 and consequentlyaintain the expression of endothelial adhesion molecules, and activateacrophages. qVICs might transform to aVICs and obVICS in response

o inflammatory chemokines, with TGF� again as main player, and anmerging role for Toll-like receptors. Neoangiogenesis further facilitatesnflammation, serving as highway to the leaflet matrix.84

eneticsLast but not least, all the above-mentioned players in aortic valveathobiology are subject to genetic variations, from which only the top ofhe iceberg is visible to date. Regarding bone metabolism, vitamin D
eceptor polymorphisms and a nonsense mutation with haploinsufficiency

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n Notch 1 have been described. The receptor B allele, leading to reducedalcium absorption, bone loss, and higher parathormone levels, is morerequent among patients with AS, from which we might deduct thatalcium mobilization from bone enhances aortic valve calcification.85

ecause Notch 1 acts, among other functions, as a repressor of Runx2,egulating osteoblast activity, a nonsense mutation might lead to dimin-shed inhibition of calcium deposition.86 The Pvull polymorphism in thestrogen receptor � gene might facilitate aortic stenosis through dyslip-demia.87 Regarding lipid metabolism, only conflicting data about allelicariants of apolipoproteins are published to date,88-90 while the results forenetic variations in inflammation and cell cycle regulatory genes areven more preliminary.91,92 The search for culprit genes should howevere continued, both for early diagnosis in patients with genetic predispo-ition or in siblings in case of familial AS, as for treatment optimizationuided by pharmacogenomics. The need is illustrated by a Finnishecropsy study with microcalcifications in anatomically normal aorticeaflets of young subjects,93 while the Finnish population is known forimited genetic variation, and a French epidemiologic study suggesting anutosomal-dominant inheritance, different from apoE or vitamin Deceptor genes.94

ypothesis on Calcific Aortic Valve StenosisWe hypothesize that all human individuals develop aortic sclerosis to a

ertain (subclinical) degree, due to aging and longstanding mechanicaltress. However, only the patients with the appropriate genetic back-round and/or facilitating factors such as a bicuspid valve, smoking,iabetes, hypertension, dyslipidemia, or renal dysfunction will progress toevere AS within their lifespan, with an as reported variable rate ofrogression.95-97 AS is the common endpoint of diverse pathophysiolog-cal processes, able to develop independently from oxLDL.

hy Did SEAS and SALTIRE Show No Effect onortic Valve Stenosis Progression?With the background provided, several possible reasons can be indi-

ated. At first, the selected patients did not have dyslipidemia asacilitating factor for the progression of AS, so the effect would onlyepend on the pleiotropic effects of statins. Second, only patients with ateast mild stenosis were included. As such the dysfunctional stressistribution and inflammation might already be self-perpetuating and
urpassing the beneficial effect of statins. This hypothesis is supported by

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he recent retrospective study of Antonini-Canterin et al, showing thattatins only reduced progression in aortic sclerosis and mild AS, not inore advanced stages.98 Third, statins do not act on all pathways of AS

athophysiology, which on top do not fully resemble atherosclerosis.ast, but not least, plaque stabilization accounts for most of the beneficialffects of statins in atherosclerosis, but plaque rupture as a cause ofymptoms is not an issue in AS. These trials are very valuable, however.s they emerged from the internationally growing conviction that statins

lone could be capable of slowing the progression of AS, they can nowe seen as the catalysts for further maturation of AS research.

alini M. Rajamannan: LDL-Density-Radius Theory is a recently publishedheory describing trial design for future valvular heart disease. This theoryncorporates the biology and the importance of the hemodynamic measure-

ent for aortic valve disease using the continuity equation. Rajamannan NM.echanisms of aortic valve calcification: the LDL-density-radius theory: a

ranslation from cell signaling to physiology. Am J Physiol Heart Circ Physiol009.

hat Should Be the Next Step?Further characterization of VICs and response to culture conditions isarranted, to optimize in vitro experiments to search for and test newrug targets, and test combinations and optimal timing of establishedrugs (statins, ACE-inhibitors, angiotensin-receptor blockers). In parallelhe search for low cost animal models needs to be continued, at first toompletely characterize the evolution of AS, both by immunohistochem-cs as by in vivo molecular imaging, followed by testing the drugegimens emerging from the in vitro experiments. Meanwhile, the geneticackground influencing the evolution of AS and response to pharmaco-herapy should be further mapped, to direct further human trials. Atresent statins are established players in cardiovascular prevention andhould be administered to AS patients with a current guidelines indica-ion. To date statins cannot be advocated to patients solely to preventrogression of AS. They might prove valuable as part of a drug regimen,s lipids are an important but not the only player in AS, taking intoccount timing and genetic background of the patient.

alini M. Rajamannan: In summary, the authors have summarized the fieldf calcific aortic valve disease from experimental models to clinical trialsxtremely well. This paper demonstrates the potential for future experimental
nd clinical studies in this field. The authors have carefully reviewed the

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ublished data and have defined numerous mechanisms for this disease. Inhe future, medical therapy for calcific aortic valve disease will have manyignaling pathways to target to try and slow progression of this disease.

REFERENCES1. Lindroos M, Kuppari M, Heikkilä J, et al. Prevalence of aortic valve abnormalities

in the elderly: an echocardiographic study of a random population sample. J AmColl Cardiol 1993;21(5):1220-5.

2. Vahanian A, Baumgartner H, Bax J, et al. Guidelines on the management ofvalvular heart disease: the Task Force on the Management of Valvular HeartDisease of the European Society of Cardiology. Eur Heart J 2007;28(2):230-68.

3. Aronow WS, Ahn C, Kronzon I, et al. Association of coronary risk factors and useof statins with progression of mild valvular aortic stenosis in older persons. Am JCardiol 2001;88(6):693-5.

4. Novaro GM, Tiong I, Pearce GL, et al. Effect of hydroxymethylglutaryl coenzymeA reductase inhibitors on the progression of calcific aortic valve stenosis.Circulation 2001;104:2205-9.

5. Bellamy MF, Pellikka PA, Klarich KW, et al. Association of cholesterol levels,hydroxymethylglutaryl coenzyme A reductase inhibitor treatment, and progressionof aortic stenosis in the community. J Am Coll Cardiol 2002;40:1723-30.

6. Shavelle DM, Takasu J, Budoff MJ, et al. HMG CoA reductase inhibitor (statin)and aortic valve calcium. Lancet 2002;359(9312):1125-6.

7. Rosenhek R, Rader F, Loho N, et al. Statins but not angiotensin-converting enzymeinhibitors delay progression of aortic stenosis. Circulation 2004;110:1291-5.

8. Moura LM, Ramos SF, Zamorano JL, et al. Rosuvastatin affecting aortic valveendothelium to slow the progression of aortic stenosis. J Am Coll Cardiol 2007;49:554-61.

9. Pohle K, Mäffert R, Ropers D, et al. Progression of aortic valve calcification.Association with coronary atherosclerosis and cardiovascular risk factors. Circula-tion 2001;104:1927-32.

0. Rossebø AB, Pedersen T, Boman K, et al. Intensive lipid lowering with simvastatinand ezetimibe in aortic stenosis. N Engl J Med 2008;359:1343-56.

1. Cowell SJ, Newby DE, Prescott RJ, et al. A randomized trial of intensivelipid-lowering therapy in calcific aortic stenosis. N Engl J Med 2005;352:2389-97.

2. Lindroos M, Kupari M, Valvanne J, et al. Factors associated with calcific aorticvalve degeneration in the elderly. Eur Heart J 1994;15(7):865-70.

3. Stewart BF, Siscovick D, Lind BK, et al. Clinical factors associated with calcificaortic valve disease. Cardiovascular health study. J Am Coll Cardiol 1997;29:630-4.

4. Iung B, Baron G, Butchart EG, et al. A prospective survey of patients with valvularheart disease in Europe: the Euro heart survey on valvular heart disease. Eur Heart J2003;24:1231-43.

5. Olsson M, Dalsgaard CJ, Haegerstrand A, et al. Accumulation of T-lymphocytesand expression of interleukin-2 receptors in nonrheumatic stenotic aortic valves.
J Am Coll Cardiol 1994;23(5):1162-70.

1

1

1

1

2

2

2

2

2

2

2

2

2

2

3

3

3

3

3

3

6. Otto CM, Kuusisto J, Reichenbach DD, et al. Characterization of the early lesionof degenerative valvular aortic stenosis. Histological and immunohistochemicalstudies. Circulation 1994;90:844-53.

7. O’Brien KD, Reichenbach DD, Marcinova SM, et al. Apolipoproteins B, (a), andE accumulate in the morphologically early lesion of degenerative valvular aorticstenosis. Arterioscler Thromb Vasc Biol 1996;16:523-32.

8. Rajamannan NM, Subramaniam M, Springett M, et al. Atorvastatin inhibitshypercholesterolemia-induced cellular proliferation and bone matrix production inthe rabbit aortic valve. Circulation 2002;105:2660-5.

9. Simmons CA, Grant GR, Manduchi E, et al. Spatial heterogeneity of endothelialphenotypes correlates with site-specific vulnerability to calcification in normalporcine aortic valves. Circ Res 2005;96:792-9.

0. Vasile E, Antohe F. An ultrastructural study of beta very low density lipoproteinuptake and transport by valvular endothelium of hyperlipidemic rabbits. J Submi-crosc Cytol Pathol 1991;23:279-87.

1. Nievelstein-Post P, Mottino G, Fogelman A, et al. An ultrastructural study oflipoprotein accumulation in cardiac valves of the rabbit. Arterioscler Thromb1994;14:1151-61.

2. Rajamannan NM, Sangiorgi G, Springett M, et al. Experimental hypercholesterol-emia induces apoptosis in the aortic valve. J Heart Valve Dis 2001;10:371-4.

3. Drolet MC, Arsenault M, Couet J. Experimental aortic valve stenosis in rabbits.J Am Coll Cardiol 2003;41:1211-7.

4. Cimini M, Boughner DR, Ronald JA, et al. Development of aortic valve stenosis ina rabbit model of atherosclerosis: an immunohistochemical and histological study.J Heart Valve Dis 2005;14:365-75.

5. Zeng Z, Nievelstein-Post P, Yin Y, et al. Macromolecular transport in heart valvesIII: experiment and theory for the size distribution of extracellular liposomes inhyperlipidemic rabbits. Am J Physiol Heart Circ Physiol 2007;292:H2687-97.

6. Luo G, Ducy P, McKee MD, et al. Spontaneous calcification of arteries andcartilage in mice lacking matrix gla protein. Nature 1997;386:78-81.

7. Galvin KM, Donovan MJ, Lynch CA, et al. A role for SmadVI in development andhomeostasis of the cardiovascular system. Nat Genet 2000;24:171-4.

8. Lee TC, Zhao YD, Courtman DW, et al. Abnormal aortic development in micelacking endothelial nitric oxide synthase. Circulation 2000;101:2345-8.

9. Tanaka K, Sata M, Fukuda D, et al. Age-associated aortic stenosis in apolipoproteinE-deficient mice. J Am Coll Cardiol 2005;46:134-41.

0. Garg V, Muth AN, Ransom JF, et al. Mutations in NOTCH 1 cause aortic valvedisease. Nature 2005;437:270-4.

1. Drolet MC, Roussel E, Deshaies Y, et al. A high fat/high carbohydrate diet inducesaortic valve disease in C57BL/6J mice. J Am Coll Cardiol 2006;47:850-5.

2. Weiss RM, Ohashi M, Miller JD, et al. Dl. Calcific aortic valve stenosis in oldhypercholesterolemic mice. Circulation 2006;114:2065-9.

3. Aikawa E, Nahrendorf M, Sosnovik D, et al. Multimodality molecular imagingidentifies proteolytic and osteogenic activities in early aortic valve disease. Circulation2007;115:377-86.

4. Davignon J. Beneficial cardiovascular pleitropic effects of statins. Circulation
2004;109(suppl III):III-39-III-43.

3

3

3

3

3

4

4

4

4

4

4

4

4

4

4

5

5

5

C

5. Soini Y, Salo T, Satta J. Angiogenesis is involved in the pathogenesis ofnonrheumatic aortic valve stenosis. Hum Pathol 2003;34(8):756-63.

6. Rajamannan NM, Subramaniam M, Rickard D, et al. Human aortic valvecalcification is associated with an osteoblast phenotype. Circulation 2003;107:2181-4.

7. Roberts WC, Ko JM. Frequency by decades of unicuspid, bicuspid and tricuspidaortic valves in adults having isolated aortic valve replacement for aortic stenosis,with or without associated regurgitation. Circulation 2005;111:920-5.

8. Thubrikar MJ, Aouad J, Nolan SP. Patterns of calcific deposits in operativelyexcised stenotic or purely regurgitant aortic valves and their relation to mechanicalstress. Am J Cardiol 1986;58(3):304-8.

9. Nicosia MA, Cochran RP, Reichenbach DR, et al. A coupled fluid-structurefinite-element model of the aortic valve and root. J Heart Valve Dis 2003;12:781-9.

0. Davignon J, Ganz, P. Role of endothelial dysfunction in atherosclerosis. Circulation2004;109(suppl lIII):III-27-III-32.

1. Tiwari RL, Singh V, Barthwal MK. Macrophages: an elusive yet emergingtherapeutic target of atherosclerosis. Med Res Rev 2008;28(4):483-544.

2. Robicsek F, Thubrikar MJ, Fokin AA. Cause of degenerative disease of thetrileaflet valve: review of the subject and presentation of a new theory. Ann ThoracSurg 2002;73:1346-54.

3. Singh R, Strom JA, Ondrovic L, et al. Age-related changes in the aortic valve affectleaflet stress distributions: implications for aortic valve degeneration. J Heart ValveDis 2008;17(3):290-8.

4. Sacks MS, Yoganathan AP. Heart valve function: a biomechanical perspective.Philos Trans R Soc Lond 2007;362:1369-91.

5. Balachandran K, Sucosky P, Jo H, et al. Elevated cyclic stretch alters matrixremodelling in aortic valve cusps: implications for degenerative aortic valvedisease. Am J Physiol Heart Circ Physiol 2009;296:H756-764.

6. Merryman WD, Lukoff HD, Long RA, et al. Synergistic effects of cyclic tensionand transforming growth factor -�1 on the aortic valve myofibroblast. CardiovascPathol 2007;16:268-76.

7. Sucosky P, Balachandran K, Elhammaly A, et al. Altered shear stress stimulatesupregulation of endothelial VCAM-1 and ICAM-1 in a BMP-4- and TGF�1-dependent pathway. Arterioscler Thromb Vasc Biol 2009;29:254-60.

8. El-Hamamsy I, Balachandran K, Yacoub MH, et al. Endothelium-dependentregulation of the mechanical properties of aortic valve cusps. J Am Coll Cardiol2009;53:1448-55.

9. Butcher JT, Penrod AM, Garcia AJ, et al. Unique morphology and focal adhesiondevelopment of valvular endothelial cells in static and fluid flow environments.Arterioscler Thromb Vasc Biol 2004;24:1429-34.

0. Butcher JT, Tressel S, Johnson T, et al. Transcriptional profiles of valvular andvascular endothelial cells reveal phenotypic differences. Influence of shear stress.Arterioscler Thromb Vasc Biol 2006;26:69-77.

1. Liu AC, Joag VR, Gotlieb AI. The emerging role of valve interstitial cellphenotypes in regulating heart valve pathobiology. Am J Pathol 2007;171:1407-18.

2. Paranya G, Vineberg S, Dvorin E, et al. Aortic valve endothelial cells undergotransforming-growth-factor-�-mediated and non-transforming-growth-factor-
�-mediated transdifferentiation in vitro. Am J Pathol 2001;159:1335-43.

5

5

5

5

5

5

5

6

6

6

6

6

6

6

6

6

6

3

3. Paruchuri S, Yang JH, Aikawa E, et al. Human pulmonary valve progenitor cellsexhibit endothelial/mesenchymal plasticity in response to vascular endothelialgrowth factor-A and transforming-growth-factor-�2. Circ Res 2006;99:861-9.

4. Yip CYY, Chen JH, Zhao R, et al. Calcification by valve interstitial cells isregulated by the stiffness of the extracellular matrix. Arterioscler Thromb Vasc Biol2009;29:936.

5. Monzack EL, Gu X, Masters KS. Efficacy of simvastatin treatment of valvularinterstitial cells varies with the extracellular environment. Arterioscler ThrombVasc Biol 2009;29:246-53.

6. Wu B, Elmariah S, Kaplan FS, et al. Paradoxical effects of statins on aortic valvemyofibroblasts and osteoblasts. Implications for end-stage valvular heart disease.Arterioscler Thromb Vasc Biol 2005;25:592-7.

7. Anger T, El-Chafchak J, Habib A, et al. Statins stimulate RGS-regulated ERK ½activation in human calcified and stenotic aortic valves. Exp Mol Pathol 2008;85:101-11.

8. Edep ME, Shirani J, Wolf P, et al. Matrix metalloproteinase expression innonrheumatic aortic stenosis. Cardiovasc Pathol 2000;9:281-6.

9. Fondard O, Detaint D, Iung B, et al. Extracellular matrix remodeling in humanaortic valve disease: the role of matrix metalloproteinases and their tissueinhibitors. Eur Heart J 2005;26:1333-41.

0. Satta J, Oiva J, Salo T, et al. Evidence for an altered balance between matrix-metalloproteinase-9 and its inhibitors in calcific aortic stenosis. Ann Thorac Surg2003;76:681-8.

1. Helske S, Syvaranta S, Lindstedt KA, et al. Increased expression of elasolyticcathepsins S, K, V and their inhibitor cystatin C in stenotic aortic valves.Arterioscler Thromb Vasc Biol 2006;26:1791-8.

2. Helske S, Syvaranta S, Kupari M, et al. Possible role for mast cell-derivedcathepsin G in the adverse remodeling of aortic valves. Eur Heart J 2006;27:1495-504.

3. Kaden JJ, Dempfle CE, Grobholz R, et al. Inflammatory regulation of extracellularmatrix remodeling in calcific aortic valve stenosis. Cardiovasc Pathol 2005;14:80-7.

4. Mohty D, Pibarot P, Després JP, et al. Association between plasma LDL particlesize, valvular accumulation of oxidized LDL, and inflammation in patients withaortic stenosis. Arterioscler Thromb Vasc Biol 2008;28:187-93.

5. Warren BA, Yong JL. Calcification of the aortic valve: its progression and grading.Pathology 1997;29(4):360-8.

6. Chen K, Thomas SR, Keaney JF Jr, et al. Oxidation: ROS in vascular signaltransduction. Free Radic Biol Med 2003;35:117-32.

7. Miller JD, Chu Y, Brooks RM, et al. Dysregulation of antioxidant mechanismscontributes to increased oxidative stress in calcific aortic valvular stenosis inhumans. J Am Coll Cardiol 2008;52:843-50.

8. Liberman M, Bassi E, Martinatti MK, et al. Oxidant generation predominatesaround calcifying foci and enhances progression of aortic valve calcification.Arterioscler Thromb Vasc Biol 2008;28:463-70.

9. Towler DA. Oxidation, inflammation, and aortic valve calcification. J Am Coll
Cardiol 2008;52:851-4.

7

7

7

7

7

7

7

7

7

7

8

8

8

8

8

8

8

C

0. Maher ER, Young G, Smyth-Walsh B, et al. Aortic and mitral valve calcificationin patients with end-stage renal disease. Lancet 1987;2(8564):875-7.

1. Ortlepp JR, Pillich M, Schmitz F, et al. Lower serum calcium levels areassociated with greater calcium hydroxyapatite deposition in native aorticvalves of male patients with severe calcific aortic stenosis. J Heart Valve Dis2006;15(4):502-8.

2. Linhartova K, Veselka J, Sterbakova G, et al. Parathyroid hormone and vitamin Dlevels are independently associated with calcific aortic stenosis. Circ J 2008;72:245-50.

3. O’Brien KD, Kuusisto J, Reichenbach DD, et al. Osteopontin is expressed inhuman aortic valvular lesions. Circulation 1995;92:2163-8.

4. Mohler ER III, Gannon F, Reynolds C, et al. Bone formation and inflammation incardiac valves. Circulation 2001;103:1522-8.

5. Caira FC, Stock SR, Gleason TG, et al. Human degenerative valve disease isassociated with up-regulation of low-density lipoprotein receptor-related protein-5receptor-mediated bone formation. J Am Coll Cardiol 2006;47:1707-12.

6. Kaden JJ, Bickelhaupt S, Grobholz R, et al. Receptor activator of nuclear factor kBligand and osteoprotegerin regulate aortic valve calcification. J Mol Cell Cardiol2004;36:57-66.

7. Steinmetz M, Skowasch D, Wernert N, et al. Differential profile of the OPG/RANKL/RANK system in degenerative aortic native and bioprosthetic valves.J Heart Valve Dis 2008;17(2):187-93.

8. Satta J, Melkko J, Pöllänen R, et al. Progression of human aortic valve stenosis isassociated with tenascin-C expression. J Am Coll Cardiol 2002;39:96-101.

9. Meng X, Ao L, Song Y, et al. Expression of functional toll-like receptors 2 and 4in human aortic valve interstitial cells: potential roles in aortic valve inflammationand stenosis. Am J Physiol Cell Physiol 2008;294:C29-35.

0. Yang X, Fullerton DA, Su X, et al. Pro-osteogenic phenotype of human aortic valveinterstitial cells is associated with higher levels of toll-like receptors 2 and 4 andenhanced expression of bone morphogenic protein 2. J Am Coll Cardiol 2009;53(6):491-500.

1. Helske S, Lindstedt KA, Laine M, et al. Induction of local angiotensin II producingsystems in stenotic aortic valves. J Am Coll Cardiol 2004;44:1859-66.

2. O’Brien KD, Shavelle DM, Caulfield MT, et al. Association of angiotensin-converting enzyme with low-density lipoprotein in aortic valvular lesions and inhuman plasma. Circulation 2002;106:2224-30.

3. Holvoet P, De Keyzer D, Jacobs DR, et al. And the metabolic syndrome. FuturesLipidol 2008;3(6):637-49.

4. Mazzone A, Epistolato MC, De Caterina R, et al. Neoangiogenesis, T-lymphocyteinfiltration, and heat shock protein- 60 are biological hallmarks of an immunome-diated inflammatory process in end-stage calcified aortic valve stenosis. J Am CollCardiol 2004;43:1670-6.

5. Ortlepp JR, Hoffmann R, Ohme F, et al. The vitamin D receptor genotypepredisposes to the development of calcific aortic valve stenosis. Heart 2001;85:635-8.

6. Garg V, Muth AN, Ransom JF, et al. Mutations in Notch 1 cause aortic valve
disease. Nature 2005;437:270-4.

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8

8

9

9

9

9

9

9

9

9

9

3

7. Nordström P, Glader CA, Dahlen G, et al. Oestrogen receptor alpha genepolymorphism is related to aortic valve sclerosis in postmenopausal women.J Intern Med 2003;254:140-6.

8. Novaro GM, Sachar R, Pearce GL, et al. Association between apolipoprotein Ealleles and calcific valvular heart disease. Circulation 2003;108:1804-8.

9. Avakian SD, Annicchino-Bizzacchi JM, Grinberg M, et al. Apolipoproteins AI, B,and E polymorphisms in severe aortic valve stenosis. Clin Genet 2001;60:381-4.

0. Ortlepp JR, Pillich M, Mevissen V, et al. ApoE alleles are not associated withcalcific aortic stenosis. Heart 2006;92:1463-6.

1. Ortlepp JR, Schmitz F, Mevissen V, et al. The amount of calcium-deficienthexagonal hydroxyapatite in aortic valves is influenced by gender and associatedwith genetic polymorphisms in patients with severe calcific aortic stenosis. EurHeart J 2004;25:514-22.

2. Golubnitschaja O, Yeghiazaryan K, Skowasch D, et al. P21WAF1/CIP1 and 14-3-3sigma gene expression in degenerated aortic valves: a link between cell cyclecheckpoints and calcification. Amino Acids 2006;31:309-16.

3. Kuusisto J, Räsänen K, Särkioja T, et al. Atherosclerosis-like lesions of the aorticvalve are common in adults of all ages: a necropsy study. Heart 2005;91:576-82.

4. Probst V, Le Scouarnec S, Legendre A, et al. Familial aggregation of calcific aorticvalve stenosis in the western part of France. Circulation 2006;113:856-60.

5. Roger VL, Tajik AJ, Bailey, KR, et al. Progression of aortic stenosis in adults: newappraisal using Doppler echocardiography. Am Heart J 1990;119:331-8.

6. Rosenhek R, Klaar U, Schemper M, et al. Mild and moderate aortic stenosis.Natural history and risk stratification by echocardiography. Eur Heart J 2004;25:199-205.

7. Briand M, Lemieux I, Dumesnil JG, et al. Metabolic syndrome negativelyinfluences disease progression and prognosis in aortic stenosis. J Am Coll Cardiol2006;47:2229-36.

8. Antonini-Canterin F, Hirsu M, Popescu BA, et al. Stage-related effect of statintreatment on the progression of aortic valve sclerosis and stenosis. Am J Cardiol2008;102:738-42.


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