Aortic valve disease is among the third most common cardiovascular disease worldwide, and is also a strong predictor for other cardiac related deaths. Altered mechanical forces are believed to cause changes in aortic valve biosynthetic activity, eventually leading to valve disease, however little is known about the cellular and molecular events involved in these processes. To gain a fundamental understanding into aortic valve disease mechanobiology, an ex vivo experimental model was used to study the effects of normal and elevated cyclic stretch on aortic valve remodeling and degenerative disease. The hypothesis of this proposal was that elevated cyclic stretch will result in increased expression of markers related to degenerative valve disease. Three aspects of aortic valve disease were studied: (i) Altered extracellular matrix remodeling; (ii) Aortic Valve Calcification; and (iii) Serotonin-induced valvulopathy. Results showed that elevated stretch resulted in increased matrix remodeling and calcification via a bone morphogenic protein-dependent pathway. In addition, elevated stretch and serotonin resulted in increased collagen biosynthesis and tissue stiffness via a serotonin-2A receptor-mediated pathway. This work adds to current knowledge on aortic valve disease mechanisms, and could pave the way for the development of novel treatments for valve disease and for the design of tissue engineered valve constructs.

Aortic stenosis is a life-threatening valvular heart disease. At the onset of symptoms, a patient’s prognosis becomes poor and the risk of death rapidly increases. Aortic valve replacement surgery remains the gold standard in treatment for aortic stenosis. However, in the total population of patients with severe aortic stenosis, about one third are deemed inoperable due to their high surgical risk. In recent years, the development of transcatheter aortic valve implantation (TAVI), a non-invasive heart valve replacement procedure brought hope for the elderly, high-risk and inoperable aortic stenosis patient population pool. A literature review was performed to examine the safety, efficacy and effectiveness evidence for transcatheter aortic valve treatment option. The results showed that TAVI is a safe treatment option, however the effectiveness for the whole patient population is unknown. The adoption of this alternative treatment option is certainly coupled with multiple dimension of impact from a public health perspective. It remains inconclusive whether TAVI is an effective treatment option to be adopted. / published_or_final_version / Public Health / Master / Master of Public Health

Various surgical options exist to correct pathologies of the aortic valve, including mechanical or biological valve implantation, reconstruction of the native vessels, and a combination of the two. Additionally, finite-element analysis and, to some extent, fluid-structure interaction (FSI) analyses have been used in the past to analyze how these procedures may affect various engineering metrics such as tissue stresses and opening and closing dynamics of the valves. In this work, a similar type of model and analysis is performed, however, in addition to modeling the actions of the aortic valve, coronary flows are also considered. By incorporating these vessels, it is possible to examine coronary flow perturbations to mechanical and geometric model variations and to assess certain surgical procedures in regards to a new clinically relevant metric.

Experiments described in this thesis address the pathogenesis of aortic valve sclerosis/stenosis using a bench to bedside approach. In particular, the thesis begins with development of a technique using ultrasonic backscatter analyses to quantitate the early stages of aortic stenosis. Subsequent chapters utilized this methodology to quantitate aortic valve structural changes in a model and intervention study of aortic stenosis in rabbits. The last chapters are human studies designed to identify factors associated with presence of aortic sclerosis/stenosis; with particular interest in potential association of endothelial dysfunction/inflammation/platelet aggregation with abnormal aortic valve structure quantitated by ultrasonic backscatter. In Chapter 1 (Introduction) the relevant literature is reviewed. Development of ultrasonic backscatter to quantitate aortic sclerosis (Chapter 2) Aortic valve sclerosis (ASc) is detected when there is visual assessment of focal increases in echogenicity of the aortic valve most commonly assessed by echocardiography. However, there is no previously described method to quantitate degree of aortic valve structural abnormality as ASc is not associated with marked hemodynamic obstruction quantifiable by Doppler echocardiography. The current study used ultrasonic backscatter to quantitate aortic valve structural abnormality in patients assessed as having ASc based on valve appearances, compared to young healthy volunteers with normal aortic valves. The results of the study indicate: 1) that the mean levels of aortic valve backscatter in ASc patients are approximately 60% greater than in young healthy volunteers (ie aortic valve backscatter scores ≥ 16dB are not consistent with normal aortic valve structure), 2) ultrasonic backscatter scores in ASc patients are directly correlated with subjective scoring of sclerosis and with a positive trend with transvalvular pressure gradients in patients with mild-moderate aortic stenosis, and most importantly, 3) ultrasonic backscatter is a reproducible technique, with mean differences between estimates based on repeat echocardiograms of 2.3 ± 1.7 (9.1%). These results indicate that ultrasonic backscatter could be used as a quantitative measure of aortic valve structural abnormality in epidemiology and for examination of interventions. In vivo studies Development of an animal model of aortic stenosis with vitamin D2 (Chapter 3) The aim of the study was to develop an appropriate animal model for AS. The study used vitamin D2 alone at 25,000IU/4 days weekly (vit-D2) for 8 weeks to induce AS in rabbits. Results showed that: 1) rabbits in the vit-D2 group had significantly increased in transvalvular velocity and pressure gradients compared to rabbits in the control group (normal chow + drinking water); this was consistent for aortic valve ultrasonic backscatter scores; 2) aortic valve immunohistochemistry/histology showed marked calcification, neutral lipids, macrophage, and leukocyte infiltrations for rabbits in the vit- D2 group (ie consistent with histology of human AS); 3) significant elevation of asymmetric dimethylarginine (ADMA) concentrations in the vit-D2 group occurred compared to controls over the 8 weeks treatment period; the change in ADMA concentrations correlated significantly with the change in transvalvular pressure gradients for rabbits in the vit-D2 group; 4) rabbits in the vit-D2 group had significantly impaired endothelium-dependent acetylcholine-induced aortic relaxation, and this effect was completely abolished by the nitric oxide synthase inhibitor (L-NAME); 5) the addition of 0.5% cholesterol-supplemented diet to the vitamin D2 regimen did not accentuate the development of AS. Thus, treatment with vitamin D2 at 25,000IU/4 days weekly for 8 weeks significantly induced AS with similar aortic valve pathology to that of human AS; therefore, the model is suitable for use in examining potential therapeutic interventions in AS. Effects of ramipril on development of AS in rabbits (Chapter 4) Using this animal model, this study aimed to examine the effects of the angiotensinconverting enzyme inhibitor (ACEi) ramipril on development of AS. Rabbits (n=28) treated for 8 weeks were divided into 2 groups: (a) vitamin D2 alone (n=10) (normal chow + 25,000IU vitamin D2 in drinking water); (b) vitamin D2/Ramipril (n=12) (normal chow+25,000IU vitamin D2/Ramipril (0.5mg/kg) in drinking water). Six further rabbits constituted a normal reference group (no treatment was given). The results for comparisons between vitamin D2/ramipril vs vitamin D2 alone were as follows: 1) ramipril-treated rabbits had significantly less severe hemodynamic obstructions (p<0.05, for both) as assessed by transvalvular velocity, and aortic valve area; with borderline reduction in aortic valve backscatter (p=0.08); 2) ramipril significantly reduced plasma ADMA concentrations; 3) there was improvement in acetylcholine-induced aortic relaxation (p=0.056), with significant improvement in sodium nitroprusside-induced relaxation (p<0.05); 4) there was a strong inverse correlation between acetylcholineinduced aortic relaxation and aortic valve backscatter score (0<0.001), thus providing further evidence of the potential role of nitric oxide in retarding the development of AS in this model. These data provide a strong rationale for the inception of a randomized trial of ACE inhibition as a strategy for limitation of AS progression in humans. Human studies Aortic stenosis is associated with elevated plasma levels of asymmetric dimethylarginine (ADMA) concentrations in humans (Chapter 5). Given the findings that aortic stenosis induced by vitamin D2 in rabbits also caused elevation of plasma ADMA concentrations, a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk. The study sought to determine whether plasma ADMA concentrations are elevated independently of pre-existing coronary risk factors in subjects with at least moderate aortic stenosis (n=42) compared to age-matched patients with normal aortic valves (n=42): as determined both by visual assessment and with aortic valve backscatter scores < 16dB. Results for this study were as follows: 1) plasma ADMA concentrations were not statistically different between the AS and non-AS group (median 0.59 vs 0.54 µmol/L, p=0.13, Mann-Whitney test) on univariate analysis; 2) backward stepwise multiple linear regression showed the presence of AS was a significant predictor of elevated ADMA concentrations (p=0.04, 95% CI =0.001, 0.072). 3) in addition, elevated plasma ADMA concentrations were also associated with history of atrial fibrillation (p=0.009, 95% CI=0.015, 0.100), and negatively associated with creatinine clearance (p=0.01, 95% CI=-0.002, 0.000), and the use of statin therapy (p=0.01, 95% CI=-0.081, -0.011). Therefore, in conclusion, this study found that AS is independently associated with elevation of ADMA concentrations, beyond that implied by “conventional” risk factors for endothelial dysfunction. The clinical status of AS as an incremental marker of cardiovascular risk may reflect ADMA-mediated endothelial dysfunction. Assessment of factors associated with ASc in a random ageing population study (Chapter 6). There have been few clinical studies of factors associated with ASc. Previous population studies have established that ASc is an independent correlate of incremental risk of coronary events. Having established that patients with AS have increased plasma ADMA concentrations (Chapter 5), it was now aimed to determine whether subjects with increased aortic valve backscatter scores (ASc) also have other markers of endothelial dysfunction/NO effects, independent of preexisting coronary risk factors. The study was designed to identify such anomalies, if they existed, on an incremental basis to other putative correlates of ASc, including coronary risk factors, renal dysfunction and vitamin D levels. Random selected subjects (n=253) aged between 51 to 77 years were evaluated. All patients underwent transthoracic echocardiography examination; aortic valve ultrasonic backscatter score (AVBS), was used to quantitate echogenicity of the aortic valve. Conventional coronary risk factors were identified on history. Integrity of NO generation/response was assessed via (i) plasma ADMA concentrations; (ii) inhibition of platelet aggregation by the NO donor sodium nitroprusside (SNP); (iii) aortic augmentation index (AIx), a measure of arterial stiffness/wave reflection. All putative correlations with AVBS were examined by univariate and stepwise multiple linear regression analyses. On the basis of echocardiographic appearances, ASc was present in 63 subjects (25.4%); mean AVBS scores was 14.9±4.6dB (SD) vs 11.2±3.9dB (SD) in the presence vs absence of ASc (p<0.001). Univariate analyses revealed that platelet responsiveness to NO was inversely correlated with AVBS (β=-0.16, p=0.02); but [ADMA] and AIx were not. On multiple linear regression, significant correlates of increased AVBS were: (i) advanced age (β=0.21, p=0.003), (ii) low body mass index (β=-0.23, p=0.001); and (iii) impaired platelet responsiveness to NO (β=-0.16, p=0.02). In Chapter 7, the implications of the overall findings in this thesis are discussed in relation to future perspective. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1309350 / Thesis(Ph.D.) -- School of Medicine, 2008

Experiments described in this thesis address the pathogenesis of aortic valve sclerosis/stenosis using a bench to bedside approach. In particular, the thesis begins with development of a technique using ultrasonic backscatter analyses to quantitate the early stages of aortic stenosis. Subsequent chapters utilized this methodology to quantitate aortic valve structural changes in a model and intervention study of aortic stenosis in rabbits. The last chapters are human studies designed to identify factors associated with presence of aortic sclerosis/stenosis; with particular interest in potential association of endothelial dysfunction/inflammation/platelet aggregation with abnormal aortic valve structure quantitated by ultrasonic backscatter. In Chapter 1 (Introduction) the relevant literature is reviewed. Development of ultrasonic backscatter to quantitate aortic sclerosis (Chapter 2) Aortic valve sclerosis (ASc) is detected when there is visual assessment of focal increases in echogenicity of the aortic valve most commonly assessed by echocardiography. However, there is no previously described method to quantitate degree of aortic valve structural abnormality as ASc is not associated with marked hemodynamic obstruction quantifiable by Doppler echocardiography. The current study used ultrasonic backscatter to quantitate aortic valve structural abnormality in patients assessed as having ASc based on valve appearances, compared to young healthy volunteers with normal aortic valves. The results of the study indicate: 1) that the mean levels of aortic valve backscatter in ASc patients are approximately 60% greater than in young healthy volunteers (ie aortic valve backscatter scores ≥ 16dB are not consistent with normal aortic valve structure), 2) ultrasonic backscatter scores in ASc patients are directly correlated with subjective scoring of sclerosis and with a positive trend with transvalvular pressure gradients in patients with mild-moderate aortic stenosis, and most importantly, 3) ultrasonic backscatter is a reproducible technique, with mean differences between estimates based on repeat echocardiograms of 2.3 ± 1.7 (9.1%). These results indicate that ultrasonic backscatter could be used as a quantitative measure of aortic valve structural abnormality in epidemiology and for examination of interventions. In vivo studies Development of an animal model of aortic stenosis with vitamin D2 (Chapter 3) The aim of the study was to develop an appropriate animal model for AS. The study used vitamin D2 alone at 25,000IU/4 days weekly (vit-D2) for 8 weeks to induce AS in rabbits. Results showed that: 1) rabbits in the vit-D2 group had significantly increased in transvalvular velocity and pressure gradients compared to rabbits in the control group (normal chow + drinking water); this was consistent for aortic valve ultrasonic backscatter scores; 2) aortic valve immunohistochemistry/histology showed marked calcification, neutral lipids, macrophage, and leukocyte infiltrations for rabbits in the vit- D2 group (ie consistent with histology of human AS); 3) significant elevation of asymmetric dimethylarginine (ADMA) concentrations in the vit-D2 group occurred compared to controls over the 8 weeks treatment period; the change in ADMA concentrations correlated significantly with the change in transvalvular pressure gradients for rabbits in the vit-D2 group; 4) rabbits in the vit-D2 group had significantly impaired endothelium-dependent acetylcholine-induced aortic relaxation, and this effect was completely abolished by the nitric oxide synthase inhibitor (L-NAME); 5) the addition of 0.5% cholesterol-supplemented diet to the vitamin D2 regimen did not accentuate the development of AS. Thus, treatment with vitamin D2 at 25,000IU/4 days weekly for 8 weeks significantly induced AS with similar aortic valve pathology to that of human AS; therefore, the model is suitable for use in examining potential therapeutic interventions in AS. Effects of ramipril on development of AS in rabbits (Chapter 4) Using this animal model, this study aimed to examine the effects of the angiotensinconverting enzyme inhibitor (ACEi) ramipril on development of AS. Rabbits (n=28) treated for 8 weeks were divided into 2 groups: (a) vitamin D2 alone (n=10) (normal chow + 25,000IU vitamin D2 in drinking water); (b) vitamin D2/Ramipril (n=12) (normal chow+25,000IU vitamin D2/Ramipril (0.5mg/kg) in drinking water). Six further rabbits constituted a normal reference group (no treatment was given). The results for comparisons between vitamin D2/ramipril vs vitamin D2 alone were as follows: 1) ramipril-treated rabbits had significantly less severe hemodynamic obstructions (p<0.05, for both) as assessed by transvalvular velocity, and aortic valve area; with borderline reduction in aortic valve backscatter (p=0.08); 2) ramipril significantly reduced plasma ADMA concentrations; 3) there was improvement in acetylcholine-induced aortic relaxation (p=0.056), with significant improvement in sodium nitroprusside-induced relaxation (p<0.05); 4) there was a strong inverse correlation between acetylcholineinduced aortic relaxation and aortic valve backscatter score (0<0.001), thus providing further evidence of the potential role of nitric oxide in retarding the development of AS in this model. These data provide a strong rationale for the inception of a randomized trial of ACE inhibition as a strategy for limitation of AS progression in humans. Human studies Aortic stenosis is associated with elevated plasma levels of asymmetric dimethylarginine (ADMA) concentrations in humans (Chapter 5). Given the findings that aortic stenosis induced by vitamin D2 in rabbits also caused elevation of plasma ADMA concentrations, a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk. The study sought to determine whether plasma ADMA concentrations are elevated independently of pre-existing coronary risk factors in subjects with at least moderate aortic stenosis (n=42) compared to age-matched patients with normal aortic valves (n=42): as determined both by visual assessment and with aortic valve backscatter scores < 16dB. Results for this study were as follows: 1) plasma ADMA concentrations were not statistically different between the AS and non-AS group (median 0.59 vs 0.54 µmol/L, p=0.13, Mann-Whitney test) on univariate analysis; 2) backward stepwise multiple linear regression showed the presence of AS was a significant predictor of elevated ADMA concentrations (p=0.04, 95% CI =0.001, 0.072). 3) in addition, elevated plasma ADMA concentrations were also associated with history of atrial fibrillation (p=0.009, 95% CI=0.015, 0.100), and negatively associated with creatinine clearance (p=0.01, 95% CI=-0.002, 0.000), and the use of statin therapy (p=0.01, 95% CI=-0.081, -0.011). Therefore, in conclusion, this study found that AS is independently associated with elevation of ADMA concentrations, beyond that implied by “conventional” risk factors for endothelial dysfunction. The clinical status of AS as an incremental marker of cardiovascular risk may reflect ADMA-mediated endothelial dysfunction. Assessment of factors associated with ASc in a random ageing population study (Chapter 6). There have been few clinical studies of factors associated with ASc. Previous population studies have established that ASc is an independent correlate of incremental risk of coronary events. Having established that patients with AS have increased plasma ADMA concentrations (Chapter 5), it was now aimed to determine whether subjects with increased aortic valve backscatter scores (ASc) also have other markers of endothelial dysfunction/NO effects, independent of preexisting coronary risk factors. The study was designed to identify such anomalies, if they existed, on an incremental basis to other putative correlates of ASc, including coronary risk factors, renal dysfunction and vitamin D levels. Random selected subjects (n=253) aged between 51 to 77 years were evaluated. All patients underwent transthoracic echocardiography examination; aortic valve ultrasonic backscatter score (AVBS), was used to quantitate echogenicity of the aortic valve. Conventional coronary risk factors were identified on history. Integrity of NO generation/response was assessed via (i) plasma ADMA concentrations; (ii) inhibition of platelet aggregation by the NO donor sodium nitroprusside (SNP); (iii) aortic augmentation index (AIx), a measure of arterial stiffness/wave reflection. All putative correlations with AVBS were examined by univariate and stepwise multiple linear regression analyses. On the basis of echocardiographic appearances, ASc was present in 63 subjects (25.4%); mean AVBS scores was 14.9±4.6dB (SD) vs 11.2±3.9dB (SD) in the presence vs absence of ASc (p<0.001). Univariate analyses revealed that platelet responsiveness to NO was inversely correlated with AVBS (β=-0.16, p=0.02); but [ADMA] and AIx were not. On multiple linear regression, significant correlates of increased AVBS were: (i) advanced age (β=0.21, p=0.003), (ii) low body mass index (β=-0.23, p=0.001); and (iii) impaired platelet responsiveness to NO (β=-0.16, p=0.02). In Chapter 7, the implications of the overall findings in this thesis are discussed in relation to future perspective. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1309350 / Thesis(Ph.D.) -- School of Medicine, 2008

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 6 uppsatser.

Η ασβέστωση της αορτικής βαλβίδας σχετίζεται με αυξημένη νοσηρότητα και θνητότητα, ιδιαίτερα στους ηλικιωμένους. Μέχρι σήμερα η φαρμακευτική θεραπεία δεν έχει αποδειχθεί τόσο αποτελεσματική, όσο η χειρουργική. Στην παρούσα εργασία χρησιμοποιήθηκε μοντέλο υπερλιπιδαιμικών κονίκλων προκειμένου να μελετηθεί η επίδραση του εκλεκτικού ανταγωνισμού της αλδοστερόνης στα πρώιμα στάδια της ασβέστωσης της αορτικής βαλβίδας. Αυτή η φαρμακευτική προσέγγιση δεν είχε προηγουμένως διερευνηθεί. Σαράντα αρσενικοί κόνικλοι τύπου Νέας Ζηλανδίας παρέμειναν για 4 εβδομάδες σε κανονική διατροφή και στη συνέχεια χωρίστηκαν σε 3 ομάδες: (1) ομάδα ελέγχου (control) που αποτελούνταν από 10 πειραματόζωα και συνέχισαν να τρέφονται με κανονική διατροφή για 8 εβδομάδες ακόμη, (2) ομάδα vehicle που αποτελούνταν από 15 πειραματόζωα και συνέχισαν να τρέφονται με υπερλιπιδαιμική διατροφή (1% χοληστερόλη) για 8 εβδομάδες ακόμη συν ένα διάλυμα γλυκόζης 5% (vehicle), για τις τελευταίες 4 εβδομάδες και (3) ομάδα επλερενόνης που αποτελούνταν από 15 πειραματόζωα και συνέχισαν να τρέφονται με υπερλιπιδαιμική διατροφή για 8 εβδομάδες ακόμη και τουs χορηγούνταν επλερενόνη 100 mg/kgr/day σε διάλυμα γλυκόζης 5%, για τις τελευταίες 4 εβδομάδες. Πριν από τη θυσία κάθε πειραματοζώου γινόταν μέτρηση της αρτηριακής πίεσης καθώς και των επιπέδων καλίου, ολικής χοληστερόλης και αλδοστερόνης στο πλάσμα. Μετά τις 8 εβδομάδες όλα τα πειραματόζωα θυσιάστηκαν και οι παρασκευασμένες αορτικές βαλβίδες εξετάσθηκαν με χρώση αιματοξυλίνης – ηωσίνης και Von Kossa silver stain και με ανοσοχρώσεις για τους υποδοχείς των αλατοκορτικοειδών (αλδοστερόνης), τα μακροφάγα και το μετατρεπτικό ένζυμο της αγγειοτενσίνης. Η παρουσία εναποθέσεων ασβεστίου επιβεβαιώθηκε με ηλεκτρονικό μικροσκόπιο σάρωσης. Η επλερενόνη αύξησε τα επίπεδα αλδοστερόνης στο πλάσμα, αλλά δεν επηρέασε την αρτηριακή πίεση και τα επίπεδα χοληστερόλης και καλίου. Η υπερλιπιδαιμία προκάλεσε συνάθροιση μακροφάγων και αύξηση της έκφρασης του μετατρεπτικού ενζύμου, όπως επίσης και μικροσκοπική εναπόθεση ασβεστίου στις γλωχίνες. Όλοι αυτοί οι δείκτες ελαττώθηκαν με τη χορήγηση της επλερενόνης. Η ανοσοϊστοχημία για τους υποδοχείς των αλατοκορτικοειδών ανέδειξε παρόμοια έκφραση στις γλωχίνες της ομάδας ελέγχου και της υπερλιπιδαιμικής ομάδας (vehicle). Συμπερασματικά τα αποτελέσματα αυτά δείχνουν πως οι υποδοχείς της αλδοστερόνης εκφράζονται στην αορτική βαλβίδα και πως η εκλεκτική αναστολή τους με τη χορήγηση της επλερενόνης αναστέλλει το σχηματισμό των σκληρυντικών αλλοιώσεων που προκαλούνται από την υπερλιπιδαιμική διατροφή. / Calcific aortic valve disease is associated with increased morbidity and mortality, especially in the elderly. To date, pharmacological therapies have not proven as effective as surgical intervention. Here, we used a hyperlipidemic rabbit model to investigate the potential effects of selective aldosterone inhibition on the early stages of aortic valve calcification, a pharmacological strategy that has not yet been tested. Forty New Zealand male rabbits fed a standard diet for 4 weeks were separated into three groups: (1) control (n = 10), fed a standard diet; (2) vehicle (n = 15), fed a hyperlipidemic diet (cholesterol 1%) plus vehicle; and (3) eplerenone (n = 15), fed a hyperlipidemic diet plus 100 mg/kg/d eplerenone (last 4 weeks). After 8 weeks, animals were sacrificed and prepared aortic valve sections were examined with Von Kossa silver stain and by immunostaining for mineralocorticoid receptor, macrophages and angiotensin-converting enzyme. The presence of calcium deposits was confirmed by scanning electron microscopy. Eplerenone increased aldosterone levels but did not affect blood pressure, cholesterol or potassium levels. Hyperlipidemia induced macrophage accumulation and angiotensin-converting enzyme expression, as well as calcium deposition in the leaflets. All markers were decreased by eplerenone treatment. Immunohistochemistry for mineralocorticoid (aldosterone) receptors revealed similar expression in the leaflets of both control and hyperlipidemic groups. Collectively, these results indicate that aldosterone receptors are present in rabbit aortic valve leaflets and their selective blockade with eplerenone inhibits formation of the sclerotic lesions induced by a high fat diet.

Abstract Aortic valve stenosis (AS) is one of the most diffuse valvular diseases in developed countries. AS is a progressive disease, which usually results in serious life-threatening adverse events. Defining a treatment strategy for AS is a focus of cardiovascular research, although the topic is still controversial because of its related clinical and economical implications. Surgical aortic valve replacement (AVR),which is regarded as the gold standard for the treatment of severe symptomatic AS, affords excellent results, particularly in asymptomatic patients with good functional status. AVR requires the institution of cardiopulmonary bypass and aortic cross-clamping, and the duration of these procedures is directly associated with increasing morbidity and mortality, especially in patients with preoperative comorbidities. Accordingly, techniques aimed at decreasing the duration of cardiopulmonary bypass and aortic cross-clamping have the potential to improve postoperative outcomes of AVR. In the present study, we demonstrated that the Perceval sutureless bioprosthesis could significantly reduce the duration of the surgical procedure. This was associated with improved immediate postoperative outcomes and long-term freedom from adverse events. The use of a Perceval sutureless bioprosthesis can facilitate AVR through minimally invasive approaches and is associated with fewer transfusions of packed red cells compared to full sternotomy approaches, even with traditional stented bioprostheses. It could be expected that patients at intermediate-high risk would benefit more from the combination of a fast surgical procedure, performed with reduced surgical invasiveness. When compared to transcatheter aortic valve implantation (TAVI), the Perceval sutureless bioprosthesis was associated with increased incidence of device success as well as less paravalvular leak, with similar immediate and 1-year outcomes. Finally, AVR with the Perceval sutureless bioprosthesis provided excellent hemodynamics at rest and under high workload. The significant increase of effective orifice area under stress suggests that the Perceval sutureless bioprosthesis is the valve of choice for patients with small aortic annuli or when prosthesis-patient mismatch is anticipated. / Tiivistelmä Aorttaläpän ahtauma on yksi yleisimmistä läppävioista kehittyneissä maissa. Aorttaläpän ahtauma on etenevä sairaus, joka yleensä johtaa vakaviin henkeä uhkaaviin haittatapahtumiin. Aorttaläpän ahtauman hoitotavasta keskustellaan kiivaasti sydän- ja verisuonitautien tutkimuksessa siihen liittyvien kliinisten ja taloudellisten vaikutusten vuoksi. Aorttaläppäleikkausta, jossa aorttaläppä korvataan proteesilla, on aina pidetty vaikean oireisen aorttaläpän ahtauman hoidon kultaisena standardina, koska sen tulokset ovat erinomaisia, etenkin oireettomilla potilailla, joilla sydämen toiminta on hyvä. Leikkaus vaatii sydän-keuhkokoneen käyttöä ja aortan sulkemista, joiden kesto on suoraan yhteydessä kasvavaan sairastavuuteen ja kuolleisuuteen erityisesti potilailla, joilla on muitakin sairauksia. Niinpä tekniikat, jotka lyhentävät sydän-keuhkokoneen käyttöaikaa ja aortan sulkuaikaa, voivat mahdollisesti parantaa aorttaläppäleikkauksen tuloksia. Tässä tutkimuksessa osoitettiin, että ompeleettoman biologisen Perceval-läppäproteesin käyttö vähensi merkittävästi leikkauksen kestoa. Tämä oli yhteydessä parantuneisiin lyhyen ja pitkän aikavälin tuloksiin leikkauksen jälkeen. Ompeleettoman biologisen Perceval-läppäproteesin käyttö voi helpottaa aorttaläppäleikkausta, koska se voidaan asentaa vähemmän kajoavasta avauksesta, ja siihen liittyy vähemmän punasolusiirtoja rintalastan kokoavaukseen verrattuna, myös silloin kun käytetään kokoavausta ja perinteisiä stenttibioproteeseja. Voisi olla odotettavaa, että keskisuuren tai suuren riskin potilaat hyötyisivät enemmän leikkauksesta, jossa yhdistyvät toimenpiteen nopeus ja vähäisempi kajoavuus. Katetriteitse asennettuun biologiseen keinoläppään (TAVI) verrattuna ompeleeton biologinen Perceval-läppäproteesi oli yhteydessä parempaan laitteen toimimiseen ja pienempään paravalvulaariseen vuotoon. Muut tulokset heti leikkauksen jälkeen ja yhden vuoden seurannassa olivat samanlaisia. Lopuksi voidaan todeta, että aorttaläppäleikkaukseen ompeleettomalla biologisella Perceval-läppäproteesilla liittyi erinomainen hemodynamiikka levossa ja korkean työkuorman aikana. Stressin aikaisen tehokkaan aorttaläpän aukon pinta-alan merkittävä kasvu osoittaa, että ompeleeton biologinen Perceval-läppäproteesi on hyvä valinta potilaille, joilla on pieni aorttaläpän aukko tai kun on odotettavissa proteesin ja potilaan yhteensopimattomuutta.

L’anévrisme de l’aorte abdominale (AAA) est associé à des taux élevés de morbidité et de mortalité. A l’heure actuelle, le seul traitement curatif de l’AAA est chirurgical, aucune approche pharmacologique n’ayant démontré une efficacité suffisante. Une meilleure compréhension des mécanismes aboutissant au développement de l’AAA permettrait d’identifier de nouvelles cibles thérapeutiques. Bien qu’utiles dans cette démarche, les modèles animaux expérimentaux actuels ne reproduisent pas parfaitement la physiopathologie humaine. Les objectifs de ce travail étaient de : 1/ Créer et caractériser un nouveau modèle murin d’AAA associant application topique d’élastase et neutralisation du TGFβ. 2/ Etudier le rôle de l’IL1β dans ce modèle. La neutralisation du TGFβ chez des souris C57Bl6j aggravait la dilatation anévrismale induite par l’application d’élastase et favorisait la rupture aortique. Ceci était associé à une dégradation accrue de la matrice-extra-cellulaire, une infiltration de cellules inflammatoires au sein de la paroi aortique, la formation d’un thrombus intra-luminal ainsi qu’une augmentation de la néo-angiogénèse. L’utilisation de la technique d’imagerie par synchrotron a permis de montrer une destruction de la paroi aortique en l’absence de formation de dissection aboutissant à une rupture aortique transmurale fatale. L’expression génique de différentes cytokines, dont l’IL1β était augmentée dans la paroi aortique. Afin d’étudier le rôle de l’IL1β, 2 modèles d’invalidation ont été utilisé : l’induction d’AAA chez des souris déficientes en IL1β et l’injection systémique d’anticorps anti-IL1β. Les souris IL1β-/- étaient protégées du développement anévrismal et de la rupture après application d’élastase et neutralisation du TGFβ. En revanche, la neutralisation de l’IL1β par injection d’anticorps à un temps plus tardif ne limitait pas la progression de l’AAA et aboutissait à la rupture anévrismale. Cette étude a permis de créer un nouveau modèle murin d’AAA dont les caractéristiques sont proches de la physiopathologie humaine. L’invalidation génétique de l’IL1β, et non la neutralisation systémique à un temps tardif, limitait la croissance et prévenait la rupture anévrismale suggérant le rôle de cette cytokine au cours des stades précoces du développement de l’AAA. / Abdominal aortic aneurysm (AAA) is associated with extremely high morbidity and mortality rates. The only curative treatment relies on surgery as no drug has proven yet its efficacy to cure the disease. A better understanding of pathophysiological mechanisms involved in AAA development would help to identify new therapeutic targets. Even though current experimental animal models are useful to address this question, none of them perfectly mimics human disease. The aim of this study was: 1/ Create and characterize a new murine model of AAA based on topic application of elastase associated with systemic TGFβ neutralization. 2/ Study the effect of IL-1β in this model. We report that TGFβ neutralization in C57Bl6j male mice increased aneurysmal aortic dilatation induced by elastase and favored aortic rupture. This was associated with major vascular remodeling including the degradation of extracellular matrix, the infiltration of inflammatory cells in the aortic wall, the formation of an intraluminal thrombus and the increase of neoangiogenesis. Synchrotron-based ultrahigh ex-vivo resolution imaging revealed a wall disruption with no medial dissection culminating in fatal transmural aortic wall rupture. The gene expression of several cytokine including IL-1β was increased in the aortic wall. The effect of IL-1β was investigated using IL-1β-/- mice or using systemic injection of monoclonal anti-IL-1β antibody. IL-1β-/- mice were protected against aortic dilatation and aortic rupture after application of elastase associated with TGFβ neutralization. However, the injection of anti-IL-1β antibody did not limit the aortic dilatation and neither prevented the aortic rupture. In this study, we created a new murine model of AAA which reproduces the main pathophysiological human features. The genetic invalidation of IL-1β, but not its blockade after disease initiation prevented AAA dilatation and rupture, suggesting the role of this cytokine in the early stages of AAA development.

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第13331号 / 論医博第2199号 / 新制||医||1044(附属図書館) / (主査)教授 湊谷 謙司, 教授 横出 正之, 教授 戸口田 淳也 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM