Calcific aortic valve sclerosis is characterized by focal lesions in the valve leaflet. These lesions are rich in myofibroblasts that express α-SMA and cause fibrosis. Lesions tend to occur in regions of the leaflet that are subjected to large bending loads, suggesting a mechanobiological basis for myofibrogenic differentiation and valve pathogenesis. In this thesis, a bioreactor was developed to study the effect of physiological loading on myofibrogenic differentiation of valve interstitial cells. Cyclic loading of native porcine aortic valve leaflets ex vivo resulted in increased α-SMA expression, predominantly in the fibrosa and spongiosa (similar to sclerotic leaflets). Cofilin, an actin-binding protein, was also upregulated by loading, suggesting it plays a role in mechanically-induced myofibrogenesis. Similarly, loading of a tissue engineered aortic valve leaflet model resulted in increased α-SMA transcript and protein expression. These data support an integral role for mechanical stimuli in myofibrogenic differentiation and sclerosis in the aortic valve.

Endothelial cells (ECs) form the inner lining of all blood vessels in the body, and coat the outer surfaces of heart valves. Because ECs are anchored to extracellular matrix proteins and are positioned between flowing blood and underlying interstitium, ECs are constantly exposed to hemodynamic shear, and act as a semi-permeable barrier to blood-borne factors. In vitro cell culture flow (ICF) systems have been employed as laboratory tools for testing endothelial properties such as adhesion strength, shear response, and permeability. Recently, advances in microscale technology have introduced microfluidic systems as alternatives to conventional ICF devices, with a multitude of practical advantages not available at the macroscale. However, acceptance of microfluidics as a viable platform has thus far been reserved because utility of microfluidics has yet to be fully demonstrated. For biologists to embrace microfluidics, engineers must validate microscale systems and prove their practicality as tools for cell biology. Microfluidic devices were designed, fabricated, and implemented to study properties of two EC types: aortic ECs and valve ECs. The objective was to streamline experimentation to reveal phenotypic traits of the two types and in the process demonstrate the usefulness of microfluidics. The first task was to develop a protocol to isolate pure populations of valve ECs because reported methods were inadequate. Dispase and collagenase in combination for leaflet digestion followed by clonal expansion of cell isolates was optimal for obtaining pure valve EC populations. Using a parallel microfluidic network, we discovered that valve ECs adhered strongly and spread well only on fibronectin and not on type I collagen. In contrast, aortic ECs adhered strongly on both proteins. Both aortic and valve ECs were then exposed to shear and analyzed for cell orientation. Morphological analyses showed aortic and valve ECs both aligned parallel to flow when sheared in a macroscale flow chamber, but aortic ECs aligned perpendicular to flow when sheared in a microchannel. Finally, a microfluidic membrane device was designed and characterized as a potential tool for measuring albumin permeability through sheared endothelial monolayers. Overall, these studies revealed novel EC characteristics and phenomena, and demonstrated accessibility of microfluidics for EC studies.

Calcific aortic valve sclerosis is characterized by focal lesions in the valve leaflet. These lesions are rich in myofibroblasts that express α-SMA and cause fibrosis. Lesions tend to occur in regions of the leaflet that are subjected to large bending loads, suggesting a mechanobiological basis for myofibrogenic differentiation and valve pathogenesis. In this thesis, a bioreactor was developed to study the effect of physiological loading on myofibrogenic differentiation of valve interstitial cells. Cyclic loading of native porcine aortic valve leaflets ex vivo resulted in increased α-SMA expression, predominantly in the fibrosa and spongiosa (similar to sclerotic leaflets). Cofilin, an actin-binding protein, was also upregulated by loading, suggesting it plays a role in mechanically-induced myofibrogenesis. Similarly, loading of a tissue engineered aortic valve leaflet model resulted in increased α-SMA transcript and protein expression. These data support an integral role for mechanical stimuli in myofibrogenic differentiation and sclerosis in the aortic valve.

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.

Turbulent flow downstream of a bileaflet mechanical heart valve is investigated using digital particle image velocimetry. Evolution of flow structures during the systole and diastole phases of a typical cardiac cycle is characterized by obtaining global flow velocity measurements in multiple cross-sections of the flow field. Instantaneous and time-averaged patterns of flow velocity, vorticity, and streamline topology are used to illustrate the interaction between the unsteady vortices that results in elevation of shear stress levels. This image-based approach can potentially lead to development of methods of control of platelet activation and provides insight into the underlying flow physics.

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.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Description based on contents viewed June 24, 2007; title from title screen. Includes bibliographical references (p. 76-80).

Η εκφυλιστική στένωση της αορτικής βαλβίδας και τα οξέα στεφανιαία σύνδρομα αποτελούν τις σημαντικότερες αιτίες θανάτου από καρδιαγγειακά νοσήματα. Είναι τεκμηριωμένο ότι ο ρόλος της ασβεστοποίησης στην παθοφυσιολογία των ανωτέρω νοσημάτων είναι σημαντικός και αναμφισβήτητος. Μέχρι πρόσφατα θεωρούταν ότι η ασβεστοποίηση αποτελεί παθητική διαδικασία εναπόθεσης αλάτων ασβεστίου σε ιστούς που έχουν υποστεί κάποιου βαθμού βλάβη. Ωστόσο τελευταία δεδομένα υποδεικνύουν ότι πρόκειται για ενορχηστρωμένη διαδικασία που έχει ως αποτέλεσμα την κυτταρική διαφοροποίηση και την ενεργοποίηση μεταγραφικών παραγόντων που σχετίζονται με τον οστίτη ιστό. Προκειμένου να τεκμηριώσουμε την άποψη ότι η ασβεστοποίηση των αορτικών βαλβίδων και στεφανιαίων αρτηριών στηρίζεται σε μία ενεργό διαδικασία που περιλαμβάνει την ενεργοποίηση χονδρο – οστεογενών οδών, μελετήσαμε ανοσοϊστοχημικά για πρώτη φορά την έκφραση των παραγόντων NFATc1 και Osterix. Επιπρόσθετα, διερευνήσαμε άλλα χαρακτηριστικά του προγράμματος οστεογενούς και χονδρογενούς διαφοροποίησης όπως την έκφραση των παραγόντων OPG, RANKL, RANK, Runx2 και Sox9 καθώς και τη συμμετοχή της φλεγμονής, της νεοαγγείωσης και της υπερπλασίας κυττάρων που εκφράζουν α - SMA. Στην παρούσα ερευνητική εργασία τεκμηριώνεται για πρώτη φορά η συμμετοχή των βασικών ρυθμιστικών παραγόντων των οστών NFATc1 και Osterix στη διαδικασία ασβεστοποίησης των αορτικών βαλβίδων και των στεφανιαίων αρτηριών στον άνθρωπο. Επιπρόσθετα, επιβεβαιώνεται η συμβολή των παραγόντων Runx2 και Sox9 στη δημιουργία αποτιτανώσεων στους συγκεκριμένους ιστούς. Οι αλλαγές στην έκφραση του συμπλέγματος OPG/RANKL/RANK σχετίζονται με την ασβεστοποίηση της αορτικής βαλβίδας. Αντίθετα, το προφίλ έκφρασης του συμπλέγματος δεν είναι σταθερό στις στεφανιαίες αρτηρίες επιβεβαιώνοντας αντικρουόμενα αποτελέσματα προηγούμενων μελετών. Τέλος, επιβεβαιώνεται η συμμετοχή της φλεγμονής, της νεοαγγείωσης και της υπερπλασίας των κυττάρων με συσταλτικό φαινότυπο στην εξέλιξη της παθοφυσιολογικής διεργασίας. Από την παρούσα μελέτη διαπιστώνουμε ότι η διαδικασία της ασβεστοποίησης στις αορτικές βαλβίδες και τις στεφανιαίες αρτηρίες παρουσιάζει αρκετές ομοιότητες με την οστεογένεση. Αυτό συνεπάγεται ευοίωνες προοπτικές για δυνητική γονιδιακή παρέμβαση σε πρώιμα στάδια που θα μπορούσε να οδηγήσει σε αναστροφή της παθοφυσιολογικής διαδικασίας εναπόθεσης ασβεστίου. / Degenerative aortic stenosis and acute coronary syndromes constitute major causes of cardiovascular morbidity. There is evidence that calcification plays significant role in pathophysiology of these diseases. Until recently, calcification was considered to be a passive process of calcium deposition in injured tissue. However, recent data suggest that calcification of aortic valves and coronary arteries is an active process related to cellular differentiation and transcription of bone regulators. In order to provide further evidence that aortic valve and coronary artery calcification is an active process involving chondro-osteogenic pathways, we investigated using immunohistochemistry the expression of NFATc1 and Osterix in human calcified aortic valves and coronary arteries, which to the best of our knowledge has not been reported previously. Additionally, we investigated in our specimens other features of chondro/osteogenic differentiation program such as the expression of OPG, RANKL, RANK, Runx2 and Sox9, and the participation of inflammation, neovessel formation and hyperplasia of α - SMA positive cells in calcification process. Our results provide evidence for the involvement of bone regulatory factors NFATc1 and Osterix in aortic valve and coronary artery calcification process in human. In addition, we confirm Runx2 and Sox9 expression in diseased specimens. Expression pattern of OPG / RANKL / RANK system is related to aortic valve calcification. Consistently with previous reports, the role of OPG / RANKL / RANK system in coronary artery calcification is not clear. Finally, our study confirms involvement of inflammation, neovessel formation and hyperplasia of α - SMA positive cells in calcification process. Present study demonstrates that aortic valve and coronary artery calcification is actually an active process sharing features with developmental osteogenesis. This fact implies promising prospects for potential genetic intervention in early stages that could lead to inhibition of calcification process.