bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ice-Free-Cryopreservation Attenuates Calcification in Allograft Heart Valves
Authors: Lisy Milan , Brockbank Kelvin G.M. , Schenke-Layland Katja , Fend Falko , Moritz Anton , Stock Ulrich A. 
Published: July 2012

AbstractThe objective of the study was to attenuate calcification in allogeneic ovine pulmonary heart valves. Six valves of white face sheep were ice-free-cryopreserved (STUDY) in 12.6 mol/L cryoprotectant (4.65, 4.65, and 3.31 mol/L of DMSO, formamide and 1,2-propanediol) and stored at -80°C. 6 control valves were cryopreserved by controlled slow rate freezing in 1.4 mol/L DMSO and stored in vapor-phase nitrogen (CONTROL). After 7 months in vivo explanted valves were processed for histopathology. Gross morphology showed significantly thickened leaflets in the CONTROL group. Histopathology revealed a marked calcification in the leaflet stroma and conduit wall. STUDY valves in contrast demonstrated well preserved ECM structures, no leaflet thickening, inflammation and only neglectable calcification in the conduit wall. Only discrete panus formation was noted migrating from the ventricularis onto the leaflet. Ice-free-cryopreservation enables attenuation of calcification in ovine allografts valves. The observed decreased calcification warrant improved long-term function.
Investigation of the Suitability of Decellularised Porcine Pericardium for Mitral Valve Reconstruction
Authors: Morticelli Lucrezia , Thomas Daniel , Ingham Eileen , Korossis Sotiris 
Published: July 2012

AbstractThe aim of this study was to investigate the suitability of decellularised porcine pericardium for heterotopic repair of the mitral valve (MV) leaflets, and its potential to regenerate through endogenous cell repopulation in vivo, or in vitro seeding and bioreactor conditioning. Anterior and posterior MV leaflets and pericardia were excised from porcine hearts within. The pericardia were decellularised according to the in-house protocol. Anterior and posterior leaflet, and decellularised and fresh pericardial samples were subjected to histology (H and E, Masson trichrome, Sirius Red, Miller’s elastin, Alcian blue-PAS), immunohistochemistry (collagen type I, III, IV, fibronectin, laminin, and chondroitin sulfate labelling), SEM, and uniaxial tensile testing. Samples were isolated along the radial and circumferential direction (leaflets), and perpendicular and parallel to the collagen fibres (pericardium). Biochemical assays for quantification of the sulphated GAG and collagen content of the tissues were also performed. Contact and extract cytotoxicity testing, and DNA quantification was performed to assess the decellularised pericardia. Histology revealed the trilaminar structure of the pericardium and quadrilaminar structure of the leaflets. Collagen type I and III was found in the fibrosa layers of both pericardium and leaflets, whereas fibronectin and laminin were found throughout the tissues. Decellularisation produced a completely acellular pericardial scaffold, which retained the histoarchitecture of the natural tissue. The biomechanics showed the anterior leaflets being stiffer along the circumferential direction. No significant anisotropy was observed in the biomechanics of the posterior leaflets, or fresh and decellularised pericardium. The anisotropy of the anterior leaflet was attributed to the orientation of the collagen (aligned along the circumferential direction). Biochemistry showed a significant increase in sulphated GAGs between the fresh leaflets and pericardium. No difference was found between the collagen content of the fresh leaflets and the fresh or decellularised pericardium. The decellularised pericardium showed a 99% reduction in DNA and a high loss in the GAG content compared to the fresh pericardium.
The study showed that the MV leaflets and pericardium share similar histoarchitectures and comparable biomechanics. The similarity was more pronounced in the case of the posterior leaflet which was more isotropic both in terms of histoarchitecture and biomechanics. Apart from a decreased GAG content, the similarity was also apparent between the leaflets and the pericardial scaffolds. The decellularised pericardium has the potential to deliver the necessary biological and biomechanical cues to seeded or migrating cells, representing a plausible scaffold option for the regeneration of the MV leaflets in vitro or in vivo.
Integration of Microstructural Architecture of the Mitral Valve into an Anatomically Accurate Finite Element Mesh
Authors: Amini Rouzbeh , van Loosdregt Inge , Koomalsingh Kevin , Gorman Robert C. , Gorman Joseph H. , Sacks Michael S. 
Published: July 2012

AbstractAlthough mitral valve (MV) repair initially restores normal leaflets coaptation and stops MV regurgitation, in long term it can also dramatically change the leaflet geometry and stress distribution that may be in-part responsible for limited repair durability. As shown for other collagenous tissues, such changes in geometry and loading reorganize the fiber architecture. In addition, MV interstitial cells may also respond to the altered stress by reducing biosynthetic function, which would affect the load-bearing capabilities of MV and its long-term durability. Thus, investigating the repair-induced MV stress and the concomitant microstructural alterations is a key step in assessing the repaired valve durability. Finite element models have been widely used for stress analysis of the mitral valve. Most of these models, however, have employed only basic constitutive models and above all ignore the complex microstructure of the MV. In addition, the geometry of the valve is usually simplified. Thus, in this work we developed a method to obtain accurate geometrical model of the ovine MV and quantify its fiber structure for the purposes of developing high fidelity computational meshes of the MV. To obtain an accurate geometry of the MV, microcomputed tomography (micro-CT) was used. The entire heart was scanned via a SIEMENS Inveon CT scanner. Three-dimensional scans were segmented semi-automatically using ScanIP segmentation software. The 3D positional data of the fiducial markers were also obtained via ScanIP masks generated by using gray-scale threshold of the CT scans. The segmented geometry was then converted to finite element meshes using ScanIP mesh free mesh generator scheme. Next, the anterior leaflet was then dissected and prepared for measurements of its fiber alignment. The positional data of each point on the accurate mesh was then projected onto the 3D marker mesh. By using a computational domain, the projected point was mapped back to the 2D flattened surface. In addition to mapping, the current method can be used to estimate the changes in connective tissue structure with deformation. This is done by for each point on the valve surface using the local right Cauchy strain tensor C using an in-plane convective curvilinear coordinate system to convect the local fiber orientation to predict the current fiber alignment. To conclude, a robust technique to quantify and map the fibrous microstructure of the MV anterior leaflet to anatomically accurate 3D MV shape derived from micro-CT imaging was developed. The method provides a framework for development of anatomically and micro-structurally accurate finite element models of MV using our tissue structure-based models. It can also be used as a means to validate predicted changes in fibrous structure due to altered stress following surgical interventions.
Valve Calcification on Computed Tomography Can Estimate Aortic Stenosis Severity
Authors: Chitsaz Sam , Blackshear Charlie , Tegegn Nebiyu , Wisneski Andrew , Azadani Ali N. , Ge Liang , Hope Michael D. , Tseng Elaine E. 
Published: July 2012

AbstractUse of coronary CT angiography for screening of coronary artery disease is being advocated for the general population. Meanwhile, CT is increasingly used in preoperative planning for transcatheter aortic valve replacement (TAVR). Although aortic stenosis (AS) severity can be evaluated by measurement of incidentally found aortic valve calcification on CT, it has not been validated by pathologic specimens and can be confounded by calcification of adjacent structures as well as motion artefact. Micro-computed tomography (microCT) provides ultra-high resolution imaging of small structures to yield excellent estimation of tissue calcification. In this study, excised aortic valves from patients with confirmed AS were used to determine if the amount of calcium on microCT correlated with severity of aortic stenosis. Thirty-five aortic valves excised during surgical valve replacement underwent micro-CT imaging with resolution of 76μm in the axial direction. Amount of calcium was determined by absolute and proportional values of calcium volume. Correlation of calcium volume and preoperative mean aortic valve gradient (MAVG), peak transaortic velocity (Vmax), and aortic valve area (AVA) on echocardiography was evaluated. For the patients who had a preoperative CT scan with acceptable image quality, the amount of valvular calcification was also measured by a well-experienced radiologist using modified Agatston algorithm. Mean amount of calcium across all valves was 603.2±398.5mm3, while mean ratio of calcium volume to total valve volume was 0.36±0.16. Mean aortic valve gradient correlated positively with both calcium volume and ratio (r=0.72, p<0.001). Vmax also positively correlated with calcium volume and ratio (r=0.69 and 0.76 respectively, p<0.001). A logarithmic curvilinear model was best fit to the correlation. Calcium volume of 480mm3 showed sensitivity and specificity of 0.76 and 0.83, respectively for severe AS diagnosis, while calcium ratio of 0.37 yielded sensitivity and specificity of 0.82 and 0.94, respectively. Calcium volume and its proportion to total valve volume were found to be good predictive parameters for severe AS when estimated radiologically. Calcium volume quantification may be a complimentary measure for AS severity evaluation in situations where aortic valve calcification is found incidentally on CT as well as in preoperative assessment of aortic valves for TAVR.
Functional Mitral Regurgitation Is a Main Determinant Of Adverse Outcome In Patients With Heart Failure Due To Non-Ischemic Dilated Cardiomyopathy.
Authors: Mauro Toniolo , Andrea Rossi , Mariantonietta Cicoira , Corinna Bergamini , Corrado Vassanelli 
Published: July 2012

AbstractIschemic mitral regurgitation has been recently demonstrated to carry important prognostic information in patients with left ventricular dysfunction due to coronary artery disease. There is no information regarding the prognostic role of functional mitral regurgitation in patients with non ischemic dilated cardiomyopathy. Patients with stable heart failure due to non-ischemic dilated cardiomyopathy were prospectively enrolled. All patients underwent a comprehensive echocardiographic assessment. Left ventricular diastolic (LVD) , systolic (LVS) diameters, left atrial diameter (LAD), ejection fraction (EF) and restrictive mitral filling pattern (RMP) was measured. Mitral regurgitant volume (RV) was measured by means of proximal isovelocity surface area method. The end point of the study was death or hospitalization for worsening heart failure. 80 patients (mean age 61±9 years; 82% male) were enrolled. 10 patients reached the end point of the study. At univariate Cox analysis, the echocardiographic variables associated with outcome were: EF (HR 0.84 95% CI 0.75 0.94; p=0.002), RMP (HR 5.2 95% CI 1.4 19.7; p=0.01) and RV (HR 1.046 95% CI 1.02 1.07; p=0.0005), LVS/BSA (HR 1.2 95% CI 1.02 1.4; p=0.03). At multivariate analysis RV remained the only variables independently associated with outcome (p=0.04). Result did not change when LVS/BSA substituted EF in the model. Receiving operator characteristics analysis documented that the area under the curve for RV in identifying patients with adverse outcome was 0.84±0.06 (95% CI 0.74 0.91) and the best cut off value for RV was 28 ml (sensitivity 80% 95% CI 44 97 and specificity 87% 95% CI 77 94). Patients with RV<28 had a survival rate of 95% after 6 years from the index echocardiogram compared with 22% in those with RV> 28 (longrank 23; p<0.0001). In patients with non-ischemic dilated cardiomyopathy, RV was a main predictor of death or hospitalization for worsening heart failure.
Fluid-Structure Interaction Simulation of an Aortic Bi-Leaflet Mechanical Heart Valve in a Patient-Specific Left Heart
Authors: Bao Le Trung , Sotiropoulos Fotis 
Published: July 2012

AbstractA large-scale kinematic model is developed for animating the left ventricle (LV) wall to drive the fluid-structure interaction (FSI) between the ensuing blood flow and a mechanical heart valve prosthesis implanted in the aortic position of an anatomic LV/aorta configuration. The kinematic model is of lumped type and employs a cell-based, FitzHugh-Nagumo framework to simulate the motion of the LV wall in response to an electrical wavefront propagating along the heart wall. The emerging large-scale LV wall motion exhibits complex contractile mechanisms that include contraction (twist) and expansion (untwist). The kinematic model is shown to yield global LV motion parameters that are well within the physiologic range throughout the cardiac cycle. The FSI between the leaflets of the mechanical heart valve and the blood flow driven by the dynamic LV wall motion and mitral inflow is simulated using the curvilinear immersed boundary (CURVIB) method (Ge et al., J. Comp. Physics., 2007 and Borazjani et al., J. Comp. Physics, .2008) implemented in conjunction with a domain decomposition approach. The computational results show that the simulated flow patterns are in good qualitative agreement with in vivo observations. The simulations also reveal complex kinematics of the valve leaflets, thus, underscoring the need for patient-specific simulations of heart valve prosthesis and other cardiac devices.
Functional Performance and Biomechanics of Decellularized Human Aortic Valves
Authors: Arnold Stacy M. G. , Goldstein Steven , Gale David C. 
Published: July 2012

AbstractAllograft decellularization based on detergents and/or enzymes to reduce antigenicity has been reported to damage tissue structure. We applied to human aortic valves a non-detergent/non-protease decellularization treatment prior to cryopreservation. To ensure that the method did not negatively impact valve structure, we submitted decellularized and conventional human aortic valves to pulsatile flow characterizations and accelerated wear testing (to 80 million cycles) under both normal and elevated aortic valve flow conditions. The biomechanical properties of decellularized aortic valve tissues were compared to those of non-decellularized aortic valves.
Valve performance was assessed using six conventional and six decellularized human aortic valves (internal valve diameter of 21mm±1mm). Valves were placed in accelerated wear testers, at a cycle rate of 200beats/min as specified in ISO 5840. All valves underwent pulsatile flow characterization before testing and at 20 million cycle intervals up to 80 million loading cycles (pressure>100mmHg). Images captured during pulsatile testing at peak systole and diastole were used to evaluate proper valve function, full leaflet coaptation and wear related damage.
Tissue biomechanics was evaluated pair-wise using ten bisected valves, half conventionally treated, half decellularized. For each, conduit and leaflet circumferential ultimate tensile strength (UTS), and conduit and myocardium suture retention strength were evaluated. Compared to conventional human aortic heart valves, the decellularized valves showed comparable valve performance based on effective orifice area before accelerated testing (1.57±0.3 vs 1.51±0.2 cm2, decellularized and conventional, respectively) and similar non-significant decrease after reaching an accumulated 80 million cycles (1.40±0.2 vs. 1.45±0.3 cm2). Both populations met the minimum performance requirements specified in ISO 5840 for effective orifice area and regurgitant fraction. There was no significant increase in retrograde flow due to post-wear leakage. Biomechanical testing demonstrated leaflet and conduit circumferential UTS and conduit and myocardium suture retention strength of decellularized valves were equal to or greater than the conventional valves. From these measurements we conclude that there is no quantifiable impact on valve functionality, performance or biomechanics due to the SynerGraft® (non-detergent based) decellularization process.
Autologous Bone Marrow Mononuclear Cell-Based Tissue Engineered Heart Valves: First Experiences with a One-step Intervention in Primates
Authors: Weber Benedikt , Emmert Maximilian Y. , Scherman Jacques , Gruenenfelder Juerg , Frese Laura , Brokopp Chad , Falk Volkmar , Zilla Peter , Hoerstrup Simon P. 
Published: July 2012

AbstractA living heart valve with regeneration capacity based on autologous cells and minimally invasive implantation technology would represent a substantial improvement upon contemporary heart valve prostheses. This study investigates the feasibility of injectable, marrow stromal cell-based, autologous, living tissue engineered heart valves (TEHV) generated and implanted in a one-step intervention in non-human primates. Trileaflet heart valves were fabricated from non-woven biodegradable synthetic composite scaffolds and integrated into self-expanding nitinol stents. During the same intervention autologous bone marrow-derived mononuclear cells were harvested, seeded onto the scaffold matrix, and implanted transapically as pulmonary valve replacements into non-human primates (n=6). The transapical implantations were successful in all animals and the overall procedure time from cell harvest to TEHV implantation was 118±17 min. In vivo functionality assessed by echocardiography revealed preserved valvular structures and adequate functionality up to 4 weeks post implantation. Substantial cellular remodeling and in-growth into the scaffold materials resulted in layered, endothelialized tissues as visualized by histology and immunohistochemistry. Biomechanical analysis showed non-linear stress-strain curves of the leaflets, indicating replacement of the initial biodegradable matrix by living tissue.
Here we provide a novel concept demonstrating that heart valve tissue engineering based on a minimally invasive technique for both cell harvest and valve delivery as a one-step intervention is feasible in non-human primates. This innovative approach may overcome the limitations of contemporary surgical and interventional bioprosthetic heart valve prostheses.
The Effect of Side-specific Valve Endothelial Cells on Extracellular Matrix Production by Valve Interstitial Cells
Authors: Mongkoldhumrongkul Napachanok , Yacoub Magdi H. , Chester Adrian H. 
Published: July 2012

AbstractValve endothelial cells (VECs) play an important role in regulating the function of the underlying interstitial cells (VICs). However, the regulatory effects VECs from each side of the valve on the production of ECM proteins by VICs have not been studied. This study aims to determine the regulatory effects of VECs isolated from the aortic (aVECs) and ventricular (vVECs) surfaces of the aortic valve on the production of collagen, glycosaminoglycan (GAGs) and elastin by VICs.
Side-specific VECs were co-cultured with VICs using Transwell® inserts and the effects on extracellular matrix production by VICs were investigated by quantifying the amount of secreted collagen and sulphate GAGs by VICs as well as examining gene expressions of collagen, GAGs and elastin components by VICs. Collagen production by VICs was significantly increased by co-culturing with aVEC and vVECs to 154.38 ± 13.71% (p=0.041) and 196.35 ± 16.59% (p=0.008), respectively, of the control (VIC culture without VECs). Furthermore, vVECs significantly enhanced production of sulphate GAGs by VICs to 217.18 ± 32.9% (p=0.008) above control whereas aVECs showed an increase of 150.08 ± 18.0%, which was non-significance. There was no significant difference between sulphate GAGs release in response to vVECs and aVECs. Only fibrillin 1, a component of elastin, gene expression was increased by co-culturing VICs with aVEC, 2.07 ± 0.34 (p=0.008), and vVECs, 2.13 ± 0.31 (p=0.03) fold increase above control. In contrast, media collected over a 48 hour period from aVEC or vVEC cultures and subsequently incubated with VICs (in the absence of VECs) showed no induction on the ECM production by VICs. In conclusion, aVECs and vVECs induce the ECM production and expression by releasing labile molecules which are degradable or lose their activities with time. Further experiments are necessary to identify the mediators that produce these effects and to determine how their release is modulated by the different flow patterns experienced by aVECs and vVECs. This study further highlights the complex interaction and communication between different cell types present in the valve cusps.
Immunological Effects of [alpha]Gal-positive and [alpha]Gal Knockout Biological Heart Valves
Authors: McGregor Christopher G. A. , Kogelberg Heide , Byrne Guerard W. 
Published: July 2012

AbstractAs immune responses likely contribute to degeneration of bioprosthetic heart valves (BHVs), this nonhuman primate study compares the anti-Gal antibody response to BHVs from wild type (WT) pigs (current BHVs) and those from α-galactosyltransferase knockout (GTKO) pigs.
Stented glutaraldehyde fixed BHVs from WT (n=4) and GTKO (n=3) pigs were commercially manufactured and implanted in the mitral position in nonhuman primates using standard surgical techniques. Recipients were treated with Lovenox (1mg/kg BID) for 5 weeks reducing to 1mg/kg daily for one week and then discontinued. Recipients were sensitized to the αGal antigen by immunization to match IgG levels found in humans. Serum antibody responses were monitored by ELISA. WT BHVs were explanted at 3 hours, 1 year, 2 years and the fourth is currently ongoing at 3 years. One GTKO BHV was explanted at 218 days. The remaining two GTKO BHVs are currently ongoing at 3 years. After immunization, circulating anti-Gal IgG levels were comparable in both groups at the time of implantation and were equal or greater than human levels. Anti-Gal antibody levels decreased in both WT and GTKO recipients after implantation. WT recipients, however, retained elevated levels (greater than 20% preimplant values) of anti-Gal IgG for at least the first year post implant. Conversely anti-Gal IgG levels in all GTKO recipients fell within one month and remained at less than 20% preimplant values. Analysis of the area under the curve showed a significant increase of anti-Gal IgG in the WT BHV group compared to GTKO BHV recipients (p<0.01). In this nonhuman primate model, the persistently and significantly (p<0.01) elevated levels of anti-Gal IgG antibody observed in WT but not GTKO BHV recipients, indicate continuing immune stimulation to the αGal antigen. Current commercially available BHVs are similarly known to contain αGal antigen. Anti-Gal antibody has been shown to increase calcification of processed pericardium in the rat implant model. These data support the hypothesis that preformed and induced anti-Gal antibody in BHV recipients may initiate an early immune response, which promotes subsequent calcification. BHVs made from GTKO pigs would eliminate this major xenoreactive antigen and provide a prosthesis with reduced immunogenicity. Such BHVs made from GTKO pigs may have greater durability and be potentially used in younger patients with more active immune systems.