Heart Valve Tissue Engineering Research Articles

Unraveling the Mechanisms of Endogenous Tissue Restoration after Bioresorbable Pulmonary Valve Implantation in Sheep

Objective: Endogenous Tissue Restoration (ETR) utilizes the regenerative response of the human body to transform an off-the-shelf available, synthetic, absorbable graft into a living functional valve. Recent preclinical studies have shown the principle of ETR for heart valve grafts to be promising1Bennink G Torri S Brugmans M et al.A novel restorative pulmonary valved conduit in a chronic sheep model: Mid-term hemodynamic function and histologic assessment.J Thorac Cardiovasc Surg. 2018; 155 (doi:10.1016/j.jtcvs.2017.12.046.): 2591-2601Google Scholar,2Kluin J Talacua H Smits AIPM et al.In situ heart valve tissue engineering using a bioresorbable elastomeric implant – From material design to 12 months follow-up in sheep.Biomater. 2017; 125 (doi:10.1016/j.biomaterials.2017.02.007.): 101-117Google Scholar. However, further detailed knowledge on the underlying mechanisms of the material-driven regenerative response remains elusive. The goal of the present study was to gain a mechanistic understanding of these processes by histopathological analysis of ETR heart valves. Methods: In this study, Xeltis Pulmonary Valved Conduits (XPV, Xeltis B.V., Eindhoven, The Netherlands) implanted in an ovine model were analyzed. Explanted valves (follow-up time: 2, 6, 12 (N=5 per timepoint) and 24 months (N=2)) were embedded in paraffin and sectioned longitudinally. Spatiotemporal analysis was performed using a comprehensive sheep-specific antibody panel3Dekker S van Geeman D van den Bogaerdt AJ et al.Sheep-specific immunohistochemical panel for the evaluation of regenerative and inflammatory processes in tissue-engineered heart valves.Front. Cardiovasc. Med. 2018; 5 (doi:10.3389/fcvm.2018.00105.): 105Google Scholar. Results: Detailed knowledge on graft absorption as well as neo-tissue formation and a better understanding of cellular influences was obtained. Interestingly, foreign body giant cells were located within the graft material at iNOS-rich degradation and tissue remodeling sites in the hinge region of the leaflet, starting as early as 2 months after implantation. In the conduit material, on the other hand, foreign body giant cells remained on the outer layers with only limited infiltration into the scaffold material. Interestingly, at the same time point vascularization was observed throughout the conduit material. Extracellular matrix components, such as collagens and elastin were formed in a highly heterogeneous fashion, suggesting an important role for hemodynamic loads on the inflammatory and regenerative processes. Conclusions: Our results enhance the mechanistic understanding of material-driven endogenous tissue restoration. These findings also highlight, the importance of the micro-environment imposed by the graft material on the regenerative response towards a biomaterial. KEYWORD: ICTEHV-O-02 The authors do not declare any conflict of interest.

Polymer Fiber-reinforced GAG Based Hydrogel Scaffolds for Heart Valve Tissue Engineering

Objective: An ideal scaffold for TE valve replacement requires native features such as the anisotropic collagen architecture and its surrounding GAG matrix. In this study, we propose to fabricate a...

Acute In Vivo Functional Assessment of a Biodegradable Stentless Elastomeric Tricuspid Valve.

Degradable heart valves based on in situ tissue regeneration have been proposed as potentially durable and non-thrombogenic prosthetic alternatives. We evaluated the acute in vivo function, microstructure, mechanics, and thromboresistance of a stentless biodegradable tissue-engineered heart valve (TEHV) in the tricuspid position. Biomimetic stentless tricuspid valves were fabricated with poly(carbonate urethane)urea (PCUU) by double-component deposition (DCD) processing to mimic native valve mechanics and geometry. Five swine then underwent 24-h TEHV implantation in the tricuspid position. Echocardiography demonstrated good leaflet motion and no prolapse and trace to mild regurgitation in all but one animal. Histology revealed patches of proteinaceous deposits with no cellular uptake. SEM demonstrated retained scaffold microarchitecture with proteinaceous deposits but no platelet aggregation or thrombosis. Explanted PCUU leaflet thickness and mechanical anisotropy were comparable with native tricuspid leaflets. Bioinspired, elastomeric, stentless TEHVs fabricated by DCD were readily implantable and demonstrated good acute function in the tricuspid position.

Tissue-engineered heart valves predicted to be cost effective

Tissue-engineered heart valves predicted to be cost effective

Early cost-utility analysis of tissue-engineered heart valves compared to bioprostheses in the aortic position in elderly patients

ObjectivesAortic valve disease is the most frequent indication for heart valve replacement with the highest prevalence in elderly. Tissue-engineered heart valves (TEHV) are foreseen to have important advantages over currently used bioprosthetic heart valve substitutes, most importantly reducing valve degeneration with subsequent reduction of re-intervention. We performed early Health Technology Assessment of hypothetical TEHV in elderly patients (≥ 70 years) requiring surgical (SAVR) or transcatheter aortic valve implantation (TAVI) to assess the potential of TEHV and to inform future development decisions.MethodsUsing a patient-level simulation model, the potential cost-effectiveness of TEHV compared with bioprostheses was predicted from a societal perspective. Anticipated, but currently hypothetical improvements in performance of TEHV, divided in durability, thrombogenicity, and infection resistance, were explored in scenario analyses to estimate quality-adjusted life-year (QALY) gain, cost reduction, headroom, and budget impact.ResultsDurability of TEHV had the highest impact on QALY gain and costs, followed by infection resistance. Improved TEHV performance (− 50% prosthetic valve-related events) resulted in lifetime QALY gains of 0.131 and 0.043, lifetime cost reductions of €639 and €368, translating to headrooms of €3255 and €2498 per hypothetical TEHV compared to SAVR and TAVI, respectively. National savings in the first decade after implementation varied between €2.8 and €11.2 million (SAVR) and €3.2–€12.8 million (TAVI) for TEHV substitution rates of 25–100%.ConclusionsDespite the relatively short life expectancy of elderly patients undergoing SAVR/TAVI, hypothetical TEHV are predicted to be cost-effective compared to bioprostheses, commercially viable and result in national cost savings when biomedical engineers succeed in realising improved durability and/or infection resistance of TEHV.

Porcine Small Intestinal Submucosa Mitral Valve Material Responses Support Acute Somatic Growth.

Background: Conceptually, a tissue engineered heart valve would be especially appealing in the pediatric setting since small size and somatic growth constraints would be alleviated. In this study, we utilized porcine small intestinal submucosa (PSIS) for valve replacement. Of note, we evaluated the material responses of PSIS and subsequently its acute function and somatic growth potential in the mitral position. Methods and Results: Material and mechanical assessment demonstrated that both fatigued 2ply (∼65 μm) and 4ply (∼110 μm) PSIS specimens exhibited similar failure mechanisms, but at an accelerated rate in the former. Specifically, the fatigued 2ply PSIS samples underwent noticeable fiber pullout and recruitment on the bioscaffold surface, leading to higher yield strength (p < 0.05) and yield strain (p < 0.05) compared to its fatigued 4ply counterparts. Consequently, 2ply PSIS mitral valve constructs were subsequently implanted in juvenile baboons (n = 3). Valve function was longitudinally monitored for 90 days postvalve implantation and was found to be robust in all animals. Histology at 90 days in one of the animals revealed the presence of residual porcine cells, fibrin matrix, and host baboon immune cells but an absence of tissue regeneration. Conclusions: Our findings suggest that the altered structural responses of PSIS, postfatigue, rather than de novo tissue formation, are primarily responsible for the valve's ability to accommodate somatic growth during the acute phase (90 days) following mitral valve replacement. Impact Statement Tissue engineered heart valves (TEHVs) offer the potential of supporting somatic growth. In this study, we investigated a porcine small intestinal submucosa bioscaffold for pediatric mitral heart valve replacement. The novelty of the study lies in identifying material responses under mechanical loading conditions and its effectiveness in being able to function as a TEHV. In addition, the ability of the scaffold valve to support acute somatic growth was evaluated in the Baboon model. The current study contributes toward finding a solution for critical valve diseases in children, whose current prognosis for survival is poor.

Recent investigation on biomaterial based tissue engineered heart valve (TEHV)

In recent years the concept of tissue-engineered heart valves provides advanced treatment for creating a living heart valve replacing the failed one. Valvular Heart Disease (VHD) is the most common disease in failing one or more valves in the heart, for those people from various countries are being affected in a huge number. This may be due to valvular stenosis (abnormal narrowing in valves of the heart), valvular prolapse and regurgitation (backflow of blood or due to leakage). This study was designed to overcome the failure faced by the present bioprosthetic heart valves as well as tissue-engineered heart valves by bringing in an optimized advanced material using the present biopolymers. The main reason for the usage of biopolymers in this study is due to its good physiochemical and mechanical properties as compared to other existing materials which is been used in the manufacturing of heart valves. A crucial factor of this methodology is to solve problems like calcification at the surface of the material, thrombosis, degeneration, and others. Bio polymeric materials generally possess good resistance towards oxidation and hydrolysis with good stability. As there are many existing materials available to manufacture heart valves, in this review the materials that are investigated are Polyurethane (PU), Polydimethyl Siloxane (PDMS) - Polyhexamethylene Oxide (PHMO) PU, and POSS-PCU Nanocomposite (Polyhedral Oligomeric Silsesquioxane - Polycarbonate Urethane). These biopolymer materials exhibit long term stability, resulting in good mechanical properties and enhanced resistance towards hydrolysis, oxidation. These materials also result in reduced calcification and thrombosis.

Structure and Rheological Properties of Bovine Aortic Heart Valve and Pericardium Tissue: Implications in Bioprosthetic and Tissue-Engineered Heart Valves.

Heart valve (HV) diseases are among the leading causes of cardiac failure and deaths. Of the various HV diseases, damaged HV leaflets are among the primary culprits. In many cases, impaired HV restoration is not always possible, and the replacement of valves becomes necessary. Bioprosthetic HVs have been used for the replacement of the diseased valves, which is obtained from the sources of bovine and porcine origin, while tissue-engineered heart valves (TEHV) have emerged as a promising future solution. The bioprosthetic valves are prone to become calcified, and thus they last for only ten to fifteen years. The adequate understanding of the correlations between the biomechanics and rheological properties of native HV tissues can enable us to improve the durability of the bioprosthetic HV as well as help in the development of tissue-engineered heart valves (TEHV). In this study, the structural and rheological properties of native bovine aortic HV and pericardium tissues were investigated. The microstructures of the tissues were investigated using scanning electron microscopy, while the rheological properties were studied using oscillatory shear measurement and creep test. The reported results provide significant insights into the correlations between the microstructure and viscoelastic properties of the bovine aortic HV and pericardium tissues.

Differential Leaflet Remodeling of Bone Marrow Cell Pre-Seeded Versus Nonseeded Bioresorbable Transcatheter Pulmonary Valve Replacements

This study showed that bone marrow mononuclear cell pre-seeding had detrimental effects on functionality and in situ remodeling of bioresorbable bisurea-modified polycarbonate (PC-BU)-based tissue-engineered heart valves (TEHVs) used as transcatheter pulmonary valve replacement in sheep. We also showed heterogeneous valve and leaflet remodeling, which affects PC-BU TEHV safety, challenging their potential for clinical translation. We suggest that bone marrow mononuclear cell pre-seeding should not be used in combination with PC-BU TEHVs. A better understanding of cell-scaffold interaction and in situ remodeling processes is needed to improve transcatheter valve design and polymer absorption rates for a safe and clinically relevant translation of this approach.

Trilayered tissue structure with leaflet-like orientations developed through in vivo tissue engineering

A tissue-engineered heart valve can be an alternative to current mechanical or bioprosthetic valves that face limitations, especially in pediatric patients. However, it remains challenging to produce a functional tissue-engineered heart valve with three leaflets mimicking the trilayered, oriented structure of a native valve leaflet. In our previous study, a flat, trilayered nanofibrous substrate mimicking the orientations of three layers in a native leaflet—circumferential, random and radial orientations in fibrosa, spongiosa and ventricularis layers, respectively, was developed through electrospinning. In this study, we sought to develop a trilayered tissue structure mimicking the orientations of a native valve leaflet through in vivo tissue engineering, a practical regenerative medicine technology that can be used to develop an autologous heart valve. Thus, the nanofibrous substrate was placed inside the closed trileaflet-shaped cavity of a mold and implanted subcutaneously in a rat model for in vivo tissue engineering. After two months, the explanted tissue construct had a trilayered structure mimicking the orientations of a native valve leaflet. The infiltrated cells and their deposited collagen fibrils were oriented along the nanofibers in each layer of the substrate. Besides collagen, presence of glycosaminoglycans and elastin in the construct was observed.

Tissue engineering of heart valves – challenges and opportunities

Tissue engineering of heart valves – challenges and opportunities

TGF-β Signaling Promotes Tissue Formation during Cardiac Valve Regeneration in Adult Zebrafish

Cardiac valve disease can lead to severe cardiac dysfunction and is thus a frequent cause of morbidity and mortality. Its main treatment is valve replacement, which is currently greatly limited by the poor recellularization and tissue formation potential of the implanted valves. As we still lack suitable animal models to identify modulators of these processes, here we used adult zebrafish and found that, upon valve decellularization, they initiate a rapid regenerative program that leads to the formation of new functional valves. After injury, endothelial and kidney marrow-derived cells undergo cell cycle re-entry and differentiate into new extracellular matrix-secreting valve cells. The TGF-β signaling pathway promotes the regenerative process by enhancing progenitor cell proliferation as well as valve cell differentiation. These findings reveal a key role for TGF-β signaling in cardiac valve regeneration and establish the zebrafish as a model to identify and test factors promoting cardiac valve recellularization and growth.

Mechanical and finite element evaluation of a bioprinted scaffold following recellularization in a rat subcutaneous model

Tissue engineered heart valves (TEHV) provide several advantages over currently available aortic heart valve replacements. Bioprinting provides a patient-specific means of developing a TEHV scaffold from imaging data, and the capability to embed the patient's own cells within the scaffold. In this work we investigated the remodeling capacity of a collagen-based bio-ink by implanting bioprinted disks in a rat subcutaneous model for 2, 4 and 12 weeks and evaluating the mechanical response using biaxial testing and subsequent finite element (FE) modeling. Samples explanted after 2 and 4 weeks showed inferior mechanical properties compared to native tissues while 12 week explants showed a mechanical response of similar magnitude but did not demonstrate the anisotropy present in native tissues. In the FE analysis, the model utilizing mechanical properties from samples explanted after 12 weeks showed the closest mechanical behavior to the native tissues. However, in diastole native tissues showed higher stress in the leaflet belly and lower strain at the commissures compared to 12 week explants, likely due to the anisotropy present in the native tissues. Thus, either further remodeling is required in situ in the aortic valve position or by in vitro preconditioning in an environment such as a bioreactor. Regardless, these results demonstrate the utility of FE analysis to optimize bioprinting process parameters for the most favorable in vivo mechanical performance.

Optimization of polycaprolactone fibrous scaffold for heart valve tissue engineering

Pore size is generally small in nanofibrous scaffolds prepared by electrospinning polymeric solutions. Increase of scaffold thickness leads to decrease in pore size, causing impediment to cell infiltration into the scaffolds during tissue engineering. In contrast, comparatively larger pore size can be realized in microfibrous scaffolds prepared from polymeric solutions at higher concentrations. Further, microfibrous scaffolds are conducive to infiltration of reparative M2 phenotype macrophages during in vivo/in situ tissue engineering. However, rise of mechanical properties of a fibrous scaffold with the increase of polymer concentration may limit the functionality of a scaffold-based, tissue-engineered heart valve. In this study, we developed microfibrous scaffolds from 14%, 16% and 18% (wt/v) polycaprolactone (PCL) polymer solutions prepared with chloroform solvent. Porcine valvular interstitial cells were cultured in the scaffolds for 14 d to investigate the effect of microfibers prepared with different PCL concentrations on the seeded cells. Further, fresh microfibrous scaffolds were implanted subcutaneously in a rat model for two months to investigate the effect of microfibers on infiltrated cells. Cell proliferation, and its morphologies, gene expression and deposition of different extracellular matrix proteins in the in vitro study were characterized. During the in vivo study, we characterized cell infiltration, and myofibroblast and M1/M2 phenotypes expression of the infiltrated cells. Among different PCL concentrations, microfibrous scaffolds from 14% solution were suitable for heart valve tissue engineering for their sufficient pore size and low but adequate tensile properties, which promoted cell adhesion to and proliferation in the scaffolds, and effective gene expression and extracellular matrix deposition by the cells in vitro. They also encouraged the cells in vivo for their infiltration and effective gene expression, including M2 phenotype expression.

P5990In vivo tracking of long-term survival of xenogeneic porcine mesenchymal stem cells seeded on tissue-engineered heart valve implanted in sheep

Abstract Background Long-term survival of xenogeneic transplanted cells in adults requires strong immunosuppression and/or encapsulation of the cells to achieve peripheral transplant tolerance. Purpose The aim of our project was to seed decellularized tissue engineered heart valves (TEHV) with xenogeneic (porcine) mesenchymal stem cells (pMSCs) transfected transiently (Lipofectamine) with a positron emission tomography (PET)-reporter gene (pMSC-PETr), followed by implantation as pulmonary valve replacement into sheep without immunosuppression. The fate of the seeded pMSC-PETr was tracked via serial in-vivo non-invasive PET-computed tomography (PET-CT). Methods Static cultivation of TEHV scaffold led to successful ingrowth of the pMSC-PETr. For enabling quantitative assessment of viable pMSC-PETr in the TEHV scaffold after in vivo implantation, vials containing 5x104, 2x105, and 4x105 pMSC-PETr were in vitro mixed with the [18F]-FHBG PET tracer for 1 hr, then the non-bound tracer was washed out and vials were in vitro PET-CT imaged, giving reference values. TEHV-pMSC-PETr were then implanted percutaneously into the pulmonary valve position of sheep (n=4) under general anesthesia, while an additional sheep with no valve implantation served as a control. Ten mCi of [18F]-FHBGPET radiotracer was produced for each procedure and serial PET-CT imaging of the sheep was performed at 3 hr, 24 hr, 2 or 3 weeks, and 5 and 6 months after valve implantation. The study followed the Principles of laboratory animal care. Results PET-CT of vials containing increasing number of pMSC-PETr showed dose-dependent tracer uptake in the transfected cells in vitro (Figure). PET-CT images of the sheep 3 hr after implantation of the TEHV-pMSC-PETr showed a clear signal of transfected cells, with a mean estimated number of viable pMSC-PETr of 5.18±1.19x106. No meaningful decrease of the amount of living cells occurred at 24 hr or 2 or 3 weeks. Interestingly, 5- and 6-month follow-up PET-CT images showed clear in vivo and in vitro (after explantation) PET signals of the pMSC-PETr on TEHV, indicating spontaneous stable transfection of the PET reporter plasmid (insertional mutagenesis). Histology confirmed the survival of the pMSC-PETr at 5 and 6-month after xenogeneic transplantation. Merged immunohistochemistry and fluorescence imaging of anti-pig SLA I and anti-sheep MHC I antibodies and PET-reporter gene (HSV1-tk) suggested in vivo inter-species lateral jump gene transfer between pig MSCs and host sheep cells. Figure 1 Conclusions This is the first report on serial non-invasive in vivo tracking of long-term survival of xenogeneic pMSCs-PETr seeded on TEHVs and percutaneously implanted into the pulmonary position of sheep. Long-term follow-up revealed spontaneous stable transfection of the plasmid PET-reporter gene, which suggests the risk of insertional mutagenesis induced by the plasmid (transposon), and PET-reporter gene shuttle from xenogeneic pig MSCs to sheep cells. Acknowledgement/Funding LifeValve EU project (grant number: 242008)

RESVERATROL SIGNIFICANTLY ATTENUATES CELL MEDIATED IMMUNE REJECTION AGAINST XENOGENEIC BOVINE PERICARDIUM

Resveratrol is a major bioactive phenol found in red wine and red grapes that has been shown to reduce T cell activation and proliferation through inhibition of protein kinase B (PKB/Akt) and mTOR pathways. Recent studies have shown that humoral and cell-mediated immune reactions cause structural valve deterioration (SVD) in xenograft valves constructed out of bovine pericardium. Thus, tissue engineered heart valves (TEHV) which involve the process of decellularizing bovine pericardium have been developed to reduce xenoreactive immune response. Our study examines whether resveratrol could further reduce cell-mediated immune rejection against xenograft bovine pericardium thereby serving as a potential adjuvant therapy to TEHV. Human peripheral blood mononuclear cells (PBMC) were isolated by Ficoll-Paque gradient centrifugation and resuspended in RPMI 1640 complete medium containing 10% human serum, 2mM L-glutamine, 50 IU penicillin/ml, and 50 ml streptomycin/ml. The cells were further split into a resveratrol-treated group (50μM/ml) and a vehicle-treated group containing ethanol (50μM/ml) and cultured overnight (18hrs) in a 37C 5% CO2 incubator. 2ml of the complete medium from each group containing 1 X 10ˆ6 PBMC cells were then aliquoted into 12-well cell culturing plate with each well containing either native bovine pericardium, decellularized bovine pericardium, allograft pericardium, autograft pericardium, or no pericardium. The exposed culture media were then collected for ELISA analysis after 1 and 3 days. Tumor necrosis factor-a (TNF-a), chiefly produced by macrophages in cell-mediated immunity, were measured. Resveratrol-treated cells showed a significant reduction in all of the tissue exposure types in comparison to vehicle-treated controls at both 1 and 3 days (P < 0.05). Additionally, both vehicle control and resveratrol-treated groups at each time points generated the highest TNF-a concentration with native bovine pericardium exposure followed by the decellularized bovine pericardium, autograft pericardium, allograft pericardium, and no tissue. Resveratrol significantly attenuates cell-mediated immune rejection against xenogenic bovine pericardium exposure to an extent comparable to allograft and autograft human pericardium exposures. Therefore, resveratrol may serve as effective adjuvant therapy in patients receiving TEHV replacements to further decrease the xenogenic immune shown to cause SVD.

P4739Novel tissue-engineered heart valve without any foreign materials

Abstract Background We are developing a novel autologous tissue-engineered heart valve with a unique in-body tissue engineering. This is expected to be a viable bioprosthesis keeping better biocompatibility. Purpose We developed a conduit-type valve without any foreign materials and tested the feasibility and long-term availability in large animal experiments. Methods We created plastic molds for Biovalves with 3D printer easily and quickly considering the recipient character. We embedded them in the subcutaneous spaces of adult goats about 2 months. After extracting the molds with the tissue en-block and removing the plastic molds only, Biovalve with tri-leaflets similar to those of the native valves were constituted from completely autologous connective tissues and fibroblasts. Total 21 conduit-type Biovalves were implanted in the apico-aortic bypass or the pulmonary artery of goats, (8 and 13, respectively). No anticoagurants were used after implantation. Results The valves were successfully implanted and showed smooth movement of the leaflets with a little regurgitation in angiogram, and the maximum duration reached to 3 years 7 months. Histological examination of the Biovalves showed the autologous cells covering the laminar surface of the valve leaflets as the endothelium and also getting inside to construct characteristic tissues like native leaflets. Conclusion The valves have a potential to be used for viable bioprosthetic valves and to keep better function and biocompatibility longer than current ones.

In vivo remodeling of a 3D-Bioprinted tissue engineered heart valve scaffold

ObjectiveTo evaluate the recellularization potential of a bioprinted aortic heart valve scaffold printed with highly concentrated Type I collagen hydrogel (Lifeink® 200) and MSCs. Materials and methodsA suspension of rat mesenchymal stem cells (MSCs) was mixed with Lifeink® 200 and was 3D-printed into gelatin support gel to produce disk scaffolds which were subsequently implanted subcutaneously in Sprague-Dawley rats for 2, 4, 8, and 12 weeks. The biomechanical properties of the scaffolds were evaluated by uniaxial tensile testing and cell infiltration and inflammation assessed via immunohistochemistry (IHC) and histological staining. ResultsThere was an average decrease in both UTS and tensile modulus from 2 to 4 weeks followed by an increase between 4 to 8 weeks and a plateau from 8 to 12 weeks. IHC showed a continued expression of alpha smooth muscle actin and vimentin biomarkers throughout the study demonstrating continued presence of interstitial-like and fibroblast-like cells. Additionally, there was also an increase of elastin at each time point. ConclusionThe profile of the stress-strain curves of the bioprinted aortic heart valve scaffolds indicated that the scaffold transitioned through phases of resorption, synthesis, stabilization, and ultimately, remodeling. This is supported by IHC and histology which showed favorable remodeling capacity demonstrating potential feasibility for a 3D printed heart valve.

Human cell-derived tissue-engineered heart valve with integrated Valsalva sinuses: towards native-like transcatheter pulmonary valve replacements

Transcatheter valve replacement indication is currently being extended to younger and lower-risk patients. However, transcatheter prostheses are still based on glutaraldehyde-fixed xenogeneic materials. Hence, they are prone to calcification and long-term structural degeneration, which are particularly accelerated in younger patients. Tissue-engineered heart valves based on decellularized in vitro grown tissue-engineered matrices (TEM) have been suggested as a valid alternative to currently used bioprostheses, showing good performance and remodeling capacity as transcatheter pulmonary valve replacement (TPVR) in sheep. Here, we first describe the in vitro development of human cell-derived TEM (hTEM) and their application as tissue-engineered sinus valves (hTESVs), endowed with Valsalva sinuses for TPVR. The hTEM and hTESVs were systematically characterized in vitro by histology, immunofluorescence, and biochemical analyses, before they were evaluated in a pulse duplicator system under physiological pulmonary pressure conditions. Thereafter, transapical delivery of hTESVs was tested for feasibility and safety in a translational sheep model, achieving good valve performance and early cellular infiltration. This study demonstrates the principal feasibility of clinically relevant hTEM to manufacture hTESVs for TPVR.

Trilayer scaffold with cardiosphere‐derived cells for heart valve tissue engineering

Natural polymers collagen, glycosaminoglycans, and elastin are promising candidate materials for heart valve tissue engineering scaffolds. This work produced trilayer scaffolds that resembled the layered structures of the extracellular matrices of native heart valves. The scaffolds showed anisotropic bending moduli (in both dry and hydrated statuses) depending on the loading directions (lower in the With Curvature direction than in the Against Curvature direction), which mimicked the characteristic behavior of the native heart valves. The interactions between cardiosphere-derived cells and the scaffolds were characterized by multiphoton microscopy, and relatively similar cell distributions were observed on different layers (a cell density of 3,000-4,000 mm-3 and a migration depth of 0.3-0.4 mm). The trilayer scaffold has represented a forwarding step from the previous studies, in attempting to better replicate a native heart valve structurally, mechanically, and biologically.