According to the Centers for Disease Control and Prevention (CDC), over 40,000 infants are born with a congenital heart defect annually in the United States.1 Congenital heart defect entails a vast number of heart problems, including septal defects, valve deformities, or any change that leads to physiological malformations. Approximately one-third of these defects involve valves in the heart, including valvular stenosis (narrowing of the blood flow between chambers), regurgitation (unproper closure of heart valve, allowing blood to flow backward), atresia (lack of the valve) or valve dysplasia (thickened, malformed leaflets and/or chordae, causing stenosis and regurgitation).2,3 As science advances, new methods for treating valve defects have emerged. Even with advancements in technology, children with congenital valve dysfunctions often require multiple surgical interventions throughout their lives due to the lack of technology that creates a valve able to develop along with the child's development. Thus, while child grows up, frequent new interventions will be needed to implant a new suitable artificial valve, and every time a new surgical procedure occurs, it carries risks and complications.4

Depending on the type of valve defect, a suitable surgical approach will be applied. For many patients, valvular repair, which focuses on restoring the valve’s function, may be a suitable option.5 Valvular repair has shown a significant advantage, reducing the likelihood of reintervention within the next 10 years by approximately 86% ± 5%.5 While it can contribute to preserving the valve, allowing it to grow with the child, decreasing the risk of long-term complications. Despite advancements in valvular repair, risks such as residual regurgitation and recurrent stenosis still persist. In some cases, surgeons may perform a reconstruction of the surrounding area to restore the valve's physiological shape. Some techniques involve adjusting the aortic root, ventricular walls, or the valve rings, all done to improve function and potentially combat the need for further procedures.6 When valve repair and reconstruction are not sufficient, valve replacement becomes the next consideration.

Valve replacement is a surgical procedure in which a dysfunctional valve is entirely removed, or pushed toward the valvular annulus in transcatheter implantation, and replaced with a prosthetic valve.7 The replacement can be done using a mechanical valve (constructed from durable materials such as titanium or carbon), or a tissue valve, including xenografts (from animal tissue), homografts (from deceased human donors) which is applied in Partial Heart Transplant, or autograft like in the Ross procedure. Several techniques can facilitate successful valve replacement, some of which incorporate new developments designed to bypass the difficulties associated with the valve's limited growth.

The Ross procedure is a complex surgical technique in which the patient's native pulmonary valve is transplanted into the aortic position, and the pulmonary valve is subsequently replaced with a homograft or xenograft conduit.8 This operation offers several physiological advantages, including excellent hemodynamic performance, resistance to thrombosis, and the potential for somatic growth, making it especially valuable in pediatric and young adult populations.8 Long-term studies have demonstrated favorable outcomes, with survival rates approaching those of the general population and reduced risks of thromboembolic events compared to mechanical valves.9,10 However, the procedure is technically demanding and involves creating a two-valve disease scenario, which can lead to potential reintervention, particularly in the right ventricular outflow tract. Despite these limitations, the Ross procedure remains a valuable option for selecting patients, particularly those with contraindications to lifelong anticoagulation or a strong preference for maintaining native- like valve function.11

Partial Heart Transplantation (PHT) is an innovative surgical procedure in which only a portion of a donor heart—typically a functional heart valve or root complex—is transplanted into the recipient, rather than the entire organ. This technique offers a biologically active, living tissue graft with potential for growth, repair, and physiological integration, which is particularly advantageous in pediatric patients with congenital heart valve diseases. Unlike conventional valve replacement with prosthetic valves, PHT has shown the potential to grow with the patient, reducing the burden of repeated interventions.12

While each type of procedure offers specific benefits and can improve patient outcomes, prosthetic valve replacement remains the most prevalent treatment.13 In adult patients, valve replacement typically results in symptomatic relief and improved quality of life. However, in pediatric populations, heart valve replacement poses unique challenges. As prosthetic valves do not grow with the patient, children frequently require multiple reoperations over time to accommodate somatic growth.14 These repeated surgical interventions increase the risk of both morbidity and mortality and may also compromise long-term cardiac function and overall quality of life.15 Additionally, patients with mechanical valves require lifelong anticoagulation therapy, which elevates the risk of serious complications, including hemorrhagic and thromboembolic events.16 Given these limitations, this review focuses on recent advancements in tissue valve replacement, aiming to identify the most promising strategies capable of accommodating patient growth and improving long-term outcomes in pediatric populations.

Tissue Engineering: General Principles

Tissue engineering is an interdisciplinary field that merges principles of biomedical sciences, materials engineering, and regenerative medicine to develop functional tissues and organs capable of restoring or replacing damaged biological structures.16 In congenital heart disease, Heart Valve Tissue Engineering (HVTE) represents a promising frontier focused on creating living, functional heart valves that can grow, repair, and remodel alongside a patient’s growth and development.17 This field of research is needed for pediatric patients, as prosthetic valves fail to accommodate somatic growth, necessitating repeated interventions.

Successful HVTE relies on three core components: stem cells, bioactive molecules, and scaffolds.18 Stem cells can be derived from various tissues, including bone marrow, umbilical cord, adipose tissue, and even dental pulp. These cells may originate from either autologous or allogeneic sources.19 In autologous transplantation, the stem cells are harvested from the same individual who will receive the engineered tissue, offering better compatibility and significantly reducing the risk of immune rejection.20–22 This contrasts with allogeneic sources, which involve cells from a donor of the same species, xenogeneic sources, where cells are obtained from a donor of a different species, and emerging alternatives such as bioengineered/printable tissues.23

Allogeneic stem cell derivatives offer several advantages, including greater availability, batch-to-batch consistency, and the potential for extensive laboratory manipulation and quality control. These characteristics make them particularly appealing for off-the-shelf regenerative therapies and scalable clinical applications. However, because these cells originate from a different source, they are more likely to provoke an immune response in the host. This immunological recognition can lead to graft rejection, chronic inflammation, or impaired tissue integration. As a result, recipients often require prolonged immunosuppressive therapy to reduce the risk of rejection and maintain graft viability.24– 27

The second important component of HVTE is the structural formation of the scaffolds. Scaffolds are 3-dimensional structures designed to mimic the extracellular matrix (ECM).28 In tissue engineering, scaffolds provide physical support, shape, and biomechanical cues that facilitate cell adhesion, giving the space and enabling the formation of new tissue. Scaffolds can be made of a range of biomaterials.29 Natural materials – such as collagen, gelatin, and fibrin – create excellent biocompatibility but have less stable and weaker mechanical properties. Synthetic materials – such as Polyglycolic acid (PGA), Polylactic acid (PLA), Polycaprolactone (PCL), and PEG-based hydrogels – provide controlled mechanical properties, degradation rate, and reproductivity, while also decreasing the flexibility of the tissue. A widely adopted approach is to engineer hybrid scaffolds that integrate natural and synthetic materials, thereby leveraging the biocompatibility of the natural with the mechanical strength and tunability of the synthetic tissue.30 One persistent challenge HVTE faces is the difficulty in achieving consistent, patient-specific remodeling. Recent advances in biomaterials – such as electrospinning, 3D bioprinting, and nanostructuring – have enabled the creation of scaffolds that more closely mimic the structure and mechanical properties of natural heart valve tissue.31,32

The final component of HVTE is the incorporation of bioactive molecules – soluble or immobilized biological signals that guide cell growth and tissue development.33 These include extracellular matrix proteins, growth factors, cytokines, and other signaling ligands. By promoting cell attachment, proliferation, and differentiation, these bioactive molecules simplify tissue formation and the body's response. These components, when combined, will assist the cells in mimicking the mechanical and biochemical properties of native heart valves, thereby creating a copy of the latter.34

HVTE typically follows one of two main strategies: in vitro or in situ engineering. In in vitro approaches, scaffolds are seeded with cells and cultured under controlled laboratory conditions – often using bioreactors – to promote tissue formation prior to implantation. This method enables precise regulation of environmental factors such as nutrient supply, mechanical stimulation, and growth factor exposure. In contrast, in situ engineering involves the implantation of acellular scaffolds directly into the patient. These scaffolds are designed to recruit host cells and harness the body’s natural regenerative capacity to initiate tissue remodeling and integration at the site of implantation. Each approach offers unique advantages and challenges in terms of cell sourcing, immune response, and long-term

functionality. The in-situ approach is gaining momentum due to its logistical advantages, including reduced production costs and simple manufacturing, while also offering the potential for decreased fibrotic and immune response complications.35 The success of this approach depends on the valve's ability to withstand physiological hemodynamic pressure at the time of implantation and to support the formation of viable, immune-regulated tissue that can integrate, remodel, and function effectively over time.35

Considering the multifaceted nature of heart valve tissue engineering (HVTE), two of the most significant challenges remain minimizing post-implantation inflammatory responses and achieving long-term durability of the constructed tissues.36 Future advancements in this field are likely to be driven by the integration of immune-modulatory biomaterials, patient-specific stem cell therapies, and dynamic bioreactor systems that more accurately replicate physiological conditions during tissue development. These innovations aim to enhance tissue maturation, vascularization, and immune tolerance.37 Notably, ongoing research is increasingly focused on pediatric applications, where the need is especially urgent for valve replacements that are not only biocompatible and durable but also capable of growing and remodeling in concert with the child’s development.

IN VITRO STUDIES

In vitro studies are characterized as experiments conducted outside a living organism, typically in a controlled laboratory setting, such as a petri dish, test tube, or culture flask. It plays a crucial role in helping researchers understand the cellular and molecular mechanisms behind how implanted valves interact with the body and elicit their immune responses. These lab-based systems, such as immune cell-scaffold interaction studies, enable the testing of different materials and designs before progressing to animal or clinical studies. The immune response to engineered heart valves is a crucial factor in predicting their long-term function and integration within the body. If not well controlled, this response can lead to inflammation, tissue damage, or even graft failure. Understanding these potential outcomes is important for creating heart valves that are safe, long-lasting, and more suitable for patients, especially children.

Recent advances in valve tissue engineering have highlighted the importance of immune- responsive scaffold designs, leading to increased interest in in vitro studies that aim to replicate the complex cellular environments to which heart valves are exposed after implantation. These models serve as a good source for evaluating how scaffold materials interact with immune and vascular cells, supporting the development of next-generation valves that can integrate, remodel, and function in dynamic in vivo environments.38 These models also show the importance of balancing mechanical properties with biological compatibility to create functional heart valves that can integrate with the host tissue and withstand the dynamic forces of the cardiovascular system.39

A review published in the Tissue Engineering Journal in 2020 explains that when immune cells, such as macrophages and dendritic cells, are exposed to decellularized cardiac tissue, they recognize damage-associated molecular patterns (DAMPs) present in the biomaterial and initiate an inflammatory reaction and production of cytokines.40 During implantation, a tuned equilibrium between pro-inflammatory and anti-inflammatory cytokines is critical for success. Initially, the host immune system mounts an acute pro-inflammatory response (e.g., release of IL1β, TNFα, IL6) to clear debris, recruit immune cells, and trigger tissue remodeling.41,42 However, if this response is excessive or persists, as is common in foreign body reactions, it can result in chronic inflammation, fibrosis, and impaired integration. Consequently, a switch toward anti-inflammatory mediators (such as IL-10, TGFβ) is necessary. These cytokines will suppress further pro-inflammatory signaling while also promoting tissue repair, angiogenesis, and scaffold remodeling. New strategies in scaffold design intentionally adapt this cytokine balance by incorporating immunomodulatory cues, such as mesenchymal stromal cells (MSCs), bioactive coatings, or timed drug release, to promote a constructive M1-to-M2 macrophage shift and prevent detrimental fibrotic encapsulation.43 Thus, maintaining this cytokine balance is not merely biological housekeeping—it’s foundational to achieving functional integration, long-term graft viability, and regenerative outcomes post-implantation.44

The development of in vitro experiments allows for the controlled assessment of cellular behavior, particularly the interactions between immune cells and progenitor or stem cells, prior to in vivo implantation. These systems help isolate key factors—such as scaffold composition, surface properties, and cytokine signaling—that influence cell adhesion, activation, differentiation, and inflammatory responses. By modeling specific aspects of the post-implantation environment, in vitro studies provide valuable insights into how biomaterials may perform in vivo and support the refinement of scaffold designs before progressing to preclinical or clinical testing.

Another important area of in vitro research involves the design of scaffold structures, with recent advancements in nanoscale architectures showing significant promise for enhancing tissue regeneration and integration. The new Melt ElectroWriting (MEW) and electrospinning technologies, as published by Saidy et al. (2019), demonstrate that the fabrication of serpentine MEW scaffolds exhibits defined structural changes that mimic the mechanical behavior of native heart valve leaflets.45,46 By adjusting factors such as the spacing between circumferential and radial fibers, the degree of curvature, and the number of layers, researchers have been able to produce scaffolds with J-shaped stress–strain curves, directional stiffness (anisotropy), and viscoelastic properties similar to those found in natural valve tissue.

The use of Nanofibrous Scaffolds, biodegradable nanofiber polymers, allows for the creation of materials that replicate the extracellular matrix components. These scaffolds aim to provide structural support while facilitating cellular infiltration and tissue formation.47 While further research is still needed, studies have shown that carbon fibers support the adhesion of human adipose-derived stem cells (hADSCs) without triggering their differentiation.48 Additionally, the fibers demonstrated sufficient flexibility to be integrated into a functional in vitro tissue-engineered heart valve without impairing cusp motion.48 These findings suggest that carbon fiber–based scaffolds represent a promising strategy for creating heart valves that combine durable and load-bearing mechanical properties with the ability to support tissue regeneration, potentially improving outcomes for patients requiring valve replacement.48 However, further studies are necessary to fully evaluate the efficacy and long-term potential of carbon fiber–based approaches in tissue-engineered valve replacement.

ANIMAL STUDIES

Preclinical animal studies have been instrumental in advancing the understanding of tissue- engineered heart valve replacements, developing strong knowledge of host immune responses, and conducting research trials. Studies using ovine, porcine, and non-human primate models have demonstrated that decellularized xenogeneic scaffolds produce a variety of immune responses, which are influenced mainly by the graft’s tissue origin and the level of residual antigen remaining after processing.49 Work involving biologic scaffolds derived from pig tissue has shown early infiltration of macrophages and T cells, accompanied by elevated anti-Gal antibody titers and complement activation, which often correlate with early calcification and structural valve degeneration.50 In contrast, decellularized allograft scaffolds implanted in large-animal models showed an attenuated cellular infiltration, reduction in cytokine expression, and more favorable remodeling dynamics.51 Host-derived endothelial and interstitial cell repopulation of decellularized scaffolds has been consistently observed in immuno-tolerant large-animal models, highlighting the potential for in situ regeneration and long-term functionality of bioengineered heart valves.52 Unseeded decellularized porcine valve matrices have been shown to promote platelet adhesion and aggregation, both in vitro and in vivo—an effect that is markedly reduced with endothelial cell seeding, suggesting that thrombogenicity can be mitigated through bioactive surface modification.53 In ovine models, implantation of decellularized porcine valves elicited an early humoral immune response, characterized by increased levels of IgM, IgG, and complement component C1. Additional assays demonstrate that decellularized human allograft scaffolds attract significantly fewer monocytes than porcine equivalents, indicating species-specific antigen remnants as key drivers of the monocytic chemotactic response.54 Furthermore, seeding acellular porcine pericardial scaffolds with MSCs enhances host-side recellularization and reduces inflammation compared to unseeded controls.55 Together, these studies underscore the importance of factors such as effective decellularization, scaffold source, and recellularization methods in shaping the immune response, particularly thromboinflammatory reactions, antibody activity, and tissue regeneration. These insights are crucial for enhancing the design of scaffolds to improve the long-term durability and immune compatibility of engineered heart valves.

Clinical Studies

While great progress has been made in preclinical animal models, clinical studies involving children have not yet undergone comprehensive testing and remain limited. Pediatric patients present unique challenges due to growth, immune variability, and long-term durability requirements. A few early-phase clinical efforts, such as those involving decellularized allografts or in situ tissue engineering, have shown promising results.56–58 The use of decellularized pulmonary homograft (DPH) in infants, for example, has attracted increasing clinical interest due to its potential to reduce graft immunogenicity and improve durability.59 In early childhood – particularly infancy – the immune system is highly reactive, raising important considerations for graft-host interactions. Several clinical studies have investigated the immunological performance of these grafts in this sensitive population, focusing on both cellular and humoral responses.60

Cebotari et al. (2011) reported on early use of DPH in children and infants. Their findings reinforced the idea that fresh decellularized grafts reduce inflammation and early degeneration. While limited by short-term follow-up in the infant subgroup, the study reported no immune-mediated graft failures and suggested that decellularization may favor a more tolerant host environment during early immune development.61 Building on earlier findings, a 2024 case report provided histological insight into DPH remodeling in an infant patient. The explanted graft showed directional recellularization, mainly along the ventricular side of the valve leaflets. Although the conduction wall exhibited limited cellular repopulation, there was no evidence of calcification, thrombosis, or immune-mediated injury. These results support the immunological safety of DPHs in very young patients and highlight their potential for selective in vivo integration, while also underscoring areas where recellularization remains incomplete.62

In addition, Burch et al. (2010) compared decellularized and standard cryopreserved human pulmonary homografts in pediatric right ventricular outflow tract reconstructions.57 They observed a modest reduction in peak valve gradients—significant in smaller conduits—and a nonsignificant trend toward fewer reinterventions among recipients of decellularized grafts, with no difference in valve insufficiency between groups. Importantly, antibody panel reactive activity (PRA) remained stable in the decellularized group post-surgery, suggesting reduced humoral response. These findings support the reduction of immunogenic response in decellularized grafts while maintaining functional performance, reinforcing the possibility of a more immune-compatible option in pediatric cardiac surgery.58,63–66

Long-term follow-up from the ESPOIR Pediatric Registry—comprising over 300 patients— confirmed excellent decellularized pulmonary homograft performance, with ~97% freedom from explantation or reintervention and very low adverse event rates over 5–15 years. While the primary report did not provide infant-specific or immunologic subgroup data, other studies (e.g., antibody binding assays) have reported no significant sensitization or rejection, supporting the immunologic safety and anatomical effectiveness of DPHs in pediatric populations; however, detailed infant data remain limited.59 These findings nonetheless highlight the potential of DPH to meet the unique immunologic and anatomical demands of infant patients while reducing the risk of sensitization that could complicate future interventions such as transplantation.

While decellularized pulmonary homografts (DPHs) are supported by robust clinical data, other forms of tissue-engineered heart valves (TEHVs) are still very much in the early clinical stage and require extensive validation before widespread adoption. For example, small- scale in situ TEHV trials have shown that decellularized pulmonary homograft scaffolds reseeded with autologous endothelial progenitor cells were successfully implanted in pediatric patients (ages 11 and 13) in 2002, demonstrating somatic growth and improved valve function over 3.5 years.67 More recently, first-in-human clinical trials have tested electrospun, bioresorbable polymeric pulmonary conduits (e.g., Xeltis) in children, showing favorable hemodynamics at 2 years but significant regurgitation and no proven adaptive growth.68 While these findings are encouraging, overall clinical evidence remains limited.

Collectively, these data underscore that while DPHs currently have the strongest clinical foundation – especially due to ESPOIR and registry data – alternative TEHV approaches still need larger studies with longer follow-up, particularly focusing on infant populations, immunogenicity, and true growth potential. Continued clinical research is essential to determine whether these next‑generation strategies can reliably meet the complex demands of congenital valve replacement.

FUTURE DIRECTIONS

Pediatric heart valve replacement remains a major clinical challenge due to the static nature of treatment options. The inability of prosthetic heart valves to accommodate somatic growth in children contributes to a high rate of reoperations over time, with nearly 30% requiring reintervention by 20 years and a 20-year survival rate of only 81.9%, underscoring the long-term risks, including mortality, with repeated surgical interventions.69 Therefore, there is an urgent need for new developments in this specific field. The future of pediatric heart valve replacement hinges on developing dynamic, biologically integrated valves that grow with the child, thereby reducing the burden of repeated surgeries. Progress will depend on the synergistic integration of bioresorbable scaffolds, innovative biomaterials, and advanced cell recruitment strategies to create valves that not only mimic the properties of native tissue but also adapt over time.

Emerging technologies, such as hybrid polymers, nanoengineering, and personalized 3D printing, are opening up new possibilities for creating heart valves that integrate with tissue remodeling. To better predict how these materials will perform in young patients, improving preclinical models—particularly juvenile animal studies and organ-on-chip systems—will be vital for capturing the nuances of pediatric physiology and immune response. At the same time, developing clinical trials will generate the real-world data needed to inform the development of next-generation therapies. Looking ahead, the development of immune- instructive biomaterials tailored to each patient’s unique biology may help reduce complications and support long-term function. Bridging the gap between lab-based innovation and clinical reality will require ongoing investment in translational research and strong public-private partnerships, ultimately bringing us closer to durable, adaptive valve solutions for children in need.

1. About Congenital Heart Defects. Congenital Heart Defects (CHDs). March 18, 2025 [cited 2025 Jul 11]. Available from: https://www.cdc.gov/heart-defects/about/index.html
2. Allan L. Fetal cardiac scanning today. Prenat Diagn. 2010;30(7):639–43.
3. Hoffman JIE, Kaplan S. The incidence of congenital heart disease. J Am Coll Cardiol. 2002;39(12):1890–900.
4. Nguyen SN, Vinogradsky AV, Ferrari G, et al. Pitfalls and future directions of contemporary pediatric valve surgery: the case for living valve substitutes. Curr Pediatr Rep. 2023;11(4):180–92.
5. Tweddell JS, Pelech AN, Jaquiss RDB, et al. Aortic valve repair. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2005:112–21.
6. Arjomandi Rad A, Zubarevich A, Osswald A, et al. The surgical treatment of infective endocarditis: a comprehensive review. Diagnostics (Basel). 2024;14(5):464.
7. Cleveland Clinic. Heart valve replacement: types, procedure & recovery [Internet]. [cited 2025 Jul 13]. Available from: https://my.clevelandclinic.org/health/treatments/23966-heart-valve-replacement
8. Ross Procedure in adults for cardiologists and cardiac surgeons: JACC state-of-the-art review [Internet]. [cited 2025 Jul 13]. Available from: https://www.jacc.org/doi/10.1016/j.jacc.2018.08.2200
9. Aboud A, Charitos EI, Fujita B, et al. Long-term outcomes of patients undergoing the Ross procedure. J Am Coll Cardiol. 2021;77(11):1412–22.
10. Ryan WH, Squiers JJ, Harrington KB, et al. Long-term outcomes of the Ross procedure in adults. Ann Cardiothorac Surg. 2021;10(4):499–508.
11. Mazine A, Rocha RV, El-Hamamsy I, et al. Ross procedure vs mechanical aortic valve replacement in adults: a systematic review and meta-analysis. JAMA Cardiol. 2018;3(10):978–87.
12. AHA Journals. Partial heart transplantation: early experience with pediatric heart valve replacements that grow [Internet]. [cited 2025 Jul 13]. Available from: https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.124.072626
13. Pibarot P, Dumesnil JG. Prosthetic heart valves. Circulation. 2009;119(7):1034–48.
14. Nguyen SN, Vinogradsky AV, Ferrari G, et al. Pitfalls and future directions of contemporary pediatric valve surgery: the case for living valve substitutes. Curr Pediatr Rep. 2023;11(4):180–92.
15. Jones JM, O’Kane H, Gladstone DJ, et al. Repeat heart valve surgery: risk factors for operative mortality. J Thorac Cardiovasc Surg. 2001;122(5):913–8.
16. MacIsaac S, Jaffer IH, Belley-Côté EP, et al. A historical review and critical analysis of anticoagulation therapy following mechanical valve replacement. Circulation. 2019;140(23):1933–42.
17. Ciolacu DE, Nicu R, Ciolacu F. Natural polymers in heart valve tissue engineering: strategies, advances and challenges. Biomedicines. 2022;10(5):1095.
18. Sun L, Wang Y, Xu D, Zhao Y. Emerging technologies for cardiac tissue engineering and artificial hearts. Smart Med. 2023;2(1):e20220040.
19. Li C, Zhao H, Cheng L, Wang B. Allogeneic vs autologous mesenchymal stem/stromal cells in their medication practice. Cell Biosci. 2021;11:187.
20. Augustine R, Dan P, Hasan A, et al. Stem cell-based approaches in cardiac tissue engineering: controlling the microenvironment for autologous cells. Biomed Pharmacother. 2021;138:111425.
21. Povsic TJ, Gersh BJ. Stem cells in cardiovascular diseases: 30,000-foot view. Cells. 2021;10(3):600.
22. Champlin R. Selection of autologous or allogeneic transplantation. In: Holland-Frei Cancer Medicine. 6th ed. BC Decker; 2003 [cited 2025 Jul 13]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK12844/
23. Pitkin Z. New phase of growth for xenogeneic-based bioartificial organs. Int J Mol Sci. 2016;17(9):1593.
24. Núñez García A, Sanz-Ruiz R, Fernández Santos ME, et al. “Second-generation” stem cells for cardiac repair. World J Stem Cells. 2015;7(2):352–67.
25. Gupta M, Bindra MS. Hyaline globules in fine-needle aspiration smears of salivary gland neoplasms. BMJ Case Rep. 2015;2015:bcr2014208114.
26. Shobayashi Y, Tanoue T, Tateshima S, et al. Mechanical design of an intracranial stent for treating cerebral aneurysms. Med Eng Phys. 2010;32(9):1015–24.
27. Sipp D, Robey PG, Turner L. Clear up this stem-cell mess. Nature. 2018;561(7724):455–7.
28. Jana S, Tefft BJ, Spoon DB, Simari RD. Scaffolds for tissue engineering of cardiac valves. Acta Biomater. 2014;10(7):2877–93.
29. Lu T, Li Y, Chen T. Techniques for fabrication and construction of three-dimensional scaffolds for tissue engineering. Int J Nanomedicine. 2013;8:337–50.
30. Nikolova MP, Chavali MS. Recent advances in biomaterials for 3D scaffolds: a review. Bioact Mater. 2019;4:271–92.
31. Wu CA, Zhu Y, Woo YJ. Advances in 3D bioprinting: techniques, applications, and future directions for cardiac tissue engineering. Bioengineering. 2023;10(7):842.
32. Percival KM, Paul V, Husseini GA. Recent advancements in bone tissue engineering: integrating smart scaffold technologies and bio-responsive systems for enhanced regeneration. Int J Mol Sci. 2024;25(11):6012.
33. Rosso F, Marino G, Giordano A, et al. Smart materials as scaffolds for tissue engineering. J Cell Physiol. 2005;203(3):465–70.
34. Courtenay JC, Sharma RI, Scott JL. Recent advances in modified cellulose for tissue culture applications. Molecules. 2018;23(3):654.
35. Mirani B, Latifi N, Lecce M, et al. Biomaterials and biofabrication strategies for tissue-engineered heart valves. Matter. 2024;7(9):2896–940.
36. Kheradvar A, Groves EM, Dasi LP, et al. Emerging trends in heart valve engineering: Part I. Ann Biomed Eng. 2015;43(4):833–43.
37. D’Amore A, Luketich SK, Raffa GM, et al. Heart valve scaffold fabrication: bioinspired control of macro-scale morphology, mechanics and micro-structure. Biomaterials. 2018;150:25–37.
38. Cordoves EM, Vunjak-Novakovic G, Kalfa DM. Designing biocompatible tissue engineered heart valves in situ: JACC review topic of the week. J Am Coll Cardiol. 2023;81(10):994–1003.
39. Cordoves EM, Vunjak-Novakovic G, Kalfa DM. Designing biocompatible tissue engineered heart valves in situ. J Am Coll Cardiol. 2023;81(10):994–1003.
40. Differential activation of immune cells for genetically different decellularized cardiac tissues [Internet]. [cited 2025 Jul 14]. Available from: https://www.liebertpub.com/doi/10.1089/ten.tea.2020.0055
41. Nair A, Tang L. Influence of scaffold design on host immune and stem cell responses. Semin Immunol. 2017;29:62–71.
42. Farzamfar S, Garcia LM, Rahmani M, Bolduc S. Mesenchymal stem/stromal cells as architects of inflammatory harmony in tissue-engineered constructs. Bioengineering. 2024;11(5):494.
43. Corradetti, B., et al. "Immune Tuning Scaffold for the Local Induction of a Pro-Regenerative Environment." Scientific Reports, vol. 7, no. 1, 2017, p. 17030. https://doi.org/10.1038/s41598-017-16895-0.
44. Crupi, A., et al. "Inflammation in Tissue Engineering: The Janus Between Engraftment and Rejection." European Journal of Immunology, vol. 45, no. 12, 2015, pp. 3222–3236. https://doi.org/10.1002/eji.201545818.
45. Saidy, N.T., et al. "Biologically Inspired Scaffolds for Heart Valve Tissue Engineering via Melt Electrowriting." Small, 2019. https://doi.org/10.1002/smll.201900873.
46. Jin, T., and I. Stanciulescu. "Numerical Investigation of the Influence of Pattern Topology on the Mechanical Behavior of PEGDA Hydrogels." Acta Biomaterialia, vol. 49, 2017, pp. 247–259. https://doi.org/10.1016/j.actbio.2016.10.041.
47. Rubin, N., et al. "FGF10 Signaling Enhances Epicardial Cell Expansion During Neonatal Mouse Heart Repair." Journal of Cardiovascular Disease Diagnosis, vol. 1, no. 1, 2013, p. 101. https://doi.org/10.4172/2329-9517.1000101.
48. Tseng, Y.T., et al. "Biocompatibility and Application of Carbon Fibers in Heart Valve Tissue Engineering." Frontiers in Cardiovascular Medicine, vol. 8, 2021. https://doi.org/10.3389/fcvm.2021.793898.
49. "Xenoantigenicity of Porcine Decellularized Valves." Journal of Cardiothoracic Surgery, https://cardiothoracicsurgery.biomedcentral.com/articles/10.1186/s13019-017-0621-5. Accessed 16 July 2025.
50. Park, C.S., et al. "Anti Alpha-Gal Immune Response Following Porcine Bioprosthesis Implantation in Children." Journal of Heart Valve Disease, vol. 19, no. 1, 2010, pp. 124–130.
51. "Decellularization Reduces Immunogenicity of Sheep Pulmonary Artery Vascular Patches." PubMed, https://pubmed.ncbi.nlm.nih.gov/20637475/. Accessed 16 July 2025.
52. "Recellularization of a Novel Off-the-Shelf Valve Following Xenogenic Implantation Into the Right Ventricular Outflow Tract." PubMed, https://pubmed.ncbi.nlm.nih.gov/28763463/. Accessed 16 July 2025.
53. "Thieme E-Journals - Thrombosis and Haemostasis / Abstract." Thieme Connect, https://www.thieme-connect.com/products/ejournals/abstract/10.1160/TH05-01-0025. Accessed 16 July 2025.
54. Rieder, E., et al. "Tissue Engineering of Heart Valves: Decellularized Porcine and Human Valve Scaffolds Differ Importantly in Residual Potential to Attract Monocytic Cells." Circulation, vol. 111, no. 21, 2005, pp. 2792–2797. https://doi.org/10.1161/CIRCULATIONAHA.104.473629.
55. "In Vivo Response of Acellular Porcine Pericardial for Tissue Engineered Transcatheter Aortic Valves." Scientific Reports, https://www.nature.com/articles/s41598-018-37550-2. Accessed 16 July 2025.
56. Hawkins, J.A., et al. "Immunogenicity of Decellularized Cryopreserved Allografts in Pediatric Cardiac Surgery: Comparison with Standard Cryopreserved Allografts." The Journal of Thoracic and Cardiovascular Surgery, vol. 126, no. 1, 2003, pp. 247–252. https://doi.org/10.1016/S0022-5223(03)00116-8.
57. Burch, P.T., et al. "Clinical Performance of Decellularized Cryopreserved Valved Allografts Compared with Standard Allografts in the Right Ventricular Outflow Tract." The Annals of Thoracic Surgery, vol. 90, no. 4, 2010, pp. 1301–1305; discussion 1306. https://doi.org/10.1016/j.athoracsur.2010.05.024.
58. Waqanivavalagi, S.W.F.R., et al. "Clinical Performance of Decellularized Heart Valves versus Standard Tissue Conduits: A Systematic Review and Meta-Analysis." Journal of Cardiothoracic Surgery, vol. 15, no. 1, 2020, p. 260. https://doi.org/10.1186/s13019-020-01292-y.
59. Bobylev, D., et al. "5-Year Results from the Prospective European Multi-Centre Study on Decellularized Homografts for Pulmonary Valve Replacement: ESPOIR Trial and ESPOIR Registry Data." European Journal of Cardio-Thoracic Surgery, vol. 62, no. 5, 2022, ezac219. https://doi.org/10.1093/ejcts/ezac219.
60. Neumann, A., et al. "Early Systemic Cellular Immune Response in Children and Young Adults Receiving Decellularized Fresh Allografts for Pulmonary Valve Replacement." Tissue Engineering Part A, vol. 20, no. 5-6, 2014, pp. 1003–1011. https://doi.org/10.1089/ten.TEA.2013.0316.
61. Cebotari, S., et al. "Use of Fresh Decellularized Allografts for Pulmonary Valve Replacement May Reduce the Reoperation Rate in Children and Young Adults." Circulation, vol. 124, no. 11_suppl_1, 2011, pp. S115–S123. https://doi.org/10.1161/CIRCULATIONAHA.110.012161.
62. Kugo, Y., et al. "Histological Analysis of a Decellularized Pulmonary Homograft Explanted From a Pediatric Patient." JACC: Case Reports, vol. 30, no. 2, 2025, p. 102806. https://doi.org/10.1016/j.jaccas.2024.102806.
63. "Matched Comparison of Decellularized Homografts and Bovine Jugular Vein Conduits for Pulmonary Valve Replacement in Congenital Heart Disease." Cell and Tissue Banking, https://link.springer.com/article/10.1007/s10561-023-10082-4. Accessed 16 July 2025.
64. Vafaee, T., et al. "Decellularization of Human Donor Aortic and Pulmonary Valved Conduits Using Low Concentration Sodium Dodecyl Sulfate." Journal of Tissue Engineering and Regenerative Medicine, vol. 12, no. 2, 2018, pp. e841–e853. https://doi.org/10.1002/term.2391.
65. da Costa, F.D.A., et al. "Decellularized Versus Standard Pulmonary Allografts in the Ross Procedure: Propensity-Matched Analysis." The Annals of Thoracic Surgery, vol. 105, no. 4, 2018, pp. 1205–1213. https://doi.org/10.1016/j.athoracsur.2017.09.057.
66. Huyan, Y., et al. "Application of Homograft Valved Conduit in Cardiac Surgery." Frontiers in Cardiovascular Medicine, vol. 8, 2021. https://doi.org/10.3389/fcvm.2021.740871.
67. Konsek, H., et al. "Growing Heart Valve Implants for Children." Journal of Cardiovascular Development and Disease, vol. 10, no. 4, 2023, p. 148. https://doi.org/10.3390/jcdd10040148.
68. Konsek, H., et al. Same as above.
69. "Long-Term Outcomes of Mechanical Aortic Valve Replacement in Children." ScienceDirect, https://www.sciencedirect.com/science/article/abs/pii/S1092912623000248. Accessed 16 July 2025.