Strategies for Development of Synthetic Heart Valve Tissue Engineering Scaffolds

A self-sacrificing anti-inflammatory coating promotes simultaneous cardiovascular repair and reendothelialization of implanted devices

During interventional surgeries of implantable cardiovascular devices in addressing cardiovascular diseases (CVD), the inevitable tissue damage will trigger host inflammation and vascular lumen injury, leading to delayed re-endothelization and intimal hyperplasia. Endowing cardiovascular implants with anti-inflammatory and endothelialization functions is conducive to the target site, offering significant tissue repair and regeneration benefits. Herein, inspired by the snake's molting process, a ShedWise device was developed by using the poly(propylene fumarate) polyurethane (PPFU) as the foundational material, which was clicked with hyperbranched polylysine (HBPL) and followed by conjugation with pro-endothelial functional Arg-Glu-Asp-Val peptide (REDV), and finally coated with a "self-sacrificing" layer having reactive oxygen species (ROS)-scavenging ability and degradability. During the acute inflammation in the initial stage of implantation, the ROS-responsive hyperbranched poly(acrylate-capped thioketone-containing ethylene glycol (HBPAK) coating effectively modulated the level of environmental inflammation and resisted initial protein adsorption, showcasing robust tissue protection. As the coating gradually "sacrificed", the exposed hyperbranched HBPL-REDV layer recruited specifically endothelial cells and promoted surface endothelialization. In a rat vascular injury model, the ShedWise demonstrated remarkable efficiency in reducing vascular restenosis, protecting the injured tissue, and fostering re-endothelization of the target site. This innovative design will introduce a novel strategy for surface engineering of cardiovascular implants and other medical devices.

Advances in Bacterial Cellulose-Based Scaffolds for Tissue Engineering: Review

Bacterial cellulose (BC) has emerged as a highly versatile and promising biomaterial in tissue engineering, with potential applications across skin, bone, cartilage, and vascular regeneration. Its exceptional properties like high mechanical strength, superior biocompatibility, excellent moisture retention, and inherent ability to support cell adhesion and proliferation, make BC particularly effective for wound healing and skin regeneration. These attributes accelerate tissue repair and foster new tissue formation, highlighting its value in skin-related applications. Additionally, BC's capacity to support osteogenic differentiation, combined with its mechanical robustness, positions it as a strong candidate for bone tissue engineering, facilitating regeneration and repair. Recent advancements have emphasized the development of BC-based hybrid scaffolds to enhance tissue-specific functionalities, including vascularization and cartilage regeneration. These innovations aim to address the complex requirements of various tissue engineering applications. However, challenges remain, particularly regarding the scalability of BC production, cost-effectiveness, and the long-term stability of BC-based scaffolds. Such barriers continue to limit its broader clinical adoption. This review critically examines the synthesis methods, intrinsic properties, and recent innovations in the design of BC-based scaffolds, offering insights into their potential to revolutionize regenerative medicine. Furthermore, it addresses the key challenges and limitations that must be overcome to enable the clinical integration of BC. By addressing these limitations, BC could play a transformative role in advancing tissue engineering and regenerative therapies, bridging the gap between laboratory research and clinical application.

A chronological history of heart valve prostheses to offer perspectives of their limitations

Prosthetic heart valves (PHV) have been studied for around 70 years. They are the best alternative to save the life of patients with cardiac valve diseases. However, current PHVs may still cause significant disadvantages to patients. In general, native heart valves show complex structures and reproducing their functions challenges scientists. Valve repair and replacement are the options to heal heart valve diseases (VHDs), such as stenosis and regurgitation, which show high morbidity and mortality worldwide. Valve repair contributes to the performance of cardiac cycles. However, it fails to restore valve anatomy to its normal condition. On the other hand, replacement is the only alternative to treat valve degeneration. It may do so by mechanical or bioprosthetic valves. Although prostheses may restructure patients' cardiac cycle, both prostheses may show limitations and potential disadvantages, such as mechanical valves causing thrombogenicity or bioprosthetic valves, calcification. Thus, prostheses require constant improvements to remedy these limitations. Although the design of mechanical valve structures has improved, their raw materials cause great disadvantages, and alternatives for this problem remain scarce. Cardiac valve tissue engineering emerged 30 years ago and has improved over time, e.g., xenografts and fabricated heart valves serving as scaffolds for cell seeding. Thus, this review describes cardiac valve substitutes, starting with the history of valvular prosthesis transplants and ending with some perspectives to alleviate the limitations of artificial valves.

Innovative hydrogel solutions for articular cartilage regeneration: a comprehensive review

Articular cartilage damage is predominantly caused by trauma, osteoarthritis (OA), and other pathological conditions. The limited intrinsic capacity of cartilage tissue to self-repair necessitates timely intervention following acute injuries to prevent accelerated degeneration, leading to the development of planar arthritis or even osteoarthritis. Unfortunately, current therapies for articular cartilage damage are inadequate in effectively replacing or regenerating compromised cartilage due to the absence of suitable tissue-engineered artificial matrices. However, there is promise in utilizing hydrogels, a category of biomaterials characterized by their elasticity, smooth surfaces, and high water content, for cartilage regeneration. Recent advancements in hydrogel engineering have focused on improving their bioactive and physicochemical properties, encompassing innovative composition designs, dynamic modulation, and intricate architectures. This review provides a comprehensive analysis of hydrogels for articular cartilage repair, focusing on their innovative design, clinical applications, and future research directions. By integrating insights from the latest research studies and clinical trials, the review offers a unique perspective on the translation of hydrogels for articular cartilage repair, underscoring their potential as promising therapeutic agents.

Recent Advances in Degradable Biomedical Polymers for Prevention, Diagnosis and Treatment of Diseases

Biomedical polymers play a key role in preventing, diagnosing, and treating diseases, showcasing a wide range of applications. Their unique advantages, such as rich source, good biocompatibility, and excellent modifiability, make them ideal biomaterials for drug delivery, biomedical imaging, and tissue engineering. However, conventional biomedical polymers suffer from poor degradation in vivo, increasing the risks of bioaccumulation and potential toxicity. To address these issues, degradable biomedical polymers can serve as an alternative strategy in biomedicine. Degradable biomedical polymers can efficiently relieve bioaccumulation in vivo and effectively reduce patient burden in disease management. This review comprehensively introduces the classification and properties of biomedical polymers and the recent research progress of degradable biomedical polymers in various diseases. Through an in-depth analysis of their classification, properties, and applications, we aim to provide strong guidance for promoting basic research and clinical translation of degradable biomedical polymers.

Substrates with Tunable Hydrophobicity for Optimal Cell Adhesion

Electrospinning is a technique used to create nano/micro-fibrous materials from various polymers for biomedical uses. Polymers like polycaprolactone (PCL) are commonly used, but their hydrophobic properties can limit their applications. To enhance hydrophilicity, nonionic surfactants such as sorbitane monooleate (Span80) and poloxamer (P188) can be added to the PCL electrospinning solution without altering its net charge density. These additions enable the successful production of PCL/P188 and PCL/Span80 fibrous substrates. In this study, P188 and Span80 are incorporated into the PCL solutions; they are successfully electrospun into PCL/P188 and PCL/Span80 substrates, respectively. PCL/P188 substrates show that until a specific P188 concentration, fiber and pore sizes are similar to PCL substrates. However, exceeding 0.30% P188 concentration enlarges fibers, impacting fiber uniformity at higher concentrations. Conversely, higher concentrations of Span80 result in thicker, less uniform fibers, indicating potential disruptions in the electrospinning process. Notably, both surfactants significantly improve substrate hydrophilicity, enhancing the adhesion and proliferation of fibroblasts, endothelial cells, and smooth muscle cells. P188, in particular, shows superior efficacy in promoting cell adhesion and growth at concentrations optimized for different cell types. Therefore, precise surfactant concentrations in the electrospinning solution can lead to the optimization of electrospun substrates for tissue engineering applications.

Innovative Substrate Design with Basement Membrane Components for Enhanced Endothelial Cell Function and Endothelization

Enhancing endothelial cell growth on small-diameter vascular grafts produced from decellularized tissues or synthetic substrates is pivotal for preventing thrombosis. While optimized decellularization protocols can preserve the structure and many components of the extracellular matrix (ECM), the process can still lead to the loss of crucial basement membrane proteins, such as laminin, collagen IV, and perlecan, which are pivotal for endothelial cell adherence and functional growth. This loss can result in poor endothelialization and endothelial cell activation causing thrombosis and intimal hyperplasia. To address this, the basement membrane's ECM is emulated on fiber substrates, providing a more physiological environment for endothelial cells. Thus, fibroblasts are cultured on fiber substrates to produce an ECM membrane substrate (EMMS) with basement membrane proteins. The EMMS then underwent antigen removal (AR) treatment to eliminate antigens from the membrane while preserving essential proteins and producing an AR-treated membrane substrate (AMS). Subsequently, human endothelial cells cultured on the AMS exhibited superior proliferation, nitric oxide production, and increased expression of endothelial markers of quiescence/homeostasis, along with autophagy and antithrombotic factors, compared to those on the decellularized aortic tissue. This strategy showed the potential of pre-endowing fiber substrates with a basement membrane to enable better endothelization.

Non-immune factors cause prolonged myofibroblast phenotype in implanted synthetic heart valve scaffolds

The clinical application of heart valve scaffolds is hindered by complications associated with the activation of valvular interstitial cell-like (VIC-like) cells and their transdifferentiation into myofibroblasts. This study aimed to examine several molecular pathway(s) that may trigger the overactive myofibroblast phenotypes in the implanted scaffolds. So, we investigated the influence of three molecular pathways - macrophage-induced inflammation, the TGF-β1-SMAD2, and WNT/β-catenin β on VIC-like cells during tissue engineering of heart valve scaffolds. We implanted electrospun heart valve scaffolds in adult sheep for up to 6 months in the right ventricular outflow tract (RVOT) and analyzed biomolecular (gene and protein) expression associated with the above three pathways by the scaffold infiltrating cells. The results showed a gradual increase in gene and protein expression of markers related to the activation of VIC-like cells and the myofibroblast phenotypes over 6 months of scaffold implantation. Conversely, there was a gradual increase in macrophage activity for the first three months after scaffold implantation. However, a decrease in macrophage activity from three to six months of scaffold tissue engineering suggested that immunological signal factors were not the primary cause of myofibroblast phenotype. Similarly, the gene and protein expression of factors associated with the TGF-β1-SMAD2 pathway in the cells increased in the first three months but declined in the next three months. Contrastingly, the gene and protein expression of factors associated with the WNT/β-catenin pathway increased significantly over the six-month study. Thus, the WNT/β-catenin pathway could be the predominant mechanism in activating VIC-like cells and subsequent myofibroblast phenotype.

Influence of Substrate Structure and Associated Properties on Endothelial Cell Behavior in the Context of Behaviors Associated with Laminar Flow Conditions

In order to treat most vascular diseases, arterial grafts are commonly employed for replacing small-diameter vessels, yet they often cause thrombosis. The growth of endothelial cells along the interior surfaces of these grafts (substrates) is critical to mitigate thrombosis. Typically, endothelial cells are cultured inside these grafts under laminar flow conditions to emulate the native environment of blood vessels and produce an endothelium. Alternatively, the substrate structure could have a similar influence on endothelial cell behavior as laminar flow conditions. In this study, we investigated whether substrates with aligned fiber structures could induce responses in human umbilical vein endothelial cells (HUVECs) akin to those elicited by laminar flow. Our observations revealed that HUVECs on aligned substrates displayed significant morphological changes, aligning parallel to the fibers, similar to effects reported under laminar flow conditions. Conversely, HUVECs on random substrates maintained their characteristic cobblestone appearance. Notably, cell migration was more significant on aligned substrates. Also, we observed that while vWF expression was similar between both substrates, the HUVECs on aligned substrates showed more expression of platelet/endothelial cell adhesion molecule-1 (PECAM-1/CD31), laminin, and collagen IV. Additionally, these cells exhibited increased gene expression related to critical functions such as proliferation, extracellular matrix production, cytoskeletal reorganization, autophagy, and antithrombotic activity. These findings indicated that aligned substrates enhanced endothelial growth and behavior compared to random substrates. These improvements are similar to the beneficial effects of laminar flow on endothelial cells, which are well-documented compared to static or turbulent flow conditions.

3D printing of heart valves

3D printing technologies have the potential to revolutionize the manufacture of heart valves through the ability to create bespoke, complex constructs. In light of recent technological advances, we review the progress made towards 3D printing of heart valves, focusing on studies that have utilised these technologies beyond manufacturing patient-specific moulds. We first overview the key requirements of a heart valve to assess functionality. We then present the 3D printing technologies used to engineer heart valves. By referencing International Organisation for Standardisation (ISO) Standard 5840 (Cardiovascular implants - Cardiac valve prostheses), we provide insight into the achieved functionality of these valves. Overall, 3D printing promises to have a significant positive impact on the creation of artificial heart valves and potentially unlock full complex functionality.

Shaping the Future of Cardiovascular Disease by 3D Printing Applications in Stent Technology and its Clinical Outcomes

Cardiovascular disease (CVD) is a leading cause of death worldwide. In recent years, 3D printing technology has ushered in a new era of innovation in cardiovascular medicine. 3D printing in CVD management encompasses various aspects, from patient-specific models and preoperative planning to customized medical devices and novel therapeutic approaches. In-stent technology, 3D printing has revolutionized the design and fabrication of intravascular stents, offering tailored solutions for complex anatomies and individualized patient needs. The advantages of 3D-printed stents, such as improved biocompatibility, enhanced mechanical properties, and reduced risk of in-stent restenosis. Moreover, the clinical trials and case studies that shed light on the potential of 3D printing technology to improve patient outcomes and revolutionize the field has been comprehensively discussed. Furthermore, regulatory considerations, and challenges in implementing 3D-printed stents in clinical practice are also addressed, underscoring the need for standardization and quality assurance to ensure patient safety and device reliability. This review highlights a comprehensive resource for clinicians, researchers, and policymakers seeking to harness the full potential of 3D printing technology in the fight against CVD.