Decellularization Following Fixation of Explanted Aortic Valves as a Strategy for Preserving Native Mechanical Properties and Function

Advances and Challenges of Tissue Vascular Scaffolds and Supercritical Carbon Dioxide Technology in Cardiovascular Diseases

BACKGROUND

Atherosclerosis often leads to ischemic heart disease and peripheral artery disease. Traditional revascularization technique such as bypass grafting using autologous vessels are commonly employed. However, limitations arise when patients lack suitable grafts due to underlying diseases or previous surgeries, prompting the need to substitute vessel grafts. Due to the high biocompatibility of decellularized products (grafts or scaffolds) prepared using supercritical carbon dioxide (ScCO2), it has been widely applied in decellularization-related technologies in recent years. Therefore, this review article will comprehensively discuss the current developments in tissue vascular scaffolds applied to the treatment of cardiovascular diseases, with a particular focus on the application of supercritical carbon dioxide technology in this field and the challenges it faces.

METHOD

This review was compiled by searching relevant references on PubMed database (before June 2024) based on selected key words and specific terms.

RESULTS

ScCO2 is an effective and eco-friendly extraction agent widely used in industries like food, pharmaceuticals, and cosmetics. It has been applied in decellularization processes to obtain extracellular matrices (ECMs) from tissues. ScCO2 technology has emerged as a promising method in cardiovascular disease treatment, particularly for developing tissue vascular scaffolds. ScCO2 effectively removes cellular components while preserving the ECM, ensuring high biocompatibility and reduced immune response. It has been applied to decellularize tissues like heart valves and arteries, creating scaffolds that mimic natural ECM to support cell proliferation and tissue regeneration. Despite challenges such as solubility limitations and cost, ScCO2 offers advantages like low toxicity and ease of use, making it a valuable tool in advancing regenerative medicine for cardiovascular applications.

CONCLUSION

ScCO2 has the advantages of low cellular toxicity, cost-effectiveness, and ease of manipulation. These characteristics have the potential to lead to significant progress in cardiovascular research on tissue regeneration.

Hemodynamic evaluation of biomaterial-based surgery for Tetralogy of Fallot using a biorobotic heart, in silico, and ovine models

Tetralogy of Fallot is a congenital heart disease affecting newborns and involves stenosis of the right ventricular outflow tract (RVOT). Surgical correction often widens the RVOT with a transannular enlargement patch, but this causes issues including pulmonary valve insufficiency and progressive right ventricle failure. A monocusp valve can prevent pulmonary regurgitation; however, valve failure resulting from factors including leaflet design, morphology, and immune response can occur, ultimately resulting in pulmonary insufficiency. A multimodal platform to quantitatively evaluate the effect of shape, size, and material on clinical outcomes could optimize monocusp design. This study introduces a benchtop soft biorobotic heart model, a computational fluid model of the RVOT, and a monocusp valve made from an entirely biological cell-assembled extracellular matrix (CAM) to tackle the multifaceted issue of monocusp failure. The hydrodynamic and mechanical performance of RVOT repair strategies was assessed in biorobotic and computational platforms. The monocusp valve design was validated in vivo in ovine models through echocardiography, cardiac magnetic resonance, and catheterization. These models supported assessment of surgical feasibility, handling, suturability, and hemodynamic and mechanical monocusp capabilities. The CAM-based monocusp offered a competent pulmonary valve with regurgitation of 4.6 ± 0.9% and a transvalvular pressure gradient of 4.3 ± 1.4 millimeters of mercury after 7 days of implantation in sheep. The biorobotic heart model, in silico analysis, and in vivo RVOT modeling allowed iteration in monocusp design not now feasible in a clinical environment and will support future surgical testing of biomaterials for complex congenital heart malformations.

Biorobotic hybrid heart as a benchtop cardiac mitral valve simulator

In this work, we developed a high-fidelity beating heart simulator that provides accurate mitral valve pathophysiology. The benchtop platform is based on a biorobotic hybrid heart that combines preserved intracardiac tissue with soft robotic cardiac muscle providing dynamic left ventricular motion and precise anatomical features designed for testing intracardiac devices, particularly for mitral valve repair. The heart model is integrated into a mock circulatory loop, and the active myocardium drives fluid circulation producing physiological hemodynamics without an external pulsatile pump. Using biomimetic soft robotic technology, the heart can replicate both ventricular and septal wall motion, as well as intraventricular pressure-volume relationships. This enables the system to recreate the natural motion and function of the mitral valve, which allows us to demonstrate various surgical and interventional techniques. The biorobotic cardiovascular simulator allows for real-time hemodynamic data collection, direct visualization of the intracardiac procedure, and compatibility with clinical imaging modalities.

Robotic right ventricle is a biohybrid platform that simulates right ventricular function in (patho)physiological conditions and intervention

The increasing recognition of the right ventricle (RV) necessitates the development of RV-focused interventions, devices and testbeds. In this study, we developed a soft robotic model of the right heart that accurately mimics RV biomechanics and hemodynamics, including free wall, septal and valve motion. This model uses a biohybrid approach, combining a chemically treated endocardial scaffold with a soft robotic synthetic myocardium. When connected to a circulatory flow loop, the robotic right ventricle (RRV) replicates real-time hemodynamic changes in healthy and pathological conditions, including volume overload, RV systolic failure and pressure overload. The RRV also mimics clinical markers of RV dysfunction and is validated using an in vivo porcine model. Additionally, the RRV recreates chordae tension, simulating papillary muscle motion, and shows the potential for tricuspid valve repair and replacement in vitro. This work aims to provide a platform for developing tools for research and treatment for RV pathophysiology.

Decellularized blood vessel development: Current state-of-the-art and future directions

Vascular diseases contribute to intensive and irreversible damage, and current treatments include medications, rehabilitation, and surgical interventions. Often, these diseases require some form of vascular replacement therapy (VRT) to help patients overcome life-threatening conditions and traumatic injuries annually. Current VRTs rely on harvesting blood vessels from various regions of the body like the arms, legs, chest, and abdomen. However, these procedures also produce further complications like donor site morbidity. Such common comorbidities may lead to substantial pain, infections, decreased function, and additional reconstructive or cosmetic surgeries. Vascular tissue engineering technology promises to reduce or eliminate these issues, and the existing state-of-the-art approach is based on synthetic or natural polymer tubes aiming to mimic various types of blood vessel. Burgeoning decellularization techniques are considered as the most viable tissue engineering strategy to fill these gaps. This review discusses various approaches and the mechanisms behind decellularization techniques and outlines a simplified model for a replacement vascular unit. The current state-of-the-art method used to create decellularized vessel segments is identified. Also, perspectives on future directions to engineer small- (inner diameter >1 mm and <6 mm) to large-caliber (inner diameter >6 mm) vessel substitutes are presented.