The clinical application potential of extracellular matrix in cardiac tissue engineering

Biological Scaffolds for Congenital Heart Disease

Congenital heart disease (CHD) is the most predominant birth defect and can require several invasive surgeries throughout childhood. The absence of materials with growth and remodelling potential is a limitation of currently used prosthetics in cardiovascular surgery, as well as their susceptibility to calcification. The field of tissue engineering has emerged as a regenerative medicine approach aiming to develop durable scaffolds possessing the ability to grow and remodel upon implantation into the defective hearts of babies and children with CHD. Though tissue engineering has produced several synthetic scaffolds, most of them failed to be successfully translated in this life-endangering clinical scenario, and currently, biological scaffolds are the most extensively used. This review aims to thoroughly summarise the existing biological scaffolds for the treatment of paediatric CHD, categorised as homografts and xenografts, and present the preclinical and clinical studies. Fixation as well as techniques of decellularisation will be reported, highlighting the importance of these approaches for the successful implantation of biological scaffolds that avoid prosthetic rejection. Additionally, cardiac scaffolds for paediatric CHD can be implanted as acellular prostheses, or recellularised before implantation, and cellularisation techniques will be extensively discussed.

Promoting Cardiac Regeneration and Repair Using Acellular Biomaterials

Ischemic heart disease is a common cause of end-stage heart failure and has persisted as one of the main causes of end stage heart failure requiring transplantation. Maladaptive myocardial remodeling due to ischemic injury involves multiple cell types and physiologic mechanisms. Pathogenic post-infarct remodeling involves collagen deposition, chamber dilatation and ventricular dysfunction. There have been significant improvements in medication and revascularization strategies. However, despite medical optimization and opportunities to restore blood flow, physicians lack therapies that directly access and manipulate the heart to promote healthy post-infarct myocardial remodeling. Strategies are now arising that use bioactive materials to promote cardiac regeneration by promoting angiogenesis and inhibiting cardiac fibrosis; and many of these strategies leverage the unique advantage of cardiac surgery to directly visualize and manipulate the heart. Although cellular-based strategies are emerging, multiple barriers exist for clinical translation. Acellular materials have also demonstrated preclinical therapeutic potential to promote angiogenesis and attenuate fibrosis and may be able to surmount these translational barriers. Within this review we outline various acellular biomaterials and we define epicardial infarct repair and intramyocardial injection, which focus on administering bioactive materials to the cardiac epicardium and myocardium respectively to promote cardiac regeneration. In conjunction with optimized medical therapy and revascularization, these techniques show promise to upregulate pathways of cardiac regeneration to preserve heart function.

The extracellular matrix patch implanted in the right ventricle evaluated with cardiovascular magnetic resonance protocol to assess regional physio-mechanical properties

OBJECTIVES

An extracellular matrix patch was implanted in the porcine right ventricle for in situ myocardial regeneration. A newly developed cardiovascular magnetic resonance protocol was utilized to investigate the regional physio-mechanical function of the patch.

METHODS

Cardiovascular magnetic resonance was performed at 60-day after the porcine right ventricular wall full thickness substitution with an extracellular matrix cardiac patch (n = 5). Dacron patches and remote normal right ventricle served as control (n = 5/each). Late gadolinium enhancement, strain encoding and rest perfusion were measured for scar/patch detection, regional contractility and tissue perfusion. Image analyses were performed by two observers to validate interobserver reproducibility.

RESULTS

All imaging sequences were successfully obtained. The patches were located with late gadolinium enhancement imaging in 95% accuracy. All the parameters demonstrated significant differences among extracellular matrix, Dacron and normal myocardium (P < 0.05), which correlated with histological findings, including constructive remodelling with nascent myocardium and profound vasculogenesis/angiogenesis in extracellular matrix patches, and scar formation in Dacron. Bland-Altman analysis demonstrated good interobserver reproducibility with minimal bias (strain encoding/peak strain: mean difference = -0.32%, 95% limits of agreement = -1.2 to 0.57, correlation = 0.97; rest perfusion/relative maximum upslope: mean difference = -0.74, 95% limits of agreement = -2.0 to 0.53, correlation = 0.92), along with excellent correlation obtained from linear regression (strain encoding: R² = 0.93; rest perfusion: R² = 0.85).

CONCLUSIONS

With the cardiovascular magnetic resonance protocol, we successfully confirmed early signs of functional myocardial regeneration in implanted extracellular matrix patches. This approach is promising in assessing in situ regional physio-mechanical properties and degree of regeneration of implanted tissue-engineered materials.