Investigation of the Mechanical And Microstructural Properties in Coronary Arteries Following Decellularization

Abstract

The heart is responsible for pumping blood throughout the body, and like all other tissues, the heart muscle requires a supply of oxygen-rich blood to function properly. This blood is supplied by the coronary arteries – the network of blood vessels on the surface of the heart. There are two main coronary arteries: the left (main) coronary artery and the right coronary artery. The left coronary artery divides into the left anterior descending artery (LADA) and the left circumflex artery. The LADA is the largest of the coronary arteries, and it is the most susceptible to disease. Coronary artery disease is characterized by plaque accumulation on the inner arterial wall, which limits the blood flow to the heart muscle and can result in a heart attack. In severe coronary artery disease, surgeons perform a procedure called coronary artery bypass grafting (CABG), which bypasses the diseased portion of the artery by using a graft to redirect blood from the aorta to the portion of the artery distal from the blockage. Usually, this graft comes from another artery within the patient’s body; however, this is not always ideal due to limited availability of viable vessels and high graft failure rates. When autologous grafts are unable to be used, a vessel conduit is required, however, current coronary artery conduits are suboptimal. An alternative approach to tissue-engineered vascular grafts is utilizing a donor vessel’s native extracellular matrix (ECM) to serve as a scaffold. To minimize the risk of an immune response from the patient, the donor vessel oftentimes needs to be decellularized to remove all cellular components. While decellularization remains a promising approach, there is not a standardized decellularization method for coronary arteries, and there is a lack of research investigating how the microstructure behaves under pathologic loads following decellularization. This thesis addresses this gap by proposing a novel protocol for the decellularization of porcine coronary artery tissue that effectively removes cellular components, while retaining the native tissue structure and function. This decellularization protocol consists of several treatments using detergents, enzymes, and rinsing steps, and the removal of cells is confirmed using histology and microscopic evaluation. To further determine the effect of this decellularization procedure on the mechanical properties and collagen fiber architecture, biaxial mechanical testing and polarized spatial frequency domain imaging (pSFDI) were performed before and after decellularization. This investigation revealed minimal alteration to the mechanical and microstructural properties. The findings of this thesis will be valuable to the refinement of coronary artery tissue grafts, which may ultimately improve suboptimal outcomes in coronary bypass surgeries.