A review of the immune response stimulated by xenogenic tissue heart valves

Abstract

Valvular heart disease continues to afflict millions of people around the world. In many cases, the only corrective treatment for valvular heart disease is valve replacement. Valve replacement options are currently limited, and the most common construct utilized are xenogenic tissue heart valves. The main limitation with the use of this valve type is the development of valvular deterioration. Valve deterioration results in intrinsic permanent changes in the valve structure, often leading to hemodynamic compromise and clinical symptoms of valve re-stenosis. A significant amount of research has been performed regarding the incidence of valve deterioration and determination of significant risk factors for its development. As a result, many believe that the underlying driver of valve deterioration is a chronic immune-mediated rejection process of the foreign xenogenic-derived tissue. The underlying mechanisms of how this occurs are an area of ongoing research and active debate. In this review, we provide an overview of the important components of the immune system and how they respond to xenografts. A review of the proposed mechanisms of xenogenic heart valve deterioration is provided including the immune response to xenografts. Finally, we discuss the role of strategies to combat valve degeneration such as preservation protocols, epitope modification and decellularization.