Lack of ABH-antigen expression on human cardiac valves

Seeding of heart valve prostheses with human umbilical vein endothelial cells (HUVEC) and human saphenous vein endothelial cells (HSVEC) has been applied to create a viable valve surface and improve valve performance. HUVEC and HSVEC are well characterized and have been used as a model of endothelial antigenicity, but antigenicity of the valve endothelium is less well characterized. To clarify this issue, we studied the expression of blood group antigens by human valvular endothelium, HSVEC and HUVEC.

Human aortic and mitral valves and myocardial tissue were freshly harvested from explanted hearts of patients undergoing heart transplantation (blood group A, n = 4; group O, n = 4) or valve replacement (blood group B, n = 4). After fixation in Carnoy's or formalin solution, paraffin sections were stained with anti-A (blood group A), anti-B (blood group B), and anti-H (blood group O) antibodies. Human umbilical cords were freshly harvested postpartum, and human saphenous veins were obtained from patients undergoing coronary bypass grafting (each blood group, n = 2) and similarly fixed and stained to detect ABO antigens. The preservation of endothelium was confirmed by staining with anti-CD 31 monoclonal antibody. All sections were examined by light microscopy.

CD 31 staining demonstrated vascular and valve endothelial preservation. Human umbilical cords, saphenous vein and myocardium showed strongly expressed A, B and H blood group antigens on vascular endothelium. However, no A, B and H antigens were detected on the valvular endothelium.

Valve endothelial cells appear to be a class of specialized endothelial cells that does not express the ABO antigens. Due to the strong expression of A, B and H antigens by HUVEC and HSVEC blood group cross-matching should be considered for non-autologous endothelialization of valve prostheses.