PORCINE VALVES ARE REENDOTHELIALIZED BY HUMAN RECIPIENT ENDOTHELIUM IN-VIVO

The degeneration of human allogeneic and porcine xenogeneic heart valv es has not been clearly understood. The question is whether the observ ed loss of function and calcification is primarily an immunologic proc ess or a mechanical process or is influenced by both factors. In the c urrent study, we looked at explanted xenogeneic heart valves for the p resence of recipient endothelium. Explanted valves were shock frozen a nd stored at -80 degrees C before use. They were subsequently examined by immunohistochemical staining with a variety of monoclonal antibodi es. Xenogeneic valves showed clearly positive results for the human ma jor histocompatibility complex class I and class TI antigens and morph ologically showed a thin layer of viable endothelium restricted to the annular region of the valve. Additionally, they were also positive fo r intercellular adhesion molecule-1 and the H-Y antigen. Although the xenogeneic valves were significantly degenerated, the endothelium was clearly defined and could be identified immunohistochemically as being of recipient origin. The grafts remained negative for endothelial cel l-leukocyte adhesion molecule-1 and factor VIII. These data allow spec ulation on whether reendothelialization of valvular grafts with recipi ent endothelium is a normal repair mechanism in vivo.