Pig islet for xenotransplantation in human: structural and physiological compatibility for human clinical application

Allogeneic islet transplantation has proven difficult because organ shortages are recurrent, several pancreas donors are often needed to treat one diabetic recipient, and the intrahepatic site of islet implantation may not be the most appropriate site. Thus, another source of insulin-producing cells would be beneficial; and pigs represent a possible and viable source for obtaining such cells. Although the use of pig islet grafts appears to be difficult because of the species barrier, recent reports demonstrated that pig islet xenotransplantation can overcome the immunological barrier following strong immunosuppression and function successfully in primates for at least 6 months. Before becoming clinically applicable, however, pig islet xenotransplantation must still overcome the structural and physiological incompatibility between pig donor and human recipient. Researchers agree that it is necessary to produce more preclinical data in the pig-to-primate model before any pig-to-human transplantation of islets can be considered. Therefore, in this review, we provide a summary of the present state of knowledge about pig and human islet compatibility.