Pigs as Models of Preclinical Studies and In Vivo Bioreactors for Generation of Human Organs

Abstract

Pigs are valuable and essential large animal models for human medical applications , including for stem cell therapy. Moreover, substantial effort has been made to directly engraft genetically engineered pig organs in the human body and to use pigs as in vivo bioreactors for the growth and development of human cells, tissue, or organs. However, engraftment of human cells in pigs has not yet been achieved. Although severe combined immunodeficient pigs have been developed, which can accept human biological materials, these pigs do not have practical value at present owing to difficulty in their care. To overcome these current limitations, we have proposed the generation of operational immunodeficient pig models by simply removing the thymus and spleen, enabling the long-term accommodation of human tissue. In this review, we summarize research progress on xenotransplantation animal models that accept human cells, tissues, or organs.