α-1,3-Galactosyltransferase knockout pig induced pluripotent stem cells: a cell source for the production of xenotransplant pigs.

The shortage of human organs and tissues for transplant has led to significant interest in xenotransplantation of pig tissues for human patients. However, transplantation of pig organs results in an acute immune rejection, leading to death of the organ within minutes. The α-1,3-galactosyltransferase (GALT) gene has been knocked out in pigs to reduce rejection, yet additional genes need to be modified to ultimately make pig tissue immunocompatible with humans. The development of pig induced pluripotent stem cells (piPSCs) from GALT knockout (GALT-KO) tissue would provide an excellent cell source for complex genetic manipulations (e.g., gene targeting) that often require highly robust and proliferative cells. In this report, we generated GALT-KO piPSCs by the overexpression of POU5F1, SOX2, NANOG, LIN28, KLF-4, and C-MYC reprogramming genes. piPSCs showed classical stem cell morphology and characteristics, expressing integrated reprogramming genes in addition to the pluripotent markers AP, SSEA1, and SSEA4. GALT-KO piPSCs were highly proliferative and possessed doubling times and telomerase activity similar to human embryonic stem cells. These results demonstrated successful reprogramming of GALT-KO fibroblasts into GALT-KO piPSCs. GALT-KO piPSCs are potentially an excellent immortal cell source for the generation of pigs with complex genetic modifications for xenotransplantation, somatic cell nuclear transfer, or chimera formation.