Derivation and characterization of sleeping Beauty transposon-mediated porcine induced pluripotent stem cells

The domestic pig is an important large animal model for preclinical testing of novel cell therapies. Recently, we produced pluripotency reporter pigs in which the Oct4 promoter drives expression of the enhanced green fluorescent protein (EGFP). Here, we reprogrammed Oct4-EGFP fibroblasts employing the non-viral Sleeping Beauty transposon system to deliver the reprogramming factors Oct4, Sox2, Klf4 and cMyc. Successful reprogramming to a pluripotent state was indicated by changes in cell morphology and reactivation of the Oct4-EGFP reporter. The transposon-reprogrammed putative iPS cells showed long term proliferation in vitro over >40 passages, expressed transcription factors typical of embryonic stem cells, including OCT4, NANOG, SOX2, REX1, ESRRB, DPPA5 and UTF1 and surface markers of pluripotency, including SSEA-1 and TRA-1-60. In vitro differentiation resulted in derivatives of the three germ layers. Upon injection of putative iPS cells under the skin of immunodeficient mice, we observed teratomas in 3 of 6 cases. These results form the basis for in-depth studies towards the derivation of porcine iPS cells, which hold great promise for preclinical testing of novel cell therapies in the pig model.