miRNAs promote generation of porcine-induced pluripotent stem cells.

The pigs have similarities of organ size, immunology and physiology with humans. Porcine-induced pluripotent stem cells (piPSCs) have great potential application in regenerative medicine. Here, we established piPSCs induced from porcine fetal fibroblasts by the retroviral overexpression of Oct4, Sox2, Klf4, and c-Myc. The piPSCs not only express pluripotent markers but also have the capacity for differentiation in vivo and in vitro, including EB and teratoma formation. We supplemented microRNAs during the induction process because miR-302a, miR-302b, and miR-200c have been reported to be highly expressed in human and mouse embryonic stem cells and in iPSCs. In this study, we found that the overexpression of miR-302a, miR-302b, and miR-200c effectively improved the reprogramming efficiency and reduced the induction time for piPSCs in the OSKM and OSK induction systems. Due to the similar induction efficiency of 4F-induced piPSCs or of three factors combined with miR-302a, miR-302b, and miR-200c (3F-miRNA-induced piPSCs), we recommend the addition of miRNAs instead of c-Myc to reduce the tumorigenicity of piPSCs.