Abstract：Induced pluripotent stem cells (iPSCs) can be generated from somatic cells by ectopic-expression of specific inducing factors, which are capable of maintaining self-renewal and an undifferentiated state just like embryonic stem cells (ESCs). Moreover, the application of iPSCs can avoid the immunological rejection and ethical challenges faced by ESCs research and clinical application. iPSCs were originally derived from Mus musculus somatic cells by ectopic-expression of 4 transcription factors, octamer-binding transcriptionfactor 4(Oct4), sex determing region Y-box 2(Sox2), proto-oncogene protein(Myc) and Krüppel-like factor 4(Klf4), with retrovirus vectors in 2006. Over past years, many scientists made great efforts to improve reprogramming technique and elucidate the mechanism of it. Inducing methods of iPSCs are therefore diversified, since it has been made available to transfer reprogramming factors using DNA virus vectors, plasmid vectors, and minicircle DNA vectors. Although DNA transfection-based method ologies are ostensibly safe, they nonetheless entail some risk of genomic recombination or insertional mutagenesis. RNA molecules and purified reprogramming functional proteins fused with a cell penetrating peptide were used to reprogram differentiated cells to a pluripotent state, respectively, with considerable conversion efficiencies and kinetics, where there is absolutely no genomic recombination or insertional mutagenesis. At the same time, some researchers used a number of small-molecule compounds aiming at replacing some transcription factors and finally succeeding in obtaining iPSCs completely induced by a group of chemicals without any genetic manipulation at a frequency up to 0.2%, which is even more efficient than viral protocols, also contributing to the generation of chimera. iPSCs research of big domestic animals can't be parallel with that of mouse(Mus musculus) or human(Homo sapiens), which have been much focused on, and ESCs of many big domestic animals haven't been derived yet. However, iPSCs derived from the somatic cells of pig(Sus scrofa), bovine(Bos taurus) and sheep(Ovis aries) were obtained by the transduction of serial transcription factors, while only iPSCs of pigs and sheep could generate chimeras after injected into the early embryo. The big domestic animals, such as pigs, are similar to human beings in anatomy and physiology, which can be a good model of organ transplantation and regenerative medicine, and they provide the main sources of meat and milk for human beings. Thus the iPSCs of the big domestic animals play significant roles in manufacture and clinical application. This review presents a general progress on the inducing methods, efficiency and mechanism of the iPSCs as well as the research status of iPSCs of the big domestic animals.
