Oct4-EGFP Transgenic Pigs as a New Tool for Visualization of Pluripotent and Reprogrammed Cells

Pluripotent cells proliferate for indefinite periods of time and possess the ability to differentiate to any cell of an organism. These properties render these cells promising for cell therapies of degenerative diseases. As of today, true germ-line competent pluripotent stem cells have been derived only in the laboratory mouse and the rat, while all experiments failed to establish true pluripotent cells in the large domestic species such as cattle and pigs. However, the frequently used mouse and rat models are of limited value for preclinical testing of novel therapies, mainly due to significant differences to humans. In contrast, the domestic pig is thought to be a promising preclinical model for novel therapies because pigs have a similar anatomy and physiology to humans, and have a long and successful record in biomedicine for the benefit of human patients. We have produced transgenic pigs carrying the Oct4 gene fused to the enhanced green fluorescence promoter protein (eGFP) cDNA to allow identification of pluripotent cells in the domestic pig. The transcription factor Oct4 is a stem-cell-specific marker gene that is essential for the maintenance of pluripotency in mouse and human. These pigs express the Oct4/eGFP transgene exclusively in the pluripotent cells of the body, such as early embryos and stem cells of various tissues, including spermatogonial stem cells in the testicles. The non-invasive imaging based on the green fluorescence provides a convenient means to monitor porcine stem cells with regard to localization, survival, proliferation, and function. Somatic cells from the Oct4/GFP transgenic pigs have already proved a valuable tool in studying reprogramming of somatic cells to porcine iPS cells. The Oct4/eGFP transgenic pigs offer a useful non-invasive imaging system for monitoring porcine cells and should play a critical role in the study of stem cell biology and reprogramming in the domestic pig, with significant benefits for the development of novel cell therapies.