Characterization of induced tissue-specific stem cells from pancreas by a synthetic self-replicative RNA

Induced pluripotent stem (iPS) cells have significant implications for overcoming most of the ethical issues associated with embryonic stem (ES) cells. Furthermore, our recent study demonstrated the generation of induced tissue-specific stem (iTS) cells by transient overexpression of the reprogramming factors using a plasmid combined with tissue-specific selection. In this study, we were able to generate RNA-based iTS cells that utilize a single, synthetic, self-replicating VEE-RF RNA replicon expressing four reprogramming factors (OCT4, KLF4, SOX2, and GLIS1). A single VEE-RF RNA transfection into mouse pancreatic tissue resulted in efficient generation of iTS cells from pancreas (iTS-P cells) with genetic markers of endoderm and pancreatic progenitors and differentiation into insulin-producing cells more efficiently than ES cells. Subcutaneous transplantation of iTS-P cells into immunodeficient mice resulted in no teratoma formation. Bisulfite genomic sequencing demonstrated that the promoters of Oct4 and Nanog remained partially methylated in iTS-P cells. We compared the global gene-expression profiles of ES cells, iTS-P cells, and pancreatic islets. Microarray analyses confirmed that the iTS-P cells were similar but not identical to ES cells compared with islets. These data suggest that iTS-P cells are cells that inherit numerous components of epigenetic memory from pancreas cells and acquire self-renewal potential. The generation of iTS cells may have important implications for the clinical application of stem cells.