Induced Pluripotent Stem Cells Generated Without Viral Integration

TLDR

Pluripotent stem cells have been produced from somatic cells by viral delivery of Oct4, Sox2, Klf4, and c‑Myc, but this approach relies on potentially harmful genome‑integrating viruses. We reprogrammed mouse fibroblasts and liver cells into iPS cells by transiently transducing them with non‑integrating adenoviruses expressing Oct4, Sox2, Klf4, and c‑Myc. The resulting adeno‑iPS cells displayed DNA demethylation, endogenous pluripotency gene expression, teratoma formation, and germ‑line contribution in chimeric mice, demonstrating that insertional mutagenesis is unnecessary and offering a safer method for patient‑specific stem cell generation and comparative studies with embryonic stem cells.

Abstract

Pluripotent stem cells have been generated from mouse and human somatic cells by viral expression of the transcription factors Oct4, Sox2, Klf4, and c-Myc. A major limitation of this technology is the use of potentially harmful genome-integrating viruses. We generated mouse induced pluripotent stem (iPS) cells from fibroblasts and liver cells by using nonintegrating adenoviruses transiently expressing Oct4, Sox2, Klf4, and c-Myc. These adenoviral iPS (adeno-iPS) cells show DNA demethylation characteristic of reprogrammed cells, express endogenous pluripotency genes, form teratomas, and contribute to multiple tissues, including the germ line, in chimeric mice. Our results provide strong evidence that insertional mutagenesis is not required for in vitro reprogramming. Adenoviral reprogramming may provide an improved method for generating and studying patient-specific stem cells and for comparing embryonic stem cells and iPS cells.