A Kyoto University research group led by Keisuke Okita, a lecturer of the Center for iPS Cell Research and Application (CiRA), and CiRA Director Shinya Yamanaka, a professor of the Institute for Integrated Cell-Material Sciences (iCeMS), in collaboration with Gifu University, RIKEN, the nonprofit organization HLA Laboratory, demonstrated that gene-integration-free human induced pluripotent stem cells (iPSCs) can be efficiently generated by introducing six factors - OCT3⁄4, SOX2, KLF4, LIN28, L-MYC and p53 shRNA - to fibroblasts via episomal plasmid vectors.

With the same approach, they also succeeded in establishing gene-integration-free iPSCs from dental pulp cells taken from two donors whose human leukocyte antigen (HLA) type is homozygous at three major HLA loci, which will match approximately 20 percent of Japanese population. It was also confirmed that the generated iPSCs can be differentiated into dopamine neurons and retinal pigment epithelial cells. It is hoped that this method will contribute to more efficient generation of clinical-grade iPSCs for transplantation therapy.

Jounal: Nature Method
A more efficient method to generate integration-free human iPS cells
Keisuke Okita, Yasuko Matsumura, Yoshiko Sato, Aki Okada, Asuka Morizane, Satoshi Okamoto, Hyenjong Hong, Masato Nakagawa, Koji Tanabe, Ken-ichi Tezuka, Toshiyuki Shibata, Takahiro Kunisada, Masayo Takahashi, Jun Takahashi, Hiroh Saji, Shinya Yamanaka.