Induced pluripotent stem (iPS) cells have the potential to become a universal 
resource for cell-based therapies in regenerative medicine; however, prior to 
the use of such iPS cell-based therapies, preclinical assessment of their safety 
and efficacy is essential. Non-human primates serve as valuable animal models 
for human diseases or biomedical research; therefore, in this study, we 
generated cynomolgus monkey iPS cells from adult skin and fetal fibroblast cells 
by the retrovirally mediated introduction of four human transcription factors: 
c-Myc, Klf4, Oct3/4, and Sox2 (the so-called "Yamanaka factors"). Twenty to 
30 days after the introduction of these factors, several cynomolgus monkey 
embryonic stem (ES) cell-like colonies appeared on SNL and mouse embryonic 
fibroblast (MEF) feeder layers. These colonies were picked and cultivated in 
primate ES medium. Seven iPS cell lines were established, and we detected the 
expression of pluripotent markers that are also expressed in ES cells. Reverse 
transcription polymerase chain reaction (PCR) showed that these iPS cells 
expressed endogenous c-Myc, Klf4, Oct3/4, and Sox2 genes, whereas several 
transgenes were silenced. Embryoid body and teratoma formation showed that the 
cynomolgus iPS cells had the developmental potential to differentiate into cells 
of all three primary germ layers. In summary, we generated cynomolgus monkey iPS 
cells by retrovirus-mediated transduction of the human transcription factors, 
c-Myc, Klf4, Oct3/4, and Sox2 into adult cynomolgus monkey skin cells and fetal 
fibroblasts. The cynomolgus monkey is the most relevant primate model for human 
disease, and the highly efficient generation of monkey iPS cells would allow 
investigation of the treatments of various diseases in this model via 
therapeutic cloning.