Discrimination of Stem Cell Status after Subjecting Cynomolgus Monkey Pluripotent Stem Cells to Naive Conversion

Experimental animal models have played an indispensable role in the development of human induced pluripotent stem cell (iPSC) research. The, derivation of high-quality (so-called “true Naive state”) iPSCs of non-human primates enhances their application and safety for human regenerative medicine. Although several attempts have been made to convert human and non-human primate PSCs into a truly Naive state, it is unclear which evaluation methods can discriminate them as being truly Naive. Here we derived Naive-like Cynomolgus monkey (Cm) (Macaca fascicularis) embryonic stem cells (ESCs) and iPSCs, and evaluated their potential as a highly accurate indicator of the properties of Naive-like human ESC/iPS cells. Several characteristics of Naive-like Cm ESCs including colony morphology, teratoma-forming ability, leukaemia inhibitory factor dependency, and mitochondrial respiration were confirmed. Next, we generated Cm iPSCs and converted them to a Naive-like state. When these were subjected to in vitro differentiation, some exhibited heterogeneity and showed resistance to differentiation. The difficulty of achieving chimeric contribution to mouse or rabbit embryos suggested incomplete Naive conversion. Actually, transcriptomic comparison of PSCs with early Cm embryos elucidated the partial achievement of Naive conversion. This study offers valuable pointers for deriving true Naive PSCs while avoiding irrelevant or misleading evidence of Naive-like features.