1:Biocruces Bizkaia Health Research Institute; 2:Basque Center for Blood Transfusion and Human Tissues

The successful reprograming of human somatic cells into induced pluripotent stem cells (hiPSCs) represented a turning point in the stem cell research field owing to their ability to differentiate into any cell type and lack of ethical issues. In the mouse, PSCs are thought to exist in a naive state, the cell culture equivalent of the immature, pre-implantation embryo whereas in humans, PSCs are in a primed state, which is more committed pluripotent state than naive state. Recent studies have focused on capturing a similar cell state in human, since their earlier development stage and lack of cell-of-origin epigenetic memory make the better candidates for further re-differentiation and use in disease modelling, regenerative medicine and drug discovery. In this study, we compared and evaluated the successful establishment and maintenance of primed hiPSC and human embryonic stem cell (hESC) lines with three different naive conversion media both feeder and feeder-free conditions. In addition, we compared the directed differentiation capacity of primed and naive cells in the three germ layers. We characterized these different cell states with commonly used pluripotent and lineage specific markers, and showed that, in general, naive culture medium 1 (in both feeder and feeder-free system) confers greater hiPSCs and hESCs viability and highest naive pluripotency markers expression. This medium also allows for better differentiation of cells toward endoderm.