Pluripotent Stem Cells: Current Understanding and Future Directions

Figure 4

Visual comparison of murine and human PSCs. (a) In mouse, ESCs and EpiSCs are characterized by a different pluripotent state, called naïve and primed, respectively, which reflects their embryonic origin. The stability and homogeneity of mESCs cultured in 2i represent a developmental ground state closely reflective that of the ICM of preimplantation blastocysts. Pluripotent stem cell can be obtained also by reprogramming of somatic cells. Mouse iPSCs, cultured in 2i, show a ground state similar to mESCs. (b) Human ESCs and iPSCs cultured in presence of bFGF/Activin are in the primed state. Different conditions have been established to convert primed hESCs and hiPSCs into a naïve state. The initial comparative analysis of the naïve human cell lines clearly indicates that the various culture conditions induce different pluripotent states, each showing similar features, but not identical, to those of naïve mESCs. Whether the authentic pluripotent ground state of naïve hESCs is identical to that of mESCs, it is still to be determined.

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