Pluripotent stem cells are the origin of all cells that form an adult organism. Different states
of pluripotency with specific characteristics such as two-cell-like cells, expanded potential
stem cells, extended pluripotent stem cells, naïve pluripotent stem cells, and primed
pluripotent stem cells have been described. The main differences are the origin, epigenetic
characteristics, expressed markers, and the potential for chimera formation . By analysing
the ability of the chimera formation, we get an insight into their actual differentiation
potential. Some of the newly described types of embryonic stem cells show certain
characteristics of totipotent stem cells. The differences occur also in the conditions of
establishement and maintaining the different types of pluripotent stem cells. Type and
functional characteristics of pluripotent stem cells are culture conditions dependant. By
recognising different characteristics of embryonic stem cells will aid in discovering the role
and functions of different stem cell types duringearly embryonic development. Comparison
of different types of stem cells from the developing embryo with in vitro cultures of
embryonic stem cells is also intriguing. Significant differences are also observed between
stem cells of different organism. Despite intensive research many questions remain
unanswered and we are unable to grow some of the types of pluripotent cell in in vitro
conditions.
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