Verfaillie Figure 7. Stem cell plasticity—possible mechanisms.

Four possible hypotheses exist to explain stem cell plasticity: (A) multiple stem cells may coexist in multiple tissues; (B) donor cells may fuse with host cells and acquire characteristics of the host cells; (C) cells may undergo de- and redifferentiation, or trans-differentiate; (D) multipotent stem cells “akin” to ES cells may persist past initial lineage specification. Scientific evidence exists for all possible explanations.

Abbreviations: ES, embryonic stem; HSC, hematopoietic stem cells.