The Many Facets of Cell Reprogramming

Reprogramming, transdifferentiation, transdetermination, and dedifferentiation represent multiple aspects of the same phenomenon, ie, the conversion of one cell type into another. Collectively, these cell transformations include (1) the switch from one differentiated cell to another differentiated cell type; (2) the developmental plasticity of stem cells that, by crossing tissue boundaries, commit to lineages different from those of the organ of origin; and (3) the regression of mature cells to a proliferative condition or to a unipotent or multipotent progenitor state.1 This unexpected biological flexibility has challenged the view that changes in phenotype could not take place once a cell, through a hierarchical progressive restriction of developmental options, had attained its stable mature properties. Similarly, adult stem and progenitor cells may not be discrete “fixed” entities but functional units, and a bidirectional shift between more primitive and more differentiated phenotypes may occur.1