Mammalian cell dedifferentiation as a possible outcome of stress.

Differentiation cascades are arranged hierarchically; stem cells positioned at the top of the hierarchy generate committed progenitors that, in turn, proliferate and further differentiate stepwise into mature progeny. This rigid, irreversible structure ensures the phenotypic stability of adult tissues. However, such rigidity may be problematic under conditions of tissue damage when reconstitution is required. Although it may seem unlikely that the restrictions on changes in cell phenotypes would be lifted to enable tissue reconstitution, it is nevertheless possible that mammalian tissues are endowed with sufficient flexibility to enable their adaptation to extreme conditions.