ABSTRACT
Regeneration of tissues and organs depends on obtaining the cells required to form the new structure. These cells usually originate from two origins: (1) resident stem cells or (2) mature cells close to the injury site that lose their phenotype and dedifferentiate. This chapter focuses on the process of cellular dedifferentiation as a source for cells of regenerating tissues and organs. In deuterostome animals (vertebrates and some invertebrates) that show high regeneration capacities, the regeneration process usually relies on cell dedifferentiation. Dedifferentiating cells undergo various morphological changes that can range from subtle to dramatic, as in some cases where cells lose major cellular components. Dedifferentiated cells also undergo a reprogramming of their genetic profile, increasing or decreasing the expression of specific genes or in some cases expressing genes associated with embryonic processes. However, the genetic changes associated with regeneration are distinct from those that take place after induced cell reprogramming to obtain pluripotential stem cells. Following dedifferentiation, cells usually proliferate before redifferentiating and forming the tissues of the regenerated structure. In some cases, dedifferentiation can even give rise to stem cells of a particular organ. Finally, intracellular and extracellular factors that modulate the differentiated/dedifferentiated status of cells are discussed.
