Epithelial-mesenchymal transition, transdifferentiation, reprogramming and metaplasia: modern view on the problem

The article portrays modern views on the problems of formation of metaplasia, transdifferentiation and reprogramming of cells and epithelial-mesenchymal transition on the basis of analysis of literature and the results of our own observations. Transdifferentiation in this article is considered as a kind of metaplasia, which is characterized by an irreversible transition of already differentiated cells into another type, due to the loss of one phenotype and the production of another. Metaplasia, in its broad aspect means the transformation of one cellular or tissue phenotype into another and occurs both through the transformation of stem cells and direct conversion of already differentiated cells. In addition to this metaplasia can be considered as a potentially reversible change, in which differentiated cell types are replaced by other differentiated cell types, usually better adapted to the transformed environmental conditions. Epithelial-mesenchymal transition is the process of epithelial cells alteration of epithelial phenotype to mesenchymal phenotype occurring in embryonic development, healing of wounds as well as in the pathological processes, including tumor progression and fibrosis...