Chapter 11 Cellular Metaplasia or Transdifferentiaton as a Model for Retinal Cell Differentiation

Abstract

Publisher Summary This chapter discusses the possible mechanisms of transdifferentiation or cellular metaplasia as a model for studying the programming of differentiation in neural and other cells at the cellular and molecular levels. Vertebrate eye tissues are characterized by a unique ability to perform extensive tissue metaplasia and to convert their specificities during regeneration in situ, after the removal of particular tissues. Studies on such instability in differentiation have now been extended to the cellular level by means of cell culture experiments. Besides the pigmented epithelial cells of the retina, cells from the neural retina (NR) of a number of vertebrate species can also extensively transdifferentiate into lens and pigment cells under conditions of cell culture. All the literature since 1975, when the phenomenon was first announced, has been reviewed in the chapter. Transdifferentiation in vitro is a sequential process starting from NR cells and terminating with lens cells, either through the differentiation of pigment cells or not. Several intrinsic and external factors affecting transdifferentiation have been described along with the molecular events observed in the process. There are a number of reasons, although they are not absolutely convincing, as to why transdifferentiation can be a regulatory change not mainly due to a selective outgrowth of mutated cells or a small subpopulation of cells programmed toward only lens or pigment cells.