Retina of vertebrates: an internal cell reserve for regeneration

The recent data were summarized concerning the presence in the retina of fish, amphibians and birds of additional sources of growth and regeneration, alternative to the already known sources, such as growth zone of eye, pigment epithelium, and cells--precursors of rods, and which are localized in the inner nuclear layer of retina. These sources are represented by as yet not finally identified oval small cells and cells of Muller glia. Both types of cells are capable of proliferating and producing precursors for various differentiated cells, including photoreceptors or their additional precursors. The current immunochemistry data are provided, which were obtained using markers of proliferation, proneural phenotype, and specific cell differentiation in the growing retina and in the retina after various damages. The regulatory mechanisms and methods of the stimulation of proliferation of the cells, which are sources of increase in the number and restoration of photoreceptors, interneurons, and glial cells of vertebrate retina, are discussed.