Advances of research on endogenous retinal stem cells

The retinal neurons can not repair or regenerate once they are injured.Repairing the injured neurons by stem cell therapy is a hotspot in current study field.Endogenous stem cells exist in retina, which have the potential to restore retinal neural cells.Stimulating the endogenous retinal stem cells and using them to repair the injured retina has important research value and broad application prospects.It draws attention from neurobiology and ophthalmology researchers all over the world.The retinal regeneration ability of fish and amphibians is strong, while it is quite limited in birds and mammals.The retina regrowth character varies in different species.Ciliary marginal zone, retinal pigmented epithelial cells, and Müller cells are all potential cell sources for retinal regeneration.In fish, birds and mammals, the regenerated retinal neurons derived from Müller cells, while in amphibians they derived from RPE cells.The endogenous retinal stem cells need to be activated before they generated into retinal neurons.Researchers reported several methods to activate those cells, including using excitatory amino acid, growth factor, transcription factor, and intracellular signals.Here we reviewed the recent advances about retinal regeneration in different species including fish, amphibians, birds, and mammals; also the different source of endogenous retinal stem cells, including ciliary marginal zone, retinal pigmented epithelial cell, and Müller cell.Also, we reviewed the activation factors which could activate the endogenous retinal stem cells to proliferate and differentiate.