Ocular epithelial transplantation: current uses and future potential

Visual loss may be caused by a variety of ocular diseases and places a significant burden on society. Replacing or regenerating epithelial structures in the eye has been demonstrated to recover visual loss in a number of such diseases. Several types of cells (e.g., embryonic stem cells, adult stem/progenitor/differentiated epithelial cells and induced pluripotent cells) have generated much interest and research into their potential in restoring vision in a variety of conditions: from ocular surface disease to age-related macular degeneration. While there has been some success in clinical transplantation of conjunctival and particularly corneal epithelium utilizing ocular stem cells, in particular, from the limbus, the replacement of the retinal pigment epithelium by utilizing stem cell sources has yet to reach the clinic. Advances in our understanding of all of these cell types, their differentiation and subsequent optimization of culture conditions and development of suitable substrates for their transplantation will enable us to overcome current clinical obstacles. This article addresses the current status of knowledge concerning the biology of stem cells, their progeny and the use of differentiated epithelial cells to replace ocular epithelial cells. It will highlight the clinical outcomes to date and their potential for future clinical use.