Tissue-regenerating, vision-restoring corneal epithelial stem cells

The cornea, the most anterior segment of the eye, provides us with exquisite vision. Unlike other vital tissues, it is poorly protected from the environment and is thus reliant on a self-renewal program to preserve integrity. This function is reserved for corneal epithelial stem cells located in the basal layer of the limbus, a narrow transition zone that segregates the peripheral cornea from the adjacent conjunctiva. Under physiological conditions, these cells replenish the corneal epithelium when mature or traumatized cells are lost. However, when the limbus is extensively damaged, stem cell activity is compromised, resulting in a condition known as limbal stem cell deficiency (LSCD). This disease is characterized by corneal neovascularization and persistent epithelial defects which impair vision. Over the past 20 years a myriad of treatment options have been developed for LSCD, most of which incorporate stem cell transplantation. Due to the disadvantages associated with the use of allogeneic and xenogeneic material, researchers are currently focusing on refining techniques involving autologous limbal tissue transplantation and are delving into the possibility that stem cells found in other organs can provide an alternative source of corneal epithelium. Determining where donor stem cells reside on the recipient's ocular surface and how long they remain viable will provide further insights into improving current therapeutic options for patients with LSCD.