Regulation and clinical implications of corneal epithelial stem cells

The corneal epithelium is known to have a rapid self-renewing capacity. The major advance in the field of corneal epithelial cell biology in the last decade is the establishment of the location of corneal epithelial stem cells at the limbus, i.e., the junctional zone between the cornea and the conjunctiva. This concept has helped explain several experimental and clinical paradoxes, produced a number of important clinical applications, and spawned many other research studies. This unique enrichment of epithelial stem cells at a site anatomically separated from their transient amplifying cells makes the ocular surface an ideal model to study the regulation of epithelial stem cells. The present review includes data from more recent studies and lays out other areas for future investigation, especially with respect to the role of apoptosis and cytokine dialogue between limbal epithelial stem cells and their stromal microenvironment.