Induction of Epithelial Progenitors In Vitro from Mouse Embryonic Stem Cells and Application for Reconstruction of Damaged Cornea in Mice

Severe ocular surface diseases and injuries cause loss of the corneal limbal epithelium, leading to re-epithelialization by bulbar conjunctival cells, resulting in vascularization of the cornea, conjunctival scarring, and loss of visual acuity. In this study, the optimal culture condition for induction of differentiation of epithelial progenitor cells from embryonic stem (ES) cells was determined for use in transplantation to damaged cornea in mice. Mouse ES cells were cultured on Petri dishes coated with several extracellular matrix proteins, and the markers for epithelial cells were analyzed with RT-PCR and Western blot analysis. The optimal condition for induction of epithelial progenitor cells was determined, and the progenitors were transplanted onto mouse eyes with corneal epithelia that had been damaged by exposure to n-heptanol. Epithelial progenitors were successfully induced by culturing mouse ES cells on type IV collagen for 8 days. These progenitors expressed keratin (K)12, which is specific to corneal epithelial cells, and cell surface CD44 and E-cadherin, both of which are essential in corneal epithelial wound healing. Complete re-epithelialization of the corneal surface occurred within 24 hours after transplantation. The resultant corneal epithelial cells expressed markers of the grafted cells, and no teratomata were observed during the follow-up period. Epithelial progenitors were successfully induced in vitro from ES cells and were applicable as grafts for treating corneal epithelial injury. ES cells may become an unlimited donor source of corneal epithelial cells for corneal transplantation and may restore useful vision in patients with a deficiency of limbal epithelial cells. This is an important first trial toward assessing the use of ES cells to reconstruct corneal epithelial cells.