Identification of factors regulating differentiation and growth of limbal stem cells for corneal surface regeneration

Abstract

AbstractPurpose To identify factors which are produced by damaged corneal epithelium and which control proliferation and differentiation of limbal stem cells (LSC).Methods The central cornea in the mouse was mechanically damaged and the cornea or limbal tissue was excised at different time intervals after injury. The expression of genes for a number of growth and differentiation factors in the cornea or limbus was determined by real‐time PCR. The effects of these factors on the growth and differentiation of LSC in vitro was tested.Results It was found that the expression of a number of genes in the central cornea was significantly enhanced already 3 or 6 hours after the cornea damage. Insulin‐like growth factor I (IGF‐I) which is strongly upregulated shortly after injury, was identified as the main factor responsible for LSC differentiation into cells expressing cytokeratin K12, a marker of corneal epithelial cells. Furthermore, IGF‐I enhanced expression of its own receptors in LSC, but it had no effect on LSC proliferation. Another two factors produced by the corneal epithelium, fibrocyte growth factor (FGF) and epidermal growth factor (EGF), supported LSC proliferation without effect on their differentiation.Conclusion IGF‐I was identified as the main factor inducing differentiation of LSC into cells expressing corneal epithelial cell markers. The proliferation of these cells was supported by FGF and EGF.