Corneal Stem Cells: Identification and Methods of Ex Vivo Expansion

Abstract

The discovery of corneal epithelial stem cells in the limbal basal epithelium, and their contribution to the homeostasis and renewal of the corneal epithelium, has supposed a tremendous breakthrough in ocular surface reconstruction, with limbal tissue graft transplantation providing for the first time a successful alternative to the transplantation of donor’s cornea in patients with limbal stem cell deficiency. More recent discoveries in the peripheral corneal stroma and endothelium layers of cells with stem/progenitor cells characteristics have opened up the promise of obtaining a supply of adequately differentiated cells for tissue engineering of corneal stromal and endothelial equivalents. Much applications based on the use of these corneal stem/progenitor cells are however still at the experimental stage, and their development will require to solve different challenges, such as optimizing their isolation and purification, improving their in vitro expansion, preserving their stem/progenitor phenotype in culture, and also defining the factors and signaling pathways which are required for their adequate differentiation. In this chapter, we recover past and current findings on the biological and molecular hallmarks of corneal layer-specific stem/progenitor cells, limbal epithelial stem cells, corneal stromal stem cells, and corneal endothelial progenitor cells and make emphasis on which are the different methods used for their isolation and ex vivo expansion.