Abstract
Abstract: :
Purpose: Diseases of the ocular surface can lead to loss of the corneal epithelial limbal stem cells. Without these progenitor cells, the normal corneal epithelium cannot reproduce and is quickly replaced with surface cells that are not transparent. Patients with bilateral disease must have allograft transplants requiring anti–rejection treatment. Allografts have an average survival of two years. In order to find a source of tissue less likely to result in graft rejection, the authors investigated the ability of human cord blood stem cells to differentiate into corneal epithelial cells. Methods: Cord blood stem cells were cultivated in a previously described corneal epithelial culture system, but without 3T3 fibroblasts. A 2 by 2 mm cadaver corneal epithelial limbal explant was cultured as a positive control in the same culture conditions. The resultant cell sheets for the cord blood stem cells as well as the corneal epithelial cells were analyzed by light microscopy with hemotoxylin and eosin and by immunohistochemistry for the corneal epithelial specific cytokeratin k3. Also, western blots were carried out for cytokeratin k3. Results: All cord blood samples had the same light micrographic morphology as the control corneal epithelium. While the corneal epithelium showed heavy uniform distribution of cytokeratin k3, all cord blood stem cell samples showed patchy and less vigorous expression. Both cultivated cord blood and corneal epithelial cells showed bands corresponding to cytokeratin k3 on western blot. Conclusions: Cord blood stem cells are capable of differentiation to an epithelial phenotype in a corneal epithelial culture system. The resultant cell sheet is morphologically indistinguishable from corneal epithelial cells. Cord blood stem cells are capable of expressing the corneal epithelial specific cytokeratin k3, but do not do so in the same uniform distribution as corneal cells.
Keywords: cornea: epithelium • anterior segment • cornea: basic science