Abstract
Purpose: :
To investigate the expression of five human embryonic stem cell (hESCs) markers, alkaline phosphatase, SSEA-1, SSEA-4, Nanog, and Oct-3/4, in the limbal and corneal epithelial cells.
Methods: :
Frozen tissue sections were obtained from human sclerocornea tissues which were acquired from eye banks. Immunohistochemistry staining for five hESCs markers, alkaline phosphatase, SSEA-1, SSEA-4, Nanog, and Oct-3/4, were performed to evaluate their expression in the limbus and cornea. Double staining with putative limbal stem cell marker, ABCG2 and proliferation marker, Ki67 were done, respectively. The distribution of SSEA-4, Nanog and Oct-3/4 was further confirmed by reverse transcriptase PCR (RT-PCR).
Results: :
Alkaline phosphatase, and SSEA-1 were not expressed in the limbal and corneal epithelial cells, while alkaline phosphatase was present in the anterior limbal stroma. Oct-3/4, and Nanog were detected in both limbal and corneal basal and suprabasal epithelial cells. SSEA-4 was expressed at higher level in the limbal basal epithelial cells than in the cornea, while Ki67 was absent in the limbal basal epithelial cells, and present in the corneal and superficial limbal epithelial cells. The expression of Oct-3/4, SSEA-4 and Nanog was confirmed by RT-PCR.
Conclusions: :
The hESCs markers, Oct-3/4, Nanog and SSEA-4 were expressed in a subgroup of limbal and corneal epithelial cells, while alkaline phosphatase was detected in the anterior limbal stroma. Although their possible role in corneal epithelial cell differentiation is yet to be determined, the study suggests heterogeneity among epithelial cells even in the same anatomical location and possible existence of pluripotent or multipotent limbal stem cells.
Keywords: cornea: basic science • cornea: epithelium • immunohistochemistry