Human corneal basal epithelial cells express an embryonic stem cell marker OCT4

Purpose: Transcription factors act as molecular switches to activate or repress specific genes, which in turn control cellular phenotype. Transcription factor OCT4 is critical for self-renewal and maintenance of embryonic stem cells. OCT4 expression is down-regulated in all differentiated somatic cell types in vitro and in vivo. Our aim is to investigate whether the human corneal epithelium expresses OCT4. Materials and Methods: OCT4 protein was examined in nine human cornea specimens and in human testicular seminoma positive control samples by fluorescence immunohistochemistry. OCT4 mRNA was studied in human corneal epithelial as well as human embryonic stem cells (ESC). The RT-PCR products were further analyzed by DNA sequencing. Results: All of the corneas displayed nuclear staining patterns, limited to the corneal epithelial basal layer. The OCT4 positive staining cells resided mainly in the limbal epithelial basal layer, but some were also found in the peri-limbal and central corneal epithelial basal layers. OCT4 mRNA was detected in the epithelium of all human corneas and human ESC cells. Neither OCT4 mRNA nor protein was detected from negative controls. The sequencing analysis showed that the base sequences of PCR products were 99.17% similar to the human OCT4 gene. Conclusion: The basal layer of corneal epithelium expresses OCT4.