Abstract
Purpose:
Continuous regeneration of stem cells is known to be essential for maintaining the life-long homeostasis of any types of cells in the body of animals. In the stem cells of ocular surface epithelia, several positive and negative markers have been reported. Recent studies have shown that stem cells are adapted to hypoxic conditions with slow cell cycling, low transcriptional activity, lower mitochondrial respiration, and higher glycolysis for the generation of adenosine-5'-triphosphate (ATP). The purpose of this present study was to report a new marker for corneal epithelial stem cells based on low transcriptional activity.
Methods:
Corneal tissue samples obtained from humans, rabbits, and mice were cryo-embedded, sliced into thin sections, fixed, and immunostained with antibodies against the phosphorylated serine-2 of the RNA polymerase II (RNAP II), a marker of activated transcription, as well as several positive or negative markers of corneal epithelial stem cells such as N-cadherin, p63, and keratin 12.
Results:
In all of the tissue samples, a decreased level of phosphorylation at the serine-2 residue of the RNAP II was found at the basal cells of the limbal epithelium. Immunostaining with antibodies against the above-described established markers for corneal epithelial stem cells proved that those cells were, in fact, corneal epithelial stem cells.
Conclusions:
The findings of this study show that phosphorylated serine-2 of the RNAP II is a new negative marker for corneal epithelial stem cells. Corneal epithelial stem cells may have a general feature of stem cells in terms of low transcriptional activity.
Keywords: 721 stem cells •
738 transcription