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Nick Di Girolamo, Adam Wilkinson, Naomi Kawaguchi, Carolyn L Geczy; Identification and Partial Characterization of Rare S100A8 and S100A9 Expressing Cells in the Human Limbal Stroma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1939.
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© ARVO (1962-2015); The Authors (2016-present)
A healthy transparent cornea is necessary for exquisite vision. The corneal epithelium is constantly renewed through the replenishing actions of limbal epithelial stem cells. However, less is known about the cellular composition of the stroma and how this layer is maintained. S100A8 and S100A9 have been detected in the healthy cornea and are implicated in regulating inflammatory processes on the ocular surface. We aimed to identify a unique cell type expressing these proteins in corneal tissue.
Neutrophils from human peripheral blood were prepared as positive controls for immunocytochemistry. Immunofluorescence was used to identify S100A8 and S100A9 in pterygia (n=3) and healthy fetal and adult human corneas (n=12); some specimens were co-stained with antibodies to CD34, CD68, and CD105.
S100A8 and S100A9 reactivity was confirmed in neutrophils and found in epithelial cells and intravascular neutrophils in pterygium specimens. In normal human fetal and adult corneal specimens superficial epithelia stained intensely for S100A8 and S100A9. Interestingly, a rare population of S100A8 and S100A9 positive cells were identified in the stroma; predominantly in the limbal region in adult tissue and represented 0.25% and 0.4% (respectively) of the total stromal cell population/tissue section. Furthermore, these cells were CD34 and CD68 negative but a proportion co-expressed CD105, a marker of mesenchymal stem cells.
The discovery of a rare population of S100A8 and S100A9 cells (some of which could be mesenchymal stem-like cells) in the limbal zone is a novel finding that has potential implications for cell renewal, differentiation and immune suppression particularly in a region of the ocular surface which is vulnerable to infection, inflammation and tumorigenesis.
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