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T. Nagasaki, J. Zhao; Epithelial Stem–Like Cells in the Central Cornea of Young Mice . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3031.
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Corneal epithelial stem cells are thought to be present mostly in the limbus region. However, their presence in the central cornea has not been rigorously tested. This study was initiated to examine a possibility that epithelial stem cells are present in the central cornea of young mice.
Ubiquitous GFP mice were used. To determine whether central epithelial cells are sufficient to maintain epithelial homeostasis, limbal epithelial cells were removed completely by mechanical scraping, and the cornea was monitored to document its clarity, centripetal epithelial cell movement, goblet cells, and vascularization. For epithelial scraping, corneal surface was labeled with a nuclear dye, DAPI, and the scraping was carried out under a stereo fluorescence microscope to observe DAPI–labeled cells in real time, which ensured complete removal of limbal epithelial cells (and some bulbar conjunctival cells in the immediate vicinity). To determine cell movement, epithelial GFP patterns were tracked by in vivo time–lapse fluorescence microscopy for up to one year after the injury. Corneal angiography was carried out after intraperitoneal injection of sulforhodamine 101.
When the entire corneal epithelium including the limbus area was removed in 3–week or 6–week old mice, the cornea became conjunctivalized with concomitant vascularization. However, when only the limbal epithelium was removed from mice of the same age group, keeping the central cornea intact, the cornea maintained its clarity without a sign of conjunctivalization for at least one year, suggesting that central epithelial cells can drive and sustain epithelial homeostasis of the entire cornea in the absence of limbal epithelial cells. Centripetal movement of epithelial cells was observed in these corneas as in a normal cornea, suggesting that some of the central corneal cells moved to the limbus and functioned as stem cells.
The epithelium of the central cornea in a young mouse, 6 weeks or younger, contains cells that move to the limbus and function as epithelial stem cells when limbal stem cells are removed. This suggests that either (1) epithelial stem cells are present in the central cornea of a young mouse, or (2) the environment of the limbus confers stem cell properties to central corneal epithelial cells that move into the area.
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