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H. Liu, J. Zhang, C.-Y. Liu, W. W. Kao; Corneal Epithelial Progenitors Can Maintain Corneal Surface Homeostasis for a Limited Period of Time Following Limbal Deficiency. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6369.
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© ARVO (1962-2015); The Authors (2016-present)
At birth (postnatal day 0, P0), basal cells of mouse corneal epithelium that derive from surface ectoderm remain undifferentiated and do not express keratin 12. These cells undergo differentiation to become K12 positive, postnatally. In present studies, we examined the possibility whether the K12-negative cornea epithelial progenitor cells can maintain corneal epithelium integrity following limbal epithelium debridement.
Corneal limbal epithelial debridement was performed with a Tet-On mouse model of K12rt/wt/Tet-O-Cre/RosamTmG/wt mice in which corneal epithelial cells expressed membrane tomato-red fluorescence (mT) without doxycycline (Dox) induction but expressed membrane EGFP (mG) due to the excision of LoxP-flanked mT by Cre-recombinase upon Dox-induction. Following the debridement of total limbal epithelium, one group of experimental animals was continuously induced; another experiment, Dox-induction was interrupted after limbal debridement. After limbal epithelial debridement, the healing was examined using a ZEISS fluorescent stereomicroscopy. After 6 weeks, corneas excised from the experimental mice were subjected to histochemical analysis and immunofluorescent staining with anti-K12 and K13.
Corneal epithelium of adult K12rt/wt/Tet-O-Cre/RosamTmG/wt displayed red fluorescence without Dox, but strong green fluorescence in a unique spiral pattern upon Dox induction. Following total limbal epithelial debridement, central K12-positive green corneal epithelial cells migrated outwards to cover the wounded region in 72 hours. However, the mG-positive cells lost their original spiral pattern but exhibited a mosaic pattern on corneal surface and the density of the mG-positive cells dramatically decreased at 6 weeks after total limbal epithelial wound. Immunofluorescent staining with anti-K12 and K13antibodies revealed that both K12 and K13 were positive in corneal region. In addition, goblet cells ectopically appeared on the corneal surface, indicating the conjunctivalization of the corneal surface.
Removal of limbal barrier allows the migration of K12-positive corneal epithelial cells onto denuded corneal limbal surface and maintains corneal epithelium integrity in initial stage after limbal epithelial deficiency; thereafter conjunctival epithelial cells invade and replace corneal epithelial cells, which are likely attributed to the exhaustion of those K12-negative corneal epithelial progenitor cells.
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