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Eui–Hong Chung, Audrey E. K. Hutcheon, Nancy C. Joyce, James D. Zieske; Synchronization of the G1/S Transition in Response to Corneal Debridement. Invest. Ophthalmol. Vis. Sci. 1999;40(9):1952-1958.
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purpose. This study’s intention was to examine the progression of ocular
surface epithelium through the G1/S transition of the cell cycle after
corneal epithelial debridement.
methods. Three-millimeter debridements were made in central rat cornea and
allowed to heal 4 to 48 hours in vivo. Unwounded contralateral eyes
served as controls. Two hours before the animals were killed,
5-bromo-2-deoxyuridine (BrdU) was injected to detect S-phase cells.
Incorporated BrdU was visualized by indirect immunofluorescence
microscopy, and expression of G1 cell-cycle markers cyclins D and E was
examined by indirect immunofluorescence and immunoblotting.
results. The number of BrdU-labeled cells in conjunctival, limbal, and
peripheral epithelium peaked at 28 hours after wounding (3.9-, 4.5-,
and 3.2-fold increases, respectively). In unwounded eyes, cyclin D
showed diffuse cytoplasmic localization with occasional basal cells
exhibiting a nuclear localization, while anti–cyclin E showed intense
localization in limbal and conjunctival basal cells but only minimal
labeling in corneal epithelium. Within 8 to 12 hours after wounding,
the nuclei of most corneal basal cells outside the wound area were
bound intensely by anti–cyclins D and E. Immunoblotting revealed that
cyclin D and E protein levels increased 4.5- and 12.1-fold after
wounding, respectively. Epithelium migrating into the wound area did
not incorporate BrdU and did not exhibit nuclear localization of
cyclins D and E.
conclusions. Corneal epithelial debridement stimulates basal cells outside the wound
area to synchronously enter the cell cycle. However, cells migrating to
cover the wound area do not progress through the cell cycle. These data
suggest a compartmentalization of the proliferative and migratory
phases of wound repair.
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