Synchronization of the G1/S transition in response to corneal debridement

PURPOSE. This study's intention was to examine the progression of ocular su rface epithelium through the G1/S transition of the cell cycle after cornea l epithelial debridement. METHODS. Three-millimeter debridements were made in central rat cornea and allowed to heal 4 to 48 hours in vivo. Unwounded contralateral eves served as controls. Two hours before the animals were killed, 5-bromo-2-deoxyuridi ne (BrdU) was injected to detect S-phase cells. Incorporated BrdU was visua lized by indirect immunofluorescence microscopy, and expression of G1 cell- cycle markers cyclins D and E was examined by indirect immunofluorescence a nd immunoblotting. RESULTS. The number of BrdU-labeled cells in conjunctival, limbal, and peri pheral epithelium peaked at 28 hours after wounding (3.9-, 4.5-, and 3.2-fo ld increases, respectivily). In unwounded eyes. cyclin D showed diffuse cyt oplasmic localization with occasional basal cells exhibiting a nuclear loca lization while anti-cyclin E showed intense localization in limbal and conj unctival basal cells but only minimal labeling in corneal epithelium. Withi n 8 to 12 hours after wounding, the nuclei of most corneal basal cells outs ide the wound area sere bound intensely by anti-cyclins D and E. Immunoblot ting revealed that cyclin D and E protein levels increased 4.5- and 12.1-fo ld after mounding, respectively. Epithelium migrating into the wound area d id riot incorporate BrdU and did not exhibit nuclear localization of cyclin s D and E. CONCLUSIONS. Corneal epithelial debridement stimulates basal cells outside the wound area to synchronously enter the cell cycle. However, cells migrat ing to cover the wound area do not progress through the cell cycle. These d ata suggest a compartmentalization of the proliferative and migratory phase s of wound repair.