Disruption of the basement membrane after corneal débridement.

PURPOSE: To determine whether the native basement membrane left behind after manual débridement wounding is retained throughout healing in the Balb/c mouse.
METHODS: Mouse corneas were subjected to either 1.5 mm (small) or limbus-to-limbus (large) epithelial débridement wounds and allowed to heal for times ranging from 12 hours to 3 days. For the larger wounds, care was taken to leave an approximately 0.5-mm zone of epithelial cells near the limbal border. Unwounded corneas served as control specimens. At each time point, confocal immunofluorescence microscopy was used to localize several proteins found in the basement membrane including laminin-5, entactin, and perlecan. In addition, ultrastructural studies were performed using transmission electron microscopy (TEM) to assess the basement membrane zone (BMZ) of the corneas at various times after injury.
RESULTS: The smaller (1.5-mm) wounds healed within 24 hours, and the larger wounds healed at approximately 48 hours. Both wound sizes healed with little scarring or neovascularization. At all time points after 1.5-mm wounding, immunofluorescence confocal microscopy and TEM showed that both basement membrane proteins and the lamina densa were retained at the BMZ throughout healing. For the larger wounds, at time points after 24 hours, confocal microscopy showed patches along the denuded corneal stroma where there was a partial or complete loss of basement membrane markers at the BMZ. TEM confirmed that the lamina densa was partly or completely absent along the anterior surface of the exposed cornea at time points of more than 24 hours after the larger wounds.
CONCLUSIONS: The denuded epithelial basement membrane was shown to be partially disassembled in response to manual débridement wounds when re-epithelialization took more than 24 hours. Regulated disassembly of the epithelial basement membrane probably plays a role in the healing of large-diameter débridement wounds.