Disruption of the basement membrane after corneal debridement

PURPOSE. TO determine whether the native basement membrane left behind afte r manual debridement 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 debridement 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 bord er. Unwounded corneas served as control specimens. At each time point, conf ocal immunofluorescence microscopy was used to localize several proteins fo und in the basement membrane including laminin-5, entactin, and perlecan. I n addition, ultrastructural studies were performed using transmission elect ron microscopy (TEM) to assess the basement membrane zone (Bh IZ) of the co rneas 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 litt le 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 mic roscopy showed patches along the denuded corneal stroma where there was a p artial or complete loss of basement membrane markers at the BMZ. TEM confir med that the lamina densa was partly or completely absent along the anterio r 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 parti ally disassembled in response to manual debridement wounds when re-epitheli alization took more than 24 hours. Regulated disassembly of the epithelial basement membrane probably plays a role in the healing of large-diameter de bridement wounds.