Repair of the wounded guinea pig tympanic membrane: organization of filamentous actin and spatial cellular reorganization.

Since the role of the epithelial cell in the repair of the wounded tympanic membrane is not well understood, the epithelial cell layers were examined using rhodamine phalloidin to localize F-actin in situ following a full-thickness traumatic perforation. The change in shape of the epithelial cells and the morphological changes in F-actin were characterized. The mucosal cells were remarkably resistant to wounding and their morphology and F-actin distribution remained unchanged. Within 24 hours following perforation, basal cells were prominently stained adjacent to the perforation, whereas the remainder of the drum showed fainter staining similar to non-wounded drums. The basal cells showed a minor shape change in the direction of movement of the surface keratin. By three days, the dense peripheral F-actin staining of basal cells was prominent throughout the entire drum. The suprabasal cells demonstrated a marked shape change by 24 hours following the injury. The normal cobblestone pattern disappeared and cells elongated and were aligned towards the perforation. This occurred first adjacent to the perforation, and by three days re-orientation was present over the entire tympanic membrane. A few fine stress fibers appeared in the suprabasal cells. Histological and electron microscopic evaluation of the areas away from the perforation did not, however, show inflammation or disruption. By one week these changes were resolving and by two weeks the drum, with the exception of the cells in the area of the healed perforation, had returned to normal. The results are discussed with respect to the role of the various cell types in the migratory aspect of tympanic membrane wound repair.