[The healing process of tympanic membrane perforations in rats]
Hanna Zajączkiewicz1, Elżbieta Hassmann-Poznańska1, Bożena Skotnicka1
1Klinika Otolaryngologii Dziecięcej UM w Białymstoku, Kierownik: prof. dr hab. Elżbieta Hassmann-Poznańska, Białystok, Polska.
Introduction:
Tympanic membrane (TM) perforations are commonly seen in clinical practice as a result of trauma or in the course of otitis media. The TM is a unique structure suspended in air which makes its healing processes different than in the skin wounds. The aim of the study was otoscopical and histological evaluation of the rat's TM healing process.
Material And Methods:
56 male Wistar rats were used for the study. Fifty of them had TMs perforated bilaterally using CO2 laser, additional 6 served as a controls. The animals were sacrificed on either day 1, 2, 3, 6 and 10 post injury. Process of healing was assessed otoscopicaly, subsequently TM were dissected and processed for histological evaluation.
Results:
At day 6 after perforation half and on day 10 all of TM were healed. On the first day, in histological evaluation, focal thickening of the epithelial layer was observed at some distance from the edge of perforation, on the side of annulus. On the following day proliferation of epithelium covering outer surface of TM on the side of the malleus handle and annulus was clearly visible. An eosinophilic mass containing macrophages and granulocytes was seen in front of the migrating epithelium. On day 3-6 migrating epithelium reached the edge of perforation. Proliferation of the connective tissue layer followed the epithelium.
Conclusions:
The present results indicate that the squamous epithelium covering the outer surface of TM constitutes the first layer which restores continuity of TM. The proliferation of the connective tissue occurs in the direct vicinity of the proliferating and migrating epithelium.
