Histology of the Healing Tympanic Membrane Following Perforation in Rats

Objectives/Hypothesis: The aim of this study was to provide a detailed cytological account on the healing tympanic membrane (TM) over 14 days and to complement existing research into TM wound healing. Study Design: The study is a prospective cohort study of 19 male Sprague-Dawley (Rattus norvegicus) rats. Methods: Rat TMs were perforated using a sterile needle and sacrificed at time points during the 14 days following perforation. Results: The healing of the TM resembles cutaneous wound healing except that the TM is unique in the lack of a supportive matrix beneath the regenerating epithelia. This prevents the influx of reparative cells and nutrients and the in growth of the usual fibroblastic reaction. Conclusions: TM wound healing contrasts with cutaneous wound healing in that keratinocytes are the first cells to close the wound and not the last. A keratin scaffold may not be important in the healing process. The malleus plays a crucial role in the healing of the TM and is the site of significant mitotic activity during the healing process. Migration across layers of the TM appears to account for the closure of the perforation.