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Effects of mechanical trauma to the human tympanic membrane: an experimental study using transmission electron microscopy

Abstract Hypothesis: To examine the cellular events following induced superficial lesions of the human tympanic membrane (TM). Such information could lead to enhanced appreciation of repair mechanisms and novel strategies to restore TM perforations. Background: Persistent perforation of the TM in chronic otitis media is a major global health problem and frequently necessitates surgical intervention. Most TM perforations heal spontaneously and swiftly, but sometimes healing fails. The underlying mechanisms and the reason for incomplete repair are often elusive, although some mechanisms have been proposed. Methods: Here, five healthy adult human TMs were sampled during vestibular schwannoma surgery. Three days before harvesting, three TMs were superficially lesioned, including the epithelial and sub-epithelial layers, using a needle and two TMs served as controls. Light and transmission electron microscopy were performed. Results: Surrounding lesion showed distinct ultrastructural changes. This included a keratinocyte frontier with electron-dense cells with abundant ribosomes and nuclei metamorphosis. Beneath, were activated fibroblasts and invaded/transformed free cells and signs of increased transcellular activity of adjacent blood vessels. Conclusions: The study describes dynamic morphological events of a human lesioned TM. The human model may be used for further investigations and understanding of TM healing mechanisms.