ABSTRACTS FROM THE ANNUAL MEETING OF THE SURGICAL RESEARCH SOCIETY OF AUSTRALASIA, 2003 ST VINCENT'S HOSPITAL, MELBOURNE, AUSTRALIA The human tympanic membrane: preliminary studies in tissue engineering. Anandacoomaraswamy KS , Thamrin C, Eikelboom RH, Then CM, Atlas MD. Otolaryngology Department, The University of Western Australia, Perth Introduction: The function of the tympanic membrane (TM) in transferring energy to the middle ear is largely due to the cellular arrangement. Three layers are distinctly recognized, namely the outer epidermal, middle lamina propria and inner mucosal layer. To maximize the functional hearing outcomes after tympanoplasty a tissue-engineered TM must closely replicate the normal human TM. The rupture pressure of the TM is an indicator of tympanic membrane strength. The mean rupture pressure of human TMs is 1.2-1.6 atm, which is significantly higher than measured in previous animal studies. Two studies were undertaken as part of a project to tissue engineer a human TM. Methods: TMs were obtained from patients having surgery where the drum was sacrificed. TM structure was examined using light and electron microscopy. The TMs of nine porcine temporal bone specimens were ruptured by a calibrated pressure delivery system. Results: Our study is consistent with previous studies showing the outer radial and inner circular fibres of the lamina propria, the keratinising stratum corneum with underlying stratum granulosum, stratum spinosum, and stratum basale layers in the epithelium, and the simple cuboidal cells in the mucosa. The rupture pressure of the porcine TM was measured at 1.2 ± 0.3 atm. Conclusions: Successful tissue engineering of a TM will require further work on structure and function. Immunohistochemistry will be performed to determine cytokeratin expression and collagen types. The mean rupture pressure in pigs is comparable to humans, and represents a suitable animal model for testing our tissue engineered TMs.