[The in vitro system in internal ear research].

The knowledge about in vitro culture of the embryonic inner ear dates back to the 1920's. During the following decades it was mainly the avian embryonic labyrinth which was used for organ culture. Emphasis was put on histological differentiation of individual cells and tissues. A poor morphogenesis/organogenesis was accepted. In the 1950's a very important field of research emerged which concerned the morphogenetic relationship between cells and tissues of different types. A great progress in basic understanding of in vitro conditions for normal and tumour tissues from mammalian species including man occurred during the 1960's. In the early 1970's this was applied to research on the cytodifferentiation and morphogenesis of the embryonic mammalian inner ear anlage. The organ culture techniques have been applied to studies mainly on the embryonic development of the mouse inner ear anlage but also to some extent on early postnatal development. In vitro studies on other species are few. The in vitro technique for inner ear studies has been evaluated with regard to morphology and to some extent biochemical parameters as phospholipid composition, the transport enzyme adenylate cyclase, etc. With the introduction of the organ culture technique for the inner ear of the mouse and guinea pig (higher vertebrates) many of the experiments earlier restricted to lower vertebrates performed in vivo could now be performed with great accuracy in vitro using higher vertebrates and under considerably better controlled conditions: neural induction, epithelio-mesenchymal interactions, neurotrophic interaction, "fate mapping", tissue interactions for normal morphogenesis and studies on especially vulnerable stages during inner ear development and applied research as e.g. ototoxicity. It must be emphasised that applications of the organ culture technique cannot give information on the systemic effects of an agent, only about its direct action on a given tissue.