Postnatal production of supporting cells in the chick cochlea.

The auditory receptor organ in birds, the basilar papilla, is mitotically active after acoustic overstimulation or pharmacological insult and is capable of self-repair. The damaged epithelium is repopulated with new hair cells and supporting cells. The cell production that underlies this regenerative self-repair is believed to be a response evoked by damage in populations of cells that normally become mitotically quiescent even before hatching. In contrast, regeneration in the vertebrate nervous system is often correlated with continued or recent neurogenesis in the tissue concerned. The hypothesis that there may be ongoing postnatal production of cells in the normal avian basilar papilla was investigated. Autoradiographic analysis of tritiated-thymidine-injected animals was used to look for the existence of newly formed cells in the basilar papilla of normal posthatch chickens. Several types of supporting cells, namely, organ supporting cells, border cells and hyaline cells, are produced postnatally in the normal chicken. Typically, they are added interstitially to the apical (distal) half of the basilar papilla.