Post-traumatic survival and recovery of the auditory sensory cells in culture.

Following mechanical injury in organotypic cultures, auditory hair cells show the ability to survive and to initially reform their apical specializations, cuticular plates and stereocilia, but none show incorporation of tritiated thymidine, the mitotic marker. Disruption of the reticular lamina and local injury to hair cell cuticular plates induces proliferation of supporting cells. The regenerating apices of inner hair cells are wrapped by the cells of the inner spiral sulcus and the inner phalangeal cells, while those of outer hair cells are wrapped by the phalangeal processes of Deiters' cells and outer spiral sulcus cells. Some of these hair cells subsequently resurface with newly formed tops. Hair cells that lose contact with the surface of the organ remain buried--but alive--deep within the epithelium. Our study provides evidence that the mammalian organ of Corti responds to injury not by the formation of new sensory cells but by the recovery of the pre-existing postmitotic hair cells.