Degeneration followed by partial regeneration of the organ of Corti in deafness (dn/dn) mice.

The deafness mouse is a Mendelian recessive mutant which never hears and has no stimulus-related receptor or neural auditory responses. From birth through 12 days after birth (DAB), the organ of Corti develops normally as seen with light microscopy, except that the space of Nuel does not fully develop. The inner and outer hair cells are degenerating between 12 and 24 DAB and are gone by 45 DAB. As the hair cells degenerate, other cells of the organ of Corti become less recognizable, appear to collapse, and lose their identities as differentiated cells. By 45 DAB, from base to apex, the organ of Corti is composed of a low, roughly cuboidal epithelium with no distinguishing cell types; a hint of a tunnel of Corti remains at the apex. In the basal turn, the organ of Corti remains in this degenerated state through at least 460 DAB (senility for these mice). In the apical organ of Corti, considerable regeneration occurs between 45 and 90 DAB. By 90 DAB the apical turn of the organ of Corti has readily identifiable inner and outer pillar cells, inner and outer supporting cells, Hensen's cells, and Claudius' cells. A tunnel of Corti and space of Nuel are also present in the apex but there are no hair cells. Mechanisms are not known for either the degeneration or the regeneration.