Spontaneous Proliferation in Organotypic Cultures of Mouse Cochleae

Cells in mammalian cochleae virtually stop proliferation and exit cellular circle before birth. Consequently, hair cells and spiral ganglion neurons destroyed by ototoxic factors cannot be replaced through proliferative regeneration. However, substantial proliferation occurs in organotypic cultures of cochleae from postnatal mice. In the present study, we studied the time course of proliferative growth in cultures of mouse cochlea explants obtained from up to 12 postnatal days. The mitotic nature of this growth was confirmed by bromodeoxyuridine (BrdU) staining and expression of proliferation cell nuclear antigen (PCNA) evaluated with real–time quantitative polymerase chain reaction (RT–PCR). Similar growth time course was found in the cochlear explants of different postnatal ages. The new growth reached its maximum at around 2 days in culture followed by a slow–down, and virtually stopped after 5 days of culture. The possible mechanisms and the significance of this proliferation are discussed.