Mammalian cochlear supporting cells can divide and trans-differentiate into hair cells

Hair-cell regeneration Hearing loss in humans results from the loss of sensory hair cells in the organ of Corti. In mammals, these cells do not regenerate but in non-mammalian vertebrates such as birds, supporting cells adjacent to hair cells can trans-differentiate to regenerate lost hair cells. That raises the question of whether this capacity is entirely lost in mammals, or whether it remains latent. Using new methods to purify post-mitotic mouse supporting cells, White et al. show that these cells do retain the capacity to develop into mature hair cells in vitro. The signals for regeneration seem to be absent or inhibited in vivo. An age-dependent shift in supporting cells' ability to proliferate is associated with levels of the cyclin-dependent kinase inhibitor p27Kip1, suggesting a therapeutic avenue for regenerating damaged hair cells. The cover shows the organ of Corti from a transgenic mouse; hair cells are purple and supporting cells are fluorescence-tagged green.