The inner ear of mammals uses neurosensory cells derived from the embryonic ear for mechanoelectric transduction of vestibular and auditory stimuli (the hair cells) and conducts this information to the brain via sensory neurons. As with most other neurons of mammals, lost hair cells and sensory neurons are not spontaneously replaced and result instead in age‐dependent progressive hearing loss. We review the molecular basis of neurosensory development in the mouse ear to provide a blueprint for possible enhancement of therapeutically useful (...) transformation of stem cells into lost neurosensory cells. We identify several readily available adult sources of stem cells that express, like the ectoderm‐derived ear, genes known to be essential for ear development. Use of these stem cells combined with molecular insights into neurosensory cell specification and proliferation regulation of the ear, might allow for neurosensory regeneration of mammalian ears in the near future. BioEssays 28: 1181–1193, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

Neurosensory hearing loss is a growing problem of super‐aged societies. Cochlear implants can restore some hearing, but rebuilding a lost hearing organ would be superior. Research has discovered many cellular and molecular steps to develop a hearing organ but translating those insights into hearing organ restoration remains unclear. For example, we cannot make various hair cell types and arrange them into their specific patterns surrounded by the right type of supporting cells in the right numbers. Our overview of the topologically (...) highly organized and functionally diversified cellular mosaic of the mammalian hearing organ highlights what is known and unknown about its development. Following this analysis, we suggest critical steps to guide future attempts toward restoration of a functional organ of Corti. We argue that generating mutant mouse lines that mimic human pathology to fine‐tune attempts toward long‐term functional restoration are needed to go beyond the hope generated by restoring single hair cells in postnatal sensory epithelia. (shrink)