Irreversible damage of cochlear sensory hair cells and nonsensory supporting cells causes permanent hearing loss because the sensory epithelium cannot repair or regenerate itself postnatally. Active Wnt/β-catenin signalling marks many endogenous stem cells and Roel Nusse, Alan Gi-Lun Cheng and colleagues now report () that tympanic border cells (TBCs), which lie beneath the sensory epithelium, are Wnt responsive and can act as progenitors for sensory epithelial cells in the postnatal mouse cochlea. The researchers show that transient but robust Wnt signalling and proliferation exists in TBCs during the first 3 postnatal weeks and report that Wnt agonists stimulate the proliferation of TBCs in cochlear explants. Moreover, TBCs that express the Wnt target gene Axin2 can generate new hair cells and supporting cells in vivo and in vitro. The researchers suggest, therefore, that TBCs serve as a reservoir of cells for the intricate organisation of the cochlea during early postnatal development and that quiescent TBCs in the adult cochlea might represent targets for regenerative therapy.
