Despite their curious morphology prompting numerous hypotheses of their normal function, the root cells lining the cochlear outer sulcus have long evaded physiological characterization. A growing body of evidence now suggests that they regulate the solute content of the endolymph and/or the perilymph, and may be essential in safe-guarding the global homeostasis of the cochlea. Immuno-labeling experiments have demonstrated polarized expression of key ion transport proteins, and recent electrophysiological recordings have identified specific membrane conductances. These studies have painted a clearer picture of how this unusual cell type may contribute to the maintenance of sound transduction, and how they may be central to pathological processes associated with various forms of hearing loss.
This article is part of a Special Issue entitled “Annual Reviews 2013”.Highlights
▸ Outer sulcus root cells have morphological and functional features that show tonotopic variation. ▸ In low frequency coding regions they contact endolymph and likely absorb cations. ▸ In high frequency regions the basolateral membrane is specialized for K+ recirculation. ▸ Root cells may contribute to the cochlear response to stress. ▸ Root cell function may be adversely affected by numerous deafness gene mutations.