The glycocalyx of inner ear sensory and supporting cells

The ultrastructure of the glycocalyx of the sensory and the supporting cells of guinea pig inner ear was studied using the ruthenium red staining technique. The glycocalyx was found over the entire length of the stereocilia and the kinocilium of the sensory cells as well as over the entire apical surface of the supporting cells appearing as a fuzzy filamentous layer. The mechanism of sensory hair fusion and its relationship to glycocalyx in gentamicin treated animals was also studied. The sensory hair degeneration process started with a decrease or even a loss of glycocalyx ensued by a local attachment of neighbouring sensory hairs. These findings have led to two hypotheses about the function of the glycocalyx of the sensory hairs. Firstly the glycocalyx serves as anchoring structure for the mechanical coupling between the ciliary structures so that when a single hair in the bundle is deflected, all stereocilia and kinocilium within that bundle move in unison as a group. Secondly, because of the electronegativity of its acidic groups, the glycocalyx serves to maintain, by repulsion, a distance between adjacent cilia, preventing close contact and preventing the cell membranes from fusing.