Electron-microscopic localization of type II, IX, and V collagen in the organ of Corti of the gerbil.

The presence of types II, IX and V collagen was probed in the organ of Corti of the adult gerbil cochlea by use of immunocytochemistry at the light- and electron-microscopic levels. Type II collagen is found in the connective tissues of the osseous spiral lamina and spiral limbus. In the region of the sensory hair cells it is present in the tectorial membrane and antibodies bind to the thick unbranched radial fibers. Type IX collagen co-localizes with type II collagen in the tectorial membrane, where antibodies bind to the thick unbranched radial fibers. Type V collagen is present in the connective tissue of the spiral limbus, the osseous spiral lamina, the eighth nerve, and the tectorial membrane. In the tectorial membrane, the staining with antibodies to type V collagen is more diffuse than that seen for types II and IX collagen and antibodies to type V bind to the thin, highly branched fibers in which the thick fibers are embedded. The results indicate that collagens characteristic of cartilage are localized in the organ of Corti. Within the tectorial membrane, types II and IX collagen form heterotypic thick fibers embedded in a reticular network of type V collagen fibers. These collagens form a highly structured matrix which contributes to the rigidity of the tectorial membrane and allow it to withstand the physical stresses associated with transmission of the stimuli necessary for sensory transduction.