Expression of Intermediate Filament Proteins in the Adult Human Cochlea

Abstract

The immunohistochemical localization of intermediate filament proteins was studied in frozen sections of chemically fixed, nondecalcified adult human cochleas. Cytokeratins were found in all epithelial cells lining the cochlear duct (including most supporting cells of the organ of Corti) but were absent in the hair cells. Neurofilament proteins were present in the nerve endings at the hair cells, in the neural bundles, and in the ganglion cells. Vimentin staining occurred in most of the supporting structures and was roughly complementary to the regions showing cytokeratin staining and neurofilament staining. However, the region of the spiral prominence and outer sulcus, as well as the pillar cells and Deiters' cells in the organ of Corti, showed coexpression of vimentin and cytokeratins. No definite immunostaining was observed with antibodies to desmin and glial fibrillary acidic protein.

Identification with a recombinant antibody of an inner-ear cytokeratin, a marker for hair-cell differentiation

“…Although they provide mechanical stability to cells, cytokeratins probably serve other roles as well, including the organization of organelles and the nucleus (15)(16)(17). Cytokeratins, including cytokeratins 8, 9, and 19 and otokeratin, are known to occur in cells of the inner ear (13,(18)(19)(20)(21)(22)(23). A definitive subclassification of our inner-ear cytokeratin within the type II cytokeratin family is difficult because of the sequence conservation within this family and the lack of anuran cytokeratin sequences to use for comparison.…”

Immunologically Defined Component of the Circumferential Ring Around the Cuticular Plate in Mammalian Hair Cells

“…Supernatants from 22 uncloned hybridomas were screened and all of them appeared to contain anti bodies against cytoskcletal structures and most of them labelled hair cells. The struc tures most commonly labelled in hair cells were the circumferential ring around the cu ticular plate (7), the cuticular plate (3) and the lateral cortex (8). A hybridoma cell line that secreted class IgM antibodies (CAR) to the circumferential rings of both inner and outer hair cells was cloned.…”

“…In the organ of Corti, particularly across the epithelial surface, there is a rich diversity of actin filaments [3][4][5][6], microtubules [7] and intermediate filaments [8] that are assembled by various specific cross-linking proteins [9][10][11], Hair cells possess relatively few microtu bules or intermediate filaments, but they have evolved several distinct arrays of actin fila ments [12]. In chick hair cells, for example, these include a paracrystalline bundle crosslinked by fimbrin in the stereocilia, a complex gel cross-linked by spectrin in the cuticular plate, and a circumferential bundle crosslinked by a-actinin on the cytoplasmic face of the adhesion belt (zonula adherens) [9], Mam malian outer hair cells possess a fourth array in the lateral cortex that is highly specialised and related to the mechanism of electro mechanical transduction [13], This 'cortical lattice' is composed of circumferential actincontaining filaments that arc cross-linked along the cell axis by spectrin filaments [14,15].…”

Keratin filament deployment and cytoskeletal networking in a sensory epithelium that vibrates during hearing

“…Although antibodies to keratins bind to supporting cells in those mammals that have been investigated (humans, guinea pigs, and rats), no binding to the adjacent hair cells has been detected [Raphael et al, 1987;Bauwens et al, 1991b;Kuipers et al, 1991]. Keratin filaments are important, and sometimes essential, for maintaining the mechanical properties of epithelia and their resistance to mechanical stress [McLean and Lane, 1995;Fuchs and Cleveland, 1998].…”

“…Staining of supporting cells by anti-keratins [Bauwens et al, 1991b;Kuipers et al, 1991] is sometimes most intense in regions where compact fibrous meshworks Tucker et al, 1995] that include non-muscle actin isoforms [Slepecky and Savage, 1994] are situated at the ends of microtubule bundles. It is unknown whether these meshworks also include keratin filaments.…”