FIBRONECTIN-LIKE IMMUNOREACTIVITY OF THE BASILAR-MEMBRANE OF CELLOIDIN-EMBEDDED HUMAN TEMPORAL BONE SECTIONS

Dysfunction of the mechanical properties of the basilar membrane is a potential cause of presbycusis. In cases of minimal sensorineural or strial degeneration it is believed to play a major role. The membrane has been shown to be partly composed of fibronectin. Fibronectin immunoreactivity is diminished in aged rats. Mesothelial cells line the perilymphatic surface of the membrane and are reduced in number in the aged rat cochlea. Fibronectin immunoreactivity was examined in human temporal bone sections (6 months to 92 years old). Hematoxylin and eosin stained sections (17 to 97 years) were used to count the number of mesothelial per radial section of the basilar membrane in the upper middle turn. Fibonectin immunoreactivity was demonstrable in the human cochlea, but was not reduced, even in the eldest cases examined. The number of mesothelial cells was reduced, however, and was related to the age of the individual, but not to the clinical diagnosis or audiogram shape. These two factors do not, therefore, appear to give rise to hearing losses associated with presbycusis.