Age-Related Degeneration of the Organ of Corti in Two Genotypes of Mice

Abstract

Degenerative changes in the organ of Corti were investigated in two genotypes of mice, CBA/Ca (moderate age-related late-onset hearing loss) and C57BL/6J (spontaneous early-onset auditory deterioration), ranging in age from 1 to 21 months (C57BL) and from 1 to 33 months (CBA). Light, transmission and scanning electron microscopes were used for qualitative and quantitative analyses. Alterations of deterioration in the CBA-mouse cochlea showed a late-onset loss of hair cells, lipofuscin in the outer hair cells (OHCs), giant stereocilia on the inner hair cells and elevated pillar heads. In C57BL mice, the primary lesions of the organ of Corti include early damage of stereocilia on OHCs, missing OHCs, and a ruptured reticular lamina. Giant cilia and elevated pillar heads were not evident in C57BL mice. In the aged C57BL mouse cochlea, the whole organ of Corti was collapsed and replaced by the supporting cells, whilst in the oldest CBA mice, completely normal-looking OHCs still remained even in severely deteriorated areas of the organ of Corti. The results indicate that the patterns of degeneration of the organ of Corti are different between CBA/ Ca and C57BL/6J mice, probably under the control of different genes.

Inner ear pathology and loss of hearing in estrogen receptor-β deficient mice

“…1A). Hearing thresholds in WT mice changed with age in a similar manner to that previously reported for C57BL/6J mice with a progressive hearing loss (Li & Hultcrantz 1994).…”

Age-related auditory pathology in the CBA/J mouse

“…Different strains show widely different patterns of age-related changes and in some of these strains distinct loci have been associated with accelerated hearing loss. CBA/J exhibit minimal hearing loss by 18 months of age but others such as C57BL/6, BALB/cJ and DBA/2J show significant deficits already between three and eight months of age (Li et al, 1991;Li et al, 1994;Spongr et al, 1997). Such strains may not reflect a normal biological aging process since the accelerated hearing loss correlates with the presence of pre-disposing genetic variants, including an ahl locus on chromosome 10, the Cdh23 ahl allele (Johnson et al, 1997;Johnson et al, 2000;Noben-Trauth et al, 2003).…”

“…"CBA" mice have been tested for some aspects of age-related hearing loss in earlier studies (Li et al, 1991;Li et al, 1994;Spongr et al, 1997), but past results may not pertain to currently available mouse colonies. Some studies combine CBA/J with CBA/CaJ (Spongr et al, 1997) while others (e. g., Henry and Chole, 1980) date back several decades.…”

Age-related hearing loss in the Fischer 344/NHsd rat substrain

“…The CBA/Ca mouse retains most of its hearing sensitivity up to 18 months of age, after which hearing declines progressively beginning in the high frequencies and moving to the low frequencies (Li and Borg, 1991). Underlying the loss of hearing sensitivity late in its lifespan, the CBA/Ca mouse undergoes progressive loss of OHC and IHC (Li and Hultcrantz, 1994;Spongr et al, 1997). The C57/BL6 mouse has been used as a model for accelerated ARHL.…”

“…The C57/BL6 mouse demonstrates a much more rapid onset of hearing loss and more rapid decline than the CBA/Ca mouse (Li and Borg, 1991). Hair cell degeneration also happens more rapidly, with potentially complete loss of hair cells by one year of age (Li and Hultcrantz, 1994;Spongr et al, 1997). In addition to their use as a model for sensory ARHL, mouse strains have also shown evidence of spiral ganglion cell degeneration (Saitoh et al, 1994;Dazert et al, 1996), although it is unknown if the pathology is indicative of neural ARHL, or if it is secondary to the loss of hair cells.…”