title: Cellular correlates of progressive hearing loss in 129S6/SvEv mice.
abstract: Several strains of mice hear well initially but show progressive sensorineural hearing loss. Affected cochlear cell types include all those known to be affected in human age-related hearing loss (ARHL), or presbycusis. Thus these mice have been offered as models of human ARHL. At present, however, few mouse ARHL models are sufficiently well described to serve as the basis for specific hypotheses about human ARHL. We examined 1-month-old and 15-month-old 129S6/SvEv (129S6) mice and compared them with BALB/cJ and CBA/J mice. Age-related elevation of compound action potential thresholds was interpreted in the light of endocochlear potentials and changes in hair cells, afferent neurons, fibrocytes in spiral limbus and ligament, and supporting cells within the organ of Corti. Aging in 129S6 mice was associated with high-frequency hearing loss. Four components of age-related cochlear degeneration emerged from quantitative analyses, including 1) basal loss of outer hair cells; 2) basal loss of type IV fibrocytes in the spiral ligament; 3) apical loss of fibrocytes in spiral limbus, and 4) anomalies of supporting cells in the cochlear base. Although neuronal loss was not consistently found, two mice showed loss of afferent dendrites and cell bodies in the cochlear apex without inner hair cell loss. Despite multifaceted degeneration, hearing loss in 129S6 mice appears to be best explained by degenerative changes in outer hair cells and in the organ of Corti, conforming to human sensory ARHL. Age-related changes in the apical spiral limbus may promote pathology of the medial organ of Corti and eventual loss of afferent neurons, with possible implications for human neural ARHL.
authors.affiliation: Department of Otolaryngology, Washington University, Saint Louis, Missouri 63110, USA. kohlemiller@cid.wustl.edu
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Ohlemiller
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Gagnon
mesh_terms: D000161:Acoustic Stimulation; D000200:Action Potentials / Q000502:physiology / Q000528:radiation effects; D000375:Aging / Q000473:pathology*; D000818:Animals; D002452:Cell Count; D003051:Cochlea / Q000473:pathology* / Q000503:physiopathology; D004195:Disease Models, Animal; D004307:Dose-Response Relationship, Radiation; D004594:Electrophysiology; D006198:Hair Cells, Auditory / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D009410:Nerve Degeneration; D009457:Neuroglia / Q000473:pathology; D009474:Neurons / Q000473:pathology; D009925:Organ of Corti / Q000473:pathology; D011304:Presbycusis / Q000473:pathology* / Q000503:physiopathology; D013136:Spiral Ganglion / Q000473:pathology / Q000503:physiopathology