Divergent aging characteristics in CBA/J and CBA/CaJ mouse cochleae.
Two inbred mouse strains, CBA/J and CBA/CaJ, have been used nearly interchangeably as 'good hearing' standards for research in hearing and deafness. We recently reported, however, that these two strains diverge after 1 year of age, such that CBA/CaJ mice show more rapid elevation of compound action potential (CAP) thresholds at high frequencies (Ohlemiller, Brain Res. 1277: 70-83, 2009). One contributor is progressive decline in endocochlear potential (EP) that appears only in CBA/CaJ. Here, we explore the cellular bases of threshold and EP disparities in old CBA/J and CBA/CaJ mice. Among the major findings, both strains exhibit a characteristic age (∼18 months in CBA/J and 24 months in CBA/CaJ) when females overtake males in sensitivity decline. Strain differences in progression of hearing loss are not due to greater hair cell loss in CBA/CaJ, but instead appear to reflect greater neuronal loss, plus more pronounced changes in the lateral wall, leading to EP decline. While both male and female CBA/CaJ show these pathologies, they are more pronounced in females. A novel feature that differed sharply by strain was moderate loss of outer sulcus cells (or 'root' cells) in spiral ligament of the upper basal turn in old CBA/CaJ mice, giving rise to deep indentations and void spaces in the ligament. We conclude that CBA/CaJ mice differ both quantitatively and qualitatively from CBA/J in age-related cochlear pathology, and model different types of presbycusis.
Ohlemiller
Kevin K
KK
Program in Audiology and Communication Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA. kohlemiller@wustl.edu
Dahl
Ashley R
AR
Gagnon
Patricia M
PM
D000200:Action Potentials / Q000502:physiology; D000375:Aging / Q000473:pathology* / Q000502:physiology*; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D003051:Cochlea / Q000473:pathology* / Q000502:physiology*; D004195:Disease Models, Animal; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D011304:Presbycusis / Q000473:pathology / Q000503:physiopathology; D012727:Sex Characteristics