Age-related changes of myelin basic protein in mouse and human auditory nerve

• Published in: PloS one 2012-04, Vol.7 (4), p.e34500-e34500
• Main Authors: Xing, Yazhi, Samuvel, Devadoss J, Stevens, Shawn M, Dubno, Judy R, Schulte, Bradley A, Lang, Hainan
• Format: Article
• Language: English
• Subjects: Adult; Adults; Age; Aged; Aged, 80 and over; Aging; Aging - physiology; Alternations; Alzheimer's disease; Analysis; Animals; Auditory nerve; Auditory system; Biology; Bones; Brain-derived neurotrophic factor; Cochlear Nerve - cytology; Cochlear Nerve - metabolism; Cochlear Nerve - ultrastructure; Confocal microscopy; Degeneration; Ear; Electron microscopy; Female; Fibers; Ganglia; Hair; Hearing - physiology; Hearing loss; Hearing protection; Humans; Immunoenzyme Techniques; Immunoreactivity; Inner ear; Laboratories; Male; Medicine; Metabolism; Mice; Mice, Inbred CBA; Microscopy, Electron, Transmission; Middle Aged; Myelin; Myelin basic protein; Myelin Basic Protein - metabolism; Myelin proteins; Nervous system; Neurons; Otolaryngology; Pathology; Physiological aspects; Polymerization; Proteins; Rodents; Sheaths; Spectrum analysis; Spiral ganglion; Studies; Surgery; Target marketing; Temporal bone
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0034500

Age-related hearing loss (presbyacusis) is the most common type of hearing impairment. One of the most consistent pathological changes seen in presbyacusis is the loss of spiral ganglion neurons (SGNs). Defining the cellular and molecular basis of SGN degeneration in the human inner ear is critical to gaining a better understanding of the pathophysiology of presbyacusis. However, information on age-related cellular and molecular alterations in the human spiral ganglion remains scant, owing to the very limited availably of human specimens suitable for high resolution morphological and molecular analysis. This study aimed at defining age-related alterations in the auditory nerve in human temporal bones and determining if immunostaining for myelin basic protein (MBP) can be used as an alternative approach to electron microscopy for evaluating myelin degeneration. For comparative purposes, we evaluated ultrastructural alternations and changes in MBP immunostaining in aging CBA/CaJ mice. We then examined 13 temporal bones from 10 human donors, including 4 adults aged 38-46 years (middle-aged group) and 6 adults aged 63-91 years (older group). Similar to the mouse, intense immunostaining of MBP was present throughout the auditory nerve of the middle-aged human donors. Significant declines in MBP immunoreactivity and losses of MBP(+) auditory nerve fibers were observed in the spiral ganglia of both the older human and aged mouse ears. This study demonstrates that immunostaining for MBP in combination with confocal microscopy provides a sensitive, reliable, and efficient method for assessing alterations of myelin sheaths in the auditory nerve. The results also suggest that myelin degeneration may play a critical role in the SGN loss and the subsequent decline of the auditory nerve function in presbyacusis.