Late-phase recovery in the cochlear lateral wall following severe degeneration by acute energy failure.

Publisher: Elsevier/North-Holland Biomedical Press Country of Publication: Netherlands NLM ID: 0045503 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1872-6240 (Electronic) Linking ISSN: 00068993 NLM ISO Abbreviation: Brain Res Subsets: MEDLINE

Original Publication: Amsterdam Elsevier/North-Holland Biomedical Press.

Cochlear Diseases/*physiopathology ; Fibroblasts/*metabolism ; Hearing Loss, Sensorineural/*physiopathology ; Mitochondrial Diseases/*metabolism ; Recovery of Function/*physiology ; Spiral Ligament of Cochlea/*metabolism; Animals ; Cochlear Diseases/chemically induced ; Cochlear Diseases/pathology ; Disease Models, Animal ; Fibroblasts/drug effects ; Fibroblasts/pathology ; Hearing Loss, Sensorineural/chemically induced ; Hearing Loss, Sensorineural/pathology ; Male ; Mitochondrial Diseases/chemically induced ; Mitochondrial Diseases/physiopathology ; Rats ; Rats, Sprague-Dawley ; Severity of Illness Index ; Spiral Ligament of Cochlea/pathology ; Spiral Ligament of Cochlea/physiopathology

We previously reported a model of acute cochlear energy failure using a mitochondrial toxin, 3-nitropropionic acid (3-NP), to study mechanisms of inner ear disorders such as inner ear ischemia. In this model, the main cause of hearing loss is apoptosis of fibrocytes in the cochlear lateral wall. Here, we analyzed the time course of structural and hearing level changes in the cochlea from the acute phase to the chronic phase up to 2 months after surgery. Hearing levels as determined by auditory brainstem response (ABR) thresholds exceeded the maximum acoustic output (>87 dBSPL) of the system at all frequencies 1 day after 3-NP treatment. Histology showed nearly complete loss of fibrocytes 2 weeks after 3-NP treatment. However, after 2 months, ABR showed significant recovery at low frequency (8 kHz) in four of five rats treated with 3-NP. ABR thresholds at 20 kHz occasionally showed some recovery. At 40 kHz, recovery of ABR thresholds was not observed. Histology of 3-NP-treated rats revealed partial recovery of the lateral wall and the regenerated fibrocytes in the spiral ligament expressed Na/K-ATPase in the cochlear basal turn 2 months after 3-NP treatment. These results indicate that ABR recovery is caused by regeneration of the cochlear lateral wall. Our findings demonstrate the recoverable capacity of the cochlear lateral wall that leads to functional recovery after severe damage.
(Copyright © 2011 Elsevier B.V. All rights reserved.)

Date Created: 20110920 Date Completed: 20120803 Latest Revision: 20111017

20221213

10.1016/j.brainres.2011.08.062

21925650