The astroglial reaction along the mouse cochlear nerve following inner ear damage.
OBJECTIVE
Determine how the astroglial cells of the peripheral and central nervous system transitional zone (PCTZ) react to sensorineural hearing loss using a mouse cochlear nerve model.


METHODS
Prospective, basic science.


METHODS
Research laboratory.


METHODS
Neomycin was injected into the mouse inner ear to cause chemically induced hearing loss. Auditory brainstem responses (ABRs) were used to determine hearing threshold shifts after neomycin treatment. Immunofluorescence was used to detect the expression of proteins specific for hair cells, spiral ganglion neurons, astrocytes, and the myelin components of both oligodendrocytes and Schwann cells.


RESULTS
ABR threshold shifts and immunofluorescence results supported that hair cells and spiral ganglion neurons were damaged in neomycin-treated mice. Immunofluorescence showed the peripheral and central nervous system (PNS and CNS) transitional zone of the cochlear nerve at the interface of the myelin components of the PNS and CNS. In the control mice, the expression of glial fibrillary acidic protein (GFAP) was observed proximally to the PCTZ closer to the CNS, which is their normal location. However, in neomycin-treated animals the expression of GFAP was detected distally to the PCTZ and was found close to the spiral lamina level in the basal cochlear turn, suggesting that GFAP-expressing astrocytes migrated across the PCTZ and reached the PNS.


CONCLUSIONS
The GFAP positive astrocyte processes extended across the PCTZ along the mouse cochlear nerve following chemically induced sensorineural hearing loss.
Department of Otolaryngology-HNS, Wayne State University School of Medicine, Detroit, Michigan, USA.
Zhengqing
Z
Hu
Baofu
B
Zhang
Xuemei
X
Luo
Lei
L
Zhang
Jue
J
Wang
Dennis
D
Bojrab
Hui
H
Jiang
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000473:pathology*; D003056:Cochlear Nerve / Q000187:drug effects / Q000473:pathology*; D007758:Ear, Inner / Q000187:drug effects / Q000473:pathology; D016057:Evoked Potentials, Auditory, Brain Stem; D005455:Fluorescent Antibody Technique; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D006198:Hair Cells, Auditory / Q000187:drug effects; D006319:Hearing Loss, Sensorineural / Q000139:chemically induced / Q000473:pathology*; D051379:Mice; D009355:Neomycin / Q000008:administration & dosage; D011446:Prospective Studies; D013136:Spiral Ganglion / Q000187:drug effects
D005904:Glial Fibrillary Acidic Protein; D009355:Neomycin
astrocyte; astroglial reaction; cochlear nerve; hearing loss; inner ear damage; transition zone