epidermal-growth-factor and Hearing-Loss--Noise-Induced

We performed an in vitro study in order to determine possible triggers of hair cell regeneration in the chick basilar papilla following degeneration. We compared the response of sensory epithelium damaged by collagenase treatment with that damaged by acoustic trauma. The former exhibited no proliferative activity, but the latter did. The basilar papillae damaged by acoustic trauma could have proliferating activity in medium containing fetal bovine serum (FBS) or epidermal growth factor (EGF) but not in the medium without FBS or EGF. These findings indicate that regeneration of basilar papillae depends on the manner of cell death and that FBS or EGF is required for regeneration.

Topics: Animals; Anti-Ulcer Agents; Antibodies, Monoclonal; Cattle; Cell Death; Cell Movement; Chickens; Collagenases; Epidermal Growth Factor; Hair Cells, Auditory; Hearing Loss, Noise-Induced; Regeneration

The expression of epidermal growth factor receptor (EGFR) in cochlear hear cells was studied in normal and guinea pigs exposed to blasts. The effects of epidermal growth factor (EGF) and dexamethasone (DXM) treatment for blast hearing loss and the underlying mechanisms were also explored. Scattered expression of EGFR was seen in IHCs and OHCs in normal guinea pigs. Segmentally distributing positive reaction was also located in stereocillia of hair cells. Distribution of EGFR reaction was seen in the cytoplasm of IHC 24 hours after exposure to blasts, and in the stereocillia of IHC and the cuticular plate of OHC 72 hours postexposure. At one week EGFR reaction in hair cells increased obviously and part of OHC stereocillia also showed positive reaction. EGFR reaction reduced at two weeks, though positive reaction could still be found in the stereocillia of hair cells at one month. Combination of EGF and DXM administrations promoted hearing recovery significantly. Our results suggest that healing of injured hair cells may be to EGF.

Topics: Animals; Anti-Inflammatory Agents; Blast Injuries; Dexamethasone; Epidermal Growth Factor; ErbB Receptors; Evoked Potentials, Auditory, Brain Stem; Female; Guinea Pigs; Hair Cells, Auditory; Hearing Loss, Noise-Induced; Male