[Hair cell regeneration in a chicken's inner ear after damage due to exposure to industrial noise].

In mammals, the damage to the hair cells of the inner ear due to exposure to noise or other ototoxic agents is irreversible. In fish, reptiles and birds, however, the hair cells may regenerate, probably from the supporting cells. This regeneration process in the inner ear is being intensively examined in animals in the hope of curing the sensorineural hearing loss in human subjects in future. The aim of the study was to assess hair cell regeneration in the inner ear of chicks after exposure to industrial noise, depending on the level of exposure. The birds were exposed either to the noise at the level of 110 dB (A), 4 hours a day, for 5 consecutive days, or at the level of 125 dB (A), 8 hours a day, for 5 consecutive days. The results confirm that the regeneration starts immediately during the period of recovery from acoustic trauma, and the supporting cells are the main source for new, developing hair cells. Moreover, we found that the complete damage to hair cells is not necessary to the proliferation of supporting cells and that the intensity of proliferation of these cells depends on the level and time of exposure.