Hair cell loss and regeneration after severe acoustic overstimulation in the adult pigeon.
The extent of hair cell regeneration following acoustic overstimulation severe enough to destroy tall hair cells, was determined in adult pigeons. BrdU (5-bromo-2'-deoxyuridine) was used as a proliferation marker. Recovery of hearing thresholds in each individual animal was measured over a period of up to 16 weeks after trauma. In ears with loss of both short and tall hair cells, little or no functional recovery occurred. In ears with less damage, where significant functional recovery did occur, there were always a few rows of surviving hair cells left at the neural edge of the basilar papilla. In the region of hair cell loss, numerous BrdU labeled cells were found. However, only a small minority of these cells were regenerated hair cells, the majority being monolayer cells. Irrespective of the extent of the region of hair cell loss, regenerated hair cells were observed predominantly in a narrow strip at the transition from the abneural area of total hair cell loss and the neural area of hair cell survival. With increasing damage this strip moved progressively towards the neural edge of the papilla. No regeneration of hair cells was observed in the abneural region of total hair cell loss, even up to 16 weeks after trauma. The results indicate that there is a gradient in the destructive effect of loud sound across the width of the basilar papilla, from most detrimental at the abneural edge to least detrimental at the neural edge. Both tall and short hair cells can regenerate after sound trauma. Whether they do regenerate or not depends on the degree of damage to the area of the papilla where they normally reside. Regeneration of new hair cells occurs only in a narrow longitudinal band, which moves from abneural into the neural direction with increasing damage. In the area neural to this band, hair cells survive the overstimulation. In the area abneural to this band, sound damage is so severe, that no regeneration of hair cells occurs. As a consequence morphological and functional deficits persist.
Ding-Pfennigdorff
D
D
Physiologisches Institut III, Klinikum der J.W. Goethe Universität, Frankfurt am Main, Germany.
Smolders
J W
JW
Müller
M
M
Klinke
R
R
D000161:Acoustic Stimulation; D000818:Animals; D001489:Basilar Membrane / Q000503:physiopathology; D001973:Bromodeoxyuridine; D002455:Cell Division; D002470:Cell Survival; D010856:Columbidae; D004261:DNA Replication / Q000502:physiology; D006198:Hair Cells, Auditory / Q000503:physiopathology*; D006317:Hearing Loss, Noise-Induced / Q000503:physiopathology*; D009416:Nerve Regeneration / Q000502:physiology*; D000159:Vestibulocochlear Nerve / Q000503:physiopathology*
D001973:Bromodeoxyuridine