Proliferation of vertebrate inner ear supporting cells

Using two S phase markers, we determined the cell-cycle behavior of inner e ar supporting cells from two species, the chicken and the oscar. The result s indicate that chicken utricular supporting cells divide once and do not r eturn to the cell cycle for at least 7 days. In contrast, supporting cell p rogeny in the oscar saccule return to S phase after 5 days. While both the chicken utricle and oscar saccule show ongoing supporting cell proliferatio n, these data indicate that there may be a dedicated recycling population o f supporting cells in the oscar saccule but not in the chicken utricle that is responsible for hair cell production. An expulsion of proliferative cel l progeny in the chicken utricle after 7 days may be a driving force for pr oliferation, as well as an explanation for why hair cell numbers do not inc rease in the chicken utricle with age. This was not seen in the oscar saccu le, possibly explaining how this end organ increases in size throughout the adult life of the animal. The absence of S phase cell expulsion, however, does not rule out the role of cell death in the oscar saccule, (C) 1999 Joh n Wiley & Sons, Inc.