Distribution and time course of hair cell regeneration in the pigeon utricle

Vestibular and cochlear regeneration following ototoxic insult from aminogl ycoside antibiotics has been well documented, particularly in birds. In the present study, intraotic application of a 2 mg streptomycin paste was used to achieve complete vestibular hair cell destruction in pigeons (Columba l ivia) while preserving regenerative ability. Scanning electron microscopy w as used to quantify hair cell density longitudinally during regeneration in three different utricular macula locations, including the striola, central and peripheral regions. The utricular epithelium was void of stereocilia ( indicating hair cell loss) at 4 days after intraotic treatment with strepto mycin. At 2 weeks the stereocilia began to appear randomly and mostly in an immature form. However, when present most kinocilia were polarized toward the developing striola. Initially, regeneration occurred more rapidly in th e central and peripheral regions of the utricle as compared to the striola. As regeneration proceeded from 2 to 12 weeks, hair cell density in the str iola region equaled the density noted in the central and peripheral regions . At 24 weeks, hair cell density of the central and peripheral regions was equal to normal values, however the striola region had a slightly greater h air cell density than that observed for normal animals. (C) 1999 Elsevier S cience B.V. All rights reserved.