Vol.96 No.5 contentsPRACTICA OTO-RHINO-LARYNGOLOGICA
Vol. 96 No.5 May 2003
Induction of Inner Ear Hair Cell Regeneration
Norio Yamamoto and Juichi Ito
(Kyoto University)
Since the discovery of the spontaneous regeneration of inner ear hair cells in birds and mammals from the late 1980's to the early 1990's, its mechanisms have been studied. Three mechanisms of regeneration of the inner ear hair cells have been reported so far: regeneration by mitosis of supporting cells, transdifferentiation of supporting cells into hair cells, and self-repair of the sublethal hair cells. However, which mechanism contributes most to the regeneration of the inner ear hair cells has remained to be elucidated.
Extrinsic and diffusible factors like various growth factors have been reported to proliferate hair cell numbers in the inner ear. Regeneration of organs could be achieved not only by induction of proliferation with extrinsic factors but also by repeating their developmental pathways in adult organs. Molecular biology and gene targeting reveal that various intrinsic factors and signaling pathways such as cell cycle regulators, WNT signaling, and Notch signaling have important roles in the development of inner ears, and that progenitors of sensory epithelium would exist at the greater epithelial ridge in the inner ear. Further analysis and application of these factors will contribute to regeneration of the inner ear hair cells.
Key words : regeneration, inner ear hair cells, cell cycle, WNT signaling, Notch signaling