Genesis and maturation of vestibular hair cells.

The embryologic development in vivo and in vitro of mammalian hair cells in the crista ampullaris was continuously followed with regard to structural differentiation and maturation from the terminal mitosis to the morphological condition at partus or equivalent age in vitro. Otocysts were explanted both early and late during embryologic development: 13th and 16 gestation day, respectively. Both in fetal life and during in vitro conditions, the surface structures of the developing hair cell with regular arrangement of kinocilium/stereocilia were first differentiated, followed by a cytologic transformation intracellularly and subsequent development of nerve endings. Hair cells were able to develop without any morphologic contact with the nervous system. The afferent nerve system developed before the efferent nerve system (CBA/CBA mouse).