Expression of S-100 protein in the human fetal inner ear.

The expression of S-100 protein was analyzed in the human fetal inner ear using immunohistochemical methods. In the 11-week-old human fetus, the cochlea was almost negative for S-100 protein, whereas in the 14- and 15-week-old fetuses, the spiral ligament, Reissner's membrane and spiral limbus were positive for the protein. These results suggest that S-100 protein may be a reliable marker for determining functional maturation of the fetal cochlea and the inner ear. In the 11-, 14- and 15-week fetuses, the epithelial cells of the endolymphatic sac were labelled with S-100 protein. These findings demonstrate that the endolymphatic sac, spiral limbus and spiral ligament in the fetal inner ear have a high activity of S-100 protein, with this presence possibly related to fluid and ion transport of endolymph.