ULTRASTRUCTURE AND MOVEMENT OF THE EPENDYMAL AND TRACHEAL CILIA IN CONGENITALLY HYDROCEPHALIC WIC-HYD RATS

The aim of the present investigation is to determine whether or not hydrocephalus occurring in hydrocephalic Wistar-Imamichi strain rats (WIC-Hyd) is caused by functional and structural disorders of ependymal cilia. Ultrastructures and movement of cilia in the ependyma of the lateral, III and IV ventricles and aqueduct of Sylvius and in the trachea walls of the animals were examined by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and light microscopy using a phase-contrast microscope equipped with a high-speed video recording system. SEM revealed that a marked decrease in the length and number of cilia in the ependymal and tracheal walls occurred in affected male WIC-Hyd. This finding was noted even before the development of ventricular dilatation and was not related to the degree of ventricular enlargement after development of hydrocephalus. A moderate decrease in length and number of cilia was also seen among the normal ciliary tufts in affected female rats which developed a mild degree of hydrocephalus. TEM cilia findings included abnormal axonemal structures such as a lack of dynein arms and displacement of microtubules. The incidence of these ultrastructural abnormalities was found to be greater in affected male rats than in affected female rats. All cilia in affected male rats before and after development of hydrocephalus were immotile. A variety of movement disorders such as immobile, rotatory, and vibratory cilia were observed beside normally beating cilia (motile cilia) in affected female rats which never developed hydrocephalus as severe as that seen in affected male rats. These results seem to indicate that there is a correlation between cilia movement disorder and the degree of ultrastructural abnormalities. Consequently, hydrocephalus developing in affected male and female WIC-Hyd appears to be caused by a motility disorder of ependymal cilia which is part of the primary ciliary dyskinesia (PCD) affecting these animals. The present study appears to indicate that the movement of ependymal cilia may play a role in cerebrospinal fluid circulation, and that dysfunction of ependymal ciliary movement may contribute to development of hydrocephalus in WIC-Hyd rats.