Novel observations on the origin of ependymal cells in the ventricular zone of the rat spinal cord.

Despite extensive investigations of gliogenesis, the time of origin of ependymal cells in the spinal cord has not yet been fully elucidated. Using a single dose of 5-bromo-2-deoxyuridine combined with various survival times we monitored: mitotic activity (short survival time), the presence of newly formed cells in the ventricular zone (intermediate survival time) and the formation of ependymal cells (long survival time) during the late embryonic and early postnatal development in the ventricular zone of the spinal cord of rats. In the period of study it was found that the ependymal cells populated this region in two waves. Most of the ependymal cells originated around embryonic day 18 and then between postnatal days 8 and 15. In addition, it was observed that in the ventricular zone of the spinal cord, proliferation and production of ependymal cells continues at the slower rate at least until day 36 of postnatal development. Elucidation of the relationship between progenitors in the embryonic ventricular zone and the relative quiescent ependymal lining of the central canal in adulthood could be important in the search for the adult neural stem cell niche.