Abstract

Two neurogenic regions have been described in the adult brain, the subventricular zone and the dentate gyrus subgranular zone. Stem cells in these regions have been extensively studied. However, proliferating cells are found in other periventricular regions along the neuraxis, including the spinal cord central canal, where the identity of the stem cells is not known. In order to clarify which cell types proliferate in the central canal, we performed a meticulous study of this region in the rodent and in the macaque. The common cell type in the rodent spinal cord central canal was an ependymal biciliated cell that lacked centrioles and displayed motile cilia with a basal body that differed from the basal bodies of multiciliated ependymal cells. In contact with the lumen we also observed ependymal cells with one or three cilia, astrocytes with a single cilium, and neurons. The vast majority of actively dividing cells corresponded to ependymal biciliated cells, which generated new ependymal cells that contributed to the central canal length extension. The macaque central canal also contained ependymal cells, astrocytes with a single cilium, and neurons. In contrast to the rodent, ependymal cells in the macaque spinal cord were multiciliated, biciliated and uniciliated. As in the rodent, macaque central canal ependymal cells proliferated and gave rise to new ependymal cells.