Ectopic ependymal cells in striatum accompany neurogenesis in a rat model of stroke

Stroke-induced neurogenesis originates from a neural stem cell (NSC) niche in subventricular zone (SVZ). In mice, NSCs are concentrated in a so-called "neurogenic spot" in the lateral angle area of SVZ. We aimed to identify the "neurogenic spot" in the rat SVZ and to characterize the cellular changes in the ependymal cell compartment in this area at different time points after middle cerebral artery occlusion. The majority of ependymal cells outlining the ventricular wall did not proliferate, and their numbers in the "neurogenic spot" declined at 6 and 16weeks after stroke. Cells with the ultrastructural properties of ependymal cells were detected in the adjacent striatum. The number of these ectopic ependymal cells (EE cells) correlated positively with the magnitude of lateral ventricular enlargement and negatively with the ependymal cell number in the "neurogenic spot". EE cells were found along blood vessels, accumulated in the pericyst regions, and participated in scar formation but did not incorporate BrdU. We provide the first evidence for the occurrence of EE cells in the ischemic striatum following stroke.