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 16 weeks 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.

► Stroke-induced neurogenesis originates from neurogenic spot in subventricular zone. ► Ependymal cells in neurogenic spot do not proliferate and their numbers decline at 6 and 16 weeks after stroke. ► Ependymal cell loss is accompanied by emergence of ectopic ependymal cells in adjacent striatum. ► Ectopic ependymal cells are found along blood vessels, in pericyst regions, and in glial scar but do not incorporate BrdU.