Stem cell-derived neurons grafted in the striatum are expelled out of the brain after chronic cortical stroke.

BACKGROUND AND PURPOSE In humans and rodents, cortical stroke can lead to cortex atrophy in long-term survivors. In the rodent, fetal brain neural precursors or stem cell-derived neurons grafted in the stroke-lesioned brain integrate successfully and reduce infarct in the short term. We have examined the fate, in the long term, of mouse embryonic stem cell-derived neural precursors grafted after permanent middle cerebral artery occlusion in mice. METHODS Green fluorescent protein-labeled neural precursors were grafted in the striatum of control and lesioned mice and their fate examined 9 months later. RESULTS In control mice, the neuronal progeny of mouse embryonic stem cells innervated distant brain structures, in a way remarkably similar between animals, displayed a laterality preference and remained polysialated neural cell adhesion molecule-immunoreactive. In lesioned mice, grafted cells were expelled out of the brain. CONCLUSIONS Stroke-related brain atrophy and reshaping were not prevented by cell grafting and, eventually, led to the expulsion of the graft.