Effects of duplicate administration of human neural stem cell after focal cerebral ischemia in the rat.

We investigated the functional and histological recovery of middle cerebral artery occluded (MCAo) rats after of duplicate intravenous (i.v.) injection of human neural stem cells (hNSCs). Rats received i.v. injections of hNSCs (HB1.F3, 4 × 10(6) cells) on day 1 (1C), day 7 (7C), or both days 1 and 7 (1/7C) following MCAo. Functional recovery of rats was evaluated 1 day before MCAo and 1, 7, 14, 21, and 28 days following MCAo, using the modified neurological severity score (mNSS), and cylinder test. Nissl staining and anti-human nuclear matrix antigen /NeuN or GFAP were used to measure infarct size and investigate the migration and differentiation of injected cells. Treatment with hNSCs did not significantly affect infarct size of ischemic animals. Behavior evaluation using mNSS showed that functional deficits in the 1C group were reduced faster than in the 7C and 1/7C groups, and functional recovery in 1/7C rats was significantly more pronounced than that in the 7C group (day 21). Injected cells were identified at the boundary of lesions, where they had differentiated into neurons and astrocytes. Our study suggests that duplicate i.v. administration of hNSCs after stroke offers no advantages over single administration, 1 day following an ischemic event.