Study Design in Experiments 1 and 2.

Experiment 1 was conducted to identify the time point of human mesenchymal stem cell (MSC) transplantation that led to maximal neurological recovery in rats after middle cerebral artery occlusion (MCAO). In Experiment 2, MSCs were administered at 1 h after MCAO, the time point identified in Experiment 1 as being optimal for enabling maximal neurological recovery. Infarction volume, neurological recovery, MMP-2 and MMP-9 activity, and vascular density after MCAO were compared between the MSC 1-hour group and the control group.