Endothelial progenitor cells (EPCs) have been implicated in playing an important role in vascular repair and revascularization in ischemic organs including brain tissue. However, the cause of EPC migration and the function of EPC playing following post-ischemia are unclear. Here, we reported EPC therapy in a mouse model of transient middle cerebral artery occlusion (tMCAO) to explore the roles of EPC following ischemic brain injury.Human EPCs were cultured, characterized, and confirmed with flow cytometry. Ex vivo expanded EPCs (1×10 6 ) were injected via jugular vein after 1 hour of tMCAO. Histological and behavioral analyses were performed from day 1 to 28 days after tMCAO.EPCs were detected in ischemic brain region 24 hours after MCAO. EPC transplantation significantly reduced ischemic infarct volume at 3 days following MCAO compared to the control (p<0.05). CXCR4 was expressed on majority of EPCs and SDF-1-induced EPC migration was blocked by AMD3100 in vitro. SDF-1 was up-regulated in ischemic brain and AMD3100 could reduce EPCs migration to the ischemic region in vivo, suggesting that SDF-1/CXCR4 was involved in EPC-mediated neuroprotection. Compared to the control, EPC therapy reduced mouse cortex atrophy 4 weeks after tMCAO, which was accompanied by improved neurobehavioral outcomes (p<0.05). In addition, EPC injection potently increased angiogenesis in the periinfarction area (p<0.05).We conclude that systemic delivery of EPC protect against cerebral ischemic injury, promote neurovascular repair, and improve long-term neurobehavioral outcomes. Our data suggests that SDF-1/CXCR4 plays a critical role in EPC-mediated neuroprotection.

Background and Purpose-Insulin-like growth factor I (IGF-1) is a pleiotropic growth factor that has been demonstrated to protect against acute ischemic brain injury. Whether IGF-1 improves long-term functional outcome after ischemic stroke is not known. The aim of this study is to examine whether IGF-1 overexpression through adeno-associated virus (AAV) -mediated gene transfer enhances neurovascular remodeling and improves functional outcome in a mouse model of focal cerebral ischemia. Methods-Long-term cerebral IGF-1 overexpression was achieved with the AAV transduction system through stereotaxic injection. Control mice were injected with AAV-green fluorescent protein or saline. Three weeks after gene transfer, the mice underwent permanent distal middle cerebral artery occlusion. Histological and behavioral analyses were performed at day 21 after middle cerebral artery occlusion. Results-IGF-1 gene transfer compared with control treatment significantly improved motor performance assessed by sensorimotor tests. The functional recovery was accompanied by reduced volume of cerebral infarction. Immunohistochemical analysis with endothelial cell marker CD31 revealed that IGF-1 gene transfer potently increased neovessel formation in the periinfarct and injection needle tract area compared with AAV-green fluorescent protein transduction. Increased vascular density was associated with increased local vascular perfusion. Additionally, AAV-IGF-1 treatment enhanced neurogenesis in the subventricular zone compared with AAV-green fluorescent protein treatment. Conclusions-These data demonstrate that IGF-1 overexpression promoted long-lasting functional recovery after cerebral infarction. The improved functional performance was paralleled by enhanced neovascularization and neurogenesis.