Summary Human pluripotent stem cells offer promise for use in cell-based therapies for brain injury and diseases. However, their cellular behavior is poorly understood. Here we show that the expression of the brain-specific microRNA-9 (miR-9) is turned on in human neural progenitor cells (hNPCs) derived from human embryonic stem cells. Loss of miR-9 suppressed proliferation but promoted migration of hNPCs cultured in vitro. hNPCs without miR-9 activity also showed enhanced migration when transplanted into mouse embryonic brains or adult brains of a mouse model of stroke. These effects were not due to precocious differentiation of hNPCs. One of the key targets directly regulated by miR-9 encodes stathmin, which increases microtubule instability and whose expression in hNPCs correlates inversely with that of miR-9. Partial inhibition of stathmin activity suppressed the effects of miR-9 loss on proliferation and migration of human or embryonic rat neural progenitors. These results identify miR-9 as a novel regulator that coordinates the proliferation and migration of hNPCs.

Background and Purpose We have demonstrated in a previous study that superoxide radicals play a role in the pathogenesis of cerebral infarction, using a transgenic mouse model of distal middle cerebral artery occlusion, permanent ipsilateral cerebral carotid artery occlusion, and 1-hour contralateral cerebral carotid artery occlusion that produced infarction only in the cortex. However, the role of superoxide radicals in reperfusion injury in transgenic mice overexpressing superoxide dismutase (SOD) is unknown. Using a mouse model of intraluminal blockade of middle cerebral artery that produced both cortical and striatal infarction, we now further examined the role of superoxide radicals in ischemic cerebral infarction after reperfusion in transgenic mice overexpressing human CuZn-SOD activity.Methods Transgenic mice of strain Tg HS/SF-218, carrying human SOD-1 genes, and nontransgenic littermates were anesthetized with chloral hydrate (350 mg/kg IP) and xylazine (4 mg/kg IP). Physiological parameters were maintained at a normal range using a 30% O 2 /70% N 2 O gas mixture inserted via an inhalation mask. Body temperature was maintained at 37±0.5°C by using a heating pad throughout the studies. The middle cerebral artery occlusion was achieved with a 5-0 rounded nylon suture placed within the internal cerebral artery for 3 hours followed by the removal of the suture to allow reperfusion for another 3 hours. Cerebral infarct size in brain slices and infarct volume, neurological deficit, cortical blood flow, and glutathione levels were measured in both transgenic and nontransgenic mice.

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.