Emerging lines of evidence show that glial cells are not simply supportive, but rather are functional, controling various brain functions. Thus, their dysfunction seems to be closely related to several brain diseases. Although glial cells are non-excitable cells and do not evoke action potentials, they have various receptors for chemical transmitters, respond to them, and release chemical transmitters, so called "gliotransmitters". Using these gliotransmitters, glial cells communicate with adjacent cells including neurons, vascular cells and glial cells themselves. Glial cells, especially astrocytes, enwrap almost all synapses and release gliotransmitter in response to neuronal activities or even spontaneously. As a gliotransmitter, extracellular ATP has a central role. Astrocytic ATP acts on the P2 receptors on astrocytes to produce a spreading Ca^<2+> wave, which induces further ATP release from astrocytes to control neuronal activities. Almost 10 years have passed since the first report of such dynamic glial activities in vitro, and we now understand that astrocytes are active even in vivo. Here, we show that astrocytic ATP dynamically regulates neuronal excitability, i.e., synaptic transmission.

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Effective stroke therapies require recanalization of occluded cerebral blood vessels. However, reperfusion can cause neurovascular injury, leading to cerebral edema, brain hemorrhage, and neuronal death by apoptosis/necrosis. These complications of reperfusion, which result from excess production of reactive oxygen species (ROS), significantly limit the benefits of stroke therapies. We recently found two novel targets for neurovascular protection after ischemia/reperfusion: the signal transducer and activator of transcription 3 (STAT3) pathway and NADPH oxidase (NOX). Manganese-superoxide dismutase (SOD2) plays a critical role in neurovascular injury as a first-line defense against ROS produced in mitochondria, and STAT3 is a major transcriptional factor of the SOD2 gene. During reperfusion, activation of STAT3 and its recruitment into the SOD2 gene are blocked, resulting in increased oxidative stress and neuronal apoptosis. Pharmacological activation of STAT3 with interleukin-6 induces SOD2 expression, which limits ischemic neuronal death. In contrast, NOX is a pro-oxidant multi-subunit enzyme. After ischemia/reperfusion, NOX in the neurovascular unit forms an activated complex to generate ROS, which induce oxidative injury in the neurovascular unit. Pharmacological and genetic inhibition of NOX is neuroprotective against cerebral ischemia/reperfusion. Superoxide dismutase and NOX regulate ROS production in the ischemic brain, interacting with each other in a Yin and Yang relationship. Our neurovascular protective strategies targeting these two enzymes may expand the therapeutic window of the currently approved therapies.

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Ischemic tolerance showed robust protection in the experimental stroke model, but the molecular mechanisms underlying this phenomenon remain unclear. Gene expression of such factors as heat shock protein and anti-apoptotic protein had been extensively investigated, and furthermore, we recently found that CREB activation plays acrucial role on attenuation of ischemic damage and the acquisition of ischemic tolerance. However, metabolic down-regulation and gene reprogramming has recently attracted much attention because of the common pathways also seen in hypothermia, hibernation and endotoxin tolerance. In addition, endogenous adaptation in cerebral collateral vessels against hypoperfusion and ischemia has now been shown to be arteriogenesis. An increase in shear stress in the pial arteriole induces enlargement of vessel diameters and growth of collateral circulation. Colony stimulating factors have also been shown to accelerate the growth of pial collateral vessels. Arteriogenesis enhancement could be a potential target for mitigating ischemic severity after major cerebral artery occlusion.

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The intravenous administration of mesenchymal stem cells (MSCs) derived from bone marrow has been reported to ameliorate functional deficits in several CNS diseases in experimental animal models. Although MSCs may be present in different proportions in the stromal cell fraction of various species, human MSCs have a distinct cell surface antigen pattern including SH2^+, SH3^+, and CD34^-. Although human MSCs have been clinically used for treating several diseases, it is still uncertain whether MSCs may have therapeutic benefits for stroke patients. The objectives of this study were to examine the feasibility and safety of cell therapy using auto serum expanded autologous MSCs in stroke patients. Twelve (male and female) patients with stroke were enrolled. Bone marrow from the stroke patients were obtained by aspiration from the posterior iliac crest after informed consent was obtained. MSCs were cultured in appropriate medium in a humidified atmosphere of 5% CO_2 at 37℃, harvested, and cryopreserved until use. On the day of infusion cryopreserved units were thawed and injected intravenously into patients over 30min. All patients were monitored closely during and within 48h of MSC injections. Oxygen saturation, temperature, blood pressure, pulse and respiratory rate were carefully monitored before and after injection. Patients also had chest films before and after MSC injection. Patients had carefully been followed for 12 months. Human bone marrow-derived MSCs were successfully isolated from bone marrow aspirate from all 12 stroke patients, and all were successfully culture-expanded. Serial evaluations showed no severe adverse cell-related effects. In patients with cerebral infarcts, the intravenous administration of autologous MSCs appears to be feasible and safe, and merits further study as a therapy that may improve functional recovery.

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Partial restoration of function after spinal cord contusion has been accomplished by injecting stem cells. However, the effect is shown only for the acute and/or subacute phase. Carlos Lima, et al. who are pioneers in this field reported their clinical pilot study of olfactory mucosa transplantation for chronic spinal cord injury. They showed the safety and feasibility of it. The failure of the spinal cord to regenerate and undergo reconstruction after spinal cord injury (SCI) can be attributed to the extremely limited regenerative capacity of most central nervous system (CNS) axons, as well as the hostile environment of the adult CNS. After SCI, astroglial scarring forms within lesioned areas. It has been shown that axon regeneration is initiated in the injured spinal cord but is blocked by glial scar formation. Therefore, a suitable local environmental is likely to be required for successful axonal regeneration. Olfactory mucosa contains stem cells that can replace lost cells, and olfactory ensheathing cells that stimulate axon growth and provide scaffold for axon growth.

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Induced Pluripotent Stem (iPS) cells are regarded to be potential supply source of cells for application to cell replacement therapies. Recent scientific papers indicated that human iPS cells are capable of differentiating into glutamatergic neurons, dopaminergic neurons, and motor neurons. However, tumorigenesis in iPS cells is a serious problem which should be overcome for clinical application. Recently, we evaluated the influence of ischemic condition on undifferentiated iPS cells within a transient Middle Cerebral Artery Occlusion (MCAO) using a mouse model. Undifferentiated iPS cells (5×10^5) were injected into the ipsilateral striatum and cortex, which were considered as the ischemic boundary zone at 24 hours after MCAO. Ischemic brains treated with iPS cells tended to form teratoma with larger volume compared with those in intact brains. c-Myc, Oct3/4 and Sox2 were strongly expressed in iPS-derived tumors of the ischemic brain. Above results indicated that the transcriptional factors integrated into the genome by retrovirus vectors might promote teratoma formation in the ischemic brain. Potential interaction between integrated transcriptional factors and iPS cell characteristics needs to be kept in mind, for the development of transplantation therapy.

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Regenerative therapy against stroke is a novel concept. According to recent progress in stem cell biology, adult neurogenesis was rediscovered and neural stem cells were able to be cultured in vitro. There are still many problems to be clarified in order to regulate regenerative therapy using neural stem cells. We can now start to use neural stem cells to overcome neurological diseases.

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Background: Carotid Blowout Syndrome (CBS), or Carotid Artery Rupture (CAR), is a delayed complication with potentially fatal consequences occurring after the implementation of radiotherapy on head and neck tumors. In this report we describe two patients received endovascular treatment for severe hemorrhagic CBS developing 36 and 2 years, respectively, after radiotherapy. Both patients survived and responded positively to treatment. Methods: Case 1 was an 80-year-old woman found with minor hemorrhage near the bifurcation of the common carotid artery, 36 years after neck irradiation. She experienced frequent hemorrhagic events during the following years. Six years after the initial discovery of bleeding, she experienced massive hemorrhage, lapsed into shock, and was admitted to an Emergency Room. Connective tissue around the carotid artery was largely exposed due to neck skin defect. After hemorrhage was halted by manual compression, transient hemostasis was achieved with coil embolization of the aneurysm presumed to be the source of bleeding. Recurrent hemorrhage developed two weeks later with unraveled coil mass extrusion. Parent artery occlusion was performed by endovascular trapping, achieving permanent hemostasis. Case 2 presented massive nasal bleeding originating from the petrous segment of the internal carotid artery, 2 years after having been treated with heavy particle irradiation for olfactory neuroblastoma. Ischemic tolerance was confirmed by balloon occlusion test. Based on previous experiences, the bleeding was immediately halted by endovascular trapping. Result: Both patients were subsequently discharged, free of new neurological symptoms. Conclusion: Emergent hemostatic treatment is required in CBS developing severe hemorrhage. However, within irradiation fields, temporal embolization devices hardly lead to complete resolution. This is due to the deteriorated condition of the vascular wall incapable to enduring the expansion power of coils, stents or balloons. Bypass grafting is also difficult, due to the fragile surrounding tissue. Although, the application of sufficiently-long covered stents is anticipated in the future, parent artery embolization is often required to save the patient's life even when the occlusion test is impossible. In such cases, endovascular trapping out of irradiation fields is the most reliable and efficacious treatment for achieving permanent hemostasis.

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Carotid endarterectomy (CEA) is a well established procedure for the prevention of cerebral infarction secondary to carotid artery stenosis, but the use of intraluminal shunt during CEA remains controversial. We have used intraluminal shunt selectively if the collateral blood supply is insufficient during cross clamping. The ischemic tolerance is investigated by carotid artery balloon test occlusion before insertion of the intraluminal shunt during CEA for patients with contralateral carotid severe stenosis or occlusion. If ischemic symptoms, such as paralysis, develop within 5 minutes after the test occlusion, we think that insertion of the intraluminal shunt carries the risk of ischemic complication. Therefore, we use femoral-internal carotid extraluminal shunt instead of intraluminal shunt, which allows us to perform CEA without interrupting the blood flow to the brain. In addition, the extraluminal shunt can supply blood to the brain without relying on blood pressure, because the blood flow is supplied by a roller pump. We have also applied this technique to patients with long segment common carotid stenosis who require more time to insert the intraluminal shunt than usual, and patients with carotid pseudoaneurysm who require carotid cross clamping during CEA. The femoral-internal carotid extraluminal shunt could be placed in all cases without problems, and CEAs were performed without complications. Femoral-internal carotid extraluminal shunt can reduce perioperative complications in patients who have potential risks associated with insertion of an intraluminal shunt.

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