Human embryonic stem cell neural differentiation and enhanced cell survival promoted by hypoxic preconditioning

Transplantation of neural progenitors derived from human embryonic stem cells (hESCs) provides a potential therapy for ischemic stroke. However, poor graft survival within the host environment has hampered the benefits and applications of cell-based therapies. The present investigation tested a preconditioning strategy to enhance hESC tolerance, thereby improving graft survival and the therapeutic potential of hESC transplantation. UC06 hESCs underwent neural induction and terminal differentiation for up to 30 days, becoming neural lineage cells, exhibiting extensive neurites and axonal projections, generating synapses and action potentials. To induce a cytoprotective phenotype, hESC-derived neurospheres were cultured at 0.1% oxygen for 12 h, dissociated and plated for terminal differentiation under 21% oxygen. Immunocytochemistry and electrophysiology demonstrated the ‘hypoxic preconditioning' promoted neuronal differentiation. Western blotting revealed significantly upregulated oxygen-sensitive transcription factors hypoxia-inducible factor (HIF)-1α and HIF-2α, while producing a biphasic response within HIF targets, including erythropoietin, vascular endothelial growth factor and Bcl-2 family members, during hypoxia and subsequent reoxygenation. This cytoprotective phenotype resulted in a 50% increase in both total and neural precursor cell survival after either hydrogen peroxide insult or oxygen–glucose deprivation. Cellular protection was maintained for at least 5 days and corresponded to upregulation of neuroprotective proteins. These results suggest that hypoxic preconditioning could be used to improve the effectiveness of human neural precursor transplantation therapies

Long-Term Survival of Human Neural Stem Cells in the Ischemic Rat Brain upon Transient Immunosuppression

Understanding the physiology of human neural stem cells (hNSCs) in the context of cell therapy for neurodegenerative disorders is of paramount importance, yet large-scale studies are hampered by the slow-expansion rate of these cells. To overcome this issue, we previously established immortal, non-transformed, telencephalic-diencephalic hNSCs (IhNSCs) from the fetal brain. Here, we investigated the fate of these IhNSC's immediate progeny (i.e. neural progenitors; IhNSC-Ps) upon unilateral implantation into the corpus callosum or the hippocampal fissure of adult rat brain, 3 days after global ischemic injury. One month after grafting, approximately one fifth of the IhNSC-Ps had survived and migrated through the corpus callosum, into the cortex or throughout the dentate gyrus of the hippocampus. By the fourth month, they had reached the ipsilateral subventricular zone, CA1-3 hippocampal layers and the controlateral hemisphere. Notably, these results could be accomplished using transient immunosuppression, i.e administering cyclosporine for 15 days following the ischemic event. Furthermore, a concomitant reduction of reactive microglia (Iba1+ cells) and of glial, GFAP+ cells was also observed in the ipsilateral hemisphere as compared to the controlateral one. IhNSC-Ps were not tumorigenic and, upon in vivo engraftment, underwent differentiation into GFAP+ astrocytes, and β-tubulinIII+ or MAP2+ neurons, which displayed GABAergic and GLUTAmatergic markers. Electron microscopy analysis pointed to the formation of mature synaptic contacts between host and donor-derived neurons, showing the full maturation of the IhNSC-P-derived neurons and their likely functional integration into the host tissue. Thus, IhNSC-Ps possess long-term survival and engraftment capacity upon transplantation into the globally injured ischemic brain, into which they can integrate and mature into neurons, even under mild, transient immunosuppressive conditions. Most notably, transplanted IhNSC-P can significantly dampen the inflammatory response in the lesioned host brain. This work further supports hNSCs as a reliable and safe source of cells for transplantation therapy in neurodegenerative disorders

Cell therapy for ischemic stroke : are differences in preclinical and clinical study design responsible for the translational loss of efficacy?

Cell therapy is an attractive strategy for enhancing post‐stroke recovery. Different cell types and several treatment strategies have been successfully applied in animal models, but efficacy in stroke patients has not yet been confirmed. We hypothesize that the significant design differences between preclinical and clinical trials may account for this situation. Using a meta‐analysis approach and comparing preclinical with clinical trials, we reveal and discuss preliminary evidence for such design differences. While available datasets are not yet numerous enough to draw definitive conclusions, these findings may represent signposts on the route to efficacy by harmonizing preclinical and clinical study designs

Endovascular middle cerebral artery occlusion in rats as a model for studying vascular dementia

Vascular dementia (VaD), incorporating cognitive dysfunction with vascular disease, ranks as the second leading cause of dementia in the United States, yet no effective treatment is currently available. The challenge of defining the pathological substrates of VaD is complicated by the heterogeneous nature of cerebrovascular disease and coexistence of other pathologies, including Alzheimer’s disease (AD) types of lesion. The use of rodent models of ischemic stroke may help to elucidate the type of lesions that are responsible for cognitive impairment in humans. Endovascular middle cerebral artery (MCA) occlusion in rats is considered to be a convenient and reliable model of human cerebral ischemia. Both sensorimotor and cognitive dysfunction can be induced in the rat endovascular MCA occlusion model, yet sensorimotor deficits induced by endovascular MCA occlusion may improve with time, whereas data presented in this review suggest that in rats this model can result in a progressive course of cognitive impairment that is consistent with the clinical progression of VaD. Thus far, experimental studies using this model have demonstrated a direct interaction of cerebral ischemic damage and AD-type neuropathologies in the primary ischemic area. Further, coincident to the progressive decline of cognitive function, a delayed neurodegeneration in a remote area, distal to the primary ischemic area, the hippocampus, has been demonstrated in a rat endovascular MCA occlusion model. We argue that this model could be employed to study VaD and provide insight into some of the pathophysiological mechanisms of VaD