In the adult brain, neural stem cells have been found in two major niches: the dentate gyrus and the subventricular zone [corrected]. Neurons derived from these stem cells contribute to learning, memory, and the autonomous repair of the brain under pathological conditions. Hence, the physiology of adult neural stem cells has become a significant component of research on synaptic plasticity and neuronal disorders. In addition, the recently developed induced pluripotent stem cell technique provides a powerful tool for researchers engaged in the pathological and pharmacological study of neuronal disorders. In this review, we briefly summarize the research progress in neural stem cells in the adult brain and in the neuropathological application of the induced pluripotent stem cell technique.
Hippocampus ; cytology ; metabolism ; Humans ; Induced Pluripotent Stem Cells ; cytology ; metabolism ; Models, Biological ; Neural Stem Cells ; cytology ; metabolism ; transplantation ; Neurodegenerative Diseases ; metabolism ; pathology ; prevention & control ; Neurogenesis ; Signal Transduction

Human embryonic stem cells (hESCs) are pluripotent cells that have the ability of unlimited self-renewal and can be differentiated into different cell lineages, including neural stem (NS) cells. Diverse regulatory signaling pathways of neural stem cells differentiation have been discovered, and this will be of great benefit to uncover the mechanisms of neuronal differentiation in vivo and in vitro. However, the limitations of hESCs resource along with the religious and ethical concerns impede the progress of ESCs application. Therefore, the induced pluripotent stem cells (iPSCs) via somatic cell reprogramming have opened up another new territory for regenerative medicine. iPSCs now can be derived from a number of lineages of cells, and are able to differentiate into certain cell types, including neurons. Patient-specifi c iPSCs are being used in human neurodegenerative disease modeling and drug screening. Furthermore, with the development of somatic direct reprogramming or lineage reprogramming technique, a more effective approach for regenerative medicine could become a complement for iPSCs.
Cell Differentiation ; Cell Lineage ; Cell Transdifferentiation ; Cellular Reprogramming ; drug effects ; Embryonic Stem Cells ; cytology ; Humans ; Induced Pluripotent Stem Cells ; cytology ; transplantation ; Neural Stem Cells ; cytology ; transplantation ; Neurodegenerative Diseases ; therapy ; Regenerative Medicine ; Transcription Factors ; genetics ; metabolism

With their capability to undergo unlimited self-renewal and to differentiate into all cell types in the body, human embryonic stem cells (hESCs) hold great promise in human cell therapy. However, there are limited tools for easily identifying and isolating live hESC-derived cells. To track hESC-derived neural progenitor cells (NPCs), we applied homologous recombination to knock-in the mCherry gene into the Nestin locus of hESCs. This facilitated the genetic labeling of Nestin positive neural progenitor cells with mCherry. Our reporter system enables the visualization of neural induction from hESCs both in vitro (embryoid bodies) and in vivo (teratomas). This system also permits the identification of different neural subpopulations based on the intensity of our fluorescent reporter. In this context, a high level of mCherry expression showed enrichment for neural progenitors, while lower mCherry corresponded with more committed neural states. Combination of mCherry high expression with cell surface antigen staining enabled further enrichment of hESC-derived NPCs. These mCherry(+) NPCs could be expanded in culture and their differentiation resulted in a down-regulation of mCherry consistent with the loss of Nestin expression. Therefore, we have developed a fluorescent reporter system that can be used to trace neural differentiation events of hESCs.
Animals ; Cell Differentiation ; Cell Line ; Embryonic Stem Cells ; cytology ; metabolism ; transplantation ; Gene Knock-In Techniques ; Genes, Reporter ; Homologous Recombination ; Humans ; Luminescent Proteins ; genetics ; Mice ; Mice, SCID ; Nestin ; genetics ; Neural Stem Cells ; cytology ; metabolism ; Neurons ; cytology ; metabolism ; Teratoma ; pathology

The transplantation of neural precursor cells (NPCs) is known to be a promising approach to ameliorating behavioral deficits after stroke in a rodent model of middle cerebral artery occlusion (MCAo). Previous studies have shown that transplanted NPCs migrate toward the infarct region, survive and differentiate into mature neurons to some extent. However, the spatiotemporal dynamics of NPC migration following transplantation into stroke animals have yet to be elucidated. In this study, we investigated the fates of human embryonic stem cell (hESC)-derived NPCs (ENStem-A) for 8 weeks following transplantation into the side contralateral to the infarct region using 7.0T animal magnetic resonance imaging (MRI). T2- and T2*-weighted MRI analyses indicated that the migrating cells were clearly detectable at the infarct boundary zone by 1 week, and the intensity of the MRI signals robustly increased within 4 weeks after transplantation. Afterwards, the signals were slightly increased or unchanged. At 8 weeks, we performed Prussian blue staining and immunohistochemical staining using human-specific markers, and found that high percentages of transplanted cells migrated to the infarct boundary. Most of these cells were CXCR4-positive. We also observed that the migrating cells expressed markers for various stages of neural differentiation, including Nestin, Tuj1, NeuN, TH, DARPP-32 and SV38, indicating that the transplanted cells may partially contribute to the reconstruction of the damaged neural tissues after stroke. Interestingly, we found that the extent of gliosis (glial fibrillary acidic protein-positive cells) and apoptosis (TUNEL-positive cells) were significantly decreased in the cell-transplanted group, suggesting that hESC-NPCs have a positive role in reducing glia scar formation and cell death after stroke. No tumors formed in our study. We also performed various behavioral tests, including rotarod, stepping and modified neurological severity score tests, and found that the transplanted animals exhibited significant improvements in sensorimotor functions during the 8 weeks after transplantation. Taken together, these results strongly suggest that hESC-NPCs have the capacity to migrate to the infarct region, form neural tissues efficiently and contribute to behavioral recovery in a rodent model of ischemic stroke.
Animals ; Apoptosis ; Cell Differentiation ; *Cell Movement ; Embryonic Stem Cells/cytology/metabolism/*transplantation ; Glial Fibrillary Acidic Protein/genetics/metabolism ; Humans ; Infarction, Middle Cerebral Artery/metabolism/pathology/physiopathology/*surgery ; Male ; Neural Stem Cells/cytology/metabolism/*transplantation ; *Psychomotor Performance ; Rats ; Rats, Sprague-Dawley ; Receptors, CXCR4/genetics/metabolism

BACKGROUNDOur previous studies have indicated that the beneficial effects of grafting neural stem cells (NSCs) overexpressing glial cell line-derived neurotrophic factor (GDNF) in rats after stroke. However, the underlying mechanisms are highly debatable. In this study, we investigated whether neurogenesis, Akt, and extracellular signal-regulated kinase 1/2 (Erk1/2) signaling were involved in this process.

METHODSTransient ischemic stroke were induced by occluding middle cerebral artery for 2 hours and reperfusion. At 3 days after reperfusion, GDNF/NSCs, NSCs, and vehicle were administered. Immunohistochemical staining was used to evaluate neurogenesis by nestin antibody; phosphorylation of Akt and Erk1/2 was investigated by Western blotting analysis.

RESULTSTransplantation of GDNF/NSCs and NSCs significantly increased nestin-positive cells compared to control group (vehicle) from 1 to 7 weeks after reperfusion, and GDNF/NSCs showed stronger effect than NSCs at 2 and 3 weeks after reperfusion. Meanwhile, enhanced phosphorylation level of Erk1/2 was observed in the GDNF/NSCs and NSCs groups compared with control group, and phosphorylation level of Erk1/2 in GDNF/NSCs group was remarkably higher than that of NSCs group at any given time. In contrast, expression of mitogen-activated protein kinase phosphatase-1 (MKP-1), known as inhibitor of Erk1/2 signaling, was significantly decreased in the GDNF/NSCs and NSCs groups compared with the control group. Moreover, much enhanced and prolonged phosphorylation level of Akt of GDNF/NSCs group was detected compared with control and NSCs group.

CONCLUSIONGrafting GDNF/NSCs enhances neurogenesis and activates Akt and Erk1/2 signaling, that may provide the potential for GDNF/NSCs in stroke treatment.

Animals ; Glial Cell Line-Derived Neurotrophic Factor ; metabolism ; Male ; Mitogen-Activated Protein Kinase 1 ; metabolism ; Mitogen-Activated Protein Kinase 3 ; metabolism ; Neural Stem Cells ; cytology ; metabolism ; Neurogenesis ; physiology ; Phosphorylation ; Proto-Oncogene Proteins c-akt ; metabolism ; Rats ; Rats, Sprague-Dawley ; Stem Cell Transplantation ; Stroke ; metabolism ; therapy