Neural stem cells (NSCs) belong to stem cells with the ability to generate the main cells of the nervous system: neurons, astrocytes, and oligodendrocytes. NSCs can be derived from the ectoderm layer of embryo. During nervous system development, NSCs produce neural progenitors first. Then the progenitors differentiate into projection neurons, following small interneurons and glia. In the end, only a few parts of NSCs remain in the mature brain. Epidermal growth factor (EGF) and fibroblast growth factor (FGF) can promote growth of neural progenitor cells.
In humans, the existence of NSCs with multipotent differentiation capability has also been reported in the embryonic and adult human brain. These primary neural stem cells found in the ventricular zone of the human brain continue to divide asymmetrically and give rise to the intermediate progenitor cells in the sub ventricular zone. Developmentally, these cells are produced by sub ventricular cells in the brain and spinal cord that give rise to committed oligodendrocyte progenitor cells (OPCs) that divide and migrate throughout the CNS. These OPCs can then terminally differentiate into post-mitotic, pre-myelinating oligodendrocytes which, under appropriate environmental conditions, will further mature and myelinate nearby receptive axons. Oligodendrocyte progenitor cells have been defined as cells expressing NG2 and/or PDGFRA on their surface. These cells have been shown to respond to environmental factors to develop into oligodendrocytes capable of producing new myelin, and yet they also retain multi-lineage plasticity and can give rise to neurons and astrocytes when removed from the adult parenchymal environment. A substantial population of these OPCs remains in an undifferentiated state in the adult human brain as parenchymal glial progenitor cells and are recruited for repair of damaged CNS tissue. These adult OPCs can be potential targets for cell-based treatment of demyelinating diseases.
NSCs are involved in learning and hippocampal plasticity. They also supply neurons to the olfactory bulb in mice model. In vitro cultured NSCs help modeling of nervous system development and diseases. NSCs are also applied for the treatment of neurodegenerative diseases and nervous system injury.
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