What are neural progenitor cells? Where are they found in the brain and spinal cord?
Neural stem cells (NSCs) are a type of multipotent stem cells that originate in the Central Nervous System (CNS, the spinal cord and brain). Multipotent means they have the ability to differentiate more than one type of cell. As with progenitor cells (more later!) stem cells in the mature adult play a role in repair, generate and change nervous system function. This is very interesting as it implies the CNS is capable of repair. Let’s dive in and explore this!
Neurogenesis: Fact or Fiction?
Historically, it was thought that the brain was incapable of cell regeneration. While the skin and the liver were known to repair themselves once damaged, it was thought that the cells of the brain were incapable of mitosis. Thus we thought we were stuck with what we had and that injury or disease resulting in cell damage and death was irreversible.
In the 1960’s, some reports showed limited evidence of renewal of certain cell types in certain mammals. In 1998, Eriksson et al. showed that neurogenesis occured in an adult human brain, specifically in the hippocampus. The hippocampus is the center of emotion, memory, and the autonomic nervous system (the component of the nervous system responsible controlling non-voluntary bodily functions, such as digestion and breathing). Since then, evidence of neurogenesis has been found in several other regions of the CNS including the developing spinal cord. The brain does not, however, have the same regenerative abilities as other parts of the body. Neuroregeneration in the mature mammalian brain appears to be limited to certain microenvironments within the CNS.
Neural Stem Cells and Neural Progenitor Cells are the same thing right?
Ah so many scientific misunderstandings so little time!
In short, no, no, no: NSCs and neural progenitor cells (NPCs) are not the same thing and anyone who tells you otherwise needs a stern talking to. Neither are synonymous with neural precursor cells either. However, they are related!
Let’s clear this up once and for all.
|Pro Tip: neural stem cells, neural progenitor cells and neural precursor cells are often used interchangeably. However the terms do have distinct meanings!
So where do neural precursor cells fit in? When referring to a collection of cells that contains both neural stem cells and neural progenitor cells, we refer to neural precursor cells.
NPCs develop from the neuroectoderm (develops into the nervous system) during embryonic development. NPCs differentiate into neurons and glial cells, like astrocytes and oligodendrocytes. During embryogenesis, NSCs can be found in nearly all parts of the human CNS however in the mature CNS they are found primarily in the subventricular zone (SVZ) which lines the lateral ventricles of the forebrain, and the dentate gyrus, a substructure of the hippocampal formation. Further research into the stem cells present in the SVZ and the dentate gyrus in mice and in in vitro models can be read here.
As you can imagine, there is much interest in harnessing the regenerative abilities of NSCs for cases of injury to the brain as in case like Traumatic-Brain Injury (TBI) and Spinal Cord Injuries and in neurodegenerative disease, such as Alzheimer’s Disease and Parkinson’s Disease. As with other forms of stem cell research, we’re in the early days. There are some ongoing and recently completed clinical trials for:
- Amyotrophic Lateral Sclerosis (ALS)
- Malignant Glioma
- Cerebral Palsy
- Spinal Cord Injury
- Brain Metastases
- Parkinson’s Disease
- Lower Limb Ischaemia
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Britannica’s quick overview of neural stem cells
History of the discoveries around neurogenesis
2013 Perspective on Neural Stem Cells published in Neuron