Stem cells have two characteristic and essential properties:

  1. Self-renewal. They can divide to give rise to another stem cell.
  2. Potency. They are capable of differentiating into specialized cells.

Totipotent cells are stem cells that are capable of differentiating into all cell types in the entire organism. Pluripotent cells are descendant of totipotent cells, and are capable of differentiating into any of the three germ layers: endoderm, mesoderm and ectoderm. Further down the stem cell hierarchy are the progenitor cells whose ‘fate’ is somewhat determined. Progenitor cells have limited potency and differentiate into a specific lineage.

StemCellBasics
The fundamentals of a stem cell.

The neural progenitor cells (NPCs) are responsible for generating all the cell types that constitute the nervous system. Neuroepithelial cells are the earliest form of NPCs and are considered to be the stem cells of the whole nervous system. Through the timeline of development, the neuroepithelial cells are transformed into elongated radial glial cells (RG), an intermediate cell type that differentiates into more specific, lineage-determined cells of the brain. Each early RG cell divides into another RG cell and an immature neuronThe functional unit of the nervous system, a nerve cell that... More, which migrates out to attain maturity. Once neurons are produced, the late RG cells differentiate into glial cells – astrocytesStar-shaped glial cells that have a number of functions, inc... More and oligodendroglia.

NeuralStemCells
Neural stem cells during development and their differentiation fates.

While most neurogenesis ends around birth, some neural stem cells are maintained in specialized niches in the adult mammalian brain. A stem cell niche is a specialized microenvironment where the stem cell resides. Various transcriptional factors in the niche are important for stem cell survival, to retain their “stemness,” and to determine the differentiation of the housed stem cells. Much of the data about stem cell niches come from rodent research. Illustrated below are the endogenous adult stem cell niches in the rodent brain:

  1. The Ventral-Subventricular zone (V-SVZ) of the lateral ventricles; which are responsible for generating olfactory bulb neurons
  2. The subgranular zone (SGZ); which are involved in hippocampal neurogenesis
StemCellNiche
Endogenous stem cell niches in the rodent brain.

The endogenous stem cell niche is known to change in response to neuronal injury like cerebral ischemia or multiple sclerosis (V-SVZ). There is also a modulation in neurogenesis during mood regulation like during anxiety or stress (SGZ).

The capacity of these stem cell niches to generate neurons, albeit relatively limited, is promising for the development of therapeutic strategies towards neuronal repair. You can learn more about neural stem cells, the niche and its implications in brain repair at Dr. Fiona Doetsch’s Presidential Lecture titled, ‘Stem Cells in the Brain: Glial Identity and Niches,’ today between 5:15–6:25 PM (WCC Hall D) at the Society for Neuroscience meeting in Washington, D.C.

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References:

Silva-Vargas V. & Fiona Doetsch (2014). A New Twist for Neurotrophins: Endothelial-Derived NT-3 Mediates Adult Neural Stem Cell Quiescence, Neuron, 83 (3) 507-509. DOI: http://dx.doi.org/10.1016/j.neuron.2014.07.029

Maldonado-Soto A.R., Derek H. Oakley, Hynek Wichterle, Joel Stein, Fiona K. Doetsch & Christopher E. Henderson (2014). Stem Cells in the Nervous System, American Journal of Physical Medicine , 93 S132-S144. DOI:http://dx.doi.org/10.1097/phm.0000000000000111

Images made by Anita Ramanathan.

Anita

Anita met neuroscience during her undergraduate project, and it was love at first sight.While majoring in biotechnology at the B.M.S. College of Engineering, Bangalore, she had the opportunity to learn about biochemical subtyping as a method for biomarker discovery in neurodevelopmental disorders.She then pursued a Master’s in Biochemistry and Molecular Biology at USC.During her thesis project, her interest in translational neuroscience further evolved as she studied a kinase pathway (PI3K) highly implicated in autism.She currently belongs to the Neuroscience Graduate Program at USC and works on components of the blood-brain barrierA barrier between the brain itself and the blood supply of ... More and its integrity in animal models of neurological disorders. Outside the lab, Anita is very enthusiastic about educational and scientific storytelling! Some of her parallel interests include consumer psychology and behavior.

Anita

View posts by Anita
Anita met neuroscience during her undergraduate project, and it was love at first sight. While majoring in biotechnology at the B.M.S. College of Engineering, Bangalore, she had the opportunity to learn about biochemical subtyping as a method for biomarker discovery in neurodevelopmental disorders. She then pursued a Master’s in Biochemistry and Molecular Biology at USC. During her thesis project, her interest in translational neuroscience further evolved as she studied a kinase pathway (PI3K) highly implicated in autism. She currently belongs to the Neuroscience Graduate Program at USC and works on components of the blood-brain barrier and its integrity in animal models of neurological disorders. Outside the lab, Anita is very enthusiastic about educational and scientific storytelling! Some of her parallel interests include consumer psychology and behavior.

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