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products
for human cells
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neural colony-forming cell (NCFC) assay kit
support products including dissociation reagents
background
The adult mammalian central nervous system (CNS) is composed primarily of three differentiated cell types ?neurons, astrocytes and oligodendrocytes. Astrocytes and oligodendrocytes are considered to provide a critical supporting role for optimal neuronal functioning. Neurons are considered to be the functional unit of the CNS. They are responsible for forming connections and are the communicating cells of the nervous system. Developmentally, cell genesis occurs primarily in two waves ?a prenatal wave where most of the neurons are generated and an early post-natal wave where most of the astrocytes and oligodendrocytes are generated. Once this second wave of proliferation is completed the CNS has traditionally been considered mitotically quiescent. The adult mammalian CNS?inability to replace non-functional CNS tissue makes cell death due to injury or disease devastating.
Research on brain repair has traditionally focused on keeping neurons alive following injury and promoting their ability to extend processes and establish functional cell connections. This focus was the result of a well-established dogma that the adult mammalian CNS was incapable of generating new brain cells, based on the lack of evidence supporting the contrary. However, in the early 1990𠏋 the discovery of stem cells in the embryonic and adult CNS proved the traditional theories to be incorrect.
stem cells in the central nervous system
In the simplest definition, multipotent stem cells are characterized as undifferentiated cells with the capacity for extensive proliferation that gives rise to more stem cells (exhibit self-renewal) as well as progeny that will terminally differentiate into cell types of the tissue from which they are obtained. These features make stem cells important elements in embryonic development and in adult tissue for maintaining cell number following injury and disease or natural cell turnover. Stem cells have been well characterized in a number of mammalian tissues including the hematopoietic system, skin and intestinal crypts. Traditionally, stem cells have been found and characterized in tissues that exhibit a great deal of cell turnover. Therefore, one would not expect to find stem cells in tissues that exhibit little cell turnover, such as the CNS.
Prior to 1992, proliferation studies of cultured CNS cells were generally restricted to examining the limited proliferation of neural precursors in embryonic tissue. While several types of precursors had been identified, none exhibited stem cell features. In vivo studies supported the notion that CNS proliferation occurred early in life and the adult CNS was mitotically inactive and unable to generate new cells following injury. Notable exceptions include several studies in the 1960𠏋 that clearly identified a region of the adult brain that exhibited proliferation (the forebrain subependyma).1 However, this was believed to be species specific and did not occur in higher mammals.
Growth factor responsive cells from the embryonic and adult CNS that exhibit stem cell features in vitro were isolated in the early 1990𠏋.2-4 The location of CNS stem cells in the adult brain were therefore identified.5 These studies opened the door to a new area of neurobiological research, brain repair based on the generation of new cells.
For more information, refer to Mini-Review on Neural Stem Cells.
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