The investigation
In their study of the subventricular zone, the researchers worked with healthy brain tissue from 65 tissue samples from neurosurgical resections (the margins always taken to safeguard a patient) and 45 samples from autopsies. After discovering the ribbon of astrocytes along the lining of the ventricles, they succeeded in isolating the astrocytes from the tissue's dense network of mixed brain cells. Then, they conducted a series of experiments in the culture dish that revealed these cells have the properties of adult neural stem cells (i.e., the ability to produce the various cells of a given organ, in this case the brain).
First, they showed that when the cells were exposed to growth factors they could create structures called neurospheres, raspberry-like globules that can self-perpetuate and give rise to all three brain cell types - neurons, oligodendrocytes and astrocytes. Then, they demonstrated that individual subventricular zone astrocytes, grown upon a feeding layer of normal astrocytes from the human brain cortex, could produce new neurons without requiring added growth factors.
The relative ease with which the astrocytes were driven to function as adult stem cells in the second experiment was notable, says Sanai. It suggests, he says, that some factor is being secreted by the normal cortical astrocytes that induce these adult neural stem cells to produce new neurons.
The answers await. "From the laboratory to the operating room, from mice to humans." he reflects. "Many investigators and clinicians gravitate towards stem cells because they are scientifically unique and potentially powerful. They inspire in us new hope. The first step, however, will always be to simply unde
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Contact: Jennifer OBrien
415-476-2557
University of California - San Francisco
18-Feb-2004