Group demonstrates that adult human brains grow new cells after all
By Jennifer Fisher Wilson
It was the first time that researchers had ever demonstrated human neurogenesis. Prior evidence had suggested that human neurogenesis occurred, but it wasn't until publication of research showing neurogenesis in the hippocampus that most scientists believed it.
"Contrary to accepted knowledge, previous evidence existed that new neurons were born in restricted regions of the adult brain, but resistance existed that adult neurogenesis was generalizable to primates and humans. Our results proved that neuro-genesis does occur in humans," said Fred H. Gage, director of the Laboratory of Genetics at the Salk Institute for Biological Studies in La Jolla, Calif., lead investigator for the research.
Prior to studying the human brain, the paper's authors from the Salk Institute examined neurogenesis in mice and rats. This research indicated new neuron development in adult animal brains. Encouraged that this work might carry over into humans, Gage and first author Peter Ericksson, who was on sabbatical from Sahlgrenska University Hospital in Goteborg, Sweden, searched for a way to prove whether neurogenesis occurred not only in mice and rats, but also in humans. This required establishing the generalizable relevance of the phenomenon.
The investigators established procedures for isolating dividing progenitor cells from the adult brain and examining them in culture dishes. They reasoned that since the diagnostic marker bromodeoxyuridine was used to monitor tumor progression in human patients, they might be able to examine the brains of patients treated this way. It was difficult to obtain subjects for the research, but they obtained tissue from five (plus one control) fresh postmortem brains.
Gage presented his most recent research on the functional nature of these cells at the Society for Neuroscience meeting in early November. "We have theories as to the significance of their function but no proof yet," he said. He suggested that if cells can be obtained from the adult brain and expanded in vitro, they may be used for cell replacement. "Alternatively, if we learn enough about endogenous brain neurogenesis, we may be able to induce endogenous repair," he added.
Gage's lab is working to define the spatial and temporal conditions that permit functional regeneration of the adult nervous system. They are studying the cellular and molecular mechanisms that regulate neurogenesis and cell genesis throughout the brain and spinal cord. They are also studying the environmental factors that regulate neurogenesis and mechanisms through which they act.
Jennifer Fisher Wilson (firstname.lastname@example.org) is a contributing editor for The Scientist.
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