November 1, 1998
La Jolla, CA – Like bubbles fizzing from fine champagne, it has long been assumed that our supply of brain cells steadily diminishes through our lives, never to be replenished. According to a landmark Salk study, however, new cells are born in human brains, even in mature individuals.
The results, published in the Nov. 1 issue of Nature Medicine, showed that new cells were generated in the brains of terminal cancer patients who had undergone a diagnostic procedure that labels actively dividing cells. Upon the patients’ death, their brains were examined for presence of the diagnostic agent BrdU (for bromodeoxyuridine) which attaches to DNA in dividing cells.
“All of the patients showed evidence of recent cell division,” said Salk Professor Fred H. Gage, senior author on the study. “It’s interesting to note that this was not a particularly young or healthy group of people, so new cell growth may usually be even more prominent than we observed.”
Before the current study, new brain cell growth had been found in adult marmoset monkeys, a lower order primate. Efforts to detect new brain cells in Old World monkeys and apes, however, with whom humans share a more recent common ancestor, had failed.
The new growth seen in humans took place in the part of the brain called the hippocampus, which has been linked by many physiological studies to learning and memory.
“At this point, it’s premature to say that the new cells are being used for learning and memory, but given their location in the brain, it seems reasonable to suggest that they likely do,” said co-author Daniel A. Peterson, a postdoctoral fellow in Gage’s group.
Previous work in Gage’s laboratory had shown that mice reared in a stimulating environment, containing toys, exercise apparatus and increased opportunities for social interaction, generated new brain cells at a greater rate than litter mates raised in standard cages. The mice with more cells also performed better on learning and memory tests involving negotiating mazes.
“At the time those results were published, people would ask me if it meant that they could literally increase their brain capacity by traveling or taking on new challenges,” said Gage. “I had to say we don’t know, given that no one had found newborn nerve cells in human brains. And we still don’t know for sure,, whether these new brain cells are functioning normally, but the current finding brings us an important step closer to thinking that we have more control over our own brain capacity then we ever thought possible previously.”
First author on the study is Peter S. Ericksson of the Sahlgrenska University Hospital in Göteborg, Sweden and spent time with Dr. Gage as a visiting scientist prior to returning to Sweden where he was instrumental in setting this study in motion. Other co-investigators include Ekaterina Perfilieva, Thomas Björk-Ericksson, and Ann-Marie Alborn of the Sahlgrenska.
Gage’s work was supported by the National Institutes of Health, the National Institute of Neurological Disorders and Stroke, the Alzheimer’s Association, and the American Federation for Aging Research. The Sahlgrenska group was supported by the Swedish Medical Research Council, the University of Göteborg, the Gunvor and Josef Anérs Stiftelse, the John and Brit Wennerströms Stiftelse for Neurologisk Forskning, the Rune and Ulla Amlövs Stiftelse for Neurologisk and Reumatologisk Forskning, NHR-fonden, Stiftelsen Göteburgs MS förenings forsknings och byggnadsfond, Stiftelsen handlanden Hjalmar Svenssons Forskningsfond, Götesborgs Läkaresällskap, Hjärnfonden, The Swedish Society of Medicine, Stiftelsen Lars Hiertas Minne, Stiftelsen Assar Gabrielssons Fond and the Edit Jacobssons Fond.
The Salk Institute for Biological Studies, located in La Jolla, Calif., is an independent nonprofit institution dedicated to fundamental discoveries in the life sciences, the improvement of human health and conditions, and the training of future generations of researchers. The Institute was founded in 1960 by Jonas Salk, M.D., with a gift of land from the City of San Diego and the financial support of the March of Dimes Birth Defects Foundation.