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. Last Updated: 07/27/2016

Cell Repair Triggered in Mouse Brains

Harvard researchers have discovered molecular signals in the brain that trigger the development of new neurons in adult mice. These new cells, located in the cortex and extending down to other brain regions, suggest that these molecular signals could be targeted to coax the brain into healing itself, scientists say.

"In my working lifetime, we will have brain repair,'' said Dr. Jeffrey Macklis, an associate professor of neurology and neuroscience at Harvard's Children's Hospital and lead author of the study that will appear Thursday in the journal Nature. "In one to three decades, we may be able to repopulate the central nervous system at the cellular level.''

Macklis and his colleagues triggered apoptosis, or cell suicide, in a single layer of brain tissue in the cortex, and then followed the brain as it repaired itself. They used a substance to tag new cells as they developed and found their homes. They reported that these new neurons had axons, or extensions, that traveled a long distance to brain regions, and were still there seven months later when the study was completed. The scientists did not study whether the cells were functioning like the neurons they replaced. That work is now in progress, Macklis said.

The scientist added that he suspects that this neurogenesis, or birth of new neurons, follows on the heels of apoptosis, or cellular suicide. He explained that apoptosis leads to the expression of a series of genes usually active only during development, signalling molecules that help usher an immature cell into a full-grown adult, ready to carry out complex jobs in the brain.

These signal molecules induce the development of neuronal precursor cells, or stem cells, into mature adult cells.

In recent years, several research labs have announced the discovery of new neurons in the adult brains in both animals and humans. These neuronal precursor cells were thought to arise in two specific brain regions, the dentate gyrus and the olfactory bulb. In the current study, the scientists have discovered they can get new cells to grow and develop in the adult cortex of mice by turning on these molecular signals.

Macklis and his colleagues suspect that these stem cells have not been identified outsideof the dentate or the olfactory bulb because these molecular signals are not normally activated in this region.

However, the new study suggests it may one day be possible to manipulate these signals to repair damaged cells and treat brain diseases.

"The new neuronal cells occurred only in the cortical layer that was undergoing degeneration,'' Drs. Anders Bjorkland and Olle Lindvall of the neuroscience center at Lund University in Sweden wrote in an accompanying editorial. "These results raise the enticing possibility that the brain has a latent capacity for self-repair.''