Translated material
Sleeping in the hippocampus
Exercise can cause nerve cells to renew themselves
The widespread assertion that nerve cells do not regenerate is incorrect, say scientists from the Max Planck Institute for Immunobiology in Freiburg.The human brain loses nerve cells throughout life. However, according to the journal Cell Stem Cell, there are, at least in mice, a number of neural stem cells in the brain that can divide into old age, creating new nerve cells. In young rodents, these cells constantly divide, but in mature mice, a huge number of these cells seem to go into a state of hibernation. However, the formation of new cells can be reactivated, for example, by exercise or during epileptic seizures.
The conclusion about the presence of such cells should also apply to humans, since nerve cells capable of dividing are also present in the adult brain.
They say there is no use teaching an old dog new tricks. For a long time, science was dominated by the theory that with age, the human brain loses the ability to learn and remember. However, stem cells found in the hippocampus, an area of the brain central to learning and memory, can produce new nerve cells throughout life. It is clear from experiments with mice that newly formed neurons are successfully integrated into the pre-existing nervous system and play an important role in learning in rodents. However, the ability to form young cells, for a still unknown reason, weakens with age.
Biologists from Freiburg and colleagues from other universities were able to explain for the first time why fewer new nerve cells are formed in the brain of an adult mouse. They were able to identify distinct populations of stem cells and thereby demonstrate that the hippocampus contains both inactive or dormant neural stem cells and active ones, i.e. active.
“In young mice,” explains one of the study participants, Verdon Taylor, a specialist from the Planck Institute, “neural stem cells divide four times more intensively than in adult rodents. However, the number of cells in older animals, although less, is not much. Therefore, we can conclude that nerve stem cells do not disappear with age, but go into reserve.”
The full factors that cause the reactivation of dormant stem cells are still unknown. However, it is already obvious that cells can be pushed to a new division. Scientists have noticed that physically active mice have more new neural stem cells than mice leading a passive lifestyle. The formation of new neurons is promoted by running and pathological brain activity, which, for example, occurs during epileptic seizures.
Different populations of stem cells are easily distinguished under a microscope. One group includes cells oriented perpendicular to the surface of the hippocampus. Most of these radial stem cells are dormant. More than 80% of the cells in the group of horizontal stem cells, which run parallel to the surface of the hippocampus, continually divide to form new cells. The remaining 20% of horizontal cells also “sleep”, but are activated from time to time. Both types of cells have active genes.
Radial and horizontal stem cells differ not only in their location. Obviously, they respond to different stimulants. In physically active animals, some radial cells emerge from hibernation and begin to divide. However, physical activity has very little effect on horizontal stem cells. As for horizontal stem cells, they are stimulated to divide, for example, by epileptic seizures.
Neural stem cells are not limited to mice. The presence of lifelong nerve cells has also been demonstrated in the human hippocampus. Scientists believe that we also have the same active and passive stem cells. It is possible that in humans passive stem cells can be activated in the same way as in mice.
German scientists do not exclude the possibility that one day it will be possible to use neural stem cells in the treatment of brain damage or degenerative diseases such as Alzheimer's disease.