Start up brain cells to stave off ageing

PHYSICAL exercise helps to regenerate brain cells that are lost due to ageing, according to a study by researchers. The scientists believe that the discovery may lead to new ways of tackling age-related memory loss, the effects of brain injuries or Alzheimer’s disease.

Until now, the conventional wisdom is that brain cells die during the course of a person’s life and cannot be replaced. But it is now known that at least some nerve cells can be replenished in the hippocampus, the brain region that plays a key role in learning and memory.

However, a large proportion of the stem cells that give rise to new neurons remain dormant in adults. The new research in mice shows that these cells can be "kick-started" into action by physical activity and epileptic seizures.

The scientists found that physically active mice developed more newborn hippocampal neurons than inactive animals. "Running promotes the formation of new neurons," said study leader Dr Verdon Taylor of the Max Planck Institute of Immunobiology in Freiburg, Germany.

Abnormal brain activity, as occurs during epileptic seizures, also appeared to trigger neuron generation. Excessive formation of new nerve cells is thought to play a role in epilepsy, said Taylor, whose research appeared in the journal Cell Stem Cell.

"In young mice, the stem cells divide four times more frequently than in older animals," Taylor said. "However, the number of cells in older animals is only slightly lower. Therefore, neuronal stem cells do not disappear with age but are kept in reserve."

In physically active mice, some previously dormant stem cells were seen to come back to life and start to divide. Other sporadically dormant stem cells were unaffected by physical activity, but awakened by epileptic seizures.

It was likely that dormant stem cells could be reactivated in humans in the same way they were in mice.