Exercise reduces damage after therapeutic irradiation to the brain

Researchers at the Sahlgrenska Academy in Gothenburg show for the first time that exercise helps restore stem cell growth and improves behavior in young mice that suffered damage to the brain induced by a clinically relevant dose of radiation. The researchers believe that these results are also applicable to children that have suffered damage due to radiotherapy of brain tumors.

Children that receive radiation treatment for brain tumors often develop learning and memory problems later in life that may be associated with attention deficits. These symptoms have been linked to radiation-induced damage, which not only kills cancer cells, but also stem cells that reside in the hippocampus, a region essential for proper memory function.

Dr. Andrew Naylor has previously studied the effects of physical exercise on stem cells, and Associate professor Klas Blomgren has studied the consequences of irradiation on brain cells. Together with Professor Georg Kuhn, a pioneer in the brain stem cell field, the group investigated whether physical training could counteract previously established damage to certain regions of the brain. They exposed nine-day-old mice to a radiation dose that resulted in damage to the mouse brain, similar to damage observed in human cancer patients. Half of the mice were given free access to a running wheel, which mice like to run on for extended periods of time. At 13 weeks of age, the mice were placed in an open space and were allowed to explore while their behavior was analyzed by studying a number of variables to describe their movement patterns.

The results from the study demonstrated that irradiated mice showed increased motor activity and altered movement patterns that were normalized if they were allowed to exercise. In addition, the mouse brains contained 50% more stem cells than their non-exercising counterparts. The researchers were also able to determine that newly formed nerve cells in an irradiated brain form fewer extensions, compared to a non-irradiated brain. The nerve extensions were not only fewer, but they also pointed in the wrong direction. Interestingly, if the animals were allowed to exercise, the nerve extensions were normalized. "These results suggest that irradiation-induced damage in children with brain tumors could be reduced if the child under guidance is allowed to do stimulating and fun exercise", says Professor Georg Kuhn.

The research is report in the Proceedings of the National Academy of Sciences.