Brains Cells May Regenerate After Radiotherapy

Scientists have long believed that healthy brain cells, once damaged by radiation designed to kill brain tumors, cannot regenerate. However, new research in lab mice suggests that neural stem cells, the body’s source of new brain cells, are resistant to radiation, and can be woken up from a hibernation-like state to reproduce and generate new cells able to migrate, replace damaged cells, and possibly restore lost function.

“Despite being hit hard by radiation, it turns out that neural stem cells are like the special forces, on standby waiting to be activated,” noted Alfredo Quiñones-Hinojosa, MD, a professor of neurosurgery at the Johns Hopkins University School of Medicine (Baltimore, MD, USA), and leader of a study described online in the journal Stem Cells. “Now we might figure out how to unleash the potential of these stem cells to repair human brain damage.”

The findings, Dr. Quiñones-Hinojosa reported, may have impact for not only for brain cancer patients, but also for people with progressive neurologic disorders such as multiple sclerosis (MS) and Parkinson’s disease (PD), in which cognitive functions worsen as the brain suffers permanent damage over time.

The researchers examined the impact of radiation on mouse neural stem cells by assessing the mice’s responses to a subsequent brain injury. To do the research, the researchers used a device designed and used only at Johns Hopkins that effectively simulates localized radiation used in human cancer therapy. Other technology, according to the scientists, uses too much radiation to precisely impersonate the clinical experience of brain cancer patients.

In the weeks after radiation, the researchers injected the mice with lysolecithin, a compound that caused brain damage by inducing a demyelinating brain lesion, much like that present in MS. They found that neural stem cells within the irradiated subventricular zone of the brain generated new cells, which rushed to the damaged site to rescue newly injured cells. One month later, the new cells had integrated into the demyelinated area where new myelin, the protein insulation that protects nerves, was being produced.

“These mice have brain damage, but that doesn’t mean it’s irreparable,” Dr. Quiñones-Hinojosa said. “This research is like detective work. We’re putting a lot of different clues together. This is another tiny piece of the puzzle. The brain has some innate capabilities to regenerate and we hope there is a way to take advantage of them. If we can let loose this potential in humans, we may be able to help them recover from radiation therapy, strokes, brain trauma, you name it.”

These findings may not be all good news, however. Neural stem cells have been linked to brain tumor development, Dr. Quiñones-Hinojosa stressed. The radiation resistance his research discovered, he noted, could clarify why glioblastoma, the most lethal and aggressive form of brain cancer, is so difficult to treat with radiation.

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Johns Hopkins University School of Medicine