Monday, 12 August 2013

Neural stem cells may survive and regenerate after radiation therapy

It is a long held belief that healthy brain cells, once damaged by radiation designed to kill brain tumours, cannot regenerate.However, a new study on mice by researchers at Johns Hopkins indicates that neural stem cells, from which new brain cells are created, are resistant to radiation, and can be roused from a hibernation-like state to reproduce and generate new cells able to migrate, replace injured cells and potentially 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.Now we might figure out how to unleash the potential of these stem cells to repair human brain damage." says Alfredo Quiñones-Hinojosa, M.D., a professor of neurosurgery at the Johns Hopkins University School of Medicine and leader of a study described online today in the journal Stem Cells. 

The findings, adds Quiñones-Hinojosa, may have implications not only for brain cancer patients, but also for people with progressive neurological diseases such as multiple sclerosis (MS) and Parkinson's disease (PD), in which cognitive functions worsen as the brain suffers permanent damage over time.

In Quiñones-Hinojosa's laboratory, the researchers examined the impact of radiation on mouse neural stem cells by testing the rodents' responses to a subsequent brain injury. To do the experiment, the researchers used a device invented and used only at Johns Hopkins that accurately simulates localized radiation used in human cancer therapy. Other techniques, the researchers say, use too much radiation to precisely mimic the clinical experience of brain cancer patients.

In the weeks after radiation, the researchers injected the mice with lysolecithin, a substance 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. A month later, the new cells had incorporated 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. 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." said Quiñones-Hinojosa.

His findings may not be all good news, however. Neural stem cells have been linked to brain tumor development, Quiñones-Hinojosa cautions. The radiation resistance his experiments uncovered, he says, could explain why glioblastoma, the deadliest and most aggressive form of brain cancer, is so hard to treat with radiation.

Reference
Vivian Capilla-Gonzalez1, Hugo Guerrero-Cazares1, Janice M. Bonsu1, Oscar Gonzalez-Perez2, Pragathi Achanta1, John Wong3, Jose Manuel Garcia-Verdugo4, Alfredo Quiñones-Hinojosa1,* (2013). The Subventricular Zone is Able to Respond to a Demyelinating Lesion after Localized Radiation Stem Cells DOI: 10.1002/stem.1519

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