The potential for the therapeutic application of stem cells has occupied scientists in various fields for many years. Now, researchers at the University of California have demonstrated that neural stem cells may help to improve memory after brain injury. In the study, published in the October 31st edition of the Journal of Neuroscience, mice with brain injuries showed enhanced memory up to three months after receiving stem cell treatment. Matthew Blurton-Jones and his colleagues performed the experiments on mice with lesions on the hippocampus, an area of the brain vital for creating long-term memories.
To begin with, they tested the place recognition ability of the brain injured mice, compared with healthy animals. Memory for places is known to rely on the hippocampus and in the test the mice with brain injuries remembered their surroundings about 40 per cent of the time, compared with the 70 per cent recall of the healthy mice. The scientists then injected both healthy and injured mice with 200,000 neural stem cells. The cells were engineered to appear green under ultraviolet light so their migration could be tracked. Three months later, the mice were re-tested on place recognition. The mice with brain injuries now remembered their surroundings about 70 per cent of the time - the same as healthy mice.
Stem cells are usually used for their ability to develop into other kinds of cells and, in this case, it was expected that they would develop into neurons and replace the cells damaged by injury.
However, only about four per cent of the stem cells developed into neurons. Instead, the scientists found that in healthy mice the stem cells migrated throughout the brain, whereas in the injured animals they congregated at the damaged hippocampus. Instead of replacing the damaged cells, they appeared to surround and support the damaged areas. "We think the stem cells are enhancing the local brain microenvironment", Blurton-Jones said. "We have evidence to believe that the stem cells provide support to vulnerable and injured neurons, keeping them alive and functional by making beneficial proteins called neurotrophins". If neurotrophins are indeed the key to the improvement, in the future scientists could attempt to create a drug that facilitates the release or production of these proteins.
Reference: Blurton-Jones et al. (2007). Neural stem cells improve memory in an inducible mouse model of neuronal loss. The Journal of Neuroscience, October 31st 2007, 27(44),11925-11933.
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