The researchers damaged the brains of mice and put them and some healthy animals through memory tests during the study, published in the Journal of Neuroscience. All the subjects were placed in boxes containing two objects. After the mice had become accustomed to their surroundings, they were taken out and one of the objects was moved.
When the mice were placed in the boxes again, the healthy mice spent much more time sniffing around the object that had been moved. The mice with their brains damaged spent equal time investigating both objects, indicating that they had not registered that one object had moved.
Upon being injected with nerve stem cells from newborn mice, the memories of the brain-damaged mice showed improvement. It also increased the mice's levels of synapsin, a chemical which stimulates connections between brain cells. Dr Mathew Blurton-Jones, a member of the research team, said that in previous studies, stem cells injected into the brains of animals had survived and become part of the brain circuitry.
"We've now gone one stage further in showing that, once integrated, these new neurons are able to reverse cognitive deficits associated with neurodegeneration or neuronal loss," the Daily Mail quoted him as telling New Scientist magazine. "This study shows stem cells might benefit memory in stroke or traumatic brain injury - and potentially Alzheimer's disease. This has a huge potential but we have to be cautious not to rush into the clinic too early," he added.
Dr. Blurton-Jones admitted that further studies were needed before his team could move on to humans. He revealed that the next step in his research would be to test stem cells in mice with an Alzheimer's-like disease. Clive Ballard, director of research at the Alzheimer's Society, said: "This study is a major advance which demonstrates the potential of stem cell therapies. However, the race is on to develop treatments as effective in practice as in the laboratory."
"This study relies on a very specific approach using cells grown with animal growth factors. These cells are not suitable for human treatment and major obstacles still exist in applying this to people. But we anticipate a solution over the next few years," Ballard added.
Dr Paul Sanberg, director of the Centre of Excellence for Ageing and Brain Repair at the University of South Florida College of Medicine, said: "There is clearly a therapeutic potential to this. But it has to work with older brains."