Scientists have discvoered that that forgetful mice with damage to their hippocampus - the part of the brain that lays down new memories - can have their intellects restored by injecting neural stem cells collected from newborn mice.
UC Irvine researcher Frank LaFerla and his team genetically programmed mice to develop degeneration of hippocampal nerve cells. In tests designed to measure recall of objects and an animal's surroundings, the engineered mice were significantly impaired; they showed signs of recognising their environment only 40% of the time, compared with 80% when control animals were tested. Next, the researchers injected into the hippocampi of some of the impaired animals 200,000 neural stem cells collected from the brains of newborn mice. The injected cells were programmed to produce a glowing green jellyfish protein so that the researchers could follow where the cells went in the brain. The animals were then regularly re-tested to look for signs of recovery.
After three months mice that had received stem cell transplants were remembering their surroundings 70% of the time - almost as good as control animals. In contrast, the untransplanted mice still showed memory deficits. To find out how the improvements had occurred the researchers then studied the brains of the transplanted animals. They were surprised to see that only about 4% of the cells had turned into neurones, indicating that the improvement wasn't being achieved solely through replacement of missing nerve cells. Instead the researchers think that the stem cells stimulate repair and re-wiring of the nervous system by releasing beneficial chemicals such as growth factors.
But irrespective of how it works, as Frank LaFerla points out, "our research provides clear evidence that stem cells can reverse memory loss. This gives us hope that stem cells someday could help restore brain function in humans suffering from a wide range of diseases and injuries that impair memory formation."