October 25, 2004
New studies in mice point to scrambled brain signals as a possible underlying contributor to the devastating memory loss that occurs in Alzheimer's disease. The findings could help scientists to explore what goes wrong in the brains of those afflicted with Alzheimer's and one day lead to new treatments for those with dementia and other serious ailments affecting the brain and nervous system.
Researchers at the Johns Hopkins Medical Institute in Baltimore, Maryland based their findings on studies carried out on mouse stem cells, a type of primitive cell that has the ability to grow and transform into cells of many different forms and functions. Stem cells have been much in the news lately and a source of recent ethical and political controversy, since some forms are obtained from human embryos. In the current study, investigators used mouse stem cells taken from the olfactory bulb, a region of the brain that controls the sense of smell.
Researchers implanted stem cells obtained from the olfactory brain region into the brains of mice afflicted with a disease that resembles the inherited form of Alzheimer's that runs in some human families. They found that particular areas of the brain sent out signals that caused the transplanted cells to migrate and behave in unusual ways.
"In normal adult mice, stem cells taken from the olfactory bulb returned to the olfactory bulb -- they returned to where they belong -- even though they had come from a different mouse," says Lee Martin, Ph.D., associate professor of pathology and neuroscience at Johns Hopkins. "In mice with Alzheimer's disease, the stem cells went all over the place within the brain, responding to a multitude of signals whose identities we don't even know."
Remarkably, the researchers note, the stem cells were attracted to areas of the brain affected by amyloid plaques, the abnormal bundles of protein that crop up throughout the brains of those with Alzheimer's disease. Whether this occurs with stem cells in the brains of Alzheimer's patients is not known. Nor is it known whether this unusual movement reflects a chaotic brain environment or the brain's attempt at repair. These questions require further research.
The researchers believe that olfactory stem cells may potentially prove useful for brain disorders, other than Alzhiemer's, that tend to target particular types of brain cells. For example, stem cells taken from the brains of the olfactory region in people may one day prove useful for the shaking and stiffness of Parkinson's disease or the slowly progressive degeneration of amyotrophic lateral sclerosis (Lou Gehrig's disease).
The research was carried out in mice, and as with much basic research in animals, it may take years for new treatments to emerge in people. The findings, however, illustrate the importance of basic scientific research aimed at uncovering the causes of Alzheimer's disease. The Fisher Center for Alzheimer's Research Foundation is leading the way in funding new research into the underlying causes of Alzheimer's disease, which now afflicts some four and a half million Americans.
Zhiping Liu, Ph.D., 2004 Annual Meeting of the Society for Neuroscience. The Johns Hopkins Medical Institutions Office of Public Affairs. The ALS Association.