It could be a breakthrough for neurological research, experts say
THURSDAY, Nov. 8 (HealthDay News) -- The identification of a new marker is making it possible to track brain stem cells for the first time, U.S. researchers report.
The achievement is already opening doors to new research into depression, early childhood development and multiple sclerosis, the team's senior author said.
"This is a way to detect these cells in the brain, so that you can track them in certain conditions where we suspect that these cells play a certain role," explained Dr. Mirjana Maletic-Savatic, an assistant professor of neurology at the State University of New York, Stony Brook.
"This is also very applicable for situations where people envision the transplantation of stem cells into the brain," the researcher said.
The breakthrough "is very important, because it now allows us to look and see ways in which to measure changes in endogenous [natural] neural stem cells," agreed Paul Sanberg, director of the Center for Excellence for Aging and Brain Repair at the University of South Florida, in Tampa. He was not involved in the research.
The study was funded by U.S. National Institutes of Health and is published in the Nov. 9 issue of Science.
Diseases such as Alzheimer's, Parkinson's and multiple sclerosis, as well as traumatic injury or stroke, all cause debilitating injury to the human nervous system and/or brain. However, because stem cells have the potential to develop into other types of cells, scientists believe they might be manipulated to repair or replace lost cells and tissues.
In fact, key parts of the brain already produce their own stem cells, also called progenitor cells.
"There are two major areas where you can find them in the brain -- one is the center for learning and memory, called the hippocampus, and the other is around the brains' ventricles," Maletic-Savatic explained.
Like other adult stem cells in the body, these cells are held in reserve, so they can develop into new or replacement cells -- in this case, brain cells.
Stem cells in the hippocampus are particularly useful, because humans keep collecting memories. "Memories always change," Sanberg pointed out, so the brain needs new cells with which to store and interpret them.
But research in this area has been stymied by the fact that scientists haven't had any means of tracking neural stem cells. A noninvasive technology called magnetic resonance spectroscopy (MRS) has long been used to track the brain's two dominant cell types -- neurons and glial cells -- because scientists discovered molecular markers that reliably identify them on MRS.
But a marker for brain stem cells has remained elusive -- until now.
Using cutting-edge scanning and computer technology, Maletic-Savatic's team has discovered a chemical signature -- as yet unnamed -- that distinctly characterizes neural stem cells. "We think that it's a complex lipid or lipoprotein," the Stony Brook researcher said. Further investigation is under way to define and describe the molecule's identity, she added.
In MRS imaging studies in mice and rats, as well as in healthy human volunteers, the researchers tracked the quantity and location of neural progenitor cells in the brain. They even transplanted some of these cells into an adult rat's brain and used MRS to verify the transplant's location.
And in another first, Maletic-Savatic's team compared the concentrations of neural progenitor cells in the brains of young children, adolescents and adult humans. They found that -- as had been suspected from animal studies -- the number of these cells in the brain decreases markedly with age.
"We were actually really surprised that there was such a dramatic decline," Maletic-Savatic said.
The researcher said she's already planning to use the new tracking technology in a variety of neurological studies.
For example, it is suspected that antidepressants work by boosting the creation of new brain cells. With that in mind, Maletic-Savatic's team will use MRS to "clarify whether abnormalities in these progenitors have any role in causing depression," she said.
And, because she is primarily a pediatric neurologist, Maletic-Savatic said she is also planning a study looking at the cells' role in early brain development, "particularly in premature babies who can develop cerebral palsy and mental retardation."
Finally, multiple sclerosis patients may also benefit from MRS-guided research into neural stem cells.
"We are now doing a study that already started a year ago on patients with MS, and we plan to prospectively follow them and see whether we can use this biomarker as a prognostic tool," Maletic-Savatic said.
Research into a wide variety of brain disorders could also benefit from this type of stem cell research she added. Tracking stem cells in the brain has obvious implications for research into stem cell transplantation, but Maletic-Savatic said breakthroughs in that area are probably years away.
"On the other hand, if we find drugs or ways that can stimulate your own endogenous cells, that would be even better," she said.
Sanberg agreed that the ability of researchers to track neural stem cells is a boon to brain research.
"To be able to show that you are increasing neurogenesis in the brain through your treatment -- through drugs that induce neurogenesis -- that's going to be very important," he said. "This is a really strong first step."
Find out more on stem cells at the U.S. National Institutes of Health.
SOURCES: Mirjana Maletic-Savatic, M.D., Ph.D., assistant professor, neurology, State University of New York, Stony Brook; Paul Sanberg, Ph.D., distinguished university professor and director, Center of Excellence for Aging and Brain Repair, University of South Florida College of Medicine, Tampa; Nov. 9, 2007, Science
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