March 22, 2005
Adult Stem Cells Can Produce Brain Cells
In chick embryos, specific chemical environment brings results
HealthDay News -- Experiments involving chicken eggs may have hatched a major advance in stem cell research, as investigators watched adult human stem cells develop into functioning brain cells.
Until now, that is.
"We found that bone marrow stem cells did make neurons in the environment of the regenerating embryonic [chick] spinal cord," said senior researcher Joel C. Glover, of the Institute of Basic Medical Science at the University of Oslo, in Norway.
"This happened at a much higher rate than had been observed in any other experimental system," he added.
The key to the success of this model lies in as-yet-unidentified compounds within the quickly developing "microenvironment" of the embryonic spinal cord, said Paul Sanberg, a professor of neurosurgery and director of the University of South Florida's Center for Aging and Brain Repair.
Sanberg, an expert in this kind of research, believes that if scientists can identify those compounds, they might then be able to use them as a kind of cellular fertilizer -- encouraging adult stem cells to generate into human neurons.
"This study really shows that the microenvironment a stem cell is placed in is really very critical for defining how that stem cell will work," he said.
The findings appear in this week's issue of the Proceedings of the National Academy of Sciences.
According to Glover, his team knew that "the spinal cord of the chicken embryo could regenerate rapidly after an injury, to make many new neurons." So he wondered if, "perhaps the same environment might stimulate [human] bone marrow stem cells to make neurons?"
The Norwegian group tested that theory using fertilized chicken eggs. They first caused injury to the embryo's developing spinal cord. Then they introduced adult stem cells from human bone marrow into the affected area.
Not only did these stem cells quickly develop into neurons to repair the site of injury, "we were able to show for the first time that these neurons were really functional," Glover said.
"They had the right shape, they could generate nerve impulses, and they received contacts from other neurons," he said.
The next step, according to Glover, will be experiments aimed at identifying exactly which compounds within this microenvironment are pushing adult stem cells to turn into neurons.
"We speculate that a number of so-called neural growth factors, which are present in the chicken embryo spinal cord and presumably boost neuron formation during regeneration, are likely candidates," Glover said.
According to Sanberg, the finding also suggests the lowly chicken might someday be a real lifesaver for humans stricken with spinal cord injury or degenerative brain diseases such as Alzheimer's or Parkinson's.
The pharmaceutical industry, for example, "already uses the chick embryo model to make vaccines and all sorts of things, because you can have a lot of these egg models in place, whereas rat models are much more expensive," Sanberg said. "So, as we try and understand how to make more neurons out of bone marrow, this is a very interesting model and one that could be ramped up commercially."
However, the key finding remains the fact that adult stem cells can be pushed to develop into brain cells, given the right biochemical mix.
"Bone marrow stem cells from adults are very attractive for this because they can be obtained easily, they are numerous, and they have already been studied and used in clinical treatments for blood and immune disorders for many years," Glover said.
Use of adult stem cells would also get around ethical and moral issues that continue to dog the use of human embryonic stem cells -- although Glover stressed that, in many cases, embryonic stem cell research remains crucial.
Nevertheless, he said, "if we can find out how to make neurons from bone marrow stem cells in a cell culture dish, we'd have a readily accessible source of neurons for brain repair."
"This will take a lot of work," he added. "But at least now it seems possible."
For more on the promise of stem cells, head to the National Institutes of Health.