San Francisco, CA (05/14/04)- Stem cells from human adult bone marrow
have been successfully converted into functional brain cells, putting science
closer to the possibility that one day damaged brain tissue can be repaired
by implanting new cells. Not only that, it also means that people could potentially
become their own donors, circumventing ethical issues related to other, more
controversial sources of stem cells.
Dr. Alexander Storch, professor of neurodegenerative diseases at the Technical
University in Dresden, Germany, described the research at the annual meeting
of the American Academy of Neurology here.
Stem cells are non-specialized cells that can divide and turn into other
specialized cells such as bone, brain or blood cells. While large numbers
of stem cells are present in developing embryos, smaller quantities of stem
cells occur in certain parts of the adult body, such as in the bone marrow.
It is believed stem cells in mature animals are there to help with tissue
repair.
Stem cells in adult human bone marrow are normally able to change, or differentiate,
into one of three cell types: cartilage, fat cells or bone cells, Dr. Storch
said. However, researchers in various laboratories around the world
have been working with stem cells derived from adult human bone marrow to
try to change them into other types of cells, such as nerve cells.
Some small amount of success was achieved in those laboratories, though
these other research teams attempted to convert bone marrow stem cells directly
into glial
and neuron cells, types of nerve cells found in the brain. The resulting
cells were not functional, and would not be of sufficient quality for transplantation.
Dr. Storch's team added another step and have had more success.
What researchers in Dr. Storch's laboratory did was to alter the way bone
marrow stem cells are grown in culture. Instead of trying to turn them directly
into glial and neuronal cells, the researchers instead turned the bone marrow
stem cells into another type of stem cell -- neural stem cells. To do this,
they altered the environment in the culture by using a medium that is usually
used for culturing neural stem cells. They then added growth factors. Once
the bone marrow cells stayed in the mixture for a while, they turned into
neural stem cells, also referred to as neuroprogenitor cells.
"We do not produce nerve cells or glial cells, but immature neuroprogenitors,"
Dr. Storch said. The hope is that these could be transplanted straight into
the brain where they would, in theory, turn into fully functional glia and
neuron cells.
There is already evidence that these neural stem cells are active and will
turn into the appropriate glial and neuron cells is transplanted into a brain.
Researchers found that while in suspension, the cells grow into neurospheres
(small balls or aggregates of precursor brain cells) and that they expressed,
or produced, the neural stem cell marker nestin. Both of these features were
missing in previous attempts by researchers in other laboratories.
"Our protocol generated a high yield of cells," Dr. Storch said. Plus, the
cells grew quickly. "We calculate we'd need approximately 70 days to grow
enough cells for a transplant procedure from one bone marrow biopsy. We'd
have the same quantity of cells usually transplanted in studies of Parkinson's
Disease," he said.
Scientists hope that the research may one day help treat diseases such as
Parkinson's and Alzheimer Disease, and Multiple Sclerosis, all diseases where
nerve or brain tissue is damaged.
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