Self Assembling Fibers Help Nerve Repair
New, self-assembling,
biodegradable scaffolds could help repair and regrow damaged nerve cells,
possibly bringing new hope to victims of paralysis, scientists told United
Press International.
"This helps
raise the possibility of helping the spinal cord regenerate, a possibility
we are literally studying at this moment," said researcher John Kessler,
a neurologist at Northwestern University in Evanston, Ill.
The new technique
involves using tiny, artificial, 3-D scaffolds that can store or attract
cells. The scaffolds give neurons or nerve cells a framework on which to
rebuild. The materials typically are
biodegradable -- they dissolve
as cells multiply to fill their place.
Northwestern
materials scientist Sam Stupp and colleagues developed organic molecules
that can assemble themselves in seconds into transparent scaffolds made
of fibers only 5 to 8 nanometers -- billionths of a meter -- long. Using
the nano-scaffolds, doctors can create templates for nerve regeneration
simply by injecting ingredients into the body, instead of having to cut
a person open to surgically implant a scaffold.
"That's the
real advance here," Kessler said.
Kessler began
researching spinal cord injury after his daughter was paralyzed in a skiing
accident.
"It's not going
to by itself regenerate all problems in the nervous system," Kessler cautioned.
"I do think it's a very big step -- but it's just one step."
The investigators
experimented with neural progenitor cells from mice. These cells are the
primordial material that more complicated nerve cells found in the brain
and spinal cord emerge from, a process known as differentiation.
The research
team took the building blocks for the scaffolds and incorporated an amino acid
sequence into them known to help promote the growth of neurites, the branches
extending from nerves that help the cells talk with one another. "Think
of them as wiring," Kessler explained.
Anchoring the
amino acid sequences to the fibers is crucial, Kessler said. If the growth
promoters are injected into the scaffold after it is formed, they could
be broken down before cells can use them, or not coat cells evenly. The
fact the fibers are so tiny means they can be tightly packed together,
to surround cells with as much of the growth promoting amino acid sequence
as possible.
The scaffold
does not assemble until its ingredients make contact with ions, such as
the electrically charged molecules on the surrounding cells.
Electron microscope
images revealed the progenitor cells rapidly differentiated into neurons.
Moreover, they grew without any of the inhibitions limiting regeneration
in the body.
"The problem
with regeneration of the central nervous system -- the brain and spinal
cord -- is that the materials surrounding the cells do not allow them to
regenerate," Kessler explained. For instance, damaged nerve cells develop
what is called a glial scar around them.
"One of the
exciting things here is the scaffold unexpectedly was found to block neural progenitor
cell differentiation into astrocytes, the cells that make up the
glial scar," Kessler said.
The researchers
now are experimenting with Stupp's fibers on lab mice and rats to see if
they can help regenerate from spinal cord damage and stroke. They also
are investigating why the scaffolds inhibit differentiation.
"This is the
first major hopeful development in the direction of nerve regeneration and repair,"
National Science Foundation's polymer program director Andy Lovinger told
UPI.
Kessler added
it might be possible to tailor the nanofibers with chemicals targeting other
kinds of cells.
"The ramifications
of this work certainly far exceed what can happen in the nervous system.
There's every reason to believe it can help regenerate other organ systems,
providing the environment for what you can in essence think of as an artificial
pancreas, or for bone formation, and on an on," he noted.
Kessler said
there is commercial interest in this work, but added, "Both Dr. Stupp's
and my primary concern is not the financial impact, but its impact on patients."
--
Copyright 2004 by United
Press International.
All rights reserved.
--
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