MIT identifies cells for spinal-cord repair
Could lead to nonsurgical treatment for injuries
CAMBRIDGE, Mass. — A researcher at MIT's Picower Institute for
Learning and Memory has pinpointed stem cells within the spinal cord
that, if persuaded to differentiate into more healing cells and fewer
scarring cells following an injury, may lead to a new, non-surgical
treatment for debilitating spinal-cord injuries.
The work, reported in the July issue of the journal PLoS (Public
Library of Science) Biology, is by Konstantinos Meletis, a
postdoctoral fellow at the Picower Institute, and colleagues at the
Karolinska Institute in Sweden. Their results could lead to drugs
that might restore some degree of mobility to the 30,000 people
worldwide afflicted each year with spinal-cord injuries.
In a developing embryo, stem cells differentiate into all the
specialized tissues of the body. In adults, stem cells act as a
repair system, replenishing specialized cells, but also maintaining
the normal turnover of regenerative organs such as blood, skin or
intestinal tissues.
The tiny number of stem cells in the adult spinal cord proliferate
slowly or rarely, and fail to promote regeneration on their own. But
recent experiments show that these same cells, grown in the lab and
returned to the injury site, can restore some function in paralyzed
rodents and primates.
The researchers at MIT and the Karolinska Institute found that neural
stem cells in the adult spinal cord are limited to a layer of cube-
or column-shaped, cilia-covered cells called ependymal cells. These
cells make up the thin membrane lining the inner-brain ventricles and
the connecting central column of the spinal cord.
"We have been able to genetically mark this neural stem cell
population and then follow their behavior," Meletis said. "We find
that these cells proliferate upon spinal cord injury, migrate toward
the injury site and differentiate over several months."
The study uncovers the molecular mechanism underlying the tantalizing
results of the rodent and primate and goes one step further: By
identifying for the first time where this subpopulation of cells is
found, they pave a path toward manipulating them with drugs to boost
their inborn ability to repair damaged nerve cells.
"The ependymal cells' ability to turn into several different cell
types upon injury makes them very interesting from an intervention
aspect: Imagine if we could regulate the behavior of this stem cell
population to repair damaged nerve cells," Meletis said.
Upon injury, ependymal cells proliferate and migrate to the injured
area, producing a mass of scar-forming cells, plus fewer cells called
oligodendrocytes. The oligodendrocytes restore the myelin, or
coating, on nerve cells' long, slender, electrical impulse-carrying
projections called axons. Myelin is like the layer of plastic
insulation on an electrical wire; without it, nerve cells don't
function properly.
"The limited functional recovery typically associated with central
nervous system injuries is in part due to the failure of severed
axons to regrow and reconnect with their target cells in the
peripheral nervous system that extends to our arms, hands, legs and
feet," Meletis said. "The function of axons that remain intact after
injury in humans is often compromised without insulating sheaths of
myelin."
If scientists could genetically manipulate ependymal cells to produce
more myelin and less scar tissue after a spinal cord injury, they
could potentially avoid or reverse many of the debilitating effects
of this type of injury, the researchers said.
###
This study was supported by grants from the Swedish Research Council,
the Swedish Cancer Society, the Foundation for Strategic Research,
the Karolinska Institute, EuroStemCell and the Christopher and Dana
Reeve Foundation.
Public release date: 21-Jul-2008
Contact: Teresa Herbert
therbert@mit.
617-258-5403
Massachusetts Institute of Technology
http://www.eurekale
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StemCells subscribers may also be interested in these sites:
Children's Neurobiological Solutions
http://www.CNSfoundation.org/
Cord Blood Registry
http://www.CordBlood.com/at.cgi?a=150123
The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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