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Konstantinos Meletis, a researcher at MIT’s Picower Institute for Learning and Memory has identified stem cells within the spinal cord that may lead to a new, non-surgical treatment for spinal-cord injuries.
The stem cells divide into more healing cells and fewer scarring cells
following an injury.
The work by Meletis, reported in the July issue of the journal PLoS (Public Library of Science) Biology,
and colleagues at the Karolinska Institute in Sweden could lead to drugs that might restore some mobility
to the 30,000 people worldwide affected each year with spinal-cord
injuries.
Stem cells differentiate in a developing embryo 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 research 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.
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. See link (opens new window)
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