More Breakthroughs in Research

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Walking ability improves in paralysis study

Spinal cord treatment shows promising results in rats

Updated: 9:19 a.m. ET May 24, 2004MIAMI - Rats with spinal cord

injuries regained 70 percent of their normal walking function with a

three-part treatment hailed as a breakthrough in paralysis research

at the University of Miami School of Medicine.

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The study at the university's Miami Project to Cure Paralysis, due to

be published on Monday in the June issue of the journal Nature

Medicine, produced results " by far greater than what we've seen in

anything else, " said the principal researcher, Dr. Bartlett

Bunge.

" It opens up a potential new avenue of treatment for human spinal

cord injury, " said Bunge, who declined to speculate when human trials

might be attempted.

The spinal cord carries messages between the brain and the muscles

through a network of nerve cells. Normally, chemical signals prevent

those nerves from regrowing, resulting in paralysis when the network

is severed by an injury.

Regrowing nerve cells and reconnecting them is the holy grail of

spinal cord research.

The Miami study involved hundreds of animals with crushing injuries

to the thoracic region of the spinal cord, which mainly causes loss

of control of the legs and is the most common form of injury among

the 243,000 people in the United States living with spinal cord

injuries, the researchers said.

They transplanted cells known as Schwann cells from the peripheral

nerves, where regeneration does occur, to create a bridge across the

damaged area of the spinal cord and promote the growth of axons, the

nerve fibers that transmit messages. Those cells also make the

protective myelin sheath that insulates nerve fibers.

Growth stopped too soon

In earlier research, such grafts did promote the growth of new nerve

fibers across and through the damaged areas of the spinal cord, but

they stopped growing too soon.

So researchers combined the grafts with two other treatments --

injections of cyclic AMP, a messenger molecule that guides the nerve

cells to grow their connecting fibers, and Rolipram, which prevents

the breakdown of cyclic AMP.

" The cyclic AMP hangs around longer and can be more effective, " Bunge

said in an interview on Friday.

Rolipram was developed as an antidepressant by Germany's Schering AG

and is also being investigated as a possible treatment for multiple

sclerosis.

After eight weeks, the rats that did not receive the treatment could

occasionally take a halting step but could not take one step after

another, Bunge said.

Those that received the treatment had regained 70 percent of their

walking function, " a striking improvement, " Bunge said. They could

step consistently, and had better fine motor control and coordination.

" The hind limbs knew what the fore limbs were doing, " said Bunge, who

designed the study with her colleague, Dr. Damien Pearse.

The triple-treated animals also had more tissue in their spinal cords

than those without the treatment, suggesting it had stopped the

secondary tissue loss that normally occurs after a spinal cord

injury, Bunge said. And the triple-treated rats had a 500 percent

increase in nerve fibers in the graft area, she said.

" Each of the pieces of the (Miami) strategy have been hailed

as 'promising' in earlier reports, but the behavioral effects were

not huge. With the right combination, the sum is now proving to be

much greater than the parts, " said Dr. Naomi Kleitman, a program

director for spinal cord injury research the National Institute of

Neurological Disorders and Stroke, a component of the National

Institutes of Health.

Copyright 2004 Reuters