By injecting a special gel into the spinal cord of paralyzed mice, they were able to walk again within four weeks. The gel stimulates the repair of damaged nerve cells.
Researchers injected 76 paralyzed mice with either the active gel or a sham treatment one day after injury. They found that the gel enabled the paralyzed mice to walk again within four weeks. In contrast, the mice in the control group remained paralyzed.
The research team showed that the gel allowed the damaged ends of the nerve cells to grow back. In addition, the gel reduced the amount of scar tissue, which normally slows down the regeneration process. The gel also stimulated blood vessel growth, bringing more nutrients to the nerve cells.
Long chains
Materials Chemist Samuel Stupp from Northwestern University in Chicago and his colleagues made a material from short protein pieces called monomers. When you place them in water, these molecules organize themselves into long chains. Once these chains are injected into the spinal cord of the paralyzed mice, they form a gel here. This gel mimics the structure that normally surrounds cells and thus supports cell growth.
‘We saw clear biological indications of recovery, in an animal model that mimics human injuries very well. That makes this treatment better than other approaches,” says Stupp. Other experimental treatments for paralysis often use stem cells, genes or proteins. Stupp points out that there are doubts about whether these treatments are safe and effective.
Walk in line
The team examined the mice’s walking ability in two ways. First, the mice were given an overall score, for which the researchers assessed their ankle movements, body stability, paw placement and steps. The score of the gel-treated mice was three times higher than that of the mice in the control group.
The mice then underwent another test. Their hind legs were dipped in colored paint, which they had to walk on a narrow track on which lay a white sheet of paper. This test showed that the gel increased both the width and length of the steps. “This would be related to more regenerated nerve pathways supplying the leg muscles with nerves,” Stupp said.
Signal
The restorative effect of the gel is due to a short row of amino acids, the building blocks of DNA, which are attached to the ends of the proteins in the monomers. These pieces give off a recovery signal that is picked up by receptors on the outside of the nerve cells.
“It would be very interesting if this finding could be translated to people, even though it has been shown that this is often not without problems,” says medical scientist Ann Rajnicek from the University of Aberdeen.