A “self-assembling” gel injected at the site of spinal cord injuries in paralyzed mice has enabled them to walk again after only four weeks.
The gel mimics the matrix normally found around cells, providing scaffolding of sorts that helps cells grow. It also provides signals that stimulate nerve regeneration.
Led by Samuel Stupp, researchers at Northwestern University in Chicago, created a material made of protein units, called monomers, that self-assemble into long chains, called supramolecular fibrils, in water.
When injected into the spinal cords of paralyzed mice in the hind legs, these fibrils formed a gel at the injury site.
The researchers injected 76 paralyzed mice with either the fibrils or a counterfeit treatment made of salt solution, only one day after the initial injury.
By four weeks out, the paralyzed mice could walk.
The mice given the placebo weren’t as lucky and never regained the ability to walk.
Samuel Stupp’s team found that the gel helped regenerate the severed ends of neurons and reduced the amount of scar tissue at the injury site, which usually forms a barrier to regeneration. What’s more is that the gel also enhanced blood vessel growth, which provided more nutrients to the spinal cord cells.
“The extent of functional recovery and solid biological evidence of repair we observed using a model that truly emulates the severe human injury makes the therapy superior to other approaches,” says Stupp. He went on to say that other experimental treatments being developed for paralysis use stem cells, genes, or proteins and have questionable safety and effectiveness.
The mice’s ability to walk was evaluated in two ways. First, the mice were given an overall score to represent their ankle movement, body stability, paw placement, and steps.
Mice treated with the gel had a score three times higher than placebo-treated mice.
Secondly, the team assessed the mice by dipping the hind legs of the mice in colored dyes and letting them walk across a narrow runway lined with white paper. This test showed that the gel increased both stride width and length.
Stupp explains, “A higher stride length and width should correlate with more regrown axons [nerve fibers] innervating the muscles of the leg.”
The gel’s regenerative effect works due to short sequences of amino acids attached to the ends of the monomer proteins. The sequences provide regenerative signals, which are picked up by receptors on the surface of spinal cord cells.
By altering the non-signal part of these monomers, the team found that enhancing the ability of the molecules to shift in and out of the larger fibril structure reinforced the recovery of mice, probably because the increased motion activated the signals to engage with more receptors on the cells.
“It would be very exciting if this finding could translate to humans, though issues of scaling mouse therapies to humans are not trivial,” says Ann Rajnicek at the University of Aberdeen, UK.
Science and medical advances have broken through so many barriers in the last few decades. Scientific and medical research looks more like a hockey stick than a gradual growth! There’s no telling how fast things will progress. Even if this doesn’t end up working, it’s only a matter of time until we see this miracle.
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