As a treatment for paralysis in mice, a self-assembling gel has been shown to stimulate nerve regeneration.
A section of the spine from a mouse that has been treated with the gel shows nerve fibers in red Samuel I. Stuppling.
After four weeks, paralysed mice were able to walk again thanks to a self-assembling gel that was injected at the site for spinal cord injuries.
The gel mimics cells' natural matrix, providing scaffolding that allows cells to grow. It can also stimulate nerve regeneration by sending signals.
Samuel Stupp, a Northwestern University student, and his collaborators created a material that is made up protein units called monomers. These long chains of protein units are called supramolecular fibrils.
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These fibrils formed a gel when they were injected into spinal cords of paralysed mice in their hind legs.
Researchers injected paralysed mice with fibrils or a salt solution sham treatment, one day after their initial injury. The gel allowed paralysed mice walk four weeks after being injected, while mice who received placebo couldn't walk again.
The gel was found to help regenerate the damaged ends of neurons. It also reduced scar tissue around the injury site which can often act as a barrier to the process of regeneration. The gel also increased blood vessel growth, which gave more nutrients to the spinal chord cells.
"The therapy is superior to all other methods because of the extent of functional recovery and the solid biological evidence of repair that we observed with a model that accurately mimics severe human injuries," states Stupp.
Stupp says that other treatments may use stem cells, genes, or proteins, and they are questionable in terms of safety and effectiveness.
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Two ways were used to assess the walking ability of mice. The first was to give the mice an overall score that reflected their ability to walk, including how they moved, where they pawed and how far they walked. The gel-treated mice scored three times higher than the sham-treated ones.
The team also tested their walking ability by coating the hind legs with coloured dyes, and then letting them walk along a narrow runway made of white paper. The gel was found to increase stride width as well as length.
According to Stupp, a longer stride should correspond with a wider stride and more regrown nerve fibres innervating the legs.
The team created short protein sequences onto the ends monomers to enhance the gel's regenerative properties. These sequences transmit regenerative signals to the spinal cord cells' receptors.
The team altered the non-signal portion of these monomers and found that increasing the mobility of molecules in the larger fibril structure resulted in mice being able to recover. This is likely because increased motion allowed signals to interact with more cells.
Ann Rajnicek, University of Aberdeen, UK, says, "It would certainly be exciting if this discovery could translate to humans. However, issues of scaling mouse therapies for humans are not trivial."
Journal reference: Science,, DOI: 10.1126/science.abh3602
