Scientists have developed a novel therapy that repairs spinal cord injury in mice, enabling them to walk again within weeks of treatment – the new class of material works by signaling to the spinal cord to repair damaged nerves.

A team from Northwestern University has developed a therapy consisting of a complex network of nanofibers that mimic the natural environment of the spinal cord to send signals that repair damaged neurons after paralysis. The paper, published in Science, found that the treatment regrew severed nerve cells, reduced scar tissue, formed new blood vessels, and protected motor neurons.

Samuel I. Stupp, founding director of the Simpson Querrey Institute for BioNanotechnology at Northwestern, says, “Our research aims to find a therapy that can prevent individuals from becoming paralyzed after major trauma or disease. For decades, this has remained a major challenge for scientists because our body’s central nervous system, which includes the brain and spinal cord, does not have any significant capacity to repair itself after injury or after the onset of a degenerative disease. We are going straight to the FDA to start the process of getting this new therapy approved for use in human patients, who currently have very few treatment options.”

Nanotechnology that can heal a damaged spinal cord

The secret behind the breakthrough therapeutic is the unique nature of the nanofibers, based on a new class of materials called ‘supramolecular polymers.’ The material, unlike traditional polymers, has special bonds holding it together that can break apart and recombine with other broken bonds making it highly flexible and changeable. It can also be injected as a liquid, turning into a gel once inside the body. These properties make it a perfect substitute for the extracellular matrix: the support structure for cells in the body, responsible for wound healing and cell to cell communication.

The scientists said one of the challenges in administering wound healing drugs is that the cell receptors needed to enable this action are constantly moving around. Because the special bonds in the polymer wiggle around and vibrate, the finished structure can communicate and move in time with these mobile cellular receptors. In this way, the nanofibers that make up the polymer can communicate with nerve cells to promote healing.

“Receptors in neurons and other cells constantly move around,” Stupp said. “The key innovation in our research, which has never been done before, is to control the collective motion of more than 100,000 molecules within our nanofibers. By making the molecules move, ‘dance’ or even leap temporarily out of these structures, known as supramolecular polymers, they are able to connect more effectively with receptors.”

A new class of therapeutic that signals to nerve cells

When the nanofibers connect to the receptors, they trigger two cascading signals critical to spinal cord healing. One signal prompts the long tails of neurons in the spinal cord, called axons, to regenerate, strengthening the connection between the body and the brain.

The second signal provides neuroprotection after injury – it causes other cell types to increase, promoting the regrowth of lost blood vessels that feed neurons and critical cells for tissue repair. The therapy also induces myelin to rebuild around axons and reduces scarring, which acts as a physical barrier to the spinal cord healing. 

After 12 weeks, the nanofibers degrade into nutrients for the body, where it disappears harmlessly.

While the new therapy could be used in the emergency room to prevent paralysis after significant trauma involving accidents, gunshot wounds, and diseases, Stupp believes that they can apply supramolecular motion to other therapies and targets.

“The central nervous system tissues we have successfully regenerated in the injured spinal cord are similar to those in the brain affected by stroke and neurodegenerative diseases, such as ALS, Parkinson’s disease, and Alzheimer’s disease,” Stupp said. “Beyond that, our fundamental discovery about controlling the motion of molecular assemblies to enhance cell signaling could be applied universally across biomedical targets.”

Source: Northwestern University

Illustration by Mark Seniw, Northwestern University

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