Fixing Paralysis: Growing New Nerves With 3-D Printed Scaffolds

A scaffold implanted into a mouse Credit: Michael McAlpine, University of Minnesota

The human body is bad at repairing injury, and nerve damage is usually permanent, resulting in paralysis or pain. Nerves can sometimes grow back, but it's an extremely slow process. 3-D printing could change that. 

3-D printing technology is making leaps and bounds in the biological sciences, particularly in fields like tissue regeneration. Scaffolds provide a great environment to direct stem cell activity or aid the body's own restorative mechanisms. Building on this technology, researchers have now created customisable scaffolds that can help regrow nerves. 

Credit: Michael McAlpine, University of Minnesota

Guiding nerve regrowth

Previous efforts have focused on nerve transplants, in an effort to repair nerve damage in victims suffering from pain or paralysis. This process involves taking nerves from a 'healthy' area and grafting them into another. This has had limited success, but there have been issues with pain and rejection. Getting the new nerves to grow in the right direction has also proved challenging. 

Straight cylinders have been tried before to help guide regrowth, but their simple design limits their use to simpler injuries; in complex damage a more complex guidance structure is required. Scientists at the University of Minnesota attempted to overcome this problem by using 3-D printing, which creates detailed structures that can be tailored to an individual patient's needs. After scanning a nerve injury in rats, researchers created specific, branched silicone scaffolds in response and coated them with specific chemicals to trigger nerve growth.

These can be scanned and built in an hour

Rats that had these scaffolds implanted showed significant improvements in movement. The technology isn't perfected yet,  but it holds great promise. Details like specific chemical gradients and which material the scaffold is made of need more work. The scaffolds need to withstand physical strain and eventually dissolve harmlessly after they've done their job.

"One important thing is that now we are printing silicone guides, which are biocompatible but not biodegradable. For human studies, we would like to develop biodegradable scaffolds so that an additional surgery is not required to remove the guide at the end, but it simply dissolves" 

Here's a short video of the process below. The coloured dots represent chemical cues which encourage nerve growth: 

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