A cross-section image of the nerve conduit embedded in microspheres. Credit: N.B. Fadia et al., Science Translational Medicine (2019)

Researchers at the University of Pittsburgh School of Medicine have created a polymer nerve guide made out of biodegradable material filled with growth-promoting proteins that can regenerate long sections of damaged nerves. Published in Science Translational Medicine, the team were able to bridge a large, 2-inch gap between a nerve and its target muscle with this new guide, without needing a donor nerve or stem cells, and proved to be just as good, or if not better, than a nerve graft. 

Discovering ways to regrow nerves will be lifechanging for those suffering with nerve damage, such as soldiers who sustain injuries in areas that aren’t well protected by body armour like the arms and legs. Other instances can occur from cancer treatments, car crashes, machinery accidents, diabetes, and birth trauma, which currently affects more than 20 million Americans.

When a damaged nerve section is longer than a third of an inch, peripheral nerves fail grow far enough to find its target and often result in a neuroma: a painful ball of nerves resulting from nerve tangles. Restoring nerve function in longer sections of nerve damage usually involves removing a sensory neuron from the back of the leg, then cutting, bundling, and sewing it onto the end of the damaged motor nerve usually in the arm. Some complications can arise from this, such as numbness in the leg and a chance that not all motor function will return.

The new nerve guide is made from dissolvable sutures with a growth-promoting protein, which releases the protein slowly over the course of months.

The researchers investigated their design in monkeys with a 2-inch nerve gap in the forearm and found that 80% of fine motor control was returned to the thumbs of four monkeys over a year. Two controls, an empty polymer tube and a nerve graft, were used and the new guide design proved to be just as good as the nerve graft, even excelling in restoring nerve conduction and replenishing Schwann cells.

The researchers want to bring the new nerve guide to human patients and are working with the Food and Drug Administration (FDA) to begin a new clinical trial.