Synthetic Nerve Conduit Helps Regrow Damaged Nerves

A biodegradable polymer nerve guide filled with a neurotrophic factor can regenerate long sections of damaged nerves, according to a new study.

Developed at the University of Pittsburgh (Pitt; PA, USA), the off-the-shelf biodegradable nerve guide is a tube-shaped acellular conduit with glial cell-derived neurotrophic factor (GDNF) filled microspheres embedded in its walls. GDNF is released from the microspheres slowly, over the course of several months, in order to support and sustain the survival of the severed neurons so that they can regenerate long stretches (over eight mm) of peripheral nerve, without the need for transplanting stem cells or a donor nerve.

To test the conduits, the researchers removed five cm segments of nerve from the forearms of macaque monkeys. The monkeys were then implanted with either the GDNF conduit, an empty polymer tube, or the gold standard, a nerve graft. The animals that received the conduits had increased nerve conduction velocity, greater Schwann cell recruitment, and a similar functional recovery as those treated with an autografts. The empty guide performed significantly worse. The study was published on January 22, 2020, in Science Translational Medicine.

“Injuries to peripheral nerves that result in small gaps can heal after reapproximation; however, large gaps that occur after severe injuries require autograft implantation,” said senior author professor of plastic surgery Kacey Marra, MD, PhD, of the Pitt McGowan Institute for Regenerative Medicine. “We're the first to show a nerve guide without any cells was able to bridge a large, two-inch gap between the nerve stump and its target muscle. Our guide was comparable to, and in some ways better than, a nerve graft.”

The recombinant form of GDNF promotes the survival and differentiation of dopaminergic neurons, and prevents apoptosis of motor neurons induced by axotomy. GDNF also regulates kidney development and spermatogenesis.

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