University of Sheffield, Sheffield, United Kingdom

Injuries to the peripheral nervous system (PNS) are extremely common and affect 1 in 1000 individuals every year. Axon regeneration in the PNS is possible, but typically cannot occur over distances of more than 1–2 mm.

Scanning electron microscopy images of the structures fabricated by (left) 2PP and (right) microreplication techniques.
Currently, patients with severe traumatic nerve damage suffer a devastating loss of sensation and/or movement in the affected limb. The traditional course of action, where possible, is to surgically suture or graft the nerve endings together. However, reconstructive surgery often does not result in complete recovery. The use of entubulation devices such as nerve guidance conduits (NGCs) can aid axon regrowth from the proximal cone toward the distal pump. NGCs are designed to provide a favorable microenvironment and physical guidance for nerve regeneration.

A team at the University of Sheffield and Laser Zentrum Hannover (Hann - over, Germany) has developed a new method for making NGCs. The method is based on laser direct writing, which enables the fabrication of complex structures from computer files via the use of CAD/CAM (computer aided design/ manufacturing), and has allowed the research team to manufacture NGCs with designs that are far more advanced than previously possible.

“When nerves in the arms or legs are injured they have the ability to regrow, unlike in the spinal cord; however, they need assistance to do this,” said John Haycock, professor of bioengineering at University of Sheffield. “We are designing scaffold implants that can bridge an injury site and provide a range of physical and chemical cues for stimulating this regrowth.”

The new conduit is made from a biodegradable synthetic polymer material based on polylactic acid and has been designed to guide damaged nerves to regrow through a number of small channels.

“Nerves aren't just like one long cable, they're made up of lots of small cables, similar to how an electrical wire is constructed,” said lead author Dr Frederik Claeyssens, of the University's Department of Materials Science and Engineering. “Using our new technique, we can make a conduit with individual strands so the nerve fibers can form a similar structure to an undamaged nerve.”

Once the nerve is fully regrown, the conduit biodegrades naturally. The team hopes that this approach will significantly increase recovery for a wide range of peripheral nerve injuries.

In laboratory experiments, nerve cells added to the polymer conduit grew naturally within its channelled structure. The research team is now working toward clinical trials.

“If successful, we anticipate these scaffolds will not just be applicable to peripheral nerve injury, but could also be developed for other types of nerve damage too. The technique of laser direct writing may ultimately allow production of scaffolds that could help in the treatment of spinal cord injury,” said Dr Claeyssens. “What's exciting about this work is that not only have we designed a new method for making nerve guide scaffolds which support nerve growth, we've also developed a method of easily reproducing them through micromolding.”