When a nerve in the arm or leg is severed, the brain loses contact with the muscles for many months. A research team from Poznań – comprising scientists from the AMU Centre for Advanced Technologies, led by Dr Jagoda Litowczenko (editor's note), and cooperating centres, has developed a printed structure that allows nerve cells to migrate independently and form new connections.
Peripheral nerve injuries are an everyday occurrence for surgeons and neurologists. A nerve cut during an accident, a serious injury at work or a mistake during surgery is enough for a patient's arm or leg to abruptly stop working – numbness, weakness and sometimes complete paralysis occur. The body can partially regenerate such nerves, but only over short distances. With a larger severance – a few centimetres or more – nature cannot cope, and the recovery of the function is often incomplete, even after many years.
In a new study published in the Biofabrication journal, a team led by Dr Jagoda Litowczenko from the AMU Centre for Advanced Technologies proposes a more "intelligent" solution. The researchers created GrooveNeuroTube – a tube that combines a rigid skeleton, a soft gel similar to living tissue, growth factors and an antibacterial additive. Then, they checked whether nerve cells could migrate through such a tunnel on their own and reach the other end.
The GrooveNeuroTube skeleton is made of polycaprolactone, a bioplastic already used in medical implants. It was 3D-printed as a thin mesh of fibres and rolled into a tube about 1.5 cm long. A hydrogel, a soft, highly hydrated material resembling ultra-fine jelly, was deposited on this scaffold. A blend of two naturally occurring substances in the body was utilised: hyaluronic acid (found in the skin and synovial fluid, among other places) and gelatin derived from collagen.
The researchers added a protein cocktail, supporting nerve growth, known as growth factors, to this gel. These act as chemical guideposts: encouraging nerve cells to grow in a specific direction and produce longer projections (neurites). Additionally, lysozyme, an enzyme with antibacterial properties, was introduced to help protect the implant from infection in the future.
The following step involved placing cells in the tube. The researchers used F11 cells. It is a cell line that mimics sensory neurons from the so-called dorsal ganglia, which are vital in transmitting pain and touch stimuli. They were suspended in a collagen gel and, with the help of a bioprinter, a device that prints with ink composed of cells and gel, were applied to both ends of the tube. It created a model of a severed nerve: two clusters of cells at the ends and a space in the middle that needed to be filled over time.
During the next 60 days, the researchers observed how the cells behaved in this environment. After just four weeks, the cells from both ends had managed to penetrate so far into the tube that they met in the middle. They had travelled about 8 mm from each side. After two months, most of the tunnel's interior was filled with cells that were not only alive but also forming long projections and a network of connections resembling young nerve tissue.
The scientists compared several systems: the tube alone without growth factors, the tube with growth factors, and the tube with growth factors, additionally stimulated by a pulsed electromagnetic field (PEMF). It is a weak, rhythmic magnetic field, something like a magnetic massage applied for four hours a day. It proved that the best results were achieved by combining all three elements. In this group, the cells moved on average almost twice as far as without growth factors, and the longest projections after 60 days reached nearly half a millimetre. The percentage of living cells exceeded 95%.
The study's authors emphasise that it is still too early for clinical applications. The GrooveNeuroTube structure is currently a highly realistic model of a damaged nerve in laboratory conditions. Thanks to it, it is already possible to test various gel compositions, growth factor doses and stimulation patterns in such a printed tunnel. It means faster treatment development and fewer animal experiments.
However, the idea of a tube that connects a scaffold, soft gel, chemical signals and protection against bacteria closely aligns with what surgeons need to repair nerves after serious injuries. In the future, a comparable smart tube could be implanted in a patient in place of a severed nerve. For people who have been in traffic accidents, suffered hand injuries or undergone cancer surgery, this could mean a greater chance of sensation and mobility recovery with fewer procedures.
The study involved scientists from Adam Mickiewicz University, Poznań and the Institute of Molecular Physics of the Polish Academy of Sciences, along with collaborating researchers from Germany, Spain, Switzerland and the Czech Republic. (PAP)
Source: naukawpolsce.pl