Repairing damaged or severed nerves could transform the lives of countless people with untreatable partial or complete paralysis. The ultimate dream is that science might one day allow them to walk again. In the journal Acta Biomaterialia, researchers in South Korea report progress in accelerating nerve regeneration using a glue-like protein extracted from mussels.
While their work initially targets peripheral nerve injuries, such as those controlling the sensation and movement of just one limb, it may ultimately assist progress toward repairing more profound damage, such as severed spinal cords.
The researchers combine molecules of the mussel adhesive protein (MAP) with cell-supporting protein fragments called peptides from the extracellular matrix (ECM) and which are found naturally outside of cells. These functional biomaterials are combined and incorporated into aligned nanofibers using the polymer poly(lactic-co-glycolic acid). This creates a composite pipework – the researchers call it a “conduit” - which encourages nerve cells to regenerate in a selected direction.
Nerve guidance conduits up to 15 millimetres long and 1.5 millimetres wide were created using an electrospinning technique. This uses an electric field to draw a fluid of electrically charged material through a fine nozzle, prior to it condensing into solid nanofibers.
Tests with cultured cells demonstrated that the conduits could encourage and direct the growth of nerve tissue along the direction determined by the fibers. They achieve this by helping the precursor cells involved in a repair to adhere to one another, multiply, and develop into functional nerve cells with sprouting branches.
To assess the system’s effectiveness in live animals, it was grafted into rats with severed sciatic nerves. After an eight week recovery period, the treated animals regained the function of their affected limbs up to a level equivalent to 95% of normal activity. Untreated animals regained only around 50% of their normal function. These statistics were obtained in a standardised test that assesses both the sensory and movement capabilities of the affected nerves.
“The success of this research can serve as an example for other work,” says research team member Hyung Joon Cha of Pohang University of Science and Technology in South Korea.
Cha reports that the team also hope to develop another application of the mussel adhesive protein by using it as a biocompatible and biodegradable sealant to replace the sutures that are currently used in attempts to treat peripheral nerve injuries. He explains that the sutures currently used can themselves cause secondary nerve injuries, which the mussel protein based sealant might avoid.
“Our goal is to build a total solution for treating peripheral nerve injuries so that the chances of regaining nerve function can be substantially increased,” says Cha.
How the mussle adhesive protein (MAP) and peptides from the extracellular matrix (ECM) are combined into nerve healing fibers.Article details:
Cha, H. J. et al.: “Multi-dimensional bioinspired tactics using an engineered mussel protein glue-based nanofiber conduit for accelerated functional nerve regeneration” Acta Biomaterialia (2019)”
Hyung Joon Cha on Twitter: @hjcha2280
Acta Biomaterialia is part of the family of Acta Materialia Inc journals, which also includes Acta Materialia, Scripta Materialia and the newly launched Materialia