Scientists Marshal Silk Nanofibers to Repair the Optic Nerve

While scientists have developed biomaterials capable of repairing peripheral nerves, central nerves represent a greater challenge. But now, a team of researchers at the University of Leipzig (Germany) and Tufts University (Medford, MA) are attempting to marshal the powers of silk to repair damage caused to the optic nerve.

When the optic nerve is crushed or cut, the retinal ganglion cells (RGCs) that form the optic nerve degenerate. In such cases, glia cells lose their orientation and form scar tissue at the site of the lesion. Eventually the neuroretina is affected, preventing the RGCs from regrowing their axons and causing them to die. To reverse this process, Thomas Claudepierre, a professor in the faculty of medicine at the University of Leipzig, is using an electrospun silk biomaterial to serve as a 3-D nerve guide that can be implanted at the site of the nerve lesion to provide a growth support to aid the glia to reorient themselves and regenerate the traumatized axons.

To date, scientists have been unable to develop artificial nerve-regrowth technologies that can physically align the growth of regenerating nerves, switch neurons to a regenerative state, promote nerve growth and axonal adhesion, eliminate scar-tissue formation, avoid rejection by the body, avoid swelling that could impinge on the nerve, form by-products that are nontoxic or noninflammatory, and be easy to implant. The Leipzig and Tufts researchers chose silk because it is a highly biocompatible material that can be prepared in purified oriented fibers using electrospinning methods and can be biofunctionalized during the spinning process.

In addition to confirming silk's biocompatibility, the team has shown that the fiber promotes RGC survival by enabling the development of growth cones that preferentially follow the silk fibers. "In our study we provide evidence that silk is a highly biocompatible material in regenerative neuroscience, it guides the growth cone and can topically provide surviving molecules that are protected from degradation and can act therefore over a long period of time, compatible with the duration of a regenerative process in the central nervous system," Claudepierre tells Nanowerk.

The scientists work is far from over. In the short term, they hope to demonstrate that the silk-fiber guide can provide orientation clues for glia cells, thereby reducing glia scarring and controlling gliosis. But if they achieve success, their method for repairing the central optic nerve could point the way forward for treating other types of lesions of the central nervous system.