Silk-in-Silk Nerve Guidance Conduits Enhance Regeneration in a Rat Sciatic Nerve Injury Model

Advanced nerve guidance conduits can provide an off-the-shelf alternative to autografts for the rehabilitation of segmental peripheral nerve injuries. In this study, the excellent processing ability of silk fibroin and the outstanding cell adhesion quality of spider dragline silk are combined to generate a silk-in-silk conduit for nerve repair. Fibroin-based silk conduits (SC) are characterized, and Schwann cells are seeded on the conduits and spider silk. Rat sciatic nerve (10 mm) defects are treated with an autograft (A), an empty SC, or a SC filled with longitudinally aligned spider silk fibers (SSC) for 14 weeks. Functional recovery, axonal re-growth, and re-myelination are assessed. The material characterizations determine a porous nature of the conduit. Schwann cells accept the conduit and spider silk as growth substrate. The in vivo results show a significantly faster functional regeneration of the A and SSC group compared to the SC group. In line with the functional results, the histomorphometrical analysis determines a comparable axon density of the A and SSC groups, which is significantly higher than the SC group. These findings demonstrate that the here introduced silk-in-silk nerve conduit achieves a similar regenerative performance as autografts largely due to the favorable guiding properties of spider dragline silk.