QS50. Elucidating the Reasons Behind the Success of Spider Silk In Nerve Regeneration

Abstract

Purpose: The successful reconstruction of peripheral nerve injuries remains a major clinical challenge. Nerve guidance conduits are a promising alternative to autologous nerve transplantation and conduits filled with fibrous materials have shown great potential in bridging nerve gaps. The application of spider silk as a filament material for nerve guidance conduits has led to results comparable to nerve autograft. However, the use of spider silk has been phenomenological so far and the reasons for its success are still not identified. The aim of this study is to elucidate the material properties of spider silk leading to its unique medical performance. This knowledge enables a targeted production of synthetic alternatives such as recombinant silk. Methods: In this work, various silk types from golden orb weavers and tarantulas were investigated. In vitro experiments were conducted, and Schwann cells were seeded on the spider silks and monitored by live cell imaging. The extent of proliferation was analyzed by immunofluorescent staining and confocal microscopy. In addition, the silk fibers were inspected with an electron microscope for differences in their morphology and with Raman spectroscopy as well as wide angle X-ray scattering to determine their secondary protein structure and crystallinity. Results: It was found that the adhesion of Schwann cells on spider silk is independent of the size and morphology of fibers. However, the secondary protein structure and specifically the high content of β-sheets in the direction of silk’s axis gives the fiber its ability to act as a guiding element for Schwann cells. In addition, the results show that the crystallinity of the silk does not affect the proliferation of Schwann cells, while the directed movement of cells is affected by this material property. Conclusion: This direct comparison demonstrated the crucial role of the secondary protein structures and crystallinity of spider silk for the guidance properties of fibers during nerve regeneration. These results should be considered during the targeted production of synthetic fibrous materials for nerve regeneration.