Silk fibroin conduits: a cellular and functional assessment of peripheral nerve repair

Silk fibroin conduits were designed with appropriate porosity for peripheral nerve repair. The aim of this work was to use these conduits to examine cell inflammatory responses and functional recovery in a sciatic nerve defect model. A total of 45 randomized Lewis rats were used to create an 8-mm defect bridged by a silk guide, commercial collagen guide, or an autograft. After 1, 4, and 8 weeks, macrophage recruitment, percentage of newly formed collagen, number of myelinated axons, and gastrocnemius muscle mass were evaluated. Following 8 weeks, ED1+ cells in autograft and silk conduits decreased to <1% and 17% of week 1 values, respectively. Collagen formation revealed no difference for all measured time points, suggesting a similar foreign body response. Myelinated axon counts within the silk guide revealed a greater number of proximal spouts and distal connections than collagen guides. Gastrocnemius weights demonstrated a 27% decrease between silk and autografts after 8 weeks. This study demonstrates that, in addition to tailorable degradation rates, our silk conduits possess a favorable immunogenicity and remyelination capacity for nerve repair.