Effectiveness of filling structures within nerve guidance conduits in a rat sciatic nerve injury model.

Introduction: The gold standard treatment for peripheral nerve gap injury is nerve autograft transplantation. Although various nerve guidance conduits (NGCs) have been developed as alternatives to autografting, few reports have evaluated the effects of the internal structure of NGCs on nerve regeneration. We investigated how the internal structure of NGCs affects nerve regeneration. Methods: In 30 male Wistar rats, a 5 mm segment of the left sciatic nerve was resected, creating a gap. The animals were then randomly divided into two groups. A 7 mm polyglycolic acid (PGA) conduit, with (PGA-c group) or without a collagen filling (PGA group), was used to bridge the gap (n = 15 for each group). At 2 and 4 weeks postoperatively, longitudinal sciatic nerve slices were fluorescently immunostained with RECA-1 for endothelial cells, S100 for Schwann cells, and TUJ1 for axons. The fluorescence-positive areas were quantitatively evaluated. Next, 32 male Wistar rats underwent resection of a 10 mm segment of the left sciatic nerve. The animals were then assigned into four groups: sham group, autograft group, PGA-c group (transplantation of 12-mm PGA-c), and hollow PGA group (transplantation of 12 mm hollow PGA) (n = 8 for each group). At 12 weeks postoperatively, morphological evaluations and neurofunctional analyses were performed. Results: In longitudinal sciatic nerve slices, the PGA-c group had significantly larger RECA-1-positive areas proximally and distally at 2 weeks, larger S100-positive areas proximally at 2 weeks, and larger TUJ1-positive areas proximally at 4 weeks postoperatively than the PGA group. In the 10 mm nerve defect model, the PGA-c group had a significantly higher percentage of myelinated axons, isometric tetanic force, and tibialis anterior muscle wet weight than the PGA group. Conclusions: The internal filling structure of the NGCs may promote nerve regeneration by providing a scaffold for cells involved in nerve regeneration and may restore motor function. These findings provide new insights into the further structural development of NGCs suitable for peripheral nerve regeneration.