The role of precisely matching fascicles in the quick recovery of nerve function in long peripheral nerve defects

Abstract

Peripheral nerve injury therapy in the clinic remains less than satisfactory. The gold standard of treatment for long peripheral nerve defects is autologous nerve grafts; however, numerous clinical complications are associated with this treatment. As tissue engineering has developed, tissue-engineered nerve grafts (TENGs) have shown potential applications as alternatives to autologous nerve grafts. To verify the important role of the biomimetic pathway of fascicle design in TENGs, we designed an animal model to study the role of the precise matching of fascicles in the effectiveness of nerve function recovery. 24 Sprague-Dawley rats were divided randomly into three groups (eight/group) that corresponded to 100% fascicle matching (100%FM), 50%FM and 0%FM. We selected Sprague-Dawley rat long-gap (15 mm) sciatic nerve defects. In the 6 weeks after surgery, we found that the 100%FM group showed the most effective functional recovery among the three groups. The 100%FM group showed better functional recovery on the basis of the sciatic functional index than the 50%FM and 0%FM groups. According to histological evaluation, the 100%FM group showed more regenerating nerve fibres. Moreover, in terms of the prevention of muscle atrophy, the 100%FM group showed excellent physiological outcomes. The 100%FM as tissue-engineered scaffolds can enhance nerve regeneration and effective functional recovery after the repair of large nerve defects. The results of this study provide a theoretical basis for future TENG designs including biomimetic fascicle pathways for repairing long nerve defects.

Fig. 1

Schematic view of the surgical procedures in each experimental group. (a) 100%FM group; (b) 50%FM group; and (c) 0%FM group. D, distal stump; FM, fascicle matching; P, proximal stump.

Fig. 2

The process of the surgery. (a) Pre-operation. (b) Intra-operation. (c) Post-operation. Three-point star mark the nerve defect points; Four-point star mark the nerve scaffold proximal points; Five-point star mark the nerve scaffold distal points; Six-point star mark the nerve scaffold proximal points rotation 180°; Seven-point star mark the nerve scaffold distal points rotation 180°; Triangle mark the nerve scaffold proximal points rotation 180° and re-implant in distal point; Square mark the nerve scaffold distal points rotation 180° and re-implant in proximal point.

Fig. 3

The sciatic functional index (SFI) values of the three groups at 0, 2, 4 and 6 weeks after operation. n=8 for each group. *P<0.05, **P<0.01. FM, fascicle matching.

Fig. 4

Histological and immunohistochemical analysis of the three groups at 6 weeks after surgery. (a) The longitudinal sections of the distal part after H&E staining. (b) NF-200 antibody immunostaining of longitudinal sections. (c) S-100 Schwann cell marker immunostained longitudinal sections. (d) NF-200 statistical analysis of the three groups. (e) S-100 statistical analysis of the three groups. There were significant increases in the numbers of positively stained neurofilaments and S-100-positive areas for the 100%FM and 0%FM groups. Error bars correspond to the mean±SD (n=6 for each groups). *P<0.05, **P<0.01. Scale bar=50 µm. FM, fascicle matching.

Fig. 5

Transverse sections of the middle part of the regenerated nerve at 6 weeks postoperatively. (a) Toluidine blue staining. (b) Transmission electron micrograph (TEM) images of regeneration axons. (c) The number of myelinated axons in each area (mm²). The 100%FM and 50%FM groups appeared to have more regenerating nerve fibres than the 0%FM group. (d) The diameter of the myelinated axons from TEM evaluation. (e) Thickness of the myelin sheath. (f) G-ratios of the myelinated nerve fibres. Error bars correspond to the mean±SD (n=6). *P<0.05, **P<0.01. Scale bar=50 and 5 µm, respectively. FM, fascicle matching.

Fig. 6

Triceps surae muscle reinnervation. (a) Masson trichrome staining of transverse sections. (b) Cross-sectional area of muscle fibres. (c) Cross-sectional area of collagen fibres. Error bars correspond to the mean±SD (n=6). *P<0.05. Scale bar=200 µm. FM, fascicle matching.