Comparison between normal and reverse orientation of graft in functional and histomorphological outcomes after autologous nerve grafting: An experimental study in the mouse model

Abstract

Background Autologous nerve grafting has been considered the gold standard for the treatment of irreparable nerve gaps. However, the choice of effective proximodistal orientation of autografts (normal or reversed) is controversial. Therefore, we compared functional and histological outcomes between normal and reversed orientations of autografts in a mouse sciatic nerve model. Materials and methods Thirty C57BL/6J mice weighing 20–25 g were assigned to the donor, normally oriented autograft, and reverse‐oriented autograft groups (n = 10 per group). A 10‐mm section of the sciatic nerve was harvested from a donor mouse. Half the harvested nerve was grafted onto an irreparable gap in a recipient mouse using either a normal or reversed orientation. The sciatic functional index (SFI) was measured biweekly for up to 12 weeks postoperatively. Morphological analysis was performed using immunofluorescence staining for neurofilament (NF) and myelin protein zero (P0) in cross‐sectional and whole‐mount nerve preparations in 12 weeks postoperatively. Additionally, morphological analysis of the tibialis anterior muscle was performed using hematoxylin and eosin staining. NF or P0‐expressing axons were counted and cross‐sectional area (CSA) and minimum Feret's diameter of myofibers were measured. Results The SFI recovered gradually up to 12 weeks after autografting, but there were no significant differences in the SFI between the normal and reversed orientations. The number of NF‐expressing axons in center of graft was significantly higher in the normal orientation than in the reversed orientation (P < .05). However, there were no significant differences in the number and mean intensity of P0‐expressing axons between the orientations. The CSA of myofibers was significantly larger in the normal orientation than in the reversed orientation (P < .05). Conclusions Normally oriented autografts promote axonal regrowth and prevent neurogenic muscular atrophy compared with reverse‐oriented autografts. However, despite these positive histomorphometric effects, the proximodistal orientation of the autograft does not affect functional outcomes.

Comments on “Comparison between normal and reverse orientation of graft in functional and histomorphological outcomes after autologous nerve grafting: An experimental study in the mouse model”

“…Despite being considered the clinical gold standard for segmental defect reconstruction, the orientation of the donor nerve autograft remains widely debated. The article "Comparison between normal and reverse orientation of graft in functional and histomorphological outcomes after autologous nerve grafting: An experimental study in the mouse model" details an extensive investigation of the effect of autograft orientation on peripheral nerve repair in mice (Lee et al, 2021). Histological and behavioral outcome measures are provided that suggest normal oriented autografts enable greater regeneration and diminished muscle atrophy compared to reverse autografts, and there is no benefit to motor function dependent on autograft orientation.…”

“…Lee et al compared the effect of autograft orientation on nerve regeneration in mice by repairing a 3 mm defect was repaired using a 5 mm autograft either in normal or reversed orientation (Lee et al, 2021). Mice are commonly utilized model for high-throughput preclinical testing of novel therapeutics and/or studying mechanism of action(s) following nerve injury.…”