Methods: Regeneration of the sciatic nerve was assessed in four groups of C57-black-6 mice (8 animals/group). Under general anaesthesia (Fentanyl/Fluanisone 0.8ml/kg & Midazolam 4mg/kg, i.p.) the nerve was sectioned and repaired using 4 epineurial sutures. IL-10 (125ng or 500ng in 100μl of diluent) or phosphate buffered saline was injected into and around the proximal and distal nerve stumps, and comparisons made with sham-operated controls. After 6 weeks the outcome was assessed blind by determining; (1) the percentage area of picrosirius red staining (PAS) for collagen at the repair site (2) the ratio of the compound action potential (CAP) modulus evoked by electrical stimulation 2mm distal or proximal to the repair (3) the number of myelinated axons at the same sites.
Results: The median PAS for collagen was 1.73% in the controls, was higher in the saline (5.35%) and 500ng IL-10 (7.22%) repair groups (p<0.04, Kruskal-Wallis test), but not significantly different from the 125ng IL-10 group (3.35%, p=0.19). The median CAP ratio was 0.92 in the controls, was lower in the saline (0.34) and 500ng IL-10 (0.34) groups (p<0.04), but not significantly different from the 125ng IL-10 group (0.77, p=0.12). The myelinated fibre counts were always higher distal to the repair site, but there were no significant differences between groups.
Conclusion: Administration of a low dose of IL-10 to a site of sciatic nerve repair reduces scar formation and permits better regeneration of the damaged axons.
Supported by the Wellcome Trust (074500).