Interleukin-10 and regeneration in an end-to-side nerve repair model of the rat.

End-to-side (ETS) neurorrhaphy is an option in peripheral nerve surgery. The aim of this study was to investigate whether the application of the anti-inflammatory cytokine interleukin-10 (IL-10) reduces scarring and thus enhances nerve regeneration in an ETS peroneal/tibial nerve lesion model of the rat. Twenty rats with a peroneal to tibial ETS neurorrhaphy were divided into two groups: (1) control group and (2) IL-10 group with intrafascicular application of 0.125 µg/100 µl IL-10. Survival time was 8 weeks. Nerve conduction velocities (NCVs) and motor function were analyzed and histomorphological evaluation with measurement of intraneural collagen level, axon count, total nerve area, and myelination index followed. Evaluation of motor function and nerve conduction did not show any statistical differences. Histological analyses revealed thicker myelin sheaths and higher myelination index in the IL-10 group (p < 0.001). Axon count showed no difference. The IL-10 group revealed lower collagen levels (p < 0.001). Comparison of total nerve area showed no statistical significance. At this dose, IL-10 evaluated at 8 weeks was not significantly different than placebo in functional, NCVs, and most morphological measures. However, there was a significant difference in thicker myelin sheaths and higher myelination index and lower collagen levels. This suggests that future experiments of IL-10 at different doses or longer periods of evaluation would be of interest.