Immediate and delayed nerve repair: improved muscle mass and function with leukemia inhibitory factor.

In this study we examined the effect of leukemia inhibitory factor (LIF) on delayed repair of injured nerves. In a standard entubulation gap repair model of sciatic nerve in the rat, repair was performed immediately and after delays of 1 day, 1 week, and 4 weeks. Repaired nerves were treated with either LIF (10 ng) or saline, and assessment was by muscle mass and force contraction at 12 weeks after repair. After immediate nerve repair LIF administration resulted in 2.5- to 3-fold improvements compared with saline. In the 1-day delayed group, both saline and LIF treatment groups were comparable with that achieved with immediate repair combined with LIF. This result is consistent with the concept of preconditioning. In the 1-week delayed repair groups with LIF, muscle mass recovery and maximum force contraction were improved by 32% and 55%, respectively, compared with saline, whereas repairs delayed for 4 weeks showed increases of 50% and 36%. All delayed repairs treated with LIF were more effective than immediate repair with saline, but not as effective as primary repair with LIF. Our findings support the view that factors such as LIF may be efficacious for improving recovery of function in cases of delayed peripheral nerve repair.