Effects of IGF-II in a new end-to-side model.

Insulin-like growth factor-II (IGF-II) has been shown to increase the rate of axon regeneration in a number of models involving the rat sciatic nerve. This project studied the effects of IGF-II on an end-to-side nerve repair. In this study, the musculocutaneous nerve of a Sprague-Dawley rat was transected and coapted by end-to-side neurorrhaphy to the median nerve. Experimental animals received a local infusion of IGF-II at the repair site, while control animals received a local infusion of placebo solution. This new model allowed for the assessment of functional outcome through the Terzis grooming test. The use of an end-to-side repair minimized potential damage to the motor nerve donor (median nerve) and encouraged lateral axon sprouting into the severed nerve (musculocutaneous nerve). Histologic results showed that the IGF-II treated group had higher axon counts and greater myelin thickness in the reinnervated musculocutaneous nerve. IGF-II-treated animals also had significantly greater motor-end-plate counts in the biceps muscle. Furthermore, the IGF-II group scored consistently higher in the grooming test, compared to the control group.