Growth factor may decrease muscle atrophy secondary to denervation

Despite modern microsurgical techniques, functional outcomes following brac hial-plexus reconstruction and peripheral-nerve repair are usually unsatisf actory, because irreversible muscle atrophy develops before reinnervation o ccurs. Insulin growth factor-1 (IGF-1) has been shown to improve muscle reg eneration after injury, and may have a role in muscle preservation followin g denervation. This study evaluated the histologic, immunohistochemical, an d electrophysiologic differences between normal and denervated muscle over an 8-week time period, and also evaluated the effects of injecting IGF-1 in to denervated muscle. Denervated mice gastrocnemius muscles demonstrated a decrease in muscle diameter, a decrease in muscle weight, early nuclear pro liferation, and a decrease in fast twitch and maximum tetanic strength, com pared to normal gastrocnemius muscle up to 8 weeks following denervation. F our weeks after denervated muscle was injected with IGF-1 at time zero, how ever, relative preservation of muscle diameter and weight, and maintenance of electrophysiologic contractile properties were observed. These prelimina ry data suggest that IGF-1 may prevent muscle atrophy secondary to denervat ion.