The influence of growth factors on neuromuscular junction regeneration

Peripheral motor nerve injury frequently results in significant morbidity even after repair employing micro-surgical techniques. Following such an injury the trophic effect of the motor nerve is lost, leading to degeneration of the neuromuscular junction, muscle atrophy and eventually irreversible muscle fibrosis.;Several neurotrophic growth factors (including insulin-like growth factor-I and fibroblast growth factor-I) have been identified. These have been shown to facilitate regeneration of peripheral nerve in-vivo, however less is known regarding any trophic action at the neuromuscular junction.;In this series of experiments the ability of insulin-like growth factor-I and fibroblast growth factor-I to facilitate neuromuscular junction regeneration in atrophic muscle was studied. The growth factors were delivered to the nerve/muscle interface of a nerve implant either as a bolus dose using a fibrin glue carrier or by continuous infusion with a mini-osmotic pump. The animal model employed was the rat lower limb model. Functional testing of the regenerated neuromuscular junctions was performed by measuring muscle twitch force following nerve implantation.;Both growth factors were shown to facilitate neuromuscular junction regeneration in atrophic muscle equally effectively. Despite histological evidence of neuromuscular junction regeneration, functional testing did not demonstrate any significant difference between growth factor treatment groups and controls.