Nerve regeneration is improved by insulin-like growth factor I (IGF-I) and basic flbroblast growth factor (bFGF)

Abstract

In rat sciatic nerves, IGF-I or bFGF was applied distal to a crush to evaluate their effects upon the restoration of the neuromuscular function. In comparison with the recovery following a simple crush, treatment with growth factors resulted in (i) enhanced elongation of regenerating axons ( + 24%) up to day 3 post lesion (PL); (ii) more sprouts at early times; (iii) reduced participation of macrophages in the removal of the degenerating myelin in the first week PL; (iv) restoration of the neuromuscular transmission 2 days earlier; (v) a prolonged relaxation time and a reduced specific tetanic tension at week 3 PL but not at week 7 PL. Other indicators of recovery such as conduction velocity of nerve impulse, muscle weight, specific twitch tension, and time to peak were not affected by bFGF or IGF-I. Results suggest that IGF-I and bFGF affect locally Schwann cells and axons, and also the neuron as a whole, including its trophic function. We conclude that IGF-I and bFGF applied to the nerve, albeit moderately, improve the recovery of the neuromuscular function.