Acceleration of peripheral nerve regeneration following FK506 administration.

Purpose: The severe functional and sensory deficits seen following injury to peripheral nerves makes facilitation of nerve regeneration a primary goal of the reconstructive surgeon. This study examines whether daily administration of FK506 or Cyclosporin A expedites peripheral nerve regeneration following neurotmetic injury in a rat model Methods: Inbred Buffalo rats were randomized to three experimental groups. Group I rats served as untreated controls. Rats in groups II and III received daily subcutaneous CsA (5 mg/kg), and FK506 (1 mg/kg), respectively. Each animal underwent unilateral posterior tibial nerve transection with immediate epineurial reapproximation. Functional recovery of the injured limb was assessed by serial walking track analysis. Nerve regeneration was assessed histomorphometrically via light microscopy. Results: Return of hindlimb function in control animals occurred at 32 days post injury. CsA and FK506-treated transection animals recovered at 26 and 18 days post injury, respectively. Statistically significant greater fiber density and percent neural tissue were seen in FK506- treated animals compared to control animals four weeks post transection. Conclusions: This data suggest that the daily systemic administration of both CsA and FK506 accelerate the rate of functional regeneration, following neurotmetic injuries in tbc rat model. FK506's effect on nerve growth is significantly greater than that of CsA.