Delayed repair of transected nerves: Effect of brain-derived neurotrophic factor

Objective: To determine if administration of brain-derived neurotrophic factor (BDNF) after peripheral nerve transection can improve the functional outcome in situations where epineurial repair must be delayed. Design: Randomized, blinded, controlled trial. Subjects: Thirty-four Sprague-Dawley rats. Intervention: Sciatic nerves were transected and, after a 2-week delay, repaired with epineurial sutures. Animals were assigned to receive daily administration of lactated Ringer solution (LR [control] group); BDNF delivered at the time of nerve transection through 2 weeks after nerve repair, for a total of 4 weeks (BDNF-early group); or BDNF delivered at the time of nerve repair through 2 weeks after repair (BDNF-late group). Outcome was assessed using sciatic functional indices (SFIs) and histomorphometric analysis. Results: The SFI maximal recovery was superior in the BDNF groups, but this difference did not reach statistical significance (SFI, -90.1 ± 9.6 [LR group], -85.7 ± 7.6 [BDNF-early group], and-84.6 ± 4.8 [BDNF-late group], where normal function is 0 and complete loss of function is -100; P = .27). The mean axon diameter tended to be greater in the BDNF groups compared with the LR group, ie, 2.43 ± 0.23 μm (LR group), 2.80 ± 0.44 μm (BDNF- early group), and 2.83 ± 0.38 μm (BDNF-late group) (P = .05). Conclusions: The local administration of BDNF to nerves that underwent transection and then repair after a delay resulted in an increase in axonal diameters and maximal SFIs, a difference that did not reach statistical significance. The timing of BDNF administration after nerve transection did not affect neuronal regeneration.