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.