Introduction: We sought to determine whether supplementation of acellular nerve allografts (ANAs) with Schwann cells overexpressing GDNF (G-SCs) would enhance functional recovery after peripheral nerve injury. Methods: SCs expanded in vitro were infected with a lentiviral vector to induce GDNF overexpression. Wild-type SCs (WT-SCs) and G-SCs were seeded into ANAs used to repair a 14-mm nerve gap defect. Animals were harvested after 6 and 12 weeks for histo- morphometric and muscle force analysis. Results: At 6 weeks, histomorphometry revealed that ANAs supplemented with G- SCs promoted similar regeneration compared with isograft at midgraft. However, G-SCs failed to promote regeneration into the distal stump. At 12 weeks, ANAs with G-SCs had lower maximum and specific force production compared with controls. Conclusions: The combined results suggest that consistent overexpression of GDNF by G-SCs trapped axons in the graft and prevented functional regeneration. Muscle Nerve 47:213-223, 2012 The current ''gold standard'' for peripheral nerve repairs is a direct end-to-end coaptation. However, this is not always possible due to tension on the repair that would ultimately impair nerve regenera- tion. 1 In these instances, it may be necessary to use
