Electrical stimulation accelerates nerve regeneration and functional recovery in delayed peripheral nerve injury in rats

The present study aims to investigate the potential of brief electrical stimulation (ES; 3V, 20Hz, 20min) in improving functional recovery in delayed nerve injury repair (DNIR). The sciatic nerve of Sprague Dawley rats was transected, and the repair of nerve injury was delayed for different time durations (2, 4, 12 and 24weeks). Brief depolarizing ES was applied to the proximal nerve stump when the transected nerve stumps were bridged with a hollow nerve conduit (5mm in length) after delayed periods. We found that the diameter and number of regenerated axons, the thickness of myelin sheath, as well as the number of Fluoro-Gold retrograde-labeled motoneurons and sensory neurons were significantly increased by ES, suggesting that brief ES to proximal nerve stumps is capable of promoting nerve regeneration in DNIR with different delayed durations, with the longest duration of 24weeks. In addition, the amplitude of compound muscle action potential (gastrocnemius muscle) and nerve conduction velocity were also enhanced, and gastrocnemius muscle atrophy was partially reversed by brief ES, indicating that brief ES to proximal nerve stump was able to improve functional recovery in DNIR. Furthermore, brief ES was capable of increasing brain-derived neurotrophic factor (BDNF) expression in the spinal cord in DNIR, suggesting that BDNF-mediated neurotrophin signaling might be one of the contributing factors to the beneficial effect of brief ES on DNIR. In conclusion, the present findings indicate the potential of using brief ES as a useful method to improve functional recovery for delayed repair of peripheral nerve lesions.