Development of a mouse nerve-transfer model for brachial plexus injury

Nerve transfer involves the use of a portion of a healthy nerve to repair an injured nerve, and the process has been used to alleviate traumatic brachial plexus injuries in humans. Study of the neural mechanisms that occur during nerve transfer, however, requires the establishment of reliable experimental models. In this study, we developed an ulnar-musculocutaneous nerve-transfer model wherein the biceps muscle of a mouse was re-innervated using a donor ulnar nerve. Similar muscle action potentials were detected in both the end-to-end suture of the transected nerve (correctrepair) group and the ulnar-musculocutaneous nerve-transfer group. Also, re-innervated acetylcholine receptor (AChR) clusters and muscle spindles were observed in both procedures. There were fewer re-innervated AChR clusters in the nerve transfer group than in the correct repair group at 4 weeks, but the numbers were equal at 24 weeks following surgery. Thus, our ulnar-musculocutaneous nerve-transfer model allowed physiological and morphological evaluation for re-innervation process in mice and revealed the delay of this process during nerve transfer procedure. This model will provide great opportunities to study regeneration, re-innervation, and functional recovery induced via nerve transfer procedures.