Novel Injectable Supports Long‐Term Recurrent Laryngeal Nerve and Partial Peripheral Nerve Repair

BACKGROUND: Unilateral vocal fold paralysis (VFP) from recurrent laryngeal nerve (RLN) injury currently has no injectable treatment options that promote targeted reinnervation. In a prior pilot study, Agrin, neuregulin-1 (NRG1), and acetylcholine (ACh) enhanced early (1-month) reinnervation after RLN injury. The aims of the current study were to (1) assess if these effects persist in a 3-month RLN injury model and (2) test whether Agrin/ACh/NRG1 promotes regeneration after sciatic nerve (SN) transection, with relevance to nerve repair beyond the larynx. METHODS: Adult C57BL/6 mice underwent unilateral RLN or SN transection with injections into the thyroarytenoid or gastrocnemius, respectively. Separate RLN and SN cohorts included saline (N = 5), biomolecule (Agrin, NRG1, ACh) (N = 5), and uninjured controls (N = 5). Functional recovery was evaluated using videolaryngoscopy and electromyography (EMG) for RLN injury, and gait analysis with EMG for the SN model. Histologic outcomes included immunohistochemistry and myofiber diameter of the thyroarytenoid or gastrocnemius muscles. RESULTS: Biomolecule treatment improved vocal fold movement and restored EMG symmetry in the RLN model, consistent with functional reinnervation. Histology demonstrated increased NMJ formation and preserved myofiber integrity. In the SN model, treatment did not produce meaningful functional recovery based on EMG and gait deficits. However, gross nerve continuity, increased neurofilament staining, and preserved myofiber architecture indicated partial structural regeneration. CONCLUSIONS: Biomolecule therapy supports functional and structural regeneration following RLN injury and demonstrates structural, but not sustained functional, recovery in the SN model. Further investigation into sustained delivery or repeat dosing may be necessary to support regeneration in larger peripheral nerves. LEVEL OF EVIDENCE: N/A.