Human Gingival-Derived NCSCs Enhance Functional Recovery Following Nerve Fusion

Objectives: Facial nerve injury resulting in a disconnection between the neurons and the muscle end target often leads to incomplete functional recovery and disfiguring paralysis. Successful functional recovery requires axonal regeneration to span the entire disconnected stump and reconnect with the denervated muscle. However, diminished neuronal regenerative capacity coupled with prolonged muscle denervation diminishes the likelihood of successful reinnervation. To date, no clinically available strategies address these issues. Nerve fusion is a promising approach to immediately restores axonal connectivity with denervated muscle. However, fusion efficacy and recovery may be enhanced by stabilizing weakly fused axons and promoting regeneration. In this study, we evaluated whether pro-regenerative and immunomodulatory exosomes secreted by neural crest cells (NCSC) induced from human gingiva-derived mesenchymal stem cells (GMSC) augment regenerative capacity and improve functional recovery after facial nerve injury.
Methods: Exosomes (Exo) secreted by GMSC or NCSC were encapsulated in fibrin glue (40 µg). Male rats were randomly enrolled in the facial nerve injury model. Following epineural suture repair and the well-established fusion protocol, 20 µL fibrin was applied to the coaptation site containing one of the following: (A) Fusion, (B) Fusion+Fibrin, (C) Fusion+GMSC-Exo:Fibrin, (D) Fusion+NCSC-Exo:Fibrin. Immediate electrophysiological recovery, and nerve regeneration, muscle reinnervation, longitudinal electrophysiological and facial palsy recovery, and distal nerve molecular changes were evaluated at 6 and 12 weeks post repair.
Results: Fusion resulted in immediate electrical connectivity after repair. Histological and functional recovery outcomes suggest potential nerve regeneration and maturation in the Fusion+NCSC-Exo:Fibrin cohort.
Conclusions: In vivo findings demonstrate fusogens are promising approach for immediate nerve reconstruction; however, additional work to improve efficacy is necessary prior to widespread clinical adoption, e.g. large animal efficacy testing. Further mechanistic work is necessary to elucidate the role exosomes secreted by human gingiva-derived NCSCs have on enhancing facial nerve fusion.