Chitosan conduits combined with nerve growth factor microspheres repair facial nerve defects

Research Highlights (1) Microspheres for sustained release of nerve growth factor were prepared by compound method, and the sustained in vitro release of active nerve growth factor lasted for at least 90 days. (2) Microspheres were implanted into chitosan conduits to repair 10-mm defects on the buccal branches of the facial nerve in rabbits. Results showed that the muscular atrophy induced by facial nerve defects was attenuated, and the nerve conduction velocity and amplitude were significantly increased. (3) Microspheres for sustained release of nerve growth factor in combination with chitosan conduits can improve axon and myelin sheath regeneration of injured facial nerve. (4) The combination of nerve growth factor-releasing microspheres and chitosan conduits exhibits superior effects in repairing facial nerve injury compared with nerve growth factor alone. Abstract Microspheres containing nerve growth factor for sustained release were prepared by a compound method, and implanted into chitosan conduits to repair 10-mm defects on the right buccal branches of the facial nerve in rabbits. In addition, chitosan conduits combined with nerve growth factor or normal saline, as well as autologous nerve, were used as controls. At 90 days post-surgery, the muscular atrophy on the right upper lip was more evident in the nerve growth factor and normal saline groups than in the nerve growth factor-microspheres and autologous nerve groups. Electrophysiological analysis revealed that the nerve conduction velocity and amplitude were significantly higher in the nerve growth factor-microspheres and autologous nerve groups than in the nerve growth factor and normal saline groups. Moreover, histological observation illustrated that the diameter, number, alignment and myelin sheath thickness of myelinated nerves derived from rabbits were higher in the nerve growth factor-microspheres and autologous nerve groups than in the nerve growth factor and normal saline groups. These findings indicate that chitosan nerve conduits combined with microspheres for sustained release of nerve growth factor can significantly improve facial nerve defect repair in rabbits.