Transplantation of neural stem cells overexpressing glia-derived neurotrophic factor promotes facial nerve regeneration

Abstract

CONCLUSION: Combining neurotrophic factor support and neural stem cell (NSC) transplantation may improve regeneration of the peripheral nervous system. Objectives. We constructed a biodegradable nerve conduit (NC) filled with NSCs overexpressing glia-derived neurotrophic factor (GDNF), which is known to protect facial motoneurons, and tested the effect of this NC on facial nerve regeneration. MATERIALS AND METHODS: Primary cultured NSCs were transduced with a lentiviral vector encoding enhanced green fluorescent protein (EGFP) and GDNF. GDNF expression was confirmed by Western blotting and ELISA. Sprague Dawley (SD) rats were subjected to right facial nerve transection, and polyglycolic/polyglycolic acid (PLGA) NCs filled with NSCs-GDNF were used to bridge the nerve gap (n=24). In vivo GDNF expression was confirmed by real-time PCR. NCs containing NSCs, transgenic Schwann cells (SCs-GDNF), or empty NCs served as controls (n=24 per group). Facial nerve regeneration was assessed 2-12 weeks after surgery, by electrophysiological testing, immunohistochemical staining, and morphometric analysis of axons. RESULTS: NSCs exhibited sustained and robust GDNF expression in culture and following implantation. Nerve action potential amplitude, axonal area, and axonal number were significantly greater in the NSCs-GDNF group than in the NSCs or empty NC groups. Axonal area and number were also greater in the NSCs-GDNF group than the SCs-GDNF group, although this was not statistically significant. The enhanced regeneration observed in the NSCs-GDNF group was accompanied by increased labeling for S100, NF, and βIII tubulin.