Chitosan conduits filled with simvastatin/Pluronic F-127 hydrogel promote peripheral nerve regeneration in rats.

Treating peripheral nerve defects represents a clinical challenge, and nerve conduits lacking an internal scaffold lead to limited large nerve gap regeneration. Here, we bridged 10-mm sciatic nerve defects in rats with a chitosan conduit filled with 0, 0.5, or 1.0 mg of simvastatin in Pluronic F-127 hydrogel. We assessed subsequent nerve regeneration using the sciatic functional index (SFI), electrophysiological assessments, Fluoro-Gold (FG) retrograde tracing, gastrocnemius muscle mass measurements, and histological and immunohistochemical assessments of nerve regeneration. Ten weeks after implantation, the chitosan conduit filled with simvastatin/Pluronic F-127 hydrogel promoted nerve regeneration; there were significant increases in the SFI, compound muscle action potential peak amplitude, motor nerve conduction velocity, FG-labeled neuron number in the dorsal root ganglia, myelin sheath thickness, axon diameter, gastrocnemius wet weight, and muscle fiber area percentage in the gastrocnemius muscle (all p < 0.05). The expression levels of neurotrophic factors, such as pleiotrophin, hepatocyte growth factor, vascular endothelial growth factor, and glial cell line-derived neurotrophic factor, were also found to be increased. The results suggest that chitosan conduits filled with simvastatin/Pluronic F-127 hydrogel improved peripheral nerve regeneration and functional recovery in rats, which may have been related to the increased expression of several endogenous neurotrophic factors.