D20. Agrin Nanoparticles in a Nanofiber Hydrogel-based Drug Delivery System Improve Neuromuscular Junction Reinnervation following Chronic Denervation

Abstract

PURPOSE: Following peripheral nerve injury, neuromuscular junctions (NMJs) within denervated muscle rapidly destabilize. Agrin, a proteoglycan essential to NMJ formation, may have an essential role in preserving NMJ receptivity to reinnervation. This study aimed to evaluate the efficacy of agrin-NP therapy in a rodent chronic denervation model. METHODS: Agrin was encapsulated in biodegradable polyelectrolyte:polymer NPs and embedded within a hyaluronic acid/PCL nanofiber hydrogel composite (NHC). The effect of locally delivered agrin-NP/NHC on NMJ reinnervation was assessed using a forelimb chronic denervation nerve injury model. Animals were injected with agrin-NP/NHC, free agrin, or empty-NP/NHC every six weeks from time of nerve injury and underwent 16 weeks of functional assessment. RESULTS: Agrin-NP/NHC animals exhibited significantly increased functional recovery compared to free agrin (p<0.01) and empty-NP/NHC animals (p<0.01) At Week 15, Agrin-NP/NHC animals demonstrated an increase of 21.2% compared to free agrin (p=0.056) and of 26.8% compared to empty-NP/NHC (p<0.05). Agrin-NP/NHC animals demonstrated significantly greater NMJ reinnervation than free agrin (78.9% vs 66.8%, p<0.05) and empty-NP/NHC groups (78.9% vs 39.2%, p<0.001). No significant differences were seen in myofibril cross-sectional area between treatment groups. No foreign body response was detected in empty-NP/NHC or agrin-NP/NHC animals. Agrin levels were undetectable in serum and were significantly higher in agrin-NP/NHC than free agrin animals. CONCLUSION: Agrin-NP/NHC treatment in vivo promotes neuromuscular junction reinnervation and improves functional recovery of forelimb grip strength.