Autologous fat grafting for nerve regeneration and neuropathic pain: current state from bench-to-bedside.

Despite recent advances in microsurgical techniques, functional recovery following peripheral nerve injury remains slow and inadequate. Poor peripheral nerve regeneration not only leaves patients with significant impairments, but also commonly leads to the development of debilitating neuropathic pain. Recent research has demonstrated the potential therapeutic benefits of adipose-derived stem cells, to enhance nerve regeneration. However, clinical translation remains limited due to the current regulatory burdens of the US FDA. A reliable and immediately translatable alternative is autologous fat grafting, where native adipose-derived stem cells present in the transferred tissue can potentially act upon regenerating axons. This review presents the scope of adipose tissue-based therapies to enhance outcomes following peripheral nerve injury, specifically focusing on their role in regeneration and ameliorating neuropathic pain.

Fibrin gels containing GDNF microspheres increase axonal regeneration after delayed peripheral nerve repair.

AIM: Recovery following nerve transection declines when target reconnection is delayed for prolonged periods. GDNF has previously been shown to promote motor axon regeneration following delayed nerve repair. MATERIALS & METHODS: We constructed delivery systems using fibrin gels containing free GDNF or poly(lactide-co-glycolide) microspheres with GDNF. The delivery systems were implanted with fluorescent fibrinogen surrounding the common fibular (CF; peroneal) nerve in transgenic Thy-1 GFP rats (whose axons express GFP) to track degradation of the system. A delayed nerve repair model was designed by transecting the rat CF nerve, where nerve regeneration was prevented by ligating the two stumps to surrounding muscle for 2 months prior to resuture. At resuture, either a delivery system with GDNF or an additional group consisting of fibrin gels with empty microspheres were implanted surrounding the repair site. In an additional positive control, the CF was transected and repaired immediately without delay. RESULTS: ELISA assays demonstrated GDNF release in vitro for 2 weeks from fibrin gels with GDNF microspheres. Implanted delivery systems, including GDNF microspheres, remained surrounding the nerve for at least 10 days compared with 3 days for free GDNF. Four weeks after repair, histomorphometry of distal nerve cross-sections taken 20 mm from the repair site demonstrated increased fiber diameter and myelin thickness due to release of GDNF from microspheres compared with empty microspheres. Additionally, the number of motoneurons that regenerated their axons to the same site increased to comparable levels as immediate repair due to the extended delivery of GDNF from microspheres. CONCLUSION: These findings demonstrate that early measures of nerve regeneration after delayed nerve repair is improved by GDNF microspheres implanted at the coaptation site.