Peripheral nerve regeneration through hydrogel enriched chitosan conduits containing engineered Schwann cells for drug delivery

Critical length nerve defects in the rat sciatic nerve model were reconstructed with chitosan nerve guides filled with Schwann cell (SC) containing hydrogel. The transplanted SCs were naïve or have been genetically modified to over-express neurotrophic factors thus providing cellular neurotrophic factor delivery systems. Prior to the assessment in vivo, in vitro studies evaluating the properties of engineered SCs over-expressing glial cell line-derived derived neurotrophic factor (GDNF) or fibroblast growth factor 2 (FGF-2(18kDa)) demonstrated their neurite outgrowth inductive bioactivity for sympathetic PC-12 cells as well as for dissociated dorsal root ganglion cell drop cultures. The SCs were delivered into the lumen of chitosan hollow conduits with a 5% degree of acetylation within NVRhydrogel, which is mainly composed of hyaluronic acid and laminin. The viability and neurotrophic factor production by engineered SCs within NVR-Gel inside the chitosan nerve guides was further demonstrated in vitro. In vivo we studied the outcome of peripheral nerve regeneration after reconstruction of 15 mm nerve gaps with either chitosan/NVR-Gel/SCs composite nerve guides or autologous nerve grafts (ANGs). While ANGs did guarantee for functional sensory and motor regeneration in 100% of the animals, delivery of NVR-Gel into the chitosan nerve guides obviously impaired sufficient axonal outgrowth. This obstacle was overcome to a remarkable extent, when the NVR-Gel was enriched with FGF-2(18kDa) over-expressing SCs.