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A Bio and synthetic polymer based nerve guide tested under in vitro and in vivo conditions

Dursun Usal, Tuğba
Damages to the peripheral nervous system due to age, diseases or trauma may lead to gap formation in nervous tissue and inhibit signal transfer. Nerve guides are used to bridge the neural gaps created as a result of these events. This study describes the design, construction, and testing of a nerve guide which carries inner guidance elements to provide an appropriate microenvironment for peripheral nerve regeneration. A methacrylated gelatin-poly(2-hydroxyethyl methacrylate) (GelMA-pHEMA) hydrogel and 3D printed polycaprolactone (PCL) tube were produced as the exterior part of the nerve guide. Inner guidance elements, gelatin-poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) aligned fibers, were produced to provide PC12 cell alignment. Both GelMA-pHEMA hydrogels and PCL tube were suitable for Schwann cell (SC) attachment and proliferation. PC12 cells, seeded on gelatin-PHBV aligned fibrous mats, were aligned along the fiber axis and showed neurite outgrowth. Gelatin-PHBV fibrous mats were rolled and implanted into the 3D printed PCL tube to obtain a whole nerve guide structure. Over three weeks, cell number increased significantly. SCs were attached to the PCL tube, connected to each other and showed myelination. PC12 cells were also attached, proliferated and migrated from proximal to distal part on the gelatin-PHBV aligned mats. The increase in expression of neuronal markers such as beta-III tubulin and NeuN indicated the differentiation of PC12 cells into neurons. This composite nerve guide was tested under in vivo conditions. 10 mm sciatic nerve defect was created in rats and different types of nerve guides were implanted at the injury site. Both walking track analysis and electrophysiology studies showed that there is a functional recovery in the groups having PCL tube and PCL tube with gelatin-PHBV mat and SCs. These results show the potential of the developed nerve guide for the peripheral nerve regeneration under in vitro and in vivo conditions.