Construction of tissue engineered nerve grafts and their application in peripheral nerve regeneration

Surgical repair of severe peripheral nerve injuries represents not only a pressing medical need, but also a great clinical challenge. Autologous nerve grafting remains a golden standard for bridging an extended gap in transected nerves. The formidable limitations related to this approach, however, have evoked the development of tissue engineered nerve grafts as a promising alternative to autologous nerve grafts. A tissue engineered nerve graft is typically constructed through a combination of a neural scaffold and a variety of cellular and molecular components. The initial and basic structure of the neural scaffold that serves to provide mechanical guidance and optimal environment for nerve regeneration was a single hollow nerve guidance conduit. Later there have been several improvements to the basic structure, especially introduction of physical fillers into the lumen of a hollow nerve guidance conduit. Up to now, a diverse array of biomaterials, either of natural or of synthetic origin, together with well-defined fabrication techniques, has been employed to prepare neural scaffolds with different structures and properties. Meanwhile different types of support cells and/or growth factors have been incorporated into the neural scaffold, producing unique biochemical effects on nerve regeneration and function restoration. This review attempts to summarize different nerve grafts used for peripheral nerve repair, to highlight various basic components of tissue engineered nerve grafts in terms of their structures, features, and nerve regeneration-promoting actions, and finally to discuss current clinical applications and future perspectives of tissue engineered nerve grafts.