Regeneration of peripheral nerves by nerve guidance conduits: Influence of design, biopolymers, cells, growth factors, and physical stimuli

Injuries to the peripheral nervous system (PNS) cause neuropathies that lead to weakness and paralysis, poor or absent sensation, unpleasant and painful neuropathies, and impaired autonomic function. In this regard, implanted artificial nerve guidance conduits (NGCs) used to bridge an injured site may provide appropriate biochemical and biophysical guidance cues required to stimulate regeneration across a nerve gap and restore the function of PNS. Advanced conduit design and fabrication techniques have made it possible to fabricate autograft-like structures in the NGCs with incredible precision. To this end, strategies involving the use of biopolymers, cells, growth factors, and physical stimuli have been developed over the past decades and have led to the development of varying NGCs, from simple hollow tubes to complex conduits that incorporate one or more guidance cues. This paper briefly reviews the recent progress in the development of these NGCs for nerve regeneration, focusing on the design and fabrication of NGCs, as well as the influence of biopolymers, cells, growth factors, and physical stimuli. The advanced techniques used to fabricate NGCs that incorporate cells/growth factors are also discussed, along with their merits and flaws. Key issues and challenges with regard to the development of NGCs have been identified and discussed, and recommendations for future research have been included.