Figure 4.

Tissue engineering approaches to peripheral nerve regeneration. Current approaches being researched include A) Developing advanced microarchitecture such as (left to right) aligned filaments,^[99] porous sponges,^[100] and micro-channels^[101] in 3D scaffolds. B) Controlled release of neural growth factors to enhance regeneration.^[102] C) Embedding supportive cells, such as Schwann cells^[103] or stem cells within 3D scaffolds.^[104,105] D) Mimicking natural extracellular matrix (ECM) of the peripheral nerves. To mimic the ECM, it is possible either to combine the components of the ECM^[106] or decellularize the natural peripheral nerve tissue.^[107] Combinations of above approaches are also being studied to utilize the advantages of various techniques. Current FDA approved techniques and approaches in the clinic include E) Autologous nerve grafts which are the current clinical gold standard for peripheral nerve regeneration. F) Hollow conduits have been translated to clinical product and approved by the FDA. Hollow conduits used in the clinic are composed of either natural (e.g., collagen I) or synthetic (e.g., polyglycolic acid) materials. These products can be either biodegradable or nondegradable. G) Decellularized nerve allografts (AxoGen, Inc.) were more recently approved for use in the clinic.