Challenges to nerve regeneration.

Peripheral nerve injuries can result from mechanical, thermal, chemical, congenital, or pathological etiologies. Failure to restore these damaged nerves can lead to the loss of muscle function, impaired sensation, and painful neuropathies. Current surgical strategies for the repair of critical nerves involve the transfer of normal donor nerve from an uninjured body location. However, these "gold standard" methods for tissue restoration frequently are limited by tissue availability, risk of disease spread, secondary deformities, and potential differences in tissue structure and size. One possible alternative to autogenous tissue replacement is the development of engineered constructs to replace those elements necessary for axonal proliferation, including a scaffold, support cells, induction factors, and extracellular matrices. Despite advances and contributions in the field of tissue engineering, results to date with nerve conduits have failed to equal the nerve regeneration achieved with autogenous grafts for large distances. We review the current challenges to tissue-engineered constructs. Each of the four components is reviewed and approaches are outlined. Semin. Surg. Oncol. 19:312-318, 2000.