The primary purpose of this research study is to evaluate the safety and possible harms of injecting one's own Schwann cells along with nerve auto-graft after a severe injury to a major nerve has occurred.

Inclusion Criteria:

1. Persons with severe sciatic nerve injury, brachial plexus injury, and/or major nerve injury at the upper or lower extremity within previous year;
2. Between the ages of 18 and 65 at last birthday

Exclusion Criteria:

1. Persons unable to safely undergo an MRI;
2. Persons with pre-existing conditions that would preclude satisfactory sural nerve harvest;
3. Persons with severe peripheral nerve injury gap length > 10 cm;
4. Persons with history of radiation or local cancer in area of nerve injury, including primary tumors of the nerve;
5. Pregnant women or a positive pregnancy test in those women with reproductive potential prior to enrollment;
6. Presence of disease that might interfere with participant safety, compliance, or evaluation of the condition under study;
7. History of active substance abuse;
8. Persons allergic to gentamicin;
9. Persons who test positive for HIV or Hepatitis B or C virus.
10. Persons unable to provide consent independently due to cognitive impairment