Individual Sciatic Nerve Branch Repair and Stem Cell Administration to Enhance Nerve Function Recovery in Limb Transplantation.

Abstract

Introduction: Since the first successful hand transplant in 1998, more than 89 upper extremity transplants have been performed worldwide. Unlike visceral organ transplants, hand or leg transplants require successful regeneration of nerve components and robust reinnervation of graft motor and sensory targets. We investigated whether MSC therapy can improve sensory and motor function in sciatic and individual nerve repair models. Methods: Lewis (RT1.Al) rat was anesthetized and sciatic or individual sciatic nerve branches (tibial, peroneal and sural) of the right hind-limb were transected. After one hour the epineurium of sciatic or individual nerves were approximated by 10-O sutures. Mesenchymal stem cells (MSC; 5 x106; passage ≤6) or vehicle (saline control) were administered locally (at the nerve repair sites) and intravenously. Walking track analysis (for motor function) and cutaneous pain reaction test (for sensory function) were performed at 1-2 week intervals following nerve repair. Results: Rat MSC expanded ex vivo were CD29+, CD90+, CD34-, CD31-, CD45low, MHC Class I+, and Class II-. MSC were pluripotent and differentiated in to adipocytes, osteocytes and chondrocytes in ex vivo cultures. At one week post nerve repair, total sensory nerve function in all groups was ≤0.4 on a scale of Grade 0-3 (0=No function; 3= Normal function). However, by 5 weeks in sciatic nerve repair (n ≥6) it was 1.9±0.4 compared to 2.4±0.7 in individual nerve repair (n ≥6) with MSC treatment; in the vehicle group it was 1.4±0.3 (sciatic nerve repair) and 1.8± 0.6 (individual nerve repair). Interestingly, peroneal sensory function appeared as early as one week ( ≥1.1) but not tibial or sural function. Sensory function was significantly (P<0.05) higher in MSC treated compared to untreated group; also, it was higher in individual nerve repair group. At four weeks post-individual nerve repair, the sciatic nerve function index (SFI) a measure of motor function (0 = normal function; -100 = nonfunctional) was - 42.9 and - 58.1 in MSC and vehicle treated groups, respectively; with sciatic nerve repair it was - 55.1 and - 65.9 in MSC and vehicle treated groups, respectively. Long-term nerve function recovery, histology, cellular and molecular studies are ongoing. Conclusions: Sciatic and individual nerve surgical repairs were highly successful. Individual nerve repair with MSC therapy appear to promote both motor and sensory nerve function recovery.