Mesenchymal stem cell therapy to promote functional recovery in a limb transplant model

Abstract Introduction: Battlefield trauma leads to limb amputations. We investigated whether Mesenchymal Stem Cell (MSC) therapy can improve nerve regeneration and functional outcome in limb transplantation (Tx). Methods: We performed orthotopic syngeneic hind-limb Tx in Lewis rats. Following Tx rats received syngeneic MSC (2×10 6; passage ≤6) or vehicle i.v. and locally via hydrogel. Limb sensory function (SF) and motor function (MF) were assessed weekly and at study endpoint (16 weeks) limb tissues were harvested for cell/molecular analysis. Results: SF in the tibial, peroneal/sural and saphenous nerve boundaries recovered as early as 5, 6 and 8 weeks, respectively. Total limb SF did not vary (P>0.05) between MSC and control groups; recovery was gradual at week 8 (Grade 1.4), week 12 (Grade 2.3) and week 16 (2.6) on a scale of Grade 0–3 (0, no function; 3, optimal function). A novel grading system was used to assess MF based on walking track footprints: Grade 0–4 (0, no footprint; 4, heel and 4–5 toe prints). MF was significantly (P<0.05) improved with MSC compared to controls at week 8 (Grade 1.33 Vs 0.5) and at week 16 (Grade 2.66 Vs 0.6). Ex vivoexpanded rat MSCs were CD29 +, CD31 −, CD34 −, CD44 +, CD45 low, CD90 +, MHC Class I +, Class II −and pluripotent. Neurofilament M (axonal marker), S100 and Krox20 (myelinating Schwann cells), Oct6 (Pre-myelinating Schwann cells) and GAP43 (regeneration marker) expressions were increased (P<0.05) and GFAP (non-myelinating Schwann cells) were reduced (P<0.05) in the distal portion of the sciatic nerve in MSC treated rats compared to controls. Conclusion: MSC administration following limb Tx appears to promote limb function recovery and is attributed to enhanced nerve regeneration/myelination/innervation. DoD –CDMRPL-19-0-DM190329 grant (PI, Salgar)