Human Epineural Sheath Conduit Augmented with Human Mesenchymal Stem Cells As a New Biologic Construct Supporting Peripheral Nerve Regeneration: A Preliminary Report

PURPOSE: Peripheral nerve injury (PNI) repair is a challenging task, resulting in unsatisfactory outcomes. Rat epineural sheath conduit supported with rat bone marrow-derived stromal cells demonstrated neuroregenerative potential. To bring this approach closer to clinical applications we developed a new biologic construct for nerve regeneration - human epineural conduit (hEC) consisting of human epineural sheath (hES) filled with human mesenchymal stem cells (hMSC). The aim of this study was to assess the feasibility of hEC on the PNI repair in the nude rat model.

METHODS: Sciatic nerve defect (20mm) was created in 24 nude male rats. Animals were divided into four experimental groups: Group 1 - no repair; Group 2 - autograft; Group 3 - hES filled with saline; and Group 4 - hEC (supported with 3-4 x 10^6 hMSC ). hES was created by fascicles removal using pull-out technique. To ensure homogenicity of hMSC, cells were cultured for 14 days and immunostained for hMSC-specific markers prior to injection into the hES. Outcome assessment included: sensory pinprick (PP) and motor toe-spread (TS) tests at 1, 3, 6, 12 weeks. Somatosensory evoked potentials (SSEP), gastrocnemius muscle index (GMI), histomorphometry, fluorescent immunostaining for GFAP, NGF, S-100, HLA I / II, vWF and laminin B2 were performed 12 weeks post-surgery.

RESULTS: Cultured hMSC expressed CD105, CD73 and CD90, and lacked expression of CD45, CD34, CD14, CD11b, CD79a, CD19 and HLA-DR surface molecules. No leakage of cells was observed at the time of injection during conduit implantation. hEC maintained its shape and integrity at 12 weeks following repair. No local inflammation or scarring was observed at the end of the follow up. Clinical evaluation and SSEP analysis confirmed sciatic nerve recovery in groups 3 and 4 with outcomes comparable to nerve autograft repair. Immunostaining showed presence of the hMSC in the conduit at 12 weeks post-implantation. Quantitative nerve and muscle histological analysis is currently in progress.

CONCLUSION: The feasibility of the application of hEC for restoration of PNI was successfully confirmed in this study. The functional outcomes following the use of hEC were comparable to the golden standard of autograft repair. hEC is a promising new technology for regeneration of long nerve gap defects which combines the effect of neurotropic properties of hES and immunomodulating properties of hMSC.