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Nerve Graft Modality Matching Directs Regeneration of Mixed Peripheral Nerves
Simone W. Glaus; Scott Farber, MD; Daniel A. Hunter; Philip J. Johnson; Susan E. Mackinnon
Washington University, Saint Louis, MO, USA
Introduction: When provided equal access to motor and sensory pathways, injured motor neurons preferentially regenerate down motor pathways—a phenomenon termed preferential motor reinnervation. It was previously hypothesized that preferential motor reinnervation would result in improved motor neuron regeneration across a nerve graft if the graft was harvested from a donor motor, rather than sensory, nerve. While initial studies demonstrated a regenerative advantage with grafts derived from motor nerves, more recent results have been conflicting. The aim of this study was to evaluate the efficacy of nerve regeneration through grafts of mixed, motor, and sensory nerve origin in a rat peripheral nerve model. Both fresh and acellularized grafts were evaluated, to serve as correlates to clinical nerve autografts and acellular nerve allografts.
Methods: 48 adult male Lewis rats were randomized to one of six groups and underwent transection of the unbranched portion (mixed nerve) of the femoral nerve and placement of a 1 cm nerve graft of mixed (peroneal), motor (femoral motor branch to the quadriceps), or sensory (femoral sensory branch) origin. Half of the animals received fresh grafts; the other half received grafts acellularized via the well-established Hudson protocol. The animals were sacrificed six weeks postoperatively, and the grafted portion of the unbranched femoral nerve was harvested along with its distal motor and sensory branches. Histomorphometry was performed on nerve sections from the distal motor and sensory branches, distal to the nerve graft.
Results: Some regeneration was present in all groups. Mixed and motor nerve grafts, whether fresh or acellularized, trended toward supporting improved regeneration into the motor branch compared to sensory nerve grafts. Fresh mixed and fresh motor grafts showed statistically significant superiority to acellularized sensory grafts. Fresh sensory grafts significantly outperformed mixed and motor grafts for regeneration into the sensory branch.
Conclusions: Nerve graft origin—motor or mixed versus sensory—influences the quality and specificity of regeneration. The clinical implication of graft modality matching is using a donor motor nerve graft (e.g., nerve to gracilis muscle, intercostal nerve) when grafting a critical mixed or motor nerve, in order to promote optimal regeneration.
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