OBJECTIVE: The accuracy of motor axon regeneration becomes an important issue in the development of a nerve tube for motor nerve repair. Dispersion of regeneration across the nerve tube may lead to misdirection and polyinnervation. In this study, we present a series of methods to investigate the accuracy of regeneration, which we used to compare regeneration across autografts and single-lumen poly(lactic-co-glycolic acid) (PLGA) nerve tubes. We also present the concept of the multichannel nerve tube that may limit dispersion by separately guiding groups of regenerating axons.
METHODS: The simultaneous tracing of the tibial and peroneal nerves with fast blue and diamidino yellow was performed 8 weeks after the repair of a 1-cm nerve gap in the rat sciatic nerve to determine the percentage of double-projecting motoneurons. Sequential tracing of the peroneal nerve with diamidino yellow 1 week before repair and fast blue 8 weeks after repair was performed to determine the percentage of correctly directed peroneal motoneurons.
RESULTS: In the cases in which there was successful regeneration across single-lumen nerve tubes, more motoneurons had double projections to both the tibial and peroneal nerve branches after single-lumen nerve tube repair (21.4%) than after autograft repair (5.9%). After multichannel nerve tube repair, this percentage was slightly reduced (16.9%), although not significantly. The direction of regeneration was nonspecific after all types of repair.
CONCLUSION: Retrograde tracing techniques provide new insights into the process of regeneration across nerve tubes. The methods and data presented in this study can be used as a basis for the development of a nerve tube for motor nerve repair.
Cellular Neurobiology Laboratory and Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota (de Ruiter)
Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota (Spinner)
Department of Neurosurgery, Leiden University Medical Center, Leiden, the Netherlands (Malessy)
Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota (Moore)
Department of Neurology, Mayo Clinic, Rochester, Minnesota (Sorenson)
Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota (Currier)
Departments of Physiology and Biomedical Engineering and Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota (Yaszemski)
Cellular Neurobiology Laboratory and Department of Neurology, Mayo Clinic, Rochester, Minnesota (Windebank)
Reprint requests: Anthony J. Windebank, M.D., Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. Email: firstname.lastname@example.org
Received, May 23, 2007.
Accepted, April 21, 2008.