title: A combination of BDNF and NT-3 promotes supraspinal axonal regeneration into Schwann cell grafts in adult rat thoracic spinal cord.
abstract: We previously demonstrated that Schwann cells (SCs) in semipermeable guidance channels promote axonal regeneration in adult rat spinal cord transected at the mid-thoracic level. Propriospinal but not supraspinal axons grew into these channels. Here, we tested the ability of exogenous brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) to promote axonal regeneration in this novel model. The two neurotrophins were delivered simultaneously into the channel by an Alzet minipump at a rate of 12 micrograms/day for each neurotrophin for 14 of 30 days tested; phosphate-buffered saline, the vehicle solution, was used as a control. Significantly more myelinated nerve fibers were present in SC/neurotrophin grafts than in SC/vehicle grafts (1523 +/- 292 vs 882 +/- 287). In the graft, at least 5 mm from the rostral cord-graft interface, some nerve fibers were immunoreactive for serotonin, a neurotransmitter specific to raphe-derived axons in rat spinal cord. Fast blue retrograde tracing from SC/neurotrophin grafts revealed labeled neurons in 10 nuclei of the brain stem, 67% of these being in the lateral and spinal vestibular nuclei. The mean number of labeled brain stem neurons in the SC/neurotrophin group (92; n = 3) contrasted with the mean in the SC/vehicle group (6; n = 4). Our results clearly demonstrate that BDNF and NT-3 infusion enhanced propriospinal axonal regeneration and, more significantly, promoted axonal regeneration of specific distant populations of brain stem neurons into grafts at the mid-thoracic level in adult rat spinal cord.
authors.affiliation: Chambers Family Electron Microscopy Laboratory, Miami Project to Cure Paralysis, University of Miami School of Medicine, Florida 33136, USA.
authors.forename: X M
authors.initials: XM
authors.lastname: Xu
authors.forename: V
authors.initials: V
authors.lastname: Guénard
authors.forename: N
authors.initials: N
authors.lastname: Kleitman
authors.forename: P
authors.initials: P
authors.lastname: Aebischer
authors.forename: M B
authors.initials: MB
authors.lastname: Bunge
mesh_terms: D000818:Animals; D001369:Axons / Q000187:drug effects* / Q000648:ultrastructure; D019208:Brain-Derived Neurotrophic Factor; D005260:Female; D008959:Models, Neurological; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009416:Nerve Regeneration / Q000187:drug effects*; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D051381:Rats; D011916:Rats, Inbred F344; D012583:Schwann Cells / Q000637:transplantation*; D013116:Spinal Cord / Q000637:transplantation*; D016378:Tissue Transplantation
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins