title: TrkB gene therapy by adeno-associated virus enhances recovery after cervical spinal cord injury.
abstract: Unilateral cervical spinal cord hemisection at C2 (C2SH) interrupts descending bulbospinal inputs to phrenic motoneurons, paralyzing the diaphragm muscle. Recovery after C2SH is enhanced by brain derived neurotrophic factor (BDNF) signaling via the tropomyosin-related kinase subtype B (TrkB) receptor in phrenic motoneurons. The role for gene therapy using adeno-associated virus (AAV)-mediated delivery of TrkB to phrenic motoneurons is not known. The present study determined the therapeutic efficacy of intrapleural delivery of AAV7 encoding for full-length TrkB (AAV-TrkB) to phrenic motoneurons 3 days post-C2SH. Diaphragm EMG was recorded chronically in male rats (n=26) up to 21 days post-C2SH. Absent ipsilateral diaphragm EMG activity was verified 3 days post-C2SH. A greater proportion of animals displayed recovery of ipsilateral diaphragm EMG activity during eupnea by 14 and 21 days post-SH after AAV-TrkB (10/15) compared to AAV-GFP treatment (2/11; p=0.031). Diaphragm EMG amplitude increased over time post-C2SH (p<0.001), and by 14 days post-C2SH, AAV-TrkB treated animals displaying recovery achieved 48% of the pre-injury values compared to 27% in AAV-GFP treated animals. Phrenic motoneuron mRNA expression of glutamatergic AMPA and NMDA receptors revealed a significant, positive correlation (r(2)=0.82), with increased motoneuron NMDA expression evident in animals treated with AAV-TrkB and that displayed recovery after C2SH. Overall, gene therapy using intrapleural delivery of AAV-TrkB to phrenic motoneurons is sufficient to promote recovery of diaphragm activity, adding a novel potential intervention that can be administered after upper cervical spinal cord injury to improve impaired respiratory function.
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States; Department of Biomedical Engineering, Universidad de los Andes, Bogotá, Colombia.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Martínez-Gálvez
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States; Department of Biomedical Engineering, Universidad de los Andes, Bogotá, Colombia.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Zambrano
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Diaz Soto
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Wen-Zhi
authors.initials: WZ
authors.lastname: Zhan
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Gransee
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States; Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Gary C
authors.initials: GC
authors.lastname: Sieck
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, United States; Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, United States. Electronic address: mantilla.carlos@mayo.edu.
authors.forename: Carlos B
authors.initials: CB
authors.lastname: Mantilla
mesh_terms: D000818:Animals; D066193:Cervical Cord / Q000473:pathology; D002574:Cervical Vertebrae; D015316:Genetic Therapy / Q000379:methods*; D008297:Male; D008562:Membrane Glycoproteins / Q000008:administration & dosage / Q000235:genetics*; D011505:Protein-Tyrosine Kinases / Q000008:administration & dosage / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020813:Receptor, trkB; D020127:Recovery of Function / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000235:genetics* / Q000473:pathology / Q000628:therapy*
chemical_list: D008562:Membrane Glycoproteins; D011505:Protein-Tyrosine Kinases; D020813:Receptor, trkB; C000591259:tropomyosin-related kinase-B, human
keywords: Diaphragm muscle; Glutamatergic; Neuroplasticity; Neurotransmitter; Neurotrophin; Phrenic motoneuron; Respiratory; Serotonergic; Spinal hemisection