title: Characterization of dendritic morphology and neurotransmitter phenotype of thoracic descending propriospinal neurons after complete spinal cord transection and GDNF treatment.
abstract: After spinal cord injury (SCI), poor regeneration of damaged axons of the central nervous system (CNS) causes limited functional recovery. This limited spontaneous functional recovery has been attributed, to a large extent, to the plasticity of propriospinal neurons, especially the descending propriospinal neurons (dPSNs). Compared with the supraspinal counterparts, dPSNs have displayed significantly greater regenerative capacity, which can be further enhanced by glial cell line-derived neurotrophic factor (GDNF). In the present study, we applied a G-mutated rabies virus (G-Rabies) co-expressing green fluorescence protein (GFP) to reveal Golgi-like dendritic morphology of dPSNs. We also investigated the neurotransmitters expressed by dPSNs after labeling with a retrograde tracer Fluoro-Gold (FG). dPSNs were examined in animals with sham injuries or complete spinal transections with or without GDNF treatment. Bilateral injections of G-Rabies and FG were made into the 2nd lumbar (L2) spinal cord at 3 days prior to a spinal cord transection performed at the 11th thoracic level (T11). The lesion gap was filled with Gelfoam containing either saline or GDNF in the injury groups. Four days post-injury, the rats were sacrificed for analysis. For those animals receiving G-rabies injection, the GFP signal in the T7-9 spinal cord was visualized via 2-photon microscopy. Dendritic morphology from stack images was traced and analyzed using a Neurolucida software. We found that dPSNs in sham injured animals had a predominantly dorsal-ventral distribution of dendrites. Transection injury resulted in alterations in the dendritic distribution with dorsal-ventral retraction and lateral-medial extension. Treatment with GDNF significantly increased the terminal dendritic length of dPSNs. The density of spine-like structures was increased after injury, and treatment with GDNF enhanced this effect. For the group receiving FG injections, immunohistochemistry for glutamate, choline acetyltransferase (ChAT), glycine, and GABA was performed in the T7-9 spinal cord. We show that the majority of FG retrogradely-labeled dPSNs were located in the Rexed Lamina VII. Over 90% of FG-labeled neurons were glutamatergic, with the other three neurotransmitters contributing less than 10% of the total. To our knowledge this is the first report describing the morphologic characteristics of dPSNs and their neurotransmitter expressions, as well as the dendritic response of dPSNs after transection injury and GDNF treatment.
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202; Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery, Goodman and Campbell Brain and Spine, Indiana University School of Medicine, Indianapolis, Indiana 46202.
authors.forename: Lingxiao
authors.initials: L
authors.lastname: Deng
authors.affiliation: Guangdong-Hong Kong-Macau Institute for CNS Regeneration (GHMICR), Jinan University, Guangzhou,China, 510632.
authors.forename: Yiwen
authors.initials: Y
authors.lastname: Ruan
authors.affiliation: Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery, Goodman and Campbell Brain and Spine, Indiana University School of Medicine, Indianapolis, Indiana 46202.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery, Goodman and Campbell Brain and Spine, Indiana University School of Medicine, Indianapolis, Indiana 46202.
authors.forename: Christian Corbin
authors.initials: CC
authors.lastname: Frye
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202; Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery, Goodman and Campbell Brain and Spine, Indiana University School of Medicine, Indianapolis, Indiana 46202.
authors.forename: Wenhui
authors.initials: W
authors.lastname: Xiong
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202; Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery, Goodman and Campbell Brain and Spine, Indiana University School of Medicine, Indianapolis, Indiana 46202.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Jin
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202; Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery, Goodman and Campbell Brain and Spine, Indiana University School of Medicine, Indianapolis, Indiana 46202.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Jones
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405.
authors.forename: Dale
authors.initials: D
authors.lastname: Sengelaub
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202; Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery, Goodman and Campbell Brain and Spine, Indiana University School of Medicine, Indianapolis, Indiana 46202. Electronic address: xu26@iupui.edu.
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Xu
mesh_terms: D000818:Animals; D003712:Dendrites / Q000473:pathology* / Q000648:ultrastructure; D004195:Disease Models, Animal; D005260:Female; D007839:Functional Laterality; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000627:therapeutic use*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000473:pathology / Q000648:ultrastructure; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010641:Phenotype; D011712:Pyramidal Tracts / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D020127:Recovery of Function / Q000187:drug effects*; D016622:Silver Staining; D013119:Spinal Cord Injuries / Q000188:drug therapy* / Q000473:pathology; D013266:Stilbamidines
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D051100:Glial Cell Line-Derived Neurotrophic Factor; D018377:Neurotransmitter Agents; D013266:Stilbamidines; D049452:Green Fluorescent Proteins
keywords: Dendrite; Descending propriospinal neuron; GDNF; Rabies virus; Spinal cord injury; Spine