title: Axonal growth potential of lumbar dorsal root ganglion neurons in an organ culture system: response of nerve growth factor-sensitive neurons to neuronal injury and an inflammatory cytokine.
abstract: METHODS
  The axonal growth potential of dorsal root ganglion (DRG) neurons in an organ culture system was investigated.
  
  
  OBJECTIVE
  To examine the effects of neuronal injury and tumor necrosis factor-alpha (TNF-alpha) on the axonal growth potential of 2 types of nociceptive DRG neurons: nerve growth factor (NGF)-sensitive and glial cell line-derived neurotrophic factor (GDNF)-sensitive neurons.
  
  
  BACKGROUND
  Nerve ingrowth into the disc is recognized to be one of the causes of discogenic pain. Almost all of these disc-innervating neurons are NGF-sensitive. The axonal growth potential of NGF-sensitive neurons has not been investigated.
  
  
  METHODS
  Adult Sprague-Dawley rats were used for immunohistochemistry (n = 7) and cell viability studies (n = 6). Bilateral L3-L5 DRGs, which were successfully removed without damage, were noncultured or cultured in serum-free medium containing TNF-alpha at 0, 0.01, 0.1, and 1 ng/mL for 48 hours (n = 5, each treatment). The DRGs were then immunostained for activating transcription factor 3 (ATF3, a marker for injured neurons) or double-stained for growth-associated protein 43 (GAP-43, a marker for axonal growth) with calcitonin gene-related peptide (CGRP, a marker for NGF-sensitive neurons) or isolectin B4 (IB4, a marker for GDNF-sensitive neurons). Cell viability was assessed by a lactate dehydrogenase (LDH) assay and an MTS assay (n = 6, each treatment).
  
  
  RESULTS
  Immunoreactive evidence of injured neurons (ATF3 positive) was frequently observed in cultured DRGs, but never in noncultured DRGs. The percentage of neurons exhibiting axonal growth potential (GAP-43 immunoreactive) was significantly higher for NGF-sensitive neurons than for GDNF-sensitive neurons at any concentration of TNF-alpha. More than 95% of the cultured neurons were viable.
  
  
  CONCLUSIONS
  The results suggest that the cultured DRG neurons exhibit pathologic changes similar to those found in injured neurons. NGF-sensitive neurons, which include disc-innervating neurons, may have a greater potential to extend their axons in response to neuronal injury under pathologic conditions in the presence of TNF-alpha than GDNF-sensitive neurons.
authors.affiliation: Department of Orthopedic Surgery, Rush Medical College at Rush University Medical Center, Chicago, IL 60612, USA.
authors.forename: Yasuchika
authors.initials: Y
authors.lastname: Aoki
authors.forename: Howard S
authors.initials: HS
authors.lastname: An
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
authors.forename: Kei
authors.initials: K
authors.lastname: Miyamoto
authors.forename: Mary Ellen
authors.initials: ME
authors.lastname: Lenz
authors.forename: Hideshige
authors.initials: H
authors.lastname: Moriya
authors.forename: Koichi
authors.initials: K
authors.lastname: Masuda
mesh_terms: D051700:Activating Transcription Factor 3 / Q000378:metabolism; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D019922:GAP-43 Protein / Q000378:metabolism; D005727:Ganglia, Spinal / Q000187:drug effects / Q000293:injuries / Q000473:pathology; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000494:pharmacology*; D007150:Immunohistochemistry; D007403:Intervertebral Disc / Q000294:innervation; D008159:Lumbar Vertebrae; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D051700:Activating Transcription Factor 3; C497108:Atf3 protein, rat; D019922:GAP-43 Protein; D051100:Glial Cell Line-Derived Neurotrophic Factor; D014409:Tumor Necrosis Factor-alpha; D020932:Nerve Growth Factor