title: Annular puncture with tumor necrosis factor-alpha injection enhances painful behavior with disc degeneration in vivo.
abstract: BACKGROUND
  Painfulintervertebral disc degeneration is extremely common and costly. Effective treatments are lacking because the nature of discogenic pain is complex with limited capacity to distinguish painful conditions from age-related changes in the spine. Hypothesized sources of discogenic pain include chronic inflammation, neurovascular ingrowth, and structural disruption.
  
  
  OBJECTIVE
  This study aimed to investigate inflammation, pro-neurovascular growth factors, and structural disruption as sources of painful disc degeneration
  
  
  METHODS
  This study used an in vivo study to address these hypothesized mechanisms with anterior intradiscal injections of tumor necrosis factor-alpha (TNFα), pro-neurovascular growth factors: nerve growth factor and vascular endothelial growth factor (NGF and VEGF), and saline with additional sham surgery and naïve controls. Depth of annular puncture was also evaluated for its effects on structural and painful degeneration.
  
  
  METHODS
  Rat lumbar discs were punctured (shallow or deeper puncture) and intradiscally injected with saline, TNFα, or NGF and VEGF. Structural disc degeneration was assessed using X-ray, magnetic resonance imaging (MRI), and histology. The rat painful condition was evaluated using Von Frey hyperalgesia measurements, and substance P immunostaining in dorsal root ganglion (DRG) was performed to determine the source of pain.
  
  
  RESULTS
  Saline injection increased painful responses with degenerative changes in disc height, MRI intensity, and morphologies of disc structure and cell. TNFα and NGF/VEGF accelerated painful behavior, and TNFα-injected animals had increased substance P in DRGs. Deeper punctures led to more severe disc degeneration. Multiple regression analysis showed that the painful behavior was correlated with disc height loss.
  
  
  CONCLUSIONS
  We concluded that rate and severity of structural disc degeneration was associated with the amount of annular disruption and puncture depth. The painful behavior was associated with disc height loss and discal inflammatory state, whereas pro-inflammatory cytokines might play a more important role in the level of pain, which might have resulted from enhanced DRG sensitization. These in vivo painful disc degeneration models with different severities of structural changes may be useful for investigating discogenic pain mechanisms and for screening therapies, although interpretations must note the differences between all surgically induced animal models and the human condition.
authors.affiliation: Icahn School of Medicine at Mount Sinai, 1 Gustave Levy Place, Box 1188, Orthopaedics, New York, NY 10029-6574.
authors.forename: Alon
authors.initials: A
authors.lastname: Lai
authors.affiliation: Icahn School of Medicine at Mount Sinai, 1 Gustave Levy Place, Box 1188, Orthopaedics, New York, NY 10029-6574.
authors.forename: Andrew
authors.initials: A
authors.lastname: Moon
authors.affiliation: Icahn School of Medicine at Mount Sinai, 1 Gustave Levy Place, Box 1188, Orthopaedics, New York, NY 10029-6574; The Ohio State University, Dorothy Davis Heart and Lung Research Institute, 473 W 12th Avenue, Room 012L, Columbus OH 43210.
authors.forename: Devina
authors.initials: D
authors.lastname: Purmessur
authors.affiliation: 5 E 98th St#1259, New York, NY 10029, United States.
authors.forename: Branko
authors.initials: B
authors.lastname: Skovrlj
authors.affiliation: Icahn School of Medicine at Mount Sinai, 1 Gustave Levy Place, Box 1188, Orthopaedics, New York, NY 10029-6574.
authors.forename: Damien M
authors.initials: DM
authors.lastname: Laudier
authors.affiliation: 240 Skirkanich Hall 210 S. 33rd St Philadelphia, PA 19104-6321.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Winkelstein
authors.affiliation: Icahn School of Medicine at Mount Sinai, 1 Gustave Levy Place, Box 1188, Orthopaedics, New York, NY 10029-6574.
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Cho
authors.affiliation: Icahn School of Medicine at Mount Sinai, 1 Gustave Levy Place, Box 1188, Orthopaedics, New York, NY 10029-6574.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Hecht
authors.affiliation: Icahn School of Medicine at Mount Sinai, 1 Gustave Levy Place, Box 1188, Orthopaedics, New York, NY 10029-6574. Electronic address: james.iatridis@mssm.edu.
authors.forename: James C
authors.initials: JC
authors.lastname: Iatridis
mesh_terms: D000818:Animals; D000070616:Annulus Fibrosus; D001522:Behavior, Animal / Q000187:drug effects*; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D006930:Hyperalgesia / Q000378:metabolism / Q000503:physiopathology*; D007267:Injections; D007403:Intervertebral Disc; D055959:Intervertebral Disc Degeneration; D008159:Lumbar Vertebrae; D008297:Male; D020932:Nerve Growth Factor / Q000494:pharmacology*; D010146:Pain / Q000378:metabolism / Q000503:physiopathology*; D011677:Punctures; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013373:Substance P / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology*
chemical_list: D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; D013373:Substance P; D020932:Nerve Growth Factor
keywords: Animal model; Discogenic pain; Hindpaw mechanical hyperalgesia; Intervertebral disc degeneration; Nerve growth factor; Tumor necrosis factor-alpha