title: Investigating the role of DNA damage in tobacco smoking-induced spine degeneration.
abstract: BACKGROUND
  Tobacco smoking is a key risk factor for spine degeneration. However, the underlying mechanism by which smoking induces degeneration is not known. Recent studies implicate DNA damage as a cause of spine and intervertebral disc degeneration. Because tobacco smoke contains many genotoxins, we hypothesized that tobacco smoking promotes spine degeneration by inducing cellular DNA damage.
  
  
  OBJECTIVE
  To determine if DNA damage plays a causal role in smoking-induced spine degeneration.
  
  
  METHODS
  To compare the effect of chronic tobacco smoke inhalation on intervertebral disc and vertebral bone in normal and DNA repair-deficient mice to determine the contribution of DNA damage to degenerative changes.
  
  
  METHODS
  Two-month-old wild-type (C57BL/6) and DNA repair-deficient Ercc1(-/Δ) mice were exposed to tobacco smoke by direct inhalation (4 cigarettes/day, 5 days/week for 7 weeks) to model first-hand smoking in humans. Total disc proteoglycan (PG) content (1,9-dimethylmethylene blue assay), PG synthesis ((35)S-sulfate incorporation assay), aggrecan proteolysis (immunoblotting analysis), and vertebral bone morphology (microcomputed tomography) were measured.
  
  
  RESULTS
  Exposure of wild-type mice to tobacco smoke led to a 19% increase in vertebral porosity and a 61% decrease in trabecular bone volume. Intervertebral discs of smoke-exposed animals also showed a 2.6-fold decrease in GAG content and an 8.1-fold decrease in new PG synthesis. These smoking-induced degenerative changes were similar but not worse in Ercc1(-/Δ) mice.
  
  
  CONCLUSIONS
  Short-term exposure to high levels of primary tobacco smoke inhalation promotes degeneration of vertebral bone and discs. Disc degeneration is primarily driven by reduced synthesis of proteoglycans needed for vertebral cushioning. Degeneration was not exacerbated in congenic DNA repair-deficient mice, indicating that DNA damage per se does not have a significant causal role in driving smoke-induced spine degeneration.
authors.affiliation: Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Department of Orthopaedic Surgery, Catholic University of Rome School of Medicine, "A. Gemelli" University Hospital, l.go Agostino Gemelli 8, 00168 Roma, Italy.
authors.forename: Luigi A
authors.initials: LA
authors.lastname: Nasto
authors.affiliation: Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Ngo
authors.affiliation: Department of Medicine, University of Pittsburgh School of Medicine, 3550 Terrace St, Pittsburgh, PA 15213, USA.
authors.forename: Adriana S
authors.initials: AS
authors.lastname: Leme
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.
authors.forename: Andria R
authors.initials: AR
authors.lastname: Robinson
authors.affiliation: Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Dong
authors.affiliation: McGill Scoliosis and Spine Group, Genetics Unit, Shriners Hospital for Children, Montreal, Quebec H3G 1A6, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Roughley
authors.affiliation: Department of Orthopaedic Surgery of UPMC, Stem Cell Research Center, Pittsburgh, PA 15261, USA.
authors.forename: Arvydas
authors.initials: A
authors.lastname: Usas
authors.affiliation: Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
authors.forename: Gwendolyn A
authors.initials: GA
authors.lastname: Sowa
authors.affiliation: Department of Orthopaedic Surgery, Catholic University of Rome School of Medicine, "A. Gemelli" University Hospital, l.go Agostino Gemelli 8, 00168 Roma, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Pola
authors.affiliation: Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
authors.forename: James
authors.initials: J
authors.lastname: Kang
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA; Department of Metabolism and Aging, The Scripps Research Institute, 130 Scripps Way #3B3, Jupiter, FL 33458-5284, USA.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Niedernhofer
authors.affiliation: Department of Medicine, University of Pittsburgh School of Medicine, 3550 Terrace St, Pittsburgh, PA 15213, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Shapiro
authors.affiliation: Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA. Electronic address: von@upmc.edu.
authors.forename: Nam V
authors.initials: NV
authors.lastname: Vo
mesh_terms: D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D004249:DNA Damage / Q000502:physiology*; D004195:Disease Models, Animal; D005260:Female; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000378:metabolism; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011509:Proteoglycans / Q000378:metabolism; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D055114:X-Ray Microtomography
chemical_list: D053674:Aggrecans; D011509:Proteoglycans
keywords: Aggrecan; DNA damage repair; Intervertebral disc degeneration; Matrix metalloproteinases; Matrix proteoglycans; Tobacco smoking