title: Biological response of the intervertebral disc to repetitive short-term cyclic torsion.
abstract: METHODS
  In vitro study of the biological response of the intervertebral disc (IVD) to cyclic torsion by using bovine caudal IVDs.
  
  
  OBJECTIVE
  To evaluate the biological response of the IVD to repetitive cyclic torsion of varying magnitudes at a physiological frequency.
  
  
  BACKGROUND
  Mechanical loading is known to be a risk factor for disc degeneration (DD) but the role of torsion in DD is controversial. It has been suggested that a small magnitude of spinal rotation decreases spinal pressure, increases spinal length, and enhances nutrition exchange in the IVD. However, athletes who participate actively in sports involving torsional movement of the spine are frequently diagnosed with DD and/or disc prolapse.
  
  
  METHODS
  Bovine caudal discs with end plates were harvested and kept in custom-made chambers for in vitro culture and mechanical stimulation. Torsion was applied to the explants for 1 hour/day over four consecutive days by using a servohydraulic testing machine. The biological response was evaluated by cell viability, metabolic activity, gene expression, glycosaminoglycan content, and histological evaluation.
  
  
  RESULTS
  A significantly higher cell viability was found in the inner annulus of the 2˚ torsion group than in the static control group. A trend of decreasing metabolic activity in the nucleus pulposus with increasing torsion magnitude was observed. Apoptotic activity in the nucleus pulposus significantly increased with 5˚ torsion. No statistical significant difference in gene expression was found between the three torsion angles. No visible change in matrix organization could be observed by histological evaluation.
  
  
  CONCLUSIONS
  The IVD can tolerate short-term repetitive cyclic torsion, as tested in this study. A small angle of cyclic torsion can be beneficial to the IVD in organ culture, possibly by improving nutrition and waste exchange, whereas large torsion angle may cause damage to disc in the long term.
authors.affiliation: ARTORG, Institute for Surgical Technology and Biomechanics, University of Bern, Bern, Switzerland.
authors.forename: Samantha C W
authors.initials: SC
authors.lastname: Chan
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ferguson
authors.forename: Karin
authors.initials: K
authors.lastname: Wuertz
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gantenbein-Ritter
mesh_terms: D051722:ADAM Proteins / Q000235:genetics; D000071121:ADAMTS4 Protein; D053674:Aggrecans / Q000235:genetics; D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D002417:Cattle; D002470:Cell Survival; D024042:Collagen Type I / Q000235:genetics; D005786:Gene Expression Regulation; D006025:Glycosaminoglycans / Q000378:metabolism; D007403:Intervertebral Disc / Q000166:cytology / Q000378:metabolism*; D053509:Matrix Metalloproteinase 13 / Q000235:genetics; D019278:Matrix Metalloproteinase 3 / Q000235:genetics; D009924:Organ Culture Techniques; D011348:Procollagen N-Endopeptidase / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D054159:Torsion, Mechanical
chemical_list: D053674:Aggrecans; D024042:Collagen Type I; D006025:Glycosaminoglycans; D053148:Caspase 3; D053179:Caspase 7; D051722:ADAM Proteins; D053509:Matrix Metalloproteinase 13; D011348:Procollagen N-Endopeptidase; D019278:Matrix Metalloproteinase 3; D000071121:ADAMTS4 Protein