title: The evolutionary importance of cell ratio between notochordal and nucleus pulposus cells: an experimental 3-D co-culture study.
abstract: BACKGROUND
  Notochordal cells and nucleus pulposus cells are co-existing in the intervertebral disc at various ratios among different mammalians. This fact rises the question about the interactions and the evolutionary relevance of this phenomenon. It has been described that these relatively large notochordal cells are mainly dominant in early lifetime of all vertebrates and then differences occur with ageing. Human, cattle, sheep, and goat lose the cells with age, whereas rodents and lagomorphs maintain these throughout their lifetime.
  
  
  METHODS
  Here, we addressed the importance of cell ratio using alginate bead 3-D co-culture of bovine nucleus pulposus cells (bNPC) and porcine notochordal cells (pNCs) for 14 days using culture inserts.
  
  
  RESULTS
  We found a significant stimulation of bNPC in the presence of pNC in terms of cell activity and glycosaminoglycan production, but not for proliferation (DNA content). Relative gene expression was significantly stimulated for collagen type 2 and aggrecan.
  
  
  CONCLUSIONS
  The stimulating effect of NC was confirmed and the ideal ratio of NPC: NC was found to be ~50:50. This has direct implications for tissue-engineering approaches, which aim to repopulate discs with NP-like precursor cells.
authors.affiliation: ARTORG Center for Biomedical Engineering Research, Institute for Surgical Technology and Biomechanics, Medical Faculty, University of Bern, Stauffacherstrasse 78, 3014, Bern, Switzerland. benjamin.gantenbein@artorg.unibe.ch
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gantenbein-Ritter
authors.forename: Samantha C W
authors.initials: SC
authors.lastname: Chan
mesh_terms: D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D005075:Biological Evolution; D002417:Cattle; D002452:Cell Count; D049109:Cell Proliferation; D018920:Coculture Techniques; D024043:Collagen Type II / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000166:cytology* / Q000378:metabolism; D009672:Notochord / Q000166:cytology* / Q000378:metabolism; D013552:Swine
chemical_list: D053674:Aggrecans; D024043:Collagen Type II; D006025:Glycosaminoglycans