title: Intradiscal application of rhBMP-7 does not induce regeneration in a canine model of spontaneous intervertebral disc degeneration.
abstract: BACKGROUND
  Strategies for biological repair and regeneration of the intervertebral disc (IVD) by cell and tissue engineering are promising, but few have made it into a clinical setting. Recombinant human bone morphogenetic protein 7 (rhBMP-7) has been shown to stimulate matrix production by IVD cells in vitro and in vivo in animal models of induced IVD degeneration. The aim of this study was to determine the most effective dose of an intradiscal injection of rhBMP-7 in a spontaneous canine IVD degeneration model for translation into clinical application for patients with low back pain.
  
  
  METHODS
  Canine nucleus pulposus cells (NPCs) were cultured with rhBMP-7 to assess the anabolic effect of rhBMP-7 in vitro, and samples were evaluated for glycosaminoglycan (GAG) and DNA content, histology, and matrix-related gene expression. Three different dosages of rhBMP-7 (2.5 μg, 25 μg, and 250 μg) were injected in vivo into early degenerated IVDs of canines, which were followed up for six months by magnetic resonance imaging (T2-weighted images, T1rho and T2 maps). Post-mortem, the effects of rhBMP-7 were determined by radiography, computed tomography, and macroscopy, and by histological, biochemical (GAG, DNA, and collagen), and biomolecular analyses of IVD tissue.
  
  
  RESULTS
  In vitro, rhBMP-7 stimulated matrix production of canine NPCs as GAG deposition was enhanced, DNA content was maintained, and gene expression levels of ACAN and COL2A1 were significantly upregulated. Despite the wide dose range of rhBMP-7 (2.5 to 250 μg) administered in vivo, no regenerative effects were observed at the IVD level. Instead, extensive extradiscal bone formation was noticed after intradiscal injection of 25 μg and 250 μg of rhBMP-7.
  
  
  CONCLUSIONS
  An intradiscal bolus injection of 2.5 μg, 25 μg, and 250 μg rhBMP-7 showed no regenerative effects in a spontaneous canine IVD degeneration model. In contrast, intradiscal injection of 250 μg rhBMP-7, and to a lesser extent 25 μg rhBMP-7, resulted in extensive extradiscal bone formation, indicating that a bolus injection of rhBMP-7 alone cannot be used for treatment of IVD degeneration in human or canine patients.
authors.affiliation: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Yalelaan 108, 3584 CM, Utrecht, The Netherlands. N.Willems@uu.nl.
authors.forename: Nicole
authors.initials: N
authors.lastname: Willems
authors.affiliation: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Yalelaan 108, 3584 CM, Utrecht, The Netherlands. F.C.Bach@uu.nl.
authors.forename: Frances C
authors.initials: FC
authors.lastname: Bach
authors.affiliation: Department of Orthopaedics, University Medical Center, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. S.G.M.Plomp@uu.nl.
authors.forename: Saskia G M
authors.initials: SG
authors.lastname: Plomp
authors.affiliation: Department of Orthopaedics, University Medical Center, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. M.Rijen@umcutrecht.nl.
authors.forename: Mattie H P
authors.initials: MH
authors.lastname: van Rijen
authors.affiliation: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Yalelaan 108, 3584 CM, Utrecht, The Netherlands. J.Wolfswinkel@uu.nl.
authors.forename: Jeannette
authors.initials: J
authors.lastname: Wolfswinkel
authors.affiliation: Department of Pathobiology, Faculty of Veterinary Medicine, Yalelaan 1, 3584 CL, Utrecht, The Netherlands. G.C.M.Grinwis@uu.nl.
authors.forename: Guy C M
authors.initials: GC
authors.lastname: Grinwis
authors.affiliation: Department of Radiotherapy, University Medical Center, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. C.Bos@umcutrecht.nl.
authors.forename: Clemens
authors.initials: C
authors.lastname: Bos
authors.affiliation: Department of Biomedical Engineering, University of Technology (TU/e), P.O. Box 513, 5600 MB, Eindhoven, The Netherlands. G.J.Strijkers@tue.nl.
authors.forename: Gustav J
authors.initials: GJ
authors.lastname: Strijkers
authors.affiliation: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Yalelaan 108, 3584 CM, Utrecht, The Netherlands. W.J.A.Dhert@uu.nl.|Department of Orthopaedics, University Medical Center, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. W.J.A.Dhert@uu.nl.
authors.forename: Wouter J A
authors.initials: WJ
authors.lastname: Dhert
authors.affiliation: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Yalelaan 108, 3584 CM, Utrecht, The Netherlands. B.P.Meij@uu.nl.
authors.forename: Björn P
authors.initials: BP
authors.lastname: Meij
authors.affiliation: Department of Orthopaedics, University Medical Center, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. L.B.Creemers@umcutrecht.nl.
authors.forename: Laura B
authors.initials: LB
authors.lastname: Creemers
authors.affiliation: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Yalelaan 108, 3584 CM, Utrecht, The Netherlands. M.A.Tryfonidou@uu.nl.
authors.forename: Marianna A
authors.initials: MA
authors.lastname: Tryfonidou
mesh_terms: D000818:Animals; D055419:Bone Morphogenetic Protein 7 / Q000008:administration & dosage*; D004195:Disease Models, Animal; D004285:Dogs; D055959:Intervertebral Disc Degeneration / Q000188:drug therapy*; D008297:Male; D010012:Osteogenesis / Q000187:drug effects*; D016133:Polymerase Chain Reaction
chemical_list: C525819:BMP7 protein, human; D055419:Bone Morphogenetic Protein 7