Cell and Tissue Research

, Volume 342, Issue 3, pp 363–376 | Cite as

Remodeling of the notochord during development of vertebral fusions in Atlantic salmon (Salmo salar)

  • Elisabeth Ytteborg
  • Jacob Seilø Torgersen
  • Mona E. Pedersen
  • Grete Baeverfjord
  • Kirsten O. Hannesson
  • Harald Takle
Regular Article


Histological characterization of spinal fusions in Atlantic salmon (Salmo salar) has demonstrated shape alterations of vertebral body endplates, a reduced intervertebral space, and replacement of intervertebral cells by ectopic bone. However, the significance of the notochord during the fusion process has not been addressed. We have therefore investigated structural and cellular events in the notochord during the development of vertebral fusions. In order to induce vertebral fusions, Atlantic salmon were exposed to elevated temperatures from fertilization until they attained a size of 15 g. Based on results from radiography, intermediate and terminal stages of the fusion process were investigated by immunohistochemistry and real-time quantitative polymerase chain reaction. Examination of structural extracellular matrix proteins such as Perlecan, Aggrecan, Elastin, and Laminin revealed reduced activity and reorganization at early stages in the pathology. Staining for elastic fibers visualized a thinner elastic membrane surrounding the notochord of developing fusions, and immunohistochemistry for Perlecan showed that the notochordal sheath was stretched during fusion. These findings in the outer notochord correlated with the loss of Aggrecan- and Substance-P-positive signals and the further loss of vacuoles from the chordocytes in the central notochord. At more progressed stages of fusion, chordocytes condensed, and the expression of Aggrecan and Substance P reappeared. The hyperdense regions seem to be of importance for the formation of notochordal tissue into bone. Thus, the remodeling of notochord integrity by reduced elasticity, structural alterations, and cellular changes is probably involved in the development of vertebral fusions.


Notochord Perlecan Spinal fusions Substance P Atlantic salmon Salmo salar (Teleostei) 



Anulus fibrosus


Base pair


Collagen type 2




Elongation factor 1


Glomerular kidney membrane


Intervertebral disc degeneration


Intervertebral disk


Phosphate-buffered saline




Quantitative polymerase chain reaction


Reverse transcription


Runt-related transcription factor 2


(Sex determining region Y) box 9


Substance P


Zebrafish neuron marker 12

Supplementary material

441_2010_1069_MOESM1_ESM.jpg (5.8 mb)
Fig. S1 Western blot of (a) Zn12 (standard in lane 1 Novex Sharp Pre-Stained Protein Standards, Invitrogen), (b) Aggrecan, and (c) Perlecan. (JPEG 5925 kb)


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Elisabeth Ytteborg
    • 1
    • 5
  • Jacob Seilø Torgersen
    • 1
  • Mona E. Pedersen
    • 2
  • Grete Baeverfjord
    • 3
  • Kirsten O. Hannesson
    • 2
  • Harald Takle
    • 1
    • 4
  1. 1.Nofima Marine AS, Fisheries and Aquaculture ResearchNorwegian Institute of FoodAasNorway
  2. 2.Nofima Food ASAasNorway
  3. 3.Nofima Marine ASSunndalsøraNorway
  4. 4.AVS ChilePuerto VarasChile
  5. 5.Department of Animal and Aquaculture SciencesNorwegian University of Life SciencesAasNorway

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