Differences in tumor necrosis factor (TNF)alpha and TNF receptor-1-mediated intracellular signaling factors in normal, inflamed and scar-formed horse tendons

J Vet Med Sci. 2005 Oct;67(10):985-91. doi: 10.1292/jvms.67.985.


Tumor necrosis factor (TNF) receptors (TNF-R)-mediated cell survival or apoptosis has been demonstrated in many cells, but little is known about survival or apoptotic signals via TNF-R1 in tendinocytes. In this study, we focused on four signaling factors, TNFalpha, TNF-R1, TNFR-associated factor2 (TRAF2) and caspase-3, in order to elucidate the signaling events in tendinocytes. Samples were obtained from normal, inflamed and scar-formed equine superficial digital flexor tendons. To detect these signaling factors, samples were subjected to immunohistochemistry and Western blot analysis, and some samples were also subjected to reverse transcription-polymerase chain reaction (RT-PCR), PCR-Southern blot analysis and in situ hybridization to detect the expression of TNFalpha mRNA. Distribution of the four factors differed depending on the tendon condition, normal, inflamed or scar-formed. In the normal tendon, large amounts of TRAF2 were found in tendinocytes, but the amounts of TNF-R1 were small. TNFalpha mRNA was expressed most highly in the inflamed tendon. TNF-R1, which was only faintly detected in the normal tendon, was detected at a high level in the inflamed tendon, and the amounts of TRAF2 and caspase-3 also increased. Activated caspase-3 was only detected in the inflamed tendon. TNFalpha mRNA was also expressed in the scar-formed tendon, though it showed weak signals, and the expression levels of TNF-R1, TRAF2 and caspase-3 proteins were very low. Two distinct intracellular signaling pathways of TNFalpha, which lead to cell survival and apoptosis, might be present in tendinocytes mediated through TNF-R1. These results, which reflect the dynamism of TNFalpha, provide important clues for means to prevent tendinopathy.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Southern / veterinary
  • Blotting, Western / veterinary
  • Caspase 3
  • Caspases / metabolism
  • DNA Primers
  • Horse Diseases / metabolism*
  • Horse Diseases / pathology
  • Horses
  • Immunohistochemistry / veterinary
  • In Situ Hybridization / veterinary
  • Inflammation / metabolism
  • Inflammation / pathology
  • Inflammation / veterinary*
  • Receptors, Tumor Necrosis Factor, Type I / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction / veterinary
  • Signal Transduction / physiology*
  • TNF Receptor-Associated Factor 2 / metabolism
  • Tendons / metabolism*
  • Tendons / pathology
  • Tumor Necrosis Factor-alpha / metabolism*


  • DNA Primers
  • Receptors, Tumor Necrosis Factor, Type I
  • TNF Receptor-Associated Factor 2
  • Tumor Necrosis Factor-alpha
  • Caspase 3
  • Caspases