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Tenocyte hypercellularity and vascular proliferation in a rabbit model of tendinopathy: contralateral effects suggest the involvement of central neuronal mechanisms
  1. Gustav Andersson1,
  2. Sture Forsgren1,
  3. Alexander Scott2,3,
  4. James Edmund Gaida1,4,5,
  5. Johanna Elgestad Stjernfeldt1,
  6. Ronny Lorentzon5,
  7. Håkan Alfredson5,
  8. Clas Backman6,
  9. Patrik Danielson1
  1. 1Department of Integrative Medical Biology, Anatomy, Umeå University, Umeå, Sweden
  2. 2Centre for Hip Health and Mobility, Vancouver Coastal Health and Research Institute, Vancouver, British Columbia, Canada
  3. 3Department of Physical Therapy, University of British Columbia, Vancouver, British Columbia, Canada
  4. 4School of Exercise and Nutrition Sciences, Deakin University, Burwood, Australia
  5. 5Department of Surgical and Perioperative Sciences, Sports Medicine, Umeå University, Umeå, Sweden
  6. 6Department of Surgical and Perioperative Sciences, Hand Surgery, Umeå University, Umeå, Sweden
  1. Correspondence to Dr Patrik Danielson, Department of Integrative Medical Biology, Anatomy, Umeå University, SE-901 87 Umeå, Sweden; patrik.danielson{at}


Objective To determine whether there are objective findings of tendinosis in a rabbit tendinopathy model on exercised and contralateral (non-exercised) Achilles tendons.

Design Four groups of six New Zealand white rabbits per group were used. The animals of one (control) group were not subjected to exercise/stimulation.

Interventions Animals were subjected to a protocol of electrical stimulation and passive flexion–extension of the right triceps surae muscle every second day for 1, 3 or 6 weeks.

Main Outcome Measures Tenocyte number and vascular density were calculated. Morphological evaluations were also performed as well as in-situ hybridisation for vascular endothelial growth factor (VEGF) messenger RNA.

Results There was a significant increase in the tenocyte number after 3 and 6 weeks of exercise, but not after 1 week, in comparison with the control group. This was seen in the Achilles tendons of both legs in experimental animals, including the unexercised limb. The pattern of vascularity showed an increase in the number of tendon blood vessels in rabbits that had exercised for 3 weeks or more, compared with those who had exercised for 1 week or not at all. VEGF-mRNA was detected in the investigated tissue, with the reactions being more clearly detected in the tendon tissue with tendinosis-like changes (6-week rabbits) than in the normal tendon tissue (control rabbits).

Conclusions There were bilateral tendinosis-like changes in the Achilles tendons of rabbits in the current model after 3 weeks of training, suggesting that central neuronal mechanisms may be involved and that the contralateral side is not appropriate as a control.

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  • Funding Financial support was obtained from the Faculty of Medicine at Umeå University (SF, PD), the Sigurd and Elsa Golje Memorial Foundation (PD), the Tore Nilsson Foundation for Medical Research (PD) and the JC Kempe and Seth M Kempe Memorial Foundations, Örnsköldsvik (SF, HA). AS was supported by a travel grant from the Canada–Scandinavia Foundation, as well as a CIHR postdoctoral fellowship. JEG was supported by the Felice Rosemary-Lloyd travel scholarship.

  • Competing interests None.

  • Ethics approval Experiments were approved by the local ethical committee for research on animals.

  • Provenance and peer review Not commissioned; externally peer reviewed.