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Tissue memory in healing tendons: short loading episodes stimulate healing
Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Orthopaedic Centre, Department of Orthopaedics Linköping.
2009 (English)In: JOURNAL OF APPLIED PHYSIOLOGY, ISSN 8750-7587, Vol. 107, no 2, 417-421 p.Article in journal (Refereed) Published
Abstract [en]

Intact tendons adapt slowly to changes in mechanical loading, whereas in healing tendons the effect of mechanical loading or its absence is dramatic. The longevity of the response to a single loading episode is, however, unknown. We hypothesized that the tissue has a "memory" of loading episodes and that therefore short loadings are sufficient to elicit improved healing. The Achilles tendon of 70 female rats was transected and unloaded by tail suspension for 12 days (suspension started on day 2 after surgery). Each day, the rats were let down from suspension for short daily training episodes according to different regimes: 15 min of cage activity or treadmill running for 15, 30, 60, or 2 x 15 min. Rats with transected Achilles tendons and full-time cage activity served as controls. The results demonstrated that full-time cage activity increased the peak force over three times compared with unloading. Short daily loading episodes (treadmill running) increased the peak force about half as much as full-time activity. Prolongation of treadmill running above 15 min or dividing the daily training in two separate episodes had minimal further effect. This mechanical stimulation increased the cross-sectional area but had no effect on the mechanical properties of the repair tissue. The findings indicate that once the tissue had received information from a certain loading type and level, this is "memorized" and leads to a response lasting many hours. This suggests that patients might be allowed early short loading episodes following, e. g., an Achilles tendon rupture for a better outcome.

Place, publisher, year, edition, pages
2009. Vol. 107, no 2, 417-421 p.
Keyword [en]
hindlimb suspension, immobilization, Achilles tendon, tendon healing, mechanical stimulation
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-19914DOI: 10.1152/japplphysiol.00414.2009OAI: oai:DiVA.org:liu-19914DiVA: diva2:231643
Available from: 2009-08-14 Created: 2009-08-14 Last updated: 2012-03-27
In thesis
1. Response to mechanical loading in healing tendons
Open this publication in new window or tab >>Response to mechanical loading in healing tendons
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ruptured tendons heal faster if they are exposed to mechanical loading. Loading creates deformation of the extracellular matrix and cells, which give rise to intracellular signalling, increased gene expression and protein synthesis. The effects of loading have been extensively studied in vitro, and in intact tendons in vivo. However, the response to loading in healing tendons is less known.

The general aim of this thesis was to understand more about the response to mechanical loading during tendon healing. The specific aims were to find out how short daily loading episodes could influence tendon healing, and to understand more about genes involved in tendon healing.

The studies were performed using rat models. Unloading of healing tendons resulted in a weaker callus tissue. This could be reversed to some extent by short daily loading episodes. Loading induced more matrix production, making the tendons thicker and stronger, but there was no improvement in the material properties of the matrix. Lengthening is one potential adversity with early loading, during tendon healing in patients. This was also seen with continuous loading in the rat models. However, short loading episodes did not result in any lengthening, not even when loading was applied during the inflammatory phase of healing. It also appeared as loading once daily was enough to make healing tendons stronger, while loading twice daily with 8 hours interval did not give any additional effect. The strongest gene expression response to one loading episode was seen after 3 hours. The gene expression changes persisted 12 hours after the loading episode but had disappeared by 24 hours. Loading appeared to regulate genes involved in inflammation, wound healing and coagulation, angiogenesis, and production of reactive oxygen species. Inflammation-associated genes were regulated both by continuous loading and by one short loading episode. Inflammation is an important part of the healing response, but too much can be harmful. Loading might therefore have a role in fine-tuning the inflammatory response during healing.

In conclusion, these studies show that short daily loading episodes during early tendon healing could potentially be beneficial for rehabilitation. Loading might have a role in regulating the inflammatory response during healing.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 86 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1247
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-70774 (URN)978-91-7393-166-3 (ISBN)
Public defence
2011-09-09, Nils-Holger salen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2011-09-16 Created: 2011-09-16 Last updated: 2012-03-27Bibliographically approved

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Andersson, ThereseEliasson, PernillaAspenberg, Per

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