HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 107/2/399    most recent 91563.2008v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Eliasson, P. Articles by Aspenberg, P. PubMed PubMed Citation Articles by Eliasson, P. Articles by Aspenberg, P.

Rat Achilles tendon healing: mechanical loading and gene expression

Linkoping University, Orthopedics, AIM/IKE, Faculty of Health Sciences, Linkoping, Sweden

Submitted 3 December 2008 ; accepted in final form 16 June 2009

Injured tendons require mechanical tension for optimal healing, but it is unclear which genes are upregulated and responsible for this effect. We unloaded one Achilles tendon in rats by Botox injections in the calf muscles. The tendon was then transected and left to heal. We studied mechanical properties of the tendon calluses, as well as mRNA expression, and compared them with loaded controls. Tendon calluses were studied 3, 8, 14, and 21 days after transection. Intact tendons were studied similarly for comparison. Altogether 110 rats were used. The genes were chosen for proteins marking inflammation, growth, extracellular matrix, and tendon specificity. In intact tendons, procollagen III and tenascin-C were more expressed in loaded than unloaded tendons, but none of the other genes was affected. In healing tendons, loading status had small effects on the selected genes. However, TNF- transforming growth factor-β1, and procollagens I and III were less expressed in loaded callus tissue at day 3. At day 8 procollagens I and III, lysyl oxidase, and scleraxis had a lower expression in loaded calluses. However, by days 14 and 21, procollagen I, cartilage oligomeric matrix protein, tenascin-C, tenomodulin, and scleraxis were all more expressed in loaded calluses. In healing tendons, the transverse area was larger in loaded samples, but material properties were unaffected, or even impaired. Thus mechanical loading is important for growth of the callus but not its mechanical quality. The main effect of loading during healing might thereby be sought among growth stimulators. In the late phase of healing, tendon-specific genes (scleraxis and tenomodulin) were upregulated with loading, and the healing tissue might to some extent represent a regenerate rather than a scar.

unloading; tendon healing; inflammation; extracellular matrix; mechanobiology