Document Detail

Tendinosis-like histologic and molecular changes of the Achilles tendon to repetitive stress: a pilot study in rats.
MedLine Citation:
PMID:  21800208     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Tendinopathy (pain and tendon degeneration) is associated with repetitive use and mechanical overload. However, the etiology of tendinopathy remains unclear. Clarification of histologic and molecular changes of tendon to repetitive stress could provide better understanding of Achilles tendon disorders related to repetitive stress.
QUESTIONS/PURPOSES: We asked whether repetitive stress simulating overuse of the Achilles tendon induced (1) histologic changes in rats similar to tendinosis (increased cellularity of fibrocytes, increased disorganization of collagen fiber, and increased roundness of the nucleus of the fibrocyte), (2) increased collagen Type III occurrence, and (3) increased inducible nitric oxide synthase (iNOS) expression.
METHODS: We used an exercise protocol simulating repetitive, jerky, eccentric contraction of the triceps surae in 15 rats. We conducted the exercise for 2 hours per day, three times per week using the right rear legs only and the left legs as internal controls. We harvested Achilles tendons after either 2, 4, or 6 weeks of exercise, and evaluated changes in tendon thickness, fibrocyte count, collagen fiber arrangement, collagen fiber type, and occurrence of iNOS.
RESULTS: Exercised Achilles tendons showed increased cellularity of fibrocytes at 4 and 6 weeks of exercise, and disorganized collagen fiber arrangement at 6 weeks of exercise. There was a trend for Type III collagen occurrence being greater in experimental groups. Expression of iNOS increased after 2 and 4 weeks of exercise when compared with that of the controls, but decreased after 6 weeks.
CONCLUSIONS: These observations suggest repetitive, synchronized, passive, and jerky exercise induced by electrical stimulation can lead to the tendinosis-like changes in the Achilles tendons in rats with imbalance between synthesis and degeneration after 4 weeks of exercise.
CLINICAL RELEVANCE: This newly designed exercise protocol may be used to design an animal model of Achilles tendon overuse. With this model, therapeutic interventions of tendinopathy could be analyzed by investigation of tendon biology and response in terms of histologic and molecular changes.
Nam Soon Cho; Ji Hye Hwang; Yong Taek Lee; Seoung Wan Chae
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2011-07-29
Journal Detail:
Title:  Clinical orthopaedics and related research     Volume:  469     ISSN:  1528-1132     ISO Abbreviation:  Clin. Orthop. Relat. Res.     Publication Date:  2011 Nov 
Date Detail:
Created Date:  2011-09-30     Completed Date:  2011-11-30     Revised Date:  2013-06-28    
Medline Journal Info:
Nlm Unique ID:  0075674     Medline TA:  Clin Orthop Relat Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3172-80     Citation Subset:  AIM; IM    
Department of Physical Medicine and Rehabilitation, Korea University Ansan Hospital, Korea University College of Medicine, Gyeonggi-do, Korea.
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MeSH Terms
Achilles Tendon / metabolism,  pathology*
Biological Markers / metabolism
Cell Nucleus / pathology
Collagen Type III / metabolism
Cumulative Trauma Disorders / metabolism,  pathology*
Disease Models, Animal
Electric Stimulation
Fibroblasts / metabolism,  pathology
Muscle Contraction
Nitric Oxide Synthase Type II / biosynthesis
Physical Conditioning, Animal
Pilot Projects
Rats, Sprague-Dawley
Stress, Mechanical
Tendinopathy / metabolism,  pathology*
Reg. No./Substance:
0/Biological Markers; 0/Collagen Type III; EC Oxide Synthase Type II; EC protein, rat

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