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Achilles tendinosis: Changes in biochemical composition and collagen turnover rate

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Author: Mos, M. de · El, B. van · Groot, J. de · Jahr, H. · Schie, H.T.M. van · Arkel, E.R. van · Tol, H. · Heijboer, R. · Osch, G.J.V.M. van · Verhaar, J.A.N.
Institution: TNO Kwaliteit van Leven
Source:American Journal of Sports Medicine, 9, 35, 1549-1556
Identifier: 240176
doi: doi:10.1177/0363546507301885
Keywords: Biology · Biomedical Research · Achilles tendon · Collagen · Crosslinks · Matrix metalloproteinase · Pentosidine · Tendinopathy · Tendinosis · collagen · collagen type 1 · collagen type 2 · lysine · matrix metalloproteinase · pentosidine · achilles tendinitis · article · biochemical composition · biopsy · clinical article · controlled study · cross linking · enzyme activity · gene expression · genetic analysis · human · human tissue · hydroxylation · laboratory test · nucleotide sequence · priority journal · turnover time · upregulation · water content · Achilles Tendon · Adult · Aged · Biomechanics · Collagen · Female · Gene Expression · Humans · Male · Matrix Metalloproteinase 3 · Middle Aged · Tendinopathy · Water


Background: Understanding biochemical and structural changes of the extracellular matrix in Achilles tendinosis might be important for developing mechanism-based therapies. Hypothesis: In Achilles tendinosis, changes occur in biochemical composition and collagen turnover rate. Study Design: Descriptive laboratory study. Methods: From 10 patients undergoing surgery for Achilles tendinopathy, 1 tendinosis biopsy specimen and 1 biopsy specimen of macroscopically healthy tendon tissue adjacent to the lesion were collected. Furthermore, biopsy samples were collected from 3 donors with asymptomatic Achilles tendons. Water content, collagen content, percentage of denatured collagen, amount of lysine hydroxylation, number of enzymatic and nonenzymatic crosslinks, matrix metalloproteinase activity, and matrix metalloproteinase and collagen gene-expression levels were analyzed. Results: In tendinotic lesions, the water content was highest, and collagen content was subnormal with higher amounts of denatured/damaged collagen. Low pentosidine levels in tendinotic tissue indicated the presence of relatively young collagenous matrix. More hydroxylated lysine residues were present in tendinotic samples, but enzymatic crosslinks revealed no differences between tendinotic, adjacent, and healthy samples. In tendinotic specimens, matrix metalloproteinase activity was higher, matrix metalloproteinase gene-expression profile was altered, and collagen type I and III gene expression were upregulated. Conclusion: In Achilles tendinosis, the collagen turnover rate is increased, and the natural biochemical composition of the collagenous matrix is compromised. Clinical Relevance: Although tendon tissue directly adjacent to an Achilles tendinosis lesion looks macroscopically healthy, histological and biochemical degenerative changes in adjacent tissue are evident, which may have implications for surgical interventions. © 2007 American Orthopaedic Society for Sports Medicine.