Achilles tendinosis: changes in biochemical composition and collagen turnover rate.
BACKGROUND
Understanding biochemical and structural changes of the extracellular matrix in Achilles tendinosis might be important for developing mechanism-based therapies.


OBJECTIVE
In Achilles tendinosis, changes occur in biochemical composition and collagen turnover rate.


METHODS
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.


CONCLUSIONS
In Achilles tendinosis, the collagen turnover rate is increased, and the natural biochemical composition of the collagenous matrix is compromised.


CONCLUSIONS
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.
de Mos
Marieke
M
Department of Orthopaedics, Erasmus MC University Medical Center, Rotterdam, The Netherlands. m.demos@erasmusmc.nl
van El
Benno
B
DeGroot
Jeroen
J
Jahr
Holger
H
van Schie
Hans T M
HT
van Arkel
Ewoud R
ER
Tol
Hans
H
Heijboer
Rien
R
van Osch
Gerjo J V M
GJ
Verhaar
Jan A N
JA
D000125:Achilles Tendon / Q000378:metabolism* / Q000473:pathology / Q000502:physiology / Q000503:physiopathology; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D003094:Collagen / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006801:Humans; D008297:Male; D019278:Matrix Metalloproteinase 3 / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D052256:Tendinopathy / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D014867:Water / Q000032:analysis
D014867:Water; D003094:Collagen; D019278:Matrix Metalloproteinase 3