Tendon integrity depends on the extracellular matrix (ECM) metabolism which is regulated by proteolytic enzymes. However,
it is unclear which enzymes play a role in tendon rupture. We studied the ECM of 19 ruptured human Achilles tendons, comparing
the composition of specimens harvested close to the rupture with specimens harvested from an apparently healthy area in the
same tendon. We compared gene expression of collagen Type I, decorin, and versican including enzymes involved in their metabolism
as matrix metalloproteases (MMP-2 and -9) and tissue inhibitory of metalloproteinase (TIMP-1 and -2) using real-time PCR,
zymography and FACE analysis. We found greater gene expression of proteoglycan core protein decorin and versican, collagen
Type I, MMPs and TIMPs in the tendon rupture. Zymography analysis, reflecting expression of enzymatic activity, confirmed
the gene expression data at protein level. Carbohydrate content was greater in the macroscopically healthy area than in the
ruptured area. In the ruptured area, we found increased core protein synthesis but without the normal glycosaminoglycan production.
The tissue in the area of rupture undergoes marked rearrangement at molecular levels and supports the role of MMPs in the
pathology.
Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest,
patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
Each author certifies that his or her institution has approved the reporting of these cases, that all investigations were
conducted in conformity with ethical principles of research, and that informed consent for participation in the study was
obtained.