MMP and Matrix Degradation in Tendon

Tendons are often affected by chronic pain and rupture, particularly in the middle-aged and elderly, but also in the sporting and physically active younger population. Although not life threatening, these conditions (‘tendinopathy’) are major causes of morbidity, and estimated to cost tens of millions of pounds every year in lost productivity. I have previously shown that the organisation and composition of the tendon extracellular matrix (ECM) are substantially altered in tendinopathy, and that these changes may predispose to tendon pain and rupture. I have also shown that most tendinopathy is degenerative, with changes in fibroblast activity and increased ECM turnover. ECM degradation, in both normal physiology and pathology, is largely mediated by metalloproteinase enzymes: the matrix metalloproteinases (MMP) and the ‘A Disintegrin And Metalloproteinase with ThromboSpondin motifs’ (ADAMTS). I have previously shown that there are differences in MMP activity in chronic tendinopathy compared to acute tendon injuries, as well as differences in collagen turnover between tendons. Thus, although it is not known which enzymes are implicated, perturbation of the balance of metalloproteinase activities is a potential cause of tendinopathy.