Tendinopathy is a broad term used to describe disorders in and around tendons, with absence of inflammatory cells and a poor healing response, demonstrated by collagen fibrils separated from each other lengthwise and disrupted in cross section. Tendinitis, tendinosis, and paratenonitis are all examples of tendinopathy.¹

MATRIX METALLOPROTEASES (MMPS) AND TISSUE INHIBITORS OF METALLOPROTEASES (TIMPS)

MMPs, a family of zinc and calcium dependent endopeptidases active at a neutral pH, are involved in the remodelling of extracellular matrix (ECM) through their broad proteolytic capability.² Degradation of collagen in tendon ECM is initiated by MMPs.³ Twenty three human MMPs have been identified,² with a wide range of extracellular substrates (table 1⇓).^4,5 MMPs can be subdivided into four main groups: collagenases, which cleave native collagen types I, II, and III; gelatinases, which cleave denatured collagens and type IV collagen; stromelysins, which degrade proteoglycans, fibronectin, casein, collagen types III, IV, and V; membrane-type MMPs.⁵

The activity of MMPs is inhibited reversibly by TIMPs in a non-covalent fashion in a 1:1 stoichiometry.⁵ There are four types of TIMP: TIMP1, TIMP2, TIMP3, and TIMP4.⁵ The balance between the activities of MMPs and TIMPs regulates tendon remodelling, and an imbalance produces collagen disturbances in tendons.⁶

ROLE OF MMPS AND TIMPS IN TENDINOPATHY

MMP3 may play a major role in regulation of tendon ECM degradation and tissue remodelling. An increased expression of MMP3 may be necessary for appropriate tissue remodelling and prevention of tendinopathic changes.⁷ The timing of …