A correlation between knee cartilage degradation observed by arthroscopy and synovial proteinases activities

Objective A novel study has been carried out to characterize the amount and activity levels of metalloproteinases (i.e., MMP-1, MMP-2, MMP-3, MMP-8, MMP-9 and MMP-13) and of their inhibitors (i.e., TIMP-1 and TIMP-2) in synovial fluid from patients (n = 56) with different degrees of either chondral lesions or knee arthritis identified and classified by arthroscopy. Design and methods Zymographies, Western blotting and ELISA tests have been used to correlate the disease stage, as determined by arthroscopy, and both the amount and the activation state of different MMPs and of their inhibitors. Results Analysis of data obtained demonstrates that the degree of cartilage degradation, as seen by arthroscopy, is strictly related to the activity of some synovial MMPs, in particular MMP-2 and MMP-13 and on reduced inhibitory effect of MMP-2 by TIMP-2; in addition, a serine protease weighing about 125 kDa appears only in patients with severe cartilage degradation, i.e., with knee arthritis. Conclusions On the whole, this is the first study in which an analysis of synovial MMPs/other proteinases activity and TIMPs has been strictly related to arthroscopy results in patients with different degrees of osteoarthritis. Results indicate that an imbalance between specific MMP activities and the amount of TIMPs and of its inhibitory efficiency is crucial for the disease evolution and it is related to the disease stage.