M. Maiotti et al., Correlation between osteoarthritic cartilage damage and levels of proteinases and proteinase inhibitors in synovial fluid from the knee joint, ARTHROSCOPY, 16(5), 2000, pp. 522-526
Matrix metalloproteinases (MMPs) in the synovial fluid are responsible for
collagen breakdown during physiologic cartilage turnover and the pathologic
destruction of the cartilage. We measured the levels of MMPs, specific tis
sue inhibitors of metalloproteinases (TIMPs), and interleukin-6 (IL-6) in s
ynovial fluid from the knees of 36 patients with cartilage lesions subdivid
ed according to severity based on arthroscopic findings. Lesions were class
ified as mild(group 1, edema with no disruption of the surface), moderate (
group 2, open lesions without exposure of subchondral bone), or severe (gro
up 3, exposure of subchondral bone). Zymography (gel electrophoresis in the
presence of hydrolizable substrates) showed a 60-kd band in all samples. A
second band (94-kd) was found exclusively in specimens from groups 2 and 3
, and a third band (110-kd) was present only in group 3. Concentrations of
2 of the most important modulators of MMP activity, TIMP-1 and IL-6, were m
easured. TIMP-1 levels did not vary significantly with the severity of cart
ilage damage. Linear regression analysis revealed a significant positive co
rrelation between TIMP-1 and IL-6 in groups 1 and 3. These data indicate th
at the severity of the cartilage damage corresponds with MMP activity. The
correlation between IL-6 and TIMP-1 in groups with mild and moderate damage
suggests a regulating mechanism that is absent in severe lesions.