BACKGROUND AIMS: Cartilage defects are considered to be an initial event in the progress of osteoarthritis. Reliable data about in vivo regulation of cytokines in natural and surgically induced cartilage repair are still missing.
METHODS: Knee lavage fluids of 47 patients were collected prospectively between August 2006 and September 2007. Five patients without cartilage lesions served as a control group. In 42 patients the cartilage defects were treated by microfracturing (19) or autologous chondrocyte implantation (ACI) (23). Total protein content and concentrations of aggrecan, basic fibroblast growth factor (bFGF), Insulin-like growth factor and interleukin (IL)-1beta were determined. Clinical status was evaluated using the Lysholm score.
RESULTS: High-level expression in all knees was found for aggrecan, low-level constitutive expression for bFGF and IGF-I, while concentrations of IL-1beta in the control group remained below detection levels. The concentration of IGF-I in the knees with cartilage lesions was significantly higher (P<0.05) than in the control group. bFGF concentrations depended on cartilage lesion size; levels in the knees of patients undergoing ACI (6.1 cm(2)), were significantly higher compared with the control group (P<0.05) and the group of patients undergoing microfracturing (3.4 cm(2), P<0.001). Levels of aggrecan did not change after surgical cartilage repair, whereas concentrations of bFGF, IL-1beta and IGF-I significantly increased (P<0.01). Levels of IL-1beta significantly correlated with systemic C-reactive protein (CRP). The Lysholm score showed a medium significant negative correlation with IGF-I levels.
CONCLUSIONS: Aggrecan is constitutively expressed in knee joints. bFGF and IGF-I seem to play a pivotal role in natural and surgical cartilage repair. Operative intervention is additionally associated with IL-1beta-related inflammation-like reactions.