Evaluation of the effect of oxidative stress on articular cartilage in spontaneously osteoarthritic STR/OrtCrlj mice by measuring the biomarkers for oxidative stress and type II collagen degradation/synthesis.

To investigate the involvement of oxidative stress in the pathogenesis of osteoarthritis (OA), we evaluated the relationship between oxidative stress and articular cartilage degradation by measuring the serum levels of malondialdehyde (MDA, an oxidative stress marker), CTX-II (a type II collagen degradation marker) and CPII (a type II collagen synthesis marker) in obese and hyperlipidemic STR/Ort (STR) and control CBA mice. Seven-week-old osteoarthritic STR male mice (n=10) and control CBA male mice (n=10) were fed standard laboratory food ad libitum. At 35 weeks of age, the mice were sacrificed, and the serum levels of MDA, CTX-II and CPII were determined. Furthermore, histopathological changes were evaluated in the knee joints. Most of the STR mice spontaneously developed OA (18 of the 20 knees). By contrast, the CBA mice developed OA in only 4 of the 20 knees. Importantly, the serum levels of MDA, CTX-II and CPII were elevated to a greater extent in the STR mice compared to levels in the CBA mice. Notably, the level of MDA was correlated with that of CTX-II, but not of CPII. Moreover, the MDA levels were significantly correlated with the serum lipid (total cholesterol and triglyceride) levels as well as body weight. Together these observations suggest that oxidative stress is likely involved in the degradation of type II collagen in articular cartilage, thereby possibly contributing to the development of OA in obese and hyperlipidemic STR mice.