A Longitudinal Analysis of Urinary Biochemical Markers and Bone Mineral Density in STR/Ort Mice as a Model of Spontaneous Osteoarthritis

Objective. To investigate the longitudinal changes both in the urinary concentrations of biochemical markers and in bone mineral density (BMD) during disease progression in the STR/Ort mouse model of osteoarthritis (OA). Methods. Male STR/Ort mice were studied, with CBA mice used as nonarthritic controls. Radiographic evaluation and grading of the knee and measurements of urinary C-terminal crosslinking telopeptide of type II collagen (CTX-II), pyridinoline (Pyr), and deoxypyridinoline were performed between 8 weeks and 40 weeks of age. The BMD of the femoral shaft was measured from 20 weeks to 40 weeks of age and adjusted for body weight. Histologic evaluation and grading were performed at 40 weeks of age. STR/Ort mice were divided into 2 subgroups (STR OA and STR non-OA) based on histologic grading. Results. No significant differences between STR/Ort and CBA mice were observed for any biochemical marker or BMD at any time point. Urinary CTX-II levels and BMD in the STR OA subgroup were higher than those in the STR non-OA subgroup before radiographic changes of OA were apparent. Higher urinary Pyr levels in the STR OA subgroup were observed at the advanced stage of OA. Conclusion. Urinary CTX-II could be a useful marker in the early diagnosis and predicting the progression of OA, and urinary Pyr may be a potential marker to assess the severity of OA at an advanced stage. An increase in BMD prior to the establishment of radiographic OA may be related to the induction of OA.