Objective: To describe the spontaneous evolution of age-related changes affecting knee joint articular cartilage, walking speed and a serum biomarker of cartilage remodeling in C57BL/6-JRj wild-type male mice.
Design: Histological changes were assessed by the Osteoarthritis Research Society International (OARSI) score (0=normal, 6=vertical clefts/erosion to the calcified cartilage extending >75% of the articular surface) in newborn, 1-week- and 1-, 3-, 6-, 9- and 12-month-old C57BL/6-JRj wild-type male mice, walking speed by the Locotronic system, and serum C-terminal telopeptide of type II collagen (CTX-II) content by ELISA in 1-, 3-, 6-, and 9-month-old C57BL/6-JRj wild-type male mice.
Results: Mean (SD) OARSI score significantly increased from 0.2 (0.3) to 1.3 (0.6) (p=0.03) between 1 and 3 months of age and from 1.3 (0.6) to 3.3 (0.6) (p=0.04) between 3 and 6 months of age. Mean walking speed was stable between 1 and 6 months of age but significantly decreased from 11.4 (1.8) to 3.2 (0.8) cm.s-1 (p=0.03) between 6 and 9 months of age. Serum CTX-II content was maximal at 1 month of age, then decreased from 12.2 (8.5) to 2.4 (8.4) pg/ml (p=0.02) between 1 and 3 months of age, remaining low and stable thereafter.
Conclusions: C57BL/6-JRj wild-type male mice showed continuously increasing osteoarthritic changes but delayed decreasing walking speed with age. These variations were maximal between 3 and 9 months of age. Maximal serum CTX-II content preceded these changes.
Keywords: age-related changes; mouse model; osteoarthritis.