Expression of type X collagen in young and old C57Bl/6 and Balb/c mice. Relation with articular cartilage degeneration

Objective: To investigate whether the development of osteoarthritic lesions in the knee joints of mice is associated with increased immunostaining of type X collagen. Methods: Sections of total knee joints in combination with immunohistochemi stry were used to study the distribution of type X collagen in the cartilag e of young and old mice of two mouse strains, Balb/c and C57Bl/6, known to develop osteoarthritic lesions at different locations. Expression of type X collagen and PTH/PTHrP-receptor mRNA were studied by RT-PCR. Results: Young adult Balb/c and C57Bl/6 mice both expressed type X collagen in the non-calcified cartilage of the tibia-femoral joint. Old mice of bot h strains had a strongly increased deposition of type X collagen in the pat ella-femoral but not in the tibia-femoral joint. The locations in the murin e knee joints prone to develop osteoarthritis (OA) did not preferentially e xpress increased amounts of type X collagen. Thus, whereas increased type X was observed in both strains in the patella-femoral joints, only Balb/c mi ce preferentially developed osteoarthritic lesions in these joints. Also ca rtilage degeneration was usually seen only in the lateral compartment of th e knee joints of C57Bl/6 mice but this was not accompanied by increased typ e X collagen immunostaining. Increased deposition of type X collagen was no t associated with elevated levels of type X collagen mRNA or with decreased levels of PTH/PTHrP-receptor mRNA. Conclusion: Type X collagen expression and spontaneous OA in mice are not n ecessarily related since OA prone locations in the murine knee joint do not preferentially express type X collagen. (C) 2001 OsteoArthritis Research S ociety International.