Histopathological characterization of spontaneously developing osteoarthropathy in the BCBC/Y mouse established newly from B6C3F1 mice.

A new breed of mouse showing cinnamon-color of hair and osteoarthropathy was born from mouse of the B6C3F1 strain, and was named the BCBC/Y mouse. The incidence and severity of the articular lesions increased with aging, and by 10 to 22 months of age, many mice showed moderate-severe motor paresis with ankylotic changes of the limb joints. Abnormal radiographic changes were observed at many joints with increasing age. There was bone and joint deformity, followed by progressive osteoarthritic changes and ankylosis of the limb joints. Histopathologically, degenerative changes, followed by loosening, fissuring and erosion of the articular cartilage were observed at early stage of articular lesions. Unilateral progressive changes, characterized by joint fusion with abnormal osteophytes, were observed at late stage of articular lesions with aging. For successive breeding to establish a homogeneous strain, generation mice retained the symptoms of the primary mice. Thus, these BCBC/Y mice may be a useful as mode to elucidate the hereditary background and hyperplastic changes of the osteochondrocytes for pathogenesis of the osteoarthropathy.