Spontaneous temporomandibular joint arthropathy in MRL‐lpr/lpr mice

The temporomandibular joint (TMJ) in spontaneously arthritic MRL lpr/lpr (MRL/l) mice has been histologically analysed. After decalcification and standardized preparation of the joint tissue, histological sections were examined for presence of synovial hypertrophy, synovial villi, pannus tissue, erosions, cysts and signs of periarticular inflammation. In 12 of 13 TMJs examined, histopathological changes indicating a state of arthropathy were found. The most prevalent finding was synovial proliferation, which was frequently detected at the insertion of the synovial membrane to the bone. Two or more signs of inflammatory involvement including synovial proliferation, pannus tissue and bone erosion were seen in 5 mice with a predominance among the oldest mice (greater than or equal to 5 months of age). No lymphocytic cell infiltration was found in the analyzed synovial tissues of the TMJ. In contrast, lymphocytes were observed in the vicinity of periarticular blood vessels and tendons. It is concluded that the TMJ is frequently involved in the arthritic disease of autoimmune MRL/l mice.