Further characterization of spontaneous arthritic changes in murine squamo-mandibular joint: histopathological aspects.

The appearance of age-related ulcerative changes in the mouse mandibular condyle were evaluated by light and electron microscopy examinations. Fibrillations appeared along the articular surface and in deeper tissue regions, as early as at six months of age. Such changes were characterized by a marked loss of the tissue's cellularity and by a marked reduction in matrix metachromasia and safranin-0 staining. These microscopical changes were accompanied by a reduced reactivity for both ruthenium red and colloidal iron binding, as noted ultrastructurally. At the same time, increasing numbers of erythrocytes appeared to be adhered to the surface irregularities and were also found in deeper regions within the articular lesions. Using morphological criteria, it became apparent that the degenerative changes of aging articular cartilage started at the more superficial regions of the tissue and only thereafter proceeded toward the chondro-osseous junction. Also, with the advancement of age, the degenerative changes became more severe.