Osteoarthritic lesions in temporo-mandibular joints of STR/ort mice

Methods: Articular cartilage of STR/ort and control mice (C57BL/6) was examined. Bone mass density (BMD) was evaluated using the LE Lunar Piximus II dual-energy X-ray machine. Alizarin red/alcian blue and safranin-O staining were used to assess the morphologic and histological changes of the articular cartilage as well as its sulphated proteoglycans content. Immunohistochemical staining was carried out using specific antibodies to IL1-β, endothelin (ET-1), bradykinin receptor (B1R), and Reg I proteins.

Results: An increase in BMD was noted in STR/ort TMJ and knee condyles. Morphological changes and structural alterations were observed in the articular cartilage after the age of 36 weeks. A histological loss of proteoglycans with age was also observed mainly in STR/ort males. These degenerative changes were associated with an over-expression of IL1-β, ET-1, Reg I and B1R proteins.

Conclusion: The STR/ort mouse strain appears to develop OA-like lesions in the TMJ with age, especially in males, and this is associated with an over-expression of pro-inflammatory mediators, namely IL1-β, ET-1, B1R and Reg I. These mediators may therefore play a significant role in the initiation and exacerbation of TMJ OA. This in vivo experimental animal model appears to be a promising research tool for a better understanding of the pathogenic mechanisms involved in OA of the TMJ.