Immunohitochemical localization of matrix metalloproteinase-12 [macrophage elastase] in rabbit mandibular condyle following experimental induction of anterior disc displacement

ABSTRACT

The purpose of the present study was to investigate the immunohistochemical distribution of matrix metalloproteinase-12 [MMP-12] in the rabbit mandibular condyle following experimental induction of anterior disc displacement. The right temporomandibular Joint [TMJ] of nine rabbits was exposed surgically and all discal attachments were severed except for the posterior attachment. The disc was then repositioned anteriorly. The left TMJ served as a control. Mandibular condyles were excised at 2, 4 and 7 weeks following surgery. These specimens were prepared and stained by Haematoxyline and eosin [H and E] for routine histological examination. For immunohistochemical staining with MMP-12, five micron thick sections were cut and mounted on positively charged slides. After two weeks the current study revealed the presence of numerous intense immunoreactivities at the bone cartilage interface. Some of the chondrocytes showed intense granuliform reactivity for MMP-12. The subchondral bone showed also intense immunoreactivities surrounding both Haversian and Volkmann canals as well as along the entire borders of large resorbed bone marrow spaces. These immunohistochemical results concomitant with the breakdown of the articular cartilage and degradation of the extracellular matrix as well as splitting phenomena at the bone cartilage interface observed histologically during this period. After four weeks, the articular cartilage was lost and the mandibular condyle showed formation of coarse fibered woven bone. The immunohistochemical staining for MMP-12 was relatively weak at the surface of the woven bone and appeared to be moderate in the deep layer. After seven weeks, the mandibular condyle showed irregular remodeling of bone with negligiable immunoreactivity in the remodeled bone trabeculae. On the other hand, in the control group the MMP-12 was relatively weak at the surface of the woven bone and appeared to be moderate in the deep layer. After seven weeks, the mandibular condyle showed irregular remodeling of bone with negligiable immunoreactivity in the remodeled bone trabeculae. On the other hand, in the control group the MMP-12 immunoreactivites were noticed relatively weak mainly around the Haversian canals. In conclusion, the increased expression of MMP-12 in rabbit mandibular condyle was detected obviously after two weeks rather than after four and seven weeks postoperatively. These results provide evidence for a potential role of MMP-12 in the pathogenesis of osteoarthritis and imply that the inhibition of MMP-12 may be potentially therapeutic for the treatment of degenerative joint diseases