Alterations in articular cartilage of the rabbit mandibular condyle following surgical induction of anterior disc displacement: Light and electron microscopic immunocytochemistry using colloidal gold conjugates

To test the hypothesis that surgical induction of anterior disc displacement (ADD) in rabbit craniomandibular joints will lead to degenerative osteoarthritic changes, ultrastructural features of normal condyles was compared to those of experimental condyles at two weeks following induction of ADD. Also, the quantities of type-VI and -IX collagens, as well as the components of proteoglycans, such as chondroitin-4-sulfate (C4S), chondroitin-6-sulfate (C6S), keratan sulfate (KS) and link protein (LP) were measured using immunogold labeling technique at the light and the electron microscopic levels.; The right joint of each of 20 rabbits was exposed surgically, and the disc was displaced anteriorly to be sutured to the zygomatic arch. The left joint served as a sham-operated control. Ten additional joints were used as non-operated controls. Anesthetized rabbits were perfused with 2% buffered formalin. Mandibular condyles were excised, decalcified in EDTA, and processed for light and electron microscopy. Sections were incubated in monoclonal antibodies against C4S, C6S, KS and LP, and in polyclonal antibodies against type-VI and -IX collagens, followed by an incubation in appropriate colloidal gold conjugates. Immunostaining for proliferating cell nuclear antigen (PCNA) was performed, and PCNA indices were determined.; Pathological observations included cartilage neovascularization, chondrocyte clustering, vacuolation, loss of extracellular matrix next to the chondrocytes, and increased numbers of apoptotic chondrocytes and PCNA-positive cells. Injured chondrocytes showed increased amounts of RER and Golgi.; The results of the immunocytochemistry showed statistically significant depletion of C4S, C6S, KS, LP, type-VI collagen and type-IX collagen in the osteoarthritic cartilage (P {dollar}<{dollar} 0.05). The reduction of binding molecules such as LP, type-VI and type-IX collagens suggest a possible mechanism for the observed loss of integrity of the extracellular matrix.; It is concluded that surgical induction of ADD in the rabbit CMJ leads to molecular, cellular and extracellular alterations in articular cartilage of the mandibular condyle similar to those described previously in human ADD and in osteoarthritis of other synovial joints. The results of this study provides evidence that the loss of shock absorber function of the disc and the exposure of condyles to overloading may cause the injured chondrocytes to secrete degradative cytokines.