AN IMMUNOHISTOCHEMICAL STUDY OF THE EFFECTS OF SURGICAL INDUCTION OF ANTERIOR DISC DISPLACEMENT IN THE RABBIT CRANIOMANDIBULAR JOINT ON TYPE-I AND TYPE-II COLLAGENS

The right craniomandibular joint (CMJ) was exposed surgically and all the discal attachments severed except for the posterior one. The disc was then repositioned anteriorly and sutured to the zygomatic arch. Th e left joint served as a sham-operated control; IO other joints were u sed as non-operated controls. Deeply anaesthetized rabbits were perfus ed with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbi ts) after the induction of the anterior disc displacement (ADD). The a rticular disc, bilaminar zone, mandibular condyle and articular eminen ce were excised. The condyles and the articular eminences were deminer alized in EDTA. All tissues were then sectioned at 10 mu m in a cryost at. Sections were incubated with polyclonal antibodies directed agains t type I or type II collagens. Following incubation in the appropriate fluorescein isothiocyanate-labelled secondary antibodies, these speci mens were studied under the fluorescence microscope. At 2 weeks there was a reduction in type II collagen immunostaining; some areas of the experimental condylar cartilage showed a switch from type II to type I collagen. However, at 6 weeks there was an increase in type II collag en immunostaining and a decrease in type I compared to the 2-week grou p. It is concluded that surgical induction of ADD in the rabbit CMJ le ads to alteration in the condylar cartilage collagen phenotype similar to that reported for osteoarthritic cartilage of other synovial joint s.