Ultrastructural Characterization of the Rabbit Mandibular Condyle following Experimental Induction of Anterior Disk Displacement

Abstract

Previous studies in our laboratory have shown that surgical induction of anterior disk displacement (ADD) in the rabbit craniomandibular joint (CMJ) leads to cellular and extracellular alterations consistent with osteoarthritis. Similar findings were also reported in human ADD as well as osteoarthritis of other joints. The purpose of this study was to further characterize these histopathological findings at the ultrastructural level. The right joint of 15 rabbits was exposed surgically and all discal attachments were severed except for the posterior attachment. The disk was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control. Ten additional joints were used as nonoperated controls. Mandibular condyles were excised 2 weeks following surgery and processed for transmission electron microscopy. Experimental condyles showed neovascularization, fibrillation and vacuolation of the extracellular matrix and an increase in the number of apoptotic cells compared to controls. In addition, chondrocytes in osteoarthritic cartilage showed an increase in the amounts of rough endoplasmic reticulum and Golgi complex suggesting an increase in protein synthesis. The presence of thick collagen fibers in osteoarthritic cartilage supports our previous immunohistochemical results of the presence of type I collagen instead of normally existing type II collagen. It was concluded that surgical induction of ADD in the rabbit CMJ leads to ultrastructural changes in the mandibular condylar cartilage consistent with degenerative alterations known to occur in osteoarthritis.

Chondrogenic effect of the perichondrium graft on the internal derangement and osteoarthritis of the temporomandibular joint of the rabbit

“…The study of Sharawy et al involving the rabbit TMJ has supported other studies claiming that anterior disc emplacement causes intracellular and extracellular changes of osteoarthritis (Sharawy et al, 2000). In this study they have split all the connections of the disc but the posterior ones and investigated the condyles with electron microscopy after 2 weeks.…”

Factors affecting degeneration in human temporomandibular joints as assessed histologically

“…Potential adverse effects of abnormal, mostly anterior disc position undoubtedly have attracted the greatest interest of researchers. Recent evidence from experiments in rabbits (34)(35)(36) indicated that surgically induced disc displacement entails alterations of TMJ tissues, which are similar to those observed in osteoarthrosis. This has neither been confirmed by another study in animals (37), nor is it supported by the present findings suggesting that abnormal disc position plays a statistically significant role only, when it is accompanied by loss of molar support.…”

Expression of endoplasmic reticulum stress protein in rabbit condyle cartilage following anterior disk displacement

“…According to the previous studies in chondrocytes of rabbit mandibular condyles, apoptosis has been observed in the upper layer of ADD cartilage after surgery. 4,14 Wu et al 15 demonstrated that the production of pro-apoptotic proteins, bax, Fas, and caspase-8 increased in the chondrocytes following ADD. However, the underlying mechanisms are poorly understood.…”