Experimental induction of anterior disk displacement of the rabbit craniomandibular joint: an immuno-electron microscopic study of collagen and proteoglycan occurrence in the condylar cartilage.
BACKGROUND
Results from our previous studies suggest that surgical induction of anterior disk displacement (ADD) in the rabbit craniomandibular joint (CMJ) leads to histopathological alterations consistent with osteoarthritis. In addition, molecular changes in collagens and glycosaminoglycans (GAGs) were observed using immunohistochemistry. The purpose of the present study was to further characterize those molecular changes in collagens and GAGs using immuno-electron microscopy.


METHODS
The right joint of 15 rabbits was exposed surgically and all discal attachments were cut except for the posterior attachment (the bilaminar zone). The disc was then repositioned anteriorly and sutured to the zygomatic arch. The left joint was used as a sham-operated control. Ten additional joints were used as non-operated controls. Mandibular condyles were removed 2 weeks following surgery and processed for light and immuno-electron microscopy using colloidal gold-labeled antibodies against collagen type I, II, VI and IX and against keratan sulfate, chondroitin-4 and -6-sulfate, and link protein.


RESULTS
Light microscopic results showed osteoarthritic changes. Immuno-electron microscopy of osteoarthritic cartilage demonstrated a decline in type II collagen, the abnormal presence of type I collagen and loss of type VI and IX collagens. Quantitative colloidal gold immuno-electron microscopy confirmed the depletion of keratan sulfate, chondroitin-4 and -6-sulfate, and link protein in osteoarthritic cartilage.


CONCLUSIONS
Anterior disk displacement leads to molecular alterations in both the collagen and the proteoglycans of rabbit condylar cartilage characteristic of osteoarthritis in other synovial joints. These alterations are consistent with loss of the shock absorber function of the cartilage and injury of the underlying bone.
Sharawy
Mohamed
M
Department of Oral Biology and Maxillofacial Pathology, School of Dentistry, Medical College of Georgia, Augusta, GA 30912-1122, USA. msharawy@mail.mcg.edu
Ali
Ayman M
AM
Choi
Won-Seok
WS
D000818:Animals; D000906:Antibodies; D002356:Cartilage / Q000473:pathology*; D002809:Chondroitin Sulfates / Q000648:ultrastructure; D003094:Collagen / Q000648:ultrastructure*; D024042:Collagen Type I / Q000648:ultrastructure; D024043:Collagen Type II / Q000648:ultrastructure; D024081:Collagen Type IX / Q000648:ultrastructure; D024142:Collagen Type VI / Q000648:ultrastructure; D016326:Extracellular Matrix Proteins / Q000648:ultrastructure; D017979:Gold Colloid; D007150:Immunohistochemistry; D004204:Joint Dislocations / Q000209:etiology / Q000473:pathology*; D007632:Keratan Sulfate / Q000648:ultrastructure; D008297:Male; D008335:Mandibular Condyle / Q000473:pathology*; D016253:Microscopy, Immunoelectron; D010003:Osteoarthritis / Q000473:pathology; D011506:Proteins / Q000648:ultrastructure; D011509:Proteoglycans / Q000648:ultrastructure*; D011817:Rabbits; D019224:Temporomandibular Joint Disc / Q000473:pathology*; D013705:Temporomandibular Joint Disorders / Q000473:pathology; D000099249:Proteoglycan Link Protein
D000906:Antibodies; D002809:Chondroitin Sulfates; D003094:Collagen; D024042:Collagen Type I; D024043:Collagen Type II; D024081:Collagen Type IX; D024142:Collagen Type VI; D016326:Extracellular Matrix Proteins; D017979:Gold Colloid; D007632:Keratan Sulfate; D011506:Proteins; D011509:Proteoglycans; D000099249:Proteoglycan Link Protein