Human and experimental osteoarthrosis of the temporomandibular joint. Morphological and biochemical studies.

Osteoarthrosis is a common disease of the temporomandibular joint. The frequency and sites of location were studied in autopsies and they were classified according to age, sex and state of dentition. There was no differences related to sex, but the osteoarthrotic lesions were more severe and frequent in joints of specimens from subjects of high age without teeth of their own. The single most affected joint component was the disk which may be due to a limited regenerative ability of this joint component. The glycosaminoglycans of the extracellular matrix of human, osteoarthrotic disks were examined by high-performance liquid chromatography and compared to normal controls. The total glycosaminoglycan content of the arthrotic disks was lower whereas the proportions of iduronic acid and 4-sulfated galactosaminoglycans were higher. The development of osteoarthrosis-like lesions in the temporomandibular joint of rabbits was studied. Sixteen weeks after the surgical disk perforation, osteoarthrosis-like lesions in both the condylar cartilage and the remaining disk tissue were seen with light microscopy. These lesions were also accompanied by changes in the components of the extracellular matrix. Unlike human arthrotic disks, these tissues showed an elevated content of glycosaminoglycans, evidenced by also an increase in proteoglycans. This increase was mostly confined to large proteoglycans in the disk, while a larger proportion of small proteoglycans than in the respective control tissue was found in the adjacent condylar cartilage. Virtually no aggregability was found in normal or degenerated disk tissue. About 50% of the monomers in the normal condylar cartilage were capable of forming aggregates, while this aggregating proportion decreased slightly in the degenerated tissue. The metabolic mechanism underlying these changes in the proteoglycan content was studied using 35SO4 labeling. In the experimental disk tissue, the population of large proteoglycans had a slightly increased rate of synthesis and a slightly slower degradation rate than in the normal disks whereas the small proteoglycans had higher anabolic and catabolic rates than the controls. However, the amount of newly-synthesized small proteoglycans were unable to compensate for the simultaneous degradation. As a result the proportion of large proteoglycans increased. In the experimental condylar cartilage, all proteoglycans showed similarly increased rates of synthesis. However, here the degradation rate of the two large proteoglycan fractions greatly exceeded that of the synthesis. This resulted in a lowered proportion of these monomers in the experimental tissue, as compared to the control.(ABSTRACT TRUNCATED AT 400 WORDS)