Spontaneous osteoarthritis in rhesus macaques. I. Chemical and biochemical studies.

We analyzed the articular cartilage of 41 rhesus macaques for elemental concentrations including [Ca] calcium, [P] phosphorus, [Mg] magnesium, [S] sulfur, [K] potassium and glycosaminoglycan (GAG) and collagen content. Our findings revealed an increase in all elements with aging. Within the osteoarthritic (OA) groups, young OA had higher levels of all elements than old OA, and significantly greater levels compared to young normals. In addition, GAG content was dramatically increased in young OA. Old OA did not differ from old normals for any elements although GAG levels decreased. Collagen was shown to be stable with increasing age in both normal and OA cartilage, but decreased in OA cartilage. This macaque model of spontaneous OA is valuable because it demonstrates early OA changes typical of experimental models and late changes similar to human OA.