Bone mineral density, osteopenia, and osteoporosis in the rhesus macaques of Cayo Santiago.

This cross-sectional study investigates metabolic bone disease and the relationship between age and bone mineral density (BMD) in males and females of a large, well-documented skeletal population of free-ranging rhesus monkeys (Macaca mulatta), from the Caribbean Primate Research Center Museum collection from Cayo Santiago, Puerto Rico. The sample consists of 254 individuals aged 1.0-20+ years. The data consist of measurements of bone mineral content and bone mineral density, obtained from dual-energy X-ray absorptiometry (DEXA), of the last lumbar vertebra from each monkey. The pattern of BMD differs between male and female rhesus macaques. Females exhibit an initial increase in BMD with age, with peak bone density occurring around age 9.5 years, and remaining constant until 17.2 years, after which there is a steady decline in BMD. Males acquire bone mass at a faster rate, and attain a higher peak BMD at an earlier age than do females, at around 7 years of age, and BMD remains relatively constant between ages 7-18.5 years. After age 7 there is no apparent effect of age on BMD in the males of this sample; males older than 18.5 years were excluded due to the presence of vertebral osteophytosis, which interferes with DEXA. The combined frequency of osteopenia and osteoporosis in this population is 12.4%. BMD values of monkeys with vertebral wedge fractures are generally higher than those of virtually all of the nonfractured osteopenic/osteoporotic individuals, thus supporting the view that BMD as measured by DEXA is a useful but imperfect predictor of fracture risk, and that low BMD may not always precede fractures in vertebral bones. Other factors such as bone quality (i.e., trabecular connectivity) should also be considered. The skeletal integrity of a vertebra may be compromised by the loss of key trabeculae, resulting in structural failure, but the spine may still show a BMD value within normal limits, or within the range of osteopenia.

Bone mineral and osteoporosis in aging rhesus monkeys.

55 femora of free ranging rhesus monkeys from the Caribbean Primate Research Center ranging in age from 2-25 years were analyzed using histology, density fractionation and chemical analysis and correlated with morphometric data. The vertebral density was determined by photon absorptiometry. 119 caudal vertebrae from the skeletal collection were analyzed chemically. Cortical mineral density and porosity increased with age, and vertebral density and cortical area increased with weight. There was significant sexual dimorphism in many histological variables reflecting size differences and cortical porosity was greater in males. The chemical analysis showed no influence of the diet on bone mineral but that Ca increase with age in females but not in males. Finally a subgroup of aged, animals had hypermineralized, and more porous bone. This subpopulation may prove to be a valuable model for senile osteoporosis.

Rhesus macaques as an experimental model for degenerative arthritis.

To understand the pathogenesis of degenerative arthritis, an experimental model of the disease in which systemic factors can be investigated is required. This study reviews the evidence that the spontaneous degenerative arthritis in free ranging rhesus macaques at the Caribbean Primate Research Center meets the criteria for such a model. Two forms of degenerative arthritis in rhesus macaques have been identified: osteoarthritis and calcium pyrophosphate dihydrate crystal deposition disease. These diseases resemble spontaneous human arthritis with respect to age, sex, joint histology and cartilage composition. The availability of large numbers of affected primates as well as the availability of age/sex matched controls free of disease are additional factors that make spontaneous degenerative arthritis in rhesus macaques a suitable experimental model for the study of the human disease.