Bone mass in female cynomolgus macaques: a cross-sectional and longitudinal study by age

A cross-sectional study by age was designed to evaluate and describe the bone mineral content (BMC, g) and density (BMD, g/cm2) in a population of female cynomolgus macaques (Macaca fascicularis). Dual-energy X-ray absorptiometry was used to measure, in segments L2-L4 of the lumbar spine, the BMC (BMCs), BMD (BMDs), length, and total-body BMC(BMCTB) in 171 female monkeys ranging in age between 3.7 and 22.0 years. The animals were divided into three age groups: (1) young (< 6.5 years, n = 51); (2) adult (> 6.5 years and < 10.5 years, n = 63); and (3) mature (> 10.5 years, n = 57). Young animals had a significantly lower (P < 0.05) body weight and shorter trunk length than adult or mature animals. Young animals also had significantly less (P < 0.05) BMCS, BMDS, and BMCTB than adult or mature animals, and had significantly shorter (P < 0.01) lumbar spine vertebral segments than the other two groups. Longitudinally, 63 animals had repeated lumbar spine scans to examine changes over time. Young animals showed a positive and significant change (P < 0.05) in BMCs and BMDs through time, whereas these parameters did not change in adult animals, and mature animals had a trend towards bone loss through time. Densitometric results suggested that peak bone mass in the lumbar spine was achieved by 9 years of age. Radiographic and dental criteria were developed to identify animals that had reached peak bone mass, and the combined radiographic and dental scoring system reliably identified animals 9 years and older. Female cynomolgus macaques 9 years old or older are recommended for investigations of bone remodeling and associated conditions, such as osteoporosis.