Measurement and Analysis of Bone Mineral Content and Bone Mineral Density in Healthy Cynomolgus Monkeys at Different Ages

ObjectiveTo study the skeletal characteristics of cynomolgus monkeys at different ages, and to provide reference values for skeletal research using cynomolgus monkeys as model animals.MethodsA total of 283 cynomolgus monkeys aged 1-19 years were selected and divided into 8 groups according to sex and age :1 year≤age<3 years , 3 years≤age<5 years , 5 years≤age<7 years, 7 years≤age<9 years, 9 years≤age<11 years, 11 years≤age<13 years , 13 years≤age<15 years, and age≥15 years groups. Bone mineral density (BMD) and bone mineral content (BMC) were measured using dual-energy X-ray absorptiometry (DEXA).ResultsBMD increased from 0.32 g/m2 to 0.57 g/m2 and BMC increased from 67 g to 399 g in male cynomolgus monkeys between the age of 1 and 12. While BMC and BMD were relatively stable in the 12~15 years group. BMC and BMD remained at (367.51±7.17) g and (0.56±0.06) g/m2, respectively, in the ≥15 year-old group. In female cynomolgus monkeys, BMC increased from 58 g to 233 g and BMD increased from 0.31 g/m2 to 0.47 g/m2 between the age of 1 and 10. The maximum BMC was only about 58% of that of male cynomolgus monkeys, the maximum BMD was about 80% of that of male cynomolgus monkeys, and BMC decreased significantly after the age of 10 years. BMC remained at (166.63±6.21) g and BMD remained at (0.46±0.04) g/m2 after the age of 15 years, which were 45% and 80%, respectively, of those of male cynomolgus monkeys.ConclusionIn male cynomolgus monkeys, as their skeleton develops, BMC and BMD increase continuously until the age of 12 years, and are relatively stable between the age of 12 and 15 years. While in female cynomolgus monkeys, BMC and BMD increase annually until the age of 10 years, but after the age of 10 years, BMC decreases significantly, while BMD remains relatively stable between the age of 10 and 15 years. Peak bone mass of female cynomolgus monkeys is lower than that of male cynomolgus monkeys.