Measurement Of Bone Mineral Density And Body Composition In Female Cynomolgus Monkeys Based On DXA

PurposeBone mass and body composition of female cynomolgus macaques in various age groups were measured quantitatively using Dual-energy X-ray absorptiometry（DXA）.In this study,we would like to explore the trend mass and peak value age of bone mass in female cynomolgus macaques.Analysis on the effects of body composition on bone mass in various age groups and precision study of DXA measurements in cynomolgus monkeys were investigated as well.Our objective is to provide data reference for the study related to bone mass and body composition using cynomolgus monkeys as disease model.MethodAccording to age,112 included healthy female cynomolgus monkeys were divided into four groups:juvenile group（1～4 years old,n=35）,youth group（5～10 years old,n=25）,middle age group（11～15 years old,n=25）and elderly group（>15 years old,n=27）.The total body bone mass and body composition were obtained by DXA total-body scanning.Spine BMD（L2-L4）measurements were obtained by the region of interests（ROIs）delineating manually.Multi-segments fitting linear regression analysis was used to obtain the age-changing trend of bone mass and body composition.Spearman correlation analysis and multiple linear regression analysis were used to explore the relationship between bone mass and body composition.The precision of DXA measurement in cynomolgus monkeys was executed with reduplicate scans in thirty female subjects.The difference of precision in various lumbar vertebrae combinations was likewise demonstrated.Results1.The peak value of bone mass were obtained at 10 years old.Bone mass was increased rapidly in juvenile period,and then growth rate slowed down in the young age.Total body bone mineral content(BMC_TB)was decreased slightly in the middle age,and kept stable in the old age after decreasing to a certain level.Compared with the peak value,BMC_TB decreased by10.6%in the old age.However,total body BMD(BMD_TB)and spine BMD（BMDs）reached a plateau when getting the peak value and remained stable until old age.2.Lean mass（LM）increased rapidly in the juvenile period and then growth rate slowed down in the young age.When reaching the peak value,LM continued to decrease in middle and old age gradually.Fat mass（FM）remained at a very low level in the juvenile period and increased rapidly in the young age.When attaining the peak value,FM decreased rapidly in middle age,and then maintained a relatively stable level after decreasing to a certain level in the old age.3.Before the age of 10,LM and FM were positively correlated with BMD_TBand BMDs（P<0.05）,and LM contributed more to BMD in female cynomolgus monkeys.After 10 years of age,LM and FM was positively correlated with BMC_TB（P<0.05）with more contribution to BMC_TBfor FM than LM.At age>10,BMD_TB represented positive correlation with FM（P<0.05）not LM.There was no significant fluctuation in BMDs in middle and old age,hence LM and FM did not contribute to BMDs.4.The root-mean-square coefficient of variation（RMS-CV）of BMD_TB and LM in DXA measurements was no more than 0.5%,and the RMS-CV of FM was 2.71%.The precision of different lumbar segments combinations was consistent with international standards,and the L1-L4 vertebra showed the best precision with RMS-CV of 0.70%.ConclusionDXA showed good reproducibility in quantitative measuring the bone mass and body composition of female cynomolgus monkeys.The bone mass and body composition of female cynomolgus monkeys of different ages will provide a good reference for the study of their animal model.It showed different contribution of LM and FM to the bone mass of female cynomolgus monkeys at different ages,which provides some reference value for exploring the influence factors of osteoporosis.