Abstract
We explored age- and strain-related differences in bone microstructure and body composition in male C57BL/6J, DBA/2JRj and C3H/J mice. Bone microstructure of the femur, tibia and L4 was assessed by μCT at the age of 8, 16 and 24 weeks. The weight of several muscles and fat depots were measured at the same time points. At all timepoints, C3H/J mice had the thickest cortices followed by DBA/2JRj and C57BL/6J mice. Nevertheless, C57BL/6J mice had higher Tb.BV/TV and Tb.N, and lower Tb.Sp than DBA/2JRj and C3H/J mice at least at 24 weeks of age. Skeletal development patterns differed among strains. C57BL/6J and DBA/2JRj mice, but not C3H/J mice, experienced significant increases in the sum of the masses of 6 individual muscles by 24 weeks of age. In C57BL/6J and DBA/2JRj mice, the mass of selected fat depots reached highest values at 24 weeks, whist, in C3H/J mice, the highest values of fat depots masses were achieved at 16 weeks. Early strain differences in muscle and fat masses were largely diminished by 24 weeks of age. C3H/J and C57BL/6J mice displayed the most favorable cortical and trabecular bone parameters, respectively. Strain differences in body composition were less overt than strain specificity in bone microstructure, however, they possibly influenced aspects of skeletal development.
Highlights
Childhood and adolescence are critical periods for the accrual of peak bone mass and structure, defined as the maximal values of skeletal traits present at the end of skeletal maturation [1,2,3]
Cortical structure was determined at the midshaft of the femur and the tibia over a length of 5% proximal and 5% distal from the middle of the bone
We showed that the highest muscle mass and cortical bone properties occurred at 24 weeks of age in C3H/J and DBA/2JRj mice, whereas more variable cortical skeletal development patterns were seen in C3H/J mice
Summary
Childhood and adolescence are critical periods for the accrual of peak bone mass and structure, defined as the maximal values of skeletal traits present at the end of skeletal maturation [1,2,3]. Twin and family studies suggest that 60–80% of peak bone mass variability is attributable to genetic factors, whilst up to 40% of the remaining variability can be influenced by modifiable factors such as lifestyle and body composition [1, 3]. The relationship between body composition (muscle and fat mass) and bone during growth in humans has gained considerable interest [1, 4]. Several pediatric studies suggest that muscle mass and bone mass are closely linked during development [4,5,6,7]. Studies on the relationship between fat and bone parameters in children, adolescents and young adults have revealed positive, negative or no associations [4, 11, 12]; these discrepancies may reflect methodological differences and/or perplexing bone–fat interactions. Pediatric studies in this area are challenged by uncontrolled genetic and environmental heterogeneity, undesirable radiation exposure during longitudinal bone assessments and bone measurements restricted to certain anatomical sites (e.g., assessment of the distal radius and tibia using high-resolution peripheral quantitative computed tomography or HR-pQCT) [13]
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