Changes in Bone Structure and Strength during Aging in Male and Female BALB/c Mice

Introduction: With aging, there are well-documented changes in the structure and strength of the human skeleton. Periosteal and endocortical expansion of the diaphyses lead to increased moments of inertia, a positive geometric change that is offset partly by decreased cortical bone material strength. Trabecular bone density decreases with aging leading to loss of bone strength at sites rich in trabecular bone. Mice are often used for studies of skeletal aging, yet there are few data on changes in bone structure and strength during normal aging. Several studies document the accrual of size and strength during mouse development, and indicate that the period of rapid growth ends by 4-5 months [1,2]. There are fewer data on quantitative changes that occur after this age, although two studies have described changes across the lifespan of C57Bl/6 mice [3,4]. In order to further assess the clinical relevance of using aged mice for studies of age-related osteoporosis, we quantified cortical and trabecular bone structural and mechanical properties of female and male BALB/c mice from 2 to 20 months age.