Meeting Abstract

P3.162  Monday, Jan. 6 15:30  The effects of weight-bearing exercise on skeletal structure and strength differ between outbred populations of mice WALLACE, I.J.*; JUDEX, S.; DEMES, B.; Anthropology, Stony Brook Univ.; Bioengineering, Stony Brook Univ.; Anatomy, Stony Brook Univ. ian.wallace@stonybrook.edu

The effects of weight-bearing exercise on skeletal structure and strength are frequently observed to vary from one individual to the next. Here, we examine whether such variation also exists at the population level. An experimental approach was adopted involving mice from two commercial outbred stocks that have been reproductively isolated for >100 generations (Hsd:ICR, Crl:CD1). Beginning shortly after weaning, females from each stock were either treated with a treadmill-running regimen for 1 month or served as sedentary controls (n=20/stock/activity group). Home-cage activity of all animals was monitored during the experiment. Limb forces were recorded to verify that they were similar in the two stocks. At the end of the experiment, μCT was used to quantify cortical and trabecular bone structure in the femoral mid-diaphysis and distal metaphysis, respectively, and mechanical testing was used to determine femoral diaphyseal strength. Among the Hsd:ICR mice, treadmill running led to significant improvements in diaphyseal bone quantity, structural geometry, and mechanical strength, as well as enhanced trabecular bone morphology. In contrast, among the Crl:CD1 mice, the same running regimen had a negative effect on femoral cortical and trabecular structure, and led to significant reductions in femoral diaphyseal strength. Importantly, in neither stock was body mass, muscle mass, or cage activity level significantly different between runners and sedentary controls. Given that most environmental variables were controlled in this study, we suggest that the differential effects of exercise on the limb bones of Hsd:ICR and Crl:CD1 mice were due to genetic differences between the stocks.