Premium
Comparison of Morphology and Bending Mechanics of Femora in Response to Chronic Exercise in Three Strains of Mice
Author(s) -
Middleton Kevin M,
Peacock Sarah J,
Coats Brittney R,
Kirkland J Kyle,
Garland Theodore
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.368.2
Subject(s) - strain (injury) , bending , biomechanics , medicine , geometry , materials science , orthodontics , anatomy , mathematics , composite material
Analyses of bone cross‐sectional geometry are frequently used to predict the loading histories of past populations. We investigated the interplay between genetic background and exercise, as well as the relationship between bone cross‐sectional geometry and bending mechanics, in three mouse strains: high bone density (C3H/He), low bone density (C57BL/6), and a high‐runner strain homozygous for the Myh4 Minimsc allele (MM). Each strain was divided into exercise (wheel) or control (no wheel) treatment groups. After seven weeks, morphometric and mechanical loading analyses were conducted on dissected femora. Comparisons of exercise versus control treatments revealed no significant differences within any strain, although exercising MM mice ran significantly more than their C3H/He and C57BL/6 counterparts (P < 0.001). Thus, predictions that exercise would alter bone phenotype were not supported in this sample. Results of cross‐sectional geometry predicted that MM femora would be most resistant to bending forces and C3H/He femora least resistant. Mechanical tests, however, showed that C3H/He mice had significantly stiffer bones than both MM (P < 0.001) and C57BL/6 (P < 0.001) mice. Thus, predictions of low bending strength in C3H/He femora, made without factoring in their high mineral content, were not supported. Overall, we did not find the expected associations between exercise, cross‐sectional geometry, and mechanical properties. Accordingly, our results suggest that predicting loading response from cross‐sectional geometry alone only partially informs such hypotheses. Our study questions common paleoanthropological conventions in which bone mineral composition is assumed to be constant, and differences in cross‐sectional geometry are interpreted as indicative of differential loading regimes. Support or Funding Information This project was supported by an EARDA award from National Institutes of Health National Institute of Arthritis and Musculoskeletal Diseases (KMM), the University of Missouri Department of Pathology and Anatomical Sciences (SJP, KMM), the University of Missouri Bond Life Sciences Fellowship program (SJP), the California State University, San Bernardino Department of Biology (BRC, KMM), Associated Students Incorporated of California State University, San Bernardino (BRC), the University of Missouri School of Medicine (JKK), and the National Science Foundation (TG, Jr.; IOB‐0543429).