INVESTIGADORES
COINTRY Gustavo Roberto
congresos y reuniones científicas
Título:
Tomographic and biomechanical analysis of muscle-bone interactions in mice artificially selected for body conformation
Autor/es:
GUSTAVO ROBERTO COINTRY; RICARDO DI MASSO; RICARDO FRANCISCO CAPOZZA; JOSÉ LUIS FERRETTI; MARÍA TERESA FONT
Lugar:
Río de Janeiro (Brasil)
Reunión:
Congreso; IOF World Congress on Osteoporosis; 2004
Institución organizadora:
International Osteoporosis Foundation
Resumen:
   Antagonistic artificial selection of adult male and female mice with wide variation in body conformation produced animals with light body / long skeleton (CBi/L) or heavy body / short skeleton (CBi/C) from a parental line CBi. On changing the natural proportions between body and skeletal size / shape, this procedure allowed analyzing correlations between the body and gastrocnemius weight and indicators of material, geometric and structural (mechanical) properties of cortical bone of the femur diaphyses (as assessed by pQCT and bending tests at a low strain rate) avoiding the natural, allometric associations which normally blunt the biomechanical interrelationships between muscles and bones.    As expected, the selection procedure altered the natural proportions between gastrocnemius mass, body weight and femur length, and between femur length and diaphyseal cross-sectional properties (moment of inertia, CSMI). The CSMI correlated closer with gastrocnemius weight than it did with body weight. Diaphyseal strength correlated significantly with CSMI, gastrocnemius weight and body weight. Correlation of CSMI with gastrocnemius weight was closer than with body weight and was the only graph describing the studied association as a single (linear) function for all the 3 strains studied as a whole.    Results suggest that 1. muscle mass would not depend alometrically on body weight in any circumstance; 2. the geometric proportions between long-bone length and cross-sectional properties would not be independent determinants of bone structure or strength; 3. muscle development would not depend on bone development; 4. the diaphyseal design would be adapted to muscle ability to directionally deform the skeleton rather than to the weight of the supported biomass, and 5. the biomechanical adaptation of bone strength to customary mechanical usage as allowed by the biochemical and microstructural constitution of the skeleton would be determined more closely by the dynamic influence of muscle contractions than by the static, gravitational load of the body weight. Those relationships, difficult to assess in natural conditions, are crucial for interpreting the biomechanical homeostasis of the skeletal structure and the etiopathogenesis of all osteopenias and osteoporoses. This knowledge could be extrapolatable to the pathogenetic analysis of many human bone-weakening diseases.